Improved processability and high fire safety of wood plastic composites via assembling reversible imine crosslinking network

[Display omitted] •A temperature-responded flame retardant is designed via in-situ Schiff reaction.•Reversible imine crosslinking network endows WPC with flexible processability.•WPC shows the excellent mechanical strength and flame retardancy simultaneously. Wood plastic composites (WPCs) are considered as the next-generation construction and decorative materials because of their mechanical stability and eco-friendliness. The manufacture of high-performance multifunctional WPCs with improved processability is, however, significantly challenging. In this study, we designed a temperature-responsive flame-retardant WPC consisting of a reversible imine crosslinking network. The reversibility of the imine crosslinking network allowed the formation of a loosely crosslinked network during the melt‐processing of the material (170 °C, 100 Hz), resulting in improved processability, with a low melt viscosity of 1.7 kPa‧s and a short stress relaxation time of 1.16 min. Meanwhile, upon cooling, the imine crosslinking network is reconstructed, imparting the flame-retardant WPC with outstanding stress/strain transfer and mechanical properties. More importantly, the unique imine-based crosslinking network accelerates the catalytic charring effect of the WPC, leading to remarkable improvements in terms of the restriction of heat transfer and inhibition of flammable gases, easy achievement of the UL-94 V-0 rating, and effective inhibition of the peak heat release rate (57.3%) and total smoke production (28.5%). Considering the simultaneous improvements in the processability, mechanical properties, and fire resistance of the WPC, this strategy of reversible crosslinking network may open up new opportunities in the development of innovative fibre-reinforced composites.