CREASING BEHAVIOR OF SOME WOVEN MATERIALS MADE FROM COMBED YARNS TYPE WOOL AN EXPERIMENTAL INVESTIGATION

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1 10 INTERNATIONAL SCIENTIFIC CONFERENCE 19 0 Novemer 010, GABROVO CREASING BEHAVIOR OF SOME WOVEN MATERIALS MADE FROM COMBED YARNS TYPE WOOL AN EXPERIMENTAL INVESTIGATION Liliana Hristian, Ph.D* Iliana Gariela Lp, Ph.D* Oana Cramaric, Ph.D** *Technical University Gh. Asachi, Jassy, Romania ** Tampere University of Technology, Finland hristian@tex.tiasi.ro Astract The paper analyses the ehavior to creasing of some woven materials made from yarns type wool sed for readymade clothes. Factors like firos composition, properties of constitent fiers, wovens strctre parameters, mechanical properties of and yarns and finishing treatments that inflenced the recovery capacity from crease/folding were investigated experimentally throgh several tests which revealed their importance in the process. Keywords: mechanical properties of and yarns, flotation, creasing, the recovery angle after folding. 1. INTRODUCTION The creasing of woven materials made from comed yarns type wool sed for readyclothes is an ndesired deformation effect with temporary or permanent character, which is cased y a composed strain of ending and compression dring tilization, processing or maintenance. It is manifested y the appearance of wrinkles, folds or stripes on the srface of wovens materials, ths diminishing their qalitative appearance and also their practical vale. Therefore, the woven materials sed for garments manfactring are classified in the following categories: - redced creasing, articles type wool; - average creasing, articles made of synthetic yarns; - prononced creasing, articles made of celllosic yarns that can e improved throgh sperior finishing. Creasing is the reslt of irreversile changes created throgh the reciprocal sliding of strctral fier components when exposed to a ending strain. Creasing is specific to oriented strctres with high crystallinity (celllosic fiers). The sliding appears ecase of hydrogen ond reaking which can, however, reform easy in other positions conferring a permanent character to creasing.. EXPERIMENTAL PART The experimental trials have een performed on a series of woven materials made of 100% wool. Factors like firos composition, properties of constitent fiers, strctral woven parameters, mechanical properties of and yarns and finishing treatments that inflenced the recovery capacity from creasing/folding were investigated sch as to assess their importance. In order to reveal the inflence of onding on the srface characteristics of wovens we have expressed it throgh the mean flotation F for yarns and mean flotation F for yarns. The intersection etween a yarn and yarn is called onding point, ths the onding contains all onding points having a or effect along a longitdinal or transversal direction. One or more onding points having the same effect and forming one onding segment can exist in longitdinal or transversal direction. The onding segments with the same effect are called flotation (F). They can e flotation (F ) when the yarn passes over the II-348

2 yarn and flotation (F ) when the yarns passes over the yarn. The flotation size, similar to the onding segment, have the minimm vale F=1. The following relations exist etween the ration (R), nmer of passes (t) and mean flotation (F): R F = ; t R F = (1) t The measrements are done on woven samples having standard dimensions. These are folded at 180 o and pressed along the direction of one of the constitent fier systems y applying over a defined time interval folding forces which are dependent on the nit srface mass. After the removal of the folding forces, the sample is left to relax freely. The recovery angle is measred in the end of a determined time interval. The following indicators are for estimating the capacity of textile materials to maintain their initial shape and dimensions dring the wearing time: the recovery angle after folding ( )- the angle etween the sample sides folded according to the SR EN ISO. after the removal of the folding force; recovery coefficient (%) calclated according to relation (): 1 = 100 () o 180 where the recovery coefficient can e determined: -at t 1 =1 minte after detension when either 1 (%) or the instantaneos recovery coefficient is determined; -at t =10 mintes after detension when either (%) or the slow recovery coefficient is determined. The latter is defined y relation (3): 1 = 100 (3) o 180 The total coefficient of recovery after folding is calclated according to relation (4): = 1 + (4) The recovery capacity from creasing depends on the firos composition and on the level of deformations. Additionally, also technological processing throgh mechanical, physical or chemical processes can inflence positively or negatively the evoltion of the indicator. Several operations have een performed for each item from the woven materials considered in the stdy: - evalation of the recovery angle after folding ( ) and of the recovery coefficient (%) along the direction of the two yarn systems, i.e. and. The experimental vales are given in Tale 1: - Fig.1 and Fig. are illstrating the plots of fnctions (t) and (t) y considering the woven materials groped ased on their flotation size. Following sefl oservations for the design of woven materials can e drawn ased on the analysis of the vales in Tale 1 and on their graphical representation: - the largest vale of the recovery angle was recorded for the wovens having the average flotation F= trialed along the direction. These were followed y wovens with same flotation vale t along the direction; - y redcing the flotation the recovery angle decreases while the recovery coefficient increases; - while the yarns diameter increases the recovery angle decreases; - the amplitde of the recovery angle variation is 8.77% along the yarn direction and 5.% along the yarn direction. For instance: a) item A1 in Tale 1 has =173 o and =170,8 o with Nm Nm, P >P, having onding D /, ths average flotation F=; ) item A14 has =155,4 o and =157,8 o, Nm Nm, P >P, having plaine onding, ths the average flotation F=1. 3. CONCLUSIONS The creasing of wovens is a complex process of deformation nder the action of mechanical stretching, ending and compression strains. II-349

3 1. Regarding the inflence of firos composition and the constitent fier characteristics on the recovery capacity from creasing 1.1. The ehavior to creasing is determined y the deformaility of the constitent fiers with respect to the creasing conditions. Tael 1. Evalation indicators for assessing the creasing ehavior of the stdied wovens Code Art. Bonding Yarn cont Nm Flotation Recovery angle from creasing, Recovery coefficient from creasing Warp Weft Warp Weft Warp Weft Warp Weft A1 D/ 40/ 4/ A D/1 40/ 4/ A3 D/ 5/ 5/ A4 Plain 5/ 5/ A5 P /1 5/ 5/ A6 Plain 5/ 5/ A7 D/ 48/ 48/ A8 D/1 48/ 30/ A9 crepe 48/ 30/ A10 crepe 48/ 48/ A11 D/ 48/ 30/ A1 check 48/ 48/ A13 P / 48/ 48/ A14 Plain 45/ 6/ A15 crepe 45/ 45/ A16 D/1 64/ 64/ A17 D/1 60/ 60/ A18 D 3/1 3/1 1/ 1/1 60/ 60/ A19 D/1 56/ 37/ A0 D/ 56/ 37/ A1 D/1 56/ 37/ A D1/ 56/ 37/ A3 Plain 56/ 37/ A4 Plain 56/ 56/ The response at a certain strain level (strain speed, time, alternation of application direction, compression or stretching level) is evalated depending whether the creasing is nder or over the elasticity limit of the mentioned strain The strain level throgh creasing determines the total deformation which in trn is determining the ratio etween the elastic components of recovery and the remanent deformation vale Based on the data presented aove one can oserve that nder the standard conditions the recovery angle is higher along the yarns direction, which cold e ecase of the following reasons: - yarns fatige dring the weaving process; - density difference of the two yarn systems; - different respons of the two yarn systems - dring the finishing process.. Regarding the inflence of strctral parameters on the recovery capacity from creasing.1. The yarns fineness, technological density and the type of onding is signficantly inflencing the creasing/folding ehavior. II-350

4 .. The yarns fineness is inflencing, at constant strctre parameters, the woven thickness. Ths, increasing the thickness y increasing the linear density of the sed yarns leads to a higher resistance to creasing..3. The yarns density is inflencing the creasing ehavior ecase the decrease of this parameter leads, independent of the sed onding type, to lower creasing tendency..4. The length of flotations has a positive inflence on the recovery capacity from creasing..5. The simltaneos decrease of yarns density and flotations length parameters leads to a lower fier tension state of the two yarns systems. This is reflected in the vales of the recovery angle. For instance: for yarns with same composition and strctre: Nm =Nm =5/, Item A4 in Tale 1, with P =15 yarns/10cm, P=195 yarns/10cm, =156,8 o, =156, o and =1,9 %, =13, %, plaine onding; Item A3 in Tale 1, with P =65 yarns/10cm, P =10 yarns/10cm, =171 o =169 o and =7,8 %, =7,1 %, diagonal onding D /..6. The plaine onding presents a low recovery capacity from creasing, ths the flotation increase for oth of yarns and yarns is favorale for redcing the creasing. The effect is compensated ecase the density in the two yarn systems is different. Fig.. Variation of recovery angle after folding from creasing for the stdied wovens 3. Regarding the inflence of the mechanical properties of and yarns on the recovery capacity from creasing 3.1. Warp yarns are more strained and worn dring processing than yarns. Ths, even if the two yarns have identical strctres, the elasticity modle of yarns is higher, i.e. they ecome more rigid. This is reflected in lower vales of the recovery angle for samples orientated along the direction. 3.. Creasing is inflenced y increased stiffness dring stretching, which is expressed throgh the elasticity modle The higher the elasticity modle vale, the lower is the recovery angle and the higher the creasing recovery coefficient. The II-351

5 interdependence etween elasticity modle and creasing recovery capacity is illstrated y the experimental data recorded, for instance: Item A1, with Nm Nm, P >P, =164,6 o, =167,6 o and =8,6%, =6,9%, having the diagonal onding D /, elasticity 1 E =44,35 N/tex, E =6,91 N/tex; Item A11, with Nm Nm, P >P, =165, o, =167, o şi =8, %, =7,1%, having diagonal onding D /, elasticity modle E =4,55 N/tex, E =4,31 N/tex The present stdy is also revealing the differentiation,in the frame of the same item, according to technological axis, the recovery angle from creasing along direction is higher than the recovery angle along direction. When the fineness Nm = Nm, the recovery angle is higher along direction and depends on the ration etween technological densities and onding type. REFERENCE [1] M. Neclăiasa, Stdy of textiles, Vol. 3, Ed. VIE, Iaşi, 000; [] Hristian Liliana, Sstantion and elaoration of a new testing methodology of woven materials srface characteristics with classical testing methods Doctoral Thesis, Gh. Asachi Technical University, Iasi, 008; II-35