Caffeic acid decorated ammonium polyphosphate-based flame retardant for fire safety and anti-aging of wood plastic composites

Wood plastic composites (WPCs) are facing fire hazard and aging when they are used as building materials. In current work, ammonium polyphosphate-based flame retardant decorated with caffeic acid (MAPP-CA) was prepared by the two-step reaction of ammonium polyphosphate (APP), ethylenediamine, and caffeic acid. The chemical structure of MAPP-CA was characterized by different measurements. When the loading amount of MAPP-CA was 25 wt% in WPC, WPC/MAPP-CA 25 sample passed the UL-94 V-0 rating and limited oxygen index (LOI) value reached 26.5%. Compared with WPC, WPC/MAPP-CA 25 showed significantly lower heat release and smoke release. Besides, MAPP-CA improved the anti-aging property of WPC. According to oxidation induction time (OIT) result of WPC, WPC/APP 25 and WPC/MAPP-CA 25 . The OIT of WPC/MAPP-CA 25 is much longer than that of WPC (17.8 min) and WPC/APP 25 (36.8 min), about 7.4 and 3.6 times of the latter two, respectively. Further, the retention ratios of mechanical properties showed that the retention in flexural strength and notched impact strength for WPC/MAPP-CA 25 is superior to that of WPC/APP 25 and WPC after aging at 120 ℃. Flame-retardant and anti-aging mechanisms of MAPP-CA were investigated in detail. This work opens a new route for upgrading traditional flame retardant.