Sodium Polyacrylate (PAAS) is used in textile printing and dyeing primarily as a dispersant, thickener, and sizing/ adhesion agent, with its function highly dependent on molecular weight. Low-molecular-weight PAAS excels at dispersing dyes and preventing back-staining, while higher-molecular-weight grades serve as thickeners and binders.
Primary Applications
1. Washing Off & Anti-Back-Staining (Low Molecular Weight)
After dyeing or printing, unfixed dyes on the fabric surface must be removed. Low-molecular-weight PAAS (optimally around 9,527 molecular weight) acts as a dispersant in the soaping/washing bath. It adsorbs loose dye molecules, keeping them stably suspended in the wash liquor so they do not re-deposit onto the fabric. Research shows this can improve wet rubbing fastness by up to 2 grades and color staining fastness by 2–3 grades .
2. Thickener for Printing/Dyeing Pastes
PAAS is used as a thickener or finishing auxiliary in printing and dyeing processes to improve the printing effect and fabric hand feel. Typical addition levels are 0.1%–1% of the color paste or finishing liquor mass, adjusted according to fiber type and process requirements .
3. Sizing and Adhesion
In textile processing, PAAS serves as a sizing agent and flocking adhesive, and is also used in formulations for water-repellent finishing of fabrics .
4. Specialty Applications
Yarn Hairiness Reduction: PAAS solution applied during spinning (a “liquid-feeding” technique) can reduce yarn hairiness by over 60%, while also improving yarn strength and abrasion resistance .
Natural Dye Pad Dyeing: In wool fabric dyeing with insoluble curcumin, a PAAS-containing paste provides excellent stability and dyeing performance, achieving high color strength (K/S value up to 16.15) under optimized wet-steaming conditions .
Key Consideration
The effectiveness of PAAS is molecular-weight dependent. For dispersing/anti-staining applications, low molecular weight (roughly 5,000–10,000) is preferred for optimal dispersion without excessive viscosity . For thickening and adhesive functions, higher molecular weight grades are typically used.