Heat release properties and flammability of the nylon/cotton blend fabric treated with a crosslinkable organophosphorus flame retardant system

• We investigated the nylon/cotton blend fabrics used for military protective uniforms.
• We discovered the interaction between cotton and nylon during the nylon/cotton blend decomposition process.
• The data showed that the flammability of nylon/cotton blend fabric was lower than that of cotton and nylon as single-fiber fabric.

Flame retardant nylon/cotton blend fabrics are widely used in the fields of industrial and military protective uniforms. In this research, we investigate the heat release properties and flammability of the 50/50 nylon/cotton blend fabric treated with a self-crosslinkable durable organophosphorus flame retardant system. For the nylon/cotton blend fabric without treatment, the blend has lower total heat release and higher percent char yield than the arithmetic sum of those of cotton and nylon as single fibers. In addition, both the peak heat release rate (PHHR) and the temperature at peak heat release (TPHRR) for cotton increases whereas both PHRR and TPHRR decrease for nylon when those two fibers are blended to form a fabric. Thus, the data indicated that interaction takes place between cotton and nylon during the decomposition process of the blend. The presence of the organophosphorus flame retardant system reduces PHRR, TPHRR and increase char formation for both cotton and nylon as single fibers. When the cotton and nylon are blended and then treated with the flame retardant, the PHRR of the blend becomes even lower and the percent char yield of the blend becomes even higher than those of the treated cotton and nylon as single-fiber fabric. The char length for the treated blend decreases compared with that of the treated cotton and nylon as single-fiber fabrics. We conclude that cotton and nylon interact with each other during the degradation process of the treated nylon/cotton blend fabric and such interaction reduces the flammability of the blend fabric.