Recent Advances in the Development of Silk-Like Polyester Fabrics
Indian Journal of Fibre & Textile Research Vol. 21, March 1996, pp. 79~89
Recent advances in the development of silk-like polyester fabrics
Pushpa Bajaj Department of Textile Technology, Indian In stitute of Technology, New Delhi 110016, India
Silk-like polyester fibres have been one of the most important targets for the textile industry in the present era. Key technologies starting from fibre engineering to finishing process have been illustrated for producing silky polyester fabrics with bulky hand touch and superior drape. Effects of polymer additives, delustrants, surfacta nts, etc. on alkaline hydrolysis of polyester fabrics for improving silk-like characteristics have a lso been highlighted.
Keywords: Alkaline hydrolys is, Bicomponent fibres, Micro-crator polyester, Microfibrcs. Shingosen, Silk-like polyester. Spinning techno fogies
I Introduction by simulating the characteristic features of silk fibre , Polyester fibre has conquered the leading position VIZ. among the three major synthetics because of its • The design of cross-sectional shape, excellent properties such as high strength, abrasion • Enhancement of drape characteristics through resistance, wash and wear, and wrinkle-free weight reduction of conventional polyes ter characteristics. However, polyester does have some fibres or by the development offine denier fibres. deficiencies, i.e. it is hydrophobic and oleophilic. Due and to this, 1t is easily soiled and accumulates the static • Creation of moderate bulk and soft handle. charge. Oily stains are also difficult to remove. History of the progress made in silk-like polyester Polyester fabrics are, therefore, not as comfortable as fibres is given in Table I and the technologies natural fibre fabrics. developed for the production of Shin-Go sen (Shin = On the basis of consumers' comments, Latta I has new & Gosen = synthetic fibre) in Japan are . also mentioned the following limitations of illustrated in Fig.l . synthetics: In this review, the va rious processes developed for • Unnatural hand and unfamiliar skin cqntact sensations, Table I- Histpry of the progress of silk-like polyester fibres9 • Unpleasant thermal sensations, • Lack of moisture absorbancy, Generation Properties Idea of technology • Clamminess of fabric in contact with skin, and Copy of natural Lustre Brightness • Static related problems. silk Drape Shape of cross-section ( 1964-) Rustle of clothes (trilobal, triangle) To overcome some of these problems, blending Copy of silk Fullness and softness Shrinkage-mix fibres touch Drape Structure of crimps with natural fibres, particularly cotton, gained a big (1975-) Delicacy market. An extensive work related primarily to Persuit for the Silky-spun like Air texturing polyester fabrics comfort has been published in aesthetic Naturality False twisting 2 excellent reviews - 6 in the recent past. From the properties Dry touch Thick and thin ya rns wearer trials using knit fabrics it was reported that the (1979-) comfort of polyester was substantially improved by Persuit for Lustre Tri-petal like cross- cross-section variations, pressure jet treatments and micro shape of Fullness and softness section certain engineering modifications of the ·polyester. cross-section Drape Microfibres Rustle of clothes Cross-sectional shape The Japanese industry has also made great strides (1983-) Naturality in improving the comfort and aesthetic properties of 'lk I'k I "Sh' " h b Aim for high Very nice tailored Development of po Iyester. SI - I e po yester mgosen as een sense and quality fini sh characteristics new polymer developed by different technologies? Various (1988-) Liveliness approaches have been tried to develop silky polyester 80 INDIAN J. FIBRE TEXT. RES., MARCH 1996
Shrinkag~-mix filam~nt ----i High shrinkage yarn t---{ Di fference in '"r---Fullness and High spQed spinning yarn fibre length softn~ss . Spontaneous extension
Polymer modification ------I Polymer with partic~s )----.Lu~e Brightness from catalyst residue Polym~r with added particles r:s-ur--:f:-a-ce-ro-u-g-:-hn-e-s.... s\.--L- Dee p co 10 ur Vi vid colour
Dry hand Special spinning ------1 Non-circul~r cross I'---{ Shape of (ross - 'ff--- Soft hand section section Conjugated yarn Rustle of (Iothes
Denier mix He Texturing ------1 False twisting 1----;rr;(o~m;;;m;;ii~ng~l;in;;;g-:-· -~~r\--~ Naturality Air tuturing dagree Afttr treatment ------1 Twisting l---'~S;;tr~u::-ct:t u:r:e--:o f;-""""":----+-~S t iff ness After finish (austic reduction fabrics Springy properties Fabric density Drape Fig. I- Fabric properties of Shingosen and key technologies SI LOOK ROYAL 51 L~ SILK been developed with triangular or trilobal I fI cross-sections. This resulted in lustrous polyester fibres. The appearance also changed from that of I 1 1\ ..... 1...- \ I / plastic to a silk equi valent. I" / '" -- I \../ PET fibres with a tripetal cross-section have also \V been developed to provide silky look. There is a " groove at the tip of each lobe oftrilobal cross-section. 1/ This unique cross-section is believed to bring the o 10 20 30 0 10 20 30 0 10 20 30 rustling sound to polyester fabrics when friction Tim~Jms occurs among them. The wave of rustling sound of three typical fabrics has been compared (Fig.2) . fr----- 'Sillook Royal' has, therefore, not only the lustre of o natural silk, but also a rustling sound similar to that of A-Sompl, 'tobric I the natural sil k. B- '" ie rophont c- W,ight , SOOt 14 em I Polyester fibres with petal-like cross-sections ha ve 0-"'0_ '1Oem Imin I been produced by conjugate spinning technologylo. Fig. 2- Wave of rustli ng sound of three typical fabrics In this process, small amounts of easily hydrolysable components are located at the tips of each lobe. During saponification or caustic treatment, this the production of silk-like polyester have been component gets dissolved and grooves a re formed. highlighted. Special emphasis has been made on the The width and depth of each groove can be controlled saponification or caustic reduction treatments for at the submicron level. producing si lk-like polyester fabrics. 3 Differential Shrinkage Polyester Yarn 7 2 Cross-sectional Shape - <) One of the technologies to bring out silk-like bulk The shape of a silk fibre after removing sericine and handle in PET is to use differential shrinkage during scouring is triangular. For imitating the polyester component yarn. Two methods have been triangular shape of silk fibres, polyester fibres have tried to produce different shrinkage levels in mixed BAJAJ: SILK-LIKE POLYESTER FABRICS 81 yarns. One is a parallel sort of mixture, just like the heat treatment. In the parallel structure, higher Quiana (nylon ya rn produced by Du Pont) and the shrinkage components form a core, and lower other is a se rial kind (Fig. 3). shrinkage components form waves or loops around The parallel structure is made by mixing fibres of the core. On the other hand, in the serial type different shrinkage levels either by using different structure, higher and lower shrinkage parts are polymer fibres or by mixing fibres of polyester drawn di stributed randomy in the yarn and there is no core at different temperatures. The serial type is produced (Fig.3). The resulting fabric from serial type by random heat setting along individual fibres during arrangement of different shrinkage level fibres fibre processing 1 I . The fibres shrink randomly with showed a more natural silk look than the parallel type. Uchida 12 has also demonstrated the role of TYPE PARALLEL SERIAL shrinkage in producing Shingosen. Fukuhara 7 from Mi Xlld Yarn of Rnndom Hrat- set Toray Industries has shown that for the production pf I'ETHOO D~rmt Shrinkage AmollJ Individual Fibre Lt'it I Shingosen, initially dry heat shrink process was tried and later the wet-heat shrink process. But, a double .. _...... - ...... shr'unk fabric appears to be closest to silky textiles (Fig. 4). It has comparatively hi'gher bulkiness and is YARN I------:--+------:::---~ .~. '"'-./ ...... /V..... more airy and soft. Sillook Sildew, produced recently, ~ ...... "'-.".... . ""'" is a double shrunk fabric with large waves or loops on ~ --v-..... J"'v... _. the surface of the fabric. For making double shrinkage fibres, the researchers have to first design the polymers by selecting a suitable comonomer and its content for accomplishing the desired shrinkage level. Degree of polymerization (DP) should also be controlled as a polymer with higher DP is likely to provide higher shrinkage. Parallel yarn str ucture After screening the polymer with a desired composition and DP, the fibres can be made from two , or more polymer components by the same spinneret from different nozzles. This kind of conjugate spinning provides fibres with in situ differential shrinkage. So, additional step for mixing fibres as Strial yarn structure discussed earlier is not required and the resulting mixture directly produced from spinning line is Fig. 3- Two kinds of shrinkage. Parallel and seri al yarn structures uniform. 4 Topical Finishes Finishes also modify the tactile, static and moisture Double shrin k type related properties of polyester fabrics. The ~I enhancement of polyester properties by treatment with aqueous sodium hydroxide was recognized soon 13 after the invention of polyester . Treatment of untextured yarn fabric with alkali produces softer ----, ...... '----- tactility with a less synthetic hand. A calendar, heat-set' and caustic soda saponified fabric was patented a few.years later as the treatment was said to ~ I~~ ____ ~D_r_y_-_he_a_t_s_h_ri~nk~tY_p_e__ ~_~ produce high fabric lusture without paper-like , l4 handle . Grey 1st 2nd Final Polyester undergoes nucleophilic substitution and fabric hQat-set ntat-set heat-~t scouring caustic dyeing is hydrolyzed by aqueous sodium hydroxide. The reduction hydroxyl ions attack the electron-deficient carbonyl Fig, 4 Shrinkage d'iagram of polyest .r fab ri c after caustic carbons of the polyester to form an intermediate treatment anion, 82 rNDiAN 1. FIBRE TEXT. RES., MARCH 1996 Table 2- Summary of alkalization processes SI.No. Materials Formulations Conditions Remarks Po lyester fa bric 0.3% NaOH in ethano l 50% pick up and Weight loss 2 1% stored 2 Po lyester fabric 6% NaOH in 5% ethano l -do- -do- 3 Kodel IV drawn 5- 15% sodium hydroxide lOOT, I h Weight loss 12-43 % PET fibre & OH < t-butoxid e hea t-set < sec. pro poxid e < methoxide < ethoxide 4 Terene fibres 5- 15% aOH 900 e I h Weight loss 1. 5 in . sta ple length 12 . 15-29.7 % 5 Trevi ra fabric Batch: 1.5-2 % NaOH I lOT, 20 min Weight loss 18% 90 g/m2 0.2% dispersing agent H.T. beam: 0.05 % accelerator Pad-ba tch: 19% NaOH R.T. fo r 24 hr Silk-like fini sh 0.2% wetting agent batching More unce rtain Continuo us: 19% NaOH 120 0 e I min 16-20% weight loss 0.2% accelerator Silk-like handle 6 Textured P ET fi lament 15% NaOH Bath ratio 10:1 Weight loss, % l.87 oz!ya rn 0.56 o r 0.87 % quaternary 30-60 min 17.5 Celenese Lauryl dimethyl benzyl 60 min 20.1 Fortrel 73 1 a moniull1 chloride 30 min 21 .9 60 min 24.4 7 Polyes ter 3% NaOH 95°C Weight loss 15 °;.) Silk:like effec t 8 100 % Dacron PET 10% aO H w e 120min Weight loss 10. 1% fa bric Strength loss 29'10 9 Li ght wei ght PET 4% aOH 90T. 60 min Weight loss 10.5-1 7.0% '68.5 g/m2 4% NaOH + I % accelera tor M:L::1:60 Strength loss 25% 10 Po lyester WY., NaO H lOOT. 15 min Weight loss 13 .74-14. 11 % I I Polyester crepe 10% NaOH IJOT Weight loss 100 g/m 2 n.1% s url ~ l c tant M:L::1:30 21-23 % after 60 min 20% after 15 min Strength loss 10-70% warp 12 Polyes ter Pad-ba tch WI. loss of tex t > flat > spun yarn 13 Po lyester Sodium trieth ylene gl ycolate (STEG» Weight loss Sodium d ie th ylene gl ycolate (SDEG) > STEG > SDEG > SEG Sodium ethylene gl ycolate (SEG) Flex. rigidity STEG < SDEG < SEG 14 Polyester textured yarn 3-5% NaOH 93-1 2 1°e Ih Weight loss 41 % Polyester textured fabric 5% NaOH 104T,. 1 h Weight loss 27 % Polyester 7. 5% Meth o no lic NaOH 2 1°C, I h Weight loss 26.8% 15 Polyester yarn 10 % NaOH 59T, 1-6 h Weight loss 18-25% 16 PET fibre, fabric 15 % Hydrazin hydrade 30T Weight loss 23 % or ethylene diamine 70T 15 % M:L:: I :20 17 PET & POY 10% NaOH 90T. I h Weight loss 20-80% fibres M:L:: I: 150 18 Heat-set delustred 2-8 mol NaOH 60T Weight loss PET fabric I % cet yl trimethyl 0-70 h 0-90% ammonium bromide ( 1% w/w) BAJAJ: SILK-LIKE POLYESTER FABRICS 83 Chain scission follows and results in the produc tion of hydroxyl and carboxylate end-groups. Table 3- Properties of polyester samples saponified by pad-steam techniques [Ca ust ic cone .. 150 giL; Steaming temp., 102°C] Sample Time of Weight Flexural Strength No. .steaming loss ri gidity loss (min) (%) (mg. em) (%) I 24.77 2 5 12.3 11. 99 7.3 The effect of caustic solution on a PET fabric 3 10 15.7 9.28 15.8 depends on the following parameters 15 - 19: 4 15 18.6 8.39 17. 1 5 20 2 1.1 6.55 26.2 • Concentration of alkali , • Time and temperature of alkali treatment, • Use of surfactants, 40r------, • Fibre type (composition and cross-section), and o~ • Heat setting. - 30 The fibre loses weight as the reaction occurs. Over a \II wide range of temperature, the relation between \II o weight loss and time or square root of residual weight ~ 20 and time has been found to be linear provided that a large exee ,; of alkali is used so that the reagent is not largely comumed during the treatment time. If an excess oT alkali is not used and its concentration decreases as the reaction continues, then the weight loss/time relation becomes exponential. Various conditions used for saponification and the weight reduction for polyester fabrics with aqueous sodium Treatment Time (h) hydroxide are listed in Table 2. It has been concluded Fig. 5- Rdationship between weight loss and treatment time for that the influence of temperature on the rate of the polyester fabric treated with aqueous caustic soda [( +) regular polyester, (0) regular polyester havi ng CTAM, ( x ) AMPET reaction is greater than that of concentration of alkali , substituted for regular polyester) which, in turn, is greater than that of time. Use of quaternary ammonium salts as accelerators for saponification has also been recommended6.20.2 1. In presence ofCEMDA and CTAM, weight loss of Samples hydrolyzed using 10% aqueous sodium 24% could be achieved only in 40 min at 130°C. hyd roxide at 60°C showed linear relationship Correlation between weight loss, strength loss and between the weight loss and the alkali treatment time flexural rigidity (Table 3) points out that the si lk-like (Fig. 5). Further, the addition of a cationic surfactant, soft handle of polyester can be realised22 when the namely certrimmonium bromide (cetyl ammonium fabric loses a weight of about 16 % and the flexural bromide) CTAM, or the replacement of PET with an rigidity reduces to about 9 mg. cm by treating with anionically modified polyester (AMPET) increases 15% NaOH at 130°C. the rate of saponi fication considerably. G awish and End group analysis of saponified polyester coworkers21 have shown that the rate of hydrolysis of indicates that with increasing weight loss of polyester crqe fabric in \0% NaOH (owl) at 130°C saponified polyester, the number of end groups of was vcry slow and it required six hours to the [COOH] increased and a value of 47.10 theoretical weight loss of 24%. However, with the equivalents/106g was achieved at 2 1% weight loss addition of different quaternary ammonium (Fig.6). The number for control being 32.8 surfactants as accelerators, the rate of hydrolysis equivalents/ I 06 g. The increased number of [COO H) coul d be enhanced significantly. The activity of the end groups after the saponification suggests that the quaternary ammonium surfactants was in the reaction of alkali wi th polyester is of hydrolysis with following order: scission of polyester chain molecules, resulting in Cetyl ethyl methacrylate dimethyl ammonium more number of [COO H) end groups, and confirms bromide (CEMDA) > cetyl trimethyl ammonium the mechanism of hydrolysis as shown earlier. bromide (CT AM) < oleyl bis-(2-hydroxylethyl) The data on saponified polyester indicates that cetyl ammonium bromide. both the accumulated charge (acceptance potential) 84 INDIA N 1. FIBRE TEXT. RES., MARC H 1996 48 Tahk 4 Eifeci ofsurl;lce saponi fica ti o n on electri c cond uctivit: 250 of polyester sampl es Sample Weight Acceptance II 2 46 No. loss potentia l (5) ( % ) (V) CII 200 I 200 240 44CDO ">" 2 1.61 190 90 ;J CII 3 5. 24 160 30 42 "'. > .. 4 13.5 1 11 5 2U ~150 Cl. o e;J 5 25 .1 4 90 10 .,c: 40 '" - '0 o c: Table 5- Fi ni shing stages of polyester fibre fa brics15 Cl. .. .. 100 38~ Sample A Sample B u 0 c: 0 W Loom sta te Loom SI a te E L....J Cl. .. Relaxati on in washer Relaxa tion in jet dyeing u 36 ~ ( I lOT. 20 min) ( I l OT. 20 min) -< ci 50 z Heat-setti ng in heat Heat-setting 34 setting unit ( 190' C 205) ( 190' C 20 s) Weight reduction Weigh t red uction 32 ( 16'Yo in 40 gi L NaOH) (25% in 40 gi L NaOH) °0~------~----~12~----~18~----~~24 Dyein g in jet dyeing Dyei ng in jet dyeing I I Weig~t Loss (~o I I I machine (no'c. 30 min) machine (130'C. 30 min ) 0. 29 0.31 0.33 0.35 0.37 Raising Ra isi ng Mo isture Regain, 'I, Fig. 6--Correlations between .weight loss. [COOH] end groups and acceptance potential in saponified po lyester • For peach lik e effect. hi gh solubility polymers or and 11 /2 (the time fo r half the accumulated charge to in orga ni c pa rticles are incorporated in PET decay) reduce with increasin g we ight l oss~ The value melt, which essenti all y solubilize or leach out to of acceptance potential red uced from 200 V for give pit effect on surface, thereby affec ting th e control sa mple to 90 V for the saponified sa mple (25% fee l and hand le of the fa bric. This radi ca l weight loss) and the di ssipati on time 11 /2 reduced fro m alterati on in the surface has been ensued by 240 s to lOs. The data also show that up to about 13% Japanese to prepare dry touch ya rn . Mi cro we ight loss the acceptance potential dec reased craters result in low convex-concave config u rapidl y to 11 5 V and with further increase in we ight rati on. loss to 25%, it dropped slowly to 90 V (Ta bl e 4). The • Samples appea r to lose we ight faster after reducti on in stati c charge accumulati on of the tex turing. For example, the losses in weight of alk ali-trea ted polyes ter may be attributed to the non-tex tured ya rn and tex tured ya rn when surface saponi fica ti on of polyes ter as indica ted by the treated with 5% ca ustic soda at 104°C for I h were inc reased nu mber of hydrophilic [COOH] and O H 36% anri 41 % respectively. end groups, wick in g and , to a limited ex tent , th e Matsudaira and Matsui 25 have al so studied the moisture regain . effect of various fi ni shing stages after the loom state on The effect of the ca usti c solution on a polyester th e fa bric handle. The di ffe rence between samples A fa bric depends also on th e fi bre type, fa bric and B is in the stage of relaxi ng and we ight reducti on constructi on, and hea t- setting conditions. Bright (Table 5). The effect of relaxing in a washer is expected fi bres with round cross-section lose we ight slowly to be greater than that in ajet dyeing machine. Overall , than delu stred fib res with multilobal cross-section. th e polyes ter fi bre fa bric is remark abl y softened and Reasons fo r thi s di ffe rence in the rate of weight loss fa bric handle by re laxa ti on, whi ch includes desizi ng, could be due to the fo ll owi ng: ~ h rin k i n g of fibres, and relaxing of in te rn al residual • For a give n linea r densit y, a multilobal fib re stress. Subseq uent we ight reducti on d ue to alka li wo uld have a large surface area than a roun d produces "efrecti ve ga p" between the fi bres/or ya rn s fi bre. and the splitting of fi bres. Tbe minimum amount of • The prese nce of delustrant may accelerate th e weight reduc ti on necessary to split fi bres is ex pected 23 24 we ight loss of the fib re . . to be approx. 10%. By usin g di scrimi na nt analysis BAJAJ: SILK-LIKE POLYESTER FABRICS 85 with the primary hand values as variables, a A method of forming a controlled microcrater on distinctive zone for silk-like and peach-skin type the fibre surface is proposed. The fibre pretreated by a polyester fabric can be found. ;pecific resist is exposed to a laser beam and then Sodium hydroxide treatment reduces electrostatic treated again with chemicals. This process can control charge generation from 280 V to 100 V and the halflife the dimensions of voids such as depth, length and from 5 to 2.5 s. Sol brig and Obendorf26 have reported height, and their density. the considerable weight loss after saponifying A blend containing PET and 4% BaS04 (~ 2%, avo polyester fibre containing 2% Ti02 (Fig.7) and the jiam. :::; 9 /-1m) was melt spun at 1800 m/min to give pitting on the surface, obsefved through SEM, mainly 290% elongation at Kuraray Co. The fibre wa~ used as axiall y oriented a long the fibre surface. Treating sheath and later on textured by Taslan process and polyester fibre with 10% aq. NaOH at 100°C (by causticized to give 30% weight loss. steaming) for 45 min produced hygroscopic polyester For improved lustre, polyester fibres containing :::; fibre. 0.04% inorganic oxide particles and having In another study, a wide range of particles have been birefringence 0.03-0.08 were draw twisted for ~ 0.15 s used for creating microvoids on the fibre surface. A at 130-170° and then untwisted to give textured yarn 2 7 common method is to remove microparticles blended with very good lustre . in the polyester polymer by a lkali treatment. By The effect of BaS04 on the extent of saponification 28 applying this method to various polyester fibres has a lso been studied in o ur laboratories . As the containing differt'nt types of particles, fibres with treatment time and concentration of NaOH various patterns of voids on surface are obtained. progressively increased from I to 2 h and from 5 to Originally, this modification was carried out to give 10% respectively, the loss in weight of the polyester depth of colour. fibre increased from 3.03% (Po, 5% NaOH, I h) to 15.2% (Po, 10 % NaOH, 2 h) at 90°C bath 30 temperature. It can be seen from Table 6 that PoSi loses more Dull 25 weight over Po or P oSiF 5. This is perhaps due to the Bright formation of sodium si licate in the presence of alk ali. ~ Serri().jll 0 due to si li cone oil coating on PET, which seems to - 20 Clear accelerate the saponificat ion process. The reduction '" in diam.is a lso maximum in Pll Si fibres. .3'" 15 ..... After hydrolysis, elongated pits, ori ented in the ~ direction of the fibre axis, on the surface of Pll Si F " . ~ 10 sample were noticed. However. unfilled fibres did not '" ~ show any pits. It was found that the size of the pits 5 depended on the length of expowre to alk ali , while the number of pits depended on the concentration of OE-__L- __L- __L- __~ __~ __~ ____~ BaS04 in the fibre (Fig.8). As the treatment time and alk ali concentration increased from I to 2 h and 5 to Treatment Time 10% respectively, the pits enlarged mainly in the fibre Fig. 7-Change in weight of clear. bright. semi-dull ai1d dull PET axis direction. Longer treatment increased the size of yarns over 6 h of treatment with \0% NaOH solution the pits without changing their numbers. H ydrolytic Table 6-Change in weight and diameter of BaSO.-filled polyester fibres after saponification Sample 5% NaOH \0% NaOH I h 2h I h 2 h Wt loss Diameter Wt loss Diameter Wt loss Diameter Wt loss Diameter % ~m % ~m % ~m '1. ~m Po 3.03 39.4 5.0 38.9 8.4 38 .2 15.2 36.8 PoSi · 6.4 . 38.6 8.3 38 .3 13.4 37.22 22.2 35 .2 PoSiFs 4.{)5 39.1 5.52 38 .8 10.5 37.94 18.8 36.04 Diameter of Po (unsaponified). 40 ~m; PoSi - si lane coated; PoSiFs - 5% BaS04-fi lled PET 00 0'1 oz ); z ;- ::!l 0:1 "tTl rri >< :-i yfii') !:» (j ":t '" 0\'" Fig. 8- SEM of saponified BaSO"-filled PET [( a) No rm al PET, (b) PET fill eu wilh 5% B"SO", (e) PET tille d wilh to'Yt, B"SO", (d) Saponified norma l PET. (e) Saponified PET ti lled wi th SU!c, 8:ISO", alld (n Saponified PET fi lled with IO'y' , 13aSO"1 BAJAJ: SILK-LIKE POLYESTER FA BRICS 87 Table 7- Tensile properties of saponified po lyester fibres [NaOH conc .. 5%] Sample Treatment time code I h 2 h Tenacity Strength Breaking Modulus Tenacity Strength Breaking Modulus cN /tex r<: tention elongation N 'tex eN/tex retention elongation N/tex % % % ala P" 38 96.5 2 1 10 36.3 92.1 19 9.5 P"Si 34 87. 1 IH 8.3 29 .5 75. 6 14 7.8 P"SiF, 36 97.0 18 11. 2 35. 1 94 ..8 17 10.6 degrada ti on of the polyester begin s at the surface of the fibre and continues until a BaS04 particle is .5:.'/ exposed (Fig.8). Pits appear to develop from '~ ': ..:, preferential hydrolysis of polymer around the fill er particle, locations where alk ali can diffuse more easily P Olyester..q;~t.". . :rf~(/ " due to hyd rophilic nature of the fill er. This action .h J. • leaves an axially-oriented elli ptical voi d around the • . .,ft:·{.. , .• ct> / - .. filler particle, forming an entry point for the alk aline . .l "'f... ,' 'i"f solution to attack polymer beneath the original :J!.t!Jzo surface. Possibly, the drawing process used in th e Sil ica ~.i"' ~ f R','N' production of fibres ca uses the pi ts to be elliptical. $;Jji.~ New ~("~ surface ~. Alkaline treatment 5 Tensi le Properties The tenacity, breaking elongati on and initial Fig. 9- Pieture of the fine concave a nd convex mechanism after modulus decrease wi th the increase in weight loss due alkaline treatment to sa ponification (Table 7). Tensi le strength retention in Po fibres is 92 % and 73.6% at 5% and 15.2 % weight Sol-dispersed silica as selected particles loss res pectivel y. However, under the same condi Pro[)enics Silica Pol yester tions of treatment the percentage strength retention So lubilit y ratio a gainst alkali 80 for P"SiF5 samples is slightly better, i.e. 94.8% and Index of refract ion 1.55 1.62 75.4% at 5.5 % and 18.8% weight loss due to Oi 1.2 r------,15 Table 8- Moisture regain, st rength retention and the durability 33 ~~-. ------r_ to washing of the chitosan-treated fabrics '" Micro-crater. polyu.ter ... Fabric Add-on Moisture Strengt~ Durability to -E (%) regain retention washing -0 0 .c; 1.0 16 (%) (°lc,) (weight remained, %) E'" ....>- Untreated 0.4 100 co '" '"OJ Chitosan-treated 6.6 I.7 75.6 2.5 c: -'" without curing 15.3 2.4 87.6 2.3 d 0·8 17 u ~ d Chitosan-trea ted 6.4 1.6 138 .0 95.0 .q: co with curing" 16.7 2.4 150.0 84.4 QI u d ..&-._ ._ ._ . --0 Alkali treatment: 10% Sodium hydroxide, 90 min, 60' C ~ ::> Curing condition: 130' C, 90 min Vl .-:: ...a.-r..&. -..vt-...... __ ------r J. Regular polyesf~r application and the nature of amine. Amide formation results in chain scission. Amines were found to react and attack amorphous as well as Alkaline Weight Reduction (%) crystalline regions. It appears, according to Zironian, that the weight loss/time curves are affected by the fine Fig. I O-Relationships between the surface area, blackness and structure of the polymer and the location of attack. a lk aline weight reduction (Black dyed Georgette fabric) 7 Aftereffects primary particle diam.45 J.1m and average secondary o Deterioration in tensile properties particle ciiam.350 J.1m with polyacids to form PET, o Broadens dye class for PET melt-spun and drawn to give trilobal fibres with silica o Improved wettability content of 0.01-0.4%. o Oily soil release improved For rapidly hydrolyzable PET fibres, melt blending o Good antistatic property of PET with 2-10% sulfo containing aromatic diol(l) o Increased moisture regain 3J o Cracks developed on fibre surface was carried out by Teijin Ltd . o Brittleness increased o Flex life decreased H-t 0 C2H4)mO ----@{-OC C2H4 0 H o Shift in endothermic melting peak to lower ~ temperature o Improved pilling resistance. S03 M ( I ) . References A woven fabric of the fibre showed weight I Latta B M, Clothing com/ort: . Interaction of thermal. ventilation. construction and assessment faClors (Ann Arbor reduction rate of 41 %/h in boiling aqueous NaOH. Science, Ann Arbor, Michigan, USA), 1977, .33-35 . Ester Co. Ltd has developed polyester fibre with 2 Slator K , Text Prog . 9(4) (1977). superior softness and gloss by dispersing 0.5-20% 3 Yoon H N & Buckley A, Text Res l. 54 (1984) 289. EPR in PET fibre. M~lt kneading was carried out and 4 Yoon H, Sawyer LC& BuckleyA, Text Resl . 54(1984)357. 32 5 Zeronian S H & Collins M J, Text Chern C%r. 20(4) (1988) then spun into fibre • 25 . Matsukawa et al. 33 have shown the recovery in 6 Matsumoto M, Indian Text l . (Jan. 1991) 'J4 . tensile strength of alkali-treated polyester fabrics by 7 Fukuhara M, Text Res l . 63(7) (1993) 387. R Wada 0 , 1 Text Inst . R3 (1992) 322. subsequent treatment with chitosan (Table 8). 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Jap Pat 06,313,214; Chern Abs/r, 122 44-45. (1995) 1902601. 24 Solbrig C M & Obendorf S K, Text Res J , 61 (1991) 177. 33 Matsukama S. Kasai M & Mizuta Y. Sen-i-Gakkaishi, 51 (I) 25 Matsudaira M & Matsui M, J Te'x t Inst, 83 (1992) 144. (1995) 17.