Properties comparison of coextruded and un‐coextruded wood plastic composites under high temperature accelerated water uptake

Abstract Wood plastic composite (WPC) has been widely used in many fields in recent years. However, the entry of water can destroy the interfacial adhesion between wood fibers and plastic matrix, eventually decreasing the properties of WPC. In order to solve a series of problems caused by absorbing water, we manufactured coextruded WPC which includes a shell layer and a core layer by coextrusion technology. Then many coextruded and un‐coextruded WPCs samples of the same size were conducted in 60°C water to accelerate the process of water absorption (WA), which were taken out at regular intervals for testing. WA, dimension stability, and flexural properties of two types of WPC were measured, respectively. The results showed that the WA of coextruded WPC (1.99%) was significantly lower than that of un‐coextruded WPC (6.02%) in 60°C water after 192 hours. It also indicated much better dimension stability of coextruded composites because of the restriction of the shell layer. The retention values of flexural properties of coextruded WPC after soaking 192 hours (flexural strength: 25.22 MPa; flexural modulus: 4.00 GPa) are much higher than those of un‐coextruded WPC (flexural strength: 21.43 MPa; flexural modulus: 2.90 GPa). Therefore, coextruded WPC has more prominent properties advantages compared with un‐coextruded WPC in a high temperature and high humidity environment.