Ultra-high flame retardant starch/wood fiber composites based on the synergistic effect of ammonium polyphosphate and calcium carbonate.

The development of bio-based composites and products from natural biomass offers a viable solution to the resource and environmental issues caused by non-renewable petrochemical feedstocks. Nevertheless, the high carbon content inherent in biomass renders bio-based materials highly flammable, thereby increasing their susceptibility to fire hazards and limiting their potential applications. In this study, flame retardant starch/wood fiber composites (SWA) were developed, utilizing starch as the matrix, wood fiber as the reinforcing phase, ammonium polyphosphate (APP) as the flame retardant, and calcium carbonate (CaCO) as both an inorganic filler and a flame retardant synergist. The SWA composites incorporating 5 % (SWA-5) and 10 % (SWA-10) APP achieved UL-94 V-0 rating, with limiting oxygen index (LOI) of 41.5 % and 57.8 %, respectively. Compared to the control group, SWA-10 exhibited significantly reduced heat release and smoke emission rates, with total heat release (THR) and total smoke production (TSP) reduced by 50.4 % and 72 %, respectively. Additionally, SWA-5 exhibited excellent mechanical properties and outstanding thermal insulation, while SWA-10 showed remarkable biodegradability. Therefore, this work developed ultra-high flame retardant bio-based composites with excellent overall performance, making them suitable for thermal insulation and green building applications.