Hemp Hurd/ <scp>HDPE</scp> Thermoplastic Biocomposites: Effects of Oxidized Polyethylene and <scp>EPDM</scp> Elastomer on Material Performance

ABSTRACT The biocomposites examined in this study utilize hemp hurd as the lignocellulosic biomass and high‐density polyethylene (HDPE) as the thermoplastic matrix, with a 50 wt.% hurd content. Oxidized polyethylene (OPE) and ethylene–propylene–diene monomer (EPDM) rubber were incorporated at varying concentrations to assess their impacts on biocomposite processability and mechanical properties. The inclusion of OPE as a chemical compatibilizer enhanced interfacial adhesion between the hurd and HDPE; as a result, composites containing OPE exhibited increased tensile strength and modulus relative to unmodified hurd/HDPE composites. For example, the 50/50 hurd/HDPE blend demonstrated an average tensile strength of 11.1 MPa and modulus of 1391 MPa, which increased to 27.1 and 3669 MPa, respectively, when 5% of the HDPE was replaced with OPE. Additionally, the OPE addition improved the melt‐flow behavior of the materials, resulting in lower melt viscosity. Although OPE increased tensile strength and modulus, it reduced the impact resistance and ductility of the biocomposites. To address this, EPDM was incorporated as a rubbery toughening agent into the composite (50/45/05 hurd/HDPE/OPE), with the HDPE phase partially replaced by EPDM at 5 to 20 wt% to enhance ductility and impact resistance. Composites containing optimized amounts of both additives (5% OPE and 15 wt% EPDM) achieved a balanced combination of tensile strength, stiffness, and impact resistance, with values of 13.0 MPa, 1777 MPa, and 42 kJ/m 2 , respectively. In brief, it showed that high‐biomass (50 wt%) hurd/HDPE biocomposites can be transformed into melt‐processable, mechanically robust materials via synergistic OPE compatibilization and EPDM toughening.