Chemical coupling in wood fiber and polymer composites: A review of coupling agents and treatments

Coupling agents in wood fiber and polymer composites (WFPC) play a very imp ortant role in improving the compatibility and adhesion between polar wood fibers and non-polar polymeric matrices. In this paper, we review coupling agents, pretreatment, and mixing technology for wood fiber and polymer curr ently used in the manufacture of WFPC. So far, over forty coupling agents h ave been used in production and research. These agents are classified as or ganic, inorganic, and organic-inorganic groups, among which organic agents are better than inorganic agents because of stronger interfacial adhesion. The most popular coupling agents currently being used include isocyanates, anhydrides, silanes, and anhydride-modified copolymers. Coupling agents are usually coated on the surface of wood fiber, polymer or both by compoundin g, blending, soaking, spraying, or other methods. Three basic processes sui table for coupling treatment are discussed: directly coating during mixing and fully or partly pretreating before mixing. The pretreatment of wood fib er and polymer by coating or grafting is the preferred method to improve th e mechanical properties of WFPC.(2).