Removal Operation
Preparatory wet processing of woven fabrics begins with the systematic extraction of temporary protective sizing agents applied during yarn preparation. In fabric preparation, desizing converts insoluble starches, water-soluble polymers or synthetic polyvinyl alcohol films into soluble fragments for washing away. Clean yarn surfaces are required prior to bleaching and dyeing operations.
Failure to eliminate size materials leads to patchy dye uptake and stiff fabric handle.
Enzymatic Breakdown
Chemical breakdown methods depend entirely on the chemistry of the applied sizing agent. Amylase enzymes specifically target starch molecules, cleaving alpha-1,4-glucosidic bonds to convert long macromolecular chains into short water-soluble dextrins and glucose units. Enzymatic treatment operates within strict pH and temperature windows to prevent enzyme denaturation.
Synthetic sizes like polyvinyl alcohol require hot alkaline washing without enzymatic digestion. Complete size removal opens fiber pores, allowing uniform penetration of subsequent bleaching and mercerization chemicals.
Efficiency Impact
Efficiency during size removal dictates down-stream processing quality across the finishing plant. Incomplete desizing causes streakiness in continuous dyeing and resist spots during rotary screen printing. High washing temperatures ensure detached size polymers remain suspended in bath liquor.
Residual Measurement
Testing protocols quantify size removal using TEGEWA violet scale ratings and iodine staining tests. Laboratory inspectors apply potassium iodide solutions directly to desized fabric surfaces to evaluate residual starch levels against standard color scales. Quantitative weight loss analysis confirms whether size content meets commercial acceptance thresholds for dyeing.
