Food Chain : Take care of all the components to ensure quality and safety
Food Chain
Cotton is a seed hair which has to undergo various stages of handling and processing before the textile mills use the fibres. It is essential that proper care is taken at various stages of handling and processing to ensure that the inherent quality of cotton is not adversely affected. The quality of the fibres, as they grow on the plant is mainly dependent on the pedigree of the plant and the conditions under which the plant has been grown. This inherent quality can be improved upon only by suitable breeding, selection and agronomic practices. But, no improvement is possible after the cotton bolls on the plant have opened out. However there are chances that this quality may not be maintained during subsequent handling of the produce with the result that the price realized for the produce is also reduced.
In India, harvested cotton is generally sold by cultivators in the form of unginned seed cotton or kapas. The merchants or marketing organizations who buy the kapas get it ginned. Ginning is the mechanical process, which separates fibres from seed. The ginned lint is then sold to textile mills. When kapas is received at the ginning factory, the ginner should take into account the inherent quality of cotton and the condition in which it has been received so that he can adjust the gins suitably to maintain the quality of the material.
Indian cottons are hand picked and hence should not contain much trash or foreign matter. Yet many of them contain considerable amount of trash due to faulty methods of collection and storage. As the cotton pickers are usually paid on the basis of quantity of kapas picked, they often tend to pick bad kapas (immature bolls, leaf bits, insect attacked bolls etc.) along with good kapas. Such trash and bad locules have to be removed before ginning. The presence of trash affects the overall quality of the fibres and gives a poorer appearance. The seeds from insect attacked and immature bolls being more fragile get crushed during ginning resulting in staining of lint by the oil oozing out of the cut-seeds. This oil acts as a medium for growth of micro-organism acts as a medium for grow of micro-organisms which will destroy the lint.
Further, the methods of transport of kapas to the factory adopted by the farmers are in many cases primitive and as a result, kapas is exposed to vagaries of weather in addition to poor handling by illiterate personnel engaged in transporting kapas.
A common complaint against ginners and cultivation relates to the mixing of different varieties. As superior varieties fetch better price in the market, inferior varieties are mixed with them and the mixed lot passed off as superior type. The admixture of inferior type lowers the quality of the superior type, due to difference in the types of cottons, the uniformity of the staple is also considerably reduced; hence the processing losses during spinning are heavy and the yarn produced is of low quality. Another problem is in dyeing. If there are marked differences in fineness of the varieties mixed, the resultant fabric cannot be dyed uniformly and the cloth will have patchy appearances.
Fibre length: The greatest contribution to spinning performance comes from fibre length. The market price is largely based on length only. Longer cottons give better spinning performance than shorter ones. Any sample of cotton contains fibres varying from 2 mm onwards. Hence, in the laboratory, average length of the fibres expressed as span length indicating the spinnable length of the fibre is evaluated.
Fineness :Fibre fineness is the measure of thickness of the cotton fibre. It varies from 15-20 micrones. As the cross-sectional dimensions of the fibres are irregular, its direct determination is difficult. Hence, fineness expressed as weight per unit length of the fibre and called micronaire value.
Maturity : Maturity is the index of the development of the fibres indicating the cellulose content of the fibres. Presence of excessive amount of immature fibres causes waste losses and yarn quality is affected.
Strength : Fibre strength directly influences yarn strength, stronger cottons produce stronger yarns.
Desirable fibre properties:
Jet spinning 30 mm and above
Rotor 25 - 28 mm
Fibre fineness 3-3.8
Strength 28 g. /tex
Maturity 80%
Elongation 7%
Trash < 2%
European Banned AGMARK Standards

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