Comparison of the Characteristics of Open-end and Ring Yarns and Fabrics of Different Structures

Transcription

1 Indian Journal of Textile Research Vol. 9. December pp Comparison of the Characteristics of Open-end and Ring Yarns and Fabrics of Different Structures G S BHARGAVA, P K MEHTA & R K GULATI The Technological Institute of Textiles. Bhiwani Receired II December 1983: accepted 2J February 1984 As the plying of yarn improves not only the yarn quality but also the fabric quality, a study has been made to compare the extent of improvement resulting from plying in open-end yarn. ring yarn and in fabrics prepared with these yarns as weft. by keeping the warp and weave identical. Increase in twist and number of plies in open-end yarn produced a plied yarn comparable to nng yarn. However. the use or open-end yarn demands a judicious selection or yarn COUIlt.number or plies In the final yarn, twist levels of single- and plied-stage yarn. loom set! and the type of weave for producing fabrics with optimum performance. Open-end (OE) yarn differs in structure from ring yarn 1.2, and by virtue of this the fabrics prepared from the two vary in their characteristics:' -7. Salhotra et al. 2 found that 2-ply OE yarns are comparable to 2-ply ring yarns in strength after being processed with a slightly higher twist. Keeping this in view, we made the present study with single-, 2-ply and 3-ply OE and ring yarns using three plying twist levels to determine the changes in breaking strength, elongation and tenacity of the yarn. A quality yarn would produce a quality fabric, but the level of fabric assistance may further vary in the level of improvement of the fabric quality. Therefore, some of the important fabric characteristics, viz. change in fabric construction, breaking strength, breaking elongation, tear strength, flex abrasion and fabric flexural rigidity, have been examined after using different yarns as weft, keeping the quality of warp and weave identical. Materials and Methods Cotton-J-34 Saw gin cotton was used for making the yarn and fabric samples. The main characteristics of the cotton used were mean fibre length, 20 mm; fibre strength (Pressley index), 8.2 lb/mg; and fibre fineness (micronaire value), 4.7 Jig/in. Preparation of yarn samples-cotton yarns of 20s nominal count were spun by using BD 40 OE and ring frame machines. Open-end yarn was prepared with an equivalent of 20 turns per inch of the ring yarn. Using open-end and ring yarns, 2-ply and 3-ply yarns, the first with 12, 16 and 20 turns/in. and the Present address: Government Central Textile Institute. Kanpur. second with 10, 14 and 18 turns/in., were prepared. Thus, in all, 12 yarn samples, six from open-end and six from ring yarn, were prepared. Each yarn sample was allotted a reference number (Table 1). In the yarn reference number the first two letters represent ply (Si, single: Tw, 2-ply: and Th. 3-plyJ. the third letter the system of yarn preparation i.e. O--open-end and R- ring. and the digit, the plying twist. Preparation of fabric samples-two weaver's beams, one with single 20s ring yarn and the other with 2-ply ring yarn having 16 turns/in. plying twist, were prepared. Two fabrics of 56 x 48 nominal construction were prepared by using the same single warp and single open-end and ring yarns as weft. Six fabric samples of 36 x 36 nominal construction were prepared by using 2-ply ring warp and six different 2-ply weft yarns. Another six fabric samples of 36 x 30 nominal construction were prepared by using 2-ply ring warp and six different 3-ply weft yarns. The fabric samples were desized and scoured under actual mill conditions. Before. testing, all the yarn and fabric samples were conditioned in standard atmosphere (65 ± 5/.) RH and 27 ± 2 C) for 24 hr and 48 hr respectively. The breaking strength and breaking elongation of single yarns were measured on an Instron tensile strength tester and the tenacity was calculated by dividing the breaking strength (gram) by yarn rex. The diameter of the yarn samples was determined with a projection microscope. The number of threads/in. in the warp and weft directions of each fabric sample was determined in the usual way by counting the number of threads in 1 in. with a standard I in. pick glass. The warp and weft crimps of the fabrics were measured on a Eureka crimp 154

2 BHARGAYA 1'/ (I/. CHARACTERISTICS or OPEN-END & RING YARl'<S AND FABRICS tester (Shirley type) and the percentage of total crimp was calculated as follows: Total crimp, /,,=(C1)1 2+(C2)1 2 where C1 and C 2 are percentage warp-and weft crimps respectively. The fabric weight was determined with a quadrant balance. The breaking strength and breaking elongation in warp and weft directions of each fabric sample were determined with an Instron tensile strength tester and using the standard method for ravelled strip, with 20 em gauge length and 5 cm wide specimen. The traverse speed was 300 mm/rnin. Each fabric sample was tested for flex abrasion on an ASTM flex abrasion tester in both warp and weft directions. The end point was determined when the strip was worn off and was specified by the number of cycles. The bending length in warp and weft directions of each fabric sample was determined with the Shirley stiffness tester. The flexural rigidity in warp and weft directions of each fabric sample was calculated by using the following relation: Flexural rigidity (mg-cm)= We (warp or weft) where W is the weight (mg/cm") of the fabric; and L, the bending length in em. To observe the general effect of the variable parameter on the fabric characteristics, the overall value of each characteristic was determined for each fabric sample by taking the geometric mean of warp and weft values. Results and Discussion Yarn Characteristics The yarn count, breaking strength, breaking elongation, tenacity and diameter of the experimental yarns are given in Table I. A comparison of the values of these characteristics for SiO 19 and SiR 19 yarns reveals that SiO 19 yarn is weaker, more extensible, less tenacious and more bulky than SiRI9 yarn by 28.5, and 3.4% respectively. This is attributed to the structural difference between open-end and ring yarns. This is in agreement with the findings of Lord I and Salhotra 1'1 al. 2. Similar trends are observed with 2-ply and 3-ply yarns for different yarn characteristics. A comparison of the breaking strengths of 2-ply yarns having the same level of plying twist shows that 2-ply open-end yarns are weaker than the corresponding ring yarns by 32.9,33.0 and 23.2"" at 12, 16 and 20 plying twist levels respectively. This shows that initial plying twist insertion does not reduce the difference between the Table I-Characteristics of Yarns Yarn Yarn Breaking Breaking Yarn Yarn ref. count strength elongation tenacity diameter No. Ne g 0, 0 g/tex mm x 10-2 SiOl SiRI TwOl TwRI TwOl TwRI Tw TwR ThOIO ThRIO ThOl ThRI ThOl ThR IX strengths of the two yarns, but higher plying twist level results in a significant reduction in the difference in yarn breaking strengths. A similar trend is observed for tenacity, which shows that 2-ply open-end yarns have a lower tenacity than the corresponding ring yarns by and 22.2% at and 20 plying twist levels respectively. A comparison of the values of breaking strength for 3-ply yarns shows that open-end yarns are weaker than the corresponding ring yarns by and 24.9 " at 10, 14 and 18 plying twist levels respectively. This shows that there is a significant reduction in the difference between the strengths of two types of yarn on increasing the number of plies. Since plying is uneconomical, open-end yarn may substitute ring yarn in the structures where 2-ply and 3-ply yarns are used to meet the specific requirements. e.g. canvas. ducks, industrial fabrics. etc. The reason for open-end yarn being weaker than equivalent ring yarn is the lack of proper orientation of fibres when they are deposited in the rotor freely and wraper fibres which do not contribute to yarn strength:'. The same effect is observed in plied yarn. though plying reduces the difference in strength and tenacity at higher levels of plying twist. A similar trend is observed for the tenacity of 3-ply yarns, which shows that open-end yarns have a lower tenacity than ring yarns by and 21.2~" at 10, 14 and 18 plying twist levels respectively. It is also obs-rved that a gradual increase in plying twist reduces the difference between the tenacity values of the two yarns gradually. The breaking elongation values of plied yarns show that open-end yarns are more extensible than the corresponding ring yarns. 2-Ply open-end yarns are more extensible by II and 1.4~" at and 20 plying twist levels respectively. while 3-ply open-end l~~

3 INDIAN J. TEXT. RES.. VOL. 9. DECEMBER 1984 yarns are more extensible by 4.4 and O.9~Jat )0 and) 4 plying twist levels respectively. It is interesting that at 18 turns/in. plying twist, the extensibility of 3-ply yarns was almost the same. The results show that at a higher level of plying twist, the extensibility of plied yarns is comparable. These findings are in agreement with those of Salhotra et a/. 2. The values of yarn diameter show that single openend yarn is 3.4~;;)bulkier than single ring yarn; 2-ply open-end yarns are 11.9, 14.3 and 3.2% bulkier at 12, 16 and 20 plying twist levels respectively; while 3-ply open-end yarns are 4.3, 6.6 and 7.2,/~bulkier at l O, 14 and 18 plying twist levels respectively. This shows that in 2-ply yarns, increase in twist initially increases the difference and later decreases it, whereas in 3-ply yarns, a gradual increase in twist reduces the difference between the bulkiness of the two types of yarn. This may be because of the changed behaviour of twist on the surface of multi-plied yarns. Fabric Characteristics Threads per in., crimp and fabric weight have a direct influence on most of the fabric characteristics, which change in a different manner when the yarn and fabric structures are changed as a result of wet treatment. Therefore, the fabric sett, crimp and fabric weight of desized and scoured fabrics were determined to study the influence of such changes on fabric characteristics, like breaking strength, breaking elongation, tearing strength, flex abrasion resistance, bending length, flexural rigidity,. and stiffness. The values of various fabric characteristics' are given In Tables 2-4. Threads/in.-From the values of threads per in. in both warp and weft directions (Table 2), it is observed that the scouring and desizing treatment brings about more shrinkage in the cross-direction than in the longitudinal direction, ends/in. increasing by 5-6 and picks/in. by 2-5. The reason for this trend is that the wet treatment swells the fibres, causing increase in yarn diameter and demanding additional yarn length, which is not available. Since the cloth is not constrained at the ends, the threads come closer, resulting in a higher number of threads/in. Further, increase in threads/in. is dependent on yarn structure and fabric construction and is little affected by the type of yarn. Crimp-A comparison of the values of warp and weft crimps for open-end and ring yarn fabrics of the same weft yarn twist and construction (Table 2) shows no particular trend but the values of total crimps are higher (though marginally) for open-end fabrics than for ring fabrics. Fabricweight-The fabric weights of open-end and ring yarn fabrics having the same weft yarn twist and construction (Table 2) show that ring yarn fabrics are heavier than the corresponding OE yarn fabrics and the trend is independent of the weft yarn folding twist and fabric construction. Pulay ' and Mohamed and Lord 4 also observed similar trends for threads/in., crimp and fabric weight. Table 2-Characteristics of Experimental Fabrics Fabric Threads/in. Crimp. % Fabric Weight ref. No * g/m" Warp Weft Warp Weft Total Nominal construction, Reed x Pick: 56 x 48 SiOl9 6: SiRI Nominal construction. Reed x Pick: 36 x 36 TwOl TwRI TwOl TwRI Tw TwR Nominal construction. Reed x Pick: 36 x 30 ThOIO ThRIO ThOl ThRI ThOl ThRI *Fabric reference number is the same as the yarn reference number and depends on the type of yarn used as weft in the preparation of fabric sample.

4 BHARGAVA 1'/ al.. CHARACTERISTICS OF OPEN-END & RING YARNS AND FABRICS Table 3-Breaking Strength, Breaking Elongation and Tearing Strength Values of Experimental Fabrics Fabric Breaking strength, kg Breaking elongation, % Tearing strength, kg ref. No. Warp Weft Overall Warp Weft Overall Warp Weft Overall Nominal construction, Reed x Pick: 56 x 48 SiOl SiR Nominal construction, Reed x Pick: 36 x 36 Tw TwR TwOl O.S TwRI Tw TwR Nominal construction, Reed x Piclc 36 x 30 ThOIO ThRIO ThOl ThR il ThOl ThRI Table 4-Flex Abrasion, Bending Length and Flexural Rigidity Values of Experimental Fabrics Fabric Flex abrasion, cycles Bending length, em Flexural rigidity, mg em ref. No. Warp Weft Overall Warp Weft Warp Weft Overall Nominal construction, Reed x Pick: 56 x 48 SiOl SiR Nominal construction, Reed x Pick: 36 x 36 TwO TwRI Tw TwRI Tw TwR Nominal construction, Reed x Pick: 36 x 30 ThOIO ThRIO ThOl , ThRI ThOl ThRI Breaking strength-the values of warp and weft breaking strengths for various fabrics having OE/ring yarn as a weft show that ring fabrics are stronger than OE fabrics, irrespective of the weft yarn structure and fabric construction (Table 3). The overall breaking strengths of ring fabrics are, in general, higher than those of the corresponding OE fabrics. This is in agreement with the findings of several researchers? -7. The reason for such a trend may be that ring yarns are stronger than OE yarns. From the results, it is also found that increase in plying twist increases the warp, weft and overall breaking strengths. Further, increase in the number of plies increases the warp, weft and overall breaking strengths, as expected. This may be due to increased strength as a result of increase in twist or of the number of plies in the yarn. A comparison of the values of overall breaking strength for OE and ring yarn fabrics having different folding twists, but the same fabric construction, reveals that the breaking strengths of the fabrics having maximum folding twist OE yarn, i.e. Tw020 and ThO 18, are comparable with those of the fabrics having minimum folding twist ring yarn, i.e. TwR 12 and ThRIO. 157

5 INDIAN J. TEXT. RES.. VOl. 9, DECEMBER 1984 Breaking elongation-the breaking elongations for warp and weft directions of various fabrics having OE/ ring spun yarn as a weft show that ring fabrics are less extensible than the corresponding OE weft fabrics, irrespective of the weft yarn structure and fabric construction (Table 3). The overall breaking elongations of ring fabrics are also, in general, lower than those of the corresponding OE fabrics. Similar observations were made by Pillay ' and Rakshit". The reason for such a trend may be that ring yarns are less extensible than OE yarns. With increase in plying twist, the values of warp, weft and overall breaking elongations increased in the case of 2-ply yarns and decreased in the case of 3-ply yarns. Increase in the number of plies increases the breaking elongation. This may be because of increase in crimp and extensibility of yarn with increase in the number of plies in the yarn. It is also observed that increase in the number of plies makes the two fabrics comparable in breaking elongation at higher twist levels. Tearing strength-the tearing strengths for warp and weft directions of various fabrics having OE/ring yarn as a weft show that the ring fabrics have a higher tearing strength than the OE fabrics, irrespective of weft yarn structure and fabric construction (Table 3). The overall tearing strengths of ring fabrics are also generally higher than those of the corresponding OE fabrics. The reason for this is that the ring yarn has a higher tenacity than the OE yarn (Table I). Similar observations were made by Pillay ' and Mohamed and Lord". Increase in twist and the number of plies increased the warp, weft and overall tearing strengths of fabrics, irrespective of the type of yarn and fabric construction. In the case of 2-ply weft yarn fabric, warp tearing strength is higher than weft tearing strength, while in the case of 3-ply weft yarn fabric, weft tearing strength is higher than warp tearing strength. This is because both the fabrics have the same warp but different wefts arid 3-ply weft is stronger than 2-ply weft. The values of overall tearing strength for OE and ring yarn fabrics, having different folding twists but the same fabric construction, reveal that the tear strengths of the fabrics having maximum folding twist OE yarn, i.e. Tw020 and ThOI8, are comparable with those of the fabrics having minimum folding twist ring yarn, i.e. TwRI2 and ThRlO. Flex abrasion-table 4 shows that the values of warp, weft and overall flex abrasion resistance are higher for ring fabrics than for corresponding OE weft fabrics. irrespective of the weft yarn twist and the number of plies. Similar observations were made by Pillay3 and Mohamed and Lord 4 with single yarns and by Rakshit" with 2-ply yarns. Increase in twist decreased the flex abrasion resistance of fabrics, irrespective of the type of yarn. Further, increase in the number of plies in the weft yarn increased the warp, weft and overall flex abrasion resistance. The poor flex abrasion of OE fabrics may be due to the surface character ofoe yarn, which makes it easier to pull the fibres from the fabric surface. Bending length and flexural rigidity-the values of bending length and flexural rigidity for warp and weft directions of various fabrics having OE and ring yarns show that ring weft fabrics exhibit more bending length and flexural rigidity than OE weft fabrics, irrespective of weft yarn structure and fabric construction (Table 4). These observations accord with those of Mohamed and Lord 4 and Palit 7. All the fabrics had higher warp-way bending length and flexural rigidity than weft-way bending length and flexural rigidity. The reason for this may be that warp threads are more in number than the weft threads per inch in the fabric construction. Increase in both weft yarn twist and the number of weft yarn plies increased the bending length and flexural rigidity in both warp and weft directions. The reason for this may be that the fabric being of a complex structure, the stiffness of the yarn, which is dependent on twist and the number of plies, would affect the stiffness of the fabric favourably in both the directions. A comparison of the values of overall flexural rigidity for OE and ring yarn fabrics reveals that ring weft fabrics are generally stiffer than OE weft fabrics. Fabrics with maximum twist OE yarn (i.e. Tw020 and ThO 14) are comparable to those with minimum twist ring yarn (i.e. TwRI2 and ThRIU) in stiffness. Conclusions (I) OE yarns are weaker than the equivalent ring yarns and the weakness decreases with increase in twist and the number of plies used in the yarn. OE yarns are also more extensible than the equivalent ring spun yarns; increase in twist or number of plies in the yarn reduces the difference between the extensibility of the two yarns. Further. OE yarns are bulkier than the equivalent ring yarns because of the large diameter of the OE yarn. (2) When fabrics of identical construction are prepared from OE and ring yarns and are processed in an identical manner, fabrics prepared from OE yarns are weaker than the corresponding ring yarn fabrics. The difference in the strengths of the two fabrics reduces with increase in the number of plies. (3) Fabrics prepared from OE yarns are more extensible than the corresponding ring yarn fabrics. The difference between the extensibility of the two 158

6 BHARGAVA ct al.: CHARACTERISTICS OF OPEN-END & RING YARNS AND FABRICS fabrics reduces with increase in twist and the number of plies. (4) OE yarn fabrics exhibit lower tearing strength than the ring yarn fabrics. Increase in twist and the number of plies in the weft yarn increases the tearing strength in the direction in which the yarn is used. (5) OE weft yarn fabrics show poor abrasion resistance than the corresponding ring yarn fabrics. Increase in twist in weft yarn decreases the abrasion resistance, whereas increase in the number of plies in the weft yarn increases the abrasion resistance. (6) Use ofoe yarn in weft results in a fabric with a higher flexibility, and increase in twist and the number of plies in the weft yarn increases the fabric stiffness in general. Hence, the use of open-end yarn demands a judicious selection of yarn count, number of plies in the final yarn, twist levels of single and plied yarn, loom sett and the type of weave to be used for producing fabrics with the required performance characteristics. Acknowledgement The authors are thankful to Prof. R.C.D. Kaushik, Director, TIT, Bhiwani, for permission to publish this paper. References I Lord P R. Text Res J, 41 (1971) Salhotra K R, Sengupta A K & Haldar A K, Indian J Text Res, 5 (1980) Pillay K P R, Text Res J, 45 (1975) Mohamed M H & Lord P R, Text Res J, 43 (1973) Morris M A & Prato H T, Text Res J, 48 (1978) Rakshit A K, Comparison of the performance characteristics of open-end and ring yarn towelling fabrics, M. Text. thesis, Technological Institute of Textiles, Bhiwani, Palit S K, Comparative study of the characteristics of open-end and ring-spun polyester-viscose blended fabrics, M. Text. thesis, Technological Institute of Textiles, Bhiwani,