Effects of Recycling Cycles and Coupling Agent on the Properties of Wood Fiber/Polypropylene Composites

Effects of Recycling Cycles and Coupling Agent on the Properties of Wood Fiber/Polypropylene Composites

In this study, various properties (mechanical, thermal, and morphological properties) of wood fiber/polypropylene (WF/PP) composites were evaluated for the core-layer application of coextruded wood plastic composites (WPCs) with and without a coupling agent. The WF/PP composites were fabricated using a twin-screw extruder in the variation of extrusion cycles to mimic recycling cycles. As the number of extrusion cycles increased, the mechanical and thermal properties of the composites decreased and showed minor changes, respectively. The maximum reduction in percentage values for the mechanical properties of the repeatedly extruded WF/PP composites was less than 15%, while the change in thermal properties was negligible. The addition of the coupling agent (i.e., MAPP) affected the mechanical properties (particularly, tensile and flexural strength) and thermal stability of the composites, even when the number of extrusion cycles was increased. Since the composites with 50 wt% WF had good stiffness, when the MAPP was added, the differences in the modulus values of the composites were smaller than those in the strength values. Various thermal property results demonstrated slight reductions as the number of recycling cycles increased, but the differences between 3- and 5-cycle extruded samples were very small. Based on these results, recycled WF/PP composites with coupling agent can be used as viable and sustainable building, furniture and 3D printing materials as well as core-shell coextruded composites having recycled WPC cores regardless of recycling cycles