Feng Chia University, Taichung City 407, Taiwan, R.O.C. and Technology, Taichung 406, Taiwan, R.O.C.

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1 Advanced Materials Research Online: ISSN: , Vol. 627, pp doi: / Trans Tech Publications, Switzerland Manufacturing Technique and Property Evaluation of Cotton/Polyester/ Rubber Composite Warp Knit Jia-Horng Lin 1,2,b, Shih-Yu Huang 1, Hui-Yu Yang 1, Ching-Wen Lin 3,c, Jin-Mao Chen 1 and Ching-Wen Lou 4,a 1 Laboratory of Fiber Application and Manufacturing, Department of Fiber and Composite Materials, Feng Chia University, Taichung City 407, Taiwan, R.O.C. 2 School of Chinese Medicine, China Medical University, Taichung 40402, Taiwan, R.O.C. 3 Department of Fashion Design, Asia University, Taichung 41354, Taiwan, R.O.C. 4 Institute of Biomedical Engineering and Material Science, Central Taiwan University of Science and Technology, Taichung 406, Taiwan, R.O.C. a cwlou@ctust.edu.tw, b jhlin@fcu.edu.tw, c chingwen@asia.edu.tw Keywords: elastic knitted fabrics, warp knits, crochet machine, cotton yarn Abstract. Cotton fiber is a type of natural fibers. Using natural fibers to fabricate textile can not only decrease the consumption of synthetic fibers, but also reduce the environmental pollution. This study aims to fabricate elastic knitted fabrics and evaluate their properties. Polyester (PET) filaments and rubber threads serve as the warp while cotton yarn serves as the weft for warp knitting. A crochet machine makes the warp and weft into warp knits with desirable stretchability, during which the amount (single/double) and the ply number (1-, 2-, and 3-ply) of the weft are further varied. The resulting warp knits are evaluated for water absorption, air permeability, and mechanical properties. As demonstrated by the experimental results, the warp knits with single 1-ply weft (S1) yield an optimal air permeability of cm 3 /cm 2 /s and stiffness along the warp direction of 4.74cm. The warp knits with single 2-ply weft (S2) display an optimal tearing strength of 86N while the warp knits with double 3-ply weft (D3/3) has an optimal tensile strength of 708N. Introduction Knitting is a process to form the yarn into loops and then connect loops to form the knits. Knitted fabrics are divided into warp and weft knits. Warp knits are made by connecting the loops along the warp direction, and thus their yarns are neither easily disaggregated nor damaged by external force. Warp knitting demands a shorter production time and can use diverse materials, and thus are commonly used. Natural materials are increasingly used as a result of ever worse environmental pollutions; in particular, cotton fiber is the most commonly used in industrial textile due to it good texture and durability. From 2006 to 2012, Lin et al. have utilized fiber materials, Knit fabric in elastic knitted products [1-5]. This study uses both PET filaments and rubber threads as the warp and cotton yarn, the functional material, as the weft. On a chroche machine, the materials are warp-knitted into resilient knits, during which the amount (single/double) and the ply number (1-, 2-, and 3-ply) of the weft are varied. The water absorption, air permeability, and mechanical properties of the resulting warp-knitted fabrics are evaluated. Experimental Materials Polyester (PET) filaments (Universal Textile Co., Ltd., Taiwan, ROC) have a fineness of 150 denier (D) and filament counts of 48f. Combed cotton fiber (Tah Tong Textile Co., Ltd., Taiwan, ROC) has a fineness of 170D. Rubber threads (Ta Yi Plastics Enterprise Co., Ltd., Taiwan, ROC) is #39. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (# , Pennsylvania State University, University Park, USA-16/09/16,02:58:22)

2 Advanced Materials Research Vol Preparation of Samples A winding machine combines the 1-ply cotton yarn (75D) into 2- and 3-ply cotton yarn, respectively, serving as the weft. On a crochet machine, the warp (PET filaments and rubber threads) and the weft is fabricated into warp knits. During the knitting process, only PET filaments (the first warp) are formed into loops, which interlock each other with enveloping the vertical rubber thread (the second warp) and horizontal cotton weft. The resulting warp knits with single 1-, 2-, and 3-ply weft are defined as S1, S2, and S3; warp knits with double 1-, 2-, and 3-ply weft are denoted as D1/1, D2/2, and D3/3. Finally, S1, S2, S3, D1/1, D2/2, and D3/3 are evaluated for their tensile strength, tearing strength, stiffness, water absorption, and air permeability. The control group is warp knits with the same warp but one or two 1-ply PET weft. Figure 1 shows the setup of the warp-knitting. Figure 1. The setup for warp knits of a) single weft and b) double weft. Air Permeability A Textest (FX3300, Switzerland) evaluates the air permeability of the warp knits as specified in D The number of samples measuring 25cm 25cm is 10 pieces of each specification. Stiffness A Flexometer (Kuoeh Tsuan Scientific Company, Taiwan, ROC) is employed to measure the stiffness of the samples according to cantilever method specified in CNS The warp knits are cut into mm 2 along the warp and weft direction, respectively. Next, they are mounted on the platform of the instrument, and the length (cm) of the sample protruding the platform horizontally before starting bending downward represents the stiffness. The longer the protruding length, the greater the stiffness. Water Absorption Five samples cut along the warp and weft direction of the warp knits, separately, and sample size is mm 2. As specified in CNS5611, one end of the samples (2cm long) is dipped in water for 10 minutes and the lengths of the water moving in them are recorded and averaged for the mean. Tensile Strength The tensile strength along the warp and weft directions of the warp knits are evaluated by a HT-9101 (Hung Ta Instrument Co., Ltd, Taiwan, ROC) as specified in CNS6842. The settings are: sample size is mm 2 ; the number of the samples is 10 of each specification; the distance between fixtures is 5cm; and the tensile speed is 300 mm/min. Tearing Strength The tearing strength along the warp and weft directions of the warp knits are evaluated by a HT-9101 (Hung Ta Instrument Co., Ltd, Taiwan, ROC) as specified in CNS The settings are: sample size is mm 2 ; the number of the samples is 10 of each specification; the distance between fixtures is 10cm; and the tearing speed is 10 cm/min.

3 304 Advances in Textile Engineering and Materials Results and Discussion Figure 1 (a) shows that the air permeability of the warp knits with single and double cotton weft is and cm 3 /cm 2 /s, respectively; and that of the warp knits with single and double PET weft (control group) is cm 3 /cm 2 /s and cm 3 /cm 2 /s, respectively. It shows that there is no significant difference in the air permeability of the warp knits and control group, as PET filament and cotton fiber have a similar fineness, which does not influence the size of pores between yarns in them. Regardless of whether it is PET or cotton weft, the air permeability of the warp knits with single weft is greater than that with double weft, as single weft has a lower amount of fibers than double weft, resulting in a larger size of pores between the weft and warp, and thus, a greater air permeability. Figure 1 (b) reveals that the air permeability of S1, S2, S3, D1/1, D2/2, and D3/3 is 224.6, 125.6, 81.79, , 57.7, and cm 3 /cm 2 /s, respectively. Regardless of the amount of the weft, the air permeability is inversely proportional to the ply number of the weft. When the 1-ply cotton yarn is combined into 2- or 3-ply, the weft has more fibers, which decreases the size of the pores between the weft and warp. As a consequence, the air permeability decreases when the ply number of the weft increases. Figure 1. Air permeability of the warp knits as related to a) different 1-ply weft and b) ply number of the cotton weft. Figure 2 (a) compares the water absorption of the warp knits with single 1-ply PET and cotton weft. The warp knits with cotton weft demonstrate lower water absorption as the cotton weft is sized before warp knitting. As seen in Figure 2 (b), when the ply number of the weft increases, the water absorption of the warp knits decreases. Regardless of whether the warp knits have single weft or double weft, the water absorption along the warp is greater than that along the weft. This is due to the continuity of the rubber threads, which leads the water to move along the warp via the cotton weft. As the cotton weft is previously sized; therefore, an increase in the ply number of cotton weft hampers the water movement, resulting in decreased water absorption. At the same time, warp knits with single weft demonstrate greater water absorption, as comparing to double weft, single weft has a smaller amount of cotton and is less restricted by the sizing of cotton yarn. Figure 2. Water absorption along the warp and weft of the warp knits as related to a) weft type and b) ply number of the cotton weft.

4 Advanced Materials Research Vol Figure 3. The stiffness along the warp and weft of the warp knits as related to a) weft type and b) ply number of the cotton weft. Figure 3 (a) shows that there is no significant difference in the stiffness between the warp knits with PET and cotton weft, as cotton fibers and PET filaments have a similar fineness. For all warp knits, the stiffness of double weft is greater than that of single weft, and the stiffness along the weft is greater than that along the warp. The warp knits with double weft contain a larger amount of the cotton fibers, resulting in a greater stiffness, as seen in Figure 3 (b). The stiffness along the warp and weft is in fact associated with the fibrous orientation (the degree to which the fibers are arranged in the same direction). When at high fibrous orientation, the resulting knits exhibit a greater drapability. The warp (PET filaments and rubber threads) in the warp knits has great fibrous orientation, and thus the stiffness along the warp of the warp knits is lower. Figure 4 (a) reveals that the tensile strength of the warp knits with PET weft is greater than that with cotton weft, as the PET fibers have a greater strength than cotton fibers do. In addition, the tensile strength along the warp is smaller than that along the weft, regardless of whether the warp knits have single or double weft. This is because when the warp knit is stretched along the warp, rubber threads transform leaving the PET filaments to take the force alone; in addition, the number of yarns in the warp is smaller than that in the weft. An increase in the number of yarns contributes to a greater tensile strength, as seen in Figure 4 (b). As within the same unit area, the greater the ply number of the weft, the higher the number of yarns, resulting in a greater tensile strength of the resulting warp knits. Figure 4. The tensile strength along the warp and weft of the warp knits as related to a) weft type and b) ply number of the cotton weft. Figure 5. The tearing strength along the warp and weft of the warp knits as related to a) weft type and b) ply number of the cotton weft.

5 306 Advances in Textile Engineering and Materials Figure 5 (a) reveals that regardless of the weft types, the warp knits have greater tearing strength along the weft than that along the warp. This is because when the warp knits are torn along the weft, the warp resists the tearing force. PET filaments and rubber threads have greater strength than cotton yarn, resulting in a greater tearing strength along the weft. The same trend can be observed when the warp knits have single 2- and 3-ply cotton weft (i.e., S2 and S3), as seen in Figure 5 (b). However, when the warp knits with double 2- and 3-ply cotton weft (i.e., D2/2 and D3/3), both tearing strengths along the warp and weft are similar to that along the weft of S2 and S3. This can be attributed to the increase in cotton yarn, which reinforces the overall structure of the warp knits, resulting in high tearing strengths both along the warp and weft. Conclusion This research successfully produces the elastic warp knits. When the knits have single 1-ply cotton weft, their air permeability and water absorption are the optimal, increasing by 8% and 30%, respectively. With an increase in ply number, the tensile strength, tearing strength, and stiffness of warp knits with double weft are 64%, 45%, and 50%, respectively, greater than that with single weft. Acknowledgements This work would especially like to thank National Science Council of the Republic of China, Taiwan, for financially supporting this research under Contract NSC E References [1] J. H. Lin, C. W. Lin, C. M. Lin, Y. C. Yang, T. T. Li and C. W. Lou: Applied Mechanics and Materials Vol (2012). [2] J. H. Lin, Y. T. Huang, C. M. Lin, Y. C. Yang and C. W. Lou: Advanced Materials Research Vol (2011). [3] J. H. Lin, Y. T. Huang, C. M. Lin, Y. C. Yang and C. W. Lou: Advanced Materials Research Vol (2011). [4] C. W. Lou, C. H. Lei, C. W. Chang, J. M. Chen, Chan-Hung Hsu, C. B. Huang and J. H. Lin: J Mater Process Tech Vol (2007). [5] C. W. Lou, C. H. Lei, C. W. Chang, J. M. Chen, Chan-Hung Hsu, C. B. Huang and J. H. Lin, "Optimal Process of Warp-Knitting Fabric with Multiple Functions", 7th Asia Pacific Conference on Materials Processing, Singapore, 2006.