Characterization, Physical and Mechanical Properties of Polypropylene/Wood-Flour Composites

Wood polymer composites (WPCs) were made with pine and polypropylene matrix (PP). Samples of WPCs were processed through melt compounding and hot-press moulding with different formulations of wood flour content and addition of coupling agent. This study focuses on the improvement of the mechanical properties of WPCs through the addition of compatibilizers. Generally fiber/matrix bonding or a strong interaction is required to ensure an appropriate transfer of stresses and satisfactorily physical properties. The effect of wood content and coupling agent like Maleic anhydride grafted polypropylene (MAPP) on the thermal behavior was monitored by DSC, water uptake and thickness of swelling during 2 months. The results exhibited increase of these two physical properties with wood flour content and coupling agent. In the thermal behavior, wood plays the role of nucleating agent. During the cooling step, the crystallization begins earlier than in pure PP and the percent of crystallization increase with wood amount. The effects of the reinforcements on the mechanical properties of the composites as well as the effect of compatibilization on the composite properties were highlighted. The mechanical study revealed the positive effect of coupling agent MAPP on interfacial bonding permitting better stress transfer from matrix to fiber.