Enhanced Mechanical and Thermal Performance of Injection-Molded HDPE Nanocomposites via Low-Content Reduced Graphene Oxide Reinforcement

High-density polyethylene (HDPE) is extensively employed owing to its affordability, chemical resistance, and ease of manufacturing; however, its relatively limited mechanical and thermal properties restrict its use in advanced structural applications. In this study, HDPE was reinforced with reduced graphene oxide (rGO) to develop lightweight nanocomposites with improved multifunctional properties. HDPE/rGO nanocomposites containing 0.25, 0.5, 0.75, and 1 wt.% rGO were fabricated via twin-screw melt compounding followed by injection molding. The influence of rGO loading on thermal, mechanical, structural, and morphological behavior was systematically investigated. Tensile results revealed a maximum strength improvement of 34.4% at 0.25 wt.% rGO, while enhanced ductility was observed at 0.75 wt.% rGO. Differential scanning calorimetry indicated a progressive increase in melting temperature, indicating that rGO influences the melting behavior of HDPE. Thermogravimetric analysis demonstrated improved thermal stability due to the barrier effect of rGO nanosheets. SEM observations suggest a relatively uniform dispersion of rGO nanosheets together with good interfacial interactions at optimal loadings. Overall, the results demonstrate that the optimum filler content depends on the property of interest, with 0.25 wt.% maximizing tensile strength and 0.75 wt.% improving ductility, demonstrating the potential of HDPE/rGO nanocomposites for lightweight structural and engineering applications.