Facile preparation of a sustainable and reactive flame retardant for silk fabric using plant extracts

• Phytic acid and tartaric acid are derived from resourceful plants or crops. • Tartaric acid phytate ester (TAPE) is a reactive flame retardant. • TAPE could react with silk fiber to form ester and amide covalent bonds. • TAPE shows high flame retardant efficiency and durability on silk fabric . • TAPE offers a sustainable and durable strategy to minimize the fire hazards of silk textiles. The development of effective and reactive flame retardant (FR) using natural products is of interest for sustainable FR textiles. This study focused on the synthesis of a reactive phosphorus-based FR agent (tartaric acid phytate ester (TAPE)) using plant-derived phytic acid and tartaric acid. We further studied its potential applications in durable FR modification of silk fabric. The chemical structure of TAPE and its potential bonding mechanism with silk fibers were explored. The thermal stability, smoke and heat generation performance, and flame retardancy of the modified silk fabrics were investigated. Char residue analyses were also performed to study the FR mechanism of TAPE on silk fabric. The results revealed that TAPE imparted higher thermal and flame resistance to silk and remarkably inhibited the smoke and heat generation of silk through a condensed charring mechanism. The introduction of TAPE to silk was driven by ester and amide covalent bonds and electrostatic attraction. This leads to good washing durability of the modified silk as reflected by the self-extinguishing action of modified silk after 20 washing cycles. In general, this research provides a novel strategy to develop a reactive FR agent as well as sustainable and durable FR functional silk textiles using bio-based plant extracts.