Concentration Specification
Aqueous sodium hydroxide solution with a density of 48 to 52 degrees Twaddell maintains the specific swelling capacity required for cellulose modification. Mercerizing caustic soda acts as the primary swelling agent in the treatment of cotton fibres to increase dye affinity and lustre. Manufacturers determine the concentration through precise hydrometer testing to ensure the lye maintains its target density during continuous circulation.
Processing Mechanism
Cellulose chains within the cotton fibre shift into a more open configuration under the influence of this alkaline environment. The mercerizing caustic soda penetrates the crystalline regions of the fibre and forces the structure to shift from cellulose I to the more amorphous cellulose II. Tension applied during this period prevents excessive shrinkage and contributes to the permanent alignment of the polymer chains.
Chemical Maintenance
Contamination by hemicellulose and other impurities accumulates in the bath over time and requires constant monitoring. Recirculation through a filtration unit removes suspended solids while heat exchangers keep the temperature within a narrow range to prevent degradation of the active components. High levels of carbonate build-up reduce the effectiveness of the solution and necessitate partial or complete bath replacement.
Performance Constraint
Variations in the concentration of the lye lead to uneven dye uptake across the batch. The swelling effect depends entirely on the interaction between the alkali strength and the dwell time of the fabric within the saturation tank. Inadequate penetration results in patches of lower reflectance that remain visible even after the finishing process completes.
