COTTON – A FIBRE FOR COMFORT APPAREL
COTTON – A FIBRE FOR COMFORT APPAREL
Introduction
Cotton is a natural fibre obtained from the cotton plant (Gossypium) of family Malvaceae. The main component in the cotton fibre is cellulose. Naturally, cotton is soft and fluffy staple fibre. The shrub plant is native to tropical and subtropical regions, like India, America, Australia, Egypt, and Africa. It has very good moisture management properties like wetting, wicking, absorbency, etc. The moisture content of the cotton fibre is around 8.5%, which is higher than synthetic fibres. Due to these properties of cotton, it is good for apparel applications and it provides good comfort behavior while wearing.
Cotton Cultivation
In India, Cotton is the major crop and plays a dominant place in agriculture. The cotton has the four important species, Gossypium arboreum, G.hirsutum, G.herbaceum. The species, Gossypium arboretum and G.herbaceum are native of old world and it is grown in Asia so it is called as Asiatic cotton. The species, G.barbadense and G.hirsutum are called as new world cottons. The species, G.hirsutum, called American or upland cotton and the species, G.barbadense, called sea island or Egyptian cotton. Among the four varieties of cotton, the G.hirsutum species plays a predominant role in the total production of cotton. It contributes around 90% to the total production of cotton. All the four species of cotton is cultivated which is the speciality of India. The semi-xerophyte plant (cotton) is grown mostly in tropical conditions. For better germination of cotton, the minimum temperature 15oC is essential. The temperature between 21oC to 27oC is good for vegetative growth. Cotton is cultivated in varieties of soil ranging from well-drained deep alluvial soil to black and red soil.
Cotton fibres are complex in morphological structure and are anisotropic. The cotton fibres are grown around the single seed and the properties. The quality of cotton is governed by several factors including climatic conditions, soil, type of varieties, and other factors. So, the huge variations like length, fineness and amount of cellulose are there in the same variety of cotton and the variations in the maturity are unavoidable. As a result, the substantial differences in the fibre properties within the same lot are inevitable.
Physical properties of Cotton Fibre
The diameter of the cotton fibre is in the range of 8-20 micrometers and the length is in the range of 20 to 35 millimeters. Some special varieties of cotton may be more than this limit.
Cotton fibre may be classified as mature fibre and immature fibre. A mature fibre consists of a primary wall and a secondary wall encapsulated by a cuticle, a waxy substance. The thickness of the outer wall or a primary wall is less than 0.5 micrometers. It consists of a mixture of cellulose fibrils, waxes, and pectin. Out of this, 87-94% is cellulose. Once the other substances like, proteins, waxes, and pectin, etc., are removed, the resultant pure cellulose fibre, the cotton is obtained. Cotton is a natural polymer consist of pure cellulose. The secondary wall, next to the lumen is covered by the primary wall.
Differential helical pitch, a third layer, and a part of the second layer is often called as a winding layer which is there in between the first layer and the second layer. The molecules of the cellulose are arranged in the helix structure around the center axis. The strength and durability of the cotton, is mainly due to the arrangement of cellulose generally around thirty layers is coiled inside the cellulose. This gives the unique properties to the cellulose. The extend of the primary and secondary wall indicates the maturity of cotton. The immature and over mature fibres are not desirable to spin the fibres.
In the centre of the cotton fibre, a narrow gummy substance called lumen present in the cotton fibre. The size of the lumen is reduced when the cotton fibre grows. If the lumen is bigger, the fibre may be immature in nature. On the other hand, if it is small, the maturity of the cotton increases. The full mature cotton will have very small or no lumen. Half mature cotton, the lumen shrinks when it is dried and the cell collapse and forms the irregular structure and creates convolution in the length direction. Due to this, the fibre becomes ribbon-like in nature.
The crimp is due to the twist in the fibre facilitate to adhere to the fibre one over another and this is one of the primary requirement for spinning the fibre. The fibres become stiffer when it is stretched in water before drying. The stretched nature of the fibre will have very less amount of convolutions.
The cotton fabric properties can be modified by chemical treatments. Various chemical treatments have been given to the cotton fabric to improve the comfort properties of the fabric. For instance, the soft finish is given to cotton fabric to improve the soft handle of the fabric, biopolishing is given to Cotton to reduce the pilling behavior of the fabric, calendaring, and mercerizing is given for lustre, crosslinking agents, the resin is given for dimensional stability. Other behaviors like flame retardancy, water repellent, and waterproof, antistatic are improved by chemical treatments.
Conclusion
Cotton is a cellulosic fibre widely used as apparel for its comfort properties. The properties like moisture, air and thermal transport behavior of the fibre increase its comfort behavior. Some properties like softener, stiffener, pilling, lustre, shrinkage and dimensional behavior are altered by chemical treatments. Shrinkage and creasing are the two major drawbacks for cotton fibre and that can be improved by chemical treatments. Overall, cotton has good comfort properties to use in the apparel industry.
image source
- cotton cross section: https://www.sciencedirect.com/topics/engineering/cotton-fibre
- cotton: https://times.mw/cotton-market-in-trouble-aicc/