A review of coextruded wood–plastic composites

Abstract Wood–plastic composites (WPCs) are increasingly broadly applied composites that combine the merits of wood and plastics, such as the renewable, degradable, lightweight, and low‐cost characteristics of wood, and the thermoplasticity, hydrophobicity, and toughness of plastics. However, WPCs also display the disadvantages of the two main components including hydrophilicity and flammability of wood, and weathering degradability, flammability, and thermal expansion of plastics. Coextruded WPCs (Co‐WPCs) are multilayer composites in which regular WPCs are coated with a protective shell layer through coextrusion. The core–shell structure of Co‐WPCs provides a way to overcome the shortcomings of WPCs by modifications specific to the composite surfaces. This review summarizes the studies of Co‐WPCs in terms of their mechanical properties, moisture absorption, weathering, flame resistance, and dimensional stability. It also presents expectations for the further development of Co‐WPCs.