Chemical Anchoring and Crosslinking of Polyelectrolyte Complex for Durable Flame Retardant Cotton

Polyelectrolytes such as polyethyleneimine (PEI) and poly(sodium phosphate) (PSP) can be combined to form a flame-retardant (FR) polyelectrolyte complex (PEC). PECs offer a halogen-free, environmentally benign flame-retardant solution that renders various substrates, including cotton, self-extinguishing. Despite these positive attributes, their durability is limited due to the PEC’s non-covalent interactions that can be disrupted during laundering. This study presents a chemical anchoring and crosslinking strategy to improve the wash durability of PEI/PSP flame retardant coatings on cotton textiles. Citric acid and sodium hypophosphite covalently anchor the PEI to the cotton substrate, while glutaraldehyde crosslinks the PEC to form a robust polymer network. The coated fabrics exhibit intumescent and self-extinguishing behavior, even after 15 standard machine wash cycles. This dual-approach significantly improves the practicality of PEC-based FR coatings for everyday textile applications and provides an avenue for adapting existing PECs to be more durable.