x t i l e S cienc T e E Journal of Textile Science ... · PDF fileWhat actually happened due to heat setting the cotton spandex woven fabric and ... inside it for heat setting [6,7]

Volume 7 • Issue 5 • 1000319J Textile Sci Eng, an open access journalISSN: 2165-8064

Research Article Open Access

Islam, J Textile Sci Eng 2017, 7:5DOI: 10.4172/2165-8064.1000319

Research Article Open Access

Journal of Textile Science & EngineeringJo

urna

l of T

extile Science & Engineering

ISSN: 2165-8064

Keywords: Heat setting; Stenter machine; Heat setting procedure; Raw materials; Changes due to heat set; 3rd Party lab testing; Time and temperature curve; Equation; Microscopic view

IntroductionThe importance of this project work is tremendous in the field

of cotton spandex woven industry. Much efforts were given while experimenting it in the industry through hundreds of trials from which, some successful trials are included in this project work. Different temperature from higher to lower were applied while heat setting the cotton spandex woven fabric. Actually, heat setting is an application of heat by high temperature, due to which, resilience, elasticity, shape retention, crease resistance of fabrics is controlled. It enhances the strength, pilling performances and stretch ability of fabrics. It is necessary for the fabric of cotton spandex, polyester spandex, thermoplastic fibres, triacetate, synthetic fibres, elastomers and PAC fibres for dimensional stabilization. It also increases the crease proof properties. Basically, heat setting is a process, by which, heat is applied on a fabric to control some properties like stretch, growth, shrinkage, elastic recovery and extension etc. It is a thermal procedure that happens habitually in either a dry heating chamber or in a steam compartment. This process also provides the fibres, yarns or fabrics a dimensional stability and a little bit wrinkle resistance property those are also discussed in this project. It is also observed from the project that, due to heat setting the cotton spandex yarns, it strongly attached with the cotton fibre and also it also gripped the cotton fibre. Due to heat setting, the structural pattern of various materials was rearranged. Thermal shrinkage happened due to heat set the cotton spandex woven fabric which reduced creep, crimp and growth in normal condition [1-3].

Stretch and GrowthDue to the application of load on a fabric it will demonstrate a

AbstractThe aim of this project is to support the cotton spandex woven industry by manufacturing a wide variety of

stretched clothes where, some friendly performance like wearer comfort, super stretch, elasticity and recovery can be achieved powerfully. This project is a practical based project, which can help not only the textile learners but also the fabric developer in a massive way to manufacture cotton spandex fabric and also to control their properties strongly. The difficulties found during manufacturing cotton spandex woven fabric were enlisted them cordially and after that all of them were solved earnestly. Cotton spandex woven fabric cannot be manufactured without trial, all of which are strongly discussed in this project briefly. This project work is just not a paper work, but it is an achievement, which has been achieved by working strongly in the textile mills. It is to be mentioned that, “stretch or super stretch” is a welcoming property which can increase the comfort level of wearer, on the other hand there remains another paradoxical property named “growth” which has some de-welcoming properties on fabrics for which it is strongly needed to be controlled and all these things are carefully discussed in this project. Growth basically has an increasing relative property with the increment of stretch, but at a stage, this increased growth brings about some negative effect in fabric which creates some bad impression to wearer. Although, growth is proportional to its stretch but this growth should not be increased with the increment of stretch due to which, it is required to be controlled through some additional but necessary treatment like heat setting through stenter machine at fabric’s wet processing zone. What actually happened due to heat setting the cotton spandex woven fabric and what changes happened in its internal structure that is also seen in microscope and analysed the differences and discussed it here in this project work.

Investigating an Appropriate Temperature for Heat Setting in a Stenter Machine to Control the Stretch and Growth of a Cotton Spandex Woven FabricIslam S*Sinha Textile Group as a Fabric Technologist, Bangladesh University of Textiles, Dhaka, Bangladesh

*Corresponding author: Islam S, Sinha Textile Group as a Fabric Technologist, Bangladesh University of Textiles, Dhaka, Bangladesh, Tel: +880 2-9114260; E-mail: [email protected]

Received September 14, 2017; Accepted September 21, 2017; Published October 15, 2017

Citation: Islam S (2017) Investigating an Appropriate Temperature for Heat Setting in a Stenter Machine to Control the Stretch and Growth of a Cotton Spandex Woven Fabric. J Textile Sci Eng 7: 319. doi: 10.4172/2165-8064.1000319

Copyright: © 2017 Islam S. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

property like springiness, which is called stretch. The fabrics whose are made by mixing with elastane and have a property of elasticity or springiness is called stretch fabric. Fabric’s elasticity can be of many types like cross-elasticity, longitudinally elasticity and bi-elasticity. Mono-stretch is the stretch ability of a material that can stretch only in one direction, either in the warp direction or in the weft direction. Bi-stretch is the stretch ability of a material that can stretch in both two directions like in the warp direction and in the weft direction. Super stretch is the fabric which has a large volume of elasticity in both directions due to having high percentage of elastane. Stretch ability of a fabric is measured by calculating the length difference in between the application of load/tension and after releasing the load. Fabric will be stretched due to the application of load, but after releasing the load and after relaxing the fabric, it will try to shrink to its earlier original position. However, due to the application of load this fabric cannot go back to its earlier original position, this increment of length is called growth [4-5].


Page 2 of 9


Stages of Heat SettingHeat setting is done in three different stages like grey fabrics,

scoured fabric (after scouring) and after mercerization. Heat setting of mercerized fabric is best suited for good dimensional stability, good dyeing actions, better crease resistance properties and for better pilling performances.

Temperature for heat setting

Temperature varies for the construction of different types of fabrics. Higher temperature like 200°C is applied for heavy weight fabric, 170°C to 180°C is applied for medium weight fabric and 160°C is applied for light weight fabric.

Machine for heat setting

Generally, in industries, Stenter machine is used for heat setting, stretching, drying and finishing of Fabrics. It has two endless chains, which have an adjustable distance within them. Basically, it has a length of 80 to 120 feet and a width of 80 to 100 inches.

Fabric is heated with a blast of hot air. Speed of this machine may be from 15 to 50 meter/minute with a temperature of 160 to 220°C that depends on the type, nature and thickness of fabrics.

Stenter MachineIt is a machine that is used to do some activities like-chemical

finishing treatment, curing treatment, heat setting, adjusting width, controlling GSM, controlling shrinkage etc. Stenter machine has some components like bath, stenter chain, burner, circulating fans, exhaust fans, winder, pin etc.

Heat setting procedure in a stenter machine

Batcher is used to collect the fabric and to feed it into the stenter machine. There is a padder where only water is used to damp/wet the fabric otherwise it can be damaged while heat setting. There is an endless stenter chain with its spiky pins at the edge to grip the fabric at selvedge and to draw it forward. Basically, in a stenter machine, there are 8 to 10 chamber, which contain burners, circulating fans to blow air, exhaust fans to suck all the hot air within the chambers. Warp elongation is done by attraction roller. Burner increases temperature inside it for heat setting [6,7].

Heat Setting Parameters• Name of the machine: M-4136 Santex Stenter Frame Year

2003

• Width: Up to 3400 mm or 133.85”

• Type: Vertical pin chain

• Temperature: 230° C heating (maximum)

• Speed: 20 Meter/Minutes to 40 Meter/Minutes

• Temperature taken: 160°C to 220°C

• Width Taken: Practically fabric is stretched by ½ inches than its original width for heat setting properly

• Bath chemicals: Water for dampening the fabric, otherwise fabric may be burnt while heat setting. 5 g/litre of acetic acid is also applied if fabric is taken after mercerization due to controlling of pH.

Materials and MethodsBasically, Lycra is a registered trademark that is used for DuPont's

elastane filament. Elastane is a generic term, like polyamide or polyester. It is a manmade fibre, where the fibre forming material is a synthetic chain polymer that contains minimum 85% segmented polyurethane. Heat setting of cotton spandex fabric is a critical procedure. During heat setting process, fabric is passed through the stenter machine continuously. Any stoppage or minute changes in the machine parameters will affect the stretch property of fabric. The measurement of stretch and growth is measured in ASTM standards. It is not possible to control the stretch and growth of cotton elastane fabric without heat setting. The best technique to heat set the fabric after mercerization, as in this stage heat can be applied properly.

Raw MaterialsCotton spandex woven fabric is the fundamental raw material for

this project. Most of the industrial engineers refer different types of fabric with different weave and construction with a view to investigate them properly and come back with a logical fruitful result. In this project, three types of fabrics were tested for this process mentioned below:

1. Cotton spandex fabric of construction 10 × (10+70D)/78 × 50

2. Cotton spandex fabric of construction 20 × (12+70D)/136 × 60

3. Cotton spandex fabric of construction 32 × (32+70D)/190 × 80.

Experiment 01Fabric details

• Fabrication: 98% Cotton 2% Spandex Solid Dyed Twill

• Construction:10 × (10+70D)/78 × 50

• Weave: 3/1 LHT

• Weight: 9.5 OZ/YD2

• Cut-able width: 51 inches

• Colour: Black.

The procedure

Fabric of composition 98% Cotton 2% Spandex Solid Dyed Twill of construction 10 × (10+70D)/78 × 50 of weave 3/1 LHT of width 51 inch is taken for heat setting and applied different temperature for controlling stretch and growth in a stenter machine. The standard for stretch and growth is given in the below chart according to buyer. Temperature was also different like 160°C, 180°C and 200°C during trial. After heat setting is done, samples of “25cm × 5cm” are cut and then hang it for measuring stretch and growth in testing lab as per ASTM method.

Buyer’s standard for measuring stretch and growth of woven non-denim bottom fabric

Every buyer has a standard for measuring the stretch and growth. This chart describes what the maximum growth can be in contrast with the stretch of a fabric.

Chart explanation

It is understood from this chart that, there is a range for growth rate for a certain stretch percentage. This stretch and growth rate is


Page 3 of 9


nearly same for most of the buyers in case of cotton spandex woven non-denim bottom fabric. If the stretch% is from 01% to 10% the maximum growth rate is 2%, that means, growth rate cannot be more than 2% when stretch is from 01% to 10%. If the stretch% is from 11% to 20% the maximum growth rate is 4%, that means, growth rate cannot be more than 4% when stretch is from 11% to 20%. Like this, if the stretch% is from 21% to 30% the maximum growth rate is 6%, that means, growth rate cannot be more than 6% when stretch is from 21% to 30%. Moreover, if the stretch% is from 31% to 40% the maximum growth rate is 8%, that means, growth rate cannot be more than 8% when stretch is from 31% to 40%. It is to be noted that, if stretch and growth are passed as per buyer’s standard, it will also give a good result for recovery% (Table 1).

We can find out the stretch and growth by below formula:

Stretch%={(Loaded Length–Initial Length)/Initial Length} × 100

Growth%={(Length after relaxation–Initial Length)/Initial Length} × 100

Recovery%={(Stretched Length–Length after Relaxing)/(Stretched Length–Original Length)} × 100.

By applying this formula, we have measured stretch and growth and have mentioned in the chart.

Chart explanation

It is seen from the chart that, when we tested for stretch and growth of a non-heat set cotton spandex woven don-denim fabric, the initial length of the sample was 25 cm. We used a load of 3 pound for hanging the sample. After it was hung for 30 seconds, the sample was increased up-to 30.3 cm due to weight. We hang it for 30 min and then we relaxed the sample for one hour. After it was relaxed for one hour, it increased a little bit due to hanging, from its initial length and the new length after relaxation was 26.75 cm. As per formula [Stretch%={(Loaded Length–Initial Length)/Initial Length} ×100], the stretch becomes, [{(30.3 cm–25 cm)/25 cm} × 100] or 21.20%. If we calculate the growth as per formula [Growth%={(Length after relaxation–Initial Length)/Initial Length} × 100], the growth becomes [{(26.75 cm–25 cm)/25 cm} × 100] or 7%. Therefore, by formula [Recovery%={(Stretched Length–Length After Relaxing)/(Stretched Length–Original Length)} × 100], the

recovery is [{(30.3 cm - 26.75 cm)/(30.3 cm–25 cm)} × 100] or 66.98%. As per buyer’s standard, if the stretch is from 21% to 30%, the growth should be maximum 6%, but here growth is more than standard that is 7% so it is failing (Table 2).

When we heat set the fabric at 160°C temperature with speed of 20 MPM having width of 51.25 inches (by stretching 0.25 inches practically), then we found stretch 19%, growth 6% and recovery was 68.42%. As per buyer’s standard, if the stretch is from 11% to 20%, the growth should be maximum 4%, but here growth is more than the standard that is 6% so it is failing.

When we heat set the fabric at 180°C temperature with speed of 20 MPM having width of 51.25 inches (by stretching 0.25 inches practically), then we found stretch 12.8%, growth 2% and recovery was 84.37% which was excellent. As per buyer’s standard, if the stretch is from 11% to 20%, the growth should be maximum 4%, and here growth is within the range that is 2% so it is passing all the parameters of buyers.

When we heat set the fabric at 200°C temperature with speed of 20 MPM having width of 51.25 inches (by stretching 0.25 inches practically), then we found stretch 4%, growth 4% and recovery was 0% which was worst. As per buyer’s standard, if the stretch is from 01% to 09%, the growth should be maximum 2%, but here growth is more than the standard that is 4% so it is failing.

Third party lab testing: After testing internally in Opex and Sinha Textile Group, for proofing the internal test, the fabric (which passed all the parameter for a specific heat set temperature) was sent to a 3rd party lab testing organisation in Bureau Veritas BD PVT LTD and measured stretch and growth there and collected the data. The report number of BV BD is: BVBD17028627. This chart shows the test report.

Chart explanation

We sent the fabric to Bureau Veritas BD PVT LTD, which was heat set at 180°C temperature with a speed of 20 MPM having width of 51.25 inches (by stretching 0.25 inches practically). When we tested for stretch and growth of the fabric, the initial length of the sample was 25 cm. We used a load of 3 pound for hanging the sample. After it was hung for 30 seconds, the sample was increased up-to 28.20 cm due to weight. We hang it for 30 minutes and then we relaxed the sample for one hour. After it was relaxed for one hour, it increased a little bit due

Buyer Stretch Growth Stretch Growth Stretch Growth Stretch GrowthLevis 01%-10% Max 2% 11%-20% Max 4% 21%-30% Max 6% 31%-40% Max 8%H&M 01%-10% Max 2% 11%-20% Max 4% 21%-30% Max 6% 31%-40% Max 8%VFA 01%-10% Max 2% 11%-20% Max 4% 21%-30% Max 6% 31%-40% Max 8%

Sears 01%-10% Max 2% 11%-20% Max 4% 21%-30% Max 6% 31%-40% Max 8%JC Penny 01%-10% Max 2% 11%-20% Max 4% 21%-30% Max 6% 31%-40% Max 8%

Table 1: Buyer requirement for stretch and growth.

Sample Size: “25 cm × 5 cm” Initial Length Length with Load

Length After Relaxation

Stretch (%) Growth (%) Recovery (%) Result

Without heat set 25 cm 30.3 cm 26.75 cm 21.20% 7% 66.98% FailHeat Set 160°C, 20 MPM, 51.25" 25 cm 29.75 cm 26.5 cm 19% 6% 68.42% FailHeat Set 180°C, 20 MPM, 51.25" 25 cm 28.20 cm 25.5 cm 12.8% 2% 84.37% PassHeat Set 200°C, 20 MPM, 51.25" 25 cm 26 cm 26 cm 4% 4% 0% Fail

Table 2: Stretch and growth test is done in opex and sinha textile group, Report number: STG 08242017-0012.




Heat Set 180°C, 20MPM, 51.25" 25 cm 28.20 cm 25.50 cm 12.8% 2% 84.37% Pass

Table 3: Stretch and growth test in bureau veritas BD PVT LTD, Report number: BVBD17028627.


Page 4 of 9


to hanging, from its initial length and the new length after relaxation was 25.50 cm. As per formula [Stretch%={(Loaded Length–Initial Length)/Initial Length} × 100], the stretch becomes, [{(28.20 cm–25 cm)/25 cm} × 100] or 12.8%. If we calculate the growth as per formula [Growth%={(Length after relaxation–Initial Length)/Initial Length} × 100], the growth becomes [{(25.50 cm –25 cm)/25cm} × 100] or 2%. Therefore, by formula [Recovery%={(Stretched Length–Length After Relaxing)/(Stretched Length–Original Length)} × 100], the recovery is [{(28.20 cm–25.50 cm)/(28.20 cm–25 cm)} × 100] or 84.37% which was excellent. As per buyer’s standard, if the stretch is from 11% to 20%, the growth should be maximum 4%, and here the growth is within the range that is 2%, so it is passing all the parameters of buyer’s (Table 3).

Result and discussion

Here it is proved that, lycra without proper heat set is very difficult to control the stretch and growth. We gave three trial in stenter machine with temperature of 160°C, 180°C and 200°C. Whenever, we heated the lycra fabric with 180°C, then all the parameters like stretch and growth were passed. For proofing our test result, we have done this test in a 3rd party lab named “Bureau Varitas testing Bangladesh PVT LTD”, Report number: BVBD17028627, where the parameters like stretch and growth were also passed. Therefore, we can say that, if we heat set a non-denim woven bottom weight fabric of composition 98% Cotton 2% Spandex Solid Dyed 3/1 Twill weave fabric of construction 10 × (10+70D)/78 × 50 at width 51.25 inches (by stretching 0.25 inches) in stenter machine with 180°C temperature at 20 RPM then it will pass all the parameters like stretch and growth.



• Construction: 20 × (12+70D)/136 × 60

• Weave: 3/1 LHT



• Colour: Dark Green.

Procedure

Construction of 20 × (12+70D)/136 × 60, 3/1 LHT, CW: 53” fabric is taken for heat setting and applied different temperature for controlling stretch and growth in a stenter machine. The standard for stretch and growth is given in the above Table 1, according to buyer. Temperature was also different like 160°C, 170°C and 180°C during trial. After heat setting is done, samples of “25 cm × 5 cm” are cut and then hang it for measuring stretch and growth in testing lab as per ASTM method.


Stretch%={(Loaded Length–Initial Length)/Initial Length} × 100;

Growth%={(Length after relaxation–Initial Length)/Initial Length} × 100;

Recovery%={(Stretched Length–Length After Relaxing)/(Stretched Length–Original Length)} × 100.

By applying this formula, we have measured stretch and growth and have mentioned in the below chart.

Chart explanation

It is seen from the chart that, when we tested for stretch and growth of a non-heat set cotton spandex woven don-denim fabric, the initial length of the sample was 25 cm. We used a load of 3 pound for hanging the sample. After it was hung for 30 seconds, the sample was increased up-to 32 cm due to weight. We hang it for 30 minutes and then we relaxed the sample for one hour. After it was relaxed for one hour, it increased a little bit due to hanging, from its initial length and the new length after relaxation was 27 cm. As per formula [Stretch%={(Loaded Length–Initial Length)/Initial Length} × 100], the stretch becomes, [{(32 cm–25 cm)/25 cm} × 100] or 28%. If we calculate the growth as per formula [Growth%={(Length after relaxation–Initial Length)/Initial Length} × 100], the growth becomes [{(27 cm–25 cm)/25} × 100] or 8%. Therefore, by formula [Recovery%={(Stretched Length–Length After Relaxing)/(Stretched Length–Original Length)} × 100], the recovery is [{(32 cm–27 cm)/(32 cm–25 cm)} × 100] or 71.42%. As per buyer’s standard, if the stretch is from 21% to 30%, the growth should be maximum 6%, but here growth is more than the standard that is 8% so it is failing (Table 4).

When we heat set the fabric at 160°C temperature with speed of 20 MPM having width of 53.25 inches (by stretching 0.25 inches practically), then we found stretch 21%, growth 6.4% and recovery was 69.52%. As per buyer’s standard, if the stretch is from 21% to 30%, the growth should be maximum 6%, but here the growth is more than the standard that is 6.4% so it is failing all the parameters of buyers.

When we heat set the fabric at 170°C temperature with speed of 20 MPM having width of 53.25 inches (by stretching 0.25 inches practically), then we found stretch 19.20%, growth 4% and recovery was 79.16% which was excellent. As per buyer’s standard, if the stretch is from 11% to 20%, the growth should be maximum 4%, and here growth is within the range that is 4% so it is passing all the parameters of buyers.

When we heat set the fabric at 180°C temperature with speed of 20 MPM having width of 53.25 inches (by stretching 0.25 inches practically), then we found stretch 10%, growth 5% and recovery was 50%. As per buyer’s standard, if the stretch is from 01% to 10%, the growth should be maximum 2%, but here the growth is more than the standard that is 5% so it is failing.

Third party lab testing: After testing internally in Opex and Sinha Textile Group, for proofing the internal test, the fabric (which passed all the parameter for a specific heat set temperature) was sent to a 3rd party lab testing organisation by name Bureau Veritas BD PVT LTD and measured stretch and growth there and collected the data. The report number of BV BD is: BVBD17022017. This chart shows the test report.




Without heat set 25 cm 32 cm 27 cm 28% 8% 71.42% FailHeat Set 160°C, 20 MPM, 53.25" 25 cm 30.25 cm 26.6 cm 21% 6.4% 69.52% FailHeat Set 170°C, 20 MPM, 53.25" 25 cm 29.80 cm 26 cm 19.2% 4% 79.16% PassHeat Set 180°C, 20 MPM, 53.25" 25 cm 27.50 cm 26.25 cm 10% 5% 50% Fail

Table 4: Stretch and growth test is done in sinha textile group, Report Number: STG 08242017-0013.


Page 5 of 9


• Colour: Dark grey.

The procedure

Construction of 32 × (32+70D)/190 × 80 of weave 3/1 LHT of width 52.25-inch fabric is taken for heat setting and applied different temperature for controlling stretch and growth in a stenter machine. The standard for stretch and growth is given in the above chart (Table 3) according to buyer. Temperature was also different like 160°C, 170°C and 180°C during trial. After heat setting is done, samples of size “25 cm × 5 cm” were cut and then hang it for measuring stretch and growth in testing lab as per ASTM method.


Stretch%={(Loaded Length–Initial Length)/Initial Length} × 100

Growth%={(Length after relaxation–Initial Length)/Initial Length} × 100

Recovery%={(Stretched Length–Length After Relaxing)/(Stretched Length–Original Length)} × 100.

By applying this formula, we have measured stretch and growth and have mentioned in the below chart.

Chart explanation

It is seen from the chart that, when we tested for stretch and growth of a non-heat set cotton spandex woven don-denim fabric, the initial length of the sample was 25 cm. We used a load of 3 pound for hanging the sample. After it was hung for 30 seconds, the sample was increased up-to 32.25 cm due to weight. We hang it for 30 minutes and then we relaxed the sample for one hour. After it was relaxed for one hour, it increased a little bit due to hanging, from its initial length and the new length after relaxation was 27 cm. As per formula [Stretch%={(Loaded Length–Initial Length)/Initial Length} × 100], the stretch becomes, [{(32.25 cm–25 cm)/25 cm} ×100] or 29%. If we calculate the growth as per formula [Growth%={(Length after relaxation–Initial Length)/Initial Length} × 100], the growth becomes [{(27 cm–25 cm)/25} × 100] or 8%. Therefore, by formula [Recovery%={(Stretched Length–Length After Relaxing)/(Stretched Length–Original Length)} × 100], the recovery is [{(32.25 cm–27 cm)/(32.25 cm–25 cm)} × 100] or 72.41%. As per buyer’s standard, if the stretch is from 21% to 30%, the growth should be maximum 6%, but here growth is more than the standard that is 8% so it is failing (Table 5).

When we heat set the fabric at 160°C temperature with speed of 20 MPM having width of 52.25 inches (by stretching 0.25 inches practically), then we found stretch 21.4%, growth 6.4% and recovery was 70.09%. As per buyer’s standard, if the stretch is from 21% to 30%, the growth should be maximum 6%, but here the growth is more than the standard that is 6.4% so it is failing all the parameters of buyers (Table 6).

Chart explanation

We sent the fabric to Bureau Veritas BD PVT LTD, which was heat set at 170°C temperature with a speed of 20 MPM having width of 53.25 inches (by stretching 0.25 inches practically). When we tested for stretch and growth of the fabric, the initial length of the sample was 25 cm. We used a load of 3 pound for hanging the sample. After it was hung for 30 seconds, the sample was increased up-to 29.80 cm due to weight. We hang it for 30 minutes and then we relaxed the sample for one hour. After it was relaxed for one hour, it increased a little bit due to hanging, from its initial length and the new length after relaxation was 26cm. As per formula [Stretch%={(Loaded Length–Initial Length)/Initial Length} × 100], the stretch becomes, [{(29.80 cm–25 cm)/25 cm} × 100] or 19.20%. If we calculate the growth as per formula [Growth%={(Length after relaxation–Initial Length)/Initial Length} × 100], the growth becomes [{(26 cm–25 cm)/25 cm} × 100] or 4%. Therefore, by formula [Recovery%={(Stretched Length–Length After Relaxing)/(Stretched Length–Original Length)} × 100], the recovery is [{(29.80 cm–26 cm)/(29.80 cm–25 cm)} × 100] or 79.16% which was excellent. As per buyer’s standard, if the stretch is from 11% to 20%, the growth should be maximum 4%, and here the growth is within the range that is 4%, so it is passing all the parameters of buyer’s (Table 3).


Here it is proved that, lycra without proper heat set is very difficult to control the stretch and growth. We gave three trial in stenter machine with temperature of 160°C, 170°C and 180°C. Whenever, we heated the lycra fabric with 170°C, then all the parameters like stretch and growth were passed. For proofing our test result, we have done this test in a 3rd party lab named “Bureau Varitas testing Bangladesh PVT LTD”, Report number: BVBD17022017, where the parameters like stretch and growth were also passed. Therefore, we can say that, if we heat set a non-denim cotton spandex woven bottom weight fabric of composition 98% Cotton 2% Spandex Solid Dyed 3/1 twill weave fabric of construction 20 × (12+70D)/136 × 60 at width 53.25 inches (by stretching 0.25 inches) in stenter machine with 170°C temperature at 20 RPM then it will pass all the parameters like stretch and growth.



• Construction: 32 × (32+70D)/190 × 80

• Weave: 3/1 LHT






Without heat set 25 cm 32.25 cm 27 cm 29% 8% 72.41% FailHeat Set 160°C, 20 MPM, 52.25" 25 cm 30.35 cm 26.6 cm 21.4% 6.4% 70.09% FailHeat Set 170°C, 20 MPM, 52.25" 25 cm 28.45 cm 25.33 cm 13.8% 1.32% 90.43% PassHeat Set 180°C, 20 MPM, 52.25" 25 cm 27.75 cm 26.25 cm 11% 5% 54.54% Fail

Table 6: Stretch and growth test is done in sinha textile group, Report Number: STG 08242017-0014.




Heat Set 170°C, 20 MPM, 53.25" 25 cm 29.80 cm 26 cm 19.2% 4% 79.16% Pass



Page 6 of 9


When we heat set the fabric at 170°C temperature with speed of 20 MPM having width of 52.25 inches (by stretching 0.25 inches practically), then we found stretch 13.8%, growth 1.32% and recovery was 90.43% which was excellent. As per buyer’s standard, if the stretch is from 11% to 20%, the growth should be maximum 4%, and here growth is within the range that is 1.32% so it is passing all the parameters of buyers.

When we heat set the fabric at 180°C temperature with speed of 20 MPM having width of 52.25 inches (by stretching 0.25 inches practically), then we found stretch 11%, growth 5% and recovery was 54.54%. As per buyer’s standard, if the stretch is from 11% to 20%, the growth should be maximum 4%, but here the growth is more than the standard that is 5% so it is failing (Figures 1-5).

Third party lab testing: After testing internally in Opex and Sinha Textile Group, for proofing the internal test report, the fabric (which passed all the parameter for a specific heat set temperature) was sent to a 3rd party lab testing organisation by name Bureau Veritas Bangladesh PVT LTD and measured stretch and growth there and collected the data. The test report number of Bureau Veritas BD is: BVBD16064103. This chart shows the test report (Table 7).

Chart explanation

We sent the fabric to Bureau Veritas BD PVT LTD, which was heat set at 170°C temperature with a speed of 20 MPM having width of 52.25 inches (by stretching 0.25 inches practically). When we tested for stretch and growth of the fabric, the initial length of the sample was 25 cm. We used a load of 3 pound for hanging the sample. After it was hung for 30 seconds, the sample was increased up-to 28.45cm due to weight. We hang it for 30 minutes and then we relaxed the sample for one hour. After it was relaxed for one hour, it increased a little bit due to hanging, from its initial length and the new length after relaxation was 25.33 cm. As per formula [Stretch%={(Loaded Length–Initial Length)/Initial Length} × 100], the stretch becomes, [{(28.45 cm–25 cm)/25 cm} × 100] or 13.80%. If we calculate the growth as per formula [Growth%={(Length after relaxation–Initial Length)/Initial Length} × 100], the growth becomes [{(25.33 cm–25 cm)/25 cm} × 100] or 1.32%. Therefore, by formula [Recovery%={(Stretched Length–Length After Relaxing)/(Stretched Length–Original Length)} × 100], the recovery is [{(28.45 cm–25.33 cm)/(28.45 cm–25 cm)} × 100] or 90.43% which was excellent. As per buyer’s standard, if the stretch is from 11% to 20%, the growth should be maximum 4%, and here the growth is within the range that is 1.32%, so it is passing all the parameters of buyer’s (Table 3).


Here it is proved that, cotton spandex bottom weight woven fabric without proper heat set is very difficult to control the stretch and growth. We gave three trial in stenter machine with temperature of 160°C, 170°C and 180°C. Whenever, we heated the lycra fabric with 170°C, then all the parameters like stretch and growth were passed. For proofing our test result, we have done this test in a 3rd party lab named “Bureau Veritas testing Bangladesh PVT LTD”, Report number: BVBD16064103, where the parameters like stretch and growth were also passed. Therefore, we can say that, if we heat set a non-denim cotton spandex woven bottom weight fabric of composition 98% Cotton 2%

Figure 1: Stenter machine.

25 cm

5 cm

Sample fabric in weft direction

Figure 5: Sample cutting standard size for measuring stretch and growth.

Figure 2: Heat setting process is going on in a stenter machine (Mercerized fabric).

25 cm

5 cm



Figure 4: Stretch measurement process.


Page 7 of 9


Spandex Solid Dyed 3/1 twill weave fabric of construction 20 × (12+70 D)/136 × 60 at width 52.25 inches (by stretching 0.25 inches) in stenter machine with 170°C temperature at 20 RPM then it will pass all the parameters like stretch and growth (Figures 6-10).

Changes Due to Heat SetWhat actually happened after heating, the spandex inside the

cotton fibre is becoming harder and it is gripping the cotton fibre. As a result, the lycra cannot be stretched as much as it could before. Prior to heat set, the yarn was thicker but after the lycra is heated, it is becoming thinner and harder. The lycra filament is attaching with the cotton fibre. And also it is gripping the cotton fibre. The structural pattern of various materials will be rearranged due to heat-set. Internal tension in yarn that was generated in spinning or in twisting will be removed and it will be stabilized, thus it will control stretch. Thermal shrinkage is also happening due to heat set that is reducing creep, crimp and growth in normal condition.

Heat setting eliminates the tendency of undesirable torqueing. Heat setting creates the structural change of fibre orientation. Heat setting also decreases the strength and elongation. It can also be said that heat setting normally causes restructuring or rearrangement of fibres and yarns (Figures 11-15).

Time and Temperature CurveWhenever we are heating the cotton spandex yarn, the strength

of that yarn at first increasing. After heating for a certain time, then the strength will not be increased. Then the strength will start falling down. This is shown in the figure with a curve. Here the straight up line designates strength and the horizontal or parallel line designates temperature. The graph also expresses that, strength increases for a certain time after that it start falling down. This can be expressed with a quadratic equation of curve that is, y=ax2+bx+c.

Mathematical EquationTemperature verses Strength curve can be expressed in standard

form, a quadratic function is written as, y=ax2+bx+c.

We know the quadratic equations with the three coefficients a,b c.

In the simplest case, Y=constant, (y=c)

If a, b, c all are zero (0), then the equation is, y=0x2+0x+0, y=0

If a=1, then y=1x2+0x+0, y=x2.




Heat Set 170°C, 20 MPM, 52.25" 25 cm 28.45 cm 25.33 cm 13.80% 1.32% 90.43% Pass




25 cm

5 cm



Figure 9: Due to heat set fibres in the yarns becoming stable.

Strength

Temperature

Figure 10: Temperature verses strength curve.


Page 8 of 9


machine provides hot air blow with heavy temperature that removes or burnt the unwanted fibres of yarn, due to that, the yarns after heat set is looking much clearer (Figures 16 and 17).

Cross section

We placed the fabric in an electron microscope (Projectina Microscope DMM 2000) and find the assessment in before and after heat set. Due to heating, the molecular structure both in amorphous and crystalline phase is changing. Due to heat-setting, the distance in between crystalline centres and the number of bonds between molecules in fibres is decreased. It is said that, the decreased tensile properties were correlated with more un-oriented chains in amorphous

If b=2, then y=0x2+2x+0, y=2x

If c=3, then, y=0x2+0x+3, y=3.

Microscopic ViewLength wise view

It is clearly noticed in the figure that, before the spandex yarn was heat set, the protruding fibres were much more visible in the yarn surface. But after the heat set is done, the protruding fibres goes up. What actually happened here, during heat setting, the protruding fibres were burnt by stenter machine through its heated chamber. Heat set

Figure 11: Microscopic view of yarn (Before heat set), 20 × (12+70D)/136 × 60.

Figure 12: Microscopic view of yarn (After heat set), 20 × (12+70D)/136 × 60.

Figure 13: Microscopic view of yarn (before heat set), 32 × (32+70D)/190 × 80.

Figure 14: Microscopic view of yarn (after heat set), 32 × (32+70D)/190 × 80.

Figure 15: Microscopic view of yarn (before heat set), 10 × 10+70D/78 ×50.

Figure 16: Microscopic view of yarn (after heat set), 10 × 10+70D/78 × 50.


Page 9 of 9


and crystalline region, and more irregular yarn structure. This process of heating, changes the orientation of fibre. Structural change also leads to the change in strength, elongation subsequently it is affecting the stretch and growth.

ConclusionFrom this total project, we got to know that, heat setting stabilizes

the cotton elastic yarn that controls the elasticity, stretch, growth and also controls the shrinkage properties of woven fabric. Heat setting of

cotton spandex yarns, closely attached the cotton fibre with elastane which gripped the cotton fibre. It is known to us that, cotton spandex woven fabrics have a tendency of curling during dyeing and colour fixation process but if the cotton spandex is heated properly, this curling problem can also be reduced while controlling growth. Cotton spandex yarns have a tendency of torqueing due to its rotating force, but due to hearting properly through the application of hot air blow from stenter this tendency reduced while controlling growth. It is also noticed that, the total core structure of yarn was rearranged due to heating and subsequently it reduced creep, crimp and growth in normal condition of fabric. Basically, heat setting is deeply connecting the cotton fibres with spandex, for that reason, elasticity, stretch ability and growth are coming under control. In final closure we can say that, this project work can help the textile cotton spandex industry to control stretch, growth, shrinkage or dimensional stability, elastic recovery and extension, resiliency, elasticity, shape retention, crease resistance properties, enhancing strength, pilling performances and also crease resistant properties.

References

1. DJ (2007) Parametric Equation of a Circle - The Math Open Reference Project.

2. Kish MH, Shoushtari SA, Kazem S (2000) Effects of cold-drawing and heat-setting on the structure and properties of medium speed spin polypropylene filaments. Iranian Polymer Journal 9: 239-248.

3. Miller R (2002) Manipulating fiber structure to stabilize geometry in fibers and yarns. Textile Research Journal 72: 601-612.

4. Kalebek NA, Babaarslan O (2013) Effect of Heat Setting Process for Polymers. Polymer science: research advances, practical applications and educational aspects: 199-207.

5. Microscopy P (2011) Textile Microscopy. Switzerland: Projectina Authority.

6. Sarkeshick STH (2009) An Investigation on the effects of heat-setting process on the properties of polypropylene bulked continous filament yarns. Journal Textile Institutuin: 128-134.

7. Tex trade (2013) Stenter Machine 1024×400. Retrieved from Textile Machines Parts & Accessories: trade, Alibaba.com global.

Figure 17: Before heat set (yarn cross section).

Figure 18: After heat set (yarn cross section).


http://www.mathopenref.com/coordparamcircle.html

http://studylib.net/doc/8795017/effects-of-cold-drawing-and-heat-setting-on-the-structure...



https://doi.org/10.1177/004051750207200707

https://doi.org/10.1177/004051750207200707

http://www.formatex.info/polymerscience1/book/199-207.pdf



http://dx.doi.org/10.1080/00405000701692429

http://dx.doi.org/10.1080/00405000701692429

http://dx.doi.org/10.1080/00405000701692429

Documents

x t i l e S cienc T e E Journal of Textile Science ... · PDF fileWhat actually happened due to heat setting the cotton spandex woven fabric and ... inside it for heat setting [6,7]