A lava-inspired design strategy based on combustion characteristics of PFRP for excellent flame retardancy via dual action mechanism at wide temperature range

Although plant fiber reinforced composite (PFRP) with environmental-friendly and biodegradable matches with society development requirements and carbon neutral strategy, the inherent flammability limits application in the engineering field, especially in rail transit and aerospace with strict fire standards. In this work, based on combustion behaviors of PFRP, the flame-retardant strategy inspired by the characteristics of volcanic lava in nature which could flow along rock crevices or valleys and form dense ceramic protective layer with outstanding heat insulation on the surface after cooling is designed. Compared with neat PFRP, the LOI of the PFRP/APP@PTNi20-GP10 (7.7 wt% FR contents) reaches 35.8%, and UL-94 achieves V-0, showing excellent self-extinguishing performance. Meanwhile, the peak heat release rate (PHRR), total heat release (THR), total smoke release (TSR) and CO production (COP) decrease by 70.1% and 51.7%, 60.3% and 65.5% respectively. More importantly, the char layer formed after the combustion process retains excellent strength and compactness, which provides better protection for the undecomposed composite. Furthermore, the release of toxic volatiles including aromatic compounds, esters and carbonyl compounds in gas-phase pyrolysis products decrease significantly. The mechanism of lava-inspired flame-retardant system can be attributed to the dual action mechanism where different components play corresponding flame-retardant role under wide temperature range. And it is noted that the designed strategy endows PFRP with excellent fire resistance without deteriorating mechanical properties. This work provides a novel design idea for realizing the flame retardancy of PFRP and broadens the application field of PFRP.