Investigation on the Recycling and Reinforcement Mechanism of Waste Plastics Modified with High-Activity Rice Husk Ash

To address the prominent drawbacks including massive raw material consumption and high carbon emissions associated with virgin plastic manufacturing, as well as the low utilization efficiency of waste plastics and rice husk agricultural residues, in this study, waste plastic was regenerated using high-activity rice-husk ash (HRHA) as the reinforcing phase. Orthogonal experiments were initially conducted to investigate the influence of liquid-solid (L/S) ratio of RHA acid activation, HRHA content, and interfacial compatibilizer dosage on the tensile strength, flexural strength, melt flow index and heat deflection temperature of recycled plastics, thereby optimizing the material parameters. Subsequently, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) technologies were employed to characterize the thermorheological properties and micromorphology of the developed recycled composites, further revealing the mechanical growth mechanism. The results show that the optimal material ratio is achieved at an L/S ratio of 6.36, HRHA content of 0.32 and interfacial compatibilizer dosage of 0.04. Under this condition, the developed RHDPE attains a tensile strength of 52.7 MPa, flexural strength of 34.5 MPa, heat deflection temperature of 76.5 °C and melt flow index of 1.24 g/10 min. HRHA serves as the dominant reinforcing filler and heterogeneous nucleating site, which reconstructs the defective microstructure of waste HDPE, establishes favourable interface bonding between the filler and plastic matrix, and restricts the mobility of polymer chains, thereby endowing the recycled HDPE with superior mechanical and thermal properties. This research establishes a high-value reutilization strategy for performance enhancement of waste HDPE, while providing theoretical and experimental insights for corrosion-resistant and weather-resistant functional coating materials.