In-situ fabrication of a sustainable, synergistic and durable flame-retardant coating for phytic acid modified silk fabric

• Highly sticky functional coating is in-situ fabricated on silk surface. • The functional coating is grafted on silk surface through covalent reaction. • The functional coating has high flame retardancy and thermal stability on silk textile. • The functional coating pyrolyzes through intumescent charring mechanism. • The functional coating offers an effective and durable strategy to minimize fire hazards of silk textile. The novel strategies for fabricating durable flame retardant (FR) silk fabric with biomass phytic acid (PA) is of interest. In this study, a highly sticky coating was in-situ developed on the surface of silk fabric by adsorption of PA, 1,4-Phthalaldehyde and followed by adsorption of 3-aminopropyltriethoxysilane (KH550). The Schiff base reaction would occur between 1,4-Phthalaldehyde and silk fiber/KH550, and thus the sticky coating could be firmly grafted on silk surface. The thermal degradation, smoke and heat emission properties, flame retardancy, and washing durability of coated silk were explored. The FR coating displayed high functional efficiency and thermal stability by taking advantage of synergistic effect with phosphate groups and silica networks. The modified silk fabrics also possessed lower fire hazards as suggested by significantly reduced smoke and heat generation. The coated silk fabrics self-extinguished and obtained a char length of 13.5 cm after 20 washing cycles. The improved washing resistance should be ascribed to the covalently grafted sticky coating on silk surface. In general, this work reports a novel and feasible strategy to develop durable silk textile using bioderived PA.