"Well prepared is half finished", the age old and universal adage probably has roots in pretreatment of textile material. Ashok Athalye attempts to cover aspects related to the evaluation of selection, application and performance (SAP) properties of chemicals used in textile wet processing.

The aesthetic appeal and appearance, feel and comfort, fitment and shape retention of the finished fabric are dependent on the effective preparation and colouration of the textile substrate.

The final textile product, be it a ready-to-wear apparel, home textile item or a technical performance material, undergoes many stages of processing. The steps involved, depend on various factors, such as source of fibre - plant, animal or synthetic; form of substrate - yarn, woven, knit, towel, garment or carpet; method of processing - exhaust, semi-continuous or continuous; and use of machinery under low/high turbulence or low/high temperature.

Fig 1. Processing of Cotton

The processing steps are aimed at optimising extraction of impurities, controlling residual moisture content, achieving the desired extent of absorbency, maintaining uniform standard of white, minimising the damage and loss of strength of the fibre, and ensuring consistent pH from core to fibre surface.

Irrespective of the textile material used, the pre-treatment process is highly chemical-intensive and the desired result is possible only when adequate chemicals are used. Apart from basic chemicals like caustic soda, soda ash, acetic acid and hydrogen peroxide, many other specialised auxiliary chemicals are used during textile wet processing and broadly categorised based on the intended purpose or processing step for which they are used. A broad list of chemicals generally used during cotton processing is given below

  •         Desizers and dispersants

  •          Emulsifiers and detergents

  •          Demineraliser and sequesterants

  •          Bleach stabiliser and quenchers

  •          Deaerators and defoamers

  •          Acidic and alkaline pH controllers

  •          Levelling and dispersing agents

  •          Dye bath controllers and migration inhibitor

  •          Dye accelerator and penetrants

  •          Anti-crease lubricant and friction controllers

  •          Dyefixers and wash-off improvers

  •          Reducing and oxidising chemicals

  •                Colour fastness improvers