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  • Trash (non-lint) content

    Chapter 2 - Cotton value addition - The impact of cotton fibre properties on textile

    Trash, often referred to as non-lint, commonly comprises fragments of leaves, bark and grass, as well as particles of sand and dust. The levels of such contaminants are determined by growing, harvesting and ginning conditions. Plastic materials also represent a serious source of contamination.

    Both the type of trash and the quantity are important in determining processing behaviour and performance and waste levels. Trash content can be measured by various laboratory instruments as well as by high volume systems (although the latter do not, as yet, provide a satisfactory means of doing so), providing a measure of trash area and number (count) and leaf grade. Sophisticated systems, using image analysis and colour differentiation, have been developed to more accurately measure trash levels and type.

    Trash content is directly and indirectly related to processing waste, the removal of trash being associated with fibre breakage and the removal of fibres as waste, as well as nep formation. These in turn can considerably affect spinning performance, particularly rotor spinning, and yarn quality. Air-jet and friction spinning require even lower levels of non-lint content than rotor spinning. Fabric and yarn appearance can be adversely affected by trash that is not removed during processing. Trash and dust content can have a particularly adverse effect on rotor spinning performance and yarn properties, since it causes a build-up of deposit in the rotor groove which interferes with yarn formation, and therefore causes end-breaks and reduces yarn quality. Seed coat fragments, with tenaciously clinging fibres, are an important cause of yarn faults, also adversely affecting spinning and yarn performance.

    Respirable dust, or agents associated with the dust, create health problems and can lead to byssinosis. Fine particles of trash can also form the nucleus for neps. Microdust can affect the wear of spinning components, particularly in newer spinning systems such as rotor, friction and air-jet, and also clog the rotor groove and air-jet nozzles.

    Foreignmatter and other contaminants, such as plasticmaterials, can have a very harmful effect on quality, not only adversely affecting processing performance (notably spinning), but also showing up as faults in the fabric, particularly after dyeing. ITMF studies indicate that claims related to contamination amount to 1%–3% of total sales of cotton and cotton blend yarns.