Sıbel Sardag, Ozcan Ozdemır, The Effects of Heat-Setting *Ismaıl Kara on the Properties of /Viscose Department of Engineering, Uludag University, Blended Görükle, Bursa 16059, Turkey E-mail: [email protected] Abstract 30 tex and 20 tex bobbins consisting of 67% PES - 33% viscose were subjected to heat- *Can Textile, setting at 90 °C & 110 °C, and under a pressure of 630 mmHg in order to investigate the Corlu, Tekirdag, Turkey effects of heat-setting conditions on the properties of twisted yarns. Both heat-set and unset yarns were dyed. The tensile strength properties (tenacity and elongation at break) of each yarns were measured before heat-setting, after heat-setting and after . The inner, middle and outer sections of the yarn bobbins were measured with a spectrophotometer to find differences in color. As a result, heat-setting and dyeing processes were found to be effective in the tenacity and elasticity of yarns. Key words: heat setting, twist setting, twisting, temperature, polyester (PES), viscose, tenacity, work of rupture.

ventional systems and operate under ral qualities, brightness and comfortable vacuum with saturated steam are used wearing property of viskose . In ad- in conditioning and heat-setting. With dition, viscose fiber has a high elasticity the aid of steaming in these systems, when compared with fibres. When yarns are conditioned or heat-set with used together with PES , viscose saturated steam under vacuum [3]. fiber gives a more hormonious blend as regards elongation at break [8]. The Heat-setting process, a treatment n Introduction with steam under vacuum, improves Since the tenacity of the wet cotton yarn efficiency and quality in and is higher than that of dry ones, cotton Moisture in the atmosphere has a great plants by reducing yarn ten- yarns have a higher tenacity under high impact on the physical properties of tex- sion, softening yarns, moisturising them moisture [9]. Studies concerning heat- tile yarns and fibres. Relative humidity homogenously, eliminating electrostatic setting are limited in literature and nearly and temperature decides the amount of effects and reducing fly and dust [4]. all of these studies are related to cotton moisture in textile materials. Exposing because of its positive reactions against yarn to high moisture during produc- Unset yarns squeeze bobbins during moisture. For this reason, the current tion generally yields negative results, as dyeing with a pressure from the out- study which has been performed on the well as being undesirable for technical side section towards the inside section, heat-setting of yarns consisting of PES/ processing. On the other hand, a high as a consequence of which bobbins get viscose is expected to make a contribu- degree of moisture adequatelly exposed deformed. The higher the temperature tion to textile literature. to yarn improves its physical proper- of heat setting is the less the bobbins get ties and enables the standard humidty deformed [5]. Improper heat setting is of yarn to be reached. Yarns with lower considered to be a factor which increases n Experimantal moisture content than the standard value skewness in weaving, a situation in In this study, 30 tex and 20 tex carded result in monetary loss in sale. Therefore, which warp and weft yarns cannot be tied yarns consisting of 67% PES and 33% conditioning and heat-set is to provide together with a right angle, although they viscose were used - the linear density and an economical device for supplying the are straight [6], and it increases diagonal staple length of PES fibres were 1,6 dtex necessary moisture in a short time [1]. run in knitwear [7]. and 38 mm respectively, and the linear density and staple length of viscose fibres Each step in the manufacturing proc- Since saturated steam used in heat-set- were 1.7 dtex and 39 mm, respectively. ess, such as twisting, , weaving, ting provides man- made fiber with good Yarns were wound onto bobbins with knitting etc., causes tension in fiber and thermal conductivity, steaming processes a Schlafhorst Autoconer 238 machine. yarns. Yarns tend to snarl in order to re- under vacuum make it possible for bob- These yarns were subjected to heat-set- lax themselves and get rid of this tension. bins to shrink homogenously in every ting under 630 mmHg pressure and at Tension and snarling are likely to lead to section. The yarns of such a bobbin are temperatures of 90 °C and 110 °C with problems in the following manufactur- dyed homogenously without causing a machine working in compliance with ing processes [2]. The purposes of con- stripe effects or colour differences be- the direct vacuum steaming system of ditioning and heat-setting (twist-setting) tween the inner and outer sections of the the Welker Company. The cycles below are to relax yarns, to prevent them from bobbin [5]. were followed: snarling, to enable them to be worked n Pre-heating : 45 °C efficiently in the following processes and The blend consisting of PES and viscose n Vacuum : 630 mmHg to fix yarn-twisting. Today, besides con- is used widely in the . n Heating : 90 °C (10 min), ventional system, other systems which This type of blend benefits from the high 110 °C (20 min) can eliminate the downsides of the con- strength of PET fiber and from the natu- n Vacuum balance : 500 mmHg

50 FIBRES & in Eastern Europe October / December 2007, Vol. 15, No. 4 (63) FIBRES & TEXTILES in Eastern Europe October / December 2007, Vol. 15, No. 4 (63) 51 Yarn bobbins were dyed in a Mini-HT As can be seen in Figure 1, the heat-set laboratory-type bobbin dyeing machine process brought about a considerable produced by Dilmenler Machinary In- improvement in the tenacity of yarn. The dustry. The dyeing process was carried rate of increase varied between 15% and out according to the conventional two- 19.9%, depending on the yarn count and step dyeing method. PES fibres were first temperature of the process (Table 1). The dyed with disperse dyes at 130 °C, and tenacity of yarns, subjected to heat-set they were then subjected to reductive showed a decrease of 4.4 – 11.3% after clearing at 75 °C. In the second step, vis- the dyeing process; however, their yarn cose fibres in the blend were dyed with tenacity was still higher than the tenacity reactive dyes at 80 °C, and then after- of unset yarns. Fıgure 1. The effect of the heat-setting process on tenacity of yarn. treatments (washings) for reactive dye- ing were performed. Finally, the bobbins In textile material science, a classic and were dried on a radio frequency drier. fundamental problem is the connec- tion between the tensile properties of Yarn count, twist and tenacity measure- fibers and yarns. A yarn is a complex ments of the yarns were taken before system made by a fibrous structure, i.e., and after heat-setting and after dyeing. a bundle consisting of a given number of Before the measurements were taken, all single fibers; this bundle, after twisting, the yarns were kept under standard con- becomes a yarn. [11] The improvments ditions. (at 20 °C ± 2 °C and 65% ± 2% observed in the tenacity of PES/viscose relative humidity) Yarn count measure- yarns after heat-setting can be an attrib- uted to the effects of this thermal process ments were carried out in compliance Fıgure 2. The effect of the heat-setting with ISO 2060. Yarn twist measurements on PES fibers, which constituted 67% of the blend. The physical and chemical process on elongation at breake of yarn. were taken in accordance with ISO 2061 properties of fibers such as dye absorp- on a James H.Heal twisting meter. Te- tion, strength etc. are close related to the The heat-setting processes increased nacity measurement of all the yarns was structure of non-crystalline sections. Due the values of yarn elongation within the performed in accordance with ISO 2062 to the temperature of the heat-setting range of 5.4% and 8.7%. Since cellulose on Uster Tensorapid 3. applied, the rate of crystalline sections, macromoleculles, which form regener- the average distance between crystalline ated cellulose fibres, are short, the att- A spectrophotometer was used to find centers and the number of bonds between raction between these macromollekules out whether inner, middle and outer macromolecules in fibres increased, as a was not very strong. Therefore, when a sections of the bobbins had any differ- consequence of which the degree of ori- force parallel to the fiber axis was app- ences in colour. Measurement was made entation in fibres increased, causing an lied to the regenerated cellulose fibers, with an observational angle of 10° and improvement in the yarn tenacity [12]. bonds between the macromollecules with D65 illuminant, using the CMC 2:1 weakened, causing the fibers to break. equation [10]. To investigate the effects The slight decrease in the yarn tenacity Breakages of wet regenerated fibres took of heat-setting and dyeing properties on after the dyeing process was something place more easily because of the swell- the yarn tenacity and elongation at break, expected. This fall arose from the fact ing and sliding effects of water [12, 13]. t tests were performed at 5% (0.05) and that especially viscose fibers and partly Consequently, the elongation values of 10% (0.1) level of significance . PES fibres get slightly damaged- dur the wet regenerated cellulose fibers were ing reductive washing with NaOH. The noticeably higher than those of dry ones. n Results and discussion t-tests we performed show that heat- sett- Generally, the tenacity values decreased, ing and dyeing process affect the tenacity but elongation values (%) increased, The effects of heat-setting at 90 °C and of yarns. while these fibres were wet [9 - 13]. The 110 °C, and of the following dyeing proc- increase observed after the application of ess on the tenacity and elasticity proper- The effects of heat-setting at 90 °C and heat-setting in the elongation (%) values ties of 20 tex and 30 tex yarns are given 110 °C and of dyeing on the elongation of the yarn fell a little after the dyeing in Table 1. % of yarn are given in Figure 2 . process. However, the elongation values (%) obtained after the dyeing process are Table 1. Changes in yarn tensile strength properties after heat-setting and dyeing process. still higher than those of the unset yarns. The heat-setting process improved both Yarn properties After heat-setting After dyeing the tenacity and elongation (%) of these Parameters (Changes as %) (Changes as %) yarns. The t tests performed indicate that 30 tex 20 tex 30 tex 20 tex heat-setting and dyeing processes aff- 90 °C 110 °C 90 °C 110 °C 90 °C 110 °C 90 °C 110 °C ected the elongation (%) of the yarns. X 15.0 19.9 16.9 15.7 -4.4 -4.8 -11.3 -9.5 Tenacity, cN/tex CV % -14.3 -15.8 13.6 12.3 9.3 16.7 -6.9 -5.5 After heat-setting, the work of rupture Elongation at X 8.9 8.7 8.7 5.4 -3.0 -5.7 -6.0 -3.7 values of the yarns increase by 12 -15%, break, % CV % -20.7 -25.5 11.8 8.8 3.2 11.4 -7.7 -6.5 and, as a result of this, these yarns were Work of rupture, X 15.0 12.4 13.6 12.9 -4.3 -5.5 -4.8 -4.5 expected to show a higher cN CV % -13.9 -14.1 18.7 16.9 4.3 8.9 -8.8 -8.0 in the following process. These values

50 FIBRES & TEXTILES in Eastern Europe October / December 2007, Vol. 15, No. 4 (63) FIBRES & TEXTILES in Eastern Europe October / December 2007, Vol. 15, No. 4 (63) 51 ven into fabrics, snarlings cause faulty weakening of intermolecular ties fascili- and lower grade fabrics. Therefore, yarns tate an easier shift of molecules. In this needs heat setting in order to prevent un- case, the moisture acted as a lubricant. twisting and snarling [14]. Heat intensified the motion of molecules, reduced the forces of intermolecular Twisted yarns which were subjected to effect and their shift became easier. As the setting processes underwent some twisted yarns were heated in swelled changes in their interior structure, as a state (i.e. stressed state) the macromol- result of which resilient and elastic de- ecule shift occured quicker. formations were able to take place and Fıgure 3. The effect of the heat- setting process on work of rupture of yarn. the macromolecules of the yarn able to If twisted yarn swelled in a free state, change from a curved to a straight shape. its cross section increased and the ori- At the same time, the monofilaments entation of yarns remained unchanged, decreased by 4 - 6% after the dyeing could have become somewhat elongated process (Figure 3). Increases obtained a shrinkage of yarn could be observed and come to occupy a position in which after heat-setting at 110 °C were lower with a certain reduction in its strength. than those obtained after heat setting at they would follow a helical path without The yarns were stretched in a swelled 90 °C. The increase observed in the work stresses, as the elastic forces would be state to increase their strength [14]. rupture value of the yarns decreased a suppressed. little because of reductive washing in the The setting of twist in case of polyester dyeing process but this value was still The straightening of macromolecules led yarns was accomplished only by heating higher than that of the unset yarns . to yarn elongation, but elastic forces tend- but without swelling of yarns. By mois- ed to shorten them. As a result, there was tening the twisted yarns, having a stabi- Work of rupture can be considered to be the possibilty that yarn length might re- lised twist in the free state, the reverse the working capacity of the yarn. Work- main unchanged, but due to the suppres- process of deformation relaxation took ing capacity is the most important value sion of elastic forces, the stresses in yarns place which imparted the capacity of which showed the yarn performance could have almost disappearred [14]. spontaneous untwisting to the yarn[14]. in the following processes. The work capacity of a yarn corresponds to the Viscose yarns featured high hygroscopic- Changes in the yarn’s linear density and area below the stress-strain curve and ity, good adsorbency, and swelling. twist as a result of heat- setting are given expresses the behavior of the yarn dur- Swelling of viscose yarns was accom- in Table 2. ing subsequent treatment. Therefore, it is pained by an increase in yarn cross sec- suggested that increases in the tenacity tion by 25 - 65% and an insignifficant As it can be seen in Table 2 slight chang- and elasticity of the yarn should not be increase by 3-5% in fibre length [9, es took place in the twisting values of the assessed individually, but together with 14]. The cause of this change is that yarn after heat-setting. This process fixed its work capacity [3]. cellulose macromolecules which form yarn twisting and eliminated yarn liveli- viscose fibres shorten and the rate of the ness, thus preventing snarling. Thus, we The CV % values which belong to te- amorphous part of fibre is high [13]. The were able to enhance the performance nacity, elongation and work of rupture of 30 tex and 20 tex yarns are given Table 2. Linear density and twist measurements of 30 tex and 20 tex PES/viscose yarns in Table 1. While 30 tex yarn showed after heat- setting. decreases in tenacity, elongation at break Yarn properties (%) and work of rupture, CV % values Parameters 30 tex 20 tex after heat- setting at 90 °C and 110 °C, Heat-set at Heat-set at Heat- set at Heat-set at 20 tex yarns showed increases in these 90 °C 110 °C 90 °C 110 °C CV% values. The tenacity of the yarn tex 29.4 29.4 19.6 19.6 decreased and tenacity CV% values Pre-heat setting t.p.m. 963 959 960 964 increased as the yarn got thinner. Tenac- tex 30.1 30.4 20.0 20.2 ity CV% values of 30 tex yarn were Post-heatsetting t.p.m. 940 930 934 935 tex 2.4 3.4 2.1 3.1 increased after dyeing, however they Changes as % were lower than those of the unset yarns. t.p.m. -2.4 -3.0 -2.7 -3.0 The tenacity CV% values of 20 tex yarn tex 31.2 31.6 20.6 20.8 Post dyeing were decreased after the dyeing process, t.p.m. 919 915 920 922 tex 3.7 3.9 3.0 3.0 but they were high when compared with Changes as % the values obtained before heat-setting. t.p.m. -2.2 -1.6 -1.5 -1.4

Twisted yarns tend to untwist. When Table 3. The results of color measurements made on 30 Tex and 20 Tex PES/Viscose yarns. twisted yarn tension is slackened (which occurs at their unwinding from pack- Unset, ΔE Heat-set at 90 °C, ΔE Heat-set at 110 °C, ΔE Yarn ages), the yarns usually get coupled as count inner- middle- middle- inner- middle- middle- inner- middle- middle- loops and twisted in reverse direction outer outer inner outer outer inner outer outer inner forming snarls which lead to breakeges 30 tex 0.18 0.19 0.18 0.14 0.15 0.17 0.19 0.19 0.17 during furter yarn processing. When wo- 20 tex 0.16 0.18 0.18 0.16 0.16 0.17 0.15 0.20 0.21

52 FIBRES & TEXTILES in Eastern Europe October / December 2007, Vol. 15, No. 4 (63) FIBRES & TEXTILES in Eastern Europe October / December 2007, Vol. 15, No. 4 (63) 53 of the yarn in the following production For furter studies it will be useful to processes by means of twist setting. investigate yarn liveliness and the re- lationship between yarn liveliness and U N I V E R S I T Y The heat-setting of man-made yarns un- heat-setting . der vacuum with saturated steam, besides OF BIELSKO-BIAŁA reducing the residual shrinkage, resulted Faculty of Materials in no dye variations in the fabric, no tube buckling and no quality changes between Acknowledgments and Environmental Sciences the inner and outer sections of the bobb- The authors wish to thank the authorities of in [5]. The measurements performed, as CAN Textile for the opportunities they have The Faculty was founded in 1969 as given in Table 3, show that no consider- provided and Dr.Mehmet Kanık for very the Faculty of Textile Engineering of the able differences in colour among the useful discussions. Technical University of Łódź, Branch in inner, middle and outer sections of the Bielsko-Biała. It offers several courses bobbins existed. References for a Bachelor of Science degree and a Master of Science degree in the field of The spectrophotometer gave a PASS 1. Ozdemir O.,Şardağ S., Yarn Conditioning Textile Engineering and Environmental value in each of the measurements, in- and New Methods, Textile&Technique, Engineering and Protection. The dicating that the bobbins did not have an Turkey, June 2004, pp. 248-260. unacceptable difference in color among 2. www.welker.de/html/englisch/ Faculty considers modern trends in the inner, middle and outer sections. The heatsetting.html., 2004. science and technology as well as the color difference value which came out 3. Toggweiler P., Gleich S., Wanger F., current needs of regional and national Improved Quality With The Contexxor after the dyeing of the yarns subjected to industries. At present, the Faculty con- Conditioned Yarn, Meiland English No. 9 heat-setting at 90 °C was lower than the (1995) pp. 154-155. sists of: values which came out when the yarns 4. Xorella catalogue, 2003. were subjected to heat-setting at 110 °C, 5. Xorella Contexxor, The Innovative Con- g The Institute of Textile and those not subjected to heat- setting ditioning and Steming System, 2003 Engineering and and dyed. However, the values of colour catalogue. Materials, divided into the follow- differences which exist among the inner, 6. Yazdi A. A., Skewness and ing Departments: Yarn Twist., Proceedings of 2nd Interna- middle and outer sections of the fixed and g Physics and Structural Research tional Istanbul Textile Congress, pp.1-7. non-fixed bobbins are very close to each g Textiles and Composites [CD-ROM] April, 2004 . other and, therefore, they can be consid- g Physical Chemistry of 7. Artzt P., The Influence of Different Spin- ered insignificant. g Chemistry and Technology of ning Processes on The Structure and Properties of Yarns, Proceedings of 2nd Chemical Fibres n Conclusions International Istanbul Textile Congress, pp.1-8. [CD-ROM] April, 2004. g In this study, tenacity, elongation at 8. Enhos S.A., An Investigation About the The Institute of Engineering and Environmental Protection, divid- break (in per cent), and work of rupture Factors Affecting the Strength Properties ed into the following Departments: of 30 tex and 20 tex yarns were found of Blended Yarns, Master thesis, Univer- g Biology and Environmental to be enhanced due to heat-setting. The sity of Uludag, Bursa 2001., pp.73. Chemistry tenacity and elongation at break values of 9. Adanur S., Wellington Sears Handbook of g Hydrology and Water Engineering the yarns decreased after dyeing; howev- Industrial Textiles, Technomic Publishing Co.Inc. Lancaster.-Basel., 1995, pp. g Ecology and Applied Microbiology er, these values are still high when com- 593-594. g Sustainable Development pared with those of the pre- heat setting. 10. Kara I., An Investigation About the Effects of Rural Areas of the Twist Setting Conditions, Final g Processes and Environmental The increase of temperature from 90 °C to Year Project, University of Uludag, Bursa, Technology 110 °C caused a decrease in the strength 2002. values of the yarns. For this reason, heat- 11. Ahumada O., Cocca M., Gentıle G., setting at 90 °C can be considered to be Martuscelli E., D’orazıo L., Uniaxial sufficient to enhance the strength proper- Tensile Properties of Yarns: Effect of ties of PES/viscose yarns – consisting of Moisture Level on the Shape of Stres- 67% PES and 33% viscose. Strain Curves, Textile Research Journal 174 (11) 2004,1001-1006. 12. Tarakc ıoglu I., Textile and After heat-setting, slight changes were Machines –Production and Finishing observed in the twist values of the yarn. of Polyester Fibres; Aracılar Publishing Yarn twist was fixed via heat- setting, Co.Izmir, 1986, pp. 414-416. thus preventing yarn snarling. As a result 13. Morton W.E., Hearle J.W.S., Physical University of Bielsko-Biała of these, the yarn is likely to show better Properties of Textile Fibres; Heineman, Faculty of Materials performance in the following produc- 1975,pp.290. and Environmental Science tion steps. Besides, colour differences 14. Usenko V., Processing of Man-made ul. Willowa 2, 43-309 Bielsko-Biała among the inner, middle and outer sec- Fibres, 1979 , Moscow, pp. 178-189. tel. +48 33 8279 114, fax. +48 33 8279 100 tions of bobbins were found to be insig- nificant after the measurements. Received 10.05.2006 Reviewed 26.01.2007

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