Investigating the effect of isocyanate modification of wood fiber on the physical-mechanical properties and torque rheometry of wood- polyethylene composite

Wood plastic composites are ideal in many applications such as furniture, components and automotive industry. However, most polymers especially thermoplastics are non-polar (hydrophobic) substances which are not compatible with polar (hydrophilic) wood fibers. This results in a poor adhesion between polymers and wood fiber. The aim of this study is to improve the adhesion properties by chemically modifying the wood fiber surface to enhance its miscibility within the plastic matrix. This was achieved by using toluene diisocyanate (TDI) linker to couple the wood fiber with either cetyl alcohol to form core-shell like structures. To investigate the effect of modification, composites containing 30% wt of wood was prepared. The effect of modification in three levels (0%, 10% and 20%) was studied on physical-mechanical properties of WPC such as: tensile properties and water absorption. Torque rheometry diagram and Scanning electron microscopy (SEM) were studied. The data showed an increase in the modulus, strength, yield stress and a decrease in the water absorption with increase of wood fiber modification while there is no considerable change in the elongation-at-yield. SEM spectra showed that the modification improve the interfacial adhesion between two phases in WPC.