BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI Publicat de Universitatea Tehnică Gheorghe Asachi din Iaşi Tomul LVI (LX), Fasc. 3, 2010 SecŃia TEXTILE. PIELĂRIE THE THICKNESS MEASUREMENT OF WEFT KNITTED STRUCTURES MADE WITH ELASTOMERIC YARNS BY ALENKA PAVKO CUDEN* and YORDANKA P. ANGELOVA** Abstract. The objective of the research was to measure the thickness of knitted fabric: four different weft knitted structures from four different yarns (PAN, Viscose, PAN/EL and Viscose/EL). The fabrics were knitted in two tightness (compactness) levels and dry or wet and dry relaxed. The results of the measurements show that the fabrics from PAN and viscose respectively exhibit quite different geometry. Generally, viscose fabrics exhibit bigger thickness changes. Fabric thickness increases in most cases with wet relaxation. It decreases most often in the case of double structures (1x1 rib, 1x1 purl). Key words: thickness, knitted, fabric, core-spun yarns. 1. Introduction The elastic garments provide more comfort, freedom of movements and shape retention. Elastane of 2% is enough to improve their fit. Knitting with core-spun elastomeric yarns usually results in a compact to very compact structure because of the yarn extension in the knitting zone, fabric relaxation after taking-off and yarn compression, which leads to changes in the loop geometry including fabric thickness in relation to yarn thickness [4], [6]. 2. Experimental Part The objective of the research was to measure the thickness of knitted fabric containing elastane [1], [4] and [5]. For this purpose, five different weft knitted structures (three single and two double: single miss - M, single half cardigan - PF, single cardigan - F, 1x1 rib - RR and 1x1 purl - LL) from four different yarns (two conventional yarns from viscose and PAN respectively, and two core-spun yarns from PAN/EL and viscose/el respectively). The fabrics were knitted in two tightness (compactness) levels and dry or dray and wet relaxed.
24 Alenka Pavko Cuden and Yordanka Angelova The thickness of the samples was determined by a fabric thickness tester Mitutoyo [6]. Loads 8.63 cn, 20 cn, 40 cn, 60 cn, 80 cn and 100 cn were applied. Fabric thickness was measured after dry relaxation and furthermore after wet relaxation. Fig. 1 Linear model. Fig. 2 Nonlinear model. Pressure-thickness linear and non-linear trend lines were drawn in Excel extrapolating the results to the zero loading for all structures (Figs.1 and 2 showing 1x1 RR PAN structure). The trendlines equations were defined and fabric thickness values read at zero loading (Tables: 1,...,4).
Bul. Inst. Polit. Iaşi, t. LVI (LX), f. 3, 2010 25 Table 1 Yarn: PAN Table 2 Yarn PAN/EL
26 Alenka Pavko Cuden and Yordanka Angelova Table 3 Yarn CV Table 4 Yarn CV/EL
Bul. Inst. Polit. Iaşi, t. LVI (LX), f. 3, 2010 27 According to correlation coefficients and reference [3], non-linear pressure-thickness relation was assumed and yarn thickness values read from the curves at zero loading. The results of the fabric thickness measurements are presented in Figs. 3 and 4. Fig. 3 Thickness of open knitted structures from different yarns and relaxations. Fig. 4 Thickness of close knitted structures from different yarns and relaxations. The R coefficient of correlation and the R2 coefficient of determination value are indicators of how well the model fits the data. The values of R2 are more close to 1.0 and indicate that we have accounted for almost all of the variability
28 Alenka Pavko Cuden and Yordanka Angelova with the variables specified in the model. The non-linear model is more proper than the linear model for defining the thickness of the fabric under zero loading. 3. Conclusions The results of the measurements show that the fabrics from PAN and viscose respectively exhibit quite different geometry. Generally, viscose fabrics exhibit bigger thickness changes. Fabric thickness increases in most cases with wet relaxation. It decreases most often in the case of double structures (1x1 rib, 1x1purl). R E F E R E N C E S 1. Knapton J.J.F., Ahrens F.J., Ingenthon W.W., Fong W., The Dimensional Properties of Knitted Wool Fabrics. Part I, The Plain Knitted Structure. TRJ, 38, 999 (1968). 2. Matsudaira M., Qin H., Features and Mechanical Parameters of Fabric's Compressional Property. JTI, 83, 476 (1995). 3. Alimaa D. et al., Pressure-Thickness Relation and Compression Mechanism of Plain and Rib Knitted Fabrics. Journal of Textile Machinery and Society Japan, English Edition (2000). 4. Nakajima M., Effect of Relaxation Processes on the Thickness of Plain Knitted Fabrics. Bulletin of the Faculty of Textile Science, Kyoto Institute of Technology, Japan, 25, 7 (2001). 5. Kopitar D., Vrljicak Z., Skenderi Z., Influence of Yarn Count on Knitted Fabrics Thickness and Mass Per Unit Area. Annals of Daaam & Proceedings (2007). 6. Pavko-Cuden A., Ph. D. Diss., University of Ljubljana, Ljubljana (2005). Received: September 29, 2009 *University of Ljubljana, Department of Textiles, Slovenia e-mail: alenka.cuden@ntf.uni-lj.si ** TU Gabrovo, Bulgaria GROSIMEA TRICOTURILOR DIN BĂTĂTURĂ CU FIRE ELASTOMERE (Rezumat) Obiectivul principal al cercetărilor l-a constituit măsurarea grosimii tricoturilor din bătătură cu fire elastomere. Pentru aceasta, s-au realizat patru structuri diferite (două pe maşini cu o fontură şi două pe maşini cu două fonturi) din patru tipuri de fire (unul din viscoză, unul din PAN iar celelalte două fiind fire cu miez în variantele: PAN/elastan şi viscoză/elastan). Tricoturile au fost realizate în două variante de desimi (compactitate) şi au fost supuse relaxării în două variante: relaxare uscată şi relaxare umedă. Rezultatele determinărilor au arătat că tricoturile din PAN şi viscoză 100% prezintă geometrii diferite. În general cele din viscoză manifestă variańii mai mari ale grosimii. Grosimea creşte în cele mai multe situańii în cazul relaxării umede. Ea descreşte în cazul structurilor tricotate pe maşini cu două fonturi (patent 1x1 şi lincs 1x1).