Study on Water Resistance of Polypropylene Based Wood-Plastic Composites Used in Building

This research was aimed at studying the preparation of polypropylene based wood plastic composite material by twin-screw extrusion. The effects of the addition of the maleic anhydride (MAH) and wood flour on WPC properties were evaluated. WPC with 4, 5, 6, 7, 8, 9, 10 wt% of MAH contents were prepared. The mechanical properties and water resistance of WPC were studied. The result showed that with the increasing of MAH, the tensile strength of WPC increases at first and then decrease, and water absorption reduced by 39%. After immersing in water for 24 h, the tensile strength of WPC decreases but the impact strength increases, and with the increasing of MAH, the reducing extent of tensile strength increases, but the improvement extent of impact strength gradually decreases. When the MAH content exceeds 8 wt%, the impact strength of dried WPC samples (dried for 24 h) can be recovered basically. WPC with 10, 20, 30, 40 wt% of wood flour contents were prepared. The result showed that with the increasing of wood flour, the tensile strength of WPC increases at first and then decreases, the impact strength decreases, and water absorption increased by 62%. When the wood flour content exceeds 10 wt%, the impact strength of dried WPC samples can only recover partially. WPC containing different wood meal sizes was prepared. The result showed that with the decreasing of wood flour particle size, the water absorption of WPC increases obviously. The impact strength of dried WPC samples is higher than that of unsoaked WPC, when the particle size of wood flour is 60 meshes. It can be seen from the SEM photos that the distance between the wood powder fibers becomes larger after 24 h of WPC soaking in water. The finer the wood flour, the easier it is to aggregate in WPC.