Optimizing the water absorption behaviour and natural weathering resistance of compatibilized ironwood-based recycled polypropylene composites

Abstract

This study focused on the optimization of material resistance of wood-plastic composite (WPC) made using recycled polypropylene and industrial ironwood residues toward water and natural weathering exposure. The Taguchi method was employed to optimize the WPC composition and manufacturing process parameters based on the L9 orthogonal array experimental design. The WPC specimens were prepared using two-step of extrusion compounding and compression moulding. As input process parameters, ironwood content, coupling agent content, moulding temperature, and pressure holding time have been taken into consideration. The results were then optimized to get the maximum tensile properties of strength and modulus of elasticity as well as minimum water-weight gain and discolouration area after exposure to water immersion and natural weathering. The grey relational analysis (GRA) was carried out to identify the most significant factors and optimal levels that work synergistically to produce enhanced results. For optimizing the performance after water uptake, the ironwood content and moulding temperature are the most significant parameters with percentage contributions of 48.71% and 43.16%, respectively. Meanwhile, the multi-objective optimization technique of GRA obtains that ironwood content is the most significant factor for optimizing the mechanical and physical performance of the WPC after exposure to natural weathering with a percentage contribution of about 71%. Considering the good resistance of the material toward environmental exposure, this study opens up a pathway to effectively utilize ironwood and recycled polymer waste as a sustainable composite material in outdoor applications.