Study on Pile Fabrics

Part 2: Structures of Pile Fabrics

By Toyonori Nishimatsu* and Teiji Sawaki**, Members, TMSJ

*Mie Prefectural Industrial Research Institute, Tsu, Mie Pref. **Chubu Institute of Technology, Kasugai, Aichi Pref. Basedon Journalof the TextileMachinery Society of Japan, Transactions,Vol. 35, No. 10, T146-T152(1982-10) Abstract Structuresand characteristicsof backinglayers and pile layersof pile fabricswere studied. Results obtained are as follows. (1) Assuming that the structures of the backing layer is 3-pickterry, the basic setting value for groundwarps (EGO) and wefts(Eso) maybe expressedby: EGO= EG(SIG + I )/48.6 Eso = Es (3,iW+2,/P)/121.5 wherethe basic setting value is the enddensity of the pile fabricwoven by ground warps Is, wefts 1s and the pile warps l s. EGis the warp density,Es the weftdensity. G is the yarn count of ground warps,P the yarn countof pile warps,and Wthe yarn count of wefts. (2) The pile inclination(0) may be calculatedby, 6 = cos-1(1/0.33Es+dp/2)/(lh+dp/2) whereEs is the weft density, dp the pile diameter and lh the pile inclinationlength. (3) Frictionaland compressiveproperties of pile fabricswere not influenced by the fabricdensity of the backinglayer.

1. Introduction The structure of pile fabrics is divided into two layers : one is a pile layer and the other a backing layer. The former is constituted of pile yarns, and the latter of weft and warp yarns. As both sides of pile fabrics are covered with the pile layer and the middle forms the backing layer, the characteristics of pile fabrics may be determined by the pile layer. In the previous paper'', the relationship between the sensory values for good feel and physical properties of pile fabrics was studied by means of the factor analysis. It was found there that the sensory values were influenced by compressive, frictional and bending properties. But there are few papers~2'31 on the structure of pile fabrics and the relation between the fabric structure and physical properties. So in this paper we studied the structure of pile fabrics and the relation between the backing layer and frictional and compressive properties.

2. Structure of Pile Fabrics

Among pile fabrics, terry fabrics are woven by a special weaving "terry motion". Figure 1 shows the cross-section of pile formation for 3-pick terry, in which two picks are first Fig. 1 Cross-section of pile formation for 3-pick terry.

Vol. 30 (No. 1) (1984) 13 beaten up to a determined distance from the fabric fell. The termined by the standard values of the fabric density and the third pick is then beaten up against the fell together with the yarn counts will be called the "basic setting value"~4~. two preceding picks. Wefts thereby slip along tensioned Now, as standard values, 1s will be chosen for the yarn ground warps. The pile warp ends now form new piles. count of ground warps, wefts and pile warps, and 1 end/cm for warp density, 3 ends/cm for weft density. Thus, the basic 2.1 Pile Structure setting values for ground warps and wefts are defined as 1.0. Pile warps are divided into single yarns and two-ply yarns. When the basic setting values are given, the warp and the The twist direction of single yarns is different from that of weft densities can be calculated for any desired combination two-ply yarns as shown in Figure 2. As single yarns have Z- of counts. And these setting values are useful in developing twist, their piles are twisted in the right direction. On the new terry fabrics. other, as two-ply yarns have S-twist, their piles are twisted in The basic setting values for ground warps and wefts are the left. calculated as follows: EGO= EG (~l G -I-0/478.6 ...... (1) Eso = Es (3/W +2 fl )/ 121.5 ...... (2) where G : Tex count of ground warps, W: Tex count of wefts, P: Tex count of pile warps, EG: No. of ends per cm of ground warps, Es : No. of picks per cm. Equation (1) is valid only with the ratio of one ground warp and one pile warp. Various setting values of terry fabrics are shown in Figure 3. EGOvalues vary from 2.0 to 4.0, and Eso values from 4.0 to 6.5. Higher basic setting values are assumed for wefts (Eso), because the weft density is responsible for the pile fixing.

Fig. 2 Pile structure

This indicates that piles twist in the opposite direction by the untwisting effect of yarns when the third pick approaches the fabric fell. Also, as the third pick is beaten up at the bot- tom of pile warps, piles incline to the opposite side of the fell. 2.2 Structure of Backing Layers The fabric structure of backing layers is 3-pick terry as Fig. 3 Basic setting values of ground warps (EGO) and wefts (Eso) shown in Fig. 1(a). The pile is held by the yarn to yarn fric- for various pile fabrics. tion caused among pile warps, ground warps, and wefts. Figure 4 shows the upper (4.0) and lower (2.0) values of the basic warp setting for various yarn counts of ground and 3. Theory pile warps in ends/cm. For example, when EGOis 2.0 and the 3.1 Basic Setting Values yarn counts of ground and pile warps are lOs, EG becomes Hitherto, the optimum fabric setting values have been de- 6.3 ends/cm from Fig. 4. termined empirically. Warp and weft densities depend on the On the other hand, Figure 5 shows the upper (6.5) and number of threads per unit length, and on the yarn counts of lower (4.0) values of the basic weft setting for various yarn ground warps, wefts and pile warps. So the setting value de- counts of wefts and pile warps in ends/cm.

/4 Journal of The Textile Machinerv Society of Japan Fig. 6 Side view of pile model.

the third weft yarns. If Rp : Pile ratio, d: Weft yarn diameter (cm), dp : Pile warp diameter (cm), l: Unit per length (= 1 cm), ES : Weft density (ends/cm), m : Numbers of piles per 1 cm warp distance (numbers/ Fig. 4 Maximum and minimum basic setting values for warps. cm), lp: Pile length (cm), w : Distance from the first weft to the third weft (cm), then, the definition of the pile ratio Rp, Rp = (lp+(d+dp)/2) x m/l ...... (3) Now as l is 1 cm, eq. (3) becomes Ip = Rp/m-(d+dp);r/2 ...... (3), From Fig. 6, w is w = 1/m-(3d+2dp) ...... (4) W = w+3d+(5/2)dp = 1/m+l/2dp = 1/0.33 ES+I/2dp ...... (5) As the pile form resembles closely an Elastic Model, we apply Leaf's Elastica Model~5's~, and the pile length lp becomes 1p = 2nF(k, 2r/2) ...... (6) where k = sin (a/2), and a is a measured value. So, the pile inclination length lh becomes lh = 2nk ...... (7) By substituting eqs. (3)' and (6) into eq. (7), we obtain Fig. 5 Maximum and minimum basic setting values fo r wefts. lh = (Rp/m-(d+dp)~r/2) k/F(k, ~r/2) ...... (8) Thus, the length OA becomes lh' = lh ± 1 /2 a (9) 3.2 Pile Inclination Therefore, the pile inclination B is given by The pile inclines to the opposite side of the fell as shown in B = cos-1(W/lh') Fig. 2, (b) and (d). Figure 6 shows the side view of a pile (10) model. It is assumed that point A is on the perpendicular 4. Experimental line to the warp axis, and touches the first weft yarn in Fig. 6. Numbers 1, 2 and 3 in Fig. 6 show the first, the second and Table 1 shows samples used to measure the pile inclina-

Vol. 30 (No. I) (1984) I5 Table 1 Samples

tion, which was measured on the cross-sectional photo- the slider is 5 mm/s. The atmosphere of the laboratory is graphs of pile fabrics by a protractor. 20°C and 65 % RH. The relation between the backing layer and the frictional The compressive property was measured by a compressive and compressive properties was studied by using samples testing machine. The maximum pressure is 10 gf/cm2, the As, As, A10 and A11 shown in Table 2. Figure 7 shows the size of the compressive plate is 40 x 40 mm2, and the com- schema of the frictional measuring apparatus. pressing speed is 5 mm/min. Sample was fixed on the horizontal plate and the frictional From the measured Pressure-Thickness curves, such val- force was measured by the tension pick up when the slider ues were calculated as compressive ratio (Ra), compres- was moved on the sample. sive energy (E~), recovery energy (Er'), compressive resilience The size of the slider is 20 x 40 mm2, the load is 17.0 gf, the (Re), compressive modulus (Dr) and compressive recovery moved distance of the slider is 100 mm, the moving speed of ratio (Kr).

Table 2 Samples 5. Results and Discussion Table 3 shows the comparison between measured values of pile inclination and calculated values by eq. (10).

Table 3 Inclination of pile, (B) e

From Table 3, it is found that both calculated and measured value agree well except sample A7. But the difference for sample A7 is large. This may be because the twist number of its pile warps is large and piles are twisted over and over again by the untwisting torque and are inclined. Table 4 shows the measured frictional coefficients in the warp and weft directions for samples As, As, A10 and A11. Table 5 shows the analysis of variance to test the effect of l • A/Kll l~/1V the warp density between A8 and As, and that of the weft Fig. 7 Schema of frictional measuring apparatus. density between A10 and 'All. As Fo.o5 (1, 16) is 4.494 and

16 Journal of The Textile Mar hinery Society of Japan Table 4 Frictional coefficients of samples. 6. Conclusion Structures and characteristics of the backing layer and the pile layer of pile fabrics, and the relation between the backing layer and frictional and compressive properties were studied in this paper. The results obtained are as follows. (1) Assuming that the structure of the backing layer is 3-pick terry, the basic setting value for ground warps (EGO) and wefts (Eso) may be expressed by Table 5 Fo values between samples Ag and A9, and samples A10 EGO= EG (4+[i)/48.6~ and A11. Eso = Es (3~W +2ii )/121.5 (2) The pile inclination (0) may be calculated by 0 = cos (1/0.33 E3+dp/2)/(lh+dp/2) (3) Frictional and compressive properties were not influenced by the fabric density of the backing layer. This study was reported at the 11th Textile Technology

Table 6 Compressive properties.

F0.01(1, 16) is 8.531, FO values are not significant at the 0.05 Table 7 Fo values between samples A~ and A9, and between Alo level. and A11. So, the backing layer which forms the middle layer of the pile fabric doesn't influence on the frictional force, if the yarn count of pile warps, the pile ratio and numbers of the pile unit per area were identical, because the slider rubs only the surface of the pile layer. Table 6 shows the measured compressive properties. Table 7 shows the analysis of variance to test the effect of the warp density between A 8 and A9, and that of the weft denstity between A10 and A11. As Fo.o5 (1, 6) is 5.99 and Fool (1, 6) is 1 compressive energy, recovery energy, compressive Forum of the Textile Machinery Society of Japan (August resilience, compressive modulus and compressive recovery 12, 1982). ratio are not significant, and compressive ratio is significant at the 0.01 level. References It was found that compressive properties (energy, compressive resilience, compressive modulus and compressive [1] Nishimatsu and Sawaki; J. Text. Mach. Soc., Japan, 35, recovery ratio) were not influenced by the fabric density of T146 (1982). the backing layer, if the yarn count of pile warps, the pile [2] Nishimatsu; Bull. of Mie Pref. Ind. Res. Inst., 3, p. 48 ratio and numbers of piles per unit area were identical. This (1978). is because that only the pile layer is compressed and the [3] Nishimatsu; The 32nd Ann. Meet. Rept. of Text. Mach. backing layer is not compressed. Soc., Japan. So, we should notice the pile layer that forms the surface [4] M. Kienbaum; Int. Text. Bull., p. 9 (1977). layer of pile fabrics when we investigate the frictional and [5] Leaf; J. Text. Inst., 51, T49 (1960). compressive properties of pile fabrics. [6] Fundamental Textile Technology (III); Text. Mach. Soc., Japan.

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