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  • Fibrous and non-fibrous extraneous contamination in cotton bales

    Chapter 2 - Cotton value addition - Extraneous contamination in cotton 

     
     

    Broadly, extraneous contaminants in cotton bales can be classified into two groups: fibrous and non-fibrous contaminants.

    Fibrous contaminants consist of:

    • Human hair
    • Animal hair
    • Yarn pieces
    • Cloth pieces
    • Polypropylene fibres or strings
    • Jute, ramie, hemp
    • Plastic strings
    • Long bark and weeds
    • Bird feathers

    All these contaminants disintegrate into tiny pieces in the process of opening and carding. They have almost the same buoyancy as the cotton, so it is difficult to separate them from cotton. As they are fibrous, they are easily twisted into the yarn body. Thus, fibrous contaminants are the worst component of extraneous contaminants. No chemical process can remove polypropylene and hair contaminants from yarn and fabrics. It is expensive to extract these contaminants from woven cloth, and they cannot be easily removed from knitted fabrics or garments as there is danger of causing holes.

    Non-fibrous contaminants include:

    • Paper, mint wrappers
    • Cables
    • Cartons
    • Wood
    • Stones
    • Metallic wires
    • Nuts and bolts, nails
    • Parts from ginning machines
    • Rubber
    • Leather
    • Tin
    • Insects

    These are somewhat easier to remove in the spinning process. However, they can cause damage to machine parts.

    The quantity or weight of extraneous contaminants ranges from 2 to 100 grams per ton depending on the origin. Fibrous contaminants form about 65%–90% of total extraneous contaminants.

    The quantity of contamination per ton of raw cotton seems very small in terms of weight. However, contamination is counted in cloth by frequency, not by the weight of the contaminants. One gram of fibrous contamination in a ton means 0.001% by weight, but this may equate to about 15,000 individual fibres (assuming an average length of 2 cm and denier of 10.0 for these fibrous contaminants)! The lighter the fibrous contamination, the greater the number, and hence the harder it is to remove them. 

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