Hierarchical Enhancement Of Stress-Strain Transfer And Flame Retardancy Of Wood Plastic Composite

Mechanical strength of multiphase material depends on mechanical properties of components and interface bonding states, which has always been a research hot spot. In this work, a hyperbranched polyethyleneimine-grafted nano SiO2 (pSiO(2))-decorated ammonium polyphosphate (APP) was applied to synergistically improve the flame retardancy and toughness of wood plastic composite (WPC). With nonpolar carbon skeleton and polar amine groups on it, pSiO(2) could successfully coated on APP via ionic bonding and improve the compatibility between wood fiber and high-density polyethylene (HDPE). According to digital image correlation (DIC), pSiO2 improved the strain transfer from HDPE molecular to wood fiber, thus an increased high-deformation region was observed in WPC/pSiO(2) and WPC/APP-pSiO(2) . pSiO(2) provided numerous of stress concentration area,to induce the formation and inhibit the convergence of craze. As a result, WPC/APP with 30% pSiO(2) addition showed a 47.9% increment in impact strength compared to WPC/APP. Besides, pSiO(2) also showed a synergistic effect with APP and further improved the flame retardancy of flame retardant WPC. This work provides a route for interface design and internal stress-strain study of multiphase composites.