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| I combinations of the above __ INIS Clearinghouse I I other IAEA P. 0. Box 100 A-1400, Vienna, Austria INIS-mf--11305
Ninth National Conference
of the South African Section of the PRI
22nd & 23rd October 1987 Indaba Conference Centre, Witkoppen Johannesburg INDEX Cl From the Sudan to Angola, a review of the Rubber Industry in the other Africa. H Werhoning Polysar.
C? The added value of Total Quality Control. 1. Applehy OuPont..
C3 Oxidative ageing of SBR vulcanisat.es. H Roebuck Monsanto. C4 Recycling of domestic and Industrial plastic was H Breiting Pretoria Technicon. Cb Urethane Prepolymer Hybrids. B Becker National Urethane Ind. C6 Raytec Reactive Elastomer. H Kletman Bayer. (77 Urethanes in motor vehicles, a suppliers view. C Groom Industrial Urethanes. C8 MDI based Urethane foams in motor vehicles, an end users view. D Taylor Nissan Motor Company.
C9 Applications for cast Urethanes in mining. E Hagen Uniroyal. CIO N<-I.wnrk wll.li filler l.o ralihi-r ImndM anil Mil |itiyiil<-ul properlICH. S Wolff Degussa. Cll Karbochems carbon/rubber masterbatching project. A Mclver Karbochem.
Cl? The study of the evolution of rubber extruders from 18R0. M Iddon Iddon Bros.
C1.1 Coated ultrafine precipitated Calcium Carbonate,a filler or an effect additive? D Cornwall ICI. C14 Reinforcement of elastomers and thermoplastics uning Kevlar short fibres. T Donkln DuPont.
CIS Problems associated with rubbers and plastics in mining cables. T Page Rand Mines Ltd.
C16 Conducting PVC compounds for explosive handling areas and High Tech environments. L Bloom PVC Compounders.
C17 Optical Fibres In Telecommunlcat ;. J Franco temens. C1B Radiation effects on Polymers and Elastomers. D Badenhorst Atomic Energy Corp. Retreading Seminar. C19 Radiation crosslinked Polymers in the Building Industry. Keynote address. T A DuPlessis Iso-Ster. EJ Wagne r American Retreadors Ass. C20 The wear resistance of Polymers. R? The history and advantages of Quality Control and third Prof A Ball Univ. of Cape Town. party certification in retreadinR. J J Keuler S.A.B.S. Tear studies in Rubbers. Prof W McGill Univ. of Port Elizabeth The retreading of Radial Steel truck tyres. J Recht Goodyear Tyre Centre. Thermal analysis of Rubber, a challenge to conventional techniques. Todays state of the art in repairing metallic radial 0 Vorster Inst. of Polymer Tech. tyres. D Litterini Technical Rubber Co. C23 New rating techniques for processing aids. A Haverland DOG. (Hamburg). The retreading of Aircraft tyres, a very specialised aspect of retreading. C24 Pressure sensitive adhesives, a review of recent trends. C Andrews BTR Dunlop South Africa. A J Knott General Adhesives. 1)6 Tyre-tread compounding. C25 Silicone flame retardent foams. 0 Ortlepp Karbochem. J DuPlessis G.E.Silicones. The design of Steel-Radial truck tyres and the constraints C26 The relative Influence of silica and elastomer content that this places on the retreading process. on compound properties. J Barnard Firestone South Africa. .1 Tultz P.P.G. Ind. The need for correct rim fitment of pneumatic tyres. C27 Stabilisers for polymers. RSW Idris General tyre and rubber Co. P Grasiozi Ciba Geigy. Hydrogenatcri nltrlle rubber Tor improved durability of motor parts. R Reuffer Bayer.
C29 Flexible containers for storage and transport of liquids. J Dorse BTR Dunlop. New concept for rubber linning in corrosion and abrasion protection. H W Renther Empro. C31 Uses of rubber liners in the mining industry. D Farnsworth Skega. Uses of polymers in the mining industry. B Hutchinson M.I.H. C 1.1
FROM THE SUDAN TO ANGOLA,
A REVIEW OF THE RUBBER INDUSTRY
IN THE OTHE R AFRICA
1. INTRODUCTION
From Che Sudan to Angola, from Mauritania to Madagascar, there are at least 41 nations (excl. South Africa and the North African nations), seven semi- to-full y permanent wars, at 1 Past ono rrvolut ion or coup d 'e'tat pvery year and at least 450 Mio humans of every possible colour, creed and race.
We have rvory itnn^iiwih 11* prob h«in It comes as a pleasant surprise to find in thia continent a rubber consuming industry, more or less alive, but certainly nod kicking very much. This industry manages to consume in a year 40,000 tons rubber, 20,000 tons carbon black and about I,500 tons rubber chemicals, I invite you to have * look around the African Rubber Market. C 1.2 C 1.3 OIL RESISTANT RUBBER These 16 plants would indeed have enough capacity to produce enough tyros THE INDUSTRIALISATION METER to cover all of Africa's requirements would it not be for it series of shortcomings : The annual consumption of NBR rubber by a nation gives a very precise * No hard currency available to update and maintain equipment reading of the industrialization of that nation. properly. * Virtual impossibiiity ro expnrf exross rapacity f rmn nno r"unrry In / tllfl (t'Kl ••[.! I.V mil.u-,-1 I lll>. In fact only 3 nations in Black Africa use nitrile rubbers at all : * Frequent shutdown due to lack of raw materials (this will he Zimbabwe, Kenya and Zambia. The total of barely 60 tons gives you a very discussed at a later stage). clear idea where Black Africa ranks ! * No capital available to upgrade production from cross ply to radial, from tube to tubeless tyres, or even to maintain existing Israel will consume 10 times more than all of Black Africa, and a giant equipment decently. like the USA consumes 5B.OO0 tons per year. In my view the greater part of these 16 plant" is slowly but steadily being But lets look now at the big consumers of rubber in Black Africa : the tyre run down by the effect of these circumstances. Consequently these plants become a burden to the local economies • The eyres and tubes they produce plants. are costlier than the imported onen, are often sold in the local mnrVer below cost (for instance Ethiopia) and have a poor quality image with their local customers. Often quite deservedly ! 16 LITTLE TYRE PLANTS WENT MAKING TYRES IN AFRICA. THEY GOT IN TROUBLE FROM THE START. BUT ARE STILL MOSTLY THERE But tyre plants are «e**n by African government s as mani festat ions of the ever ongoing industrialization of their societies, second in importance nnly tn the breweries. They provide jobs for the workers and pos it i ons for With a car population of maximum 1 mio units. Black Africa has nevertheless one's friends. They are often the only sign of classical industrial 16 tyre plants to make tyres and tubes for these cars. production, are pictured on the local currency (Tanzania 10 Rh note) mid are frequently included on tours given tn visiting heads of state. It's a caftfi of too many plants, producing not enough. How many tyret do these 16 plants produce ? - I cannot give you a precise figure, but my What will be the future ? - Like most of Africa, these plants won't Hose guest is that the whole of Black Africa produce* 1*2 nio tyras par year, down, they will struggle through, hoping for the day when mstters improve 70 X passenger and 30 % truck tyres. This satisfies about 35 X of the local and when with the help of massive dosen of cash from rirh friends, they are need* The rest has to be imported. regenerated! updated, Modernised, expanded and brought up-to-date. Bad roads, poor service and incompetence reduce tyra life considerably. C JL.4 C 1.5 In fact many such studies are written, discussed, re-written, updated and This is a plant which could do much better, considering the intelligence printed. Teams of experts fro* the United Nations and the Organisation of And education of its staff. But initiative is stifled by political African Unity and other institutions make a good living out of doing just bureaucracy, the plant is at full work perhaps 6 hours for 5 days a week, that. and even this is often reduced by political assemblies or rallies. The plants in Uganda, Upper Volts, Angola and no doubt many others have The heavy bulky old-fashioned curing bladders they make locally from NR been given auch treatment. last about 60-100 cures only, and a whole mountain of goners lies piled up behind tbf> plant. various parent organisations which built them in the first place and which DIP last t imp 1 was tht*re I suggeMfri th**y en I them up into itnnda Id, but in many cases still retain a financial share. But in most cases local any change requires an approval, and whoever signs an approval taken full financial participation in excess of 50 % is a must. Very few of those responsibility if there is a problem. Thpr*»fore nobody signs and matters plants are profitable, but the Goodyear, Firestone and Dunlop's can at stagnate. Thus they struggle on. The system prevents initiative and changes least cover their expenses through management contracts. at middle and lower management level. Further up you will find political appointees, and these characters have other things to worry about. Some plants are entirely locally run, and struggle as best as they can to keep production going. Sometime* they are out of action for a year or two, Recently Rapra of United Kingdom has done a detailed study to upgrade that and have quite a struggle to get restarted. Ghana, Bourquina Paso, Uganda plant. But you don't need to change the plant you need to change the system and Senegal are such examples of production by systems dimly remembered and to succeed. handed down from one short lived generation to the next. There we can see them now struggling along cheerfully, our comrades of the black industry producing off and on, even if they don't quite know what THE EMPIRE WAS HERE they do. But they manage, in difficult circumstances, doubly black and singularly unique. The eastern half of Africa had been developed nicely by their respective Ethiopia is an example of another type* A tyre plant bought in the early colonial powers. Kenya, Tanzania, Zambia, Zimbabwe, and to a lessor degree '70 for 12 mio dollars from CSSR, with Japanese technology and run within Mozambique, entered into independence with « simple bur efficient light the system of the scientific permanent Marxist-Leninist Revolution. industry able to produce most of the basic local demands for consumer goods. The bulk of the technical staff is trained in Russia or Eastern Europe. Some of the tyres presses to recently bought were made in Cechoslovakia in 1936 and 1937, but at least were given a fresh coat of paint before being shipped to Addis Ababa. C 1.7 - 6 - THE EXCEPTION WHICH CONFIRMS THE RULE UV8 LBS IMfORTATIOH OR WEST AFRICA MOSTLY A LA rXAMCAISE In the case of Kenya, the finest example of African development, we count 20 different companies) consuming a total fo 10,000 tons rubber a year and that number is increasing. In francophone West-Africa, the French connection in omnipresent. A French fighter squadron in Senegal, a company of paras here or therft, French We find alt che classical usages of rubber there : airforce transport command present on every sizeable airport, and of course. France's military presence in T.-hsd, And if you are a good I or A I Tyres, tubes head of government snd love France all Che time, they makf* you n member of Retreading the Academe Franchise which in like a British Lord, only with immortality Simple seals thrown in. Oil resistant rubber parts Extrusion (car profiles) Apart from B sma11 tyre plant in Cameroon, we f ind that there in no nrt ivp rubber industry at all, certainly not of the size you find in the eastern You find names like Car and General, Firestone, Bata, Avon, Vaculuc, half of Africa. Associated Batteries, and you find the rest of the producers - middle to 1 small companies - run by Kenya * energetic and entreprising Asian minority. In fact these places (Senegal, Cameroon, Ivory Coast, etc.) are captive exports markets for the French industry, from bottled Vichy water, Normandy Compound recipes have been handed down from father to son. But the sons of butter, Parisian h/un to tyre, tubes, washers snd gaskets. the sons are now being educated at the University of Northern London's Rubber Institute, The last time 1 was in Cameroon I noted that the hotel I stayed in announced proudly in their advertising that 7fl X of the food thry «(>rve is There is lively exchange of technical staff, ideas and investments between imported. Pakistan, India and Kenya, and also, to a lesser extend, to Tanzania. In Znire alt the oranges were Tantania has gone the other way* The General Tyre plant in Arusha remains a going concern, it is managed by Gentire expatriates from the United States. Ghana in in a mess, but let quote : Given the local economic conditions, this is a fine plant. "A Western diplomat describes Hr« ftawlings and Ma colleagues The fat* of the nationalised former Bata plant in Dar-es-Salaam is worte as 'one of the first truly post-independence £"vernments of Africa,1 meaning one of the first of African'* governments than death. to blame its own citizens for the nation's failure, not some bedrnck of colonial or neo-colonial evil." The Bata organisation in Canada has repeatedly been invited by the Toronto St«r, Ql Tamanian Government to tak« it back and tort out the fruit* of many years We could have told then so very long ago. of nationalisation. Bata has declined* c i.a c 1.9 Nigeria, over > 100 mio inhabitants, could potentially be a most proeperous So- *s * r«aul- of "11 your efforts you will hold a lot of local cash which place, but despite the benefit of a Britiah upbringing we uy aay now "Rien wiu not buv y°u "hat you need : ipirf., n«w equipment, new processes, ami ne va plul" - nothing goes anymore. vhich wiU not buy y°u economical security. So there is no justification to isake the effort. At th* end it all comes down to money and economical security which the T H I AfHICAH VICIOUS CIRCLE entrepreneur needi to get going, no matter what his colour is. Kow to break out of this situation ? - You can tell me ! South Africans 29 of the world's poorest 36 countries are in Africa. Every 20 years the n*v< done this with immense sucesa. Without experts from abroad. You could population doubles. Since the early 1970, Africa produces every year 1 % lnow them ! lets food. Sy 1984 food imports reached 2U mio tons. Ethiopia's population, today 45 mio, will reach 231 mio by about 2030, the tame population as today in the USA. The queation here ia if that growth is . II. werhonig stopped by family planning or by aids. *r<>" s">" Manager In Africa 29 trees are cut down for 1 planted. Over the past 25 years half of the African forest hat been destroyed. 80,000 expatriated expertt work in Black Africa on a variety of aid programs, with a budget of 7.5 Bio dollars, on which half it used to pay themselves. Despite 25 yeart of this, Africa has plunged from self sufficiency to widespread hunger. The market is there, immense, growing, ideal for Africa's rubber industry to expand and contribute- But however hard and efficient and profitable a local industry ia, at the end of the yctr its profit, in local currency, will be worth next to nothing, because you are unable to convert it to a hard currency. DOC W64H July 1987 iTHK APIIKI1 VAI.IIK OK TOTAL OliAl. I'I'Y MA N A< i KMI-: NT Oil A I I IV MANAIiKh : I'cil.YMm I'lloliln'TS IlKI'AII riHK N T IIu !'<>•>t l.h. II rtl I UP Nntiun^l i:«mfpi enic •»! I'lnsli. IIIKI llul.I., I I I.K t I > 111.- S.A. .!•.• i- MIII7 C2.2 THE APDED VALUE OF TOTAL QUALITY MANACEMF.NT AT THE HFC.INNINC OF THIS rFWTI'RY, IWWFVFR, IT RFCAMF QUALITY IS A KEY FACTOR IN DETERMINING THF. SUCCESS OF ORVHIt'S THAT THF PFMANP FOB nwiFBCIM FyPl.nSIVFS WAS BOTH PRODUCTS AMD THEIR COMPANIES THROUGH THEIR I.FVFI.I.ING OUT. THF COMPANY THFRFFORF PFI1PFP T" t'SF. COMMTmviMESS ttt THF. MARKET PLACF. THE ADOPTION OF A ITS CHFMICAI. FYPFRT1SF Tn U1PFH TIIF RANCF nF ITS QUALITY APPROACH OFFERS EACH INDUSTRIAL CONCERN THE CHFMICAI. PRnlwllTS AND TO MAKr ITS FIR.-T VFNTt'RF |NTn OPPORTUNITY TO IMPROVE ITS BUSINESS THROUGH REDl'CFD THF. PRODUCTION OF TFXTIIF FIIWFS . COSTS, INCREASED EFFICIENCY AND BETTER CUSTOMER LIAISON. IN IQ?7 THF fnMPANY TOW ANHTOFP PFriSlnH Ullll'll WAS Til SHAPF ITS RPS1NFSS STRATFnv Ff»R THr KPTTT'R PART riF THK I WOULD LIKE TO SHARF WITH YOU TODAY HOW NFXT SO YFARS. IT I'FI I I»P T" STAPT SPFNIUNi; W PONT VIEWS THF. IMPACT OF QUALITY ON ITS WORLDWIDE SK:NII U'ANT FMNPS nn «A TIIFRF FOI.mWFP. NOT OHF nR TU" NFW PSOPITTS HPT A WIIOI.F IT WOULD BF USEFUL TO RFV1F.W THF. 200 YFARS OLD HISTORY mir.r IIF HimiY si'rrF««Fi'i. pRnmn-ts, KAsrp MAIXIY "N OF OUR COMPANY. I ATTRIBUTE ITS LuNGF.VITY TO THE FACT "iYNTHFTIf I'nl.VMFPS. AM"I»: TIIFSF Vf HAl'F NYI.' IPF.UNH SOMI' VI vrARR AFTFR 11 WAP IKTRI'PITFIl TO THr FOR MOST OF THF. l»TH CENTURY THE COMPANY WAS CONTENT TO MARKF.T Pl.AfF. PURSUE ITS BUSINESS AS A PRODUCER OF HIGH QUALITY GUNPOWDER AND EXPLOSIVES. THIS IS HARDLY SURPRISING AS A COMPANY, WF SAW n|* FITITIF AS n«|r "F BRINrlNr. WHEN YOU CONSIDER THE HUGF. DEMAND THERE WAS FOR SUCH THRnl'cn TO COMMFRrlAI.ISATIOH A rnWTINI'"l'S STRl AH OF 1FW PRODUCTS IN THE RAPIDLY DEVELOPING COUNTRIES IN THE WnlllTTS WHICH WOUI.P rnMMANI) PRFHH'H PRITFS IN Tilt LAST CENTURY. THE COMPANY BECAME VERY SUCCESSFUL. MARKET. THAT RT»ATF«Y WORrFO VFRY WFI.I. I'KTII. •BliMT 10 - IS YEARS AW WMFN TWO NFW FAi time RFfiAS Tr ,:T T' RI'SIIFSS SCFNF. FIRST, THF rc-.T nc •• Wt" - i - - 5 - PRODUCTS FROH RESEARCH TO COMMERCIALISATION ESCAUTEH INTERDEPARTMENTAL QUALITY cnMHITTFFS WF«F FSTARI.ISHFD WHICH I.FH IN TURN Tn IIFPARTMFMTAI IH'AI.IIY rRm:RAHHFS IN SIGNIFtCAOTl.Y AND SECOND, COHPFT1T1VE PRESSURE WAS 1NCREASINR. THF. COMBINED EFFECT WAS TO REDUCE HUB INDUSTRIAL AND STAFF SFTTIKf:*. IT W« EARNINGS AND TO EVEN THREATEN O1IR FX1STENCE. WHAT MANAGFMENT HAP TO T" WAS To F«!TARI ISII TIIF FNVIRONHENT, THE CnNCKPTS, AND TMF TFniNHMIRY THAT THE COMPANY RECOGNISED THAT IN ORDER TO SURVIVE IT HAD WOULD CAUSE FMPI.OYFF.S Tn pRnniirF nmimrrs ANH sntvirFS TO RE-EXAM1NF. ITS RELIEFS ABOUT THF. NATURE AND PURPOSE THAT PFRFORM TO THE CUSTOMER'S F.JPFrTATlnNS. IT STARTS «Y tllFWrlFYlNr. Cl>STOHF« «r<|l'lllFHr(tTR. OF IT'S BUSINESS. ONF IMPORTANT PTXIStOM WAS TO SWITCH IT FNI)S WITH A SATISFIFP rilS ITS EMPHASIS FROM PRODUCTS TO CUSTOMPRS. ANOTHFR WAS TO GIVE QUALITY THE SAME KIND OF ATTENTION THAT WF. filVF ANOTHER ARFA OF PERFORHANCF WHFRF WF ARE A RFCOCN1SEO wr ALSO PKI'I»:NISFI> THAT wr NKFI UORID LEADER. I AM HFRF REFERRING TO SAFETY. OF A NFTWORK 'IF Rt'SINFSS TFAMS MUTT TMF CUSTOHFR IS SFPVFD BY THF SHCCFSSFI1. IKTFMITI'<1 "F WANl' MARKFTINf:, RFRFARHI AND nFVFI.OPWNT AND SUPPORT (iR qUALITY IS A FAR MORF COMP1.FX 1SSIIF THAN MOST OF t'S Aljin INCLMPFI" IN THIS KKI.IFF tS TMF Wrrt.lFR WHO RFCOONISF. IT BEGINS WITH A SINGLE PREMISE - CIV1NC BFWM-'S A VITAL LINK IN TIIF CHAIN OF SFRVItF. THE CUSTOMER WHAT HE NEEDS - BUT FXTFNDS TO THF. MANAGEW.KT OF EVERY ACTIVITY IN OUR ORGANISATION. WE vr ALSO nFVELOPED THF REI.IFF THAT ~A riisTn^FP IS TMF HAD TO CREATE NEW STANDARDS IN OUR UNDERSTANDING AND I'PRSON(S) WITHIN OR nuTSIPF IMF rrWANY Ullll I'SKS OUR MANAGEMENT OF QI'ALITY. IT HAO TO hF A BASIC CONDITION PRnntVTS OR SFRVIfFS". FOR OUR GROWTH AND PROFITABILITY. QUALITY LEADERSHIP IN THE MARKET PUCE WOULD LEAD TO COMPETITIVE WF i:AN r.WBINF THFRF TWO IIWHS SO TMM tA'"H VIINITIn' IN ADVANTAGE. THF NFTWORK INCIlRPflRATFS HANY ri'STOHFR/SIIPPLIFR SO HE BEGAN TO TAW. QUALITY AS A TOP-DOWN ISSUE AND KFUTlnNSHIPS. FACH tllSTnMFR HAS A RnmlRFMFNT MAT IS A COMBINATION OF ITEMS WF RFFF» TO AS: STARTED BY ESTABLISHING A QUALITY POLICY. PRlCF/SERVICF/UNIFORMtTY AW VAI.UF IN t'SF. m'Al.tTY IS ACHIF.VFr. WHEN EVERY INDIVIDUAL ANn FVERY GP '"P "IT SHALL tf THE POLICY OF THF. BU POHT COMMNY TO IINDFRSTANDS THFIR OWN THSTOMFR S? > nS AMD '»t H MAINTAIN A POSITION OF QUALITY LEADERSHIP FOR PRODUCTS, FFFECTIVE USE OF THKIR RESOIIRr.FS T" SAT FY 1 SmiCF. AND SYSTEMS WHICH DU PONT OFFERS FOR COMMERCIAL CMSTOMFRS. SAW." C2.6 - fi - C?.7 n ESTABLISH THE PRACTICE OF CONTINUOUS IMPROVEMENT, Vf. RECOGNISED THAT VIEWS ON QUALITY HAVF CHANGED. n THE IMPORTANCE OF PREVENTION fVS DETFCTION) AS THE ROUTE TO EFFECTIVE USE "F INTERNAL RESOURCES, PRESENT AND FUTURE PAST o THE VALUE OF MEASURED PFRFORMANCF AS A KEY TO QUALITY IS ASSOCIATE 1. QUALITY IS ASSOCIATED HOLDING GAINS. WITH PRODUCTS WITH PRODUCTS AND SERVICES THESE tDEAS ARE ENCAPSULATED IN THF. SYSTEM THAT WE CALL "TOTAL QUALITY MANAGEMENT". QUALITY IS EVERYONF'S 2. QUALITY IS THF RESPONSIBILITY RESPONSIBILITY OF SOMF MA.IOR FLEMENTS IN T.Q.M. APPROACH ARE: QUALITY ASSURANCE POLICY ORGANISATION PERSONNEL. COST OF QUALITY AWARENESS TRAINING QUALITY IMPROVEMENT IMPROVING QUALITY RESULTS 1. IMPROVING QUALITY PROGRAMMES IN LOWER COSTS, HIGHER RESULTS IN INCREASED SUPPLIER QUALITY CUSTOMER RE1JVTIONS PRODUCTIVITY. COSTS, LOWER RECOGNITION MEASUREMENT AND REPORTING PRODUCTIVITY. I AM SURF. THAT YOU ARE NOW SEEING THF. VALUE OF THE CUSTOMFR TS BFCOMING MORF 4. CUSTOMER TS MORF COST T.O.M. APPROACH IN A Rt'SINrSR OBr.,\t)tSAT1ON BUT IT MAY VALUE CONSCIOUS THAN COST CONSCIOUS THAN VALUE BE HELPFUL IF 1 CAN RF. MORF. SPFCIFIC. HOW EFFECTIVE IS CONSCIOUS. CONSCIOUS. TIIF MANAGFMENT CT OUR QUALITY? CAN WF MFASURE THF COST OF T.Q.M., THE QUALITY OF OUR MANAGF.MFNT? 5. QUALITY MORE OFTEN THAN QUALITY IS SEEN AS A NOT IS USED AS A CRITICAL INTERNAL AND WE BELIEVE THAT THIS CAN MEASURED IN FINANCIAL TERMS PROMOTIONAL TERM EXTERNAL BUSINESS AND THAT AREAS WHF.RF IMPROVEMENTS CAN RF. MAW CAN BE LACKING SUBSTANCE. STRATEGY. HIGHLIGHTED BY USING THF CONCEPT OF COST OF QUALITY. THIS MANAGEMENT TOOL BREAKS THE TOTAL COST INTO TWO TO THF.SF. VIEWS WE 'JAN ADD. COMPONENTS. THERE IS FIRST THF COST Oi noi iSU.'.R (CODB) o IDFMTIPYtNC THf RESPONSIBILITY FOR THF INDIVIDUAL ro« TMK QUALITY Of HIS/HBR EFFORTS. C2.8 UP. 9 - 7 - - fl - - THAT IS THE IRREDUCIBLE MINIMUM COST IN A PERFECT ONE CAN NOW SEE THAT THE COQ IS HIGHEST IN THE BURDEN SITUATION AND THEN THERE IS A COST OF QUALITY (COQ). (OR SERVICE) SECTION CLOSELY FOLLOWED BY OUR OPERATING THIS IS DEFINED AS:- LABOUR COSTS WHILE RAW MATERIALS OFFFR LITTLE SCOPE FOR o THE COST OF ENSURING THAT A TASK IS PERFORMED IMPROVEMENT. THESE ARE THE TWO AREAS WHERE AT MAYDOWN CORRECTLY THE FIRST TIME AND:- WE MUST CONCENTRATE OUR EFFORTS TO REDUCE OUR COSTS. o THE ADDED COST OF PERFORMING IT AGAIN WHEN IT IS STUDY OF THE COQ IS USED BY MANY TEAMS WHEN THEY NOT. INVESTIGATE REDUCING OUR COSTS - FOR THESE ARE THE THIS SYSTEM SHOWS, THAT IN THE FIRST INSTANCE, THERE COSTS OF MANAGING THE QUALITY OF OUR BUSINESS. CAN BE WASTED EFFORT IN LOOKING FOR COST IMPROVEMENT IN THE CODR SINCE, IT IS MONEY WE MUST SPEND TO R|IN OUR ONE AREA OF THE MANAGEMENT PROCESS WHERE WF HAVE BEEN BUSINESS. THE RATIO OF COO TO TOTAL COSTS IS, HOWEVER, VERY SUCCESSFUL IS IN THF APPLICATION OF STATISTICAL A DIRECT MEASURE OF HOW EFFECTIVELY WE ARE RUNNING O[tR PROCESS CONTROL TECHNIQUES TO OUR OPERATIONS. WHEN ONE BUSINESS. IF THE RATIO IS MUCH ABOVE 4-5% THEN WE APPLIES ANY TYPE OF MONITORING TO A SYSTEM ONE MUST SHOULD BE LOOKING FOR WAYS TO REDUCE IT. MANY SATISFY THF. FOLLOWING CRITERIA: ORGANISATIONS ARE SURPRISED TO FIND THAT THFIR COQ TS o FAST RESPONSF TO REAL PROCFSS CHANGES AS HIGH AS 10-35?. OF TOTAL COSTS l.FAVING HUGF o INSENSITIVITY TO FALSF ALARMS OPPORTUNITIES FOR COST IMPROVEMENT. WE HAVE FOR n NOT SUR.IF.CT TO OVER CONTROL EXAMPLE STUDIED COSTS AT MAYDOWN BREAKING THEM INTO THE o GIVES GUIDANCE IN THF. MAGNITUDE OF THE ADJUSTMENTS CATEGORIES RAW MATFRIALS, MAINTENANCE, POWER, LABOUR, o IDENTIFY PROBLEMS RFFORF NnN-STAHDARD MATFRIA! I". BURDEN. IT SHOWS THAT RAW MATERIALS ARE 1 TIMFS MORE PRODUCED COSTLY THAN ANY OTHER COST ITEM. FACED WITH THAT KIND o EASY TO IMPLEMENT ON A ROUT IN" BASIS OF BREAKDOWN THE MANAGEMENT MIGHT BE TEMPTED TO BFLIFVP THAT OUR EFFORTS SHOULD RE CONCENTRATED ON IMPROVING THE MOST WELL KNOWN OF COURSE IS THF SHF.UHART CHART OUR RAW MATF.RIAl UTILISATION, SINCE IT IS THE BIGGEST FROM WHIG!! HAVE DEVELOPED THE X BAR AND R BAR CHARTS SINGLE COST ITEM. WHEN WE LOOK AT THE COQ COST, WHICH ARE WIDELY USED IN THK AtrTOMOTIVE INDUSTRY. HOWEVER, OF EACH ITEM A VERY DIFFERENT PICTURE EMF.RGFS. SAMPLES ABE TAKEN ON A REGULAR BASIS AND THE RESULTS TO 1 STANDARD DEVIATIONS. IT WILL ALSO RESPOND AS (OR AVERAGE OF RESULTS) GFNERATES A DATA POINT WHIOI IS QUICKLY AS THE SHFWHART To A SUDDFN 1.ARGF niANGF. PLOTTED ON A CHART. AN AIM POINT IS UETFRMINED BY AWAY FROM AN AIM POINT. MARKET REQUIREMENTS OR 7S BASED UPON PAST PERFORMANCE. LIMITS ARK SELECTED AND IF THE PLOTTED POINT FALLS IT DOES GIVF YOU DFTATI.S OF HOW MUCH THF PROPFSS ilUTSIUF TIIFKF. LIMIT-;, CCIIIRI'l'TIVF M'll'IN l>. TAFFN. Till-; HAS MMVH1 AWAY I'RMM AIM SO Vnlr IAN MAKI' A VI HY IS THE CLASSICAL MECHANISM FOR PROCESS CONTROL - ACCURATE ADJUSTMENT TO RETURN TO AIM. TMF. SHFWMART INVENTED IN 19JOS BY A MAN CALLED 'SHEWHART'. IT IS SYSTEM DOES NOT AUTOMATICALLY DO THIS AND YOU HAVK SIMPLE TO USE AND IS BASED ON SOUND STATISTICAL TO EVOLVE A SFT OF RH1.FS WHICH CAN BECOME QUITE PRINCIPLES - LIMITS OF 3 STANDARD DEVIATIONS ARE COMPLICATED. TYPICAL AND IT DOES DETECT REASONABLY PROMPTLY PROCESS SHIFTS OF 2 OR MORE STANI1ARD-DEVT ATIONS. THE CI'SUM SYSTEM CAM BF DFSIIINFD SO THAT ANY N01SK WE USE A DIFFERENT METHOD OF STATISTICAL PROCESS IN THE SYSTEM CAN BE IGNORED. BY "NOIir WF MF.\N CONTROL IN OUR COMPANY- SOME VARIABILITY THAT !<: AIWAYS PRFSFNT F"OM MEASUREMENT VARIABILITY, RAW MATFRIALS OR EQUIPMENT CHRIIH - OR CUMULATIVE SUM IS 40 YR OLD TFCHNOLORY SFNSITIVITY. WITH THE SHFWUART SVSTFM YOU CAN BROUGHT UP-TO-DATE USING COMPUTERS TO Do THE EASILY START REACTING AND CORRFrTIOT: TO THIS «0(<;F ARITHMETIC. WF CAN TAKE THE SAMF DATA, AGAIN SPLECT AN IF YOU TRY TO MAKF IT MORF SFNSITIVF BY RFhUCINC AIM POINT AND CALCULATE THE DIFFERENCE BETWEEN AN THF. 'ACTION LIMITS'. IF YOUR SYSTEM IS REACTING TO OBSERVATION AND THE AIM POINT, ADD TOGETHER THESE NOISE THFN YOU ARF IN A CYCLING OR OVF.R CONTROL!! •-<' DIFFERENCES, AND THEN PLOT THIS CUMULATIVE SUM. WHEN MODE OF OPERATION. ONE SELECTS A LIMIT POSITION AS AN ACTION POINT ONE CAN SEE THAT WF. GET A SIGNAL MUCH FASTER THAN THE SHEWHART CUSUM ELIMINATES THIS OVFR CONTROL on CYri.p.'.: AND SYSTEM. DOES RESULT IN IMPROVED CONTROL WITH A R"-"IMI:TI0N IN STANDARD DEVIATION AND THF RAMTF OT RFSI'I TS. THE CUSUM TECHNIQUE HAS SEVERAL ADVANTAGES OVER THF SHEWHART SYSTEM. FOR SMALL MOVEMENTS FROM AN MM P01K OF • nnl'T 1 STANDARD DEVIATION IT I" TO o IT DOES PROMPTLY DETECT A SMALL SHIFT OF A PROCESS SENSITIVE THAN THF v T S^ AWAY FROM AN AIM POINT - USUALLY I STANDARD DEVIATION - WHEREAS THF. SHF.WHART IS DESIGNED FOR 2 CP.13 - 11 - - 1? - FOR 1 STD. REV. CHANGE YOU NEED 50 DATA POINTS FOR IN SUMMARY WE CAN SEE THAT OUR COMPANY IS ON THE SHEWHART TO DETECT THE CHANGE. FOR CUSUM YOU NF.FD PATHWAY OF A MAJOR CULTURAL CHANfT. QUALITY IS A 10 AND YOU CAN DESIGN THE CUSUM TO EVEN REACT IN S. DEDICATED MANAGEMENT PHILOSOPHY AND IS NOW A WAY OF LIFE THROUGHOUT OUR ORGANISATION. WE HAVE ONE CAN LOOK AT A GRAPHICAL PLOT OF A CIISUM CHART ESTABLISHED:- AND LOOK AT THR SLOPES OF THE PLOT AN!) THUS DETECT o TOP MANAGEMENTS' LEADERSHIP WHEN A CHANGE HAS OCCURRED. KNOWING EXACTLY WHEN A o THE COMMITMENT AND INVOLVEMENT OF ALL EMPLOYEES PROCESS CHANGES GIVES ONE THE OPPORTUNITY FOR n DEVELOPING TEAMWORK INVESTIGATION, ETC. AND THUS MAKE IMPROVEMENTS TO o REDUCING COSTS THE SYSTEM. n IMPROVING PROFITABILITY o DOING THINGS RIGHT THE FIRST TIME AND ABOVE ALL WE ARE USING CUSUM CONTROL THROUGHOUT OUR ELSE MANUFACTURING PROCESSES - FROM PAW MATERIALS, IMPROVING OUR PRODUCT AND SERVICE TO CKSTOMFRS. MEASUREMENT CONTROL, TNTFRNA1. PROCESS CONTROL, TO THAT IS WHY WE BELIEVF THAT A T.q.M. APPROACH TO FINISHED PRODUCT CONTROL. WE BELIEVE THAT CUSUM IS QUALITY WILL ENSURF OUR COMPANY'S FUTURE PROFITABILITY, A SYSTEM THAT GIVES BETTER PRODUCT UNIFORMITY AND A AND GROWTH. MEANS FOR INDIVIDUAL IMPROVEMENTS OF THAT QUALITY. tT IS A POWFRFUL QUALITY TOOL FOR MANAGEMENT TO USE. IT ALSO BRINGS US TO AN ON-AIM CONCEPT OF CONTROL. OPERATION OF A PROCESS WITHIN A RANGE OF LIMITS IS NO LONGER ACCEPTABLE. THERE MUST ALWAYS BE A TARGET OR AIM VALUE AND THE GOAL IS TO REDUCE VARIABILITY AROUND THAT AIM VALUE. WE THUS GET THE OPPORTUNITY TO CORRECT SMALL DEVIATIONS BEFORE A MAJOR CHANGE CAN OCCUR. THE MAJOR CHANGE IF IJNCORRECTED WILL ALWAYS EVENTUALLY PRODUCE NON-STANDARD MATERIAL. ME HAVE FOUND THAT WHENEVER WE REDUCE THE VARIABILITY IN A PROCESS THEN THE COSTS OF THAT PROCESS ARE IMPROVED. isanto MARKETING TECHNICAL SERVICE - RUBBER CHEMICALS LOUVAIN-LA-NEUVE BaGIUM OXIDATIVE AGEING OF SBR VULCANISATES ? f f f nut types of chomicol crosslinl- s rnn he •'vprrtf.-rl in swlpr-ui vnirormntp*; of SRK "mno-di-poly non-sulf idle. Estimation of the pf>ptn tion ol rivf.>\y cleave pcif'Ki/lcn types or" "Oitlinks. For example, deovogn of thp pnlys>rlfiriic nosslinks ton he ohiainrd with propane - ? - thiot, n hexanr* -1 - thinl rlrav'.'S ihn Hiiulfi'ln cinH polyvilfKIK , The oxidotive ageing of conventionally cured of SBR vulcanisatzs leads to and methy{ iodide breaks al( sulfldir croulint--. increases in hardness and modulus and a rapid reduction in fatigue life, when subjected to dynamic stress. Ihese effects can be reduced significantly by a (cheiio used is outlined below r progressive move towards the use of efficient curing systems for vulcanisation, fatigue life in particular increasing with such changes in compounding. Calculate From slrcss-sttnin '"eniu-*- ol (I .-.sllnl- Chemical proves have been used to study changes in the crosslink structure of SBR during ageing and the results related to changes in physical properties. CONTENTS I. INTRODUCTION Iieal with propane - ? - thiol winch \vntil '\ir pnly<,ulfi'Jir r,rosslinl V. REFERENCES VI. APPENDIX If all the crosslinks ore »ilfidi< <>„• v.,1. nm vit.- rli»-.l v. in Mr I Appendix I for method. * tM trtfa Hrti rtfarrct to it tbii rapwt, b»Miai Mini, riaaUl mi SmVtm U «.HM taTratlaa I" «•!• tolMU U t» air «aat k»a>Iaa*a traa a* ««M< M all iMtruatiaa, •] tttva • oaaaatlaal m aato rilMl pir—aa. Ilaw IM MKitlaa «r m* *• HfM tMlr m ••Mi <••»•» Mi lit HMUUUIM 41HI>1> «* UMIlUf tar »«• - 5 - 11.2 Oxidative Ageing (5) The contrast with on EV system is readily apporent when comparing Figure 1 and Figure 2. During oxidative ageing of on unfilledEVvulcanisateof SBR the crosslink density remains Th« increase in crosslink density during oxidative ageing of a conventional SBR vulcanii constant as does the modulus. is illustrated 'in Figure 1. I FIGURE 2 FIGURE 1 Variations^of crosslink densities on ageing in air CROSSLINK Total DENSITIES * After 8 A Hexane-1-thiol 2 3 4 DAYS AT 110*C 2 3 5 * Crtmlink dtnsiry = NJ DAYS AT UO'C 2Mc phys N.w cro-link, or. form* durinfl oxidativ. ag.ing of o SBR vulconisot. end h«,=e the' '%'• morfulm of the vulconisate increosei also. C3.6 Street relaxotion measurements hove shownthot during oxidative ogeing crosslinks scission The new chemical crosslinks which are formed in the early period of oxidation are os wall os the formation of new crosslinks occurs. predominantly monosulfidic, in contrast to oxidotive ogeing of NR where the new crosillnks are disulfidic. The chemical crosslinks which ore formed after prolonged ogeing The nej increosa in crosslink density must therefore indicate that the rate of new crosslink ore resistant to methyl iodide and ore either oxidised monosulfidic or non-sulfidic. formation exceeds that of chain scission. Some of these non-sulfidic crosslinks probably ariie from the oxidotive croulinking of The crosslink density data referred to in Figures I ond 2 is a measure of the total physically the pendant vinyl groups which exist in SBR. effective crosslinks. To define more precisely the structural changes which occur on ogeiJ It )• necessary to follow changes in the chemical crosslinks themselves. In doing so the I With on EV curing system (Figure 4) some new monosulfidic crosslinks ore formed curing effects of chain scission and entanglements ore eliminated. oxidative ageing ond this formation of new chemical crosslinks compensates for the chain scissions which occur and thus a constant modulus is maintained. The increase in chemical crosslink density which occurs during oxidative ogeing of a conventional SBR vulcanisate is illustrated in figure 3. FIGURE 4 FIGURE 3 Variations of chemical crosslink densities on ogeing in air Variation of chemicol crosslink densities on ogeing in air Effieienl Curing System Conventional vulconisote 12 Totol Total 16 i WICAL After CHEMICAL DSSLINK hexane- I -thiol Afttr CITIES CROSSLINK hexone-1-d DENSITIES * aft« 4 H Mel i r • Chemlwl croMlInk density * DAYS AT U0*C C3.8 C3.9 - 9 - PROPERTIES OF OXIDISED VULCANISATES There is some evidence that crosslinking through pendant vinyl groups will be $lr retarded by the sutfidic species combined in the network. It Is more difficult o why the non-sulfidic crosslinks which ore formed with conventional vulconisat** cannot be detected when EV cucuringg ssystemy s are used. | fchown previously, on increase of the efficiency of the curing systems comiderobl/ A possible explanation is thah t thhe sjlphidilhidi c speciei s present in EV vulcunisates ducei rhe structural changes occuring in SBR vulcanisotes during oxidolive ogeing. mar«ria| possess for greater inhibiting effect in the reactions leading 'o the fforrno M view of 'his, 'he retention of properties on ageing should be enhanced by the use non-tuUidtc crosslinks. \#*>'i EV or EV curing systems, and these effects have been studied in typical SBR SRR Wf Ai ton be seen in Table 1, ihe semi EV systems have foster cure rates rhon fhe conventional or EV systems. Scorch safety is slightly reduced with the semi EV m'«f*n bosed on high accelerator/fow sulphur, and more significantly in the case of *« EV compound, although this con easily be corrected by increasing the Sanlocure NS/ TKiK/fnd ratio. TABLE I Processing and Curing Properties EV 1.2 1*-'or..(e NS 1.7 1.2 7.5 V.I (man R 3 I 2 0.4 ol 135*C '8.7 14.4 14.4 20.4 14 ot I53OC > "mtwboich used. Cariflex 15nn Out Zinc oxi^ acid : 2, C3.1? C:i. l.i TABLE 3 I nliuur lilt. .,1 ,|il(«l.O"l ''HI.' Viil ilmilai pattern has been foumf minq o npw environmental fatigue tester where sample Sulphur 1.2 1.2 1.2 ;*«r>ells of rotation! are subjei tori to on oliiMnnfinq < ompiession 'extension cycle ol Sentocure NS 2.5 1 1 •voted temperatures. (A brief Wesdiption of tl\h equipment is given ir. AppenWix ?. Sulfoion R 1 2 Tbiurod 0.4 *#1ult| quoted in Tahle '1 show thahat lit* fn'iaup tifp is iimproved by about *i0 y about *i0 ?-> wi'h n ••j••jh lloww or a sulfasalf n R semi TV 'uiinn system. Wilt-, f ilt-, fhe fV system foligut til>- is Iniiiol fotigue life ol 80 % extension (Kc) -(Vd by 100 ";. Upp»r 323 275 328 Fatigue life at 80 °o extension - aaed 4 days 85*C Dynamic ogoing .if S[»P ,,,|. 61 HI 107 117 17? ' Ipt... 50% confidence limits i i)-.".-re NS [ i I Lower 40 61 66 85 131 I'own R l 2 0.4 •, t •, test done on the Monsanto fatigue-to-failure tester. i I .'< "••-•ol n •', 0 0.75 life x 10 cycles Forigue dote given in this table has been analysed assuming a gaussian distribution #1 logarithms of the results and the meaning of the figures quoted above is apparent frond following graph (Figure 61. iSO 1 13(1.4 94 7 138 no°c '"•-1 - 50.4 FIGURE 6 '«< '(one ,his envitonrnen.ol in,; .,o 1^,0, . , sample, ore ,,,b Interpretation of fatigue results on n he to 40 % (•••niion and 40 °~ compiossion rluiint, no-l, fyr|e. LOG FATIGUE The highest probobu lute has 50 % ctiwj found between fh«w lines 1.80 EXTENSION RATIO C3.14 C3.1!. - 14; TABLF A At Ih* test temperature it increased, the benefitt of using the more efficient curing become more apparent. For example at 120*C, the Sulfoscn R semi EV system impel fotigue properties by 75 % and the corresponding EV system by meanly 400 % (Tablf Ageing performance of Of SBR/BR blends TABU 5 Sulphur 2 1 1 _ Santocure MOR 1 2.5 1 1. s Sulfoson R - 1 Thiurad 1. 5 - - - 0. 5 Test at 120*C Initial 100 % Modulus at 85'C Strain omplilude 40 % Compression amplitude 40 % kg/cm 13 13 100 % Modulus afterJO days 85'C Sulphur 2 1 1 - Santocure 1.2 1.2 4 1. 5 2 Sulfasan R - \ - 2 kg/cm 24 17 16 14 Thiurad _ _ 0. 5 Increase in resilience aftei 10 days ot 85'C Fatigue life x 10s 10.6 17.5 19.1 38.5 A Resilience, % 7.8 5.7 4.2 7.3 At stress relaxation measurements have shown thot the increase in crosslink density on ageing SBR compounds is the resultant of crosslink formation and choin scittion, it might be anticipated that a smaller increase in modulus would be found on samples oged under dynamic conditions. This does not appear to be the case, as fatigue tests run under dynamic condition at elevated temperatures still show a large fall-off in flex life for conventional compounds in contrast to semi EV or EV ones. To confirm this, samples were dynamically oged for 6 days ot 85°C using the environmental fatigue tester. Moduli! values were obtained at B5°C ot in the static tests. Values obtained (Table 7) show that under these more realistic dynamic ageing conditions As in many applications SBR is blended with Butodiene rubbers it is alto necettoryl the benefits of the semi EV and EV systems are still apporent. evaluate the ogeing characteristics of SBR/BR blends and a typical passenger trend compound hat been chosen for that purpose. SBR 1712 75 BR 1220 25 Dutrex R 15 ISAF 60 ZnO 4 Sunalite 240 Wax 2 Vulconlsotes have been aged and tested at the tame temperature, 85*C. Results jU In Table 6 Indicates that OE SBR/BR blends follows to 'the tame ageing pattern » SBR Itself. C3.16 - 17 - III.3 Properties of solution SBR As there is o growing tendency to reploce OE SBR/BR blends by solution polymerired SBR, eerficulorly for passenger tread compounds, the ogeing behaviour of this polymer has also keen studied. TABLE 7 With solution SBR,as with emulsion SBR, marching modulus occurs during oxidative ageing but car Dynomlc Ageing elsa be considerably reduced by the us* of semi EV or full EV curing systems (Toble 8). TABLE 8 Sulphur Sanlocure MOR 2.5 1.5 Solfoson R 1.5 Thiurad 0.6 •'59 oL.solu'ion SBR yulconisotes Sanfoflex 13 ^ .. _ 2 - Europrene 384 100 HAF 70 Modulus tested ot 85*C - Unog«d compound Outrex R 10 Steoric acid 2 kg/cm2 200% 17 15 16 Zinc Oxide 4 300% 25 23 24 Sontoflex 13 2 lolthur 2 1 1 Modulus tested otJS*C - after 6 days 8 Wlocure 1 Ulmon R 2.5 1 1. 5 kg/cm2, 200 % 40 27 24 1 1. 5 300 % 36 - - 0. 4 Uliial physicol properties 'entile strength, Itg/cm 161 140 llengolion at Breok, % 168 159 350 320 Meevlus 100%; kg/cm' 380 4 on 28 31 28 ?7 'mile strength, kg/cm 140 143 138 146 fiofl ot Breok, % , l°0 270 250 340 I 100 % . kg/cm' 66 43 47 32 C3.18 ca. 19 - 18' IV. CONCLUSION p RT Me 0.78il0* (1 - 2.3 2Mc (equation 2) In the oxidotive ageing of conventional cured SBR vulcoriisaies further crosslink ing occurs ond this has for consequence large increase in modulus and corresponding falls in elongation at break. This has drastic effects on lt| fatigue properties ond can be expected to reduce considerably the service life of ortij Mr7 IS the number average molecular weight of the rubber before cure raid Me Is the subjected to dynamic strain cycles. number average moleculor weight of network chains between crosslinks. In passenger treod compounds, theseeffectsareparticularlyimportantastheycanbeexpecN The number of chemical crosslinks is then : - result in a progressive fall in wet skid resistance and increased groove cracking during service life of the tyre. Such drawbacks can be significantly reduced by replacing > 2.3 conventional curing system by more efficient ones, which do not reduce in any way' -X 0.78*10* physical and dynamic properties. Mn Essentially similar results hove been obtoined with OE SBR/BR blends and also soluti1 2Mc SBR. A decision, at to whether o semi EV or full EV system should be used in a porticulr] 6 2.3 application will be dependant upon the severity of the ageing conditions to be met Where A * - C, • 0.78 x I0 - 1/2 p RT „ the cost limitations of the compound. 2.3 B 4 * 1/2/1 RT x ~- x 0.78 x 10* V. REFERENCES. For unoged vulcanizores the chemical crosslink density can be deduced from Ci, using the Moore-Mulllns - Watson equation.This assumes that no scission occurs during 1. Mullins, J. Poly Sci. 1956 - 1J - 225 vuleonlsation and the value taken for Mn is that obtained on the polymer prior to cure. 2. Moore and Watson, J. Poly. Sci. 1956 - J9 - 225 After ogeing M*n differs from the values obtained above due to chain scission. Conlequen in studying the networks of oged compounds, chain scission must be 'nken into consideration 3. Moore, Mullins ond Mel. Swift, J. App. Pol. Sci. 1961 -5-293 and a new oged value for fXn calculated. One method of estobli-Mng this value Is by oxygen absorption meaturtmenls, and this Is the procedure whir* hos been adopted In the 4. Savllle and Watson, Rub. Chem, Tcchn. 1957 - 40 - 100 work. 5. E.J. Blackman - (Unpublished Work). If q (t) is the number of mala of scission per gram at time tar .oM~n~ and t $n are respectively the initial number overage molecular weight, md that at time I then 6. M.A.A. Wilson - (Unpublished Work). -1 -1 q (t) - I M"S C3.?0 Let (0~1 be 'IT appropriate number of iiolr* of oxygen olixwhed, and f the \ci»ion efficiency. VI. APPENDIX 1 q (I) t Mn - I I Mn o M,, Characterisation of a SBR Vujcanjsate I To characterise its chemical structure, a vulcanisare is treated with chemical reogtrj which give quontitive and selective cleavage of the different types of crosslinks. Knowing C. and Mn for unaqed and aqed somplM it it thus prmihle lo tnlcglnte As the stress-strain behaviour of the treated and untreated samples can be expressed crosslink densities, both physically effective nnd purely t:h«M«mal, terms of the Mooney Rivlin equation (equation )), the concentration of physically By rnecisurinq C. after selective cleavages of the chemireil hands hotween tlm chains, Jive crosslinks f 1 1 can be determined from sirr effective crosslinks f 1 1 can be determined from simple measurement. the nature and thfhe quantitq y of the dlffpionl types of nosslint* fan l)p d#»tmmined. [ 2Mc phy J The different experimental steps or? iised in lh»» followint) ficjure. f -- 2 < \ - v ) equation I , FIGURE *)lructuial analysis o' a vulcanisnlc f " force per unit area of the unstrained cross-section X " extension ratio Stieis-Strtjin r C, and C- parameters characterising the elastic behaviour of the rubbe . Measurements to -I C, related, via the statistical relation C . 1/2/MU (Me phy) "' to the ' 1 Treatment with Propane-2- thiol *itrr>u Strain concentration - of physically effective crosslinks. C'levage of the pol/sulfidic crosslinks Mr jvurementi 2 Me phy Trentment with He*ane-l-thiol Stress-Strain Physically effective crosslinks consist of the chemical crosslinks which are not at al Cleavoge of the d> * polysulfidic crosslinks ends and also includes the entanglements between different chains which under s!m{ behave like crosslinks. Treatment with Methyl iodide The concentration of chemical crosslinks can also be derived from simple stress itioj 'itn'ss-strnin measurement but it has to be assumed that equation 2 developped by workers at Nfj Cleavage of the sulfidic crosslinks Measurements -1.1 for natural rubber ts also valid for SBR vulcanisates. /> - density of the network R ^ run rnmtnnt C3.22 APPENDIX 2 Environm»nfajjajij)uemochine_ The fatigue mochine used enables us to examine the fatigue of rubber at o controlled temperature and in a controlled environment. The cycle and frequency were selected to be as close to tyre service conditions as was convenient. The equipment operates at a single frequency 500 cpm which corresponds to opprox. 30 m ph for a passengn Samples used are dumbbells of revolution of the following dimension : - 0.75" 0.25" dio 0.1875" 0.5" During a cycle these samples are compretted and extended as it happens in a tread dun service. When modulus were measured after dynamic ageing it was assumed thot parts A and C » unstretched during measurement. This is not strictly true and consequently the 200, 300' modulus values quoted are only relatives. However this values do allow meaningful comparison to be made. Printed In Belgium. C4. 1 RECYCLING OF DOMESTIC AND INDUSTRIAL PLASTICS WASTE INTRODUCTION: Modern society is a waste producing society. Whi ne it is convenient for each house holder to take his garbaqe bag, put it in the litter bin and forget about it, somewhere somebody else starts to worry what to do with all the junk that comes rolling Some of this major problems which our society has to face are: i) Environmental problems: Plastic waste which ends up in river streams, dams, etc. Plastic is not. hiodearadahle 1 ike paper and will r emain in eco 1 ogira 1 pys tpma fot: a Ionq time once it is there. ii) Unavailability of dumping sites : As our metropolitan areas qrow new dumping sites have to tr>» found in close vicinity of the suburbs. Valuable land is needed for this which could be better used for industrial or residential purposes. A dumping site must be unoccupied for t— 30 years before anything can be build on it. iii) Once a dumping site has been established/ it can not be moved and people who live clo«p to such a site have to be content with the stench, rats, flies and other nicities it has to offer. iv) Flastic waste is voluminous due to its low bulk density if compared to paper and metals. This problem is amplified that a large proportion of th v) Many tons of valuable material end up on a dump to be destroyed by Landfill. Sunlight.. Fire <^r other causes. h good profit can be made if this low value material is upgraded to a high va]ue r-iw rn^tcrial for the plastics industry. Many different recycling methods are available of which the most important iir** mentioned below; i) Hydrolysis of. Condensation Polymers : By this met'.od the original monomers are recovered and is suitable fo : Polyurethane; Polyamide; Polyester: Polycarbonate. A interesting application would be hydrolysis >t PET bottles to produce unsaturated polyester resins. ii) Pyrolysis : Under controlled conditions ->f actial oxidation polymers are degraded to prodnr<- ^m- > -O" "<»}s nf ^ molecular mass. Temperat- • t-i. ~)0 PYFOLYSIS PRODUCTS (IN WT %) OF THE DECOMPOSITION AT 740 C INCINERATION PLANT FOR DOMESTIC REFUSE Material PS PVC Used Tires Product Hydrogen 0.5 0.03 0.7 0.8 Methane 16.2 0.3 2.8 10.2 Ethylene 25.S 0.5 2.1 2.6 Ethane 5.4 0.04 0.4 1.2 Propene 9.4 0.02 0.4 0.7 Isobutene 1.1 0.2 1,3- Butadiene 2.8 0.3 Penlciic ami i fcxcne 20 0.01 (I. I Ben/ene 12.2 2.1 4.2 Toluene 3.6 4.5 1.1 3.8 Xylene and Ethylbenzene I.I 1.0 0.2 .1.9 Styrene 1.1 71.0 2.3 Naphthalene 0.3 0.8 3.1 0.9 Carbon 0.9 0.3 8.8 42.8 Hydrogen Chloride — 56.3 Hydrogen Sulfide — 1.9 Filler — 7.9 Others*) 17.3 15.0 19.3 17.0 waste gos cw: cooling wattr Flow fcheme of i proem far Ihe pyftriysis nr polyokfins xnd olher poly- mers (TR) (empcriture recorder, (TRC) temperature recorder and controller, (CI) pressure indicator, (CO) pufe glast, (RV) relief valve, (IIR) revet imtkalor anil recorder C4.4 Celsius yield methane gas and unsaturated Hydrocarbons which may be converted into new chemical compounds. dependable composition with regard to * composition. iii) Incineration of plastic to recover energy : Plastic may be a Paper and metals are relatively easily collected and sorted into valuable fuel as can be seen from the following Tabel. their types as compared to plastics. The % plastics waste featuring in this table represents a large variety ot materials of which only a few are compatible with one another. While the ENERGY VALUE (kJAg) largest portion of plastic waste consists of packaqing materials (eg. LDPE; LLDPE; HDPE; PVC; mainly in the form of film and 46 000 foil)/ the more expensive engineering plastics are present in the 46 QO0 form of assemblies (eg. in fridges; TV's; Automoblie parts, etc). 44 000 At this stage only the packaging materials are collected as they 38 000 present less problems in collection and sorting and ervjoy the 19 000 largest demand. 19 000 17 000 Table 2 iv) Utilisation of plastic waste aa a filler in other Polymer types ^ri Packaging materials applications ec|. rrround rigid PU foam ns a liqht abrasive 1 in handcleaners, etc. Polymer '* Jjhint (wt.) XPS in potting soil Pulverized rubber in concrete, asphalt etc. Many more use- full applications could be found. ?0 % 15 % v) Melting of plastics waste to produce a raw material for the JO % plastic industry. This is the most important recycling process currently used in S A and this lecture will therefore only deal with mate- Tabel 2 clearly shows that the Polyolefins (ie t.npE; HOPE; LLDPE) rial recycling. enjoy the greatest share of packaging materials and it is these PLASTIC MATERIAL RECOVERY materials upon which each recycler focusses his efforts. In comparison to other waste eg. paper and metals, the recycling A large proportion of the polystyrene occurs as XPS which of plastic is a challenge to industry as the percentage plastic requires special efforts to recycle. The PS share also tends to contained in waste is increasing rapidly. degrade very rapidly when exposed to sunlight ami it is therefor generally not fit for recycling. Table U PVC col lection at random occurs an a infinite number of compound composition and is therefor difficult to rerycle. Compounds vary from rigid to flexible, clear to pigmented and requirs carefull sorting and matching. Most recyclers win aqree Material Content (Approximate) that the riemanrifo r PVC and the prif-e which may V>c obtained for of domestic refuse Tipping aj;>are (Figures^ r <><••/.-] Hi in in •J»»l«r n«id than Hone. The primary task of the recycle? is to have the material sorted into the various types and to remove all foreign materials adhering to the plastic. (eg. Paper Stickers, aellotape, etc) This job la usually performed by African women who have had no or at th* moat very little training in materials identification. Even to the trained eye some materials are hard to distinguish especially when it comes to co-extrusions and laminates. The trouble is that this operation is the most important of all. The recyclers endproduct can only be as good as this sorting operation will allow it to be. The following table on canpatibi- lities shows that LDPE and HDPE are virtually only compatible with themselves. Even small propertions of EVOH: CA and PA can 1.Washtrough have significant effects on material quality and the overall 2.Auger profitability of the recycling plant. 3.Ventilator 4.Rotary screen to separate water 5.Residual water The water in the trough usually should contain a surfactant and electrolyte which will ensure good wetting of the polymer and flocculation of the dirt particles to make them sink. The pH of the water may be controlled to allow degcedation of cellulose derivations eg. sellotape and papers. The washing plant should have a dynamic water flow to improve interaction with the dirt and continous filtering and perhaps sedimentation tanks. If the High impact tank needs to be drained, the water must first be purified to prevent pollution of river strama etc. by phosphates, nitrates StyrtnttetylonlttUt etc. which occur in it. topolymet « 6 ABS 6 6 1 Folyimlde S 4 <5 Foiycatboiar* Plhyy i mtth*«y1itt FolyfotmildthydK Polyvinyl chloride only very few recyclers have access to this knowlec*jt» which forms Poiypiopyltnt a very important part of their process. Many cecyclern will Uiw ikntity agree that if the material sorting has b*?pn done properly and the polyethylene 6666666666 washing has been done effectively then extrusi >n and High dCfificy palytthyltnc pellitization does not present a problem at all to achieve a good Foiybutyknc product. hhl After washing and drying, the pl/»flti«" fJ*ke ver / often is agglomerated in order to increase the bulk density and feeding characteristic of the material. Allthouqh 'his ip a very conve- nient method to change low hulk den?ih: ';3ke i to high bulk density granular material/ it has more -t; -^tfvant jes than advan- tages. In a agglomerator the material t -• 'ubj»- s>d io very high After the sorting operation the material is chopped and washed* shear conditions and the friction*! h**r uiiicf «vi i*s soften" The washing plant usually consist o£ a trough in which the the flakes* makes then curl and adhp'° to ear othater * - ie paddles. agglomerate to prevent complete fup* - • of ? nr« i ?., C4.B Shematic reactions occuring durinq thermal degradation of polymers. YYVYYY * "• ««<• 9"=UP KiSSion YYYYYY R R R R R ft R R R R R R R R R R AAAAA I \_n cycUzahon •YrTi'R SHEMATIC REPRESENTATION OF AGGLOMERATORS R R R R rrm Tha batch Is then discharged when no more steam escapes from the vessel. By this method a tremendous amount of degradation is caused in the material. This immediately becomes evident in the brownish coloured agglomerate which originates from clear film. Propagation reaction in the presence of molecular oxygen. Of course the mechanisms of these degradation reactions are much more complex. It should become clear however from this that the polymer rapidly loses its physical charateriatics. AGGLOMERATE FILM i) Loss of atrenqth due t.n lowpr molecular nvVJ.i.* Unfortuanately no stabilizer can be added during the ii) Embcittlement due to crosslinkinq; agglomeration stage as the agglomerator does not realy have any iii) Discolouration due to the intr'xIn'-Hfn of ehfomophr* es; good dispersion capability. A sad fact is that once the material iv) Loss of electrical properties due to the introd" lion of contains degradation products ie chromophores, peroxides, free polar groups. radicals, the oxidative degradation process continues autocataly- tic and there is very little that can be done to stop further degradation which becomes almost inevitable in the final process, namely extrusion. C4.ll C4.10 high Another major problem which arises during the extrusion process is that of proper venting. Low molecular mass fractions of degraded polymer, binder of printing inks and residual water from the washing or agglomeration process must be vented. If the melt is not vented/ a porous pellet structure will result which may have moisture occluded in it. This raw material would he useless for film extrusion aa an example. To achieve efficient venting a well designed venting 2one is essential. Technology of most single screw compounders can easily provide for this. There is an problem however. sinqle r*rrt*u oxt-.niripr" r»lv "" rtr«n Flow Tin ninll I tmin|vit I nl. Ion lhrttii<|li (.he ventlfkj zone and nteterinq zone «nd are therefore Influenced by pressure backflow. VV'VV t TENSILE| low v 0 ^Pressure brittle 0,^Leakage t /2?'e Where: n^cnannel depth d^oiameter Counter rotating twin screw extruders on the other hand have a iv) Assembled, structures as are often found in the Automobile industry, should be designed in such a way to make recycling nor* positive pumping effect and are not affected by back of the plastic components possible. Usually these assem- pressure as material transport can be roughly assumed to occur in blies are held together by screws or rivets. It would be discreet packages. good to have the designers look at anapfits or similar assembly techniques which facilitate fast removal of such plastic components. dvujameter v) The Automobile industry should take a long and hard look at h*C>annelde its future. The trend is to uae more FRP which are usually thermosetting plastics (Epoxiea or Polyesters) while these 9? = Helix angle materials surely have significant advantages to metals there *X-An-||i> .if t tin n Will! I tut wu'hft: whl Ii> HO- IMI Because of the forced pumping of twin screw extruders a shorter constructional length can be employed or more than one venting zone is possible. From what has bean discussed up to now it becomes clear that recycling is a necessity which requires people with innovation! skill and a thorough theoretical background. If the quality of recycled material can be improved according to the lines discus- sad, new markets can be found which in turn will reward the recycler with a greater output and profit. In order to enable the recycler to achieve these goals the industries which are linked to the recycler (eg. Municipalities; manufacturing indus- tries, etc) should be aware of these problems and together solu- tions would have to be found which are for mutual benefit. Some ideas to streamline recycling efforts: i) Seperate disposal for plastic waste by the consumers (Householder or industry) to prevent contamination by other waste (eg. steelcuttings, vegetable residues, etc) This system has been successfull in Europe and might even be successful1 in 5 A if the correct incentive is offered. ii) Marking of ec—extrusions and laminates for identification purposes. This type of material is very often difficult to identify! especially in the sorting operations as described 10 C4.14 REFERENCES: DV.Schnabelj Polymer Degradation, Manser , 1981 2)VD1«Vecwerten von tnermoplastischen Kunststoffa voi-verlag GmeH,1979 3)K.J,Tnom4~Kozmi6nskyiRecycling von Kunststoffen 1/EP-Verlag fOr Energie-u. OmweJltschutz. 1987 J iJrethync pmpolymjrs have ber*i available tn 'Iw liquid rtvU-M^t wrielxy frm tiv* late SVr>. Mrjny so called "Work Horses" emergprf at tltat time nr»d have remained urv^tanged since then. In mvty lnr.timccR ur-w npplicaMons for lnyud cast^hlc urethrne prepolymers towj cncrpetl whirh havp bnon *;cit.isfif*l by "Work iVirsos". Cn closer r««mivifcions it bsxnvs apfjorcrit that; theso older products mr\v, in srnc «TftS*s. he over f*^ineercd or oxccsyivcly expensive for a particular application. PiTXiPssing features of sane of the older prenolyners may also sha«r di&irtvjnt,-^es like a hi^Ji wastage factor, due to hifji viscosities, portiatlarly in Uie case of polyester prcpolymers. 5cuth Africa has a liquid castable hot cure induBtr7 which ccntames seme 600 mhs of a total world (mrket. of .Tpproximtpty mts per nrnri. This local miltr-l ir; f tTifltnil/'iI :*v] :t < mvi'i t'n- i>«e;ir>i>i*'. in «*¥» r- i t»V WH hi do iiot pnjvijr; sufiinitait. mt/a-tsit. lor railti iv\ti«nal glMlt nanufaebjrers tn tailor-ffHke formiiatioiia vtfuoh wcolrl provi'le ^pcciTic properties and srrve n p,tvcn purpceo as rvqujrrd by irrtjsi-j-iat cawrrlnnj. Seventy pnr cent of liquid cast urcthane ciflsfccncrs TCmufanUirw! in South Afncn find their \tx in tho mining inietry. 'Die deronds of the aid applicatirm vary firm minn to mine or vise to use 1. IMSRCGEN These arc a collecticn of polyols of varying molecular niei^ite, usually 500 to 3CXX), which provide hydroxyl groups for reaction wi'h tty vario>« Each polyol inpwts certaiji properti'w to &**• pi.irtPTrMtt.lv u> tin finished clnstamer. Ihfi follcwlng table t Pblyol Cut ? I Trysioll FVopertics 2 3 I 'kidative KcHlstancc ? A i i Uw Taipcratiwo Properties 4 5 1 a l fli#i Tcnpemfcurc Properties 1 ;• D/poaic Hsnt OuiM Up ! 2 tydrolysis Rcsistoirp a 5 1 4 flebnuid Rtsilience a 5 T •j 1 viscosity I 1 3 s Hirfwst. or brut. 1 ^ Lcwsit or I.ibl-: :i illunfxrifrr, rr -jr., dun to thnir slower r&-»ctivi^r are vrajaliy chain extended with A,4 Hule not illiKtintoJ to great effoct. in the .ibrr^. wa^lo, ,t |vis been (? (litiTftdiiitinr) ml H5I with tnuUnble diola or trials surti as 1,4 but/Mic diol or t srwrally tmtfc u> di'cp as a result of liyhruHsation. It is also uitcrcnl.im> ta note Uvit t)» hybrirt p-T^u^r rret-, strc )« less in tonrn of to Table 1, it will be noted that no single hydrogen donor possesses desirable ra« imterial versus proActs A and B. pn-jjxTtws in total, tt is therefore reascnable tn EBSMTI: that hydrogen donors could be ccntoincd in sclectetl ratios to yield a polymer exhibiting thn desirable properties of the Table 0 iUuacratra OK prepolymr mid nhvsir.il proprrti-r, of on nstcr/«)I hybrid versiB tuo 3/... cT7i St. H. Klslmann Leverkusen, August 198 7/ro IAYTEC - REACTIVE - ELASTOMER » high quality polyurethane elastomer for abrasion, moisture and corrosion protection t>p*n*ive capital equipment should have a long life. The natural ageing processes which occur through utilization must be slowsd town in order to Increase the profitability of the Investment. The protection of construction works and technical plants against SKhanical demands as well as climatic and chemical Influences b«t a high priority. Polyurethane elastomeres are. as surface protection and also at between surface protection) excellently Ultid. lolyurethane elastomeres are one of the most valuable chemical Mteriali known to man. They are used for the production of high load bearing wheels, Mqhly stressed rollers in the steel Industry, for sieves to •ride ore and sand, and for many more technical parts. Ike extent of the application area has up to now been restricted through the exacting processing technology required. The mostly •olid raw materials are liquified at approximately 100 °C. And •ought up to the required reaction temperature. Through heated puapi the A and B components are fed to a mixing head, mixed and poured into moulds which are at a temperature of approximately tOO °C. It can be clearly seen, that the application of this technique is not really tutted for the easting of parts wich large ertai or for use on site. For these reasons we gave our research, HW 7-8 years ago, the task of developing a polyurethane •iMtoner product which could be processed from raw materials at rood temperature and which required no further thermal after treatment. This staple processing had to be possible without Wilng the well known high quality properties of the polyurethane «e4product. With Baytee-Reactlve-Coatinq we have achieved this fOel. The materials ace solvent free and can be applied with the - 2 - - 3 - desired thickness, because of tha high reactivity of the compo- Th« applications span of Baytec becomes clear In the following nent* after mixing, tha material adherea within a few seconds, examples: that tha product can also be excellently sprayed on vertical walls or overhead, without dripping. In the meantime, many project The produce abrasion reducing layer* on simply profiled, large have been carried out world wide where the Baytec-Reactlve-ElattM area metal parts, e. g. silos, ore product containers and has proved itself. collectors, the liquid at room temperature raw materials A and 8 - polyol and lsocyanate - are, by means of a simple machine metered Mining Industry and mixed and either through high pressure or with air sprayed - ore containers / pipes onto ••ho nhi»/;», p?r abrasion protecticrs sr. elastic coating is - silos, conveyors, cyclones chosen which has a shore hardness of 70 A and an elongation at break of 400 I. In order to achieve an optimal adhesion the metal Ceneral Industry rust be cleaned and a bonding agent applied before application of - containers the Baytec, - pipes / itccl surfaces - rollers The durability of Baytec can be clearly seen on the eccentric serajn of a sand mill which operates in a clay works. The life Building area • ime of Mie (1*001 nillllnrt -lliri ip about *7" bmu n. Throuih t ho - fjat roof / balcony / tor race / ija>tt<|i> I'lviccion '>! '-In* discs wirli Uai'i"-.- MIP lite time WBB Increased - bridges '.0 1,500 hours. Because of this the clay works achieved such - canals / waste water drains savings that the investment 1:1 the casting machine, which was - waste depot purchased for this wori, was already amortized after half a year. - high rise buildings - tunnels As one is with the processinq of Baytee-P.eact.ive-Elastomev no longer bound to the sic? of curing oven or the smallnass of Off-Shore-Area the factory, but on the contrary can also carry out coating work - drilling rig* outside of the factory, Baytee can also be used for the coating - pipelines of large area tippers. The tipper shown in the sketch has been in use in a gravel works near Munich for 2 '/ears and lias already Maritime area nuved 250,000 tons of gravel. - ship decks / loading rooms - quaysides of concrete and steel The coating is still in a problem free condition, it has neither - pipelines visibly abraldnd nor come away from the hose matftrial. " buoys / fenders For objects which can be symmetrically rotated , a particulary Automotive area interesting coating technique has been developed, When for - load bads / tip troughs example a steel pipe is rotated, the mixhead of the casting - underbody protection machine is pulled slowly through the centre of the pipe while the reaction mix is pouring in a constant stream onto the inner surface. The result la a closed, approx. 4 mm thick coating with - 4 - C 6.4 C <>.\ uniform thickness, which also with unbalanced pipes or with internal welding seams maintains a constant coating thickness. polyether basis, and as such have a certain UV-sensltlvlty. The same processing technique is also suitabla for an outside Research has shown that OV-light slightly weathers the surface, coating when the mlxhead travels above the pipe and the raw without excessive deterioration of the functional properties material mix flows onto the outer surface of the pipe. of the coating taking place. The weathering which develops Coatings which are applied by maans of casting have a higher on the surface of the coating through the uv-liqht aaaU the density than sprayed coatings and are therefore of an excep- coating underneath, so that further damage to the material tional quality. I will come back later in detail to this is prevented. It Is In any event recommended in particularly rotation process. exposed areas under the African sun to protect a flat roof Baytec covering with gravel, or to protect from direct sun- light by maans of a pigmented coating, as \n this way the Baytec-Reactive-Elastomer was first used in bridge building 6 years ago. Steel-reinforced concrete bridges are particularly lifetime of the covering will with certainty be increased. at risk through polluted moisture which penetrates the concreu through small cracks and corodes the internal steel rein foremen! Switzerland is a particulary mountainous European country, During the search for a better technical solution to this which requires a number of tunnels, and in this area the most problem, Baytcc was tried as a crack sealing covering under modern building technique has beer, developed. In St. Gal ten the road surface and was then approved by the German authoritiei a concrete tunnel pipe exceeding 12 m In diameter was coated as a particularly effective bridge protector. In the meantime with Baytec on the outside and then bedded down again with many bridges in Europe have been sealed with Baytec. The raw earth. Here Baytec dependably met all the demands of a modern m/it'vt Inl mix i» ni>iayi*O utilo the i.iv«v lona I y c I finned rom,'rnt« ana 1 Ing Bye I Am. suifaiue, so that a joint free "pan" is formed which blends into the side walls, thereby effectively keeping water and moisture out. Later, over this coating, the hot asphalt Hard coating (220 °C) which forms the actual road surfaco, is poured. Testi have confirmed that the Baytec is not damaged by the hot It has been shown in practice, that a part from the soft asphalt and that it provides the essential water impermeability elastic Baytec coating a hard Baytec-Reactive-Elastomer can as well as being resistant to petrol. also be used with advantage. A hard coating is especially necessary in cases where extreme corrosion protection 1* it is understandable that after these successes the coating requiredi as this has a higher water vapour difusion was then also used for flat roofs, which are often the weak coefficient and because of the higher hardness a lilqher point in modern building. The seamless application of this scratch resistance. system provides many advantages as gaps in the roof can be joir.i and closed, Thcac proper ties are h"w»«»r xrhieved with a lower abrasion resistance than that which we came to know with the soft Tht roof of a »ky scraper In Johannesburg, one of the first elastic system. Listed in the table are the characteristics of the soft elastic and the tough hard systems. projects, Is still today In perfect condition. It must however be noted that the polyurethane systems are built up from a With the touqh hard system we have many years of experience, as we developed this product already 20 years ago. but we h»ve in the meantime, because of new pr'orltie* not offered It further in the market, Only because of a no-Incidence v» - 6 - 7 - C 6.6 •: 6.7 once again took note of this old system, which then reminded Based on these excellent results, the ship owners decided In us of the applications at that time. We then examined each July 1972 to also coat the quarter deck Including the walla to a height of 1,6 me'ter. application object and determined that this material gave an •xtraordlnarly long protection period. A check on the new and the old coating early in 1973 proved In Hay 1967 the 305 :i2 surface deck of the 196 tonne trawler the reliability of the coating. In the same year the tough MS.Skarnheim was coated in Aalesund in.Norway. The ship had hard Baytec-Reactive-Elastomer was approved, after tests In the ju«t been prepared for a six month period at sea near Green- fire laboratories of the trade school Trondheim, by the Norwegen land and Newfoundland, with journeys in these aroas tha Sea Traffic Institute for ship's coating. steel parts are exposed to extreme corrosion, which in the case of the MS Skarnheim Is particularly severe, as a The next inspection of the coating took place in 1981. relatively large quantity of salt Is used on board to prepare The coating was found to be intact. Only in a few areas near the catch. As a rule, the usual protective paint had to be the welding seam!,, where the coating had come away from the renewed after each journey, whereby long harbour lay up times steel, was the steel rusted. A little minor damage had also resulted. been caused through inappropiate handling, such as the use of ice hooks and the loading of heavy sharp objects on deck. The 3 to 5 mm thick Polyurethane ccating was applied after the deck was cleaned by means of sand blasting. A bonding agent The last Information received In June 1984 was that the was not used. Immediately after the spraying of the coating coating, after no less than 17 years was now badly damaged the surface was strewn with sand and aluminium oxide crystals through the chipping away of ice. to reduce the danger of slipping. Because of the unfavourable weather conditions (rain, snow and hail with 2 to 5 °C) P»rti™l»rly snhjpr-f t-n rorroeion aro the elements used to resulting in moisture inclusion a few bubbles developed produce the walls of quays and jettys. The tests which were between the steel and the coating. At the end of the first started in 1970 by the company Hoesch/Dortmund in a north German fishing trip in December 1967 the polyurethane coating was harbour showed outstanding results. Tile 28 m long elements seen to be trouble free, as opposed to the weathering of the were, after sandblasting, s[myerl in a factory with a 1,6 - 2,1 mm thick covering of the tough hard coating. A bonding aqent was exposed steel elements which were treated with conventional used for most of the element. The hojps were filled with a corrosion protector. These were badly corroded. polyurethane paste preparation by means of a lance. The bubbles caused by the weather conditions during the coating were repaired in Juni 1968, Corrosion beneath the A report of 1977 from Fernez CxBsz confirms the trouble free coating could not be seen. condition and refers to some mechanical damage through ships. The efficiency was hereby not influenced. Also after 3 years of use even surfaces with a thinner coating such as those areas where horizontal surfaces have bee* Under the title "Corrosion of Steel quay elements" in some blended against the vertical showed no corrosion. East Frisian harbour* construction director Ude Hangen des- cribes that after 12 years the effectiveness as corrosion protector is still very high. Visits to Densersiel in 1984 and later confirm this statement. Damage was found in - 8 - C 6.9 C 6.8 Rotational Processing general only In the area of the expoied dry zone. The causes war* Mechanical Influence! through water craft and loading Of particular interest for the processing of Baytec-reactlve- activity as well as damage in the area of the locks through ramming elastomer Is the Bayer developed rotational process, as it by ships. In isolated cases/ on a few elements bubbles were found allows an exceptionally economical means of providing a high which were caused by moisture inclusion between the steel and value coating on a symmetrically rotatable object. Therefore the coating during the coating process. Underneath the bubbles at this point we will elaborate in greater detail on this the steel was corroded, allthough a creeping of the rust under previously mentioned process. the surround coating was not seen. Stereoscen photos were made of 1.7 mm thick coating samples. In an enlarged cross section The coating of rollers by means of the conventional polyurethane of the material algae growth could be seen to a depth of 0.3 inn. casting system in moulds Is labour-intensive and expensive. The algae covered 'spray water" zone and the barnacle covered With the rotation process no mould is used. The raw material "wet" zone is in a trouble free condition. The coating was not mix is poured with a laminar flow over the rotating roller while damaged either through algae or barnacle growth. the mixhead of the casting machine is moving continually along and above the roller. The speed of revolution of the roller, rab? of The tough hard coating has also proved itself on cranes which travel of the mixhead, output of the casting machine and the are subject to very high corrosive Influences. The crane shown reactivity of the polyurethane system must therefore all be in the sketch is used in the Bayer works in Antwerp where ammonium precisely adjusted to each other. When all these variables are sulphate 1B handled In large quantities. Tho previously used ad3us tad to each other no polyurethane material drips from lacquer had to be renewed every 1 - 2 years. The Baytee-Reactive- the roller but flows together ever the core to form a smooth Elastomer has since been on the crane for three and a half surface. Also with a 10 layer build-up a trouble-free result yearsf and no corrosion damage has yet occured. is obtained, with no delaminatlon of the layers, even when the As outer coating the tough hard system has, amongst other appli- individual layers are applied immediately one after the other. cations, proved itself on special pipes. This coated pipe, In the sketch the process is schematically shown. The isocyanate approximately 2S0 mm in diameter is driven through the earth A is homogeneously mixed with a polycl mixture from B and C underneath the street. The outer surface was, after the pipe plus activator o and then poured over the roller. The use of was forced through, undamaged apart from a few minor scratches. both polyol components allows a variation of the shore hardness from 73 A to 90 A. The metering of activator D is, especially for rollers with a small diameter, essential in order to achieve A test to determine the resistance against microbes showed a satisfactory speed of coating. after many years of storage in soil a rot index of nil le no visible fungus. The coating was unchanged. in practice rotation units suitable for rollers up to 12 Swimming pools, which were coated 15 years ago with the tough meters in length are used, these units being extremely stable hard Baytec-reactlve-elastamer still look good today and are still and also computer controlled. This process could only be in use. He have critically examined further objects which were achieved because the know-how is today available to produce treated with Baytec some 15-17 years ago. Damage could not totally bubble-and pore-free roller coverings with absolute be determined. production safety. C 6.10 With this process one 1* In the position of baing able to offar exclusive top quality polyurethane covered rollers, a* hat already been the case in many industries. Soft tlujlomtr L. Hard eUilomer; . »•. ••-• •• ••••' (ft. jon. .Unit C^siinj Spraying Casting Spnyuig production sheet-metal processing pre»» roll* - driving rolls Density ' 53 4?» 105 0 9 135 1.15 dandy guide rolls - backing rolls Shore A/0 bitUncu { 5.150! -' S3/- ,,- -Pi -1(0 • dandy roll* SlressaMOO* |,JW4 •crimp rollers sheet-metal finishing MPa 4.9 40 strain \-i-v* - - crushing cylinder (galvanizing pirn. Stress at 300% ' , | s w _ - guide pulley shun MI>a 11 f paper processing ,„ • - S-rolls - scrimp rollers Tensile strength ] 5! 504 Mft 16.5 iO - feeding pulleys - backing rolls • Elonplion at break 53 504 - webbreaklng rollers - guiding pulleys * 400 400 50 60 TtArprnr»B:inon | ,,, , IN/m l/.< ,. t» W sheet-metal production mechanical englnearlni) Abrasion ! 53516 nun' loo - S-rolls - carrier roller m ISO 300 - driving rollers - bearing pulleys Tttfrlf •/) I- the mechanical properties of Bovtcc React n-t Ct>ui<>\ - backing rolls - diabolo-rolls - guide pulleys - backing rolls The inner coating of rollers is, with this process less critical. One produces with pre-selected pipe lengths and chooses the preferred pipe flanges. The flange seals can, with advantage, be poured together in one step with the pipe. The variability of the polyurethane chemistry makes the solving of new problems always possible, and even 50 years after the discovery of the polyurethane reaction by Otto Bayer polyurethan* chemistry is still young and dynamic. With Baytec-Reactive- Elastower the evidence of this again shown, it depends on the imagination of the processor and the user a* to what can be Bade from them* products. TABLE 3 C 6.1? BAYTEC REACTIVE ELASTOMER C 6.13 ROTATIONAL CASTING J» COMPONENTS: PU 0309 HDI-PREPOLYMER PU 0310 POLYOL - 73 SHORE A PU 0341 POLYOL - 90 SHORE A PU 0328 ACTIVATOR Rotational-machinery 1. mixerhead-support, threedimensional, with cable-support 2. mixerhead 3. coating 4. roller 5. rollerdrive ARGUMENTS FOR ROT, CAST, WITH BAYTEC 6. starting-help - ROLLER COVERING WITHOUT MOLD - TOTALLY COLD CURING PROCESS - CHANGINS HARDNESS FROM LAYER TO LAYER - SHORT PRODUCTION TIME URETHANES IN MOTOR VEHICLES - A SUPPLIER'S VIEW. C7^1 INTRODUCTION. Of all the diverse uses of Polyurethane (current global usage stands at around 3,7 m tonnes/p.a.) the Automotive industry utilises about 17 x of the total, (Fig 1). We certainly see the Automotive industry to be a growth area for the use of Polyurethanes. The Impetus for introducing increased amounts of Polyurethane in the Automotive Industry was initiated by the energy crisis of the 1970's which brought about a search for increased production economics. Energy savings were brought about by weight savings In substituting PolyurethBne for heavier traditional materials and by improved aerodynamics by Incorporating exterior trim items such as air dams and spoilers moulded in Polyurethane. The United States lead at the end of 1970's was caused by Federal legislation on a 5 m.p.h. no damage requirement for bumpers which lead to the extensive adoption by United States Automotive Manufacturers of soft front ends moulded in Polyurethane using the newly developed RIM process. Today the average weight of Polyurethane used In a car is around 15kg with the anticipation that in 1990 the average car will contain around 25kg of Polyurethane. When we consider figures for the comparative consumption of automotive plastics we find that depending on whether we refer to United States, Europe or Japan, that Polyurethane is generally second most popular plastic employed in the Automotive Industry, with PVC generally being the most widely used. (Fig 2). The major reason for the extensive use of Polyurethane In the Automotive Industry, is the wide range of properties obtainable from the various types of Polyurethane. (Fig. 3). There are indeed a large number of diverse automotive parts that can be moulded from Ralyurethane. If we consider the typical weight of such parts we can calculate that the Ideal car from the Polyurethane raw materials supplier point of view, could contain as much as 35Kg of polyurethane, (Fig. 4). The parts consuming the largest quantities of Polyurethane are of course the foam seat cushions and back rests. Here we see a trend, particularly in Western Europe, towards replacing cut and fabricated foam seats with a moulded seat and replacing TDI-based foams with MOI-based foams which have meant an increase in the amount of foam being used to Improve the comfort and durability of car seating. (Figs. 5,6,7,8). This coincides with world trends generally towards use of MDI in favour of TDI mainly on environmental grounds. (Fig. 9, 10). In the processing of Polyurethane there are certain features that ensure Polyurethane stands out against other competitive plastic plastics. These are:- 1) the comparatively low cost of capital equipment - because we are processing two low viscosity reactive liquids at low temperatures dispensing machinery Is relatively simple and therefore relatively inexpensive. 2/ in ]9 oi CV.2 Page 2. Page 3. 2) Because of the nature of the low viscosity reactants, moulding takes wnts. place at low pressures, 5 - lOp.s.i. - this may be compared to SMC where pressures nay be 100 times this figure or typical thermoplastic injection Again In search of production economics European car manufacturers moulding where moulding pressure may be 500 times this figure - and therefor* have utilised the rapid viscosity build-up of MDl-based systems to develop lightweight moulds and presses can be utilised in the polyurethane process. a process for moulding the sound absorbing polyurethane foam directly onto the back of moulded carpets. 3) Tooling can be epoxy or metal-sprayed epoxy making it cheaper and Another area where the acoustic properties of Polyurethane foam have been quicker to produce than tooling for competitive plastics. utilised is in moulded roof-liners. In this case the foam is semi-rigid rather than flexible, and shows much better absorption characteristics In South African Automotive Industry we have very short production runs - tt« utien compared to competitive materials such as felt and polystyrene. (Fig. most popular model being plus minus 3000 units per month - now the low cost of 11). capital equipment and cheap tooling should ensure Polyurethane's popularity In South Africa. There is a rider to this, and that is that the ease of 3. MDI-based elastomers - integral skin foam & entering the Polyurethane processing industry due to low set-up costs, has I Mlcrocellular mouldings. tendency to encourage manufacturers to enter the market prematurely without them realising the complexities involved in processing Polyurethane - where Integral skin foam has a long history in its use in the automotive one is, in effect, performing an on-site in-mould polymerisation. Such industry where its 'mock leather1 finish has found wide application In process although superficially siirple, requires considerable control to ensun the moulding of steering wheels, arm-rests and spoilers. But in the consistent quality product. development of the RIM process for moulding mlcrocellular elastomers •e have seen considerable development over the years with considerable It Is the Polyurethane raw materials suppliers responsibility to point out potential yet to be realised. these drawbacks to ensure that the material develops its full potential in South Africa where the low volumes and wide variety of models are heaven - sent for the use of Polyurethane. In fact there may be far more potential The RIM process was guided by the Automotive industry through three major in South Africa for Polyurethane than in the rest of the world since elsenhra phases. other plastics m»y be used for components, which may be uneconomic in South Africa due to our low volume. This may be countered by local cnntant Phase 1 : 1967 - 1974. regulations which, in using mass as the governing factor often act against W Phase 2 : 1975 - 1980 use of lightweight Polyurethane parts. Phase 3 : 1981 - present. Phase 1 : included the development of Reaction Injection Moulding CURRENT GROWTH AREAS. urethane chemistry - largly the breakthrough being in developing very high These growth areas in the use of Polyurethane in cars have been Identified reactivity in low viscosity systems that could be moulded at 2 - 3mm sec- tions with a flexural modulus in excess of 500 MPA. The development of high pressure dispensing machinery which mixed the A and B components by 1. MDl-based flexible foam for seating and headrests. high pressure impingement, rapidly followed with the first United States With the growing complexity of automotive seat design based on ergonomic automotive application In 1969, but the real impetus being provided by the United States Federal 5 mph impact no-damage requirement established in considerations the utilisation of MOI-based nigh resilience foam has become 1973. increasingly important in achieving the desired levels of comfort and durability. The use of cold-cure MOI-based processes also allows easier Phase II saw an extension of the use of RIM Polyurethane bumpers particularly introduction of some of the newer techniques in foam seat pad manufacture, In tne United States of America. At this time the chain extenders utilised namely : »ere invariably short-chain glycols. 1) dual hardness foam Phase III saw a new wave of growth based on new technological breakthroughs. ii) "teardrop" encapsulation, The limitations in terms of flexural modulus of glycol-based systems that iii) unit seat production. existed during Phase II being reduced by introduction of glass-fibre The MDI based foam increases in viscosity rapidly during the polymerisa- reinforced systems (RRIM) alongside the introduction of extremely reactive tion which allows for discrete areas of foam with differing hardness as in mine-chain extended systems. The culmination of this work was the release case i), ii), and prevents strike-through of foam through fabric in case In the United States of the all plastic body panel car the Pontlac Fiero Developments in RIM Area. 2. Mm-based flexible foam t*w ""ind insulation. further developments currently going into production Include the use of The increasing competitiveness of car market has made reduced noise level Internal mould release (IMR) system, to produce faster cycling parts by inside cars an important selling point. One way of reducing noise levels 1$' eliminating the time-consuming application of sprayed release agent to the utilise the acoustic absorption characteristics of flexible polyurethane fot>| >ould, and the development of new Polyurea systems which should allow for the in moulding under carpet insulation, and engine-side Insulators that are I [Minting of moulded body panels in the standard automotive assembly line positioned against the firewall between the engine and passenger compart- f paint shop. 3/ J/.J 4/ Page 5. C7.5 Page 4. C7.4 me presence of a large number of German-engineered cars has ensured that Polyurea RIM systems are attracting considerable attention particularly In w I tne moulding of Polyurethane sound deadening pads thrives. The direct-on United States of America. When compared to standard Polyurethane RIM I •ouldlng of foam on to moulded carpet has been called for, for the new system they show particular improvements in terms of heat sag, impact streng*! S*> 7 series and a local converter has developed the process for this and elongation at break. They show some Improvement In terms of dimension*! j wMrement with the likelihood that the full BMW range will utilise this stability on high temperature properties when compared to some of theli mort system in time to come. exotic Thermoplastic Injection mouldable rivals, at the same time they retita the easy processing advantages of RIM Polyurethanes. A unique process for moulding Polyurethane roofliners has been developed locally making parts for the Toyota Corolla range and the Honda Ballade. In terms of bumper production there is a perennial conflict amongst JMs process has been adapted from the original Italian process which has automotive engineers and raw material suppliers regarding the best material not been adopted worldwide because of its relatively long cycle time compared for bumper constructions. There is no one ideal solution, it depends very toother processes. Tor South african volumes however, the cycle time Is of much on the parameters relevant In each particular case, e.g. RUtively low importance and the process has become a cost effective means of producing a high quality product. i) The volumes to be produced. 11) Whether the part should be painted or not, Integral skin foam moulding processes are widely used for production of ill) Is the part cosmetic or structural. Some automotive companies itrering wheels, arm rests and spoilers and other trim items. Armrests are have arrived at solutions that have satisfied both Thermoplastic and Polyurethane raw materials suppliers by this constructing bumpers with •lso moulded by rotocasting PVC and back-filling the skin with semi-rigid a thin Thermoplastic injection moulded outer skin (It can be more Polyurethane foam. At present there is no facility for large-scale production economical to utilise RIM polyurethane skins for low volumes) backed o' Automotive crash pads (dashboard units) since the car manufacturers tend by thick energy absorbing semi-rigid Polyurethane foam. to bring such units in from overseas manufacturers assembled complete with Instrumentation. Another growth area for RIM moulded mlcrocellular elastomers is in the area llkenise there is potential In developing locally moulded door panels of window encapsulation. In this process modular windows are produced for 'ran Polyurethane/Vinyl composites. A number of convertors are set up to a simplified assembly on the production line. One of the big advantages •tnufacture parts through the RIM process, "olyuretnane Bumpers have been of using a modular window approach is that the encapsulant (RIM Polyurethant M It has probably been assumed that most of the preceding paper has referred to Tre use of energy-absorbing foam in bumper construction is also used in developments outside South Africa, however the majority of these products 2 or 3 models. The window encapsulation previously described Is being used in processes and developments are finding their place in the Republic of South South Africa interestingly enough for an export market. There is also Africa. considerable local activity In moulding Air Filter gaskets using •talyurethane. To take the growth areas the majority of South African manufactured cars hsvt moulded seating - there is still some use of fabricated seats either from out T>ie low volume of South African cars has precluded the development of very slabstock or rubberised hair. There are two hot cure moulded foam lines 'ast curing amine-extended RIM systems and one might also be pessimistic in operation, whose viability is dependent on volume passing through them. icout any development here around Polyurea systems in the near future. Thus we still see a higher proportion of seat pads being moulded using the •lth the strength of South African Steel industry the likelihood of replace- traditional hot cure process. Once these hot-cure lines approach the end of wnt of steel body panels with any form of plastic appears remote. There their life the change to the cold-cure process will no doubt be completed. ire however, examples of automotive products moulded in South Africa In The majority of the high resilient moulded foam still uses the TDI-MOI warm Polyurethane typically moulded from other plastics elsewhere. Such a case cure process but in the last year we have seen two convertors changing to Is the squab reinforcer moulded from glass material reinforced structural the MDI-only cold cure approach. Nissan having their own foam moulding plant, torn for BMW and Mercedes. Overseas it is more likely such a part be moulded being one the those two, - It is no coincidence that numerous reviews of the Oy Thermoplastic Injection moulded processes. new model range remark on the high level of comfort In the seating. 6/. Dual hardness foams processed in Europe require some sophisticated robotics, whereas the lower volumes demanded by the South African industry has allowed the development to take place, albeit in a somewhat less-automated fashion - such as moulding the areas of different hardness separately and then Inserting them into a mould for combination Into the finished cushion. V. I APPENDIX. C7.7 Page 6. C7.6 CONCLUSION. FIG. 1. APPLICATIONS OF POLYURETHANES WORLDWIDE. In South Africa Polyurethane, with its low cost of capital equipment FIG. 2. COMPARATIVE CONSUMPTION FOR AUTOMOTIVE PLASTICS (X). and cheap tooling costs appears a very attractive moulding material. Longer cycle times are of no real consquence because volumes are small FIG. 3. RANGE OF POLYURETHANE PROPERTIES. and the fact that operations can be reasonably labour ltenslve should make the processing techniques very suitable for a developing country like FIG. 4. TYPICAL AUTWOTIVE PARTS USING POLYURETHANE. South Africa. FIG. 5. CONSUMPTION OF MOULDED POLYURETHANE FDAM IN SEATS AND The Industry appear to have gone through the major part of the learning HEADRESTS IN WESTERN EUROPE. curve in that the remaining convertors now appear more aware of the problems involved in controlling the in-mould polymerisation reaction to FIG. 6. TRENDS IN POLYURETHANE MOULDED SEATS AND HEADRESTS ensure consistent quality. However, Automotive manufacturers have had some IN WESTERN EUROPE. bad quality experiences in the past and require a concerted joint effort from todays convertors and raw materials suppliers to Increase the level of FIG. 7 POLYURETHANES IN WEST EUROPEAN VEHICLES - 1979. confidence In polyurethane products and ensure that the true potential of this material Is realised. FIG. 8 POLYURETHAhtS IN WEST EUROPEAN VEHICLES - 1985. FIG. 9 WORLD MDI/TDI SALES (1000 TONh€S). ACKNWLEDGEMENTS ICI Polyuretnanes for Technical Data and statistics. FIG. 10 APPLICATIONS OF MDI-BASED POLYURETHAI*S WORLDWIDE. Marcia Yaxley for typing. FIG. 11 COMPARATIVE ACOUSTIC ABSORPTION COEFFICIENTS OF FILLERS IN ROOFLINING COMPOSITES. FIG. 12 POLYUREA AGAINST COMPETITIVE RIM MATERIALS. FIG. 13 POIYUREA AGAINST COMPETITIVE MATERIALS : TEMPERATURE PROPERTIES. FIG. 14 POLYUREA AGAINST COMPETITIVE MATERIALS : DI^NSIONAL STABILITY. 113 19 07 iIT ia nc FIG 1. C7.8 »:; 2. APPLICATIONS OF POLYURETHANES WORLDWIDE. PPARftTIVE CONSUMPTION FOR AUTOMOTIVE PLASTICS (X). WEST EUROPE III •! Ill U.S.A. JAPAN SHOES REFRIGERATION OTHERS FURNlTURE/HATi BUILOING rVCPUR PP ABS PfCNCLIC PE THE.-MGSET PC NYLON POLYESTER AUTOMOTIVE 113 20 01 in 20 02 FIG 3 RANGE OF POLYURETHANE PROPERTIES. C7.10 HQ. A. TYPICAL AUTOMOTIVE PARTS U5ING POLYURETHANE. KG. SrEERING WHEELS 0,8 MSHBOARDS Hit ID 2,0 INTERIOR DOOR PANELS 4.0 SOL ID "tRCEL SHELFS 1,2 KOt LINERS RIGID 1,3 50UW INSULATION 4,0 FOAM STRUCTURAL FOAM SOLID URETHANE SIN VISORS PLASTIC. 0,8 CONSOLES 0,8 *:R FILTERS 0,5 &JM=ERS AND RUBBING STRIPS RI GID TOILERS 5,0 FC 1,5 IUM SIR DAMS 2,0 KEL ARCH EXTENSIONS 3,0 POLYMER WH RESTS RIM ELASTOMERS 0,5 ST1hHNE5b •i® RESTRAINTS 0.6 fiCNT AND RF/W SF/1TS INTEGRAL SKIN FOAM 35,0 FLEXIBLE THERMOPLASTIC FOAM POLYURETHANES SOF T - SOLID ELASTOMERS RUE EER IDG 5GB 300 503 500 6OT5 TOO 800 9G0" IOCS 1155 1200 OENSITY (Kg/m3) 113 20 03 n/i t ; 12 FIG 5 CONSUMPTION OF MOULDED POLYURETHANE FOAM IN SEATS AND - - ''.: 6. TRENOS IN POLYURETHANE WULOFD SEATS ANP HFnDRFr>T5 HEADRESTS IN W. EUROPE. IN w. Eunnn 1976 1984 KG/VEHICLE OOOT OOOT ^ WULDEO 55 39 7 - :> RESILIENCE 10 6 - TOTAL MOUUDED 'AL WULDED FOAM 5 - FOAM A - HIGH RESILIENCE 3 - HOT 2 - 1 - 357S" 15SS" 113 20 OS ,.! JO 0« FIG 7. POLYURETVWES IN M. EUROPEAN VEHICLES - 1979. C7.U ':: B POLYURETHANES IN W. EUROPEAN VEHICLES - 1985. C7.I5 MOI BASED -BASED (49X) ,CX) "I-BASEO (51X TDI-8ASED/ (66.0 X) 113 20 07 on FIG 9 WORLD MOI/TDI SALES (1000 TONNES) C7.16 APPLICATIONS OF MQI-BASEP POLttJftETHANES WORLDWICC. .c-' •'7. 800 - 700 - TDI Furniture £00 - Others 500 - 400 - MOI 1975 1575 1550 1581 I5BZ 1983 I58» 1985 iConstruc'.ton Refrigeration FIG 11. COMPARATIVE ACOUSTIC ABSORPTION COEFFICIENTS OF FIG 12 POLYUREA AGAINST COMPETITIVE RIM MATERIALS. i:;.l'J FILLERS IN ROOFLININC COMPOSITES. 1 RIM PU POLYUREA. Soecific Gravity 1,1 1,0? ACOUSTIC Hexural Modulus (psi) ABSORPTION 72' F 75 000 72 000 COEFFICIENT (X) - 20* F 140 000 115 000 1=8 * F 45 000 12 000 PDLYURETHANE FOAM. moflulus Ratio (- 20* F) hi 2.21 Tensile Prooertles. Ultimate Stress (psi) 3,500 4,700 X Elongation at Break 110 250 Heat SflG 6" overhang 1 Hour (inch) it 2"-C" F 0,5 H, 33)" F 'io'.crea l^CC Impact fFt. 16/in.) 4.0 i:.; C.L.T.t. (incn/incn/'rJ 60 x 10 -n Materials. Thickness (mm) Weight/area (gm/cm') Polyurethane Foam W,5 990 Felt 4,5 I860 Styrene 6,5 (MO COURTESY J. COTTON LTO. in 20 C 7.2 1 FIG 13. C7.2O FIG la. POLVUREA AGAINST COMPETITIVE MATERIAL. DIMENSIONAL STABILITY^ HUMID GROWTH* CLTE»* (lnch/lncn) TInch/inch/*F) HEAT SAG (6 inch overhang) 1 hour) Glass reinforced Polyurea 0,0013 24 Arorphous Nylon 0,0t»5 W At 275*" At 325'F Nylon/PFO n.nrwn Class-reinforced Polyurea 0,03 0,19 Amorphous Nylon 72,5 - • 7 days at 100"F and 100* R.H. PPO/Nylon 0,09 0,13 * • - 20'F to 86"F ill *>n t-> C8.1 'fil BASEP tlREfHANE FUAMS IN MOTÜK VEMfCLC S ( » T A Y [ i > [v. INTRODUCTION For Autonot ÎVP seatiiq, polywrptfiane moulded foam eau bP considered tn hf fhe number one cushioning material. Continuous development of raw materials anij processing equipment has led tn inprovenpnts in the economics of manufacture and the best ririp support and confort. With special reoard to Nissan S.A. this paper will <-,how how, with the co-operation and use of ICI Technology flPI based polyurpthane foam has been introduced at tne Rosslyn Assembly niant to the advantage of both the nanufacturers and the end user beinq the new car owner. Whilst DoJvurpthanp are playino a growinq role in both interior and exterior automotive trim, the najor ijsaae is in thp fon" of seat cushioning. fiver 2% years ano flexinlp pofyuretfiane foan were first used for seat applications i" the torn of cut slabstnck pieces. Since then thp foan industry has bepn ref in ing techno logv, s iiflp1 ifving production methods, and reducing final product costs. The change fron slabstock to noulding was inspired by ( I) the dpi.iand lor conplev snape cushion, with grooves and contours and in high vol une quantity g reamreri for the typical faiiily passenger vehicle and (?) seatina des in" .• Changes away r>on spring based units covered with slabstock to rieen moulded f foari seats acting as conbmed spring / confort layers with a much simpler , final assenbW. * 'lou'dino techniques were initially based on Hot-Cure Tfl! based systens and were followed bv the introduction of less energy-demanding Cold-Curç systems in thp early 197n's hased nn Till /Mill. A standard r.i-ari it iona 1 Hot-Cure foan sy«it*>n has mould cycle times nf up to 30 ninijtes with prncess^nq tenperaturps ran^inq frnn JfiQ - 2?\)°C. Moreover non Id temperatures have to oscillate fron this hiqh level down to 3R°C in thp nrocess leading to excessive energy usage. Cold Cure SySt.ens baied on Tpl/IIDl on the other hand can <;yclp at 6-10 Minutes with denouM times of about S ninut.ps at (-.pr-iperaturps ot 4fj - 6U°C. Further improvenent has been obtained with new systems based on lU)l variants, with cycle times as low as 3-6 ninutes and demo»Id tines of 2-S minutes at temperatures rfown to 30 - 5SnC 'see fig I t P) ca.2 C8.3 Page 3 Page 2 PHODUCT UEVELOPHEWT !o achieve these improvements, the chemical development trend has been towards controlled but higher reactivity systems. The chemical changes in moulded Pi foam, based on MDl have centered on hoth the polyol and isocyanate types. In general, two basic reactions in all flexible foam, have to be considered and have to be optimized with both catalysts, and stabilizers. a) The wrethance reaction which generates the polymer structure, between the isocyanate and the polyol R-NCO + HO-R - R-N-COOR1 'H (Urethane) b) The aas reaction qenerating Carbon Dioxide which is the result of the isocyanate and water interaction. Si * ISjl 5 -,Zi R-Nf.n + H?O- R-NH2 ^ CO? The traditional Hot-Cure systems are based on polyoxypropylene trials tipped 5 » h I !? with ethyiene oxide. They have relatively low molecular weights of the order ! * n of 3000 - 3300 and are reacted with TDl. The Ethylene Oxide contact varies ' fs ; J< J 3? from 6 - 1?%, giving good flow and a final fast cure. Increasing the ethylene * oxide tippinq of the polyol constrains flow and encourages closed cells. In conventional Cold-Care systems two approaches have been used to elevate reactivity and maintain good flow. Firstly more reactive polyoxypropylene triols are used with higher molecular Heights of 4500 - 6000 incorporating ethylene oxide levels as high as 12 - 16*. l' \ Secondly a blend of polymeric MDl with TDl is used. TDl has a significantly lower reactivity than MDl because of the position of the isocyanate group, and ~t ? the retarding steric hinderance of thp methyl group. TDl (TOUIENEDIISOCVANATE) t.l! (2,4 +2,6 (isomers) 1 Q-f i I 1 MDl (D1PHENYLMETHANE - 4,4 DIISOCYANATE) is il 61 Lp If •ill • I f C8.4 Page 4 Pagp 5 The attainment of an all I ID 1 Cold-Cure system has resulted from harnessing the very fast reactivity of MUi through special modification in the combination ADVANTAGES with specifically tailored poiyol formulations. EWIR0W1ENTAL PROCESSING The environmental improvements derived from switching to MDl based foams are MDl Cold-Cure systens are highly versatile in that they can be processed on clearly highlighted by the Nissan conversion. existing production lines either low or high pressure dispensers and fulfil the requirements of the najority of existinq Cold-Cure moulded foam Atmospheric applications. One of the biqgest environmental and safety problems associated with the The introduction of MDl based moulded foar.i at Nissan's Rosslyn foam plant was production of PUH foam is the use of isocyanates and the control of their carried out via a low cost conversion of an existing plant. atmospheric levels in production areas. Since 1982 a" conventional Hot-Cure line for seat cushion, with a snail carousel system for head-rests had been in operation, (fig 3) TD1 used in flexible slabstock, Hot-Cure, and "Warm-Cure" production has a vapour prp^Mirp nf ?, 3 x If) ~'mlii Hn'V' ?t*nf am! rwan'; fhat at normal temperalurpK i nm iMitratinns willl attain and may exceed the 1LV (Threshold 1 t 15o* limit value) of u,0? ppm. HD1 has a much lower vapour pressure of H)~5inn --4rVVSr\N Hg. Therefore its relative toxic hazard is reduced. The benefits qaineri are (i) a lower level of isncyanate in the atmosphere and (ill handlinq of MDl is less of a problem and can be handled at ordinary tenperatures in an adequately ventilated area. (IB. Allthouqh MDl owing to its lower volatility is "safe" in use than TD1, all isocyanates require precautions to keep concentrations in working areas below O- the units set by the International Isocyanate Institute. TEMPERATURE After consideration of toolinq chanqes for Cold-Cure systens, deinould times and curing tenperature requirement, the followinq plant modifications were The Hot-Cure system with curinq tenperatures of +/- I6O-?5O°C resulted in carried out 'fin 4) fairly high working tenperatures, especially in the denoulding areas where moulds were in the order of 95°C, the lower curinq temperatures of 35-5O°C for MDl foam given rise to a much cooler working environment, especially in SA, where ambient temperatures can reach 3S°C durinq the summer nonths. Noise Levels A feature of the MDl system is the curing temperature of 35-50°C which is maintained on the Nissan plant by two hot air ovens, which in operation, produce nuch lower noise levels than the three large burners on the Hot-Cure system combined with the eight large forced air cooling fans (used to lower the mould temperatures before pouring). c c Ptov-t The end result is a cleaner, cooler, quicker, safer working environment important in terms of employee care and safety. This low cost conversion has given rise to the following benefits. C8.6 Page 6 Page 7 PRODUCTION/PROCESSING An advantage for an in-house converter and trimmer like Nissan is the possibility of trimninq seat cushions after +/- 4 hours instead of the 24 1101 systems offer several advantages to the converter on the hours required by TD1 systems, this is of great importance in the production/processing side. The chemical systens which can be processed on inplementation of JIT (just in time) or KANBAN system1; in the Automotive existing production lines, be they low or high pressure dispensers, assist Hanufacturing sectors. processability by reducing surge and flow variability on the machine which lead to lower reject rates. The economics of production which prompted the conversion of the plant at The fast reactivity of HD1 based systens which results in a faster increase in Nissan are clearly illustrated if we refer back to fig. (1) viscosity of the foaming mix although making it more necessary to pay Hot-Cure: Curing 150° attention to sone processing parameters has the advantage of minimising ., ... 220°C Timme 20-3zu-iu0 minutes "1)1 Cold-Cure: Curing 30° - 55°C Cycle time 2-6 n unneccesary flow through ventholes and flasn lines, thereby reducing waste ana Cycle time 2-6 minutes. easing nouid cleaning. Here the energy savings are clearly highlighted - at Nissan the removal of the Tne rapid build up of polyr.ier strength means that nouldings have good strenath rtot-Curinq and cooling sections and the relevant energy saving by replacement at deraould allowing then to be removed from the tool with the minimum of nitti two warming ovens have to date been considerable. Combined with this the damage, e.g tearing. This is of particular importance where moulds have addition of the second dispensor to the production line (obtainable from the undercuts necessitating excessive defornwtion during release. shorter cycle time of Ml)) systems) has effectively doubled the output of thp pIant from ? 160 moulded units pf^r 9 hours shift, to 48UO per 9 hours shift fincrease!number of production cycles obtained via increased line speed resiiltinq from faster demould time). Tnis reactivity also leads to a rapid hardness build up aid is such that more than 90X of the final hardness has developed within one hour of moulding as Shown in (fig. 5). This has ramification in terms of operations of double shifts and / or the total tooling requirement for a particular model line i.e with a lower tooling requirement the Nissan line can support production volumes without introducing a 2nd shift, with all the on-cost that would have resulted. " 1 1 Tin* Period After Moulding Hardness (Sewtons) 1 I Another advantaqe is again related to the lower moulding temperatures, i.e. that start-up times have been reduced enabling more production cycles hence 1 1 Hour 160 1 higher efficiency. 1 48 Hours 163 1 72 Hours 164 Apart from the numerous economic, environmental and processing benefits 1 7 D»y« | 164 obtained from conversion from a Hot-Cure system to a MUl based Cold-Cure system, significant improvements in seating comfort have been achieved. SEATING COMFORT PERFORMANCE Tne advantages here are the capability of carrying out quality control checks on foams sufficiently early to be able to correct machine malfunctions or There are three important properties of a foam seat which relate to its comfort performance. nixing ratios before large quantities of unacceptable foam have been produced. Generally for Till based Hot-Cure or "Uarm"-Cure foam 24 hours conditioning is deened necessary before carrying out hardness measurement. 1. It has to qive sufficient support to the driver in every driving This rapid hardness development means that mouldings do not require a situation without generating excessive pressures on any parts of the Post-Cure. Therefore handling and transport as well as storage requirements body. are eased. !. It has to reduce as much as possible the transmission of vibrations from the car to the body of the drive. 3. It should retain its seating characteristics over a range of climatic conditions, especially changes in humidity. C8.« C8.9 Page 8 Page 9 With regard to the above, tIDl foams exhibit the following features which stiok Hith climatic changes of the extent encountered by vehicles in South Africa them to be superior to conventional TOl/MDl foams. the resistance towards large changes in humidity such as hardness are of Increased importance. HDl foams exhibit better cure, better reaction between MD1 foam has < soft initial feel sinilar to latex and with the increase of the Polyol and isocyanate leadinq to less humidity interference i.e better load exhibits qood support, this is due to less skin densification resulting resistance of the hard blocks to moisture. fron the fast viscosity build up. For the sane reason HD1 foams have a higher sag factor (confort index) (see fig 6) If we look at the hardness variation as a function of the relative humidity Ifigure 8) it can be seen that HDl foam gives better support over long drives and in To reduce vibration and shock the foai.i has to damp vibrations and shocks as humid climatps. with regard to physical properties such as Tensile strength, much as possible. elongation 0 brtt4& Titorstrength and Compression set - formulation nodifications can be carried out to meet the particular use requirements. If we look at (figure 7) we can see the improved damping effect of Mill foan compared to TUl/MDl based systems. /Fig 9) shows typical properties of a MU) system compared to Car Manufacturers specif icationj . *5r i'y..- ... I *; -• • tpKitl I eailoA z\ •.' -:• AL -; .v I -•<• • ,-1 ! " ! ™" j^r.t.1. ftl srn unLK imF.i son HIIMAM Page 10 NOTE: Flarmability requirement passed with MD1 Cold-Cure. OUTLOOK T»e tnlrotiuct ion of 111)1 based Cold-Cure tojras .it. Nissan SA is just part of the quality drive aimed at ensuring that our bodies are built to last as long as the indestructiDie enqines. * natural progression which is currently under investigation is the production of the sc called dual hardness or dual density seats which have been developed around MD1 based foams because of their ability to cover a wide-range of hardnesses just as a function of index. Conclusion Switching to Npl based Cold-Cure mouldings has derived the following benefits. II) Minimum energy requirements in production (II) Cooler, cleaner, quieter working environment. ell) Minima) naterial wastage. IN) A nore resilient, more durable and comfortable end product. The conclusion to be drawn is that wholly MDl based flexible foams are a major step forward in autonotive foan moulding. ACKNOWLEDGMENT This paper would not have been possible without the contribution of Industrial lirethanes (Pty) Ltd, and the foresight and understanding of the Directors, Production, and Product Engineering staff of Nissan SA Ltd. REFEREHCES K Bukowski and U Schoberth S.A.E. Technical paper series 850486 (1985) I C I Polyrethanes Northern Group Technical data. D P TAYLOR Ref: 0«69C CIO. NETWORK WITH RUBBER-TO-FILLER BONDS AND ITS PHYSICAL PROPERTIES S. Wolff DEGL'SSA AG Inorganic Chemical Products Division, Applied Research and Technical Service For Fillers and Rubber Chemicals, Kdlner Str. 122, D-5O4T Wesseling, Federal Republic of Germany INTRODUCTION Nowadays there are adequate interpretations available for the reinforcing effect of carbon blacks in elastomers as far as the filler, i.e. the effects of carbon black struotiirr nnti rarhun M.vk nut r.irc nti-.i, tn cuni'"rn''''. Thp nature of thu «isr.unit«rl buruiiny forct-r; hntwri-n carbon black and rubber range from van der Waals forces to chemical bonding. The synthesis of carbon blacks able to react chemically with the polymer is difficult and time con- suming* yielding only small quantities. This considerably restricts the possibilities of carrying out measurements with this material so that until the present one has been unable to obtain a clear-cut picture as to what extent reinforcing effects - if at all - will actually have to be attributed to chemical bonds between carbon black and rubber. In order to determine the contribution of rubber-to- filler bonds in reinforcement, studies of synthetic siliceous fillers are more suitable. Silica surfaces - 1 - CIO.2 CIO.3 possess a uniform layer of silanol groups which can easily modification of the silica undergo chemical reactions. Bifunctional organosilanes are with TESPT can be cross- particularly suited for these reactions, e.g. y-mercapto- linked by addition of accel- propyltrialkoxi silane or Bis-(3-triethoxysilylpropyl)- erator. As the TESPT is tetrasulfide (TESPT). The reaction using TESPT can be bound in the TESPT/silica carried out in such a way that silica-to-rubber bondB and/ intermediate, crosslinking or rubber-to-rubber bonds are formed. This flexibility in can only take place on the conducting the reaction thus opens up the possibility of silica surface by formation building up various different networks and thus of of silicn-to-rubber bonds. A examining the question if and how these variants affect the schematic representation of Fig.2 technological behavior of vulcanizates. the resulting network is given in Figure 2. THE BUILD-UP OF SILICA-TO-RUBBER BONDS WITH Possible accelerators which can be used in the reaction BIS-(3-TRIETHOXYSILyLPROPYL)-TETRASULFIDE are HBTS, sulfenamides and thiurams In the presence of zinc oxide and stearic acid. For reasons of cure kinetics, In practical applications, silanes are usually used in thiuram accelerators, especially DDTS, are preferred. The combination with sulfur most favorable conditions are obtained when using TESPT and RCKTION SCHCIC OF TESPT accelerators, such as in EC- accelerator in molecular ratios of 1;1. IN SULTUR OWED COMPOUNDS systems . In this case, both rubber-to-filler bonds and Without the addition of sulfur, HBTS and sulfenamides 4 r4 ___ rubber-to-rubber bonds are cannot crosslink polymers at normal cure temperatures in formed so that both types of the presence of zinc oxide and stearic acid, i.e. vulca- bonds are present in the nization with TESPT would only lead to the formation of vulcanizate (Figure 1). Ob- rubber-to-filler bonds. However, if thiuram disulfides are viously this makes it more used, there is, at least theoretically, the possibility difficult to determine the Flg.l that rubber-to-rubber bonds are also formed. contribution of rubber-to- filler bonds towards the reinforcement of silica-containing Figure 3, however, shows by means of rheometer curves vulcanizates. that no cure reaction can be observed when using DDTS, zinc oxide and stearic acid without the addition of TESPT. On However, in an earlier publication it had already been the other hand, a very rapid crosslinking reaction takes pointed out that the silica/TESPT-intermediate, or more place with the TESPT-modified silica, i.e. with the poly- precisely its polysulfide group, formed after the in situ sulflde groups located on the silica surface. - 2 - - 3 - CIO. 4 ClO.b filler are primarily of an adsorptive nature. Rubber networks can also be built up in the presence of zinc oxide and stearic acid by using TESPT/DDTS as a cure system as long as the formation of filler-to-rubber bonds is prevented. In the moat simple case this is done by using carbon black instead of silica. Carbon blacks are not expected to show any appreciable reaction with the TESPT, as the modification reaction - unlike with silica - cannot Pig. 4 take place. Fig. 3 However, the flaw in replacing the silica with carbon It Is therefore legitimate to assume that in this cross- black in order to build up a rubber network with TESPT/DDTS linking reaction only rubber-to-silica bonds are formed is that it is as yet impossible to predict its outcome. if no free TESPT is present. Figure 4 gives a schematic Although it is indeed possible to choose a carbon black and representation of the structure of such a network. Increas- a silica with approximately the same surface area so that ing degree of hydrophobation of the silica with TESPT the diameter of primary particles is more or less the same, corresponds to an increasing number of rubber-to-filler this does not preclude that the two fillers have different bonds. The remarkable feature of this type of network in-rubber structures. This would then mean that an unknown structure is that the polymer chains between two crosslinks factor, i.e. filler structure, enters into the comparison, run from one filler particle to another without rubber-to- which makes it more difficult to compare filler and rubber rubber crosslinks between them. Thus, each individual networks. A similar situation can also be observed for the filler particle represents a multifunctional crosslink. In silica network because there are indications that the the following, this type of network will therefore be in-rubber structute of the silica is changed by the hydro- referred to as filler network. phobation of the silica with TESPT. The opposite case is illus- If one disregards this difficulty, which for the time trated in Figure 5. The net- being cannot be eliminated, the use of the TESPT/DDTS cure work resulting from most vul- system offers the advantage that at equal TESPT dosage canization processes is made both, filler and rubber networks, form the same number of up of rubber-to-rubber bonds, equally structured filler-to-rubber and rubber-to-rubber i.e. it is a rubber network in bonds. which the filler is embedded and in which the bonding Further network variants are obtained Fig.S forces between rubber and - A - - S - CIO.6 (1) by varying the ratio of TESPT-modifled silica to un- EXPERIMENTAL modified silica, i.e. by building up rubber-to-filler bonds via the modified silica portion and embedding the Two test series form the basis of the comparison. unmodified silica in this filler network. One would thus obtain an inhomogeneous distribution of rubber-to- The first test series uses vulcanizates with the compo- filler bonds in the vulcanizate (Figure 6), or sition shown in Table I. (2) by using filler blends containing both modified silica .mtw Mil in. !•<>- M IN) .. • — and carbon black. In this case, the carbon black is 'OKJLJIT10N UMC «IlK » embedded in the silica network (Figure 7). VTCNttC K1> 1 nri WtK jt TO mvtat otetflLiMa MOH«XNCDUS F1LUH HCTHHK , lNHOnOGOCOUS riLUR NE7H0RK «TH CflftMN iLfICK Ton VA, IfMWI0CDWUI ttltP91 10 SILICA MMM 45 « IS H 11 •• ii •• 1 • 9 II IS It IS M u 49 St tCTT ••» 1. Tt« T^^IOIi IN MLCOILMt MlTIO in The following variations were performed in preparing the Fig. 6 Fig. 7 compound: These network variants were prepared and their physical (1) A silica with a BET surface area of 135 m /g was vulcanizate data were measured and compared. totally hydrophobized with TESPT and crosslinked with DDTS during vulcanization. The ratio of silica : TESPT : DOTS was kept constant (TESPT : DDTS = 1:1) and the OBJECTIVES degree of loading varied between 5 and 50 parts of modified silica. The objectives of this paper can be derived from the (2) Instead of the silica, N 110 (BET: 140 m2/g) with a BET above considerations, i.e. to determine whether surface area similar to that of the silica was used (1) rubber and filler networks possess different physical with the same degrees of loading and the same dosages vulcanizate properties, of TESPT and DDTS. (2) a change in the distribution of filler-to-rubber bonds in the filler network has a perceptible influence on The first case described is an example of a filler net- network properties. work (Figure 4), the second of a rubber network (Figure 5), both containing fillers of approximately the same BET sur- face area. - 6 - - 7 - cio.a CIO. 9 The second investigation is limited to a filler loading o of 50 phr. The composition of the compound is shown in adopted. The compounds were cured at 155 C to t99%. Table I and dosages are listed in Table II. The compounds were tested according to the relevant DIN, In the first case, the total amount of silica used was ISO, and ASTH test methods. homogeneously modified by simultaneously adding TESPT during compounding so that the TESPT was evenly distributed over the whole silica surface. Crosslinking was again COMPARISON OF THE PHYSICAL VULCANIZATE DATA achieved by adding DDTS (in a molecular ratio to TESPT of OF A FILLER AND A RUBBER NETWORK 1:1). TESPT concentration, i.e. the degree of modification, wan iirutd AS a parameter. Thun * illlca network WAS obtained Klnrn In I hn cnnn nf I In- In illn Tfir.lM IIKUMMKII nlll'-n with homogeneous distribution of the rubber-to-sillca the number of tetrasulf ide groups per silica particle bonds * remains unchanged on a statistical average, a plot of the physical data versus deqree In the second case, a similar silica network as in the of loading or TESPT concen- first case was built up, with the exception that this tration shows no difference. second silica network is an inhomogeneous one. To begin The rise in Atorque (Fig- with, part of the silica was totally modified during ure 8) Is a consequence of mixing; after completion of this reaction, the balance of the increasing number of 50 phr of silica was added. By this means, the same number rubber - to - silica bonds of rubber-to-silica bonds as In the first case was obtained formed in the silica net- but this time was inhomogeneously distributed, i.e. distri- work. As shown in the plot, buted on only part of the silica surface. Crosslinking was fltorque is directly propor- Fla.8 carried out as in the first case. tional to the silica load- inq, which is equivalent to the number of ruhhpr-to-fi1 lor In (.he third cane, finally, tha same nilica/TKSPT hoixiR fotn»'il. It rnn t hnn n<< l In order to ensure that the hydrophobation take* place For the rubber network, fitorque can theoretically be as desired, the conditions described earlier for NR were divided into a crosslinking and reinforcement portion. The - 8 - CIO.10 CK). II crosslinking portion can be determined by preparing an between the two fillers as well as different bonding forces II • It*. H») 1 • N lit unfilled vulcanlzate with between rubber and filler are not apparent here. This will, the same composition. If the however, be the case in the following. Atorgue portion which has to be attributed to crosslink- ing is substracted from the total Atorque, the fitorque which has to be ascribed to reinforcement is obtained Pig. 9 {Figure 9). This differen- tiation shows clearly the structural difference between the two networks. Fig.11 Fiq.l? Equal fitorque can be an indication of equal crosslinking density. An answer whether this applies in the present case is obtained by measuring equilibrium swell (benzene). If Differences are more pronounced between the two types of one disregards the minor deviations which are probably networks when comparing thp values for modulus at 100, 200, within the limits of experimental accuracy, there is indeed and 3001 elongation (Figures 11,12,13). This indicates that - as shown in Figure 10 - no difference in reciprocal swell the differences in modulus between the two networks might be a function of the strain applied. An examination - as between the filler and the shown in Figure 14 - of vulcanizates containing 40 phr - rubber network over the confirmed that this indication was correct. With increasing A * " "• A whole range of filler load- strain the rise in modulus of the robber network is indeed ings. This seems to recon- faster than that of the silica network. firm the assumption that the number of crosslinks Is the same in both networks and suggests furthermore that fltorque and swell are not significantly affected by Fig.10 the difference between rubber-to-filler and rubber-to-rubber bonds if the struc- ture of the crosslinks is th« same. This finding 1* even more surprising as differences in in-rubber structure Fig.13 rig.14 - 10 - - 11 - CHK1? Harked differences are visible in the plot of trouser Even more pronounced are the differences In the complex tear (Figure 18). At low filler loadings until just below modUlu. B« (Figure 15). and this all the more the higher the maximum at approx. 30 phr no differentiation occurred. the filler loading. In the range of higher filler loadings, however, the gap between the curves widens, with the rubber network giving • f«0| ISS) higher values of trouser tear resistance at room tempera- tHt • H It* i« • H IIS ture. / it 9* / i •• / -It • tiOt y • M lit i * / / s 1 t / £ flLLJX, *hr , iiai measurements (Figure 20). However, it would be wrong to •» • H lit ascribe this finding purely to differences in networks. i '• Other, so far unpublished RUBBEfl NCIHORh investigations have shown a \ II / \ similar behavior of ball \ rebound and tan delta values 1 ru.Lt*. pttr V .V .'P ¥ (Fiqure 21) in a rubber 1CWT. #hr network containing the same Fig.18 t fillers and dicumylperoxide as crosslinking agent and With regard to Shore hardness (Figure 16) and tensile having the same number of strength (Figure 17), both types of networks show largely chemical crosslinks. These corresponding behavior within the limits of experimental Fig.21 phenomena which appear in accuracy. - 13 - - 12 - CIO.1 CIO.lb both types of networks will definitely have to be attrib- regard to the distribution of rubber-to-silica bonds. At uted to differences between the two fillers in structure 5.25 phr TESPT, all three networks are identical. There- and bonding forces. fore, if differences occur, they ought to become more pronounced with decreasing TESPT concentration. COMPARISON OF THE PHYSICAL VULCANI2ATE DATA OF FILLER The course of the reciprocal equilibrium swell 1/0 NETWORKS WITH HOMOGENEOUS AND INHOMOGENEOUS DISTRIBUTION (benzene) as a function of TESPT concentration is shown in OF THE RUBBER-TO-SILICA BONDS Figure 22 for all three networks. With decreasing TESPT concentration the silica networks with homogeneous and in- As explained in the experimental section, three filler homogeneous distribution of the rubber-to-filler bonds networks were compared which each contained SO phr of exhibit marked differences, which - since the overall filler. number of rubber-to-filler bonds is the same - have to be ascribed to their different distribution. The change in 1/0 The first silica network contains 50 phr of silica. The is even more pronounced when the unmodified part of the distribution of the ruhhor-t o-f i ller bonds on t.ho silica r. tlirn in replnri-d with N 110. An in thin innc I he fllliir stit f ace is homogunuous• network is identical with the silica-filler network with inhomogeneous distribution of the rubber-to-filler bonds, In the second silica network the distribution of the the difference in 1/0 must obviously be attributed to the rubber-lo-filler bonds is inhomogeneous. The total amount different interactive forces caused by the exchange of the of silica used falls into two groups: one that has been silica against carbon black. totally modified and another one which has not been modified. CONSTfWT LOflDING (SB phr) CONSTANT LORDING <3t phr> • •••, IIMI • «IO| tlH> • lit, IIMI • •<«, "in The third network variant corresponds in its composition to the second silica network except that the unmodified silica portion has been replaced with N 110. For all three silica networks the usual physical para- meters were measured as a function of TESPT concentration which In equivalent*, to the numhnr of MIM>IT -I o-n I 1 Irn hondR obtained. At equal TESPT concentration the three networks rlq.22 Fig.23 therefore contain the same number of rubber-to-filler The course of Atorque is very similar (Figure 23), with bonds. However, the higher the amount of TESPT used, the the gap between the curves for the homogeneous and the closer the three types of networks resemble each other with inhomogeneous silica network being even more apparent than - 15 - CIO.16 CIO.17 in the plot for 1/0 and showing higher atorque values for CONSTANT LORDING (S« phr) the homogeneous silica network. Here again the greater • ••«, uni tone. difference in atorque, observed after exchanging the unmodified silica portion with N 110, reflects the stronger carbon black/rubber interaction as compared to rubber/ silica interaction. Fig,26 Fig.27 The findings for Shore hardness are similar to those for modulur (Figure 28). With regard to complex moduIns E* at 16 hertz and room temperature (Figure 29) , the three networks rank different- Fiq.J5 ly with regard Co each other. It war, in the middle TFKPT (loumji' r Amjc t h.it t hr mo it pr on* HI need dlMci «>n<-»H lie t. w«p n The plot of atorque versus 1/0 (Figure 24), which the two silica networks with homogeneous and inhomogeneous largely eliminates the differences, shows that the observed distribution of the si 1ica-to-rubber bonds occurred. In changes in Atorque and 1/0 are caused by the same factors. this case, the silica network with inhomogeneous distribu- tion of silica-to-rubber bonds yielded higher E* values Whereas Atorque and 1/0 respond visibly to changes in than the vulcanizate with homogeneous distribution. This the distribution of rubber-to-silica bonds in silica CONSTANT LOADING IS« phr) networks, the differences disappear almost completely in ,, me, urn WMt. the plots of the moduli at 100, 200, and 300% elongation ••t«t nm HMMOC. •>» MBV The tensile strength curves (Figure 30) run in all three ! „ cases through a maximum. A shift towards lower TESPT con- centrations is shown at the transition from inhomogeneous to homogeneous silica network. The different distributions Fig. 32 of rubber-to-silica bonds Fig.31 are most apparent at middle the homogeneous silica network exhibits more favorable TESPT concentrations. The values than the inhomogeneous one. Responsible for the » »l differences in this case can considerable deviations in both ball rebound and tan delta be as much as 7 MPa. This in the case of the replacement of the unmodified silica means that tensile strength with N 110 is not - as mentioned earlier - the type of is very sentitive to changes bonding or distribution ot the rubber-to-filler bonds, but in the distribution of the the fact that the silica was replaced with carbon black rubber-to-sllica bonds. Tne with the changes in filler structure and interactive forces most pronounced differences that this implies. Fig.3O at egual TESPT concentration were observed in the middle dosage range between the 5 C0NSTAN1 10CDING Heat build-up in the inhomogeneous silica network and the similarly structured Goodrich Flexometer (Fig- network containing N 110 instead of the unmodified silica. ure 33) shows a close rela- Again the stronger adsorptive forces between the carbon tionship with tan delta. black and the silica surface may be responsible for this Homogeneous and inhomo- phenomenon. geneous distribution of. the rubber-to-filler bonds in In the ball rebound plot (Figure 31), the gap between silica networks results in the curves for homogeneous and inhomogeneou* silica considerable differences in Fig.33 heat generation, with the - IB - - 19 - CIO.20 homogeneous silica network always exhibiting the lowest heat build-up. also investigated. These deviations cannot without further evaluation be attributed to the difference between rubber- The replacement of the unmodified silica with N 110 to-rubber or rubber-to-silica bonds, since in the present leads to a curve which - at least in the range of higher comparison a change of filler from silica to N 110 was TGSPT dosages - lies closer to the inhomogeneous silica carried out. Both fillers have approximately the came network. surface area hut differ with rpgnrd to their ntructiirn In the network and the adsorptive forces between filler surface and rubber. Only recently has a method been found DISCUSSION AND CONCLUSIONS to circumvent this difficulty. It might thus be possible in the near future to compare a silica network and a silica- The fact that the introduction of rubber-to-silica bonds filled rubber network containing a constant number of leads to a very considerable change and improvement in the crosslinks. reinforcing behavior of silicas has already been widely described in technical publications and is furthermore the However, as long as these results are not available, the basis for bifunctional organosilanes being used success- question cannot be answered conclusively. The present fully in practical applications. comparison seems to indicate that the contribution of rubber-to-filler bonds to the deformation behavior of On the other hand, so far only speculations rather than vulcanizates corresponds approximately to that of rubber- quantitative measurements have been put forward as an to-rubber bonds . If this is correct, the statistical answer to the question whether chemically introduced lenqth of the polymer chains and their distribution are rubber-to-rubber bonds and rubber-to-silica bonds affect more important with regard to the properties of the two network properties differently, and if at all. to what types of networks than differences between the two types of extent. This is due to experimental difficulties. The bonding. comparison of a rubber network against a filler network with normal test methods for network properties should be The situation is less ambiguous if one compares carried out not only at equal number of rubber-to-rubber rubber/silica networks with different distributions of the bonds or rubber-to-silica bonds but also at equal rubber-to-silica bonds* The comparison shows marked crosslinking structure. This pre-requisite seems to be differences in almost all parameters which are commonly fulfilled by using the TESPT/DDTS cure system since the determined in order to characterize a network. In a silica values for fltorque and 1/0 are the same. However, deviations beyond the limits of experimental accuracy were network, the influence of the distribution of rubber-to- found in the stress/strain behavior, the complex modulus silica bonds on the properties is therefore a factor which f*. *r>i a r-j»£>er cf ctser network parameters »h:rt were cannot be Ignored. - 21 - CIO.22 CIO.23 Th« replacement of the unmodified silica with N 110 which was included in the latter comparison reconfirmed the reservation expressed earlier concerning the comparison of ABSTRACT a rubber network with a silica network. The changes in net- work properties observed after replacing the unmodified silica with N 110 are unmistakeably caused only by the The object of this study is to provide an answer to two structural differences between the two fillers as well as questions: (1) in how far rubber-to-filler and rubber-to- the adsorptive forces of their surfaces. rubber bonds lead to different network properties, and (2) in how far they are affected by n homogeneous or Rubber-to-silica bonds, their distribution in the vulcani- inhomogeneous distribution of the rubber-to-filler bonds. zate. and the incorporation of fillers which have a The first question cannot be answered conclusively. Accord- tendency to bind the rubber by adsorption are thus para- ing to the tests carried out, however, it seems to be more meters through which network properties can be influenced probable that the length of the polymer chains is more to an unusual extent. In how far they can actually be used decisive than the difference in type of bonding. The second to influence the practical properties of filled networks in question, however, was answered conclusively: homogeneous the desired direction and thus obtain properties which are and inhomogeneous distribution of rubber-to-filler bonds is better adjusted to requirements, is question which can only most definitely a factor determining the physical proper- be answered by testing their properties in practical ties of silica networks. applications. - 22 - - 23 - CIO.24 REFERENCES (1) G. Kraus, Reinforcement of Blattomera, Wiley Inter- sclence. New York, 1965. (2) E. Papirer, 3. Le Bras, Journal of Applied Polymer Science, 22, 525 (1978). (3) R.K. Her, The Chemistry ol Silica, Wiley Interneionce, New York, 1979. (4) S. Wolff, Kautschuk und Gummi - Kunststoffe, 30, 516 (1977). (5) S. Wolff, Kautschuk und Gummi - Kunststoffe, 32, 760 (1979). (6) S. Wolff, Rubber Chem. Tech., 55 (4), 967 (1982). (7) H.P. Wagner, "Precipitated Silica Surface Modification with Organosilanes and its Relation to the Prop- erties Produced in Rubber and Other Composite Systems,' paper presented at the ACS-Meeting, Washington, Virginia, September 1979, Paper No. 17. - 24 - R1P.1 THE STUDY OP TUB EVOLUTION OF RUBBER EXTRUDERS FROM 1880, HIGHLIGHTING THE MAJOR ADVANCEMENTS IN TECHNOLOGY AND DESIGN, LEADING TO THE INCORPORATION OF MICROPROCESSORS (HP's) TO EFFECTIVELY CONTROL THE PRODUCT BRING MANUFACTURED PAPER TO BE PRESENTED AT THE 9th NATIONAL P R I CONFERENCE TO BE HELD IN JOHANNESBURG, OCTOBER 22nd-23rd 19R7 HI IDDONC.ENG., M.I.MECHE., F.P.R.I. IDDON BROTHERS LIMITED MANUFACTURERS OF MACHINERY FOR PROCESSING RUBBER AND PLASTICS QUIN STREET, LEYLAND, ENGLAND My Paper today will attempt to outline the step by step evolution of a process which, quite literally, started off as a :black art", and indeed remained as such during a period of over seventy years, until, in the mid sixties, designers adopted a realistic and serious approach to convert the Extruder from a basically unrefined tool to an extremely precise and accurate example of indispensible processing plant. Slide 1 Early example of a Forcer - this Slide shows a typical machine of around the 1880's. A period of, at least, Clg.3 four start scrolls in an attempt to produce a more consistant in excess of twenty years had passed by 1880 since the first feed to the die, and hence a more dimensionally accurate Forcers, as they were then called, appeared in our rubber product. Additionally some scrolls incorporate a degree of processing factories. Called Forcers, on account of the fact pitch modification. For example, a decreasing pitch from feed that the word forcer, exactly explained the process. Namely, to discharge, or sometimes a single start with a two start hot rubber directly from the two-roll Mill was guided into the configuration of the discharge end of the scroll, etc., etc. feed pocket of the machine, a simple rotating screw of around 4. The greatest and inevitable progress that had been 4/1 L.t>. ratio transported the rubber through the barrel, by made was the improvement in know-how of engineering techniques, which means it was "forced" eventually through a die. On and the gradual improvement in the quality of engineering emerging hopefully the end product took some semblance of its materials. desired shape. The Forcer, as you will conclude from this Slide was often driven from an overhead line shaft via flat Effectively, we have now rapidly covered the period from leather belts, which in itself was hardly conducive to accurate 1880 to 1940. Sixty years have passed. However, it is output, as inevitably belt slip would leaa to variance in sere* interesting to note that around the 1920's, a novel development speed, and therefore, cross sectional area of the profile or was exploited. tube being processed. Speed of scroll was often a choice of fixed speed or change speed via a system of cone pulleys and SLIDE 3 - This shows what is possibly the forerunner of flat leather belts. our roller die system. Two rollers, mounted vertically, on the exit side of the nip, a close fitting die is fitted, hot rubber Slide 2 - This Slide shows a later development of the being fed in at the opposite side, utilising the same principle "Forcer". Indeed it is true to say that it represents around as for a two roll vertical Calender. Essentially, this device sixty years of evolution. Sixty years of less than dynamic in its existing form enjoyed a short and undistinguished career progress, the main highlights being:- as processors reverted to the more conventional form of 1. A self contained electric drive motor, generally Ext ruder/Forcer. fixed speed, supplied the transmission power. 2. Three, or even five speed gearboxes with SLIDE 4 - This shows a "modern" hot feed Extruder. interlocking gear selection levers replaced the cone pulleys. Basically, the format has changed very little, although in the 3. Scroll designs had changed little, the basic Scroll process of evolution, 1960 has arrived. Over eighty years have being two start constant depth. In situations where it wai now slipped by, and briefly the changes that have transpired deemed important, some work study had produced three and even - 2 - C12.4 Clg.5 are still confined to:- lometimes well, over a thousand compound formulations, derived 1. Gearboxes - more reliable and capable of :o meet their customers demands. This lend to the unwelcome transmitting higher powers, generally three speed introduction of yet another imponderable into our extrusion 2. Scrolls, feed rollers and liners are now process, that of "stock piling" hot rubber in order to allow manufactured in higher grade materials, and surface hardening tne Mill capacity to be devoted to the next work schedule. techniques are considerably improved Initially, the feed stock so produced entered the Extruder at a 3. Around 20% of all machines, in addition to the ttmperature that could vary from as low as 80*C up to around two/three speed gearbox were also fitted with variable speed IJO'C, and with a 5/1 L.D. ratio scroll giving an effective drives. The advent of the variable speed drive being a major ;rocessing length of 4/1 after the feed pocket aperture had step forward in controlling output and quality of output* as «en taken into consideration. This temperature variation was any small deviation in c.s.a. could be finely balanced by a frequently a further element that created often insurmountable slight increase or decrease in the speed of the scroll, thus problems. increasing or decreasing the die pressure and, there-fore, marginally the die swell SLIDE 5 - "What would happen if the polymer was pre 4. Temperature control was still effected by steam and fixed on a Mill, stripped off, allowed to cool, and then fed water valves. When new, the Extruders were fitted with .ito a revised form of Extruder?". Was the enlightened thermometers, but, as inevitably these became broken, the ,-itstion raised in the mid 50 's. The age of the Cold feed operatives reverted to the time honoured "spit on the hand and litruder was upon us. An age which started full of promise, give the Extruder a quick slap" method. The dreaded "black :-.t unfortunately, owing to the relatively low level of art" was still with us, and became even more indispensible as '.ndamental understanding of the extrusion process, was almost scroll and liner clearances became excessive and machine "reatened with extinction even before it had a chance to efficiency, therefore, deteriorated alarmingly. | rralve. 5. A further factor which caused a high degree of early Cold feed Extruder was basically an updated version product irregularity also became increasingly apparent as :! its well tried hot feed compatriot, having basically taken demand for extruded products increased, and processors si the following format. installed more Extruders. Also that of supplying a continual 1. The process where the feed stock is introduced to and consistant quality of feed stock, without the expense of '» Extruder in cold form, i.e., room temperature, would installing new mixing capacity. It was common practice for the »»lously require a considerably extended scroll. Original largar processors to have at laast several hundred, and sinking lead to the conclusion of around 10 or 12 L/D ratio. - 5 - C12.6 C12.7 2. The process likewise required more power, which 2- To facillitate proceRSibi1ity and Introduce a work necessitated uprating the gearbox transmission capability, and input to the scroll, the scroll took on the following fitting a larger drive motor. Typically, therefore, a 3.1/2" features:- Cold feed Extruder would have incorporated a 4 5 hp motor, a) The conventional two start configuration was almost compared with around 20 hp for the hot feed version. Motors universally adopted. Compare this to the Plastics industry, increasingly became of the variable speed type, with a 50/50 who basically adopt a single start configuration mix between variable/fixed speed. b) In order to "work the rubber" and introduce heat 3. The requirement of some better form of temperature into the material being passed over the scroll, the depth of control was realised, and gradually, automatic temperature the flight at the feed section was around 2 to 2.5 times deeper control systems were introduced into the Extruder specification than the depth of the flight at the delivery end, i.e.. the These machines of the mid 50's - early 60's left much to scroll had, therefore, a compression ratio of 2.5/1. The idea be desired. as their specification and level of technological being that this would sufficiently "process" the cold stock and input proved unequal to the process demands. produce at the die head, material of uniformity of mix, and The heart of any Extruder and the secret of its success therefore, uniform viscosity and temperature. or otherwise rests in various areas - very briefly we will Unfortunately, this was not the case, and processors highlight two:- inevitably resorted to foedinq thnse early Cold feed Kxtruders 1. The level of quality and understanding of the with hot material from the Mill, in order to produce an fundamentals of the electrical and mechanical engineering acceptable product. control systems utilised Our next major step forward in the cycle of evolution of 2. The design of the scroll the Extruder, took place from around 1963 onwards, when continuous vulcanisation was introduced by Dupont in the USA, SLIDE 6 - The unfortunate forerunners of our, now well who developed the principles of eutectic extrusion salts proven. Cold feed Extruders incorporated scrolls that suffered L.C.M. systems, and RAPRA in the UK, who pioneered the fluid from the following faults:- bed - BalXotini system. To manufacture a product which was 1. As we have seen, the L.D. ratio of 10/1 or 12/1 acceptable to the automotive industry and others, required a proved insufficient when adopting the scroll technology of the radical rethink of scroll technology, and at this stage, the time, and was, therefore, unable to process a full range of development of the Extruder, as we know it today, was in polymers and hardnesses that were in demand - today this would relation to the progress of the previous eighty/eighty-five not have been a problem years, a unique example of outstanding achievement. The era of - 6 - - 7 - C12.9 C12.8 SLIDE 9 - gives you a typical example as it shows a the mystique and the "black art" of extrusion disappeared for :ro98 section of a typical pipe seal, the width can range from ever with the advent of highly sophisticated designs of scroll configurations. .10mm up to around 220mm, with a relatively intricate range of .ips, etc. , which places quite a demand on quality control, specially as the service duty of such pipe seals is extremely irduous. This seal can be successfully produced on a 90mm SLIDE 7 - Currently, essential features of an 3.1/2") Extruder, although ideally, a 115mm (4.1/2") machine efficient, reliable and versatile Extruder incorporates into •ould be utilised. its design, the following Now we have arrived at the most vital stage of the 1. a reliable and accurate variable speed drive, now ivolution of development of our Extruder, namely, the universally D.C. with refined monitoring systems to ensure that requirement for an effective, predictable and versatile scroll output speeds exactly match the process requirement lesign. Several excellent designs are currently available, and 2. a good feed roll design, coupled with a carefully .' is interesting to note that, broadly speaking, whilst the developed feed pocket profile ;rincipleB of the He dea lgna vnry COIIB iderab ly, the object ivea 3. some form, of which many are available, of ichieved are relatively compatable, and, unlike our colleagues controlling the temperature of each of the zones of the ,n the plastics processing industries, we, in the rubber Extruder, plus, and of equal relevance, the temperature of the .ndustry are fortunate in so much that a well designed modern scroll. Machines nowadays have up to 7 or 8 zones, and you tcroll, is quite capable of processing a wide range of polymers will note, on page 22 how each polymer requires its own reference is made to this most convenient capability on page temperature profile for optimum performance II of my Paper) *. a range of scrolls, both vented and non-vented, to Simply by modifying the temperature profile of the barrel suit the process application. isd scroll of the Extruder, as you will note, enables the SLIDE • - Today, thanks to the very considerable icroll to readily process, in a most efficient manner, an development that has evolved with respect to the design of fttremely wide range of polymers and cross blends. Extruder scrolls, considerable progress has been made. The vastly improved efficiency of the modern Extruder, as you will In order to arrive at this situation, in the mid 1970'e, gather from this slide, means that you, the processor, can now t embarked upon a design exercise in order to establish, in produce on a 90mm (3.1/2") Extruder, what would have required, jr own right, a scroll configuration embracing totally new in the relatively recent past, a larger and more expensive incepts for our next generation of Extruders - the results of 115mm (4.1/2") Extruder. -nich are shown in SLIDE 10 - 8 - ClP.jp The result being the 'Iddon1 high intensity mixing scroll SLIDE 14 we have now really made substantial major (H.I.M.), covered by Patent in the major countries world wide. progress, as you can readily conclude from this slide. Unlike a conventional scroll when the output up to around 40 rpm, is in direct relationship to scroll speed, after which any increase With a conventional scroll of say 15/1 L.D. ratio, two in scroll speed relates to a relatively minor increase in start and 2.5/1 compression ratio, the flight configuration is throughput, and indeed in the most extreme cases, can such that material passing over the root of the scroll, and eventually, if the Bcroll is run fast enough, actually produce, tn.ntrri.il in rnntacy with the brtrrnl liner is the only part to at say 6*1 rpm, only lh*» nnmn vo [ iimn ,in I hn HIT'II I wnuM pto'liif1 experience any semblence o£ effective processing. (iy Idi the at 40 rpm. The H.I.M, version, actually throughout, the whole largest volume in the centre of the flights is subject to speed range produces a linear output, i.e., if the scroll speed virtually no work input, and this situation is aggravated at is doubled, the output of polymer is doubled. The quality of least proportionally in relation to the increase in the size of the product is additionally vastly superior due to the the Extruder being operated. Indeed, the majority of the sheer excellent processing characteristics of the scroll. imparted to the polymer is induced by resorting to the fitting Eventually, a limiting factor of scroll speed is reached, of steel gauzes behind the breaker plate, which is most but this is governed purely by heat generated as opposnd to thr> inefficient, eneryy demanding and produces poor quality efficiency of transportation, as can been seen from the next profiles with a tendency for surging, due to the lack of slide. SLIDE 15 uniformity of the material being processed. SLIDE 11 demonstrates how, on our H.I.M. scroll, the vanes interrupt the material flow, and effectively cross blend the polymer as it SLIDE 16 a good test, for nn Extruder's process inq progresses through the Extruder. The actual scroll and the capability, is to fit a larqe CSA low resistance die to the H.I.H. principle is clearly shown in the next two slides. Extruder in the absence of a breaker plate. Feed the Extruder with two strips of contrasting coloured material, and ideally, as you will conclude from this slide, a uniformity of colour SLIDE 12 shows a non vented scroll blend of the extruded product will indicate an efficient desiqn of scroll profile. SLIDE 13 shows the vented version, where it is The modern Extruder, therefore, is totally predictable. interesting* to note the loss of throughput- is only around 12% - The output for any profile, in any polymer cross blend can, 151 from theory, be exactly calculated for costing purposes, and reproduced on the production floor by an operative. The - 10 - 11 cy?.13 C12.12 MICROPROCESSORS (M.P.'s) AMD THEIR APPLICATION mystique enjoyed by the 'old hands' on the factory floor to manufacture the product has gone. Control systems and a Our industry has to move into a new era of technology if general understanding of good designs have taken over. progress is to be maintained. This technology must be aimed at The advancement in know-how, and improvement in processing plant over the past ten years, at least equals, and 1. improving quality of production very possibly exceeds that of the previous ninety years. 2. reducing scrap levels In many respects, the next ten years will probably see 3. releasing manpower, which can be more effectively little further progress in the development of the basic utilised in other areas extruder. However, new machining techniques, etc., will 4. a constant monitoring and nnrrpeUon capability to advance, hnnd tn hnnri, with realistic vnluo eny I noorlny nnd ensure that any variations in basic materials, factory help to stabilise manufacturing costs. services, etc., are detected and their effects on the end The title of my Paper, provides a clue as to what we can product either totally eliminated or reduced to acceptable expect over the next decade. Most extruders operate on average levels at around 50/60% of their full potential due to many reasons, 5. reducing unit coats some of which are listed as followst- To achieve this, excellent progress has been made in 1. the ability of the operative or ancillary processing developing, what, possibly only a few years ago, presented plant to handle a higher volume of product expensive bulky computers, unacceptable either on a cost 2. heat input into the material being processed during effective or reliability basis. The modern M.P.'s package in extrusion, coupled with demands from industry to limit tho robust, compact, and in real terms, low cost, and coupled with maximum permissable temperature of extrudate to often as low as its now accepted reliability, we have a technological package 100'. or even less that can be put to goad use; a modern M.P. is an exce.pt ionai Ly 3. with a conventional type die head, a maximum line versatile tool speed of around 30 metres per minute is rarely exceeded, It is a simple matter to install a M.P., with the limited by the frictional resistance of the die head capability of controlling 8-12 temperature zones, and in components. The future will see considerable development in •ddltion, monitor and control - design to overcome this limitation 1. acroll apeed 2. driva motor power 3. melt -raiiuci along the barrel - 12 - 4. die pressures, etc Such systems are relatively cheap, considerably less or concentricity will immediately be apparent, and the than, say five years ago, reliable and easily maintained, but, information collected from the scanner will be fed into *. he by and large, customer demand is still relatively low. H.P., resulting in the appropriate die adjustments being Perhaps, over the next decade, the situation will change. Only automatically carried out. Enormous potential exists time will tell. We have, in keeping with many other machinery throughout the industry for such applications, which would suppliers, been endeavouring to establish the exact role of the ensure that tiie savings on scrap products and excessive use of M.P. in the field of extrusion. material would soon pay back the initial investment costs. We are of the firm belief that such low key demands are a poor reflection of the intelligence of M.P.'s, and that the SLIDE 17 demonstrates the 'Iddon' ComputahosH* extrusion system, made possible by the excplIpnrf nnd efficiency of thn modern nxtnirtPr, onqnqnd upon o typical r.inqe reliability or I hi- mixlRin <>xl i uilcM , coupli-i! witli t tic dlli.-.l of process applications, is such that, little or no benefit, M.P. 's. Essentially, it comprises three units:- can be gained by the introduction of a M.P., whose sole purpose 1. the extruder is primarily to carry out the above functions, unless, of 2. the Computahose* variable geometry head unit course, statistical feed back is required for reference 3. the M.P.'s control centre purposes, as is the case, for example, in research and The principle involved ifl quite straightforward, as development. A more demanding and definitive role must exist anyone who has ever involved themselves in the mystery of tube as the prime requirement, and if necessary, the above functions extrusion will appreciate. can then all be incorporated as the secondary requirement for the M.P. We are definitely of the opinion, that the role of thn SLIDE 18 if an outer circular die is geometrically microprocessor in extrusion, is to be able to exactly monitor located exactly central, relative to a fixed inner circular flll rtnportn of thn [lrorlurt boinq m.inuf ,-irl urnri by rho nxrrurier. die, a tube will be produced with uniform wall thickness. I.e., Currently, we have a serious vacuum in the priority development a ntrnlijht, t i u* con<:«nt. i 11; tutm. HI>WI>V»I , nn you will noli' of commercially acceptable measuring systems for everyday from the slide, if the outer die is not concentric, unequal applications. However, rapid progress is taking place in the flows are generated, thus producing a 'bent' tube. By thus development of these requirements, which will enable a controlling the exact location of the outer die relative to the continuous running dimensional check to be constantly kept inner die, the principle of the 'Iddon' Computahose* extrusion upon, say for example, a hose profile. Any change in diameter •yitem, is derived. Straights, (S)-Bend Radii, and Bend Vector angles can be accurately produced to generate any form of - 15 - 'shaped hose'. Perhaps, at this stage, it would be oppoctuno incorrectly implement. CJ ?.IV to demonstrate the process by showinq a video film. ThlH VKi«u film, will, 1 tu»|»', i-mir I uti I vt> I y t-nnltini inv predictions. A process has been developed, whereby a sequence control system that precisely locates the outer die in relation SLIDE 22 (OPTIONS SCREEN) to tha inner die. jives the ability to, at all times, control This display gives six options, marked:- the relative die positions, and enables us to automatically, 1) BLOCK INDEX and very simply, develop a fully M.P. controlled extrusion 2) SAVE DATA system to produce a wide range of formed tubes, either as waste 3) LOAD DATA pipes and traps, manufactured from standard compounds, c.cj., 4) ENTER NEW DATA Butyl or E.P.O.H. SLIDE 19 or by using Monsanto's Santoweb*, 5) EDIT DATA which is a fibre reinforced material, a full range 01 6) RUN DIE HEAD automotive radiator and heater hoses can be continuously The required Option 1 to 6 is selected by pressing the extruded at a rate of up to 10 units/minute SLIDE 20 ami appropriate number key SLIM 21 OPTION 1 BLOCK INDEX (press key marked [1)1 FILM This provides a quick and easy reference as to which Blocks are free (marked 'NOT USED') and which Blocks are Those of you who, like myself, have grown up in the Hlirtr programmed (marked with your Block Code). rule era. possibly have an inherent distrust of the M.P.'s and Pressing ISPACE BAR) reverts to the Options Screen. their technology. Nothing could be further from tho truth. Our admittedly, relatively short experience in this field of OPTION 2 SAVE DATA (press key marked (2)) activities has taught us that M.P.'s used with intelligence This section saves data for future use, and will save-to- are, without a doubt, an extremely effective processing tool. disc, all profiles programmed into the Main Block, and filed under the roclc name And numhm-. Very briefly, the next two slides will dcinnnatr.itu how wi?. •nploying our own skills and initiative, developed what I believe to be. not only a very professional programme, but a OPTION 3 LOAD DATA (press key marked [3 1) program* that, as customer experience and feed back has This section is used to load back into the M.P., proven, is one that is easily followed and almost impossible to Information that has previously been saved on disc. Place data disc in tha drive M.P. instructs - 16 - - 17 - C1P.19 PRESS |C1 TO LIST CONTENTS OP DISC IY1 will ask for the displacement value - this refers to PRESS [LI TO LOAD DATA the required radius of the bend, measured to the centre of the Pressing |C) will list the complete contents of tru now. Key in the relative value to produce the desired radius f) Enter total Bend roil tun ( 1 - 1 BO ) dtac Select the Block you wish to load. press the key mark*! g) SLIDE 25 M.P. instructs BEND VECTOR ANGLE (1- KO) H.P. instructs ENTER BLOCK CODE Enter this in the this refers to the sector of the die where bend is required 160" - 180' are presented vertically; 90* - 270* normal way. then press IRETURN1 On completion, the M.P. horizontally in the conventional manner will revert to the Options Screen PRESSING (S) for straight centralises the outer die and COMPUTAHOSE* PROGRMWE ACTUAL «ny length of straight section can now be keyed into the programme OPTION 4 ENTER NEW DATA (press key marked HI) When profile data entry is complete, press (E] to return to Options Screen This soction in uf»e«l to input n lion" protlli; programme. OPTION S KI)IT DATA ( |>l nnfl kny mnrkod I') I I Throughout this section, the M.P. raises a series of question!, This section allows editing of any Blocks of data stored in the a* the following slides will demonstrate - answered with tn« Data Bank. The M.P. instructs ENTER THE BLOCK NUMBER YOU HSH TO EDIT. Key in a number from 1 to 20. Press (RETURNI appropriate key presses, followed by (RETURN) •nil the system will then display the selected programme and The normal steps are as follows triable the operative to selectively 'EDIT' any section of the a) Enter BLOCK number .lose construction sequence. b) Enter BLOCK CODE NAME (maximum 10 characters) AND OPTION 6 RUN DIE HEAD (press key marked |6]) key in Product Code This section is used to run your programme on the die c) Enter hose inside diameter Dead, and is where the M.P. converts the entered information d) SLIDE 23 Enter EXTRUDATE OUTPUT SPEED (SECS PF» into a series of electronic signals and pulses required to 100mm) by keying in your appropriate linear output speed operate the die head e) SLIDE 24 Enter BEND STRAIGHT OR END (B/S/E/l? 1) M.P. instructs ENTER THB BLOCK NUMBER YOU WISH Praia |E) if entry data ia complete tO RUN PRESSING |B) M.P. queries: ARE YOU CORRECT 2) Key in the appropriate coding number 1 to 20 Press either [Y| for Yei or (Nl for No - 18 - - 19 - C12.21 3) The M.P. then automatically activates the air an I hope that the text enclosed with my paper does not serve to put you off M.P. applications. In actual practice, wo have found that potential users of the system can, with limit"') supervision, successfully programme their own hose profiIf within thirty minutes of being introduced to the equipmant, ami once experienced, dependent upon the complexity of the hose. can easily carry out a typical programme operation in around 2/1 minutes maximum. - 20 - - 21 - 3 S». C12.23 ft I £ INDSX OP SLIDES FOR CONPERBNCR % % OCTOBER 22-231907 *S| *" "5|* li s Ils Screw Forcer cc 1880 lit Hot feed Extruder cc 1940 Iiiliii Roller Forcev ec 1920 Hot feed Extruder cc 1950's/1960'a iU ^ •u u * Early Cold feed Extruder cc 1955/1960 Diagramtical flow paths ot:- a) original conventional Cold feed 1 ill: 1HU Scrolls b) the Iddon High Intensity Mixing (H.I.M.) Scroll Current deaign of Cold feed Extruders • II; Typical output chart SB Hardy pipe aeal O ». 10 CO ii O S o° h a « • H.I.M. Patent Section through a scroll flight 4 « • » u « •• •- b i; Ml. £ -. § S H.I.M. non vented scroll H.I.M. vented scroll Typical output performance for an H.I.M. i ii i m 11? | •croll o i k li It : S IS 3 |S SIS s£8St-' I 3irn ik i III k inn i ill liil i C1?.JM Comparison graph showing the parameters nl processibility between conventional and mixing scrolls SLIDE 16 Samples of large extrusions processed conventionally vis-a-vis a mixing scroll Iddon Computahoae* extrusion system Plow through cL ~- l«ir apcriutc tlit>u Non reinforced hose sample SLIDE 20 Monsanto die system SLIDE 21 Santoweb* hose samples Computahose* options screen Computahose* V.D.U. slides C13. COATED ULTRAFINE PRECIPITATED CALCIUM CARBONATE - A FHI.EI OR AM EFFECT ABD1TIVE7 D W COMIWELL, 'WMNOflL' SALES DEVELOPMENT MAN AC EH ICI CHEMICALS ADD POLYMERS CROUP, 1UNC0M, ENGLAND Syeopeie It diacuaaea tbe capabilitiea of compound* containing 'Wionofil' a faaiily of coated ultrafine precipitated calcium carbonatea manufactured by ICI Chemical aid Polyaera Croup in tbe UK vbich are achieving continuing aucceaa aa performance alternativea Co exiating proceaaing aida and iapact aodifiera in a vide range of PVC applicationa. Tbe ua* of ""Winnofil' to improve the cconoatica of the uae of titaniua dioxide ia weatherable gradta of rigid PVC ia alao deacribed. The econoaica of tbe uae of CFCC e-e an alternative proceaaing aid and impact enhancer ia covered aid finally other application areaa where tha performance behaviour of CUPCC cao be uaed to advantage are briefly reviewed. Introduction Compered to tbe geological age of theae natural producta made uaeable by •eehanieal grinding and claaaification,precipitated calciua carbonate, aa typified by tbe 'Winnofil' range of producta manufactured by ICI, are a relatively recent innovation. Pirat produced over JO yeara ago for uae in natural rubber to enhance key phyeicel propertiea, their uae now extenda to C13.8 CM.. I the re..on for carrying out thin procpsR in bent apprecinted by viewing electron micrograph! (Figure 1). Ibe icrograph of the ground calcium carbonate reproncntu perhaps the bent ftC, peiet Uk, elaetoaeric eealante tad automotive coatings. In tb«M •ue, shaph e andJ si:z ••plicatioa ereae tk«y fuaction to product • technical effect b*yoad tb* " • "- distribution nchievable by a mech»nic»l grinding o»r.tion. In conpa i«on the aynthetical Iy p: educed 'Winnofil' ' calcium capability •( gtowsd cclcium carbonate fillcra and otbtr more expeneivt tad ftrbonate deaonatra eophieticates additives. Tha vWinnofil' range of ultrafina coatad e» a particle nije order of magnitude mailer, B regular IDd control led part cle flhape and a vpry nar ow B17.P distribution HR would be precipitated calcium carbonataa (CUPCC) ara characterised by their primary tlpectcd from a con particle eise (0.07 microaa), thair regularity of ahapa and oarrovnesa of rolled preripitat ion pro PAH. Tlif t^t-oHnct ion of i»nch *mn\ I mil defined crytti * is only pniMible by me on «f n rli«nica 1 prrcipi i at i on particle aiae dietributiontaurface coating of calcium ataarata and high purity. Tke combiaatioa of tbaaa propertiaa clearly differentiataa COPCC fro* ?Toce»«. inpo sible to mechanically gr TIJ calcium r«rbonnte to this grouad calciua carbonate fillers and ia atao a factor in explaining tba use. performance affecta vbicb are obaarved during the uaa of tba precipitated prodncte. Tkia talk deacribea tba method of aaoufacture for tba ICI product Ibt primary particlea of the CUPCC (0.075 micronii in diameter ) are vtfiaaofil' and givea examplea of ita uaa in a range of application! vttb in the powder Btate to >ljim (Figure 7 ) but Hi .p-rsion and miKinK pi explaaatioae of tha meehanieme involved. •How breakdown towards the primary pnrti.lp unifR. Haaufactura of Coated Oltrafine Precipitated Calciuai Carbonate "Hiaaofil' ia tkc ICI ttadenaaa for a range of coated ultrafina precipitated calcium caraoaatea manufactured by ICI Chemicals and Polyaera Group at Lostock, Ckeahire ia faglaad. Tke producta are a •yotbetic calcicic font of calciuai carkoaate prodacad ay a precipitation proceaa. Tkc aaia raw material for tha ^Winnofil' aanufacturing procaaa ia aourcad fraa toitoa, Berbyakira. taglaad where ICI Liae Croup operatea an extenaiTa qverryiag operatioa priacipally intended to produce, aggregate liaaatoaa for kuildiag/coaatrvetioa, quickliaa for tha atcal induatry and hydratad lisa for agricultural aad general induatry uee. A portion of tbia high purity mineral calciua carbonate ia tranaported by rail to ICI loatock Horka, a diataoce of toaie SO ailee from the aource quarry to forai tbe atartiag point for tha 'Winiiofil* manufacturing proceaa. Tbe geaeral reaction acheme ia illuatrated in tbe 'Hinnofil' proceaa chart. iLIMKSTONtl -> I COKE I- ->lquicn.iHEl I I I I I I •EACTIOH MOCBSJ I CAIC1DN I CaCOj—> CaO • C02 IBYMOXIDII I I CaO • IjO — > Ca(M)2 I Ca(0t>2 • CO2 — > CaC03 PHeCIPITATIM CUPCC EfFFCT ON IMPACT pniAVlOUR WINNOFIL TUPKAL PROPERTIES PVC is a versatile polymeric material, but one prone to brittle fracture upon i«pact,particularly at low temperatures. It is, however, possible to enhance typical properties of commercially available CUPCC are shown In Table 1. the impact behaviour of rigid PvC by modification to the polymer composition itself Or by compounding impact modifiers in with the PVC. The incorporation Stearate treatment Is carried out to hydrophobe the surface, thereby attistine of 'Winnofil1 into a rigid PVC compound will greatly enhance the impact dispersion through better netting of the calcium carbonate in elastomers. Tht behaviour relative to both the unfilled polymer,one containing ground calcium alkane fatty acids are widely used because they are compatible and bond to tht carbonate and any modified PVC.(See FIGURE 4A.4R). filler surface at the calcium salts. The coating cannot be removed by solvent e»traction clearly Indicating it to be bonded to the calcium carbonate The actual increase In impact strength obtained with 'Winnofil' clearly is Influenced by the formulation and the test method used but Improvements of 3GK surface. wd above are seen with falling weight tests on rigid pipe. With Charpy V GENERAL APPLICATION CRITERIA notch testing of modified PVC,hinge break failures are seen indicating a ductile rather than brittle failure mode due to the pressure of 'Winnofil'. The «1de range of chemical, physical and industrial application areas for the The enhanced impact strength is seen across the whole range of rigid PVC 'Hinnofil' range of products are defined by : implications encompassing modified as well as unmodified formulations. - The ultrafine nature of the primary particles. The e>planatton for this lies within the PVC matrii. - The presence of the fatty add coating - The aggregate strength (Fig 2) Irittle failure in rigid PVC occurs via a crack initiation and propagation - The optimum surface coating distribution lechanism. The greater population of 'Winnofil' particles act as - 1h* ability to e»ert control over the above individual elements to gain the crick arrestors being capable of distributing the energy involved. The more toaplete gelation results in a PVC matrix with a lower concentration of defect balance of properties required. tites which can otherwise readily act as crack initiators. 'VUMOFIL,1 - EFFECTS M MGlo PVC Organic impact modifiers can be used to enhance the impact behaviour of rigid It but their use at high levels adversely affects melt rheology In addition to If *N1nnofU' Is compounded into rigid PVC several quite specific effects are llgnif icantly increasing compound volume costs. The classical 'S' shape curve observed. Amongst those seen are : lor modifier/PVC impact behaviour can be shifted by the use of 'Winnofil' iltoving reduction in PHR modifier,generating positive cost savings. Ground 1. Shorter fusion/gelation time. ttlcium carbonates are Incapable of generating this effect.'Winnofil' enables a 2. Enhanced Impact strength particularly at Ion temperatures. 201 reduction of organic modifier content with no adverse effect on physical J. Improved surface finish and gloss. woperties. Kelt processing behaviour will be improved. *. Elimination of plate out. 5. elimination of surface defects, 1e sharkskin which occurs under Hfect on Surface Gloss conditions of high shear gradients, such as those seen in Injection moulding operations. These observed effects are usually associated more with the use of organic processing (ids and Impact modifiers than with the use of only an Inorganic additives. However, the fact is that they are real effects seen with 'WnnofU* and clearly offer performance and economic benefits. Verials sometimes difficult to process such as CPVC trt made more manageable «FECT Of CUPtC ON P¥C Ml A! ION UK f CUPCC is Included in the formulation. The degree of (elation 1« a measure of the breakdown of the PVC structure. I' MECT10N MOULDING the PVC Is under gelled or over gelled poor physical properties will result. 'HinnstU* because of Us very snail particle site and unique surface coat ins Hinnof11 * containing moulding compounds demonstrate excellent processing generates fast, efficient gelation in any PVC formulation. xhtviour and produce components with high gloss without the need for The reason for this behaviour Is the comparability of the 'Winnofil* primary ;Mventional processing aids. Ground calcium carbonates fall to match this parliclc siie of 0.075 a1crons,w1th the primary PVC particle. This jrrformance even when used in combination with process aid. The formulation compatability allows good contact Ic develop which Is instrumental in Kiev illustrates the reformulation trends possible to eliminate process aid in developing frictionet heat, tecause of the large number of 'WinnofU' ml ding compounds. particles present,this effect Is distributed evenly throughout the PVC matrii. This result* In a more efficient heat up and ultimate fusion of the PVC PVC 100 100 «ranuAes,henc* the earlier gelation. HSURE S. PROCESS AID 1.5 GROUND CALCIUM CARBONATE J 'WINNOFIL' 5 The "Wlnnofil1 formulation represents a *io.nifleant cost saving. C13.6 OTHER APPLICATION AREAS FOR COATED PRECIP1T AIEtl CALCIUM CARBONATES IFFECT ON PVC WEATHER At IIITY Th« use of precipitated calcium carbonate in rigid PVC is fust one example of tltt very wide range of performance applications for the 'Winnof U' range of groducts.Scune of these applications have a basis In the primary physical "WiaeoUr ia rigid PVC baa a poaitive effect oa weatberiot by: •roperties of the product in terms of particle size,surface coating content, thereas the performance In other applications relies on a more complex mixture (i) allowiag aildet extruaioa conditioaa ptoduciag a «ote atable polyaer; if criteria which certainty for the ICI range of products are controllable. hlM are listed some of the applications in which 'Vinnofil' 1s successfully mtd. (ii) pttrvidiag eabaaced aurface glosa aod light acatteriag; (iii) efficieat abeorptioa of HC1 thereby ishibitiag debydrocblorination aad giviag reduced yellowing. IMLICATION Aa a coaeea/aeact of the improved diaperaive behaviour of *Viooofil* it ia EFFECT BENEFIT toaaible to iaarove tbe utiliaation of titaoiua dioxide pigaent and obtain UTURAL/SBR RUBBER e^nivaleat vaiteaeea levela at reduced levela of pigaenc. Uhen uaing a IMPARTS HIGH TEAR STRENGTH REDUCED REJECT RATE precipitated calciua carbonate to replace a grouad calciua carbonate filler n IMPROVED DUALITY ia aoaaibl* to reduce tbe pigaent content by SOX without affecting the RESISTANCE TO FLEX HARKING whiteaeaa. Thia very clearly baa economic benefita and alao helpa to ainiaiM MSTICISED PVC EFFICIENT HCL ABSORBER abraaive damage to axpeneive extruaioa equipment. LOW HCL EMISSION PVC IMPROVES SCRATCH RESISTANCE ACTS AS A PROCESSING AID REGULAR CELL STRUCTURE CfUUUR RIGID PVC AND MELT STABILISER. COST REDUCTION CUFCC IMFACT STRWCTI PLASTISOIS FOR IMPARTS A YIELD VALUE,GIVES SPRAY APPLIED PRODUCTS L* •jTOWTIVE USE A LOW HIGH SHEAR VISCOCITY WITH EXCELLENT RHEOLOGV WITH RAPID RESTRUCTURATION. CAN BE PRODUCED WITHOUT HAS NO ADVERSE EFFECT ON USE OF FUMED SILICA. ADHESION REDUCE ADHESION PROMOTER. r n < PVC U1TI 6PUI W1HHOPIL 0.07 HICIOX A •.ISTOMCRIC PROVIDES THIXOTROPY AND IMPROVE PERFORMANCE OF IIK.MTS Ic ANTI-SAG BEHAVIOUR.GIVES SEALANT BEYOND THAT SEEN REINFORCEMENT IN CURED WITH MORE EXPENSIVE pvc win trai 1 MICKM CALCIUH CAUOMM SEALANT BUT RETAINS LM THIXOTROPES AND FILLERS. PILLM MODULUS.ENHANCES PHYSICAL GIVES A LOW MODULUS 1 PROPERTIES. PRODUCT WITH HIGH JMT. *l 1 HI MOM flLLM REDUCES FORMULATION COST. •MT REDUCES SETTLEMENT DURING IMPROVES STORAGE LIFE. STORAGE. IMPROVES DISPERSION ENABLES REDUCTION OF OF PRIMARY PIGMENTS. PRIMARY PIGMENTS GIVING REDUCES SAG ON APPLICATION. COST SAVINGS. REDUCES SETTLEMENT. IMPROVES INK STABILITY. IMPROVES DISPERSION. REDUCES SETTLEMENT. T 2 3 « 5 READILY WETTED ASSISTS WETTING OF OTHER FIR TitaaiuB Dioxide INGREDIENTS. ENHANCES SHEARING FORCES. REDUCED MIXING TIMES. MUTENESS OP CUPCC KELAT1VE TO CALCIOM CAHOMATI PHUI EFFICT OM C13.8 Mi; 1 C13.9 UNO. US ION TM» NX' has atteapted to demonstrate that stearate coated precipitated c*lc •otk "WHItrOfll.' and 'FOUTINIx1 have a cheaUal basis as caUlua carbonate •«?* a*. inuismsslON ri.tCTRfiN HrCROCItArH X6OK (a) Ornund Cjiirium Cjirhonate I (b) 'WinncM!' Precipitated Cali-iun Carbnmtt C13.10 TMLE 1 TYF1CAL "tHHNOPlL' PROKHltt 0.0*5 - O.Ot . *«ticl« SUt <|«>* 19 - 25 1ET Surface Area <»Ji-l) by »itro»e» Adtorption 2.45 - J.» Co«tiot.t C.lci««»t»" (W») 0.* Hoi»tur« Conte«t ««/«) <0.05 (eaiduel ot ** "• <*> 0.J5 Four Dtmity (Kf d^3) 35 BOF Abtotptio« - Manual it Hater) Moderate to emcallent (heolO(ical b.hayiool in aeala>ta.p>i*t* an4 laVa. Good to excellent Diapcraabilitj White Fowder Mature opy * |y air permeability and clc C13.1? FIGURE 4A 1HPACT TEST BEHAVIOUR OF 'WINNOFIL1 IN RIGID PVC CHARPr U NOTCH ?O CENTIGRADE 0 CENTIGRADE -20 CENTIGRAOE 1 1 I 1 1 5 6 7 1 9 10 UINNOFIL S PARTS PER HUNDRED RESIN FIGURE 48 IMfACT TEST BEHAVIOUR Of VINNOFU IN RIGID PVC CHARPY V NOTCH 0 CENTIGRADE 20 CENTIGRADE -20 CEN1 ADE V1NN0FIL PARTS PER HUNMU RESIN PAGE 1 ' REil)JF9BEEB£N!_Qr_.EiaST9MERS.ANp THERMOPLASTICS WITH.KEVLAR*. 5HQPX Jl BBSS Kevlar* p-araiid is well-known for reinforcement of thermoplastics: the yarn form provides composites with desirable properties such as superior stiffness, impact resistance and vibration damping at lighter weight. Recent developments with Kevlar* in pulp and short fibre fora take use of the outstanding properties of the fibre in reinforcing elastomers and thermoplastics. The paper concentrates on what the desired properties are, how to achieve them, indicates some commercial applications and future directions for the various types of composites. Ktvlar: what it is Kevlar* is Du Pont's registered trademark for its high tenacity para-aranid (aromatic polyamide) fibre, invented in 1965 and vade commercially available in the 1970's. Chemically, Kevlar* is poly-paraphenylene terephthalamide (PPD-T) . Its high tenacity properties are obtained by orientation of the molecules during spinning. Properties such as tenacity, modulus of elasticity, and elongation at break can be tailored to meet end-use requirements. The two main types »re Kevlar* 29 and Kevlar* 49. Kevlar* is intrinsically yellow. Some principal properties Table 1 shows some of the more important physical properties of Kevlar* and compares them with nylon 66, polyester, E-g]ass, carbon fibre and steel wire. The aramid fibres have the highest tensile strength of all these fibres, measured both on cross-sectional area (MPa) and linear density (dN/tex) bases. On a weight-for-weight basis Kevlar* yarn is five times as strong as steel wire. It is interesting to note that a tensile strength of 120 dN/tex is theoretically possible for Kevlar*. This is the ideal tensile strength of perfectly orientated fibres with no structural or surface faults. Aramid fibres are relatively weak in compression (with a ductile failure mode) and this has to be taken into account when designing composites. The correct orientation of the fibre in the plastic or elastomer is important if required properties are to be developed. Lack of orientation will lead to ir.otropic properties. Chemically Kevlar* is unaffected by most elaatomeric and thermoplastic compounding materials. The unreactive nature of the PPD-T molecule means that chemical binding between the fibre and plastic or rubber is not easily achieved (some success has bttn achieved with surface-activated Kevlar* and ionomers such as Surlyn*). C14.3 C14.2 PAGE 3 PACE 2 There are various methods of obtaining a uniform dispersion: Available Forma 1. The fibre Bust be 'pre-opened' using a proprietary Kevlar* 29 and 49 is available in filament and roving fora. •ixer. The pulp is mechanically and electrostatically Kevlar* 29 is also available as staple fibre and pulp. The entangled and must be 'separated' so that a uniform fibre has a circular cross-section with a diameter of 11,9 • distribution and proper orientation can be achieved in 12.1 u. the elastomer to be reinforced. Kevlar* for reinforcement ef elastomers and thermoplastics. The addition of a mineral substance such as carbon black or talc helps the shearing action of the mixer The advantages of using Kevlar* for reinforcement of elastossrt and therefore, the opening of the pulp. Opening the and thermoplastics ara related to the unique properties of the pulp without the addition of carbon black or talc gives para-araaid, and also to the success achieved with therraosetting rise to a tremendous increase in volume; the mineral resins. Kevlar* filament yarn imparts added toughness, impact substance aids in collapsing the volume and makes the resistance and vibration damping to composites in many areas, product easier to handle. ranging from tennis racquets to boat hulls and tha monocoqut structures in Grand Prix racing cars. Kevlar* pulp and stapl* The elastomer is then added to the pre-opened fibre. are used as asbestos replacements in friction materials such a« While this method may be reasonably effective on a disc brake pads and clutch plates; and also gasket*. small scale whan a laboratory blender can be used, scaling up can be a problem. The mixers that are A. Elastomer reinforcement. purpose-designed for pre-opening Kevlar* pulp are very expansive and only worth buying if there is a definite Traditionally, carbon black has been used in the rubber industry commercial application. Furthermore, very careful as an effective reinforcing agent. However, the tensile control of the addition of pulp to elastomer has to be property improvements obtainable through higher and higher saintalned if consistent properties are to be obtained. loadings of carbon black are offset by increasing processing difficulties and deterioration of other properties, notably heat 2. It is far easier to ensure proper dispersion of the build up. short fibre if the "aastcrbatch" route is followed. This is not only so while potential commercial The use of short fibres in rubber is not new, but only recently applications are being looked at, but also for have short fibre forms been specially developed for rubber continuous production in many cases. reinforcement. The use of continuous filament yarn of Xevltr* for the reinforcement of elastomers is well established in Tha masterbatch has been developed by Du Pont to conveyor belting, hose and tyres. overcome the difficulties of getting proper mixing of the pulp - the biggest problem in processing. Kevlar* pulp consists of short random length . ~ t F — _..-»- *...•%.<*.• *wiiyt.M (iwii (nomina{nominall average fibre length of 2mm) with fibrils extending over the A typical masterbatch will contain around 44% Kevlar* entire surface . >utPulpr i»s useu.wdu in rcinrorcemenreinforcement of rubber pulp, 44% carbon black and 12% elastomer, though some because of its high length-to-diameter ratio and high surface preparations contain up to 60% Kevlar* by weight. area. This provides acceptable mechanical locking to the rubber Masterbatches are prepared either by solvent mixing or •atrix, especially under tension. Even better nechanical locking dry mixing depending on the elastomer and required pulp could be achieved with adhesive activation. This is a development to be enticlpatad. loading. A masterbatch must be defined. If you want to Kevlar* pulp of different nominal lengths is being experimented reinforce neoprene, a neoprene masterbatch must be with. Pulp dimensions and properties are being optimised for used. Masterbatches for most elastomers are now various end uses. From having started out almost as t available, but not yet for fluorocarbons. "Cinderella" product, Kevlar* pulp is now being precision produced. There is no real 'secret' to the preparation of a •asterbatch. If you ara going to do it properly you Processing will still nsed a proprietary mixer for effective pulp opening. The solvent mixing procedure is as follows: The blffest problem in processing is putting the fibre Into the elestoaer. Kevlar* pulp tends to clump, Raking unifors dispersion of the fibre in the elastomer very difficult. Once unifora dispersion has been achieved, then the orientation of the fibre becoaes relatively easy. The orientation of the fibre* in the elastomer is important, to take advantage of the properties of the Kevlar*. PAGE 4 PAGE 5 o Prepare a rubber cement by dissolving the desired elastoaer in solvent (typically toluene). Th« Applications ratio of the solvent to the elastomer is 4:1. Some examples cf commercialised applications using short Kevlar* o Pre-open the pulp in a high intensity mixer. fibre are gaskets, seals, v-belts and ablative liners for rockets. A specialised application, of interest to cyclists, is o Mix in the desired filler (typically carbon blacJi, the use of Kevlar* pulp to increase the abrasion resistance (and silica or talc) with the pulp. hence wear life) of brake blocks for racing cycles. o Add the rubber cement and mix. Potential applications include parts for oil well production, seals, wheels, rollers, guides, belts and protective/sacrificial o Evaporate the solvent. liners. Work is being done with Kevlar* pulp to reinforce the join areas in branched automotive hoses. Note: Fluoroelastomer nasterbatches cannot be prepared t>y this method due to their very good solvent resistance. B. Reinforcement of Thermoplastics, (Engineering and Fluorocarbon elastomers are made to final 5-10% thermoplastic elastomers). concentration without going via a masterbatch. From the foregoing, it is obvious that Kevlar* short fibres Dispersion of the aasterbatch in the rubber to be reinforced could greatly enhance the properties of thermoplastics. The is improved by increasing shear. This can be accomplish** prohibit, cf putting thp fibre Int" n suitnlilp fotm for oxtMirion with equipment and/or compounding technique*. or Injection moulding has now been overconip. o Equipment. in milling, a tight roll setting alonf Continuous fibres of Kevlar* are melt-coated with the with a high ratio of roll speed helps. A refintr thermoplastic required. The melt-coated fibres are then chopped or cracker mill is very effective. into pellets which can then be processed in the normal way, and without abrasion of the equipment. o Compounding. Shear is increased by increasing viscosity. if the option is available, use hl The benefits of reinforcing elastomeric materials with short Glass fibre, for example, provides improved strength, stiffness Kevlar* fibre include: and temperature capability, but it is severely abrasive. Fluoropolymers such as PTFE, are used as lubricants to reduce o improved aechanical properties (particularly at hlqo friction but soften the resin matrix at elevated temperatures. teaperatures) The superior capabilities of thermoplastic composites reinforced o increased cut, tear and penetration resistance with Kevlar* have been demonstatedin tests conducted with nylon 66, polyphenylene suplphide and Delrin*. Nylon 66 reinforced o significantly iaprovad wear characteristics with Kevlar* compared with unreinforced nylon has 50% greater tensile strength and three times notched impact strength. - all provided that the appropriate fibre orientation is ussd. Kevlar* also increases the heat deflection temperature of nylon from 88 C to 254 C at 264 psi (1,8 HPa) loading, thus increasing Typical levels of iaprovaaent are listed in Table 2. Actual the composite's service temperature capability (see Table 6). results with Meoprene CRT coaparing control (no fibre) wit* •Santoweb' DX (25 phr) and with Kevlar* pulp (15 phr) are shorn The wear resistance of nylon 66 reinforced with Kevlar* is 4 to in Tables 3,4 & 5. 8 times better than unreinforced nylon and 70% better than glass-reinforced nylon. The composite reinforced with Kevlar* Abrasion resistance is aost significantly iaprovad when th« is 40 times less abrasive than glass-reinforced nylon. (Table fibres are "on end" to the abrading force. C14.6 PAGE 7 PAGE 6 Testa on polyphenylene sulphide (PPS) show that reinforcing thU , CONCLUSION thermoplastic with Kevlar* produces a super wear-resistant ins ; non-abrasive composite. ; This paper has set out to show how the properties of Kevlar* ptra-aramid are being used to reinforce elastomers and A brittls polymer with excellent temperature capability 414 . ingineering plastics. The initial results with these new chaaical resistance, PPS is usually reinforced with glass flbr* i Mterials are very promising, giving impetus to further even for wear applications, despite the abrasive quality of , development. With such snhanced performance available, the glass. When Kavlar* replaces glass, the performance of PPS u potential for new applications is seemingly endless. We expect substantially upgraded. Its wear resistance is 18 tines better i the capabilities of reinforced elastomers and engineering than its glass reinforced counterpart and it is 278 time* }aaj plastics to be extended much further, based upon these abrasive!. (Table 8). ' favourable results. Tests on composites of Delrin* reinforced with Kevlar* ehov results even >ore impressive than nylon and PPS. Delrin* reinforced with Kevlar* has 50% greater tensile strength ens' four times notched impact strength when compared to the unreinforced resin. Kevlar* also increases the heat deflection ACKNOWLEDGEMENTS temperature from 101 c to 174 c at 2f-4 pal (l,n MPn) loading. The Author h»» drawn Informntlon from th« following »OUM-««I (Table 9). The wear resistance of Delrin* reinforced with Kevlar* is t*» Dr. George Pavlow )Textile Fibres, Du Pont de Nemours, times that of unreinforced Delrin* - already a preniua self-lubricating plastic. Hear rate of this new araiU Dr. Bernd Pulvermacher (International S A, Geneva, Switzerland composite is already approaching the practical limit possible Keith R. Watson )Kevlar* Special Products for a polymeric material. (Table 9). Adding Kevlar* to Hytrel* Andrew P. Foldi )E.I. Du Pont de Nemours i Co (Inc) (polyester elastomer) produces a no-break composite witi (Wilmington, Delaware, U.S.A. excellent wear-rate (400 times lower than the unreinforce* elastomer) making it excellent for heavy wear applications thet require bending around corners, hubs or other components. and various other publications on Kevlar*. Applications. Because nylon 66 composites were introduce* first, engineers have used these in more applications. Mew plates, for example, take advantage of the composite's tusk wear-resistance and low abrasion. The nylon composite is also being used in enclosure guide* fo» glass fireplace doors because of its high temperature capability. (Its ability to withstand high temperature alee makes the composite easier to machine). Lubricated composites of nylons are replacing metal *nt expensive synthetics in bushings, gears and bearings in *»nj TIM DONKIN high-temperature an'«l high-wear industrial applications. TEXTILE FIBRES DEPARTMENT One application for Hytrel* reinforced with Kevlar* is for the W PONT DE NEMOURS INT SA bristles of a large industrial sweeper. This composite is alee SOUTH AFRICAN BRANCH OrFICE used for the cover of a large diameter bearing. A large chela runs along this cover, causing equipment wear problems. Other synthetic materials including ultra-high molecular weight polyethylene and a fluoropolymer-based product were found to be unsatisfactory for this application. Potential applications for these reinforced polymers include equipment for textile processing, bottling and packaging, mining, printing, etc. • Du Font's raqistered trademark TABU 1 MECHANICAL PROPERTIES OF IMDCSTRIAL FIBRES ! Fibre _-- Density Tensile Strength Tensile Strength E-Modulus Elongation at (1/em ) (MPa) (dN/tex) (GPa) break (%) Kevlar* 29 1,44 2760 19,0 67 3,7 Kevlar* 49 1,45 2760 19,0 124 1,9 Nylon 66 1,14 990 8,6 5,6 18 Polyester 1,38 1150 8,2 13,4 14 Carbon Fibre 1,75 2650 15,6 240 1.0 E Glas» 2,54 1750 9,5 73 2,5 Steel Kir* 7,85 2600 3,3 200 2 i Tex - linear density 1 tax » lg/lOOOm z S o m I s in in in o at 5! n i § M s M I 5 n in w M I § e S ft m n1 o u If C14.10 TABLE 3 C14.ll TABLE 4 COMPARISON OF EFFECTS OF FIBRES ADDED TO NEOPRENE GRT COMPARISON OF EFFECTS OF FIBRES ADDED TO NEOPRENE GRT PHYSICAL PROPERTIES - Press cure 20 minutes at 160* C. PHYSICAL PROPERTIES - Pr«»s cure 20 alnutes at 160*C. •SANTOWEB' DX K£ VLAK* f U Jjf ». After 3 davs at 121*C <% change at 25* C) A. Original at 25* C 'SANTOWEB DX' KEVLAR* PULP CONTROL Machine Direction Machine Direction 8,4 10,8 1,0 M10 (MPa) 1,7 Q n 16,4 M10 M20 (MPa) O at 6,2 54 3 + 100 M100 (MPa) O|O 19,7 H20 38 18 + 98 17,2 M100 Tb (MPa) 11 fi 20 290 + 76 Eb (%) 77 Tb + 17 12 83 87 - 17 Hardness (Shora A) Eb Yield 0 - 47 Hardness + 6 5 + 8 (points change) CfftM Machine pftyction Cross Machine 0,9 Direction 1,3 1,8 M10 (MPa) 3,3 1,5 M20 (MPa) 2,2 M10 + 131 + 57 5,3 5,6 + 104 M100 (MPa) 19,2 M20 + 106 + 44 + 121 9,8 9,1 M100 Tb (MPa) 85 300 + 62 + 98 290 Tb 3 Eb (%) 83 88 78 + 14 - 13 Hardness (Shore A) Eb - 50 - 24 - 47 Hardness + 8 + 4 + 7 (points change) B. at 100* C nlrectlon >• After 7 davs at 121* C <% change at 25* c 6,4 0,1 M10 (MPa) 5,7 Machine Direction 5,5 10,8 1.1 M20 (MPa) 4,3 M100 (MPa) 9,i M10 + 167 6,8 11,2 M20 Tb (MPa) 25 225 + 175 Eb (%) 90 74 M10O 80 83 + 147 Hardness (Shora A) Tb +8 + 20 - 12 Eb - 85 - 25 - 60 Hardness + 10 + 5 + 12 Cf°" Machlna (points change) ntraetlon 0,7 cross Machine H10 (MPa) 0,8 1,1 Direction 1,3 1,9 1,3 M20 (MPa) J.« 3,1 H10 M100 (MPa) 10,0 + 105 + 88 + 137 4,6 5,1 M20 Tb (MPa) 85 ISO + 103 + 75 + 179 Xb (t) 215 M100 + 86 80 83 74 + 155 Hardness (Shora A) Tb +3 + 17 - 16 Eb - 64 - 47 - 62 Hardness + 9 1 + 4 + 11 •Santovab is a Monsanto proprietary product. (points change) C14.12 C14.13 TABLE 5 TABLE 6 COMPARISON OF EFFECTS OF FIBRES ADDED TO NEOPREHE CRT MECHANICAL PROPERTIES OF NYLON PHYSICAL PROPERTIES - Praas cura 20 minutes at 160* C UNREINFORCED 20% WT. KEVIAR* 49 'SANTOWEB' DX KEVLAR* PULP CONTROL 0.6mm PELLET K. DE MATTIft TISX " Original at 25* c 3/4" (19mm) atroke, Fibra Voluna (%) 16,2 piarced Kilocycles to 0,5" (12,7mm) growth 47 40 Tancila Strength (MPa) 82,1 125,5 1 Tensile Modulus (MPa) 4207 B. 11241 ABTM D1H04 I at 25 C Elongation (t) Rubber to Steel 60 2,3 )i k (dynamic) 0.46 0.2! 0.55 Flax Strength (MPa) 124,1 188,3 c. ABRASION RESISTANCE - Flax Modulus (MPa) NBS TEST 3310 ASTM D1630 6069 25*C Cut edge Machine Direction 134 218 272 IZOD - Notched (J/») 53 160 Cross Hachina Direction* 201 436 243 IZOD - Unnotchad (J/m) no break 480 * Simulates waar of aid* of v-belt on pullay faca. Hitt Daflaction Ta«p (*C) 66 pal (0,455 MPa) 220 264 pai (1,82 MPa) 263 88 254 C14.14 C14.15 TABLE 7 TABLE « WEAK DATA 1 HY.1/W 66 WEAR DATA : POLYPHENYLEHE Material Wear Factor Friction St««l washer Wear X Coefficient Height Loss Rate mterial wear Factor Friction steel Washer Wear K Coefficient Weight Loss Rate Nylon 66 917 0,435 0,2 22,93 Nylon 66 containing PPS containing 33% wt. glass 424 0,420 0,4 10,60 ! 40% wt. glass 4867 0,425 fibre fibre 500,8 121,68 Nylon 66 containing 20% wt. 6nm 239 0,390 <0,01 5,98 Kevlar* 49 : PPS containing . 20% wt. 6BD 270 Ktvlar* 0,349 1,8 6,75 Hot;a: For Table 7,6,9: -10 , UMITSi Wear Factor K : 10 in - Bin ft-lb-hr Weight Loss : ag - 5 Wear Rat* K.PV: 10 in/hr PV - 2500, P - 250 psl, V - 10 ft/»in Thrust washer test ASTM D3702-7I. C14.16 TABUS » MECHANICAL AND MEMt PROPERTIES OF REINFORCED DELRIN* Dalrin* 500 16% vt. 12,5M Kavlar* 49 In Dalrin* 500 Tanaila Stangth (MPa) 69,7 103,4 Tanaila Modulus (MPa) 2655 6690 Elongation to braak (%) 16,0 2,6 Flax Strength (MPa) 96,6 144,1 Flax Modulus (MPa) 2745 5393 XZOD - notchad (J/m) 81 303 IZOD - unnotchad (J/B) 1565 745 Haat Distortion tamp C 66 psi (0,455 MPa) 175 17$ 264 psi (l,!2MPa) 105 174 waar Factor 141 14,7 Friction Coafficiant 0.247 0.169 THE PROBLEMS ASSOCIATED WITH RUBBERS. AND PLASTICS IN MINING CABLES T PAGE - CONSULTING ENGINEER, RAND MINES LTD C15.3 lHTIQDUCTlOW The cablea which are of moat concern to aining lnduatry electrical > engineer* ere those which take power, usually at 500 to 1000 volte, to Che The alnlnf boom In South Africa during the second half of th< nineteenth stops fsce In hard rock mines, snd to mobile machinery In coal mines, and century relied heavily on the readily available cheap labour. From this to a leaaer extent gold mines. baae the aechanlaatlon of South African Mining proceeded at a alower pace than In most flrat world countrlea. Within the last 15 yeara the squeeze on proflte and advent of high output The former are ueually relatively stiff, steel wire araoured cablea, •lnee ha* reaulted In a rapid movement toward levela of mechanisation generally ualng PVC aa an lnsulant with PVC shesthlng, and are covered by equivalent to that in moat other countriea. SABS apeclficetion ISO. Refer to Figure 1. Many mechanised systems uaed In South Africa have been baaed on systems The cablea feeding mobile machinery are required to be flexible and are aatlafaetorlly saployed elaewhere. However, Insufficient attention waa thue unaraaured. The cables can uae a variety of lnmilants and sheath often focused on the local condltlona under which equipment was to be material!. For electrlcel protection reasons the Insulated conductors in operated. Subsequently, the shortcoaings in much of the production tbeae cablea are ueually covered with croasbralded copper or copper snd equipment ha* been eliminated through re-engineering. However, the eupport nylon screening. Theee cables are referred to ae trailing cable*. Refer equipment, one of which la electric cabling, haa not had the aaae attention to Figure 2. and can and doea lead to production lo»», Increases In operating coata, and possibly health or life haxards. In surface mining application, similar cables but usually for operation at higher voltagee, namely 2200 and 6600 volts, are uaed to feed large mining This paper concentrates on the aubject leaat understood by electrical machines. Since soae requirements for these cables differ from thoae engineer* and currently requiring most attention In order to overcoat soae above, they will be referred to as portable cables. of the problems. Other cablea for epeclallsed applications such ss telemetry and telephone CABLE TYPES cebles, extrs high voltsge and high teapersture cablea are also used in mining, but owing to the epeciallsed nsture of these cables, will not be Polymers are uaed In the aanufacture of aost power and communication i discussed in this paper. cable*. Cablaa utilising oil Impregnated paper aa an Insulation material are considered to be obsolete but are still widely used. i Thla paper will deal with the araoured PVC type cable and trailing and | portable cablea. Cross linked polyethylene insulated csbles, and to a leaser extent PVC lnsulstsd cables, are commonly used in mines for the reticulation of power at voltagae of 2200 volt* to 33000 volt*. These major reticulation cables are Invariably carefully installed, and protected, and with the exception of cablae Installed in shafta ar* not prone to being damaged. Ulb.4 THE SOUTH AFR1CAH TRAILING AMD PORTABLE CABLE INDUSTRY Tltlfi WAN tl I M«i|i|>«i lut ltiK l.t I lit* *»Kl"*'*'tH 1" til* nltilng indtiHlty who have a Until eh* aid fifties. South African coal Billing consisted largely of vested interest In the local cable manufacturing Industry being a viable and strong lnduatry. •mall, fairly labour Intensive alnes. Mints producing coal for the local market wart a poor Investment, owing to th* low local price*. SOB* aln« war* d*v*lop*d to £««d power ststions, and were at that etagc th* "ore Local manufacturer? have suaequently moved In the name direction as the aechsnised aln*e. oversees manufacturer**, but still tend to lag behind. SOB* opencast alnea had been developed which aade uet of trailing or ARMOURED PVC CABLES portable cables. Fires c*u*ed largely by damaged cables, have concerned the mining industry The last 30 years hss seen major aechanlsed alnlng developments resulting for over a decade. In this regard attention was focussed on matters of n froa better export prospects, for coal In particular, the devclopaent and nechanlcal or electrical nature, rather than on the PVC compounds used for construction of large power station* requiring high output sines, as well this type of cable. aa a boom In th* coppti, uranium and cement market*. Ultliln the last decade, the lgnitahlIIty. flame retnrdency nnd lombuntlnn Th* local cable manufacturer* were faced with a sudden increaee In demand gaa toxiclty of PVC started to receive attention. The recent tragic for trailing and portable cablee, soaa of which were larger than sny polyurethane foam fire, although not related to nlertrlcal tints, brought previously manufactured in South Africa. the question of compound combustion performance to the fore front. A fairly significant amount of cabl* was Imported In the early booa years. Considerable work has been done on the aspects of flame or fire retardency, This was followed by an lncreaae In Interest from overaeas manufacturer* but considerations particular to the mining industry will be expanded upon later. and local Importers. Subssquently a downturn In mining activity elsewhere In th* world led to substsntlal dumping of iaported cable. TRAILING AND PORTABLE CABLES The local manufacturer* who had gssrad up to aeet the locsl deaand, wert suddenly faced with an ovcrsupply situation and war* forced to meet th> Trailing cables have traditionally been specified to comply with the resulting low*r prices. Som* of th* Imported cables were poor quality British Standards and British National "oal Board «perlflcatlona. However, products and wars offered *t ridiculously low price*. the machinery used in South Africa and the levels ol skill and "feel for a aachlne" of the local operators, remilts In Smith African enndItImin being Soa* C< th* larger manufacturers were, at that stags, strongly considering sore ar 'uous than those In the UK. whether or not to continue to manufacture trailing and portable cables. The laproved trailing cable performance whlcli the mining industry required At about th* saas tlas, ths alnlng Industry rsallssd thst csbl* life in vould be achieved by Improvements to the compounds used for lnsulsting and South African mines was usually substsntlslly 1*** thsn that sxpsctcd In ihesthlng purposes. Some advances have been made In this regard, although other countries, and engineers In the Industry startsd to look foi the problems faced by the user In Identifying the most Important compt. .nd Improvements In th* product In order to cops with South Afrlcsn conditions. characteristic* snd shaping developments, require further discussion. Unfortunstsly th* local manufacturer* did not recogni** th* opportunities presented by the situation, snd It was lergely left to som* of th* aor* reputable overseas manufactured to start developing better cables aore suited to the local requirement*. - 5 - CIS.6 - 6 - C15.7 It It not unreasonable to have expected the local manufacturers to lead the In the preaence of the high air velocities caused by the ventilntlnn way alnce they «r« cloacr to, and should be more aware of the needa, of the system, the propogatlon of the fir* la rapid, nna the presence of other market place. In addition the local manufacturers entire production la for cables as well as plastic piping and other plastic materials, run lend to local consumption, whereas the South African market forms a small toxic gas, carbon dioxide, carbon monoxide and smoke lit Ins evolved. Then* proportion of the European manufacturer's output. producta of combustion are then carried directly Into the working place by the ventilation air. In contrast with trailing cable, portable cables were Initially designed to comply with the American IPCEA and NEMA specifications. As with trailing Since one of the two possible escape ways la now blocked by the fire, to cables. South African conditions are in many respects more srduous than eacape the heat and fumea workera have to travel with the air and those in North America. This was clearly reflected in the relatively poor combustion products for appreciable distances before fresh air can be performance of the American style cables. In other respects, some North reached. Smoke can rapidly reduce visibility to rero in an area lit only American requirements such ss the requirements for compounds to perform by the worker's cap lamps. Furthermore since ventilation air Invariably satisfactorily at temperatures of down to -SO'C. were more arduous than ventilates large areas before being drsvn into return slrvaya, many workers local requirements, and in the case ot low temperature operation, of no tan be exposed to the gss snd smoke, snd a large number of fatalltim can consequence in South Africa. result. Once again, the majority of the cable shortcomings could be corrected by The lack of rapid escape routes means that relatively innocuous gases with correct selection of the compounds used for cable manufacture. ansesthetlc properties can lead to unconclousness and subsequent death through heat or oxygen starvation. Highly toxtc RaRes such aa hydrocyanic HUE HETARDEMCV acid gss can naturally lead to rapid death and the length of exposure to the gss In the case of mine fires results In gases such as hydrochloric Conern over the behaviour and properties of polymers when subjected to acid gas causing sufficient lung damage to cause fatal results. flame, Is not new, nor unique to South Africa. There are two requirements that have resulted from the fire hazards However fires in mines, particularly in deep level hard rock mining, associated with electric cablea, namely, to reduce the potential for the preaent unique problems for which solutions hsve still to be found. cable compounds to transmit flame from one timber pack to another, snd tn reduce toxic gas and satoke emission. Some of the flame retardanta used Csbles are usually instilled in the travelling waya leading to the stoping with halogenated compound* reault In high smoke emission, snd tn some cases areas. The travailing waya are usually the main ventilation routes to the in Increase in toxic gas emission. working placsa. Cables in travelling ways and entering stopes are often suspended from the timber support packs. Addlt'onal disadvantage* are « deterioration in mechanical snd electrical properties and increased prices. fires are therefore oftsn caused by cables being pinched by the timber packs. If not properly supported away from the tlaber. In the abssnee oi An Important aspect of fir* cauaed b> an electrical fault, la that failure of the electrical protection, the fault resulting from the pinching utremely high levels of energy are released at the fault. A fault on an of the cable can ignite the cable or the timber or both. Ilkv cable can f\tf energy at the rat* of 3,5 xlO kilojoulea/sec, vheress a 550 volt fault can produce 2.5 x 10 kllojoulas/sec. - 7 - cis.a C15.9 The This quantity of energy la aufflclent to vapourlae a substantial amount of crushing forces that can be exerted on cables by timber packs are BO copper within tht 100 to 500 milliseconds It should take to clear the high that it is impostble to formulate compounds capable of withstanding fault, and this vapourlstd copper provides the electrical psth which them. auatalna the fault. Portable and trailing cables require other mechanical properties resulting It therefore follows that no presently used compounds or flreflghtlng from the different duty for which these cables are used. chemicals ere capable of preventing Ignition or severe thermal degradation of aatarial In the immediate vicinity of the fault. What Is required of Firstly the compounds used for the insulation and sheathing of cabJes must the cabla compounds la that they should self-extinguish once the source of remain flexible within the range of ambient temperatures which can arise. heat haa been removed. In South Africa this is a relatively insignificant problem. As obvloua as this might appear to some, the fire rctardency of cable The conditions under which portable cables are used In South Africa differ compound and the efficiency of automatic flrefighting equipment was severly considerably from those in North America, mainly due to the fact that the criticised after a fairly major fire was caused by an electrical fault cables are dragged or laid nn sharp broken flnnHflfnne niu) nha lcn. Th» whlrh continued fur Hume 20 minute*. : flbrAn Inn, i mt anil nil t CM 1 »l *nit prupr i i I I-H nl t he rihciit h nitttei in I IN therefore ol importance. Present teat procedures for flame retardency tend to focus on the chimney effect common to fires in high rise building cable ducts. Situations which Long lengths of cable weighing up to 12 Connor, are sometimes dragged by could create chimney effects in mining are almost non-existent. It la , powerful bulldozers or tractors using wire rope slings. Thus good tensile therefore wise to test flame retardency under conditions which are more j strength properties are required. typical of mine conditions. Other requirements of the sheath compounds are good visibility against dark At th* risk of being criticised on what is presently a very emotive backgrounds and UV and hydrolysis resistance, whereas the insulting subject, I consider flame retardency of cables to be of less significance, compounds should be as crush resistant as possible and, due to their use at and smoke and toxic gas emission to be a higher priority, than In the case higher voltage than the other cables, should have good electrical for cables used In surface Installations. In the light of the above, It properties. should therefore be easier to develop the tough compounds demanded by the arduous mining applications. Clossr attention to Installation techniques Underground trailing cable sheath compounds require similar abrasion, tear and electrical principles will further reduce fire hazards. and cut resistant properties to portab le rablpn, but I)IP tens! 1* strength requirements are lower. 1TV resistance IN not essential, whereas hydrolysis HEOMMCAI. PIOfMTIES resistance is. It would be highly desirable to have a compound which is clearly visible, particularly when used on conl mines. However the Fixed type cablas suffer predominantly from Impact and cruahlng damaga. tendency for sheath compounds to become coated with fine coal within a lbs main requirement In this respect la that the compound uaed for short period, makes cable visibility a doubtful requirement. Insulation should exhibit elastic propertlea. Cabla dealgn techniquaa also play a part In Improving Impact realatance of cablas. Trailing cables used on machines with reeling devices, where the cable le being repeatedly flexed, should have Insulating compounds which are resistant td penetration by broken copper screen wires. In addition to the - 9 - - 10 - C15.10 C15.ll of meeting these ELECTRICAL PROPERTIES normal electrical properties. The cosmon nethod requirements is to use an inner compound with good electrical properties. together vith an outer compound having the required mechanical properties. The primary requirement of the compounds used to cover conductors, is the electrical insulation and ozone resistant properties of the compound. The better the insulation properties, the thinner the layer of compound With *11 insulating compounds It 1& desirable to be able to colour the required to effectively prevent current from flowing between conductors, compound to assist with cable core identification. and therefore the overall cable dimensions, and possibly price, can be reduced. Recently* problems have been noted resulting from severe corrosion of the copper in cables. Following fairly extensive investigations, the rust The ozone resistant properties of a polymer are of more interest in cables coloured corrosion product was found to be fine copper, and the reason for for use at higher voltages, where corona discharge can occur. Corona the corrosion was traced to microporo&ity in the tinning layet on the discharge causes the formation of ozone from atmospheric oxygen, and can copper wires. lead to rapid deterioration of an unsuitable insulating compound. It would appear that modern methods of tinning and drawing copper wires result in much thinner layers of tinning, but also In increased porosity This phenomenon occurs predominantly where the insulation has been removed and discontinuities in the layer. The major reason for tinning of copper to allow for terminating of the cable. However, air bubbles or inclusions in the Insulation can be ionised by high electric fields on high voltage wires is to protect the copper against corrosion from sulphur used as « cables, and the material surrounding these air pockets can deteriorate vulcanising agent. It is therefore desirable to use compounds with which gradually due to ozone attack. The deterioration of the compound leads to vulcanising agents other than sulphur can be used, allowing cable higher levels of lonisatlon, and thus the process, once started, proceeds manufacturers to use bare copper wire for the conductors. at an accelerating rate until the Insulation finally fails. A weak link in portable cables is the failure of the relatively weak pilot core when the cable is subjected to tension. One manufacturer attempted to To minimise this process, semiconducting layers are usually incorporated In the Inner end outer layers of the insulation of cables used at higher overcome the problem by using a soft, compressible butadiene cradle to voltages in order to achieve a uniform electrical field around the support the pilot cores. In theory the pilot cores would compress the conductor, and voids or impurities are avoided as far as possible. cradle when under tension, thus reducing the helix diameter and allowing effective stretch in the pilot cores. Two effective insulat inR polymers are CT«HB-IInk^H pnlyrthy1*np, known to Another manufacturer used pnlypropnlsn* film, wrapped Into cord form as A elect r leu I mil Kn#» t H nt* Xl.l'K , mitt rt lir lynr piiijiy 1 I'IIH I tthltrt , "t M'M, lintti of which hav#> flutlstactory Insulating and ozone reistant properties. filler and cradle. It was thought that this relatively Incompressible cradle would result in early failure of the pilot cores. Unfortunately neither compound has ideal mechanical properties when used as •n ittsulant In trailing cables. XLPE tends to be too stiff and EPM has However, tensile testa carried out on the two cable designs yielded poor mechanical strength. Both compounds are used as insulants for considerably better results with the latter designed. Investigations portable cables, whereas EFM Is used almost exclusively ss th* Insulant for revealed that the polypropolene cords acted aa tendons, which by taking trailing cables. tension, effectively protected the pilot cores. Thla rather accidental result lndicatea that further consideration of this matter could further improve the cable performance. - 11 - C15.12 C15.13 The use of EPM AH « trailing cable Insulant result* In poor Impact or crush However, th* European lnws governing the use of vKrrrlr |> I However, the electrical resistance of the elastomer screen is considerably In the South African context the lack of a mining cable specification j higher than that of a copper screen, and this could lead to electrocution, allows manufacturers to use electrical grade EPM without any measures being •ethane explosions caused by flashing If the cable is partially cut, or taken to Improve the mechanical properties of the compound. The difficulty failure of electrical protection. European manufacturers have tended to in the user readily distinguishing between EPH or EFM/CSM insulation, premote the use of this type of screen without fully appreciating the provides an opportunity for unethical exploitation by manufacturers or dangers resulting from the different systems in uae. Importers of cable. A further disadvantage of the elastomer screen is the gradual deterioration This means of exploitation is presently difficult to counter and puts the I in the conductivity of the screen associated with carbon migration in the ethical manufacturers at a disadvantage. In our experience, many of the j matrix. smaller cable distributors are unsure of the polymers used in the cable manufacture, and In some cases, even the Identity of the manufacturer or i the country of origin of the cable. For this reason we have been | Elastomeric screening, on the other hand, can be applied during th? normal encouraging the manufacturers to use embossing of the outer cable sheath ai | insulation application stage of manufacture, and does not require the use a means of ready identification, which will to a large degree eliminate the { of the fairly complicated screen braiding machines. sub-standard cable in the local market-place. Elaatomeric screening would undoubtedly be a boon to cable manufacturers and users If the resistance could be reduced to values similar to the Finally, South Africa's mining Industry has a need for cables with superior copper screening and the problem of conductivity degradation could be Insulation mechanical properties as well an tough outer sheaths. If local overcome. manufacturers could produce such cables, the Inferior Imported cable would gradually disappear from the scene. Attention to the particular requirements in the South African context could beer fruit. It might be argued chat the R and 0 budgets of the European CONDUCTIVE ELASTOHERS manufacturers and easier sccess to the raw material suppliers puts them in a better position to schieve this goal. However, the fact that the Conductive elastomer!, which arc essentially carbon filled compounds, ar« conducting polymers which are In use in Europe slready meet the being used as an outer core screen in place of the more traditional copper requirements of European mining law. or coppsr/nylon braided screens. The conductive elastomerlc scrssn haa largely replaced metallic scrsana in Europe. C15.14 C15.15 Local development* to Met local requirement* are therefore needed. Oth*r gulden (3)» (A) rate the properties of both compounds as good. Other Manufacturers have rated EVA (ethyl-rlnyl acetate) and nltrlle-butadlene as having superior mechanical properties to CR or CSM. but the elastomer guide POLYHERS, COMPOUNDS AND THE ELECTRICAL ENGINEER mentioned above tends to refute this statement as far an Nitrlie-butadiene From a cable point of view, the South African mining Industry is serviced ia concerned. However, a number of manufacturers have stated that to achieve a tensile strength of 15 N/mrn and 10 N/mm respectively, it is locally as well as from Germany, Britain, Spain, Italy, Taiwan, Japan and essential to use CSM rather than CR. Korea. In addition some cables of unknown origin are encountered. The marketing of cables is done by companies varying fron manufacturers, It sight be said that users do not need to become involved in selecting the with a varying, but reasonably high level, of technical competence, to some compounds In use, but since some suppliers offer a variety of compounds• with the compounds offering better characteristics being more expensive, it wholesalers who have no knowledge of the products. is possible for a supplier to substitute the more expensive compounds with cheaper compounds In order to Increase profit margins. The engineer, on the otherhand, is usually encouraged to purchase the cheapest product, provided it meets the specification, if available. Whether or not the supply of cables with the wrong materials Is through South Africa ha* no specification covering mining type trailing and malicious intent, genuine error or Ignorance, it Is a fact that this portable cables, and British or other foreign specifications were often occurs. Apart from the cost Implications, involved, the results of field trials may totally misguide a user into condemning wrongly identified used. The larger mining houses have now produced their own specifications compounds as not being suitable for the application. This in turn to overcome the problems which arise through the use of foreign lengthens the time span before meaningful results can be obtained from the specifications. field trials. However, to purchasers of cable, these speciflcatlons have not solved the problems of the site engineer or buyer. If the specification called for a It Is therefore difficult, but necessary, for an electrical engineer to polychloroprene sheath, did It mean that CR, PCP and Neoprene aheatha were h«V« the compound* verified. Nine* f.«w it Any Imvr t lie know I iMg** to do HO. unacceptable? If the supplier said that Hypalon was the best compound for A uniform method of naming of compounds and uniform use of abbreviations would undoubtedly be of some assistance. a sheath, did that rule out CSM or CR or CSP or CSPE or chloroprene? If the specification required an EPM/CSM insulated conductor, why did the It would appear that in the long run, a plastics chemist is best qualified manufacturer offer EPR/CSP exactly in accordance with the specifications? to purchaae trailing cables, since the electrical characteristics are more caul ly quant If led and a««e fined. Some auppllera claim that a material other than black In colour cannot be polychloroprene, while others offer polychloroprene In a variety of SPECIFICATIONS AMD TESTING OF ELASTOMERS colour*. An elastomer guide (Z) quotca the maximum tenalle strength of CR aa 20,5 The problems being experienced by uaers, apart from those associated with N/mm and that of CSM aa 17,5 N/mm , and quotca tear atrangth aa halng application, are flratly, which characteristic* of the compounds will excellent and fair raapectively. produce the dealred performance, and aecondly, what test methods yield reaulta which beat duplicate field conditions. - 15 - C15.16 - 16 - Cla.17 SABS 168 specifies the test methods to be used for tensile and tear Apart from the above, cables manufactured Co the same specification, but strength testing of elastomers, with and without aging. The Uest German utilising two slightly different polyurethane based compounds, also specification VPE 0472 Includes tests for tenacity and abrasion resistance. exhibited vastly different aging characteristics in use. In one cane the compound hardened and cracked severely within two years, whereas the other The results of the German tenacity tests are claimed to correlate with SABS compound appeared unaffected, apart from a thin surface layer, after li tear strength test results, although the methods and units are dissimilar. years. The results of the advanced aging testa had not highlighted any expected difference in performance. The SABS tear strength method yields results with a fairly large degree of scatter, reportedly due to difficulties in preparation of the test sample. Doubt is expressed In soae quarters as to the usefullness of abrasion testing to the VDE specification. Research has shown (1) that the wear rate of plastic conpounds varied with test procedure and temperature. Slur* Mi* V»K 't**rtl Method will result In varying dugrvnn of MlmllnK of the abrasive surface* as well as increases in temperature at the test specimen '"tain performance criteria. Such contact area depending on the polymer being tested, these doubts are well founded. How then does a user, when confronted with a produce which can be manufactured using a variety of compounds and exhibiting an even wider spread of characteristics, decide on the sultablility of the product in the . The ability to be able to select the correct compound for an application first instance, and the economic Implications of using materials with I depends on a better understanding of the influence of test results on che superior test characteristics but higher price. In the second Instance? performance criteria ol a compound. The obvious answer would appear to be that the proof of the pudding is In It is likely that too re materials engineering 1B involved in selecting the eating and that field trials will provide the answer. However, one compounds for use in. nay, wear resistant linings or bearing materials than batch of cables supplied from a single production run could give results with selecting cable sheathing compounds. Furthermore most other where the nlnigua to maximum life of the cables varies by as much as a industrial plastics appl lea t ions are poBsibly con f tried to fewer suppi iers factor of 6 to 8. In order to evaluate field trials, a very large sample, of a more specialised nature than is the cane with rabies. and years of careful documentation, is required. In aany cases the application considerations are fewer than for cables, Furthermore test results do not necessarily indicate the expected which require electrical and fire resistant properties and are subject to performance of a compound. As an example, polyurethane was used as a crushing, ripping* cutting and abrasion in dry and wet conditions, and with (beaching material for portable cables, and exhibited similar tensile, tear ozone and ultraviolet resistant propertied required periodically. and abrasion characteristics Co those of the elastomerlc conpounds in use at the tim*. However In practice, the sharp rock over which che cable was The application of plastic polyner knowhow to cable manufacture is a pulled was found to cause deep cuts and gouges In polyurethane, which was relatively Insignificant portion of the total field. However since cables not the ease with CR and CSM compounds. It must therefore be concluded fora the unbillcai cord to each Mining nachine• their performance has an that the teat results failed to highlight a shortcoming in an essential Important bearing on Maintaining productivity and reducing costs. sheathing compound characteristic. - 18 - C15.18 C15.19 Any «£fort to remove confusion and improve on cable compounds will be of CONCLUSION great benefit to the nodern mechanised mines» and greater co-operation and closer co-ordination between the plftHtir-H chemists a»U the uners 1B < Any Improvement In the performance of cables uaed in the mining industry necessary to achieve this result. will result in increased productivity and safety. Cables are currently being supplied with CSM sheath compounds with an i These improvements can only be achieved by Improving the performance of the unaged tensile strength of 16 to 18 N/'nm and tear strength of approxi- i polymers used for sheathing and insulating of cables. The need for such mately 10 N/ssi. CR sheaths with a tensile strength of 13 to U N/tum and I improvements results largely from particular South African mining condi- tear strength of 8 N/nm are also in use. | tions. I These cables are demonstrably better than previous cables with tensile and • A better understanding of convent Innn 1 t *-Ht rrnnlln or i\ 1 ti'innt i vr I y, tear strengths of 7,5 N/wn and b UJtm respectively. However, problem* formulation uf new tent procedures, is required. associated with hot vulcanising sheath repairs are being reported with son* of the compounds. This rather unexpected problem requires further ; South African standard specifications for trai1 ing and portnble rnbles for attention. use In mining are long overdue. Finally, the politco-economic threats to the country make a viable cable industry a necessity, and the availability of cable of the neceneary standards will benefit both the manufacturers and the users. - 19 - C15.20 C15.gl REFERENCES PVC QUTE8. SHF.MH STEEL WI1E U mction and Wear t«t.o£Poly«ra - K fcl*r, an, G Wickstro» P'J(. Paper pr.aented to the Nordic Syaposlum on Trlbology PVC IN'iQLM'ICN I. An ...y .old. to Poly-er. - Industrial World - August 1976 3. Poly-r. u.ed for Trailing Cables - Source unknown COPPEB. OE ALL^MIMIOM 4. "Flexit" Trailing Cables - OEC Cables Mfa.l - COHST8LUCT1ON OF PVC STEEL WltE A.tM0lil6D CA6LE SHEATH- CZ.CSM COPPE2. /NYLCN 4C2.EEN MiTEi HEDDiNfc -SOFT IUBME. itMl CCNRUC.TINC LAfES. U POLVPtOPVLtNE PM O. IHMEf. iEMI COPPE! CCNDCtTCH • P0WE1 CQt£ PILOT COB.E ! NtfL lEbDINC Ol CiAOLE - SCfT -I Fib £ - CONSTtliCTlON OP A POtTAiLE Oa TBLAlUNb CAbLE C 16.1 KIKTH NATIONAL CONFERENCE OF THE SOUTH AFRICA}! SECTIOIi OF THE PLASTICS AtlD RDB3CT INSTITUTE 22 - 2? OCTOBM 1987 "rMWIllll.TlNli I'VC IXMI-HWIUS roil KXIUVilVK ilAHIIUWli APEAK AHII HIGH TECH BKyiHOTIHEPTS' by LES BLOOH KBSI(SA) SUMMARY Work on the development of conductive TVC wan initintert during the late eeventien when it became apparent that the conductive footwear used In explosive areas wan, in fact, not conductive after a short period of wear. This p»per reviews work carried out at ABCT's Plastics Technical Service Laboratory to develop a fully conductive solinir nnterial thnt would last the practical life of the shoe. At that time all imported and locally produced conductive foot*ear were based on a vulcanised conductive rubber soling aaterial. Within weeks they bacaae antistatic, and after 3-4 •onths insulating. This paper discusses the requirements for conductivity j and specifically the additives and rrocesRin* technology developed to sake j plasticised FVC a conductive aaterial. The knowledge gained fro» these i atudies has also been evaluated in other potential nni-licationn, none of •. "hick have been comercially exploited. IKmODPCTION Tbe build-up and discharge of electric potential has been a problea world- j »id« for »any years. There are Bany industrial, explosives, and defence ' situations in which the unfortunate combination of electrostatic charge and i infalaaaUe dusts or gases oan occur. There is no world specification i covering the requireaenta for antistatic and conducting footwear but the j British Standard 2050 (1978) oan be taken as a guide. For conducting I footwear a aaxiaua resistance of 1,5 x 10^ oha is required. For antistatic ] footwear a alniaua resistance of 5 x 10* o'na with a uaxiaua resistance af ! S i 107 oha is apeclfled. C 16.3 C 16.2 - i - - 2 - TO TEST METHOD FOR KEASURIWC THE OONUDCTIVITI OF FOOTWEAR AKP PLOORINS "i» Sritiah Standard test can ee slaply and effectively inprored by using standard S7>S9 electrodes (2,5 z 2,5 cu) to contact the sole and inner under dry conditions rOOTWEAK isd stadard pressure* This is aehiered by using the sprint loaded tongs as shown la the D*xt slide. The equipment can alao >a used for flooring* The electrodes coHnjcrmo - MAX KESISTAHCK 1,5 X 105 oh« irt connected to a standard Begohaaeter operating at 900 T as currently specified. AHTISTATIC - HAX KBSISTABCB 5 x 10^ oha 'Us piece of eulpaent is an entirely South African development and details can »e - HI" SKSISTAH08 5 x 10 oha :kt>ined froa the author. no Unfortunately, the teat aethod specified gives irreproducitle results in practise. The test has >een criticised aa not representing conditions in actual service an Fig 4. AECI *est equipment for conductivity. British Betted for Measuring conductivity. Hg 5. AICI test equipment being used on footwear. Tig 6. A surface test eqipaent for aeasuring conductivity. C 16. b Fie 6. Screw design plays ar - 4 - iaportant part In even dispersion of the conducting earbor black in the compo?i* OOHPOTOP or oomwcTDis pvc athough we covered conductive additivee eueh M conductive flkr.i, aluminium flak* and metal du«t», we concentrated our efforta oa the use of conductive carboa ttaeka. Special gradae of carbon black may Vo incorporated Into WO to make It oondueting. However, it la more difficult to obtaim good conductivity in pleetieiaed WC particularly at the oof tnooo l«rol« required for .oliag. Again a» conductive carbon Mack io addad to a plaotieiaad ITC, ttao ooapounds will have inferior mectaical propartiao and thoir water vapour psraeability la eoneiderably higher. In practice, w* have found that high loadings of oarbon Mack ara required In eoling compounds to make it fully conducting, ia a coapound having a maximum raaiatanea of 1,5 x 10? oha. 1 Such co«pounda ha»a poor tanaUa atrangth and alon«a*ion •* te** ' •»* »•** Fig 7. The importance of unir eauaa cracking aftor a short jwriod of «aar. Partlda alia aad poraaity the right screen pack on conductivity. of carton black ara all important and tht processing prooadura alao playe aa iaportant part In producing the right ooapoun*. To overcoae IOM of the poor phyileal propertiea of carken filled WC coBpounda, «e have found that eaall additiona of a tar-poly»r of ethylene Tinyl acetate aaaiata the com- pounding of auch aaterlal and at the sane tiaa producea higher tanelle and elongation at iraak propertiee. Conducting plasticlaod tVC ooapounde cannot to Injection moulded under normal condltione ana require a ».. •odificatlona iPTUCATIONS to the equipment In order to retain ita conductivity. Interruption of the WOTWSAK flow path of the conducting PVC can reduce the conductivity even to that of a non-conducting compound. Screw deaign alao playe an important part and A great deal of confusion continues to dominate the footwear Industry aaallow acre* flight* ara daairaala to obtain good conductivity. Shear interpretation of conducting and anti-»tatie footwear. Conducting mat be kept to a minimum and the carbon partldea within the blend auat be footwear aade worldwide has not been aatisfactory and those which can be in contact with each other by being In doae proximity to the carbon chain. u»ed with some degree of s.f.t, are awkard. They contain conducting .trips The u»e of special plaotlcleare and atabllisera alao enhance the conductivity »hlch are affixed to the inside of the ahoe or boot and are attached to th* of the bland. Conductive JVC may also bo crow-linked by gamma irradlatloa •nkle of the wearer. »„,,„ conducting footwear has not met the re- to give Improved physical propertiee and reaiatanoo to chemical attack. UnlUt qulrB..nta for conducting footwear In aa much as they lose their conductivity other polymers, TYO needs aisletanoe in that the Irradiation energy required •Ith a relatively short ap.ee of tlae through flexing which br.aks up th* for orosa-llnkimg la greater and thus,a* a ooneequenee, oaa be very harmful te 1 conducting flow path. Conducting rubber soling is extremely conductive for the FTO itself. It la therefore naoeaaary to include a croee-linkable th. first few week, of war and r.pidly beeoaa anti.tatic and within aonth. aweMr whioh la typleally aa alljl aerylate such as trimethylol propane Ululating. Many serloua accident, have occured due to this phenomena with trlaethaerylata (TWT). T«ry aiaply, the eroaa-1 Inking •onoaer, under conducting rubber aoling which we. not appreciated for many yeara. A new Irradiation, polyaerleis aad forma a •network* with the oarboa particle* whisk tfpa of aoling mad. fro. conducting rVC has been tested In th* field for six reatrlets the movement of the rTC polymer chains. •.•Mrs and la the «ub>ct of petmt.. It involve . two «tar C 16.6 C 16.7 - 7 - _ b - flOW IDS loulding proom using special metal Insert! which arc placed Into th* eole Th* »uild-up and discharge* of alectrlc potential on plastics components can lould prior to th* injection moulding prooesa. It ha* *»n *howm that caus* ciplosionx, start fires and can »<• damaging to interpreted electrical luch oonductiv* footwear retain* it* oonductiYity for th* practical llfatl*.* circuit!. Plastic component* can carry electrostatic potentials as hlg» »f th* soot or *ho* and hav* now eeeom* th* eitattlshed footwear for u»* la u 55 000 volt* and lntergrated circuit* can •• damage! vlth electroatatlc •xplodv* handling area* and allied wtabllshments in South Africa. discharge potential* of 5 000 volt*. To aaf*fuard against *l*ctrostatio din- ebarg*, conductlv* *VC floor tile* are layed around sensltlre computer equipment and adequately grounded to earth. These floor tiles are manufactured locally from th* earn* conducting PVC compound used for the soling of conducting footwear. The manufacture of these tile* la carried out under strict moulding conditions to ensure full conductivity to Met specifications. CON HOCTnp . MAX KBSISTANCS S I 104 ohmj ANTISTATIC . MX RESISTANCE 10B ohm Tig 9. In* fir»t *tag* of - MSI RESISTANCE 5 z 10* ohm Fif B. Th* AIM pat*nt*d proeeM injection Boulding. for th* aanufactur* of conducting foot»**r. riff 1?. Conducting flooring •ad* *7 Codaata nastloa CPty) ltd »i« 10. Tbf oo«pl*t*4 conducting *ho* "" * .uufacW.4 »T 1]nit.«-rr.« rootw*ar «aottfactur*r* l?ty) Ltd. Fig 13 Tasting conducting flooring C 16.9 - 8 - HPICAl AMD SLIHMIHS ?AM On* oeapany baa evitchad over froa ualac aatal body pada to conducting PVC ca BATTBIT eo?:meTflBS vith craat auceaaa. Theee pada ara uaed for aadical and allaming implication' During «»p«riaent8 with jm»»a-irr«dl»tion to «odlfv flejiH» PVC, «e found IUTHIMO cainjgrnc sans thut at 75 kOy dose the rasultinr product of conductinr PVC was v*ry auch harder and the conductivity «•» hi/rh. Cro»»-1 lnlrinr rmrtureH « tyra of larthlne atripa have been aada froa oonduotinc TIG compound to aarth atatio theraontat ant«ri«l which aoas not *oft«n on tn<- apcl inntion of h»«t. Our electricity froa tha body during driving. Tha atripa ara oonnaetad to tha work covered a rmnfr of e«r»on M«c»r Joadlnm. R#au] tinr froa thia work, back of tha car chaaala aad is Just pround of tha road. During driTinc tha wa produced a rirld conductinr rVC coapound having a resistance of 1»'» than atripa actually touch tha cround and aarth any atatio electricity that haa 3 ohas. One novel application evaluated was car katterv connectors to built-up lnsida tho ear. elisinate the build-up of lead sulphate, around the battery terminal and surrounding holder which eauae'corrosion rrobleaa. Flf 1< Conducting earthing atrip Note corrosion corrosion around battery terninal fOTaHTlM. iltlAS FOR COKPPCTIVI WC (sOa* say be aubject to patant application) fig 18. Battery connector Bade froa conducting PVC Conducting JVC can ba aitrudad on tha outalda of a coaplex or slapl* cabla for earthing to raplaea aluainiua aatal ooTarin*. Trial quantitlaa hava O?PtATIBG THEATOES tlraady baan aaaufaotura* and found to ba axtraaaly varaattla. Suoh a oabla Conducting footwear and selected conducting flooring should be used in can ka appllad to diffieult oornara of a building and ldaal for aub-aeonoalo opera tine areas of hospitals and cliaice. HoualBf projaota. SlIMS 15-17 Ml 81I1LD1K0 K3.TPC Many alaetronle applleatlena axlat far the ua« af conductinc TIC agalnat Conducting PVC is another outlet for ninlnn belting Modifications and alaetro-aacnatle lntarfaranea. Bxaanla* ara eaapeaant heuainca and oapa. earthing connector* found in collieries and ainei, Thaaa traai ara baing lmaatlgatad by tha alaetronle indue try. SLIDES BATPO APMCATIOW It is faaslbla for atripa of conducting rVC to aa buriad Into oaaant and usa* -10- C 16.10 KILIflBT There are »»y applications lor mint eonduetiae PVC la solitary outlets. Conductiaj footwear Hustd by tha JUTT 1» frifatee to avoid atetic build-up for clseils e»ploy»ent. It 1« alao used ia a nusToer of arunitt componenta. COBS.BSICH The electrical propertiee of eonduetlnc PVC dependa on tht technology ecployed in tht •anufaeture ud processing of thi» material. Observed changes la concuctlTity ware directly associated with thia teehaoloey which could change by May orders of macsitude if injection/aztrusion conditions wtre sot strictly obaarved. In thia papar, tht author fives sow interest In* detiils of work uodtrtaktn on conductinc FTC to achitvt eocaercitl aectptas:; io specific artaa of industry. | The author would llkt to think ASCI for perilssion to present this paper and to Kr Lawrence Xayntr (az iSSl) and Dr Ouy Kesrs of AZCI for their Taluable help and (Uldanea durlnc thia work. Tht author would alao like to acknowledge the eo-oparation of Kr Robert FeiBblua of Coathu Boldinc* for aakinf available tn«ir footwear injection aouldir.c aachinaa at Dnitad-?raa Footwear at all tiaes. 7haaks art alao flue to Codaata Plastics for assisti»C with the floor tilt project and to th* SAS9 and SASU for tieir ioraluable discussions. y.ETgtEHCtS 1. COLLETT D.B. * BCLG3 S. U96o) British Patent 933.140 2. BIB30K W.T. * ZLACEIS ?.i. ATTIS1TIC FOOTWSiK (07T 1975) WO.CP LXTS^SS TiSBUt mSSBl: 15*6577 i. S1BU BDLLSTOt - ATCUS; 1979 - VOLIIKI IS HOT321 20 1. SOB BDU^rXH 9:12 - A0SC5T 1980 5. SAIS STK.LSTHI 10. Do 6. - nstUART 1981 6. BLOOM L.I. U98JJ Prirate cocsuaieation to laooa Arohlttctt. 7. (LOOM L.I. Cross-Liaked Polvawri In Poo Wear - nasties A- Xubbfr News Just 19 6. IRITISa SIAKSttS $451 U977; Eltatrically conductinf and Antistatic lubber footwaar. 9. SITSSa ITAKBUE 2050 (1978; Electrical Resistance of Conouctive and Anttaut; products aaat rroa polTmerie materials. '0. ASKS rmicAnoK. avmo LZSAR - co«am;r/« TLASHSS (HAKC: iy66j il. ABCl/SLOOK L.I. - Ktp. of South Africa. ProT.pattat Mot 79/6644 Uy79) 2. AECI/BLOOK L.Z. - Dsited States Patent Muabtr i?11.9 OPTICAL FIBRES IN TELECONNUNIUiIONS By: Dennis R Forster B. Sc (Eng) Siemens Ltd. WALTLOO Presented by: J. Franco B.Sc (Eng). Siemens Ltd. WALTLOO For 9th National Conference of the Plastics and Rubber Institute (S.A. Section) 1987. SYNOPSIS Optical Fibre technology meets the requlranrnts fnr the high speed transmission of large annunts of Information In Ihe mudern world, lhe Information is transmitted as pulses of light In a glass fibre Instead of the traditional electrical signal transmitted on metallic electrical conductors. Optical fibre technology is particularly well suited to digital signals. Thousands of telephone or data channels can be transmitted along a single fibre, due to Its high bandwidth. The low attenuation of optical fibre enables long distances to be spanned without repeaters. Additionally, optical signals are lmnune to electrical Interference and crosstalk, resulting In a high quality signal. C17.2 C17 .3 A large frequency bandwidth Is needed to transmit so much Information all at The basis of telecommunications over the past hundred years has been the once. The electrical attenuation of copper pairs and co-axial cable Increases telegraph and telephone, transmitted over electrical conductors or as a radio logarithmically with bandwidth le. large quantities of Information can only signal. Transmission technology has been repeatedly updated and Improved, but be transmitted over short distances on metal conductors. See fig 1. there were no revolutionary Innovations until the development of optical flore in the early 1970's in the USA. Optical fibres have a constant bandwidth-attenuation characteristic right Into the Gigahertz range. Thus longer distances can be covered using optical fibre BASIC PRINCIPLES as a transmission medium, with fewer or no repeaters needed to amplify the signal along the route. tan has used visual means of transmitting Information before eg. Aldls lamp Furthermore, optical fibres are non-metallic and thus iimune to external and modulated light beans through air. These methods have been limited by electrical noise which interferes with the Information signal and can degraae atmospheric conditions and topography. The optical fibre is a thread of very the Information eg. Noisy telephone connections. pure silica glass with low attenuation to certain wavelengths of light. A modulated light signal can be transmitted through this fibre over a This is particularly important In industrial and high voltage environments. considerable distance, even around corners, and received at the far end. It Is also useful on the Hlghveld with Its high Incidence of lightning strikes. Lightning not only Induces noise in metallic cables, wit cm alsn A typical telecommunication system would be designed to do the following: damage cables ana equipment connected to the cables. A voice signal is converted to an electrical signal by a microphone. This signal may then oe modulated or altered to enable it to be transmitted more The problems and dangers of Induced currents on telecommunications routes easily or effectively. The modern method Is to convert the analogue voice running parallel to power conductors (ESCOM, SATS) also fall away using signal to a digital signal eg. Pulse Code Modulation (PCM). Often this non-metallic optical fibre cables. There Js no problem of having equipment at signal Is multiplexed, or combined with many other similar signals from other opposite ends of the cable at different voltage potentials. sources, ana sent together on one transmission route in order to use available cables more efficiently. These modulated and multiplexed signals are then No crosstalk arising from the Interference of two electrical signals eg. amplified and transmitted on copper wires, or converted into a form suitable •crossed lines' Is possible on optical fibre transmission routes. for radio or microwave transmission. At the receiving end the signal is Fibre Optic cables are also generally physically smaller and have lower mass demultiplexed and demodulated and converted back into a form which we can than equivalent copper cables. They are easier to transport, handle and understand eg. sound waves. Install than copper. It Is thus also easier to manufacture and handle longer lengths of optical flore cable (typically 200On), resulting in fewer cable For transmission over optical fibre, the modulated, multiplexed electrical Joints. Silica, derived from sand. Is a much cheaper and more abundent signal Is converted into intensity modulated light which is launched into the resource than copper. However, considerably more nigh technology Is required optical fibre. This Is done using a special laser diode or Light Omitting to make an optical fibre from the raw materials. Diode (LED). Most optical transmitters in use today operate at a wavelength of 860 nm or 1300 nm which falls In the Infra-red part of the electromagnetic spectrun and is Just Invisible to the human eye. The optical receiver Is a photodlode which converts the light back into an electrical signal for demultiplexing and demodulating. Usually, two fibres are required for two-way (duplex) transmission. Tt€ ADVWTAGES OF OPTICAL FIBRE IN TELECOmjNICATION There Is an Information explosion taking place In todays world. More information needs to be communicated to more people In more places In many different forms eg. voice, video, data, teletex, telefax, broadcasts. Optical fibre characteristics enable it to carry more information than copper conductors, over longer distances and with less Interference. SIEMENS Ltd*«k SMCNS Lid-Be* C17.4 C17.5 There are also disadvantages In using optical fibre Instead of copper: TRANSMISSION METHODS The techniques of Jointing, or splicing, fibres and of terminating fibres to plug Into terminal equipment require specially trained personnel, expensive Jtte choice of wavelength Is largely determined by the spectral attenuation equipment and a cleaner environment than for electric conductors. Mare care characteristic of the material from which the optical fibre is made. This Is is required In handling the delicate fibres. shown for silica glass in fig.3. Wavelengths where attenuation is lowest are used i.e. 86Orm, I300nm and now ISCOnm. This characteristic is easily The optical line terminal equipment is also more expensive than electrical observed when white light Is launched into a fibre at one end. To the naked equipment. eye the light at the far end of say, 1000 metres of cable looks red. The successful manufacture of optical fibres is an Industry requiring high technology and expense." ATClstli"•"" '~ "-—e onl'y company Jdrawin" ' g opticaTfibre* '" s In Suitable optical diodes have to be manufactured which transmit and receive Sout" "h AfricaAfrlr. these wavelengths. Semiconductors made of GaAs for example are used for transmitter diodes. Photo diodes for receivers are made from SI and (ie. MANUFACTURE AND CHARACTERISTICS OF OPTICAL FIBRES. Non-linearities between the optical-electrical characteristics of transmitting and receiving diodes limit the use of direct intensity modulation of the There are three methods of manufacture of optical fibres. All three involve the manufacture of a preform using vapour deposition processes to form a glass light signal. Far better results are obtained when the electrical signal Is rod. Different concentrations of the vapours at different times during the deposition process result In a distinctive cross-section for the fibre refractive Index. Outer diameter is between 125 and 250 microns, depending on the fibre type. pery. The differing refractive Indices within the fibre causes total Internal In order to launch useful quantities of light energy Into the very small reflection. In this way a beam of light is kept within the core of the glass cross-section of the optical fibre core endface, very high power densities flDre, even when the fibre is bent. An optical fibre is also often referred to have to be generated by the LED or laser dlooe. These approach the power as an optical waveguide. Fig 2 shows different types of optical fibres density at the surface of the sun, but total power lanuched into a fibre by a Identifiable oy their refractive index cross-section. laser diode is only In the region of one milliwatt. Thus the receiving photodlodes must be very sensitive components. Step index fibre has been largely replaced by graded Index and single mode fibres. Because of path length differences between the direct ray of light and the rays taking zig-zag routes, the light signal does not all arrive at Fibre optic systems are designed with the aid of a power budget.An example is the receiving end at exactly the same time. Thus a pulse transmitted Is shown In table 1. The difference between transmit power and receive power Is spread out at the receiving end. This results In a reduced bandwidth. The used to calculate the maximun loss allowed in the optical fibre route. With longer the fibre, the greater the spreading and the lower the bandwidth. Thh all power losses known (attenuation in the fibres, splices and connectors) the effect is reduced in graded index fibres, because the velocity of light is maximum distance over which the system will operate can be calculated. faster within materials of lower refractive Index. The light in the longer trajectories thus travels faster than in the mare direct paths. CABLES AND INSTALLATION Tne very narrow core of the single mode (or mono mode) fibre restricts the light to only the most direct path, or one mode In terms of waves. Single The more practical aspects of designing a fibre optic system must also be mode fibre Is currently the cheapest on the world market. attended. The most important of these is the type of cable route, i.e. aerial, ducts, direct burial, underwater. This will affect the cable design. The refractive index of glass also changes with wavelength.(Fig 3.) Thus light Optical fibre cables can be desloned for almost any typp of Installation. of different wavelengths are attennuated more and less, and arrive at the Once the fibre Itself Is suitably protected against mechanical and cfiemlcal receiver at different times. No transmitter, not even the best laser diode. damage, the cable construction can take nearly any form. One typical cable Is an Ideal source which transmits only one specific wavelength. This design is shown in flg.5. differing attenuation of different wavelengths Is called material dispersion. S«MtN$|.M*pk WCNSltd/lpt •^Tflrrr C17.6 C17. / Individual fibres are laid In protective plastic buffers. These form the basic component of most optical cables and may be constructed from a variety of materials to suit enviroment conditions. Flg.6. Shows the difference Technological Improvements will essentially lead to longer repeaterless between loose and tight buffers. Tight buffers (also called secondary sections. This will be realized by developing the optical transmitters and coatings) do not allow any movement of the fibre within the buffer. The fibre receivers operating at wavelengths of 1500nm and higher where fibre itself has a thin primary coating to protect the surface of the fibre. Loose attenuation is lower. Research Into the use of other materials for the buffers allow the fibre to move Inside the tube, and very effectively decouple manufactur,iniiuiai.uuice oufi thesinese components iss underway.. There iss investigatioinvestigatlon Into the external forces from the fibre. The fibre is helically laid inside the buffer use off Flourine instead off Silicon as the primary materiall fnfor fhtheo manufactur~^e tuDe and the resulting overlength reduces the effects of strain on the cable. uoif thtuihec opticaunucail fibresriDres. Plastic polymerr opticarj ll waveguideinat-cnasi havror e tsno fara*r showsh, n (flo7.). Loose buffers may be filled with a thlxotroplc compound. It is considerably higherr opticall attenuation rnmwrercomparedi tno siliccm-a ->—glass-. It is also possible to place several fibres in one loose buffer tube. still early to determine whether plastic optical fibres can become widely used In telecaimunication. Integration of functions at the opto-electronic interface Is also being The buffers containing fibres nay then be handled similarly to Insulated wires researched. Optical waveguides will be manufactured Into semiconductor chips in a telecom cable. A central element Is usually provided as a support using etching and doping processes to allow better coupling to optical fibres. mater, and may be steel or non-metallic. Additional strength Is provided by The same principle can be applied to switch, deflect or modulate optical Kevlar Yam around the laid up buffers. signals by the application of electrical fields. One day there might even be optical computers. The entire Inner cable is then be sheathed In polyethylene. Additional layers of armouring and protective or conductive materials can be applied as CONCLUSION required. Composite cables containing both optical fibres and electrical conductors are not uncommon. It is often convenient to Include conductors for power feeding to repeaters, in the optical cable rather than run additional Optical Fibre technology has become established as a reliable and effective cables, when the repeaters are in a remote location, eg. undersea cables. means of meeting present and future telecommunications requiranents. It is Ideal for the transmission of digital Information and outperforms coaxial cable and twisted pairs to become economically viable for high volumes of ESCDM has already Installed an aerial groundwlre conductor with a core of information and long distance applications. The additional Imnunlty to optical flbresi and a flgure-8 cable where the optical fibre cable Is attached electromagnetic interference ensures high quality signal transmission. to a glass fibre reinforced supporting element. Optical Fibre technology Is now an indispenslble part of the modern telecommunications Industry. SAPO Installs most of Its optical cables in pipe and chamber systems. Several Major South African municipalities have ordered pilot cables containing both optical fibres and copper pairs. THE FUTURE Most of the world's leading nations are now using optical fibre technology. Optical Trunk cables being laid today can meet all the foreseeable needs for many years to come and several markets are flattening off as the Initial major requlrment for optical rahle Is saturated. The next big breakthrough will occur when optical fibre techology is Introduced Into the subscriber network. Businesses, and even houses will have their own optical connection. Optical fibre is Ideal for ISDN (Integrated Services Digital Network) which is currently being developed overseas and which allows a host of services to be provided over one subscriber connection. e.g. telephone, teletex, telefax, video, TV and stereo sound broadcasts. The cost of such a service will have to become econanlcal before widespread use Is possible. CMENSLld«pt C17.9 C17.8 REFERENCES: 1. Bark. Peter R. and others Stress-strain behaviour of Optical Fibre cables. 28th International wire & Cable symposiun, N J. USA 1978. : Networks using Fibre Optic Cables ^ UJ 2. Braun. E; Siemens AG presentation Optical Fibre Cables and their Application 3. Fo^oosa. S: presented to the Institute of Railway Signalling Engineers. Johannesburg 1985. 4. Kessler Marketing Intelligence Report on Optical Fibres 1986. N 5. Kraus. J.D. and Carver. K.R : Electromagnetics 2nd Edition. Me Graw o : Introduction to Connmlcatlon Systems. 6. Stremler. F.G. 2nd Edition. Addison - Wesley 1982. 7. Malke. G and GfisslnQ. P : Llchtwellenlelter Kabel. Siemens AG publication 1986. : Reliability of rilirc nptir Cunlt; Systtms. 8. International cunferwice on lelecumunlcatlons. Seattle, USA. 1980 : Siemens Telecom Report. Special Issue: 9. Various Authors Optical Communications. October 1983 SKMCNSLKfCpk '"ifirvrTi ATTENUATION 20.0- dB/km 10.0 5.0 •»» 0.1 700 800 900 1000 1100 1200 1300 K00 1500 nm 1600 — WAVELENGTH Fig 3. Spectral t ion of different optical fibres. CENTRAL MEMBER BUFFER FIBRE FILLING COMPOUND BUFFER Fig 5. Typical Cable Construction Cl/.lb C17.K 1.0 : FIBRE / / TIGHT SUFFER / 0.5 / V TI6HT BUFFER LOOSE BUFFER FILLED LOOSE BUFFER / / / ^.OOSE BUFFER © FIBRE WITH LACQUER •B PLASTIC MATERIAL ES3 FILLING CCHPOUNO / / OTS "CABLE Tig 6. Loose and tight buffer construction. Fig 7. Fibre strain vs. Cable strain For loose and tiqht buFFered Fibres. Wavelength nm 1300 Fibre grad mono Transmit Power dBm -3 -4 Receive Power dRn -40 -43 System Attenuation dB 37 39 Margin dB 6 6 Connector loss (x2) dB J 4 Cable Attenuation dB 28 29 Splice Losses dB/km 0.1 0.1 Repair splices dB/km 0-0.2 0-0.2 Fibre Attenuation dB/km 1.0 0.7 Heaultant Cable (ft/km 1.1-1.5 0.8-1 .1) loss Max section length km 21-25 29-36 Table 1: Typical Power Budget for MDMbit/s Fibre Optic System. 53 2* 01 RADIATION EFFECTS ON POLYMERS AND ELASTOMERS 1) A HAUKNHOKST ATOMIC F.NERGY CORPORATION PELINDABA ABSTRACT Radiation damage is discussed with respect, to the various factors influencing such damaqe. Polymers are classified to the predominant reaction result i no from i r r .wl i it i "ii ((' r us.1: 1 I nk L IK] ul Sc 1 :;;i I i>ll ) . Radiation effects on P.V.C. and E.p.D.M. are briefly examined as examples of thermoplastic and elastomeric materials. Brief mention is made of wood plastics. Tables qiuinq ci.im.iqn thresholds of common polymnrs and ol.'stomcrs >>tt' a i VIMI . Kj 8 C18.2 C18.3 Where a polymeric material is subjected to any form of nuclear radiation the properties of that material are changed. I shall The most common effect in irradiated polymeric materials refer to such changes as radiation damage. is lonisation, where .in M^ctrnn is i <-movrd fr-xii .i Although not all of these changes are detrimental with respect molet-uli? thus providing an ionic pair. Kubserjuen r 1 y the to the uses to which the material will be put, they are electron may be recaptured to give a highly exited species, it may be trapped in the vicinity of its parent considered to be damage in the sense that the properties molecule, or It may move to be trapped at a remote differ from those of the unirradiated material. location or be captured by another molecule, to give luu ionic species A+ and B". The damage to the material is dependent upon a number of factors: - With the high energy radiation involved in a cobalt 50 plant all chemical bonds might bn denmnd r"]u.»lly likely i) Type of Radiation to be broken .ind radiation damage would occur .it random. li) Dosage This as we will see later is not the case. iii) Presence or absence of oxygen iv) Presence or absence of suitable anti-oxidants and li) DOSAGE stabilisers v) Molecular arrangement of the material The amount of radiation i.e. dose or dosage is the most H* will briefly examine each of the above factors before important variable which affects the extent of damage in a material. In any given material, radiation damage is considering a number of typical polymers in the light of the proportional to the dosage, irrespective of the type of above. radiation particle. Amount of radiation or dosage, is therefore the variable in terms of which damaqe is i) TYPE OF RADIATION usually described. High energy radiation, in passing through matter can cause three distinct changes (1). Dosage is described by two types of units, those which describe the radiation Mold in which t ho m.iteri.il i •; (a) reaction with and modification of the atomic placed and those which describe the amount of energy deposited in the material being considered. I in11 nucleus (b) displacement of but no change within the nucleus definitions are shown below. (c) interaction with the orbital electrons, but no direct interaction with the nucleus Roentgen: amount if ionising radiation (gamma and X rays) which imports R3 ergs per gram ot1 air With the energies generated by the electron beam and Rem : the amount of radiation of any type which has cobalt 60 generally used for the irradiation of the same biological effectiveness as one polymers in commercial plants, no nuclear changes are roentegen of X rays or gamma radiation possible and as a result there can be no induced radioactivity. CIS.4 C18.5 - 3 - Fad the absorbtion of 100 ergs of energy per gram The molecular arrangement of a material influences the of material from radiation particles ability of the material to withstand the energy imparted to it by radiation. The evidence from experiments The unit generally used in polymer irradiation is the clearly shows that the effect is siqni f i r.int .infl th.n it Gray (Gy) whom 100 Bad - 1 Hy. .KWMunt.H at lt?.iHl in par t , (ni much r>f the difference in the radiation stability of many types of polymeric When high doses are absorbed by polymeric materials in compounds (3)(4)(5)(6)(7). air, the dosage rate becomes important, this is because of a transition stage where oxygen diffuses into the In polymers containing aromatic structures (benzene outer layers of the polymer. In this case radiation rings) there is greater resistance to radiation damage. induced oxidative degradation (chain scission) may occur This is due to the forces binding the atoms being able in the outer layers, whereas the inner parts of the to resonate between at least two structures. polymer may be non-affected or even croslinked (2). The size of the molecule has minor importance. In any iii) The presence or absence of oxygen during irradiation is series of similar compounds of the same geometrical significant when the dose is high but the dose rate is arrangement, the radiation stability decreases as the low. In the case of a low dose the presence or absence molecular weight of the molecule increases. of oxygen is not significant. The presence of oxygen can aslo be significant in the irradiation of very thin The degree of saturation or unsaturat-ion is also of samples of solid organics, in which oxidation is more major significance. The radiation stability decreasing than a surface phenomenon!. as the degree of unsaturation increases. iv) The effect of radiation and hence the extent of The radiation damage in polymers takes the form of chain radiation damage can be significantly altered by the use scission with or without subsequent crosslinking taking place. of suitable antioxidants or stabilisers. Included in Since crosslinking and scission occur concurrently in most this category are also various croslinking agents. It cases, polymers can be classified according to the predominant is by the intelligent use of these compounds that process. many beneficial modifications of polymers can be achieved by means of radiation. TABLE I v) With the molecular arrangement of the material GROUP 1: - CROSSLINKING GROUP 2: - SCISSION (composition). It has been shown that the interaction of radiation particles varies for different elements, Polyethylene Polyisobutylene this is because the composition of the material affects Polypropylene Polymethlacrylates the extent of damage that occurs from a given radiation Polystyrene Polyvinylidene chloride dose. C18.6 - 5 - C1B.7 - 6 - Polyacrylates Cellulose The polymers in the centre of the table undergo both Polyvinyl chloride Cellulose acetate crosslinking and degradation. Modifications of the polymer or Polyamides Polytetraplourethylene the addition of crosslinking agents are necessary to ensure Polyesters Polytriflourochlor ethylene that crosslinking predominates. Natural rubber Polyvinyl chloride Synthetic rubbers Polyethylene terepthalate Polymers with the structure: - Polyvinylalcohol Polyacrylonitrile Ethylene - vinyl acetate co-polymer I Changes in irradiation conditions may in some cases shift a C polymer from one group to another. When crosslinking \ predominates over degradation (Scission) the molecular mass increases until a three dimensional network is formed where on R average each polymer chain is linked to one other chain. —' -n. If the more commonly used polymers present in Table 1 are rearranged in table form in order of crosslinkability we get the following: - Degrade on irradiation examples are Polypropylene (R * H) and Polyisobutylene (R * CHj). Such polymers will not be TABLE 2 (10) discussed further in this paper. Polyethylene Cross-linking Examples of polymers in the top section of the table, natural Natural rubber rubber and E.P.D.M will be discussed and P.v.C. will be E.P.D.M. discussed as an example of a polymer needing modification to Polysiloxane enhance crosslinking. Polyvinylidene flouride POIVVINVICHLORTDE Polypropylene Plyvinylchloride P.V.C wilt be discussed first as it has been established as a Polyethylene oxide large volume radiation process. P.T.P.E. From table 2 it can be seen that P.V.C. does not undergo a Polyethylene tcrepthalat* predominantly crosslmking reaction when irradiated. When Polyi»obutyl«ne Degradation irradiated in vacuum it crosslinks only slightly. CIS.8 C18.9 - 7 - t If a very high dose is used (in vacuum) the resulting product Heat shrinkable tubing Piping - is intensely coloured by a dehydrochlorination reaction in n foofwedr which a polyene sequence forms a charge transfer complex as 't packaging follows. E_. P . D. M P.V.C was an example of .1 thermoplastic mfltpri.it which lipi.n 1! 1 irradiation w.»s ri-nvortH to .i Ihprmnsi ! , i.e. .i thw<«' • 1 imi-n-: i .III.I 1 iH-twoik. llivni.| m.ilk. il till I •• I ••n- •- -. In II,.- ..ii.pn,! 4-cHa— CH=I - « thermoplastic vis .i vis solubility, elasticity .>nd mp.irt resistance. o wm E.P.D.M is an customer which until cured (vu loin I .«i->'l) qualifies as a thermoplastic with a very low tensile modulus. Once cured (vuloinised/crcssl i nkeii) thp elastomer c-,in bo regarded as .} thermosct and exhibits the properties commonly An efficient crosslinking with little colour formation may be associated with rubbers. induced in irradiated P.V.C by the inclusion of polyfuntional monomers. Various monomers have been sucessfully compounded Elastomers as 4 class of materials are amonq those most with suitable plasticisers. The more sucessful being ethylene susceptible to radiation damage. They are materials which glycol dimethacrylate, trimethylolpropane trimethacrylate and consist of small submolecules of 10 to 20 atoms polymer ist"i to ethylen* glycol diacrylate (11). form long chain like molecules. The properties of those compounds such as elasticity and rompressibi I 11 y riopond upon a A comparison between an unmodified P.V.C and a crosslinked balance between Ihn inhftiMit l|pr'li>ni ot mot ion ul the r'h.nn P.V.C shows an increase of 150 % in tensile strength and a and the degree of cross!inking or chemical bonding between tho decrease of 100 X in elongation at break. For electrical individual chains. applications the irradiated P.V.C is eminently suited due to the increase in dielectric strength, (150 X) and the exeptional increase in resistance to a hot solder iron (600 %). Other fields in which irradiated P.V.C is being used or has potential are: - cia 10 The action of energy absorbed from ionizing radiation on these compounds disrupts the bonds between the atoms and destroys The radiation crosslmking is achieved with a lower dose rhtin fine balance. is necessary for L.D.P.E. or vistalon. For the above reasons research on radiation process for rubber From the above two examples it can be seen that lrr.irintion and rubber compounds has concentrated more on the use of can be used as a tool in the polymer industry in different ionising r£diation in the curing (vulcanising) of rubber ways. A third use of radiation is in the initiation ^f rather than on the subsequent modification of cured rubber polymerslation in monomers. A siqni f i cant uso of t h 1 .s coir pounds. mechanism is in the manufacture The advantages to be gained fron radiation curing of rubber In this process wood is immersed in monomer under v.icuum. Thn are as follows: - wood with the absorbed monomer is then 1 r r no"! .it p The radiation technology section at the A.E.C. has been Methods have been developed where the wood can be made to working on the radiation curing of E.P.D.M. for use in high absorb monomer only to a certain dppth thus qtvinu, rise to n voltage cables for the past two years, and has succeeded in polymer shell around the wood. Various modifications of the producing a suitable material for that purpose. above process await exploitation by the building and furniture industries, not to mention the toy industry. Significant differences were obtained by using mono, di, and tri methacrylates as crosslinking agents. Success was also To sum up we can say that irradiation of polymers result? in obtained uffing arryl.ites and dj-aery late.*?. damaqp to the pnlymor. This Ham.iqn ran howrvrr hi» ront rnl l"d and even used belief 1 <'1 >i 11 y . In n os.s 1 1 nk 1 ML] >I MKI 1 ecu 1 II. wi I..".hi , li.irli.il . I'li I'IMMII f\ tjn p TABLE 3 < 1 •>« / I . (3) T. SF.CIK'HI. K. ARAKAWA 12 3- 5 M. I TO, N. MAYAKAWA .Hid PTFE MA«"llt, Fadi.ition. Phvs. r i. 1 98?, 2J , 49r>. Poly me thy line tnacry late (4) H. WILSKt, Colloid Polym. Sci. 1976, 2S4 A 51 . Polypropylene (5) A.A. BENnfcRl.EY and H.S. BKRNSTEIN. J. Appl. Polym. S u 1969 1_3 . 50S. Polyester 1 Plasticised PVC (6) R. IIARRINUTON .ind R l.IBKRSPN, Mod. I'l.istics 195H l')'.<. ) HDPE 1 (7) R.L. CL.OUGH and K.T. GIl.l.F.N. Rndiatlnn. Phv.« . rUrm. I LDPE i 1_8 fifil . Polycarbonate (8) 1 I'K C. l)i: IHM.I.AJN, Hull .it ion. IMiys . Ch'-m. I 9H ! , ?l , 4 9 Rigid PVC 1 (91 R.W. S INGLKTON ,md R..I.T. Cl.AHHMRN, 1'rorj, in Hubb'T iti.l ! j Polystyrene Plastics terhnoloqy Veil il , No. ?. April l9Hf>. ABS | (10 1 H'lRO J. R.iriint mri <- ri. ss 1 l 'ik i iq r>f P.V.'.'. wi I li rtliyl Nylon - J ulyrnl dimcth.ictyl.itc. hire .uicl April. OH-III. <[97(il I !. TO TABLE IV Polyurethane rubber Natural Rubber Styrene-butadiene (SBR) Nitrile rubber Po^ychloroprene Chlorosulphonated PE Silicone rubber Butyl rubber "*O04£ i* («*», Irradiation can be used to crosslink rubbers and to initiate polymerisation. Even in cases where irradiation causes doqr.itijt. ion ol the polymer this fact can be put to positive use in the manufacture of adhesives and lubriciants. In field for radiation processing in polymer materials is open to be exploited. It remains for industry to see to what extent the damage of polymeric materials can be made to suit it. C18.lt C18.15 OP Pe*OXIT>B ANO fifiOIATtoH t.u6oi-f>Tioti (ep. o. M. OAtSlNKL 3,45 H9 13 wore* /IT 22 II » m' D C u cc u NO f-l i: 19. i RADIATION CROSSLINKED POLYMERS IN THE BUIT.DTNG INDUSTRY T A OU PI.ESSIS and J H SMIT, Iso-Ster (Pty) Ltd, P O Box 3219, Kempton park 1620 ABSTRACT The South African building industry today is presented with a unique challenge to provide alternative low-coat housing at a rate that conventional construction methods and materials cannot meet. Vt is generally acknowledged that the locally produced polymers such as polyethylene and polyvinylchlor ids can alleviate some of the problems encountered with convent ionn 1 construction techniques. The radiat ion-mo South Africa is presented with a monumental but unique r-hal lengp ^i in the coming decades to provide acceptable and affordable ~p' housing for all its peoples. There is enough reason to believe f— that more than the total increase in the South African population will in future settle in the urban and semi-urban K) areas [1]. It was estimated ten years ago that economic forces -X> alone will result in most of the anticipated increase of 21 OC million Blacks by the end of the century to be absorbed in the QC metropolitan areas C2J. It is generally accepted that the BlacX Q urbanisation level in the year 2000 will be between 40% and 50% r\ - implying that almost 20 million Blacks will have to be M accommodated in the urban area* [3]. To compound matter* it was c-J 2 C19.2 C19.3 estimated that In Hm the backlog in housing for all race the unique set of cirrniniitaiic»< nirrenMy rmvnillni] In Smith r groups alraixly nmo.mi «.1 to nli >0<) 0(10 unit* til. n H" +~CH2 - -» H2 +-CH -1 The exposure of PE to ionising radiation leads to the chemical (31 linking of adjacent macromolecules at or close to their points -CH - CHj" of intersection. This crosslinking can be both intra-molecular -» I or inter-molecular - these two processes are indistinguishable ~<5H - CH£" ~CH - CHf (41 on the grounds of the change that takes place in the irradiated polymer. In agreement with crosslinking of a polymer in general, the radiation crosslinking of PG can lead to the following three H- +~CH2 - CH? H2 (3al important physical changes in the polymer: (i) An improvement in the thermal stability of the polymer resulting from the restrictions imposed on Fig 1. The radiation n J ink j nq of polyethylene the molecular movement. In the case of PE the softening point of the polymer can be increased to more than 130 "C depending on the degree of crosslinking. As the crosslinked polymer can no The three most important phenomena which are observed when PE is longer melt and drip at high temperatures, it has irradiated are the following: a far superior resistance to fire propagation and the material can be considered to be The evolution of hydrogen gas. During the irradiation of PE self-extinguishable. Similarly, melting and a mixture of gases is formed consisting of 98% hydrogen and scourging when exposed for short periods to high smaller amounts of methane, ethane, propane and butane, temperatures will be restricted. together with other hydrocarbon gasses [II]. Harlen established that the saturated hydrocarbons can be (ii) An improvement in the mechanical stability of the attributed to the radiation degradation of the side-chains polymer because of the restriction of the in the polymer, because scission of the main polymer chain macromolecular movement leading to improved does not take place readily [12]. The rad iat. ion-rhemi rnl cold-flow characteristics of the polymer. Products yield of hydrogen gas can be taken as G(H?) = 4.3 [13]. can thus be made that will have a far greater dimensional stability, especially at elevated A change in unsaturation. Dole reported that the temperatures or external forces. The vinyLedene-type double bonds, which are originally present macromolecular restriction also renders the in the polymer, very rapidly disappear under irradiation, polymer insoluble to common solvents for the while trans-vinylene-type bonds accumulate [14,15]. Most, polymer and the extent is again dependent on the investigators accept that. the formation of trans-vinylene degree of crosslinking that has taken place. unsaturation is the result of a "molecular" detachment process of a hydrogen molecute from the hydrocarbon chain, (iii) The introduction of a "memory effect" which is because it was observed that free-radical scavengers have today used on a very large scale for very little influence on the formation of trans-vinylene heat-shrinkable applications of the polymer. unsaturation when the polymer is irradiated [16]. The formation of this unsaturation can be readily explained if it is accepted that the hydroqen atom which is formed in the primary process is a "hot" hydrogen atom as indicated in reaction (1) in Fig I [17,18]. This "hot" hydrogen atom then C19.6 92JL- 7 reacts with the closest methylene group in the same molecule free radical chain Increases the probability for a polymeric as ehown in reaction (2). The radiation-chemical yield of free radical combination reaction such as reaction (4) to take place. and hence increases radiation cross)inking in general. In trans-vlnylene unsaturation can be taken as G(-CH-CH-) - 1,8 practice it is found that a crosslinking agent at a [133- concentration from 2* to 5% enhances the degree of crosslinking Crosslinking of the polymer. From a practical point of view to such an extent that the desired radiation crosslInking can be this change Hi ot course the mo«t important. The hydrogen achieved at doses as low as 50 kGy. Depending on the improvement in the physical properties of the polymer desired, a degrne of atom formed in reaction (1) can react with a neighbouring crosslinking from about 40* to 7n» In qnnnrnlly snf rli-ioni . The molecule through hydrogen abstraction to form hydrogen and a irradiation dose and crosslinking agent concentration are thus polymer radical, as shown in reaction (3). The two polymeric optimised to achieve the desired physical properties, free radicals formed in reactions (1) and (3) subsequently undergo a combination reaction to link the two neighbouring molecules, as shown in reaction (4). To favour the combination of the two radicals, the processes in reactions APPLICATIONS FOR CROSSLINKED POLYMERS (3) and (4) are supposed to occur in a very short interval and within a very small volume element of the reaction medium. In such an event the two polymeric radicals would be Considering the unique set of circumstances in which the produced very close to each other, in a favourable position building industry in South Africa finds itself today, innovation for the combination reaction to take place immediately. will be the keyword and care should be excercised that we do not However, a reaction such as (3) also requires an activation restrict ourselves through a technical "colonial attitude" by energy of at least 8 kcal/mole - a value which is much constantly asking "but where else in the world is this being higher than the observed value of about 1 kcal/mole. It is done?". With the current attitude of doing away with therefore proposed that reaction (3) takes place through a unnecessarily strict regulations in all spheres of life, WE are process of "hot" hydrogen atoms formed in the primary presented with exciting challenges to develop new applications process (reaction (1)) as shown in reaction (3a). At room for plastics in the building industry and the improvement of temperature the radiation-chemical yield for crosslinking is these products through radiation crosslinking can open up new G(X) » 2,0 [19], avenues for plastics. Great care should, however, be excercised not to create the impression that these products are "sub-economic" or inferior to their counterparts made from more conventional materials and cost effectlveness should be the aim. From this simplified reaction scheme it follows that hydrogen is formed in both reactions (2) and (3), which respectively result It would be presumptuous to come up with a new list of potential in the formation of trans-vinylene unsaturation and applications of crosslinked polymers in the building industry crosslinking. Within experimental limitations, material balance slightly more than a year after the excellent proposals by is obtained* Morris [8]. However, let us look as some potential applications based on the restrictions of existing polymers that can be G(H2) - G(-CH«CH-) + G(X) overcome through radiation crosslinking of the final product. As mentioned earlier, in practice polymers are purposely The Codesta PVC floor tile that is formed through Injection compounded with so-called "crosslinking agents" to reduce the moulding and subsequently radiation crosslinked, is an excellent radiation dose required to achieve a certain degree of example of what can be achieved through the collaboration crosslinking required for obtaining certain physical properties. between a plastics converter and the radiation processing As- wilt be appreciated, far less information is available on the industry [10]. This floor tile which Is manufactured at high preclfics of these compounds and the associated chemical speed through injection moulding, is converted through gamma kinetics thst play a role. The most common cross link ing agents radiation into n high quality floor rov To conclude, it may be stated that the only limitation in this [13] A Chapiro, Radiation Chemistry of Polymeric Systems, new field will be our spirit of innovation and I am sure there p407, Interscience Publishers, Mew York, 1962. are many fields of application that you as plastic convertors are more competent to exploit and we would like to extend an [14] M Bole, C D Keeling and D G Pose, J. Am. Chem. Soc., invitation to all interested parties to contact us to develop 76, 4304 (1954). your particular idea. [15] M Dole and C D Keeling, J. Am. Chem. Soc., 75, 6087 (1953). REFERENCES [16] M Prober, 134th American Chemical Society Meetinq, [1] E J Harais, Verslag van die Wetenskapkomitee van die Chicago, 1958. Presidentsraad oor Demografiese Tendense in Suid-Afrika, Staatsdrukker, 184-185, 1983, Kaapstad. [17] A A Miller, E J Lawtrcn and J S Balwlt, J, Phys. chem., 60, 599 (1956). [2] P Smit and J J Booysen, Verstedeliking in die Tuislande 'n Nuwe Dimensie in die Verstedelikingsproses van die [18] A N Pravednikov, Y S Kan and S S Medvedev, Doklady Swart Bevolking van Suid-Afrika, IPSA Monografiereeks Akad. Nauk SSSR, Jj!_2, 254 (1958). oor Tuaeengroepprobleme, Instituut vir Plurale Samelewings, Universiteit van Pretoria. No 3, [19] F B Waddington, J. Polym. Sci., 31, 221 (1958). Augustus, 1977. [20] T A du Plessis, S A Tydskrif vir Natimrwetenskap en C3] A J G Oosthuizen, Verslag van die Komitee vir Tegnologie, 2- 16-21 (1984). Staatkundige Aangeleenthede van die Presidentsraad oor 'n Vcrstedelikingatrategie vir die Republiek van C21] AHA Roediger and T A rlu Plessis, Radiat. Phys. Chem. , Suid-Afrika, Staatsdrukker, pp 44-56, 1985, Kaapstad. 2]_, 461-468 (1986). [22] T A du Plessis, The Fole of Radiation in Polymer Chemistry, PER-21, Atomic Knerqy Board, Pretoria (1977). THE NEAR RESISTANCE OF POLYMERS by A. Ball Department of Materials Engineering University of Cape Town Rondebosch, South Africa ABSTRACT The performance of a variety of polymers subjected to cavitation erosion and sliding near has been determined using laboratory facilities which simulate conditions encountered in mining machinery. The modes by which various polymers deteriorate under erosive and sliding wear conditions are described. INTRODUCTION During the past fifteen years, the Department of Materials Engineering at the University of Cape Town has, in collaboration with the Chamber of Mines Research Organisation, investigated the tribological wear suffered by metallic, ceramic and polymeric materials when employed in the aggressive environment of thp South African mining Industry. The results of much of this work can be applied to other Industries such as agriculture and energy production. Emphasis has been put upon an understanding of the mechanisms by which steels deteriorate under abrasive and corrosive conditions. An outcome of this work has been the development of new alloys for the mining Industry. Work is now in progress on ceramics and polymeric mateials In order to assess their potential for various compone ..s in many Items of machinery. In particular their use in the hydraulicaily powered rock drills and hammers now under development'1' 1s being considered. This paper will describe the methods by which a range of polymeric materials have been tested for their resistance to cavitation erosion In water environments and sliding abrasive wear when In contact with metals. The preliminary results will be presented which will Indicate the better materials for these applications; this Information, together with the studies of the surface degradations, are now being used to formulate Improved polymer 'alloys' or compounds. It 1s our contention that polymeric formulations have great potential for various applications but research 1s required In order to gain the necessary understanding of the modes and mechanisms of wear of a given polymer under given mechanical and environmental conditions. C2O.2 - 3 - CP0.3 - 2 - EXPERIMENTAL frictional forces and near-contact temperature were recorded throughout the tests. Specific wear rates were calculated at the end of a predetermined sliding distance as the volume loss per metre of sliding per Newton of a) Cavitation erosion tests applied force. The damage produced on the polymer and metal surfaces was examined using the scanning electron microscope. Cavitation erosion occurs In hydraulic systems and can cause severe damage on valves, impellors and pipe work. The use of water hydraulics in the RESULTS dining Industry would greatly Increase the incidence of this damage and it Is necessary to have Information with regard to performance of candidate materials. <) Cavltatton Erosion and Polymeric Properties The cavitation erosion results'^' for a range of polymers together with The tests are undertaken using a modified ultrasonic vibratory drill<2>. their mechanical properties are summarised in Table 1. Glass transition The tip of this drill is placed at a distance of 0,35 mm above the specimen temperature (Tg) measurements are also shown. The materials tested can be surface In distilled water. In this way, cavities are created In the classified Into three distinct groups in accordance with their cumulative liquid due to the high frequency vibrations and the collapse of these volume loss (CVL). A fourth group failed in a catastrophic manner. cavities causes severe erosion damage of the specimen. The specimen is weighed at hourly intervals and examined in the scanning electron The erosion resistance of polyamide b.b appears to be outstanding up to microscope- periods of 7 hours. However, the rate of erosion then increases dramatically and after 20 nours the cumulative volume loss is 3.6Umnr as b) Sliding wear tests compared with approximately lmm-3 for ultra high molecular weight Polymeric materials are frequently used as seals and bearings in various polyethylene (UHMktPE). items of hydraulic and other types of machinery. Their performance will be of particular Importance in the operation of hydraulically powered rock Scanning electron microscopy of the three groups identified in Table 1 hammers and rock drills. The polymers will experience high pressures and showed erosion mechanisms to vary from fully ductile (Group I) to fully high velocities in environments contaminated with hard quartzite brittle (Group 111). The erosion of the 'soft' polymers (Group I) such as particles. It is considered important therefore to simulate these high density polyethylene occurred by a ductile tearing mode of conditions in the laboratory in order to assess the performance of polymers fracturelfig. 1). An intermediate erosion mechanism (Group II) is currently available and to 'design' new polymeric 'alloys' which will have exhibited by only one of the 'pure' polymers, namely polyacetal; the filled Improved sliding wear characteristics. polyacetal polymers showed a mode of erosion which can also be classified In this intermediate grouping. Ths hard glassy polymers like polyethylene Tests were conducted using a lOnm square polymeric 'pin' specimen which terephatalate were found to erode by a brittle (Group III) mode as depicted reciprocates against a 431 grade stainless steel plate under a fixed in fig. 2. pressure of 10 MP»<3'. The length of the reciprocating stroke was 50 rnn and the avenge speed is 0,25 ms"1. The initial surface roughness of the The relationship between erosion loss (5 hr CVL) and resilience number Rn, polymer specimens wts 2,0 micrometres and the steel was ground to « finish as determined by a Shore schleroscope, 1s shown 1n fig. 3. From Table 1 1t can be noted that a group of polymers (Group IV) failed 'catastrophically' of 0,3 micrometres. The specimens were Immersed In distilled water and the C2J.4 - 5 - cao.s when eroded and as such are not represented In fig. 1. The elastomeric friction for UMHWPE and PTFE are similar and considerably less than those polymers of this group, namely the polyurethanes A, B and C, are for the other materials. characterised by their low resilience together with low melting points. The behaviour of these Group IV elastomers, under cyclic loading, can best There is no direct correlation between any of the conventional mechanical be understood In terns of their relatively high mechanical hysteresis which properties and the sliding wear performances. However, 1t can be seen that leads to the generation of heat. This, coupled with their low thermal UHMWPE has the greater thermal conductivity and the highest specific heat conductivity, promotes a narked rise 1n temperature. Thus failure occurs capacity. by melting rather than by fatigue. In contrast polycarbonate (also Included In Group IV) failed catastrophically as a result of its extremely Scanning electron microscopy showed parallel wear grooves as shown in fig. high resilience which is indicative of its brittle character and Its 4. It is possible that these are caused by fragments of metal debris which Inability to absorb the strain generated by cavitation. are entrapped between the two surfaces. They cannot be produced directly by surface topography because the machining marks on the metal surface are Group III polymers, with the exception of polypropylene, are all 'glassy' fixed normal to the direction of sliding. Examination of the metal at room temperature, and have in general high resilience numbers (Table counterfjee revealed the transference of thin slivers of polymer. 1). The dominant mode of erosion is by brittle chip removal. This accounts for the high value of the 5 hour CVL. It should be noted that polyethylene terphatatate (Group III), like polycarbonate, has an extremely D1SCUSSIQW high resilience number. However, ft did not fail catastrophically. a) Cavitation erosion The polymeric materials of Groups I and II with resilence numbers between 45 and 76 display optimum behaviour (fig. 3). These polymers are generally The results of cavitation erosion tests Indicate that polymer"; fall Into 'leathery' and tough at room temperature and as such the accumulation of four classes of resistance with Nylons and polyethylenes showing excellent erosion damage is slow. There is a gradual transition between the performance. Heterogeneous polymeric mixtures of polyamides, polyethylenes properties of Group I and Group II, with the properties of Group I and polyacetals indicate the great potential of 'alloying' or compounding providing the optimum erosion resistance. A similar "U" shaped polymeric materials in order to optimise the erosion resistance. relationship holds between CVL and Shore Hardness. Scanning electron microscopy of the eroded surfaces demonstrated that the b) Sliding wear Group I materials fail by a tough ductile tearing mechanism whereas Groups II and III materials have a brittle appearance. Fibre reinforced and The measured values of the static and kinetic coefficients of the friction, filled polymers did not perform well and their eroded surfaces confirm that specific wear rates and relative wear rates for the six polymers tested Inhomogenefttes initiated erosion loss and rapid degradation. against 431 grade stainless steel are given in Table 2. In addition, mechanical and thermal properties are listed. It will be noted that ultra Although there art no clear relationships between cavitation erosion high molecular weight polyethylene (UHMWPE) clearly outperforms all of the resistance and *ny single mechanical or chemical property, there 1s an other polymers tested. It should also be noted that the coefficients of optimum region of resilience and Shore hardness for erosion resistance. 020x6 C20.7 - 6 - This suggests thit resistance Is obtained by compromising toughness and hardness. The combination of two or more polymers as an 'alloy1 may provide the optimum performance. Table 1 Cavitation Erosion Performance of Polymeric Materials b) Sliding wear resistance The preliminary results presented in this paper serve to Indicate the out- standing performance of UHHUPE. It also demonstrated the Inadequacy of Shr 7hr T, M Ft Trada Kaaa Ho. CVl CVL UTS "f i I >a HOt CRT roirw CO •c macroscopic mechanical properties to predict sliding wear resistance. (->> HFa (0) However, the crystal Unity and thermal characteristics of a polymer could Folyaalda 6.1 Nyloa 6.t A laro 0,05 20 264 80 90 66 REFERENCES Faly{aalda-l>41a) TOULOK it 10,07 13,31 . 340 . - 86 75 1 ralypropylaaa FU-FF u 11,20 - -27 160 26 234 76 6D Falyatilfaaa FAS-SOL ij 21,33 173 to 190 - 70 20 at m V 1. Joughln, N.C., "Potential for the Mechanisation of Stoping In Gold Mines'" Falyataylaaa FAS-FOT/I 35,57 63 to SO 256 78 17 86 103 V\ 1 taraphacalata u J. S. Afr. Inst. Min. Metal 1., 1976, Vol 76, No. 6. pp 285-300. Falytatrafluoto- Ttncm 33 10 .a - 256 20 250 38 36 1 athylaaa III rm * lot iroata - 34 21 - 296 - - 67 30 2. Hetthcock, C.C., "Cavitation Erosion of Materials". Ph.D. thesis, I960, FTTl • 231 Caraoa - )S 40 236 - - 67 41 rm * Caraaa * - 3t 30 - 256 - - 68 33 Univ. of Cape Town. (faaalta rm * ui CF • 1? 12 — 236 — — 61 33 1 rm • ax et - 31 33 - - - 6? 24 • 3. Lloyd, A.1.6., "The Sliding Hear of UHMHPE against Steel", M.Sc. thesis, Falyatatkaaa A VOTJUUXAK IS Cf -33 130 700 32 32 H 1 FOLTCAST 110 U CF -31 90 - - 21 25 H 1986, Univ. of Cape Town. c FOLTCAST MS 17 CF - -40 90 - - 32 45 H ralycartaaata 11 CF - 260 70 38 83 91 VV1 IV falyalaylidaaa KTKAI If CF - -41 - 44 39 78 76 H 4. Barletta, A., "An Assessment of Polymeric Materials and Surface Treated j rum 4* •oaoaolyaar Steels as Cavitation Erosion Resistant Materials", M.Sc. thesis, 1983, j . - caamlatlTa Tolaaa laaa ductlla Tg • glaaa cttaattla* taapacatvta aad 2a* ar4av (Laaa httttla Un1*. of Cipt Town. i traaaltlaa taaparatara •alt fH - altlaata taaatla atraaftk vary ductlla tlf - tarcattaga alaagaKlaa ta fraetura vary Vrlttla ACKNOWLEDGEMENTS (, - (aalllai Ml - late tf araala* aa aacaralaaa* af aeaaalag alaetrea aleraaeopy • Tha hlih ranhlnt of tha The work described was performed as part of a collaborative agreement between M - aaaala alatarad ultra kla> aalacaUr "aljht aolyaaida a.I aaapla can at aWI - alga daaalty palyathylaaa •lalaadlng t» tha rita of the University of Cape Town and the Research Organisation of the Chamber of *t • (laaa ftaia aroaloa lneraaaaa raaldlf Table 2 : Sliding Wtar and Physical Properties POLYMER UHMUPE NYLON 6 PVDF PTFE PC PSUL SPECIFIC WEAR 1 RATE irn^N"!/!* 1,134x10-3 3.4X10" 7,8x10-1 1,76 8,04 8.36 RELATIVE HEAR KATE 1 300 700 1600 7000 7300 COEFFICIENTS (S) 0.2 0,45 0.55 0,18 0,5 0,65 OF FRICTION (K) 0.1 0,25 0,35 0,13 0.4 0,50 3 DENSITY <9/c«t ) 0,94 1.13 1,78 2.10 1,20 1.24 THERMAL CONDUCTIVITY 0,4 0.29 0,13 0,24 0,21 0,26 fJL STRUCTURE Highly Mod-high Mod-high Crystal Anorph. Anorph. crystal. crystal. crystal. YIELD STRENGTH (MPa) 20 50 50 10 65 70 TOUGHNESS NOTCHED (J/nt) 100 160 200 130 700 69 HARDNESS (Rockwtll) R90 RUQ mo (Short) D6S 080 DSO 1 ELONGATION 600+ 200 25-400 250-400 100+ 75 C20.10 FIG. 1 : Scanning electron micrograph FIG. 2 : Scanning electron micrograph . of the cavitation eroded of cavitation eroded surface j surface of high density poly- of polyamide-imide displaying •, ethylene displaying a ductile a brittle mode of failure f tearing mode of failure typical of Group III. j typical of Group I. . M \ • / » '. 1 \ \ HSH.ICNCC SMOM HO FIG. 3 : The relationship between the S hour cumulative volume loss by cavitation erosion •nd tht resilience number of the various polymeric materials listed in Table 1. C 21.1 TEAR STUDIES IN RUBBERS J.A. Crobler, M.G. Huson and W.J. McOi) 1 tolymtr Chemistry, University of Tort Elizabeth J Stress concentrations in tearing I \ fchen * tear test Is performed on a nnt^hnH .iamplp thn applied fnrre concentrated at the tip of the tear. The additional strp.1.1 at the tip or •n elliptical hole is proportional to (a/r) , where a is the length of the hale and r the radius at the sharp end. In a rigid material the stresses at the tip or a crack increase Indefinitely as the crack sharpens. Rubber's Ability to even out the stress concentration by elastic deformation will frratly affect its tear resistance. The rubber in clone proximity to the tip or the tear shows higher elongations than in the rest of the tear piece *nd an aniaotroplc structure may develop across the tear path. Since the degree of strens concentration 'n highly dependent, on the geometry or the test piece the applied force will not be a direct measure of the force r#.jjired to tear the rubber but will difrer for different types of test pieces. T * aring energy *l«iin, Thomas and Greensmith published a series of papers on "Ruptur*? of >-ibt>er" in which they introduced the characteristic tearing energy T required ts produce two new surface areas. T is characteristic of a vulcanizate and ;• not affected by test piece geometry and can be expected to be a good measure of tne material's performance since it Is a measure of the work required to ctuse rupture. Ttoptrature and the rate of tearing have a pronounced effect on T, especially in caava where stick-slip tearing Is observed. Siactr et. al. constrained deformation of the legs or a trouaer tear pleoe *y«Ju«lng thin strips of metal onto each leg, leaving a narrow gap of rubber in which tearing could take place. - 3 - - 2 - C 21.2 C 21.3 The first mode of tearing is a form of stlck-sllp tearing, commonly known as knotty tear. It Is characterized by a tendency for the tear to circle around and propagate Tor a short distance againat Its original direction. The force Increases up to a point where a tear initiates and develops rapidly. The Metal strip force drops, until a minimum Is reached, nnd the tear Is arrested. The force then builds up again and the cycle repeats itself. The second mode of tearing is also a form of stick-slip tearing known as aau-tonth tearing. The cycle of force fluctuations Tollows the same regular pattern as knotty tearing but the major difference lies In the tear path which here propagates at an angle of 30° to 50°. Knotty tear dominates at larger The tearing energy can be calculated from the force F necessary to propagate •hl« separation distances, while saw-tooth behaviour becomes mc-e common as the tear. the reinforcing shims are moved closer together. No distinct transition •epiration can be defined. T = 2 F/d Sttady tearing occurs most readily when the shims are placed as close together where d la the saaple thickness (tear path). •• possible though temperatures and rates exist where smooth tearing will occur at any inter-shim distances. Modes of tearing Three modes of te.irlng ware observed with carbon black rilled stocks. Evluatlon of tearing energy tar lUck-sllp tearing the standard deviations in the tear initiation values FORCE CURVES •rt significantly greater than in the arrest values, and the former distri- bution is skewed, while a normal distribution is observed for tear arrest ••lull. Tot niled vulrunl7.At.ea niiaelhtf nl' the nhlm.i (url.hcr apart rauHR.i l.ht> tenr initiation values to increase while the tear arrest values are unaffected. far unfilled vulcanizates tear arrest values are likewise unaffected while Initiation values increase at low separations and thereafter remain constant. law*, tear Initiation energies are perhaps a reasonable Indicator of strength •wt «o not Met the criterion of an Inherent material property, because they •re affected by energy stored in sample extension, which in turn is affected ey rolvfte. Tear arrest values are independent of these factors and are TEAR PATHS e» inherent material property. C 21.4 C 21 . ' dlpated In irreveraable processes. Following Stacer et. al. we therefore choose to use tear arrest values In our studies but, because or difficulties in sample preparation when using The role of silica shim supports, we developed a different test piece which still complies with the requirements of preventing elongation of the material outside the it is common practice to Include silica in formulations to Improve tear tearing zone. strength. The mechanism whereby silica functions to increase hysteresis louses Is not known. Silica arreets the rate of vulcanization and therefore most likely the crosslink density and crosslink type. Silica undoubtably also pUys a physical role in reinforcement. Th« crosslink density of a vulcanlzate is normally determined by swelling in a suitable solvent. Fillers restrict swelling and, where the filler does not afftct the vulcanization reaction, this is easily corrected for. However, *fi«n the filler influences the reaction, as in the case of silica filled aulphur vulcanization, various parameters are needed to permit calculation of Factors Influencing strength IM true crosslink density. Most workers do not attempt a correction and plot In tensile strength the energy to break Eb la related to hysteresis loosen El properties vs apparent crosslink density. Figure 1 is such a plot- for the by the empirical equation t«ar strength or vulcanizates having different silica loadings. When allowance Is made for the restricting efrect of silica and carbon black on the Eb « l2'3 •welling true crosslink densities can be plotted »« In Figure ?. Eb depends on the crosslink density, crosslink type (C-C, mono-, dl-, poly- »t any crosslink density the difference in tear strength can now be ascribed suphldicetc), carbon black loading, carbon black type, ability of the material to th» chenlcal role played by silica (its effect on poly-sulphidlc cross- to crystallize on stretching, etc. llwal and/or its physical role. Experiments to evaluate these roles are in •r*cr«as. Tear strength is affectecttd by similar factors. Elaatically stored energy does not contribute to tearing energy and the contribution of the rupture of bonds is small. The major contribution to tearing energy comes from the energy spent In setting up conditions for bond rupture i.e. the energy dls- u X > • I ss c mm 1 il / o in ( /. 1 1 1 • • / I • 5 « a N \ as \ i : P. i i «OVni) MiflNMi* «>31 C2?.l THERMAL ANALYSIS OF RUBBER: A CHALLENGE TO CONVENTIONAL TECHNIQUES. hy O.C. VORSTFR ..I MttilltMl lyiiln !••• linl'i" liy IH i||VHI Application of the various techniques in the investiqation of raw materials used in the rubber industry is discussed. Ttw us* of thermomechanical analysis as well as differential •canning calorimetry in the study of the curinq reaction of rubbers are illustrated. Finally the use of thermal analysis for determininq the physical and compositional properties of cured elastomeric compounds are reported. Special attention is given to the determination of low temperature physical properties by means of dynamic mechanical analysis. New Rating Techniques for Processing Aids . Part II. General Purpose Rubbers: The effect of Process ing Aids on Production Rate W. Mofmann and A. Have land (0.0.G. Deutsche OelfabriW, Hamburg) Suatna r v Process ing aids repres ent essenc lal compounding ingre- d i ents whe rever rubber c ompou nd s are to bp processed *t higher t h rough put r a t e s , b u C with out negati v ely «ffeeti ng the physical propert i e s of the cured finished irt i c le5 • Similar to w hat has been f o u n d in earlier «tudip5 on specialty r ubber com pound s UPDM.NBR.Cfi), • 1 s o in ge netal purpos e rubber c ornpn i.i n d s processing aids, ac cord i n(r to their cbe n i c a 1 n a t ure, s how a differentiated • ( f i c i ency as a functi on of the shea r r at f conditions pr*va i 1ing in individu a I pr oc e s ping ope r iit ions • The or*sen t wo r k rev i ews suc h effec t s in nat ural rubber. C 23.2 C 23,3 - 2 - - 3 - 1. INTRODUCTION When convert ing NR compounds into finished rubber products by extrut ion or by compression, transfer or injection Processing aids as individually indicated * only in compounds •ouldint processes their flow characteristics are not for Che evaluation of curing characteristics and cured rubber always satisfactory for such process ing steps. Improved ptopert ies. processing properties are preferentially obtained by the addition of processing aids, i.e. specially developed chemical products which in small concentrations are able to substantially modify Che processing characteristics of ). EVALUATION OF PROCESSING AIDS IN NR COMPOUNDS rubber compounds without noticeably affecting mechanical cured rubber properties. The present work will describe the influence of selected processing aids on the processing characteristics of NR compounds under varying shear race conditions. 7. EXPERIMENTAL 2.1. Preparation of compounds The following products were added in amounts of 1; 3 and TN*»e results allowed to predict that Dispergum L should iBpart optimum processing properties to NR compounds for all 5 phr resp.to poorly processing, unplasticized NR compounds: technological processes concerned. DISPEKGUM L Zinc soaps of defined unsaturated fatty acids In HooneHooneyy viscosity tests (Fig.3 left), which are charcacter- DEOFLOW S Calciun soaps of defined saturated fatty acids at6 by low shear rates, Dispergum 1. brought about the most pronounced viscosity decrease. DEOFLOtf A Mixed fatty alcohols and fatty acid esters DEOSOL VE Aqueous emu 1 at ion of selected fatty alcohol esterc and higher molecular waxes The base formulation was as follows: SHR CV 60 100.0 Carbon black N 330 40.0 lft trmifer-cnoulding tests, which ng«in are characterized Stearic acid 0.5 %y intermediate shear rfltcii, DispprRum I, achieved nn inrrpasf • f injrctrd compound VP i Rti r Hy W X ( T nl> I «• I > . Thr i-voi nl I b PI'D O.U • •ting was in good ARCfenifnt with Fig. 2 • ZnO RS 5.0 Sulphur 1.5* Effect of processing aids (5 phr) on the transfer MBT I .0* moulding of a NR compound in a spiral mould at I5O°C DOTG 0.4* - 3 - Increase <%) Injected compound (g) Procecsing aid Rased on the results of the high pressure capillary rheom?r e itudies (Fig. I) Dispergum L was also pxpected to represent 2.50 none (control) the most efficient processing aid under the high shear rate 6 conditions of injection moulding operations. Rheovulkampter- 2.64 DEOSOL VE t < s t s , i.e. under simulated injection moulding conditions, 20 fully confirmed such a rat i it^ ( F i ji . -'i ) . Ac 170 C «nci 70 bar 3.01 DEOFLOW A the injected volune off the compouncomp d studied was increased 29 with 5 phr Dispergura L by nearl 3.09 DEOFLOH S 57 3.93 DISPERGUH !• It is sometimes discussed whether under injection moulding •: ond tions processing aids could impair the flowing of m et ing parts of thf i n j e r r p H ru b h *• r . Tli *» <:"mi'oiiniis «> i n j f fit JnlM a q|> 1 .In 1 ,1 .->,,,! , .,|r>l. | llo uillllrihr ..| In • * I t ii • 11» ti t • * t • , i . * . • t higher nltftr mF"* , Mi * » x p » '* t n I i n n ft I) i a i» »• r ^ u m 1. fdvHcs KVU li a il i a s t i L ft 1 increase o 1 L h i one* aote were fully con f i t tnett. I u the high iiicimue c«|>i 1 I m y ilov bility that the mould is filled without any faults rheoaettr tests illustrated in Fig. 1, Dispergum U allowed r«*p. flow cracks (Fig. Co obtain the lowest viscosity levels of all processing aids tested; in the extrusion experiments, energy consumption was •ott of all reduced by this product (10% at 3 phr, or \S1 at Fij. 6 illustrates the curing characteristics of a conven- 5 phr). tional NR compound with and without the addition of pro- c«»«in& aids. Dispergura L exhibits a retarding action on Uhen torque and back pressure were readjusted to match the th» onset of cure which is reflected in favourable overall level of the control compound by increasing the screw speed (low properties in transfer or injection moulding operations. (Table 2), the compound containing 5 phr Dispergum L impressed Tht other processing aids do not significantly influence the by an increase of extrusion output from 27 to 76 g/min (by icorch behaviour of the compounds. With respect to time to approx. 180 Z). Surface smoothness and edge precision of a lull cure, Deoflow S at b phr gave proof of an activating Mini-Carvey profile were improved from a C <* rating (control) tffwet, while any influence of the remaining products was to an A 6 level. ntgli g ib le . results in a Effect of DISPERGUM L on extrusion Table 2. !*»• ihorter cure time of the compound with Deoflow S is re- •ini extruder fttcted by the data for modulus, tensile strength and com- jr»«tion s*t . At 5 phr the pf fpet n f rhe ot hi? r prorfsiing « id* on the ph y «: i r 3 I .t in u"t sinni ( i^oul . Cnin|>miiwl With Cunt ml rni»|HiUllil 5 phr DISPKRGUM h no processing aid 50 rpa Qvtr the whole, Dispergum t unquestionably stiuwls (nil 'is ilu- 20 rpm %••( luited processing aid for NR compounds. Oeoflow R tends l# Hooi out from the plasticizer free black NR compound. The 64 Hioi out of Deoflow S from plasticizer confining compounds Torque (H«) 62 •as not yet b«en the subject of systematic research. Practi- 66 cal •iptrtence has shown that this bloom can be of advantage Back Pressure (bar) 58 f*t •«•y mould release, Deoflow A shows smaller effects and 76 M*»ol VE only very little effectiveness. Extrusion rate (ca/min) 27 - 6 - C 23.6 C 23.7 - 6 - High pressure capillary rheornetcr ioo°C NR + 5 phr process aid Die 20/2 mm With Che addition of 5 phr DISPERGUM L, the following im- provenents can be obtained in the processing of NR compounds: Mixing Mixing energy reduced by 17 X Transfer Moulding Injected volume increased by approx.WZ ^ M L [_ ] Extrusion Extrusion energy reduced by approx.152 Excrusion rate increased by approx.lSOZ Zl, iTTTiTrr" "]' TTTSHx j Extrudate quality improved from C4 to A 6 *"": ~TTTT7T' '- "'T " Injection Moulding Injected Volume increased by approx.600Z Injection time reduced (e.g, by 3031) f% I (nflucnc* of shttar rate on viscosity ol NR compounds (bar) Hfgh pressuf* capillary fheometpf at 100° C. Dm ?0/? mm, NR + 5 phr Processing aid LIJ 1 Control 2 Dgoflow* gum L S D«o!OlVE 2 3 4567(9 10' ••.'I » •* mwn on titf ud«d voium* of Nfl compoundi C 23.B C 23.9 (H) Extrusion energy lML,,4)Moo™v.«o.Ky <%, Mixing energy 1WC 100 - V 95- \ 90- V\ 8b 4 ' 1 —i r" phr procest ek 5. DeosolVE 3 Peollow S I.Control i.Oeolto.A » nf Sprir OispergumL on th« llowability in a spider mould (Men) Modulus 300% (MPa) Tensile strenglb (*ol Elongation al break vpp*««> ewe wme (tH) ••• i el <«0T isnore A) Hardne » DeoHowA 3 PeoHowS 4 DuptrgumL 5 OeosolVE ildt on IB-KWd vokm of NR eonipowHl* Fit* C24.1 PRESSURE SENSITIVE ADHESIVES - A REVIEW OF RECENT TRENDS Although we think of pressure sensitive adhesives as being a relatively new field of adhesive technology we find that they were first developed as far back as the mid nineteenth century. The invention of natural rubber pressure sensitive adhesives is attributed to Dr Henry Day to whom a U.S. patent was i ssued i n 1815. Such adhesive consisted of India rubber, spirits of turpentine, turpentine extract of cayenne pepper, lithage, pine gum and other ingredients. By the 1890's a natural rubber based, zinc oxide containing adhesive, had been developed for use on a fabric base as medical plasters. By the turn nf the century t«ra« qimnti tien nf planter* wf»r*» pr^rlw *ri, i-hi ,q h«tnu fchi* 'Mi 1 y ma for una -if pr"ft During the 1930fs electrical insulation tapes and self adhesive labels were produced and later a transparent tape on a cellophane f i! m was introduced. AlI of these were based on natural rubber and npiy the shortage produced by World War II prompted a look in other directions. Pnlyisobutylene was among the first polymers to replace rubber but all these replacements only made minor inr^ada into the dominance of natural rubber. AeryIic copolymerg were commerc ia1ly i ntroduced in the early 1950's and rapidly gained acceptance in the market. This product mix remained relatively static fnr several years with rubber/resin solutions being used for large volume applications such as self-adhesive labels and most tapes and the acrylics for specia li ty appli cations. Two factors i n the 1970's had a ma jor i mpar t <->n his status quo and changed It into the industry as we kn^w it t>->day. Firstly the oil crisis of 1974 started a spiral of cost increases organic solvents and other petroleum derived raw materials, And secondly, legislation in the U.S.A. and Western Europe or the allowable amounts of volati1e organi c compounds (VOC) emmi tted into the air. These two factors resulted in a search for Ies3 costly, regulatory-complying alternatives. As a result of this research and development effort, the nptlons of water-borne di spersi ons and IQQ% solid hot melts became more prominent. Today both acrylic "and rubber/resin types are aval table in three main f^rms: 3-)v»nt solution, water-borne dispersion «nd hot melt, giving the converter ample choice in selecting the right system. The pressure sensitive bond : Before considering the properties of the various types of P.S.A. we need to take m cursory look at the pressure sensitive bond itR*»lf. Adhesive theory tells us that molecules have a natural mutual affinity and exert force* of attract!on for each other. These forces are operative over very small distances and cloge contact is essential for *dh«sion to take place. H#nce an adhesive should wet the surfaces that it h*s to «dh«re to. Most adhesives are applied as fluids in order to ensure this intimate contact. PSA'« do not however follow this norm and their unique distinguishing character is their capability of forming an instantly uaeable bond Basic PSA types upon bringing a dry adhesive coated surface into contact with a free uncoated surface under light contact pressure at room temperature. There are many ways of characterising PSA adhesives, i.e. by their Tht« property which we call "tack" requires that the adhesive surface polymer type, their method of application and their properties. . makes an almost Intimate contact with the other surface. This "wetting" or liquid characteristic must be balanced with adequate Perhaps the best characterisation method is by the way in which thpy cohesion (internal strength) to form an effective PSA bond. Thus to achieve the "liquid/solid" property balance. sun up the PSA bond we can say that PSA's are adhesives with both solid and liquid characteristics and that they "wet" a surface (often a) Physical mixture giving rise to a heterogeneous system - e.g. forced) by the application of light pressure to form an instantly elastomers / resins / plastieisers. uaeable bond. This pressure "forced" wetting is the reason that they adhere reasonably well to solids with low free surface energies such Host rubber/resin solutions and hotmelt PSA's belong to this as polyethylene. group. Pressure sensitive adhesives are normally compared on three physical b)~ Physical mixes of polymers nf the same type - i.e. the parameters : "liquid/solid" balance is achieved by mixing different molecular weight grades of the same polymer. Peel atrength Shear strength Polyisobutylene types and polyvtnyl ether types are the best known Tack value of this type. Peel strength - is the adhesion - i.e. the force required to atrip c) Homogeneous copolymers :- utilising different monomers to give a label or tape from a substrate - normally the desired mobility / cohesion. measured in Newtons per 25mm. This system is that used by acrylic solutions, acrylic dispersions Shear strength - is the ability of the adhesive layer to withstand and acrylic hot melts. stresses acting in different directions. Normally recorded as a time to failure with a standard Recent trends have seen two of these basic types come to the fore : weight acting in shear on a unit area. (Standard lKg weight acting on a square 25mm by 25mm). 1) Physical heterogeneous mixtures : Rubber/Resin types. Tack - is the ability of the adhesive to adhere 2) Homogeneous copolymers : Acrylic copolymers. immediately to a surface. There are various standard tests ranging from - Since it is possible to get either of the two systems above in the three major physical forms we will concentrste on property variations i) rolling ball - which measures the distance due to chemical differences of the two dominant types. Each chnmistry travelled fnr a steel ball bearing after gives rise tr> both *rivAnf-ftgf»A urid rtImtrlvuntngeR. Rp|#Mi/-n f"r n traversing n n«fc Incllnn. gtvmi end unn munt rnkn rogMlnnnrA nf t.ttn rnntil r n let ti hnpnnmi l>y Mini Chemistry. ii) the pnlyken probe tack test. Rubber / Resin types iii) the "quick stick" tack test. (lubber resin PSA'e regardless of physical form, solvent solution or These tack tests are not sll relatable but they hotmelt, are formulated as physical mixtures of various components give good comparative data. each contributing a specific property. Thai* three factors often work againat each other, e.g. a soft film Rubber will-give good "tack" but poor shear strength and hence the service parameters are of vital importance. This component supplies the elements of flexibility, and cohesive •trength. Natural rubber, used exclusively until World War II is (till extenaively used either alone or in combination with various aynthetics. Other synthetics in use are SBH, poiyieobuty lene, butyl and block copnlymers baaed on Styrene and butodlene (SBS) and Styrene and Iaoprene (SIS). C24.4 C24.b N»tur»l rubber predominates in solvent based systems and the block copolymers reign in the hotmelt systems. Acrylic Cnpolymcrs Tacklfier* In acrylic PSA's the properties of tack, cohesion, specific adhesion, low temperature flexibility, etc. are obtained by a combination rf : A wide variety of additives are available to provide "tack". Amorphous resins such aa rosins, rosin esters, polyterpenes and synthetic i) Monomer selection hydrocarbon types are all used. Plasticisers are also used to aid ii) Degree of polymerisation (Molecular weight) "tack" development - these being oils or other liquid polymeric iii) Crosslink density (where applicable) materials. The mechanism of tack development when a tough non taoky rubber ia mixed with a brittle tack-free solid resin is not fully Fig (2) shows a list of monomers used in producing acrylic PSA's. understood. However certain work has indicated the presence of a Those on the left hand side contributing a softening effect (lowering reain-rich plaatioised phase at the surface of a pressure sensitive Tg) and those in the right column being used to promote hardness and film. Figure (1) shows a typical curve for a resin in a rubber based cohesion (raising Tg). adhesive when evaluated for degree of tack. FIG.(2) Mam monomers with a softening elect Comonomets win a haidoning, cohesion-promoting cttoct lower lg raise ig n Bulyt CH,-•CH-C-O-CH|-CMI-CH,-CH, *tr,\x:aoa CH.-CH-C-O-H acylala 6 O Mm.at.,uia 1.H,-(.M (. O t II, CH, -CH-C-O-CH,-CH-CH, O •ciytaio EXy< acn CH,-CH-C»N C24.6 C24.7 t 0) CO in 1 0i c. Li Ql 1 z 4- k c QO in Of! '0 L c c ra 1 ad e C 0. ra c E c. ra c to C OJ tn £ 3S t Acrylic polymers are usually completely saturated and normally no LO c 13 thi s c c u C to Goo d ! ink i Goo d cell s c o ts . antidegradants «re required as they are inherently inert to oxygen. a. 0) W z c Q' /J mc fl! tn Oi 4J c 1. x to I) Ul Qj re L. to e 4-' •a c > to •0 The major forma of acrylic PSA's are : O c ID 4. TD tn in X C a 0 ii c 0 to to c 3 (T 111 I o. cc tn a) water borne dispersions produced by emulsion polymerisation. t. to to c c tn VI 1 (0 u 4." t CJ re c 01 OJ I QO QO b) organic solvent solutions produced by solution polymerisation. u o § I X 4-' tn c c llen t I TIO N ee l len t bstanc e : k a 1 i . istan t u vents . his) . c) rubber aolids for use as hot melts. CC X 4CJ 3 in m 01 x u c •£• c •' c 3 6 o c 4-' a u 4-) w x bJ c ra tn tn 4) c The dispersion and solvent solutions are widely used at present but i- in U in V 0) re V 3 in •D U t X: a? "D in th« acrylic hotmelta have only limited economic penetration to date 8 tl "8 i n o O D a. c U a» U but will probably prove themselves in time to come. Q. £ tn to in to (0 — a: in -J ID 1 c 1 L. The basic differences in approach between rubber/resin types and ra c L, | to n acrylic types impacts on most areas of performance. The properties of -p o re pnl ; 0 r. X the major commercial types are listed in a comparative table (1). L. •c •o Ui 0 tn c c 1 m 8. c la r u a? 11 u &. L 1 c le n n c c I X c C c a- fl- tti to c tn p i c c 4-' Hu o c QJ a 0) c O L. re TO X 4J u c c 1) to u. u. tij c re c c a 4-' ro *-' L. c nj c c "D 4J u Ul C u (fl to ro 4J •§ w I/I 5 re i. 3 c ? X u. cn CL in to a t/1 W tr. 1 - z ]ar | 0) (0 s. TJ L- len t c „ len t in 17 yest e I ' RES ! :IO N c jola r i i vent s : " po l 0) JJ to 5 c 1 CC c 4- o ce f c ra re o JJ 4-' u c a C c CC w in u CO 8 tJ in in m 4; rs 0 JJ .o tin a. •» 1. Q' *i (n (i. Ul Ml fl' III 1» it tn u 1 re AD H SO L tr. H CL SH E to • • a if t ACRYLIC pnomwv HOTMIT SOLUTION LATEX HOTMLT DISPERSION PLASTICISIR Fair Fair Fair Fair Excel lent Good RESISTANCE (When properly "PTOAIATE OR formulated) OIL TYPE". iL Good MIGRATION / Fair Fair Fair Excellent Excellent STAINING 10. OPTICAL Fair/Poor Fair Poor Fair Excellent Fair CLARIW 11. ULTRA Fair/Poor Fair/Poor Fair/Poor Good/Excellent Good/Excel lent Good/Excel lent VIOLET (Can be upgraded (Can be upgraded (Can be upgraded RESISTANCE with UV anti- with UV anti- with UV anti- degradants). degradants). degradants). 12. AGEING Fair/Poor Fair Good Good (OXIDATION) 13. HEAT Fair/Poor Fair Good/Fair Fair Good/Excellent Good/Excellent RESISTANCE LOW TEMP. Fair Fair Fair Good Good RESISTANCE HOTI: The above table gives generalisations on the properties of each type and form. Many instances where a particular syst has been graded as "poor" can be upgraded by formulation modification. Conversely where a system has rated "excellent" it is implied that the specific property has been specially compounded for. UV : EXCELLENT an outstanding property or feature GOOD perform wall in this property nilTM »ajMI—1 iii-JHUIirtHMiMii. b) tj • •* app i 9 53»§-i c -a I 3 I ? " S 1 In — rt ,3 a a. •1 a. 0 a. is cn 0 n 01 bio n j o «•£. a 3 n n 3 i (ii er 1 3 • 0 O rt- T3 — a app l •a a 3- Her a 1 3 << 3 ~ » » 9 o. - A T3 3 3 3 !» 5S| - A <••+ ft » a ' a a fff a « a °5 £ 3 ail n • a a 2fSS i . 5 -ilS • O » c 5 ,3 < ^ 1 T 9 1 * rt rf ft to ^. o I Ms 3 ?? e» — ™ (o - s * * ? a !r *" CT s*. Q) Q) "5 2 A .-3303* ft T A ,-r — *\j 1 iB -• - M » 3 K B naaagg a u> 3 9 ft n 3 3" — C24.10 C24.ll S) Plsstlcissr Resistance I la) Low Temperature Resistance Solution acrylic* are the most successful being suitable for long The low Tg of rubber is changed when modified with high Tg resins tarn adhesion to plasticised PVC. Acrylic dispersions are also and hence rubber/resin types have a fairly high composite Tg and suitable but not to quit* the same degree aa solutions. special low temp plasticiaers sre needed to improve this - but with • loss of cohesion at room temperature. 9) miration / Staining Acrylic types generally have low Tg'e and remain flexible down to Thia phenomenon is not only concerned with the staining of about-35°C when the correct monomers have been selected Hence subatratei that labels or tapes are applied to but alao the fac acrylics are the obvious choice for areas such as deep freeze stock (papar) of the label or tape. Rubber based producta have labels etc. tendency to stain and need to be specially formulated t< counteract this. Acrylic baaed systems are auitable fo: Application methods also gives the converter a choice and table (?) applications aanaitive to this, e.g. labelling onto clothing below compares the relative merits of the three application methods. papar labels requiring fine print detail. 10) Optical Clarity Thle is required for Itemn minh *• nnfnty or «"lar protective film* applied tn glasa. In then* applic«tl"n« solution acrylli-n hold the dominant roll. 11) U.V. Resistance This property ia especially required when direct sunlight exposure is called for. Decola and protective films require this specific property and acrylics of all types perform well. 12) Aaeint / Oxidation Rubber resin types having unsaturation often in both the rubber and the reain are prone to oxidation and attention must be paid to compounding antioxidants into these types. Acrylics being generally aaturated polymere sre largely inert to oxidation effects. 13) Heat Resistance Rubber based hotmelts being mixtures of three or more components, generally have at least one relatively low melting point resin which results in ths whole mass softening on heat or at least increaaed Migration. Acrylic dispersions and solutions do not normally contain low melting point modifiers snd hence are less thermoplastic. Crosslinking types sre particularly useful where thia property is required. T * 1 L I ( 2 ) APPLICATION rVUWWTMS HOTMCLT SOLUTION DISPERSION Solids 100 % • 40 X Up to 70 X Content Viscosity Limiting factor for cohesive streng- Limiting factor for cohesive Non limiting molecular weight of p:'.y~ th (i.e. actual rubber content). strength. mer does not greatly influence disper- sion viscosity. Application Very fast Medium Medium Speed *_ 300 metres per minute • 100-300 m/min dependant on * 100-200 m/min dependant VT ability to remove solvent. ability to remove water. Coating Knife coater, multi roll systems. Knife costers, multi roll systems, Knife coaters, multi roll system;, Method gravure, metering bar. metering bar, gravure. Application 140» - 200°C Rnom temp. Room temp. Temp. Drying Not applicable. 90° - ISO0 90» - 150' Tunnel Temp. Limitations Transfer coating required for paper Flammable and necessity of solvent Necessity of heated drying tunned. or plastic films to atop migration drying and recovery. or distortion. 1 5 ?Sr Si c a S 1m 3- • m » en a 2 » n C m