The consumption of textile fibres and fabrics in sportswear and sporting related goods has seen a significant increase in last decade or so. In an analysis made in 2002 by David Rigby Associates it was stated that the world wide consumption of textiles for the sports increased from 841,000 tons in 1995 to 1,153,000 tons in 2005. The forecast made for 2010 is 1,382,000 tons. This reflects to a large extent the significant rise in the interest of worldwide population in active indoor and outdoor leisure pursuits. The rising interest is due to a number of social factors that include increased leisure times, increased considerations of well being and good health, growth of indoor and outdoor sports facilities as well as the ever increasing pursuit of adult population of activities outside the home or workplace.

The sportswear textile industry has not only seen in market diversification for fibrous materials but has also contributed towards the elevation of textile science and technology to a level of approaching that of high tech industrial sectors. New technological developments, more fragmented niche markets and increasing customer expectations are some of the factors relentlessly driving the industrial sector. The producers of sportswear have been concentrating their efforts on improving their strategic position, productivity, added value product assortment and niche positions in order to expand their markets.

The performance requirements of many sports goods often demand widely different properties from their constituent fibres and fabrics, such as barrier to rain, snow, cold, heat and strength and at the same time these textiles must fulfill the consumer requirements of drape, comfort, fit and ease of movement. Among the contributing factors responsible for successful marketing of functional sportswear has been made in the fibre and polymer sciences and production techniques for obtaining sophisticated fibre, yarns and fabrics. The finishing and laminating industries have done pioneering work in the area of developing these technologies towards the needs of sportswear and sporting goods sectors resulting in unique products.

Comfort

For the consumer the comfort of any garment stems from a combination of its sensorial properties, its psychological properties and its thermo physiological properties. Comfort is determined by the interaction of the body with its micro climate and its clothing. Where garments are worn as layers, it is the combination of properties of the individual garments that determine the comfort of the whole clothing system.

Whilst undergoing strenuous activity a body generates additional metabolic heat. Sweat is produced as a part of the natural mechanism for the dispersion of that heat. A naked man can control his heat loss almost instantly as sweat is evapourated very quickly during the period of activity leaving no accumulated sweat when activity stops. Clothing can act as a barrier to heat and moisture loss. If over-heating is to be avoided, thermoregulation and moisture management are key functions of clothing designed for use as a sportswear that has been transferred to the mass market and may be worn on a daily basis, such as football and basketball shirts. The psychological and sensorial function are as important as the thermophysiological properties.

Psychological comfort consists of a combination of consumer fashion trends. Where garments are worn during strenuous activity, psychological comfort also occurs when the garment is extensible and does not restrict mobility. A garment with low intrinsic weight can significantly aid sporting performance for success in the market.

Sensorial comfort is focused on the tactile sensation of a garment on the human body. Garments should be soft and pliable during wear and especially when damped, should not prickle/ irritate or cling to the body. To a lesser extent, sensorial comfort can be improved by the control of odour and by the use of UV resistant materials. Waterproofing can improve sensorial comfort but may impair thermo physiological comfort.

Thermo physiological comfort entails both thermoregulation and moisture management. Garments should be designed to maintain the human body temperature and moisture output close to its normal levels under diverse conditions. The thicker the layer of air trapped inside the clothing system the greater its thermal resistance to moisture transmission. If perspiration is trapped next to the skin during exercise it can lead to an increase in body temperature, and this will cause dehydration, fatigue and decreased performance.

The insulation properties of a fabric usually decline when the fabric is wet resulting in rapid heat loss from the wearer. This wetting can be both from outside a garment and from inside a garment. During strenuous activity wet fabric can aid in the cooling of hot skin surface. However, once the activity and the excessive heat production stop, this heat loss must be restricted. A wet body cools very quickly leading to post-exercise “chill” or, in extreme cases hypothermia.

Garments that are designed for sportswear and active wear should be dynamic or responsive. Through effective thermoregulation and moisture management a clothing system can maximize heat loss when the wearer is hot, then increase thermal insulation when perspiration stops. In a sports arena dynamic or responsive garments can enhance performance, control weight build-up in clothing and reduce the potential for skin damage.

Measurement of comfort

Intrinsic thermal insulation measures the resistance of a dry or damp fabric. It is generally proportional to fabric thickness. It does not include the effect of the layer of air associated with a fabric during actual use.

Thermal insulation measures the resistance of a fabric and its associated layer of air to dry or conductive heat loss. Thermal insulation, unlike intrinsic thermal insulation, will vary with wind speed. Increasing wind speeds decrease the thermal insulation afforded by the layer of air. Thermal conductivity of fabric determines the rate of transmission of heat through a fabric. Thermal conductivity is the reciprocal of thermal insulation or resistance.

Moisture vapour permeability determines the resistance of a fabric to the transfer of insensible perspiration emanating from the body. Relative moisture vapour permeability determines the percentage of water vapour transmitted through the fabric sample compared with that through the equivalent thickness of air. An increase in fabric thickness tends to a decrease in the rate of water vapour transmission through the fabric. Low moisture vapour permeability prevents perspiration from passing through the fabric leading to a precipitation and accumulation of sweat in the clothing.

Water (sweat) absorption determines the capacity and rate of a fabric to mop up the liquid sweat generated by the body. Ideally the absorption capacity should be low at the surface of the fabric in contact with the skin to prevent wet clinging.

Wicking determines the capacity and rate of the fabric to transport absorbed sweat away from the point of absorption that is away from the skin. Rate of drying from the outer surface of a fabric must be optimal for continuous wicking and hence prevention of saturation of the fabric with sweat.

Wind proofing a garment provides a mechanism by which heat loss by convection is reduced, thereby improving the thermal insulation properties of the clothing system.

Surface coefficient of friction of a fabric contributes to the sensorial comfort of a fabric. The coefficient can increase significantly in a wet fabric leading to rubbing or chafing of the skin. Low surface coefficient of friction is essential where one layer of fabric must move freely against another layer of fabric.

Handle of a garment describes its tactile qualities and includes softness, compressibility, pliability, drape, etc. These properties, though less important in specialised sportswear than in clothing worn on a daily basis, should not impair the performance of the wearer.

Sportswear

The dramatic growth in active wear and sportswear market has significant implications for the textile industry. Spending for sportswear in the UK alone exceeded $4 billion in 2004 and is predicted to reach $5 billion in 2007. The sector ranges from specialist apparel for specific sports to sportswear worn for its fashion value. Different sports require garments to fulfill different functions. For example wind proofing and high thermal insulation are required for skinwear, whereas efficient thermoregulation and moisture management are required in sportswear.

Worldwide sales in the sportswear sector have increased by 75% between 1987 and 1988. There was an anticipated growth of 23% between 1997 and 2001. Sales within the European EU 15 markets are currently worth at least $ 16 billion with 11 billion being spent on clothing. A recent keynote report estimated that, in 2002 UK customer spent $ 4.5 billion on sportswear. The performance fibres, yarns, fabrics and finishes developed for this sector are being increasingly transferred to the mass market in the high street. The increasing cultural importance of sportswear in fashion meant that only 25% of sportswear was used for active sports or during exercise. The report forecasts a 17.6% growth in sportswear market over the next few years resulting in UK sales of $ 5 billion in 2010. Consumers demand high level of comfort, design and easy care in all types of clothing. However, in sportswear, where thermo physiological comfort can significantly enhance the performance of the wearer, the uses of innovative textile products are commonly increasing in the recent years.

Requirement of active sports wear

Functional properties

For top level competition, active sportswear requires super lightweight, low fluid resistance, super high tenacity and stretch ability. For those seeking comfort and healthy pursuits, critical features include thermal retention, UV resistance, cooling capacity, sweat absorption and fast drying, vapour permeability, water proofing to provide relaxation without fatigue.

Aesthetic properties

From the sensitivity or aesthetic point of view softness, surface texture, handle, lustre, colour variation, transparency and comfort in sports wear are important factors. In general predominant requirements from most of the active sportswear are:

PROTECTION:
From wind water and adverse weather.

INSULATION:
Protection from cold

VAPOUR PERMEABILITY:
To ensure that body vapour passes outward through all the layers of the clothing system.

STRETCH:
To provide the freedom of movement necessary in sports.

Characteristics of sportswear

In active and endurance sports, the performance of sportswear is synonymous with its comfort characteristics. In active wear of outdoor use, the clothing should be capable of protecting the wearer from external elements such as wind, sun, rain and snow. At same time it should capable of maintaining the heat balance between the excess heat produced by the wearer due to increased metabolic rate on the other hand and the capacity of clothing to dissipate the body heat and perspiration on the other.

Over the past two decades the advances were made in technologies of spinning fibres and yarns, the production techniques for functionally designed knitted and woven fabrics as well as in the highly functional coating and laminating technologies. All these resulted in some of the most interesting fabrics which possess the desired qualities of good tactile properties, thermal insulation, stretch, quick liquid absorption ability to evapourate water while staying dry to the touch and being capable of transporting perspiration from skin to outer surface and then quickly dispersing it the performance category that has seen a large number of innovations is that of moisture management, which is directly related to comfort.

These fabrics are engineered by using either micro porous or hydrophilic membranes, and the water vapour transmission through these membranes is achieved by the physical process of adsorption, diffusion and adsorption.

It is now well established that no single fibre or blends of different fibres can make ideal sportswear. The prerequirements of ideal sports wear are rapid transport of perspiration away from the body and then its rapid evapouration. This can be achieved by two or more layers of different fabrics. The layer next to the body usually acts as a rapid wicking layer and the layers above act to absorb this perspiration and evapourate the moisture rapidly. This evapouration takes the body heat away.

The functional sports wear must have the following characteristics:
 --Optimum heat and moisture regulation
 --Good air permeability
 --Wickability
 --Dimensional stability even wet
 --Durable
 --Easy care and light weight
 --Soft and pleasant touch and produces cooling effect

Physiological requirements relating to sportswear

It is not a simple task to optimise sports wear universally as regards thermophysiological and sensory comfort, as the marginal conditions differ. According to the Figure 1, the professional sportsman practically always produces a maximum physical performance whereby as a rule, the actual sports clothing is worn for a comparatively short time. The climatic conditions are fairly constant during this time.

On the other hand leisure sport is characterised by the fact that maximum physical performance is not always achieved and that active phases are interspersed with rest phases. In addition the leisure sportsman often wears his clothing for several hours or the whole day. Wide variations in the climatic conditions may therefore occur.

Clothing for leisure sport must therefore have a considerably greater control range than that for professional sport. This means that clothing which is physiologically suitable for the professional sportsman may be unsuitable for the leisure sportsman and vice versa. In particular, clothing for the leisure sportsman is therefore considerably more difficult to design as far as the physiological requirements are concerned because these are often contradictory because of the differing climatic conditions.

According to the Figure 2 when the weather is cold, the clothing must exhibit a high level of thermal insulation, but when the weather is hot the level of thermal insulation must be low. However, the thermal insulation of a textile material is determined by its construction parameters such as the type of fibre and yarn, the construction of the woven or knitted fabric and in particular the thickness of the sports wear.

To achieve variable thermal insulation, sports clothing must be constructed on the basis of “Onion-Skin” principle, ie, as a “clothing system “ with many layers and consisting of several items of clothing. The clothing can thus be adapted to the changing situation by putting on or taking off individual items of clothing which are designed exclusively as a protection against the wind or wet weather.

In addition to its structure, the moisture transfer and moisture storage capacity of a textile also depend on the characteristic properties of the fibre substrate. Natural fibres such as cotton and wool are hygroscopic and are therefore characterised by high absorption levels. Unfortunately the absorbed moisture is bound in strongly and only released slowly. This results in a low moisture transfer rate for these textiles. On the other hand synthetics such a polyester, nylon and acrylics are not hygroscopic and therefore only Absorb comparatively small amounts of moisture. However, because of a hydrophilic fibre surface, they have a high moisture transfer rate.

Concept of bi-layer fabric

The fibre which is better suited from the physiological point of view therefore depends on the situation. On the other hand there is no single fibre which combines all the different physiological properties to cover all the situations under which sports clothing is worn.The basic structure of bi-layer fabric is shown in the Figure 4.

Figure 4. Structure of bi-layer fabric

Knitted and woven fabrics can be used whre the spatially separate components forming the inner and outer layers are linked by the overlapping yarns. All the parameters of the two components can be selected freely and largely independently from one another.

One way of constructing a physiologically functional bi-layer fabric is to use on the inside, a synthetic material with good moisture transfer properties.e.g. polyester, nylon, acrylic, polypropylene in association with a outside material which is a good absorber of moisture, eg, cotton, wool, viscose rayon.

Figure 5 schematically shows the conductive inner layer transfers the liquid perspiration rapidly to the absorbent outer layer chiefly as a result of the capillary effect. This capillary effect can be optimised through a suitable matching of the fibre and yarn diameters on the inside and outside of the bi-layer textile material.

Figure 5. Structural principle of bi-layer fabric

Fibres used in sportswear

For every active sport, synthetic fibres preferred because they do not retain moisture and therefore do not get heavy upon sweating like cotton does. Synthetic sports uniforms also have better dimensional stability. Synthetic fibres offer the three major requirements in today’s high technology sports uniforms: 

--Warmth, wind resistance, moisture wicking and lightness. 
--Comfort and feel of natural fibres. 
--Style and a variety of colours. 

With the advanced technology, however, natural fibres like cotton and Tencel are making a comeback in high-performance, outdoor activities. For example, cotton can be made wind proof, breathable, and water resistant. For heavier fabrics, such as track suits and jogging suits, nylon, polyester, acrylic, and their blends with acetate, cotton and wool are used. These fabrics maybe brushed inside for warmth and are cut loosely for comfort.

Polypropylene 

Polypropylene fibres are increasingly being used in the sports wear market ashlars is still very small. The fibres have very low moisture absorbency but excellent in moisture vapour permeability and wicking capabilities. Insensible and liquid perspiration are transported away form the skill without being absorbed making it an ideal fibre for sportswear. As polypropylene does not become wet and its thermal insulation is retained during and after strenuous activity. However soil removal is difficult and fabrics made from polypropylene may shrink if washed at high temperature. These fibres are also relatively more difficult to dye and finish. 

Tencel 

Tencel is a trade name and the generic name is Lyocell. Lyocell is a natural, man-made fibre produced in an environmentally-friendly process from wood pulp that has become popular in clothing because it is absorbent and comfortable for wear, especially in conditions of high humidity.  Lyocell also drapes attractively and is flattering in dresses and shirts. 

Lyocell is stronger than cotton or regular viscose rayon and does not lose strength when wet as viscose rayon does. Lyocell stretches more than cotton, but less than viscose. It is often blended with cotton and/or polyester, mainly in woven fabrics, rather than knits. It is absorbent and comfortable for wear in conditions of high humidity because it is cellulosic which causes moisture to be wicked away from your skin. It is manufactured by a solvent spinning process, but the solvent is recycled so its manufacture is an environmentally friendly process compared to other rayons. 

Cotton 

Cotton is a hair attached to the seed of the cotton plant or the species of a plant known as gossipium. Cotton is the oldest fibre used for textile purpose. Cotton is used extensively used in apparel fabrics for men’s wear and women’s wear and house hold fabrics like bed sheets, towels, rugs and carpets. Cotton can also be used in industrial application as tyre cords, in bags, shoes and medical supplies and equipments. 

Materials and methodology 

Selection of raw material 

The following yarns are chosen to produce bi-layer knitted fabric: 
Texturised Polypropylene – 120 Denier, Blue yarn 
Cotton - 40s Combed yarn 
Tencel – 40s Spun yarn 

Knitting construction 

The prerequisites of ideal sportswear are rapid transport of perspiration away from the body and then its rapid evapouration to keep the fabric dry. This is achieved by bi- layer of fabric construction in which the inner layer is made of texturised polypropylene yarn which is hydrophobic and having good wicking rate. The outer layer is made up of nature or regenerated fibre such as cotton or tencel which has more absorption character and rapid evapouration. The fabric is constructed in an interlock knitting m/c with jacquard feature. The fabric which has to form as inner layer is fed in the dial needle and the outer layer is fed in the cylinder needle. 

Machine parameters 

1. Type                         : Interlock Jacquard knitting machine 
2. Make : Mayer & Cie – OVJA36 
3. Feeders 1& 3           : Cotton or Tencel 
4. Feeders 2 & 4          : Polypropylene 
5. Gauge                      : 20 needles/inch 
6. Diameter                  : 30 inches 
7. Total needle count    : 3744 
9. No. of feeders          : 36 
10. Knitting speed        : 15 rpm 

Concept of bi-layer fabric structure 

Needle Set Out: 

Cam Set Out:

Dial Needle: Two Tracks (Polypropylene Yarn)

              D N 1 – Dial Needle Track 1   D N 2 – Track 2 
              N– Needle     F – Feeder
              A –Needles Moving in Track 1 – 1,3,5,7,9,11,13,15,17
             B – Needles Moving in Track 2 – 2,4,6,8,10,12,14,16,18

Cylinder Needle: Three Tracks (Cotton / Tencel Yarn)

              C N 1 – Cylinder Needle Track 1
              C N 2 –Track 2              C N 3 –Track 3
              A –Needles Moving in Track 1 – 1,3,5,7,9,11,13,15,17
              B – Needles Moving in Track 2 – 2,4,6,8,10,12,14,16,
              C – Needle Moving in Track 3 – 18

   --Miss Cam             x –Knit Cam              o –Tuck Cam
   Feeder 1,3,5,7 …….. - Cotton / Tencel
   Feeder 2,4,6,8 ……….. - Polypropylene

Dial cam has two tracks of DN1 and DN2. The A and B needles are moving in track 1 and 2 respectively. Cylinder cam has four tracks, out of which the fourth track is kept idle. The A and B needles are moving in track 1 and 2 respectively and the C needle is moving in track 3. This is clearly shown in the needle set out diagram.

The dial and cylinder needle will perform miss and knit stitch simultaneously during fabric production. That is yarn from feeder 1 forms miss stitch with dial needle and knit stitch with the cylinder needle. The yarn from feeder 2 produces knit stitch with dial needle and miss stitch with the cylinder needle. This has been repeated up to third course (6th feeder). In the fourth course, the yarn from feeder 7 produces miss stitch with dial and knit stitch with cylinder. The yarn from feeder 8 fed to the dial needle produces knit stitch. Third track 36th cylinder needle makes tuck stitch with the dial needle to produce bi-layer knitted fabric. This cycle has been repeated throughout the knitted fabric production. This is shown in the cam set out diagram.

Bi-layer fabric parameters

Courses per inch      : 44
Wales per inch         : 33
Fabric weight           : 145
GSM Stitch length    : 0.27mm

Bi-layer fabric processing

The bi-layer fabric produced with Tencel/Polypropylene and Cotton/Polypropylene is subjected for dyeing with hot brand reactive dye and it has been subjected for compacting.

Processing of Tencel/Polypropylene

Dyeing

Recipe:

Hot Brand Reactive Dye (Black)   : 8 % (owm)
Sodium Chloride                           : 10% (owm)
Sodium Hydroxide                        : 10% (owm)
M: L ratio                                     : 1:10
Temperature                                 : 900C
Duration                                       : 3 hours

Processing of cotton/polypropylene

Bleaching

Recipe:

Hydrogen Peroxide         : 8% (owm)
Sodium Silicate               :10% (owm)
Sodium Hydroxide         :10% (owm)
M: L ratio                      : 1:10
Temperature                  : 900C
Duration                        : 3 hours

Dyeing

Recipe:

Hot Brand Reactive Dye (Yellow)  : 8 % (owm)
Sodium Chloride                           : 10% (owm)
Sodium Hydroxide                        : 10% (owm)
M: L ratio                                     : 1:10
Temperature                                 : 900C
Duration                                       : 3 hours

Both the bi-layer fabric of Tencel/Polypropylene and Cotton/Polypropylene fabric is processed in a winch dyeing machine. The bi-layer fabric is dyed in open width system. The fabric is then washed with soap water and then with cold water. Both the fabric is subjected for compacting to have lesser shrinkage and to maintain the width of the bi-layer fabric.

Bi-layer fabric structure

Different views of bi-layer fabric

Bi-layer fabric testing

The following test methods are used to test the comfort properties such as wetting, wicking, water absorbency, dryness, moisture vapour transfer, thermal conductivity, air permeability and fastness properties such as light fastness, washing fastness, rubbing fastness and perspiration fastness and dimensional stability of the bi-layer fabric.
Wetting (Sinking method)
Wicking (BS 3424)
Water Absorbency (AATCC 79:2000)
Dryness (ASTM D 4935-99)
Moisture Vapour Transfer (ASTM E 96-CUP METHOD)
Thermal conductivity (Lees disc method)
Air Permeability IS :11056 – 1984
Perspiration Fastness (AATCC 15-2002)
Washing Fastness (AATCC 61, 2A-2003)
Rubbing Fastness (AATCC 8-2005)
Light Fastness (AATCC 16-2004)

Results & discussion

The bi-layer knitted fabrics have been tested for comfort properties such as wetting, wicking, water absorbency, dryness, moisture vapour transfer, thermal conductivity, air resistance and other required properties such as light fastness, washing fastness, rubbing fastness and perspiration fastness and dimensional stability. Each samples were tested on both the sides. For each test, five samples were taken and the average values of the test results are discussed. Further bi-layer fabric has been produced as a garment and wear study was conducted at cold and hot climatic conditions for different sport activity to know the comfort aspects of the sports wear.

Wetting

The time taken to sink the sample completely in water is measured. The samples were placed on the surface of distilled water from a standard height.

Table 1. Wettability

C/P – Cotton / Polypropylene               T/P – Tencel / Polypropylene

The result found that the tencel layered polypropylene fabric is having quick wetting time than cotton layered polypropylene fabric.

Wetting time mainly depends upon the fabric porosity and GSM of the fabric.
Tencel yarn has regular yarn structure and good porosity in fabric which leads to lower wetting time. Even though the polypropylene yarn has same characteristics for cotton layered and Tencel layered fabric, the wetting time differs for both the fabrics due to composite fabric wetting effect. It is absorbed that the single layer wettability is dependent on fabric composite wettability and hence the wettability time differs for both the fabrics.

Wickability

Wickability of the fabric mainly depends upon the fabric construction, yarn regularity and the type of fibre and its characteristics.

Table 2. Wickability

The result found that the wickability of Tencel layered polypropylene fabric is higher than the cotton layered polypropylene fabric.
It is understood that man-made fibres have good wickability than cotton.
The wickability of Tencel is found to be higher than cotton, and the reason behind is that the Tencel fibre has smoother yarn surface which leads to good capillary action.

Even though the polypropylene yarn has same characteristics for cotton layered and Tencel layered fabric, the wickability value differs for both the fabrics due to composite fabric wicking effect. It is observed that the single layer wickability value is dependent on fabric composite wickability and hence the wickability value for polypropylene is 5 mm for cotton layered fabric and 7 mm for Tencel layered fabric.

Water absorbency

Water absorbency is measured by allowing one drop of water on the fabric and time taken to absorb the water has been tabulated. Water absorbency mainly depends upon the porosity of fabric and the type of fibre and yarn.

 Table 3. Water absorbency

The result found that the time taken to absorb water for cotton faced fabric is higher than the Tencel faced fabric because of the presence of protruding fibres on the surface of the fabric, as cotton is a natural fibre.

Since the Tencel is a regenerated cellulosic fibre, it is having uniform structure and the porosity of the fabric is higher than cotton. It leads to allowing the water particle as earliest.

Tencel layer polypropylene fabric has quicker absorbency than cotton layer polypropylene fabric even though the polypropylene layer structure is same in both the cases.

Dryness

The evapouration rate is determined by drying the selected fabric samples for 30 minutes at 1000C. The evapouration rate is expressed in terms of percentage of fabric weight reduction.

Table 4. Dryness

The result found that the dryness percentage for cotton faced fabric is higher than the tencel faced fabric because of the lower water retention in cotton fabric. (Moisture Regain for cotton - 8%, for tencel – 14%) The evapouration rate test results is average of face and back side of fabric samples.

Moisture vapour transfer

The moisture vapour transfer rate is the difference between the initial height of the water and the actual height of the water in the cups. Unit of water vapour transfer is measured in percentage.

The result found that the moisture vapour transfer is uniform in both the sides of tencel layered polypropylene fabric since yarn structure is uniform for both tencel and polypropylene. In case of cotton layered polypropylene fabric, the polypropylene faced layer shows higher moisture vapour transfer than the cotton faced layer. The reason is both sides has different materials. It is understood that moisture vapour transfer differs with face and back side of fabric.

Thermal conductivity

It is found that the thermal conductivity for tencel layered polypropylene fabric is higher than the cotton layered polypropylene fabric. The reason is the regenerated cellulosic fibre has higher thermal conductivity value than cotton fibre (Thermal Conductivity – Tencel-120 w/m/k, Cotton – 71 w/m/k).

Air resistance

It is the rate of air flow through a material under differential pressure between two faces of a fabric. Tha fabric air resistance is expressed as Kpa/sec/m.

The air resistance value for tencel layered polypropylene fabric is lesser than cotton layered polypropylene fabric. Hence the tencel layered polypropylene fabric has higher air permeability. The reason is tencel is having regular yarn structure in the fabric and better openness than cotton.

Dimensional stability

The dimensional stability of a fabric is a measure of the extent to which it keeps its original dimensions subsequent to its manufacture. Fabric sample with initial dimension was taken. It is dipped in water. After drying the measurement of change in length and width is noted.

C(L)-Cotton Length wise, C(W)-Cotton Width wise, T(L)-Tencel Length wise,T(W)-Tencel Width wise, P(L)- Polypropylene Length wise, P(W)-Polypropylene Width wise The result shows that the polypropylene bi-layer fabric exhibits abnormal area shrinkage due to higher yarn fineness. Tencel fabric has nearly two times higher in area shrinkage because it has dimensional reduction in both the directions. But in case of cotton fabric the lengthwise fabric extension and width wise dimension reduction have occurred.

Colour fastness to perspiration and laundering cotton/ polypropylene ( Grey Scale Rating)

Tencel/Polypropylene (Grey Scale Rating)
The colour fastness to perspiration of both the fabric was found to be excellent.
The colour fastness to laundering was found to be excellent in case of Cotton/Polypropylene and Tencel/Polypropylene.
The staining on cotton with Tencel/Polypropylene was found to be fair.

Colour fastness to rubbing (Grey Scale Rating)

The colour fastness to rubbing was found to be excellent during dry state for both fabrics. During wet the colour fastness to rubbing was fair for cotton/polypropylene fabric.

Colour fastness to light

The colour fastness due to light was found to be excellent in both the fabrics.

Wear study – Subjective Evaluation

The purpose of subjective evaluation is to know the suitability of sports activity with respect to the product design and climatic condition. The sportswear were given to sports person of athletic, volley ball, football, cricket and basket ball .The wear study was conducted at cold climatic condition (Temperature less than 280C) and at hot climatic condition (Temperature more than 280C). The property such as absorbency, air permeability, heat transfer, dryness and feel has been chosen to study the subjective evaluation of different sport activities. The subjective evaluation is purely based on the psychological feeling of sports person which is rated within five scale rating. The sportswear was given to five sports persons and the average results of the wear study

Findings

Sportswise Comparison:

Subjective Evaluation study reported that tencel/polypropylene sportswear shows better performance than cotton/polypropylene sportswear irrespective of sport activities.
The developed sportswear is most preferable for foo ball sport and least preferable for athletic and cricket sport.
Cotton/polypropylene sportswear is most preferable for football sport rather than volley ball, basket ball, cricket and athletic respectively. Tencel/polypropylene sportswear is most preferable for football sport rather than volley ball, basket ball, athletic and cricket respectively.

Propertywise Comparison:

The properties such as absorbency, air permeability, heat transfer, dryness and feel are explained to the sports person and the obtained ratings are discussed below.
Tencel/polypropylene sportswear shows better performance than cotton/polypropylene sportswear irrespective of properties of subjective evaluation.
The developed sports wear is most preferable for dryness property and least preferable for heat transfer property irrespective of sport activities. Cotton/polypropylene sports wear is most preferable for dryness property rather than absorbency, air permeability, feel and heat transfer respectively.
Tencel/polypropylene sportswear is most preferable for dryness property rather than absorbency, feel, air permeability and heat transfer respectively.
Climatewise Comparison:

The subjective evaluation of sportswear has been analysed at two different conditions.
Both cotton/polypropylene and tencel/polypropylene sports wear shows better performance in cold climatic condition.
In cold climatic condition, cotton/polypropylene sportswear is most preferable for air permeability and dryness property rather than feel, absorbency and heat transfer respectively.
In hot climatic condition, cotton/polypropylene sportswear is most preferable for dryness property rather than absorbency, air permeability, feel and heat transfer respectively.
In cold climatic condition, tencel/polypropylene sportswear is most preferable for air permeability and dryness property rather than feel, absorbency and heat transfer respectively.
In hot climatic condition, tencel/polypropylene sportswear is most preferable for absorbency rather than dryness, feel, air permeability and heat transfer respectively.

Conclusion

The comfort properties of bi-layer fabric has been studied objectively by testing the properties of wetting, wicking, water absorbency, dryness, moisture vapour transfer, thermal conductivity and air resistance. Also subjective evaluation has been analysed for the sportswear.

Objective Evaluation:

Tencel/Polypropylene bi-layer fabric has higher wickability, thermal conductivity and shrinkage than the Cotton/Polypropylene bi-layer fabric. Tencel/Polypropylene bi-layer fabric has lower water absorbency, dryness, wettability, moisture vapour transfer and air resistance than the Cotton/Polypropylene bi-layer fabric.
Tencel / Polypropylene and Cotton/Polypropylene bi-layer fabrics show better colour fastness properties for perspiration, laundering, rubbing and light.

Subjective Evaluation:

Tencel/Polypropylene sportswear shows better performance than cotton/polypropylene sportswear irrespective of different property and different sport activities.
Tencel/Polypropylene sportswear shows excellent performance for football sport activity at cold climatic condition.

Acknowledgement

The authors thank the Management of PSG College of Technology and Polytechnic College for providing them the necessary infrastructural facilities for carrying out this project work successfully.

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

Dr N Anbumani
Department of Textile Technology,
PSG College of Technology,
Coimbatore 641 004.

B Sathish Babu
Department of Textile Technology,
PSG College of Technology,
Coimbatore 641 004.