Toughening of Wood-plastic Composites Based on Silane/Peroxide Macro Crosslink Poly(propylene) Systems

Abstract

The toughening of wood-plastic composites (WPC) based on silane/ peroxide macro crosslink poly(propylene) (PP) systems was studied. A 23 experimental design was adopted to initially optimize three parameters: silane, wood flour, and talc contents of the WPC formulation. The WPCs were manufactured on a co-rotation twin screw extruder. Test specimens were prepared via injection molding. The WPC compounding formula with 8 phr of silane, 35 phr of wood flour, and 20 phr of talc was used to study the effect of ultra-high molecular weight polyethylene (UHMWPE) as a toughener. The impact strength was improved up to a 10-phr UHMWPE loading. The flexural properties and heat distortion temperature (HDT) slightly decreased. When exceeding 10 phr of UHMWPE, the unmelted UHMWPE agglomerated and the mechanical properties were inferior. The fiber/matrix interfacial adhesion was enhanced by the sauna treatment. A marginal increase in the fracture toughness was observed. The impact strengths increased with the addition of ethylene propylene diene terpolymer (EPDM) as a rubber toughener. However, high EPDM contents caused a decrease in the HDT. The sauna incubation of the EPDM-toughened WPC enhanced the impact strengths. The EPDM effectiveness was determined by the better PP matrix toughness and UHMWPE/PP interfacial adhesion.