Flame Retardant Finishing of Cotton Fleece Fabric: Part III — The Combination of Maleic Acid and Sodium Hypophosphite

Cotton fleece does not meet the federal flammability standard (16 CFR Part 1610: `Standard for the Flammability of Clothing Textiles') without chemical treatment. In this research, the chemical reactions of maleic acid (MA) on cotton in the presence of sodium hypophosphite (NaH 2 PO 2 ) and the use of the combination of MA and NaH 2 PO 2 as a flame retardant finishing system for cotton fleece are investigated. It has been found that MA esterifies cotton cellulose at relatively low temperatures in the presence of NaH 2 PO 2 as catalyst, and that MA esterified to cotton is able to further react with NaH 2 PO 2 at higher temperatures (≥150°C), which bonds phosphorus to the cotton cellulose. The reactions between MA and NaH 2 PO 2 on cotton also lead to the cross-linking of cotton cellulose. The treatment using the combination of MA and NaH 2 PO 2 is effective in reducing the flammability of cotton fleece from `Class III' to `Class I' (16CFR1610). This is a nonformaldehyde and low cost flame retardant finishing system for cotton fleece. The treated cotton fleece still maintains `Class I' flammability after 20 home laundering cycles.