An Economical Durable Flame-Retardant Finish for Cotton

Abstract

Selected low-cost N-methylol compounds have been incorporated with tetrakis(hydroxymethyl)phosphonium hydroxide (THPOH formulations and applied to cotton fabric by a number of different processing techniques. N-methylol compounds evaluated in this study were trimethylolmelamine, dimethylolethyleneurea, and dimethylolmethoxyethyl carbamate. THPOH reacts with ammonia at room temperature and with methylolamides at elevated temperatures. The flame-retardant finish produced by reacting the phosphonium hydroxide with ammonia is very durable and effective at modest add-ons. Even with modest add-ons (12–20% depending on fabric construction and weight), the phosphorus content is rather high (up to 6%). This study has shown that the amount of phosphorus needed in the flame retardant can be reduced to a fraction of that originally required by increasing the nitrogen content. Use of trimethylolmelamine and THPOH with an ammonia cure, followed by a heat cure, produced the most effective flame resistance. Treated fabrics had 100% tensile strength retention and a good hand. This treatment has resulted in the use of lesser quantities of THPOH to produce a lower-cost durable flame-retardant finish for cotton.