Preparation of a novel bio-based ferric flame retardant for enhancing flame retardancy, mechanical properties, and heat resistance of polylactic acid

A fully bio-based flame retardant PNF was prepared based on phytic acid, nicotinamide and iron salts in aqueous solution by a green and convenient ionic reaction, and then blended with polylactic acid (PLA) to improve its properties. The results demonstrated that the PLA composite containing 4 wt% PNF(PLA/4PNF) had a flame retardancy rating of UL 94 V-0 and an oxygen index of 25.3%. In addition, the peak heat release rate (PHRR) and total heat release (THR) of PLA/4PNF were reduced by 27.0% and 27.7%, respectively, compared to pure PLA, and the flame retardancy index (FRI) was increased by 210%, demonstrating that PNF could effectively improve the flame retardancy of PLA. Moreover, the thermal conductivity of PLA/4PNF increased by 284% compared to pure PLA, making the material require higher heat to reach the combustion state. DSC and mechanical property tests showed that PLA/4PNF had 31.3% higher crystallinity, 5.2% higher heat deflection temperature and 10.0% higher flexural modulus compared to pure PLA, indicating that PNF effectively improved the mechanical properties and heat resistance of PLA. The research in this article broadens the application of bio-based flame-retardant PLA in the field of electronic appliances and office equipment.