Chemical Degradation
Chemical reactions that break polyester chains belong to the category of polymeric degradation processes occurring under alkaline conditions. Synthetic fibres like polyethylene terephthalate undergo ester cleavage when exposed to high temperatures and strong bases during finishing treatments. This reaction leads to the reduction of polymer molecular weight.
Saponification Effect
Surface modification of polyester fabrics occurs when sodium hydroxide attacks the ester carbonyl groups. This targeted ester cleavage, also known as alkaline weight reduction, removes a thin layer from each fibre to increase softness. The process must be monitored closely to prevent excessive loss of tensile strength.
Process Control
Controlling the rate of reaction requires precise management of treatment duration and alkali concentration. If the ester cleavage progresses too far, the fabric suffers severe weight loss and fibre thinning, which renders the garment prone to tearing. Mills use automatic dosing systems to add sodium hydroxide gradually to the bath, maintaining a steady reaction rate across the entire batch.
Rinsing with weak acid after treatment halts the reaction immediately.
Material Impact
Physical testing of the treated fabric confirms the success of the weight reduction process. Measures of weight loss and tear strength assess the degree of ester cleavage achieved. Proper execution results in a silky drape without compromising the durability of the finished garment.
