Bulk characteristics of air-jet textured yarn woven fabrics

Transcription

1 Indian Jornal of Fibre & Texti le Research Vol. 25, March 2000, pp Blk characteristics of air-jet textred yarn woen fabrics V K Kothari', A Mkhopadhyay & R C D Kashik Department of Textile Technology, The Technological Institte of Textile & Sciences, Bhiwani , India Receied 5 lalll/ary 1999; reised receied alld accepted 22 March 1999 Fabric thickness and specific olme in relation to the natre of weft threads (air-jet textred yarn or flat yarn), pressre leel dring thickness measrement, pick density and heat setting hae been analyzed. On heat setting, the fabric thickness and specific ol me increase appreciably for the textred yarn fabrics. The changes in fabric thickness with the increase in pick density of textred and flat yarn fabrics are dependent on the pressre leel applied dring thickness measrement. Increase in pick density, in general, leads to decrease in fabric specific olme. Fabric specific o lme deried from the thickness measred at 5 gf/cm 2 pressre shold be sed for assessing air-jet textred yarn blk. Keywords: Air-jet textred yarn, Fabric thickness, Heat-set fabric, Physical blk, Pick density, Specific olme 1 Introdction The physical blk of air-jet textred yams plays a decisie role in determining the blk and thermal and mechanical behaior of fabrics made from these yams. Blk characteristics of woen fabrics hae significant inflence on comfort and fabric handling dring garment manfactring. In late 60s, among the different methods of measrement of yam blk, Wrai proposed a method for measring the blk of the air-jet textred yarns based on woen fabric made with them. alation of fabric blk reqires measrement of fabric thickness nder a certain pressre. Hence, the compressional characteristics of yam and fabric are important in the ealation of blk. Srface fzz in a fabric contribtes sbstantially to its oerall thickness 2-4 and is inflenced by height and density of the srface fibres and their stiffness 4. Yarns of higher blk generally prodce fabrics with higher blk s _ The strctre of fabric also has a major inflence on the compressional characteristics of fabrics 6. In an early work, de long et (1/. 7 assmed fabric as a two-phase strctre-a relatiely incompressible core layer in contact with a mch more compressible srface layer on either side_ In a recent stdy, H and Newton 8 proposed a fie-layer strctre for spn yarn woen fabrics instead of three-layer strctre proposed in the earlier two-phase model. In thi s model, the two primary oter layers on either side of ' Department of Textile Technology, Indi an Institte of Technology, New Delhi , Indi a a fabric contain hairy fibres and the crowns aboe the aerage geometrical thickness; the secondary layers on either side of a fabric represent two compress ible layers, which form the firm strctre of the fabric ; and in the middle is the incompressible core of the fabric_ The strctre of air-jet textred yarn fabric can also be isalized in a simi lar way as a three-phase strctre where compressible loopy strctre on either side of a fabric represents the secondary layer. In the present stdy, parent yam and its corresponding textred yam hae been woen into fabrics with different pick densities. Thickness and blk of the fabrics hae been stdied in grey state and after heat setting in relation to the fabric sett. Sitability of fabric thickness or specific olme as a measre of yam blk has been inestigated. 2 Materials and Methods 2.1 Materials Flly drawn mltifilament polyester yam of 70 denier (7.77 tex)/36 filament was sed as the parent I material. It was parallel end textred on ltex A T/HS air-jet textring machine sing the HemaJet with T 100 core nder the following textring conditions: Oerfeed to jet Air pressre Textring speed Water sed per jet Water pressre Stabilization stretch Stabilization heater temperatre Winding nderfeed 26.7 % 9 kgf/cm2 300 mlmin I Iitre/h 2 kgf/cm2 4.7 % ISO"C 0.7 %

2 38 INDI AN 1. FIBR TXT. RS., MARCH 2000 Plain woen fabric samples were prepared with 14.7 tex polyester-i scose (67:33) warp sing mltifilament polyester parent yarn and the air textred yarn as weft. The air-jet textred weft yarn was of I inear density tex and the total linear density of dobled parent yarn sed as weft was tex (2x7.77 tex). With two types of weft yarn (air-jet textred and parent), for different pick densities (24.4, 27.5, 30.7 and 33.8 picks/cm) were sed on the 100m. The fabrics were heat-set on Primatex Stenter at 180 C and 20 rnimin speed with 3% oerfeed, allowing 5.1 % width-wise shrinkage. Fabric particlars for both grey and heat-set fabrics are gien in Table I. In addition to the thread densities, crimp and fabric weight, the geometrical thickness of grey and heat-set fabrics are also presented. Warp and weft crimp ales in case of both parent and textred yarn fabrics increase with pick density in case of grey fabrics. Howeer, in case of heat-set fabrics, de to the amont of relaxation of stresses nder the oerfeed conditions in one direction, the crimp ales of the heat-set fabrics do not show sch a clear trend. Fabric weight increases with the increase in pick density. The geometrical thickness of fabric is deried from thread densities, crimp % and yarn diameter 9. In the calclation, the measred ales of the diameter of warp and textred weft yarn (withot loops) of mm and mm respectiely were sed while parent weft yarn di ameter was calclated as mm sing Schwarz open packing concept'o. 2.2 Methods Fabric thickness was measred on Instron (Model 4411) tester in compressional mode with compression plate of 49 mm di ameter and compression rate 1.2 mm/min. Thickness ales at different pressre leels from I gf/cm2 to 50 gf/cm2 were obtained. Specific olme of the fabric at different pressre leels was ealated from fabric thickness and mass/nit area sing the following expression: Specific olme of fabric(cm 3 / g) = Fabric thickness (mm) x l 000 Fabric weight (g/m 2) Physical blk (%) was obtained smg the following expression: Physical blk (%) = Sp. olme of ( tred yarn fabric x loo Sp. olme o f parent yarn fabri c Table I-Parent and tex tred ya rn woen grey and heat-set fabric particlars, [Nominal end density, 36 ends/cm; and Nominal pick density, pi ckslin. ( picks/em)] Sample Thread d e n s it, No.lcm Crim(!,% Fabri c Geometrical code Warp Weft Warp Weft weigh t, g/m:t Wickness, mm Grey Fabrics GP 36/ GT 36/ GP36/ GT 36/ GP 36/ GT 36/ GP 36/ GT 36/ Heat-set Fabrics HP 36/ HT 36/ HP 36/ HT 36/ I HP 36/ I. I I I HT 36/ HP 36/ HT 36/ G-Grey, H- Heat set, P-Par'el1t, T-Textred.

3 KOTHARI e/ al.: BULK CHARACTRISTICS OF AIR-JT TXTURD YARN WOVN FABRICS 39 3 Reslts and Discssion 3.1 ffects of Pick Density and Heat-setting on Fabric Thickness Fig.l shows that with the increase in pick density the measred ale of textred yarn fabric thickness increases when the thickness is measred nder low pressre leels. There is a ery little change in the apparent thickness if the pressre dring thickness measrement is relatiely high. The changes in thickness with the increase in pick density depend on relatie and absolte ales of crimp amplitdes of warp and weft threads, diameters of warp and weft yarns, compressibility of threads in the fabric strctre and the srface irreglarities of the fabric. At higher pressre, the change in the thickness ales is only marginal de to yarn and fabric compression. After heat setting, a similar trend is obsered with the increase in pick density except in the case of fabric thickness ealated at 1-2 gf/cm2 (Fig. 2). Frther, at lower pressre (1-2 gf/cm\ grey and heatset textred yarn fabric thickness is in the range of mm which is mch higher than the calcl ated ales of geometrical thickness (Table I). This is de to the fact that at lower pressre leel of 1-2 gf/cm2, srface irreglarity affects the measred ales of fabric thickness. Fig. 3 shows that after 20 gf/cm2 pressre, the thickness of textred yarn fabrics changes ery slightly. At high pressres, althogh the standard deiation of fabric thickness redces, the differences in thickness between fabrics also redce. Fig. 4 shows that the textred yarn fabric thickness increases after heat setting. The thermal shrinkage dring the heat setting leads to increased fabric thickness. It is frther obsered that the difference in thickness ales of grey and heat-set fabrics is mch higher at 5 gf/cm2 compared to that at 20 gf/cm2. It is obsered from Figs 5 and 6 that the parent yarn fabric thickness for both grey and heat-set fabrics at lower pressre ( 1-2 gf/cm2) is in the range of mm. This is mch higher than the calclated ales of geometrical thiclgless 9 ( mm) which signify that srface irreglarity affects the measred ale of thickness considerably. At higher pressre, the fabric thickness redces marginally with the increase in picks/cm. It is frther noted that at and beyond 5 gf/cm2 pressre, the changes in fabric thickness redce with frther increase in pressre. At lower pressre ( l1em 2, o2gl/em 2,. 5gl/m2, o10!l lem2 0 5 x 20 gl I cm2 A 30g1 lem 2, Ic m2, 50g! lem2. ",. '" O L A>...,.-- 0 C 0- ox '", c 0 c 1,, L L 36 Pieks / em Fig. I-ffect of pick density on thickness of textred yarn grey fabric at different pressres 0 7r , ",-.lgf/tm 2, o2gf/em 2,. Sgf/cm2, O10gl/cm /em2, "30g1 lem 2, Icm 2," sogllem '" c.x O.L :<:.,. -"- -D 0.3,., ; 0 2 n 2L 26 2S L 36 Fig.2-ffect of pick density on thickness of textred yarn heatset fabric at different pressres GT 36162,0 HT 36/ GP 36/62, D H P 36/62 '" a. c: 0 3..c: '" a. c:..x..c: 0.2--L----=c':_----,,..L_--_:'_::_--..,,. o pressre,gf/em , - Fig.3-ffect of pressre on fabric thickness Grey - 5 gl /em 2, o Gre y.-20 gl /em 2 Hta! set-sgf/cm 2 J D Heat set-20gfjcm D l)-.e ' Fig.4--ffect of pick density on thickness of textred yarn grey and heat-set fabrics at different pressres

4 40 INDIA 1. FIBR TXT. RS., MARCH l /cm 2 o2gl/cm 2 f 0.5 x 20gl/cm 2 I... JOgI/cm2 f - 5.,1 /cm 2, 0109' Icm 2 \/I \/I C.>< A40g1 /cm 2, V /cm 2.c I- - '" "" D PICKS I CM Fig.5-ffect of pick density on thickness of parent yarn grey fabric at di fferent pressres f C.><.c >-" 0.6 r _-,. 0.5 l l f/cm 2, 0 2g1 /cm 2, -. 20g1 /cm gl /cm2-59' / cml,010gl/cml mll.v5091/cm2 o - 1: =... -o-_---(] Fig.6-ffect of pick density on thi ckness of parent yarn heat-set fab ri c at di fferent pressres gf/cm\ the change in fabric thickness is ery sharp (Fig. 3) which indicates that at lower pressre the fabric thickness is ery ssceptibl e to change with minor change in pressre. It appears from the aboe obseration th at for the ealation of yarn blk, the fabric thickness measred at 5 gf/cm2 can be accepted for greater reali sation of yarn blk and deoid of srface irregl arity. 3.2 ffects of Pick Density and Heat-setting on Fabric Specific Volme Fig. 7 shows that with tne increase in pick density of textred yarn fabric, the specific olme of both grey and heat-set fabrics redces slightly whereas on heat setting, the specific olme of th e fabric increases. Again, it is obsered that the change de to heat setting is mch hi gher at lower pressre leel, indicating that the compressible part of fabric thickness increases after heat setting. It is obsered from Fig. 8 th at with the increase in pick density the specific olme of parent yarn fabric decreases. Howeer, the change in fab ric specific Grey - 5 gl /cm 2, -... o Grtr-20 ql /cm 2 ("'"lf Hfot set-591 /cm 2, o Htot stt-20 9' / an o > '. L- -7I Picks Icm Fig.7-ffect of pick density on speci fi c o l me of textred yarn grey and heat-set fabrics at different pressres '" (T;--- Grey - 5g1 /cm 2, o Grey - 209'/cm2 f 41- _ Heot set-5g1 /cm 2, D Heat set - 20g1 /cm 2 " 3to > 2t-, lnl l Pic ks / cm Fig. 8-ffect of pick density on specific olme of parent yarn grey and heat-set fabri cs at different pressres o lme de to heat setting has been ery small in case of parent yarn fabric both at 5gf/cm2 and 20 gf/cm2. Decrease in both grey and heat-set fabric thickness with the increase in pressre from 5 gf/cm2 to 20 gf/cm 2 is relatiely small as compared to that for textred yarn fabric. 3.3 ffects of Pick Density and Heat- setting on Physical Blk, It is obsered from Table 2 that except at ery low pressre ( 1-2 gf/cm 2 ) the fabric physical blk (%) generally redces with the increase in pressre both in case of grey and heat-set fabrics. This is de to the hi gher compressibility of textred yarn fabrics than parent yarn fabrics. On heat setting, the compressional part of textred yarn fabric increases and therefore the phys ical blk of the fabric increases. It is obsered that physical blk does not follow a trend similar to that for specific ol me of fabric with changes in pick density (Table 2, Figs 7 and 8). Therefore, higher ale of fabric specific olme may not always correspond to higher physical blk. It may

5 KOTHARI et al.: BULK CHARACTRISTICS OF AIR-JT TXTURD YARN WOVN FABRICS 41 Table 2-Physical blk of grey and heat-set fabrics measred nder different pressre leels Sample code I" 2" 5" GT36/ l GT36/ GT36/ GT36/ HT36/ HT36/ HT36/ HT36/ Physical blk, % 10" 20" 30" 40" SO" l l.7 "Pressre leel (gucm 2 ) be mentioned here that the difference in blk for parent and textred yarn fabrics is not sfficiently large as it is in the yarn stage. A nmber of factors sch as the characteristics of warp materi al, difference in yarn crimp amplitde, compression of yarn at cross oer region and fabric srface irreglarity hae significant impact oer fabric blk. It is worth noting that the physical blk ales are ery low as obtained from the woen fabric method as the a le is affected by many factors. Therefore, the ealation of physical blk throgh woen fabric method is not recommended. Howeer, the fabri c specific olme ealated at 5 gf/cm 2 can be sed for assessing air-jet textred yarn blk. 4 Conclsions The natre of change in thickness and specific olme of air-jet textred and parent yarn fabrics with the change in pick density is dependent on the pressre leel. At hi gher pressre, the thickness and specific olme of grey and heat-set fabrics decrease marginally with the increase in pick density whereas at low pressre, the aboe fabric parameters are inflenced by the fabric co n trctional parameters and srface irreglarity. On heat-setting, the textred yarn fabric thickness and specific olme increase. For the ealation air-jet textred yarn blk, the physical blk deried throgh woen fabric method is not ery sefl. Howeer, fabric specific olme at 5 gf/cm 2 can be sed for assessing the air-jet textred yarn blk. References I WrayGR, JTextil1Sl,60(1969) Rees W A, J Text lnst, 32 (194 1) T Schiefer H F, Steens H T, Mach P B & Boyland P M, J Res Natl Br Stan d, 32 (1944) Bogaty H, Holl ies N R S, Hintermaier J C & Harris M, Text ResJ, 23 (1953) Goswami B C, Martindale J G & Scardino F L, Textile yarns (John Wiley & Sons, New York), 1977, Dpis D, Popo G & Vialli er P, Text Res.l, 65 ( 1995) de Jong S, Snaith J W & Mi chi e N A, Text Res J, 56 (1986) H J & Newton A, J Textlnst, 88 (1997) Peirce F T, J Text lllst, 28( 1937) T Schwarz R, Text Res.1,2 1 ( 195 I) 125.