3 - Interactions between wood and synthetic polymers

Abstract

This chapter describes that the structure and properties of the wood fiber-polymer matrix interphase play a major role in determining the mechanical and physical properties of the composite material. The interphase or adhesion between the fiber and the matrix has little effect on the composite stiffness. However, the adhesion and interphase play a very important role in determining the properties. Adhesion can be improved by using coupling agents or compatibilizers. The fiber surfaces can vary greatly, which results in varying interaction with the polymer matrix. The regions of both low and high surface energy may exist on the same fiber; some sites may be inert, while others provide sites for specific interactions with polymer molecules. The surface of the fiber may be smooth or rough and fiber modifications may further enhance the surface area. The fiber-matrix interface and the interphase are important factors in determining a variety of properties of Wood-Plastic Composite (WPC) and therefore, should be considered when developing WPCs for any application. In WPC, there have been several techniques used to modify the surface/interface/interphase. From data available in literature, the most effective method is to covalently bond the coupling agent to the fiber surface and then have a strong interaction or covalent bonding to the bulk matrix. Covalent bonding and polymer entanglements provide stronger bonds as compared with secondary adhesive mechanisms. The type of interaction between the coupling agent and the matrix depends on the type of adhesive bonding possible.