Desizing is done in order to remove the size from the warp yarns of the woven fabrics. Warp yarns are coated with sizing agents prior to weaving in order to reduce their frictional properties, decrease yarn breakages on the loom and improve weaving productivity by increasing weft insertion speeds. The sizing material present on the warp yarns can act as a resist towards dyes and chemicals in textile wet processing. It must, therefore, be removed before any subsequent wet processing of the fabric.
Objects of Desizing:
- To remove the starch material from the fabric.
- To increase the absorbency power of the fabric.
- To increase the affinity of the fabric to the dry chemicals.
- To make the fabric suitable for the next process.
- To increase the luster of the fabric increase of dyeing and printing.
The factors, on which the efficiency of size removal depends, are as follows:
- Type and amount of size applied
- Viscosity of the size in solution
- Ease of dissolution of the size film on the yarn
- Nature and the amount of the plasticizers
- Fabric construction
- Method of desizing, and
- Method of washing-off
Methods of Desizing:
- Hydrolytic Method
- Oxidative Method
- Rot Stepping
- Alkali Stepping
- Acid Stepping
- Enzymatic Stepping
2. Oxidative Method
- Bromide Desizing
- Chlorite Desizing
- Ammonium per Sulphate Desizing