Alkaline Retention
Post-bleaching rinse baths retain unbound alkaline compounds that alter finished textile pH if improperly neutralized. Unremoved fabric residual alkali originates from sodium hydroxide or sodium silicate applied during mercerization and scouring operations. Wet processing mills measure extractable alkalinity to ensure materials reach neutral pH prior to resin finishing or garment assembly.
Excessive alkaline retention causes yellowing during high-temperature curing and fabric tenderization over storage.
Neutralization Reaction
Acidic washing liquors containing organic acids neutralize alkaline compounds trapped deep within cotton fiber structures. Standard rinsing alone fails to remove bound alkali from heavy woven constructions or dense knitted fabrics. Inadequate acid bath concentration leaves residual sodium compounds within the core of the yarn bundle, leading to delayed pH migration toward the surface.
Controlled acid dosing systems monitor wash liquor pH to ensure thorough chemical neutralization throughout the fabric cross section.
Quality Consequence
Elevated fabric surface pH degrades reactive dye stability and causes skin irritation in wearers of finished garments. High alkaline content also accelerates yellowing during hot pressing and storage.
Verification Method
Standard test methods involve boiling fabric swatches in distilled water followed by potentiometric titration of the aqueous extract. Laboratory technicians calculate total alkali content expressed as a percentage of dry fabric weight. Buying houses reject shipments exceeding maximum allowable residual alkalinity limits to prevent garment discolouration.
