Simulated Recycling of Polypropylene and Maleated Polypropylene for the Fabrication of Highly-Filled Wood Plastic Composites

Abstract

In this study, polypropylene [PP] and maleic anhydride grafted polypropylene [MAPP] were reprocessed from one to three times to simulate recycling. 30 wt % of the reprocessed PP and MAPP were compounded with 70 wt % wood filler to fabricate highly filled wood plastic composites [WPCs]. The neat and composite samples were produced using a batch mixer and injection molder. The effect of recycling and maleation of PP was analyzed using light scattering, nuclear magnetic resonance, rheology, microscopy, and other physical/mechanical properties. While thermomechanical processing may lead to chain scission reactions, shown by a reduction in melt viscosity and weight-average molecular weight, the observed changes are minor and did not change the bulk properties significantly. The repeated reprocessing allowed for the incorporation of up to 70 wt % wood flour [WF] to fabricate the highly filled WPC while the maleation allowed for better interactions and the composite’s strength. Overall, the WPCs with maleic anhydride displayed appealing physical properties due to their increased tensile properties and a lack of oxidation or significant level of degradation. This indicates that the maleation of reprocessed PP could be an important and effective strategy to reduce virgin and petroleum-based MAPP while revitalizing mechanical properties for WPCs.