Saturday, November 14, 2009

Stages of Cotton Processing - III

Cotton Processing Flow Chart

Various stages of wet processing, shown in the above figure, involve treating greige goods with chemical baths and often additional washing, rinsing and drying steps. Some of these stages may be optional, depending on the style of fabric being manufactured or whether the material being wet-processed is a yarn, or a knitted or woven fabric.

Some of the key steps in the treatment of cotton material include singeing, desizing, scouring, bleaching, mercerizing, as well as dyeing and finishing.

Singeing is a dry process that removes fibres protruding from yarns or fabrics. Desizing is a wet process that removes the sizing material applied to the warp yarns before weaving. Scouring is a cleaning process that removes impurities from fibres, yarns or cloth through washing, usually with alkaline solutions. Bleaching is a chemical process that decolourizes coloured impurities that are not removed by scouring and prepares the cloth for further finishing processes such as dyeing or printing. Mercerization is a chemical process to increase dyeability, lustre and appearance. Dyeing operations are used at various stages of production to add colour to textiles and increase product value. Dyeing can be performed using batch or continuous processes. Common methods of batch or exhaust dyeing include package, beam, beck, winch, jet and jig processing. Continuous dyeing processes typically consist of dye application, dye fixation with chemicals or heat, and washing. Dyeing processes may take place at any of several stages of the manufacturing process (fibres, yarn, piece-dyeing). Stock dyeing is used to dye fibres; yarn dyeing is used to dye yarn; and piece/fabric dyeing is done after the yarn has been constructed into fabric. Printing is a localized or patternised coloration of the fabrics. Fabrics are printed with colour and patterns using a variety of techniques and machine types. Finishing encompasses chemical or mechanical treatments performed on fibre, yarn or fabric to improve appearance, texture, or performance.

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