A durable-flame retardant based on tetrakis (hydroxymethyl ) phosphonium hydroxide (THPOH), urea, and trimethylolmelamine has been developed and applied to cotton fabric. The process is accomplished by padding fabric through a water solution of the three components to a wet pickup of about 75%, drying at moderate temperature, and curing at an elevated temperature. Solutions of 25-34% total solids containing the three components in a molar ratio of 2 : 4 : 1 (THPOH: urea : methylolmelamine), when applied to cotton fabrics of 8-9-oz weight, imparted flame resistance, and only minimal losses in breaking and tearing strength. The treated fabrics retained 91-95% break strength and 73-80% tear strength. Wrinkle recovery angles (W + F) of treated fabrics ranged from 280° to 306°. Wash- wear and durable-press properties are discussed. Little or no yellowing of treated fab rics was observed when bleached with sodium hypochlorite solution and scorched between heated plates. Resin add-ons of fabrics treated in this manner ranged from 15 to 19%. Flame resistance of fabrics treated by this process is retained after boiling the treated fabrics in a soap-sodium carbonate solution for 3 hr or after 15 laundering cycles.

Durable flame-retardant treatments based on a vinyl phosphonate oligomer or Thps were applied to cotton, cotton/polyester, cotton/wool, and cotton/polyester/wool medium-weight twill fabrics. The treatments were applied by either a pad, dry, cure process or a two-step procedure consisting of a pad, dry, cure application of DMDHEU followed by a Thps-NH 3 cure process. Flammability of the treated fabrics was evaluated by a number of tests, including burning rate, vertical char length, oxygen index, and a flame-extinguishment test. Physical properties were determined by standard tests to measure breaking strength, wrinkle recovery, stiffness, durablepress rating and shrinkage due to laundering. Cotton/wool blend fabrics treated with Thps-urea-TM M had the best flame-retardant properties. B

SynopsisMedium weight twill fabrics constructed from cotton and cotton blended with polyester and/or wool were analyzed under nitrogen by three thermoanalytical techniques. Fabrics were tested both before and after treatment with [tetrakis(hydroxymethyl)phosphonium] sulfate (THPS), urea, and trimethylolmelamine. The presence of all fibers was distinguishable in differential scanning calorimetric analysis (DSC) of untreated fabrics; the relative positions of the endothermic, decomposition peak temperatures were only slightly changed. After flame-retardant (FR) treatment, the blended cotton and wool fibers were altered. Both fibers decomposed as exotherms during DSC analysis. These data supported earlier microscopical, X-ray evidence that wool fibers were actually reacting with the FR treatment. The two DSC peaks for polyester polymer melting and decomposing remained unaffected by either blending with other fibers or the presence of the FR finish on the fabric. There was excellent agreement between DSC peak temperatures and the temperature of maximum rate of weight loss obtained from thermogravimetric analysis (TGA). Blending cotton with either of these fibers increased the residue measured after TGA. The increased residue correlated with increased flame resistance as measured by the 45" angle, edge-ignition burning rate test.

Selected Jaw-cost N-methyJol compounds have been incorporated with tetrakis(hydroxymethyljphosphonium hydroxide (THPOH formulations and applied to cotton fabric by a number of different processing' techniques. Nsmcthylo! compounds evaluated in this study were trimethyJolmelaminc, dimcthylolethylcneuren, and dlmethylolmethoxyethyl 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-ens. Even with modest add-ens (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. Usc of trimethylolmc1amine and THPOH with an ammonia cure, followed by a heat cure, produced the most effective flame resistance.