Apparel and Knitwear Physical and Mechanical Properties of Cotton/Spandex Fabrics by Mona M.A. Haji, Textiles and Clothing Department , College of Arts d Interior Design for Girls, Umm Alqura University, Makkah, Saudi Arabia Abstract Today, spandex is produced in US, Europe, Asia, and Middle East. The fabrics containing spandex is forecast to grow in the coming years. In this study, the physical and mechanical properties of cotton/spandex single jersey fabrics are investigated and the results were compared with fabric knitted from cotton alone and the effect of loop length on the fabric properties were also studied . The statistical analysis proved that the dimensional stability and air permeability is adversely affected by the percentage of spandex, whereas bursting strength crease recovery and pilling resistance rating have been improved. The loop length had a significant effect on fabric weight, bursting strength dimensional change, crease recovery , air permeability and pilling resistance rating. 1. Introduction Spandex is elastomeric fibers. It can be stretched repeatedly to at least twice Figure (1) The arrangement of polymer and hydrogen bonds in a relaxed and extended spandex fiber. their original length at room temperature; when the extending force is removed, they immediately return with force to their approximate original length. Spandex is a generic term, like polyamide or polyester. It defines a man-made fiber in which the fiber-forming substance is a synthetic chain of polymer containing at least 85% segmented polyurethane(1). It is white or transparent in its natural state and it can be dyed. The polymers in spandex fibers contain soft and hard segments (Figure 1). The soft segments Table I : Specifications of samples Blending Ratio 96% Cotton: 4% Lycra 92% Cotton: 8% Lycra Single Jersey 100% Cotton: 0% Lycra Structure 52 Loop length mm Fabric weight / m2 Number of Wales/cm Number of courses/cm 3.35 135 16 14 3 150 16 17 2.7 165 16 20 3.35 190 23 18 3 210 24 21 2.7 230 25 24 3.35 300 30 23 3 325 31 26 2.7 350 32 29 extend and retract under a pulling force; hydrogen bonds form between the hard segments of adjacent polymers (2). Spandex is always blended with other natural and synthetic fibers such as cotton, wool, silk, and linen. Different types of spandex material exist on the markets with different counts, this impose engineering the use of every type at different spun materials and fabric construction. The percentage of spandex used in the knitting industry depends on the fabric stretch required and fabric properties (3). Since the elasticity of these types varies from 60% to 300%, this is reflected on the final characteristics of knitted fabrics. When applying the bare type, we can introduce Spandex on every feeder, which is known as full plaiting. Different percentage of feeders can contain spandex material, in case of 50% it is known as half plaiting. There are many different counts and types of spandex on the market (4). "Lycra" is the trade name that DuPont uses for their particular formula of spandex that they sell to the textile industry. The type of fabric and it’s end use determine the amount and type of Lycra required to ensure optimum performance and aesthetics. Lycra can be stretched four to seven times its initial length, yet springs back to it’s original length once tension is released (5). Apparel and Knitwear 2. Function and features The use of Spandex in fabrics offers better fit on the body like a second skin and have good shape retention without any deformation throughout the life of the garment especially in knitted fabrics(6). In addition, the low moisture absorption and resistance to normal apparel exposure to sunlight and to common chemicals are other features of spandex (7). Comfortable fit in woven fabrics, freedom of movement, shape retention, excellent drape ability and crease recovery. Outstanding shape retention in knitwear(8). Used as a substrate for natural / synthetic leather or shoe uppers, Lycra provides 4-5% stretch in shoes to give maximum comfort to the wearer(9). Consistent quality effecting high yield in knitting. Almost 100% recovery in the garments. Good resistance to chemicals(10). 3. Experimental work 3.1 Materials and sample specifications The samples were knitted on a Convert weft knitted machine with 66 feeders (24 gauge, 22" diameter, 1632 total needle count, with a positive yarn feeding system) Marchizio circular knitting machine. Ne 30/1 ring spun cotton yarn and 44 dtex spandex were used in the research . Determination of air permeability: Fabric drape was measured by using Elester L 130apparatus according to (B.S2925:1958)(16). 4. Results and discussions 3.2 Laboratory Testing Fabric weight Determination of fabric weight: This test was carried out by using Mettler H 30 apparatus according to the American Standard specifications of (ASTM-D 3776-79) (11). Determination of wale & course density: This test were determined at ten different places on every sample calculated with a magnifying glass, and the average values were calculated. Determination of crease recovery:Crease recovery was measured by using Wrinkle recovery tester according to ( ASTM D-1295-67) (12). Determination of pill rating: This test was carried out by using, Martindale Tester, according to (ASTM D4970 D 4960) (13). Determination of dimensional stability: This test was carried out according to (B.S 3424: 1974)(14). Determination of bursting strength: This test was carried out by using, Bursting Tester for clothing, according to (ASTM D3787-89) (15). It was obvious from figure (2) that., the loop length has a significant effect on the fabric weight for all fabrics, as the loop length increases, the fabric weights were decreased, this means that the higher the loop length, the lower the fabric weight. The increase in loop length from 2.7 to 3.35 mm leads to a decrease in fabric fabric weight up to 23%, 21% and 17% for 0% lycra, 4%lycra and 8% lycra, respectively for all samples. The significant effect of loop length on fabric weight for all tested fabrics can be attributed to the decrease in the loop length help to increase in stitch density which lead to increase to fabric weight. The statistical analysis also showed that, the there is direct relationship between lycra ratio and fabric weight as the amount of lycra increase the fabric weight increase, because the greater the amount of lycra, the tighter the fabric weight. By applying the ANOVA technique we found that there is a significant effect of both lycra ratio and loop length on fabric weight P value (0,.002) respectively . Wale density Figure (2) Relationship between loop length and their fabric weight at different Lycra ratio. Figure (3) Relationship between loop length and their number of wales/cm at different lycra ratio. Figure (4) Relationship between loop length and their number of courses /cm at different lycra ratio. Figure (5) Relationship between loop length and their crease recovery at different lycra ratio. Figure (3) illustrates the relationship between the amount of lycra and the wale density for different loop length . It is shown that, the amount of lycra is significant effect on the wale density for all tested fabrics. The greater the amount of Lycra, the higher the wale density is. The increase in the amount of Lycra from 0% to 8% leads to an increase in wale density up to 100%. The loop length has an insignificant effect on the wale density. This can be due to the fact that the wale per cm depends in the first place on the machine gauge, while after wet relaxation this depends upon the fabric construction as all the other properties. By applying the ANOVA technique It was found that the lycra ratio had the most significant influence on wale density P value (0) 53 Apparel and Knitwear rating for the tested samples produced from single Jersey at three different loop length. It is shown that, amount of lycra has a significant effect on the pill rating for all tested fabrics as amount of lycra increase, the pill rating increase, this means that the pill formation decrease as amount of lycra increase, because the greater the amount of lycra , the tighter the fabric. Figure (6) Relationship between loop length and their pilling resistance rating at different lycra ratio. Figure (8) Relationship between loop length and their dimensional stability widthwise at different lycra ratio. Figure (7) Relationship between loop length and their dimensional stability lengthwise at different lycra ratio. Figure (9) Relationship between loop length and their bursting strength at different lycra ratio. Course density Figure (4), illustrate the relationship between the amount of lycra and the course density at three different loop length. It is shown that, the amount of lycra is significant effect on the course density for all tested fabrics. The greater the amount of lycra, the higher the course density is. The increase in the amount of lycra from 0% to 8% leads to an increase in wale density up to 60% for all samples, because the greater the amount of lycra, the tighter the fabric. The statistical analysis also showed that, the there is inverse relationship between loop length and course density as the loop length increase the course density decrease. This could be attributed to that the less the loop length the less spaces between courses leading to the inability of the fabric to have greater number of courses. By applying the ANOVA technique we found that there is a significant effect of both lycra ratio and loop length on course density P value (0,.002) respectively. Crease recovery angle Figure (5) show the relationship between the amount of lycra and the crease recovery at three levels of loop 54 length. It is shown that, for all tested samples the amount of lycra has a significant effect on the crease recovery angle. The higher the amount of lycra, the higher the crease recovery angle is. The increase in the amount of lycra from 0% to 8% leads to an increase in crease recovery up to 25%. This means that, as the amount of lycra increases, the crease resistance also increases, because the greater the amount of lycra more the elasticity of the fabric. The statistical analysis also showed that, the there is inverse relationship between loop length and crease recovery angle as the loop length increase the crease resistance decrease. The significant effect of the loop length on the crease recovery can be attributed to the less loop length associated with increasing the fabric weight which leads to resist the crease deformation. By applying the ANOVA technique we found that there is a significant effect of both lycra ratio and loop length on crease recovery angle P value (0,.001) respectively. Pilling resistance rating Figure (6) illustrate the relationship between the amount of lycra and the pill It is obvious that, loop length has a significant effect on the pill rating for all tested fabrics, as the higher in loop length, the lower the pill rating is this means that the pill formation decrease as loop length decrease. The significant effect of the loop length on the pill rating can be attributed to that the, decreasing in loop length helps to reduce pilling by tightening up and compactness the of construction and making fiber migration more difficult. By applying the ANOVA technique It was found that the lycra ratio had the most significant influence on wale density P value (0). Dimensional stability in the lengthwise direction Figure (7) illustrate the relationship between the amount of lycra and dimensional stability in the lengthwise direction at three different loop length. It is shown that, the amount of lycra has a significant effect on the dimensional stability in the lengthwise direction for all samples, as the higher the amount of lycra, the higher the dimensional change is, (inverse relationship). The statistical analysis also showed that, the there is inverse relationship between loop length and dimensional stability in the lengthwise direction as the loop length increase the dimensional change decrease. The significant effect of the loop length on the dimensional change. By applying the ANOVA technique we found that there is a significant effect of both lycra ratio and loop length on dimensional stability in the lengthwise direction P value (0,.001) respectively. Dimensional stability in the crosswise direction Figure (8) illustrate the relationship between the amount of lycra and dimensional stability in the crosswise direction at three different loop length. It is shown that, the amount of lycra has a significant effect on the dimensional Apparel and Knitwear stability in the crosswise direction for all samples, as the higher the amount of lycra, the higher the dimensional change is, (inverse relationship). The statistical analysis also showed that, the there is inverse relationship between loop length and dimensional stability in the crosswise direction as the loop length increase the dimensional change decrease. The significant effect of the loop length on the dimensional change. By applying the ANOVA technique It was found that the lycra ratio had the most significant influence on dimensional stability in the crosswise direction P value (0.006). Bursting strength Figure (9) illustrate the relationship between the lycra ratio and the bursting strength at three different loop length. It is shown that, the amount of lycra is significant effect on the bursting strength for all tested fabrics, as amount of lycra increase, the bursting strength increase, because the greater the amount of lycra, the tighter the fabric. The statistical analysis also showed that, the there is inverse relationship between loop length and bursting strength as the loop length increase the bursting strength decrease. The significant effect of the loop length on the bursting strength can be attributed to the less loop length associated with increasing the fabric weight which leads to higher bursting strength. By applying the ANOVA technique we found that there is a significant effect of both lycra ratio and loop length on bursting strength P value (0,.001) respectively . length. It is clear, for all tested samples the amount of lycra has a significant effect on the air permeability, as the amount of lycra increases, the air permeability decreases. The reduction in the fabric air permeability with increasing the amount of lycra can be attributed to the higher bulk, compactness, and the cloth thickness accompanying with a higher amount of lycra which offer resistance to the air permeability. It is obvious that, loop length has a significant effect on the air permeability for all tested fabrics, as the greater in loop length, higher the air permeability. The significant effect of the loop length on the air permeability can be attributed to that less loop length, less spaces between courses which offer resistance to the air permeability. By applying the ANOVA technique we found that there is a significant effect of both lycra ratio and loop length on air permeability P value (0 ,0) respectively . 5. Conclusion The following result are given as under: Air permeability: Figures (10) illustrate the relationship between the lycra ratio and air permeability, at three levels of loop All the parameters under study were significantly affected by the amount of spandex in the fabric and the loop length. It was found that, bursting strength, fabric weight, crease recovery and pilling resistance rating have been improved significantly by increasing in lycra ratio, but fabric air permeability and dimensional stability were decreased . Loop length had a significant effect on the air permeability, bursting strength, dimensional change, crease recovery angle and fabric weight. Pilling resistance rating is significantly affected by loop length and percentage of spandex. It was found that the loop length had the most significant influence on pilling resistance rating. References Figure (10) Relationship between loop length and their air permeability at different lycra ratio. 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