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Elastic knitted fabrics for tight fit sportswear

Spandex core cotton spun knitted fabrics are preferable for active sportswear like hockey,rugby and tennis, and Spandex back plaited cotton knitted fabrics are preferable for stretchsportswear for javelin, shot-put and athletic sprint sports activities, moot M Senthilkumar andDr N Anbumani.

Stretch garment are used in athletic sports activities such as cycling, swimsuits and sprintgames. It improves the sportsman or athletics' performance by achieving body demand in

movements by reducing fabric resistance to the body. A simple body movement expands theskin about 50%. Strenuous movements involved in active sports require even more garmentstretch and recovery. The drastic difference in between skin and fabric movement is due torestriction of movement to the wearer.

Stretch fibre, yarn or fabric provides necessary elasticity for a garment to respond to everymovement of the body and return to its original size and shape. The degree and direction ofelasticity determines the end use of stretch garment. The most important property requirementfor stretch garment is in the order of body comfort fit, breathability and durability. Thecommercial stretch fabric production methods are spandex core cotton spun yarn fabric andspandex plaited cotton fabric. So far, no comparative analysis has been made between thesetwo commercial methods, in order to select the right fabric for specific sports end-useapplication.

ObjectiveThe objective of the work is to compare the elastic and comfort characteristics of elastic knittedfabrics produced from two different commercial production methods. They are a) Spandex corecotton spun yarn converted knitted fabric b) Spandex back plaited cotton knitted fabric. In orderto compare these two methods, the amount of spandex feed kept constant at both the cases.

Experimental methods

Spandex core cotton spun yarn fabric

A core spun yarn is a structure composed of a separable core surrounded by fibre and suitablefor use as a yarn. The manufacturing process consists of feeding filament to spinning unit where

it covered by staple fibres (Figure 1).

Normal core spun yarn manufacturing system is used to produce a stretch yarn by feeding spandex separately by feed rollerarrangement. It is to be fed in the main drafting zone. Input spandex yarn tension and the draft applied to the core fibres

decide the quality of the yarn. The spandex feed is kept at 7 percentage.

Spandex back plaited cotton fabric

It is a new concept, stretch fabric production only at the fabric formation not in the yarn

stage. Bare spandex is directly fed along with normal yarn during knitting. Normal yarnand spandex is passed through the same feeder to form a loop and to produce a fabric.Normal knitting machine has special spandex feed attachment at the top of the machinefor this plaited fabric production (Figure 2).

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The selected materials were fabricated on 21-inch diameter, 24-gauge circular knittingmachine at the speed of 25 rpm. The amount of spandex feed was kept at 7%. Bothcommercial knitted fabrics were processed to heat setting at 200C temperature for 38

seconds at the speed of 30 rpm. These fabrics were dyed with Red CA dyes with 65C temperature and 7.5 PH. They aretreated with compacting at the temperature of 94C. the finished stretch fabrics were tested for its comfort properties.

Testing methodsStretch fabrics produced from two commercial production methods were tested for their stretch comfort - elastic properties(ASTM 2594), sweat management properties such as wetting (AATCC 79: 2000), wicking (BS 3424), water vapourtransmission (ASTM E 96 - Cup Method) and air permeability (IS 110 56 - 1984).

The comparative analysis was made between two kinds of stretch fabrics and the results were discussed.

Elastic stretch and recovery

Fabric stretch and growth properties were determined as per ASTM 2594 procedure. A typical way of fabric stretchanalysis was made to hank a fabric with the weight of five pounds for one minute. Then, the weight is removed to calculatefabric stretch. Further, the stretched fabric was left freely for five minutes. Now the fabric gets compresses again. It is tocalculate fabric growth.

Fabric stretch and growth can be calculated by the following formulae.

Fabric stretch percentage = change in length/original length x 100Fabric growth percentage = 100 recovery percentageWhere, Recovery percentage = change in length [removal of 5 pound load]/originallength x 100

Table 1: Elastic properties of stretch fabric

SNo Specification

Spandex core cotton spunknitted fabric

Spandex back plaited cottonknitted fabric

1 Elastic stretch-wale (Max)% 95 108

2 Elastic stretch-course(Max) % 120 130

3 Elastic recovery-wale(Max) % 90 95.5

4 Elastic recovery-course(Max)% 87.78 93.34

Spandex back plaited cotton knitted fabrics (SBPC) have higher in elastic stretch and elastic recovery at both the sides(wale wise and course wise direction) than that of spandex core cotton spun knitted fabric (SCCS) due to higher stitchdensity of SBPC (SBPC: 4608 & SCCS: 3840 Loops per Square inch) knitted fabric. The higher stitch density is the evidencethat the spandex in SBPC knitted fabric has higher residual and recovery energy than SCCS knitted fabric. That is thereason for higher stretch and recovery of the SBPC knitted fabric.

The elastic recovery of both knitted fabrics were analysed at four level of elastic extension such as 20%, 30%, 40% and50%. When the fabric elastic extension is increases from 20% to 50%, fabric elastic recovery is decreases for both thefabrics at both the directions.

SBPC knitted fabric has higher elastic recovery than that of SCCS knitted fabric at both wale wise and course wise direction(Figure 3). SCCS fabric elastic recovery - course wise direction is higher than that of wale wise direction of the fabric. But,SBPC fabric elastic recovery - wale wise direction is higher than that of course wise direction of the fabric. Fabric growthpercentage is calculated by 100 elastic recovery in percentage (Figure 4).

Wetting time

Fabric water absorbency is to measure the ability of the fabric to absorb a drop of water by spreading action. A fabricsample of size 10 x 10 cm was taken. A drop of water was allowed to fall on the flat fabric surface. Area has been keptconstant for finding out water spreading in seconds. The height of water drop is controlled by a syringe, which contains one

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ml of water.

Table 2: Wetting test

S No Specifications SCCS SBPC1 Wetting time (seconds) face 39.1 1502 Wetting time (seconds) back 26.28 175

SCCS knitted fabric absorbs a drop of water quicker than that of SBPC fabric due to cotton wrapped surface in the yarnperipheral. Further, SBPC fabric has lower inter yarn space due to higher stitch density.

Longitudinal wicking test

A 20 x 2 cm strip of test fabric was suspended vertically with its lower end (2 cm) immersed in a reservoir of distilled waterfor tracking the movement of water. In this method, the wick-up action of water spreading by capillary action was observedafter ten minute at which the water moved upward on a strip of fabric.

Rate of longitudinal wicking has been carried out for the two stretch fabrics at the interval of 1, 2, 3, 5 and 10 minute. SCCSfabric shows higher wicking rate than that of SBPC fabric in both the directions. It is may be due to cotton covered surfacein the yarn peripheral. Similarly, the spandex in the SBPC fabric has lower the capillary pressure. Hence it has lowerwicking rate.

Moisture vapour transmission

Moisture vapour transmission rate (MVT) in the speed or rate at which moisture vapour moves through a fabric. The ASTM E96 moisture vapour test (open cup test) is used for measuring the moisture vapour transmission rate. The rate of watervapour that passes through the fabric was determined by two different methods.

a) Reduction in the height of water in the cup

Water was poured into cups up to 6 cm from base level. The cups were marked for every half centimetre. The fabricsamples are placed tightly on top of the cups where the water, the air above the water and the room environment are atthe same temperature and pressure. After 48 hrs the level of water decreased in the cups and the reduction in height ofwater was noted down. The moisture vapour transfer rate is the difference between the initial height of water and the actualheight of water in the cups.

b) Reduction in the weight of water in the cup

After measuring the height of water in the cups after 48 hours, the fabrics were taken out from the top of the cups and thecups with water were weighed in an electronic balance and the reduced weight was noted down. The moisture vapourtransfer rate is the difference between the initial weight of water and the actual weight of water in the cups after 48 hours.

Moisture vapour transmission of SCCS and SBPC knitted fabrics are nearly equal value in both the weight and heightmethod. So, MVT method is the independent property, which does not serve the purpose. Further, it is essential to measureMVT with respect to time.

Air permeability test

Fabric air permeability is the rate of air flow through the material under a differential pressure between the two faces of afabric. It is expressed as the quantity of air, in cubic centimetre passing per second through a square centimetre of fabric.

SCCS fabric has higher air permeability value than that of SBPC fabric due to higher stitch length (SBPC: 2.54 mm & SCCS:2.63 mm) and lower fabric stitch density. Fabric air permeability is the inverse of air resistance. So, SCCS fabric has lowerair resistance.

Spandex Core Cotton Spun fabric and Spandex Back Plaited Cotton knitted fabrics were compared and analysed for theircomfort properties such as a) elastic properties b) Moisture management properties such as wetting, wicking, water vapourtransmission and air permeability. It is very clear that the SCCS knitted fabric has quicker wetting, higher wicking rate andhigher air permeability value than that of SBPC knitted fabric in all the cases.

At the same time, SBPC knitted fabric has higher elastic stretch and higher recovery than that of SCCS fabric at all thecases. It is recommended that Spandex core cotton spun knitted fabrics are preferable for active sportswear like hockey,rugby and tennis. Similarly, Spandex back plaited cotton knitted fabrics are preferable for stretch sportswear for Javelin,shot-put and athletic sprint sports activities, in order to enhance the stamina, speed and power of the sports person.

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The authors thank the management of PSG College of Technology and Polytechnic College, Coimbatore for providingopportunity to publish the research work. Further, they also thank the students of PSG polytechnic College -- Ramkumar,Santhosh, Udayakumar, Raja Nagendran and Ms Safiya who helped carry out the work.

References

1. Hseyin Gazi Ortlek; Sukriye Ulku (2007): Effects of Spandex and Yarn Counts on the Properties of Elastic Core-spunYarns produced on Murata Vortex Spinner, Textile Research Journal; 77, (6), 432 436.

2. C W Lou (2005): Production of a Polyester Core Spun Yarn with Spandex using a Multi-section Draw Frame and RingSpinning Frame, Textile Research Journal, 75, (5), 395 401.

3. Ching-Iuan Su; Hsiao-Ying Yang (2004): Structure and Elasticity of Fine Elastomeric Yarns, Textile Research Journal, 74,(12), 1041 -1044

4. JiaHorng Lin and Ching Wen Chang (2004): Mechanical Properties of Highly Elastic Complex Yarns with Spandex Madeby a Novel Rotor Twister, Textile Research Journal, 74 (6), 480 484.

5. A Bayazit Marmarali (2003): Dimensional and Physical Properties of Cotton/Spandex Single Jersey Fabrics, Textile

Research Journal, 73, (1), 11 14.

6. A Mukhopathyay (2001): Impact of Lycra Filament on Extension and Recovery Characteristics of Cotton Knitted Fabric,Indian Journal of Fibre and Textile Research, Vol 28, 12, 423 430.

7. J J F Knapton and W Fong (1968): The Dimensional Properties of Knitted Wool Fabrics, Textile Research Journal, Part I,38, 999 1012.

8. Kentaro Kawasaki and Takayuki Ono (1966): Stretch Properties of Weft Knitted Fabrics, Journal of the Textile MachinerySociety of Japan, Vol 19, No 4, T112 117.

9. S M Ibrahim (1966): Mechanism of Stretch Development in Fabric Containing Spandex Yarn, Textile Research Journal,(8), 697 706.

10. J Voyce, P Dafniotis and S Towlson: Invista (Switzerland), Textiles in Sports Chapter 10: Elastic Textiles, 205 - 230.(Woodhead Publications).

Note: For detailed version of this article please refer the print version of The Indian Textile Journal June 2011issue.

M SenthilkumarDepartment of Textile Technology,PSG Polytechnic College,Coimbatore, Tamil Nadu 641 004.Email: cmsenthilkumar@yahoo.com.

Dr N AnbumaniDepartment of Textile Technology,PSG Polytechnic College,Coimbatore, Tamil Nadu 641 004.

published June , 2011

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