Knitting Properties

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Effect of Heat Setting and Compacting on Elastic Properties

of Cotton/Spandex Knitted Fabrics

By: Cibi Vishnu. C,

Lakshmi Padmaraj, Sukanya. H,

Suresh Kumar. B, Dr. N. Anbumani

and Mr. M. Senthil Kumar

Effect of Heat Setting and Compacting on Elastic Properties of Cotton/Spandex Knitted Fabrics

By: Cibi Vishnu. C, Lakshmi Padmaraj, Sukanya. H, Suresh Kumar. B, Dr. N.

Anbumani and Mr. M. Senthil Kumar*

Department of Textile Technology PSG College of Technology, Coimbatore

*Lecturer

Department of Textile and Apparel Technology PSG Polytechnic College, Coimbatore

ABSTRACT Stretch fabrics are fabrics manufactured from elastomeric yarns thereby having high elastic properties. Elastic stretch (extension) and recovery of fabric is the important property for functional wear like sportswear. It gives better performance by providing freedom of body movement. The parameters observed during the manufacturing of the stretch fabric influences the final stretch properties such as the level of stretch and recovery of the fabric. INTRODUCTION The most important property requirement for stretch garment is in the order of body comfort fit, freedom of movement, breathability and durability. Further, fabric elastic recovery is as important as stretching. Good elasticity of fabric will make a good sportswear. The degree and direction of elasticity determines the end use of stretch garments. There are two methods by which stretch fabric can be manufactured. They are:

• Spandex Core Cotton Spun Yarn Converted Fabric • Spandex Back Plaited Cotton Knitted Fabric

In stretch yarns produced by using core yarn spinning system, spandex is used as core and cotton as sheath yarn. Stretch yarn production using core spinning is coming down because of lower production rate in spinning and inconsistency in quality (sheath covering effect and dynamic recovery). In order to overcome the limitations of core stretch yarn production, plaiting technique was adopted in knitting. In this method, bare spandex is directly fed along with normal yarn during knitting. Cotton and spandex is passed through the same feeder to form a loop and to produce a fabric. Normal knitting machine has separate attachment at the top of the machine for spandex feed.

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Not many attempts have been tried on elastic properties of spandex plaited knitted fabrics and hence it is necessary to evaluate the elastic properties of spandex plated knitted fabrics for the development of functional sportswear. So we have conducted a study on the effect of heat setting and compacting on the elastic properties of cotton / spandex knitted fabric. PURPOSE The purpose of the study is to find the effect of (a) heat setting temperature, (b) heat setting time, (c) compacting temperature and (d) compacting time on the elastic properties of the cotton/spandex stretch fabric. The fabric is produced from cotton and spandex by plaiting technique on a single jersey knitting machine. The fabric samples are given heat setting treatment for 3 temperatures (200°C, 210°C & 220°C) and 3 times (33 sec, 36 sec & 42 sec). Then compacting is carried out for 3 times (12 sec, 22 sec & 28 sec) and temperatures (70°C, 85°C & 100°C). A total of 12 samples are produced with different parameters. The 12 samples are tested for its elastic properties on an Elascometer and Instron tester. MATERIALS AND METHODS Cotton yarn of 40s count and spandex yarn of 40 denier were the raw materials used for the production of the stretch fabric. The fabric is produced on a single jersey knitting machine. Heat setting is given in order to maintain the dimensional stability of the fabric during subsequent processing and as well as in the final product. The normal parameters followed by the industries during the process of heat-setting of the cotton/spandex are:

Temperature: 220°C Time : 36 to 40 seconds

We have produced fabric samples by varying the heat setting time and temperature. Samples 1, 2 and 3 were produced by varying the heat setting time. Sample 1 was given heat setting for 33 seconds, Sample 2 for 36 seconds and Sample 3 for 42 seconds. The heat setting temperature for all the samples 1, 2 and 3 was the same -220°C. Samples 4, 5 and 6 were given heat setting treatment at various temperatures for the constant time of 36 seconds. Sample 4 was given heat setting treatment at 200°C, sample 5 at 210°C and sample 6 at 220°C. The fabric was then dyed using burgundy colour reactive dye under usual industry parameters. The fabric is given compacting treatment by varying the time and temperature like in the case of heat setting. Samples 7, 8 and 9 are given compacting at different temperatures. Sample 7 is compacted at 70°C, sample 8 at 85°C and sample 9 at 100°C. And samples 10, 11 and 12 are given compacting for time periods of 12 seconds, 22 seconds and 28 seconds respectively. Tests were performed using Elascometer and Instron tester. In the test for maximum stretch and recovery using the elascometer, the fabric sample was benchmarked with 50cm length and 12.5cm width. It was then folded lengthwise

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so that the length becomes 25cm. The free ends of the fabric sample were stitched together. Markings were made 6.25cm away from the ends of the fabric so that 12.5cm was obtained in the centre as the portion of the fabric to be tested. It was then taken for loading. In the test for low strain elastic properties using the instron tester the fabric sample was benchmarked with 150mm length and 25 mm width. The fabric was clamped 25mm away from the ends of the sample at both ends such that 100mm was the length of the specimen sample undergoing the test. It was then subjected to stretching. The fabric was tested by stretching it to 20% and 30% elongation levels. The samples were stretched to 120mm and 130mm respectively and the stress-strain curves were plotted. The graphs were then studied and the results were interpreted. RESULTS AND DISCUSSIONS 1. Effect of Heat Setting Time on the Elastic Properties

Elastic Recovery

92939495969798

H-33 S H-36 S H-42 S

Heat Setting Time

Ela

stic

Rec

over

y

ER-L

ER-W

Elastic Stretch

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100

H-33 S H-36 S H-42 S

Heat Setting Time

Ela

stic

Stre

tch

ES - L

ES - W

Graph 1(a) Graph 1(b)

S No. HS Time(s) ES-L ES-W 1 33 70.4 76.0 2 36 64.0 76.8 3 42 56.0 70.4

S No. HS Time(s) ES-L ES-W1 33 96.0 93.6 2 36 96.0 94.4 3 42 96.8 95.2

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Graph 1(c)

Elastic Recovery % - Waleswise

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H-33 S H-36 S H-42 S

Heat Setting Time

Ela

stic

Rec

over

y %

20% Elongation

30% Elongation

Elastic Recovery % - Coursewise

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H-33 S H-36 S H-42 S

Heat Setting Time

Ela

stic

Rec

over

y %

20% Elongation

30% Elongation

Graph 1(d)

S No. HS Time(s) 20% 30% 1 33 75.00 80.00 2 36 48.00 62.86 3 42 72.00 69.44

S No. HS Time(s) 20% 30% 1 33 83.83 78.23 2 36 73.21 64.95 3 42 72.95 40.03

From Graph 1(a), it is seen that the elastic stretch of the fabric decreases slightly as the heat setting time is increased. Graph 1(b) shows that the recovery increases with increase in heat setting time. Graph 1(c) and 1(d) showing the elastic recovery % along the wales and course direction shows that the recovery % decreases with increasing heat setting time in the case of wales and decreases and finally increases in the case of courses.

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2. Effect of Heat Setting Temperature on the Elastic Properties Graph 2(a)

Elastic Recovery

9394959697

H-200 C H-210 C H-220 C

Heat Setting Temperature

Ela

stic

Rec

over

y

ER-L

ER-W

Elastic Stretch

556065707580

H-200 C H-210 C H-220 C


Ela

stic

Stre

tch

ES - L

ES - W

Graph 2(b)

S No HS Temp(°C) ES-L ES-W4 200 96 94.4 5 210 96 94.4 6 220 96 94.4

S No HS Temp(°C) ES-L ES-W4 200 69.60 76.80 5 210 68.00 74.40 6 220 64.00 72.80

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Graph 2(c)


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100

H-200 C H-210 C H-220 C


Elas

tic R

ecov

ery

%

20% Elongation

30% Elongation


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H-200 C H-210 C H-220 C


Elas

tic R

ecov

ery

%

20% Elongation30% Elongation

Graph 2(d)

S No HS Temp(°C) 20% 30% 4 200 77.77 81.48 5 210 75.86 74.51 6 220 73.21 64.95

S No HS Temp(°C) 20% 30% 4 200 85.53 77.10 5 210 54.41 66.67 6 220 48.00 62.86

Graph 2(a) shows a slight decline in the elastic stretch as the heat setting temperature is increased. Whereas, the value of recovery remains unaffected with the increase in temperature as shown in Graph 2(b). In the case of elastic recovery % with respect to wales and courses, Graph 2(c) shows slight decline in recovery % with increase in temperature and Graph 2(d) shows best recovery % at the lowest heat setting temperature. Hence the lowest temperature of 200°C can be considered as ideal temperature for heat setting.

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3. Effect of Compacting Temperature on the Elastic Properties Graph 3(a)

Elastic Stretch

0

50

100

C- 70 C C-85 C C-100 C

Compacting Temperature

Ela

stic

Stre

tch

ES - L

ES - W

Elastic Recovery

90

92

94

96

98

C- 70 C C-85 C C-100 C


Ela

stic

Rec

over

y

ER-L

ER-W

Graph 3(b)

S No Compacting Temp(°C)

ES-L ES-W

7 70 62.4 72.0 8 85 58.4 64.8 9 100 64.0 76.8


ES-L ES-W

7 70 97.6 93.6 8 85 97.6 96.8 9 100 96.0 94.4

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Graph 3(c)


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100

C-70 C C-85 C C-100 C


Ela

stic

Rec

over

y %

20% Elongation

30% Elongation


0

50

100

C-70 C C-85 C C-100 C

Compact ing Temperat ure

20% Elongation

30% Elongation

Graph 3(d)


20% 30%

7 70 84.00 83.33 8 85 77.50 66.67 9 100 73.21 64.95


20% 30%

7 70 60.97 58.76 8 85 75.00 76.28 9 100 48.00 62.86

The effect of compacting temperature is depicted by the graphs above. Graph 3(a) shows that the elastic stretch value decreases and then increases with increase in compacting temperature. Whereas Graph 3(b) shows the decrease in elastic recovery values with increase in compacting temperature. Graph 3(c) and Graph 3(d) shows the elastic recovery % along wales and course direction and there is observed to be a decrease in the recovery % as the temperature increases in both the cases. Hence it is necessary to optimise the compacting temperature for good elastic properties.

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4. Effect of Compacting Time on the Elastic Properties Graph 4(a)

Elastic Stretch

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C-12 S C-22 S C-28 S

Compacting Time

Ela

stic

Stre

tch

ES - L

ES - W

Elastic Recovery

90

92

94

96

98

C-12 S C-22 S C-28 S

Compacting Time

Ela

stic

Rec

over

y

ER-L

ER-W

Graph 4(b)

S No. Compacting Time(s)

ES-L ES-W

10 12 97.6 93.6 11 22 96.0 94.4 12 28 96.8 94.4

S No. Compacting Time(s)

ES-L ES-W

10 12 58.4 75.2 11 22 64.0 76.8 12 28 56.0 77.6

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Graph 4(c)

raph 4(a) shows the variation in the values of elastic stretch with increase in

S No. Compacting 20% 30%

Graph 4(d)

Time(s) 10 12 79.24 70.27 11 22 48.00 62.86 12 28 75.86 69.44

S No. Compacting 20% 30% Time(s)

10 12 88.64 71.05 11 22 73.21 64.95 12 28 60.71 63.75


020406080

100

C-12 S C-22 S C-28 S

Compacting Time

Ela

stic

Rec

over

y %

20% Elongation

30% Elongation


020406080

100

C-12 S C-22 S C-28 S

Compacting Time

Ela

stic

Rec

over

y %

20% Elongation

30% Elongation

Gcompacting time. But good stretch is obtained between 12 seconds and 22 seconds of compacting. Similarly, Graph 4(b) best values of elastic recovery achieved between 12 and 22 seconds of compacting. The graphs 4(c) and 4(d) show the best value of elastic recovery % along wales and courses respectively being achieved by sample no 10 with 12 seconds of compacting Hence the compacting time should be fixed between 12 and 22 seconds in order to attain best elastic properties.

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CONCLUSION

The following conclusions were derived from this study: 1) The heat setting time influences the elastic properties of the stretch fabric.

Least time gives best elastic stretch with maximum loading whereas high elastic recovery is achieved with longer duration of heat setting. Lower heat setting time also gives high values of elastic recovery % as revealed during testing of low strain elastic properties. Hence it is necessary to optimise the time duration of heat setting for required stretch and recovery properties.

2) The heat setting temperature also influences the properties of the fabric. Low

temperature of heat setting gives best elastic stretch and also good values of elastic recovery %. But heat setting temperature has no influence on the elastic recovery of the fabric. Hence a low value of heat setting temperature may be adopted during the manufacture of cotton / spandex stretch fabrics.

3) The elastic properties of the fabric are also influenced by the compacting

temperature. The values of stretch and recovery vary as the compacting temperature changes. Hence it is essential to optimise the compacting temperature to produce stretch fabrics with required properties.

4) The compacting time also influences the elastic properties of the fabric. The

values of stretch and recovery varied as the time changed. The elastic stretch and recovery values were good at 22 seconds processing, while the elastic recovery % values were good at 12 seconds processing. Hence it would be suggested to optimise the processing time between 12 and 22 seconds to produce fabric with good elastic properties.

REFERENCES

1. Voyce J, Dafniotis P and Towlson S, “Textiles in Sport – Chapter 10: Elastic Textiles”, Woodhead Publications, Invista (Switzerland), pp. 204-230

2. Rozelle, Walter N, “Spandex: Miracle Fibre Now Coming Into Its Own”, Textile World , Vol. 147, January 1997, pp. 80-85

3. Luke, John E, “Stretch Challenge”, Textile World, Vol. 152, January 2002, pp. 46-49

4. Borland, Virginia S, “Spotlight on Stretch”, Textile World, Vol. 155, May 2005, pp. 36-38

5. Luke, John E, “Stretch: Active VS Easy”, Textile World, Vol. 1553, December 2003, pp. 38-40

6. ASTM: D 2594- 99a – 2004, “Standard Test Method for Stretch Properties of Knitted Fabrics Having Low Power”

7. Hansen, Arnold M. and Fletcher, Hazel M., “Elastic Recovery in Cotton Knitted Fabrics”, Textile Research Journal, November 1946, pp. 571-575

8. Mukhopadhyay, A, Sharma, I C and Mohany, A , “Impact of lycra filament on extension and recovery characteristics of cotton knitted fabric”, Indian Journal of Fibre & Textile Research, Vol. 28, December 2003, pp. 423-430

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9. Fletcher, Hazel M, Hansen, Arnold M and Duensing, Mary Ellen, “Method of Evaluating the Elastic Properties of Knitted Fabrics”, Textile Research Journal, February 1949, pp. 94-96

10. Ibrahim, S M, “Mechanisms of Stretch Development in Fabrics Containing Spandex Yarns”, Textile Research Journal, August 1966, pp. 696-705

11. Bardhan, M. K. and Sule, A. D, “Anatomy of Sportswear and Leisurewear: Scope for Spandex Fibres”, Man Made Textiles in India, March 2001, pp. 81-86

12. Marmarali, Bayazit A, “Dimensional and Physical Properties of Cotton / Spandex Single Jersey Fabrics”, Textile Research Journal, January 2003, pp. 11-14

13. Saravanan D, Timble N.B, Gunasekar E and Kandasamy V A, “ Influence of Compacting on Knitted Fabrics”, IE(I) Journal-TX, Volume 88, February 2008, pp. 13-16

14. www.instron.com

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Knitting Properties

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