An eco-friendly and intumescent P/N/S-containing flame retardant coating for polyamide 6 fabric

This study focused on the construction of an eco-friendly and intumescent flame retardant (FR) coating for polyamide 6 (PA6) fabric. The intumescent FR coating, consisting of phytic acid, pentaerythritol and thiourea, was deposited onto PA6 fabric through dip-coating technique. The FR performance, anti-dripping ability, thermal stability, combustion behavior and mechanical property of the coated PA6 fabrics were explored. The severe dripping of coated PA6 fabric was totally eliminated, achieving an excellent FR performance at a low P (2.2%) and S (3.4%) content. Correspondingly, the LOI increased to 28.8% versus 23.2% of pristine one, displaying good flame retardancy. The char residue analyses confirmed the intumescent FR behavior of coated PA6 fabrics. The intumescent char layer played a major role in isolating the exchange of combustibles, oxygen and heat, leading to the significant reduction in heat release performance. The results of cone calorimetry test showed that the peak heat release rate and average effective heat of combustion of coated PA6 fabric decreased by about 36.5% and 34.4%, respectively versus pristine one. Meanwhile, the sulfur-based gases captured free radicals to interrupt the continuous combustion, leading to the significantly improved flame retardancy. Furthermore, the FR coating exerted little influence on the mechanical performance of PA6 fabric.