Effects of wood flour addition and coupling agent content on mechanical properties of recycled polystyrene/wood flour composites

The effect of filler addition and coupling agent content on the mechanical properties and morphology of wood plastic composites was examined. Using wood flour as the reinforcement filler and recycled expanded polystyrene as the thermoplastic matrix polymer, a particle-reinforced composite was prepared using a co-rotating twin-screw extruder. In the sample preparation, four levels of filler loading (10, 20, 30, and 40 wt%) and three levels of coupling agent content (1, 2, and 4 wt%) were used. The influence of particle size and particle morphology was also evaluated. The results showed that short fibers provide a higher specific surface area, enlarging the contact surface area with the polymer matrix. A wood flour loading of more than 20 wt% caused a decrease in the mechanical properties studied. The addition of 2 wt% of coupling agent improved the interfacial adhesion between the polymer matrix and wood flour and increased the flexural and impact strengths of the lignocellulosic composites. Addition of a coupling agent content greater than 2 wt% caused a reduction in the mechanical properties evaluated. A morphological study revealed that the positive effect of coupling agent on the interfacial adhesion of wood flour reinforced the expanded polystyrene composites.