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Knitting & Hosiery
  Loop length & polyester-Lycra air-covered knitted fabric

The knitted fabric with a loop length of 2.5 mm has better appearance than the fabrics of other loop lengths, and in particular 10% stretch level shows a better appearance for 2.5 mm loop length, affirms C Prakash.

Today fashion designers are much conscious than ever and have up-to-date information about the latest fashion trends. The present-day consumer demands fashionable garments, which offer comfort and style, stretch and flexibility, freedom and figure enhancement, as he takes it as the tool of expressing his personality. As far as comfort is concerned, polyester/cotton blends are more popular than pure polyester. All cotton garments may be comfortable but have wrinkle problems. It is here Lycra comes to our help in offering wrinkle resistance and garment integrity while offering extra comfort. The wearer of Lycra-containing garment feels less fatigued and muscle strain than the one wearing garments without Lycra. This value of Lycra is well recognised by the fabric and apparel manufacturers as well as the consumers. 

The ongoing influence of casual clothing of lifestyle is boosting the popularity of Lycra-containing garment. As casual work attire becomes more popular, Lycra allows these types of garments more comfort. Additionally, Lycra provides a greater degree of wearability, wrinkle recovery and crease retention, making it the perfect compliment to the most garments. 

Researchers have found that natural fibres like cotton, silk, wool offers comfort and aesthetic properties while synthetic fibres like nylon, polyester, and polyurethane are more known for strength and elasticity; in other words, neither natural nor synthetic fibres can fulfil these needs when used singly in the yarn. Blending of these natural and synthetic fibres homogeneously thus becomes essential to take the advantage of better properties. Blending these fibres with spandex/Lycra fulfils majority of the requirements of the consumer and it is found that Lycra is readily compatible with most other fibres, including nylon, polyester, acetate, polypropylene, acrylic, cotton, wool, and rayon. However, the proportion of Lycra in the blends with these fibres varies significantly depending upon the end uses and application of the materials. 

This article is the outcome of studies done on the dimensional properties of knitted fabrics produced from air-covered elastomeric yarn. Here, Lycra-polyester air-covered yarns are knitted into single jersey fabric and their properties have been tested on this knitted structure. 

Methodology 

For the study of dimensional properties of Polyester/Lycra stretch yarn knitted fabric, single jersey plain knitted fabric samples at various loop lengths was produced. The fabric was dry-relaxed by keeping on flat surface for two days. On each sample the following test parameters were measured. 

  1. Wales per inch 

  2. Course per inch 

  3. Width of the fabric 

  4. Loop length 

  5. Thickness of the fabric 

Then the fabric was subjected to wet-relaxation and again the above parameters were measured. 

Results & discussion 

The test results for dry-relaxed state are given in Table 1 and for wet-relaxed state in Table 2.

Table 1. Effect of loop length on fabric parameters at dry relaxed state

Loop lengthmm (inch) CPI WPI Kc Kw N Ksx Kc/Kw
2.5 (0.098)
2.7 (0.106)
2.9 (0.114)
85
66
61
47
46
43
8.33
6.99
6.95
4.61
4.88
4.90
3995
3036
2623
38.37
34.11
34.05
1.81
1.43
1.41

From the table 1, it is found that the values of CPI, WPI, Kc, Kw, N, Ks and Kc/Kw vary with respect to loop length and also that there is a decrease in the CPI, WPI, Kc, N, Ks and Kc/Kw values and an increase in Kw value during dry relaxation process. Results are shown in Figures 1a and 1b. 


Table 2. Effect of loop length on Fabric parameters at wet relaxed state.

Loop lengthmm (inch) CPI WPI Kc Kw N Ksx Kc/Kw
2.5 (0.098)
2.7 (0.106)
2.9 (0.114)
100
102
104
75
65
63
9.8
10.8
11.86
7.35
6.89
7.18
7500
6630
6652
72.03
74.41
85.15
1.33
1.57
1.65

From the Table 2, it is found that the values of CPI, WPI, Kc, Kw, N, Ks and Kc/Kw vary with respect to loop length and that there is an increase in the CPI, Kc, Ks and Kc/Kw values, a decrease in WPI & N value and a subsequent decrease and increase in Kw value during wet relaxation process. Results are shown in Figures 2a & 2b. 


Table 3. Effect of stretching and heat setting on CPI and WPI (2.5 mm loop length).

Loop lengthmm (inch) Stretch level (%) Course / inch Wales/inch
2.5 (0.098)
10
20
30
50
70
90
110
111
114
117
119
123
58
54
50
46
44
36

From the Tables 3 to 5, it is found that CPI and WPI values vary with respect to stretch level at constant loop length and that there is a decrease in the wales per inch and increase in courses per inch.

From the Table 6, it is found that courses per inch values vary with respect to loop length and that there is a considerable increase in the course per inch after hot washing.

From the Table 7, it is found that wales per inch values vary with respect to loop length and also that there is a decrease in the wales per inch after hot washing.

From the Table 8, it is found that loop length values vary before and after wet relaxation and also that there is a minimal change in the loop length after hot washing.

From the Table 9, it is found that width of fabric values vary with respect to loop length and also that there is a decrease in the width of fabric after hot washing.

Figures 3. Effect of loop length on fabric thickness (Wet relaxed)

From the Table 10, it is found that thickness of fabric values vary with respect to loop length and also that there is a increase in the thickness of fabric after hot washing.

Conclusion

  • Courses per inch increases with an increase in loop length.

  • Wales per inch decreases with an increase in loop length.

  • Loop length increases after wet relaxation process when compared to that of the value set in the machine.

  • Thickness of fabric increases with an increase in loop length.

  • From the study, it is found that the dimension of fabric shows considerable change during wet relaxation.

  • The CPI increases from 17.65% to 70.49% and an average percentage change in CPI is 47.56% after Wet-Relaxation.

  • The WPI decreases from 59.57% to 31.75% and an average percentage change in WPI is 44.2% after wet-relaxation.

  • The fabric shows very good appearance when heat-set at all stretch levels at 180C in course direction.

  • A fabric with a loop length of 2.5 mm was found to have better appearance when compared to the fabrics of other loop lengths which have cloudy appearance. In particular 10% stretch level shows a better appearance for 2.5 mm loop length.

References

  1. Spandex Fibres - Scope and Application, Sitra focus, January 2003, Vol 20, No: 5, pp 5-8

  2. A Bayazit Marmarali: Dimensional and Physical properties of Cotton/Spandex Single Jersey Fabrics, Textile Research Journal, January 2003, Vol 73, No: 1, pp 11-14.

  3. K R Keshkari: Effect of Yarn Feed Length on Cotton Weft Knitted Fabrics, The Indian textile Journal, March 2002, pp 131-136.

  4. A Mokhopadhyay, I C Sharma and A Mohanty: Impact of Lycra Filament on Extension and Recovery Characteristics of Cotton Knitted Fabric, Indian Journal of Fibre & Textile Research, December 2003, Vol 28, pp 423-430.

  5. K Thangamani and V Natarajan: Dimensional Stability of Polyester/Lycra Air-covered Yarn, Knitted Fabrics, 2nd Indo-Czech Textile Research Conference, November 2003, pp 97-101.

  6. T Dias and G Lanarolle: Stitch Length Variation in Circular Knitting Machines due to Yarn Winding Tension Variation in the Storage Yarn Feed Wheel, Textile Research Journal, November 2002, Vol 72, No: 11, pp 997-1001.

  7. R P Nachane and G F S Hussain: Inverse Relaxation in Fabric, Indian Journal of Fibre & Textile Research, March 2003, Vol 28, pp 50-54.

  8. M Y Gudiyawar: Heat Setting Conditions and Mechanical Properties of Synthetic Fibre Fabrics - A Review, Synthetic Fibres, April/June 2003, pp 29-30.

Note: For detailed version of this article please refer the print version of The Indian Textile Journal February 2008 issue.

C Prakash
Lecturer Dept of Fashion Technology,
Sona College of Technology, Salem,
Tamil Nadu.
Email: cprakash566095@yahoo.co.in.

published February , 2008
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