Study On Aging Properties Of Wood Fiber Reinforced Recycled Polypropylene Composites

To improve the aging properties of wood plastic composites (WPCs), the ultraviolet accelerated thermal aging and hydrothermal aging properties of WPCs were systematically studied through addition of ultraviolet absorbent and antioxidant and interfacial modification in this paper.Wood fibers, recycled polypropylene (RPP) and maleic anhydride grafted polypropylene (MAPP) were firstly mixed with ultraviolet absorbent and antioxidant to fabricate WPCs. The optimum type and amount of ultraviolet absorbent and antioxidant were determined by ultraviolet accelerated thermal aging properties testing. Then the effect of surface modification of wood fibers, weight fraction of compatibilizer, composition of matrix and moisture content of wood fibers on the aging properties of WPCs were analyzed. The surface properties and microstructure of WPCs were characterized and analyzed by infrared spectroscopy and scanning electron microscopy (SEM). The aging mechanism of WPCs was preliminarily explored. The results showed that when both of the weight fraction of ultraviolet absorbent (A2) and antioxidant (B1) were 0.6%, WPCs possessed the optimum aging properties. Coupling treatment (KH550) of wood fibers was the best way to improve the aging properties of WPCs among the three methods of maleic anhydride treatment, silane coupling treatment and titanate coupling treatment. Increasing of compatibilizer content, addition of certain amount of polypropylene (PP) and drying of wood fibers could all result in improvement of the aging properties of WPCs.In the process of hydrothermal aging, the moisture absorption and mechanical properties of WPCs in 1800h were investigated. The results showed that methyl methacrylate treatment, silane coupling treatment and maleic anhydride treatment methods could all lower the moisture absorption of WPCs effectively so that the decreasing range of tensile strength and impact toughness was less than that of the untreated WPCs. With the increasing of the content and length of wood fibers the moisture absorption of WPCs increased while the mechanical properties decreased.