Synergistic reinforcing effect of fly ash and powdered wood chips on the properties of polypropylene hybrid composites

Recent advances in the field of composite materials, aligning them with cost-effectiveness and environmental sustainability, have made the development of materials from industrial waste an attractive area of research. This work introduces an innovative approach for the reuse of globally available industrial waste by hybridizing organic and inorganic by-products to create low-cost composite materials with synergistically enhanced performances. Herein, industrial wastes, namely powdered wood chips (PWC) from the woodworking industry and fly ash (FA) derived from bagasse burning, were incorporated in a thermoplastic polypropylene (PP). Hybrid PP/PWC/FA composites at 70/20/10, 70/15/15 and 70/10/20 wt% were manufactured via extrusion process, followed by injection molding. Micrographic observations and infrared spectroscopy reveal that PWC particles have good physical adherence with PP. In contrast, the hydrophilic nature of FA leads to the creation of gaps at the interface due to the poor interfacial adhesion. The latter difference is reflected in the combined void nucleation modes of particle–fracture and particles–matrix interface decohesion during hybrid composites’ tensile deformation. This provides a good synergistic stiffening effect for 70/20/10 wt% PP/PWC/FA hybrid composite, which offers the highest Young’s modulus improvement of about 44.43%, while benefiting from balanced tensile strength and strain at yield. Furthermore, a two-way ANOVA at a significance level of 5% also proved the significant effect of PWC and FA reinforcement on the tensile parameters, as the p-values were below 0.05. Melt rheological properties demonstrate complex viscosity decrement for hybrid composites, suggesting a reduction in the energy required during production. Overall, the novel, high-performance hybrid composites developed can be manufactured with less energy consumption and are suitable for applications requiring high-temperature resistance and stiffness such as automotive, construction, and beyond.