Comparison of Properties of Wood-Plastic Composites Based on Alternate Degradation in Seawater and Acid Rain

Abstract

To investigate the change of the service performance of wood-plastic composites degraded by sea water and acid rain, three types of wood-plastic composite materials were prepared with sorghum straw reinforced with high-density polyethylene (SS/HDPE), polypropylene (SS/PP), and polyvinyl chloride (SS/PVC). Under the extreme alternate degradation conditions simulated by seawater (salinity 3.5%, temperature 55 °C) and acid rain (pH 2.5, temperature 55 °C), the effects on the mechanical and wear properties and the chemical structures of the composites were determined. The exposure to the alternate sea water and acid rain deteriorated the fiber/matrix bonding quality of the composites; the mechanical and wear properties decreased accordingly. Before and after degradation, the three composites were sorted in descending order of the mechanical and wear properties as follows: SS/PVC composites > SS/PP composites > SS/HDPE composites. Sorghum straw /PVC had the best resistance to degradation and sorghum straw /HDPE composite had the least resistance. The matrix molecular chains of the SS/HDPE under the conditions of exposure were broken after 12 days.