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 (NaH2PO2) and the use of the combination of MA and NaH2PO2 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 NaH2PO2 as catalyst, and that MA esterified to cotton is able to further react with NaH2PO2 at higher temperatures (>= 150 degrees C), which bonds phosphorus to the cotton cellulose. The reactions between MA and NaH2PO2 on cotton also lead to the cross-linking of cotton cellulose. The treatment using the combination of MA and NaH2PO2 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.