EXECUTIVE SUMMARY
Special designs have been made to suit various sports. This is important as it plays an important role in sports performance. Companies have resorted to good quality textile materials to design sportswear clothing. Sportsmen should wear comfortable costumes for them to perform well in their competition. When designing sportswear, the market has to be identified first. That is the design to be used, the materials required and footwear. The fabrics available should also be identified. The comfort of the wearer is also considered as this affects performance.
History of polymers
Polymers have been used for centuries to manufacture plastics. Due to advance in technology synthetic polymers were developed. Since then new polymers have been discovered and designed for specific purpose. Polymers are long chains of mers attached together to form a structure. Mers are organic molecules that combine together to form polymers. The process by which mers are joined together is called polymerization. There are two types of polymerization; additional polymerization and condensation polymerization. Addition polymerization is the process of adding mers to an end of a developing chain.
There are three methods of additional polymerization; initiation, propagation and termination. Initiation is when a radical breaks the weak bond in the double bond between two carbon atoms in polyethylene, C2H4, and carries an electron while leaving one behind. Propagation is the continuous addition of ethylene molecules to the growing chain. Termination is addition of mers to the end of the chain. Condensation polymerization is when water molecules condensed from a reaction attaches itself to the growing chain. Thermoplastics include; polyethylene, poly vinyl chloride, polystyrene, and polypropylene. Thermosettings include; phenolics, formaldehydes, and polyesters.
Structure of polymers
Carbon is the major element in polymers due to its wide variety of covalent bonds. Long chains of carbon form polymers. The first polymer formed by carbon is known as polyethylene. There are three types of polymer structures; linear chains, branched chains and cross- linking. Linear chains are formed when organic molecules linked results in no deviation and have only two reactive sides. Branched chains are formed when organic molecules linked results in a deviation. Cross- linked chains are formed when branched chains link together between adjacent chains. Organic molecules are linked together by strong covalent bonds. The chains formed determine the type of structure and its properties. Thermoplastic polymers are formed from weak bonds that can be broken by heat.
Characteristics of polymers
Polymers have low density and do not corrode easily. They can be moulded into different shapes. Polymer products can be recycled thus economical. They have low elasticity thus they breaks when subjected to high tension. They have low temperature resistance. They can be dyed to different colours or made transparent.
Raw materials
The major raw material used to manufacture polyester is ethylene which is extracted from petroleum.
The manufacturing process
Polyester is a long chain of polymers formed from combination of esters. Esters results from the reaction of alcohols with carboxylic acids. There are two types of polyesters; saturated polyesters and unsaturated polyesters. Saturated polyesters are less reactive than unsaturated polyesters. Polyester fabrics are strong, durable, and easy to clean dries quickly, and maintain their shape. Polyesters are used to make clothes, ropes and plastic bottles in industries. Clothes made from polyesters can be washed using a fabric softener and dried at low temperatures. The fabric can also be dry cleaned and warm ironing is recommended.
There many methods used to manufacture polyester. However, the method used determines the end product. The products formed can be filament, staple, tow and fiberfill. The filament type has long strands which produces soft fabrics. The staple type has short strands which produces polyesters that can blend with other fibers. The tow type has loose strands whereas fiberfill is compact and can be used to manufacture pillows.
Polymerization
Polyester is formed from the reaction of dimethyl terephthalate with ethylene glycol in presence of a catalyst at 150-210 °C. The resulting product is a monomer alcohol which is then combined with terephthalic acid and the temperature increased to 280°C. Polyester which is clear and molten is passed through a slot to form long strands.
Drying
The long molten strands formed are cooled then cut into small pieces and dried completely.
Melt spinning
Polymer pieces are heated at 270°C to melt and form a liquid solution. The solution is poured into a metal container known as spinneret and squeezed through the small round holes in it. Special fibers produced are joined together to form a single filament. Thus, the size of the yarn is determined by the number of holes in the metal container. Additives can be mixed with the solution during spinning to improve on the quality of the product.
Drawing the fiber
The polyester formed is soft and very long. Due to the stretching forces, the polyester molecules are parallel thus forming a stronger fiber. After drying, the filaments become solid and strong. The resulting fibers may be of various forms depending on what was desired. For instance, they could be soft textured, great diameter and length.
Winding
After they are harvested, the yarn is wounded into various shapes for packaging since they are ready to be used.
Production of polyester fiber in comparison with other fibers
Scale: 5cm represents 4000 metric tons.
Manufacture of Staple Fiber
The process of manufacturing staple fiber is similar with filament yarn only that, the spinneret has many holes and the resulting product is called tow.
Drawing tow
The tow formed is cooled faster in the container that collects thick fibers. The tow strands collected are passed through heated rollers to increase their lengths.
Crimping
The emerging tow is collected in the compression boxes which folds the fibers to 15 crimps per inch. This makes the fibers to be compacted together.
Setting
After crimping, the tow is heated at 150°C to completely dry. Thus the tow can be collected easily.
Cutting
The tow is then cut to shorter lengths depending on the materials desired to be blended with.
Mesh Fabric
Multipurpose FR (fabric) mesh can be used to make the running top. Multipurpose FR mesh is knitted with polyester fabric and vinyl finish applied. It is less flammable and can be used as a shield against sun and wind. It is light in weight and has breathing space at the bottom. Textile mesh is another type of mesh that could be used. It is strong and retains its color. It can also be used as a shield from sun and wind. It is porous thus allow free air circulation. It is also coated with vinyl. Heavy duty tramp is woven polyester fiber that is coated with a thick layer of vinyl. It is very strong and mildew resistant. It does not absorb ultraviolet radiation. It is mainly used in industries. Shade plus is another vinyl coated polyester material. It is tight, less flammable and meets the textile standards. It is heavy and can be used as shield from the sun and wind and allows air circulation.
Chemical properties
Polyester fibers have high resistance to alkalis at high temperatures. It does not react with acids at high temperatures. However, long exposure might result to the destruction of the fiber. The fiber does not dissolve in organic solvents. Thus, bleaching detergents can be used. They are durable and can be taken care of easily. However, Polyester fiber has low moisture retention and is highly flammable. Attracts dirt easily and can be difficult to clean. Polyester fiber dissolves in some bases.
Physical properties
The moisture content is low and the density depends on the type of polyester fiber. It has a melting point of 300°C. The shrinkage, strength, elasticity, size and shape depend on the method of manufacture.
Thermal properties
Polyester fiber acts as a thermo insulator. The thermal insulation property of polyester fiber depends on its thermal conductivity, density and its heat emission. Heat is transferred to the fabric through conduction, convection and radiation. Polyester fiber has high heat resistance. Thick polyester fibers are good thermal insulators. High fabric density increase heat conduction and heat resistance. Thick fabrics have low temperatures. When the fiber is exposed to high temperatures, the amount of heat passing through the fabric is increased. The thermal and moisture regulation of polyester fabrics depends highly on the properties of raw materials used during the manufacture (Morris, 1953).
Dyeing properties
Polyester fibers have high dyeing ability. The fabric can be dyed to any color desired. A chemical additive of different colours as desired is added to the spinneret. The fiber does not react with colours.
Optical properties
Polyester strands are transparent and thus allows light to pass through them. Light pass through the polyester strands across covalent bonds and vibrating molecules. The transparency of the fiber is determined by the electrons in the atoms and the frequency of light.
Other properties
Has high resistance to sunlight. The fiber can’t be damaged by soaps and detergents used in laundry. It absorbs oil easily.
General Polyester Fiber characteristics
The length of polyester fiber depends on how it was manufactured i.e. filament form or staple form. Therefore it can be adjusted depending on what is desired. The texture of the polyester fiber can be controlled with the type of production. The cross sectional shape can be round, triangular, elliptical or pentagon as desired. Their color can be changed from white to another color by addition of chemicals during spinning. The strength of the fiber is determined by its density. The fiber has good elasticity and is largely used for knitting in garment industries. The crease stain in the fabric can be removed easily. It does not loose shape when subjected to high heat. The fabric is warm, attracts less dirt and can be cleaned easily. It is not affected by bleaching reagents. It does not react with acids and alkalis. Does not dissolve in organic solvents thus can be dry-cleaned. Polyester fabric should be subjected to less heat as it melts and the strength of the polyester is reduced. Thus, warm ironing and less exposure to sunlight should be applied. Exhibits good dyeing abilities at high temperatures and responds to all colours. Resists mildew, moths and insects infestation. Polyester fiber can be used in its pure form or blended with other fibers such as cotton, nylon and wool.
Knitting of polyester fabric for sportswear
Knitted polyester fabrics are durable. This means that they maintain their shape and appearance. They cannot tear easily and regain their shape when stretched. The form in which a fabric is created affects its durable nature. Knitted fabrics have a tendency to stretch which may be an advantage or a disadvantage. Plain and twill weave designs makes sportswear durable. Few knitted polyester fabrics have been developed for footwear. Some fabrics are also knitted for protection against ultraviolet radiation.
Pictures of knitted fabric
Technical face
Technical back
Technical face
Technical back
Major End Uses for Sportswear
The most important property of polyester fiber used to design sportswear is its ability to absorb sweats and dry fast. Athletes do intense physical activities which make them sweat and this is uncomfortable to the body. Thus, if their costumes can absorb the sweats and emit them to the atmosphere; they will be comfortable and increase their performance level. The frictional force is high when the costume is wet unlike when it’s dry. Wet clothing is uncomfortable and thus polyester fabric is suitable for sportswear as it dries quickly. Polyester fiber is also thermal stable.
The future
Polyester fiber has undergone rapid growth since it was first discovered. Back then, its fabrics were popular since they were easy to take care of. After sometime, its popularity reduced and the clothes made from polyester were criticized and lost value. More new polyester forms are continuously generated up to date which has revived its image. Varieties of polyester fabrics manufactured have many uses. It is difficult to distinguish different types of polyester fabrics as they have now flooded the market. Many clothing designers have created a line on these new fabrics. Research has been done at textile institutions and more products of wide applications are yet to be introduced.
Environmental consideration for fiber
Polyester fibers manufactured are useful in the environment in many ways. For instance, it can be used to prevent soil erosion, land stabilization, and water and air filtration. Plastics that have been used by consumers can be recycled and used to manufacture polyester fibers. A good example is plastic soda which readily available. Most plastics disposed are hazards to the environment. Therefore, recycling of these plastics protect the environment. The energy used to manufacture polyester fibers in the industry is harmful to the environment as it involves emission of poisonous gases to the atmosphere. Using machines to wash and dry clothes is also harmful. Therefore, consumers should resort to washing with cold water and drying clothes on hanging lines to protect the environment. Some polyester fabrics are coated with oil finishes which may be volatized by textile industrial processes thus polluting the working environment (Corbman, 1983).
Conclusion
Thermal and moisture retention of a fabric is highly dependent on the properties of raw materials used during manufacture. Sportswear need to provide comfort to the user. The wicking ability of a fabric is determined by its structure, heat resistance and water vapour and air transfer. In case of warm weather, sportswear with low thermal resistance, high heat conductivity and absorptive are preferred. Therefore, fabrics with such qualities should be designed. Also, fabrics with high water vapour permeability and moderate wicking ability is recommended. During cold weather, fabrics with high heat resistance, high water vapour diffusion and average wicking ability are preferred. Polyester fiber has bright future in sportswear industry. Sportswear clothing should be made using polyester fabrics due to their ability to absorb sweats from an athlete’s body and exposing for evaporation thus cooling the body. This increases the level of performance of the athlete since the clothing is comfortable.
References
Corbman, Thomas and Benard Beiit. Textiles: Fibre to fabric. New York: McGraw-Hill, 2003.
Hes, Leah. Mutual bonding of textile layers. New Jersey: McGraw Hill, 2006.
—. Thermal properties of nonwovens. Geneva: International Publishers, 2007.
Hongu, Tatsuya and Phillips Glyn. New fibers. New York: Cengage Learning, 2004.
Jirsak, Owens. Thermal insulating properties. New Jersey: New Academic Publishers, 2006.
Morris, Jospeh. Thermal properties of textile materials. New York: Routledge, 2007.
Ukponmwan, Joseph. Thermal insulation properties of fabrics. New York: Cengage Learning, 2003.
Voyce, John and Sam Towlson. Elastic Textile. Cambridge England: Woodhead Publishing Limited, 2005.
