Enhanced Mechanical Performance of Silica-Filled NR/HDPE Composites via Electron Beam Irradiation

Thermoplastic elastomers (TPEs) are increasingly explored for structural and energy-related engineering applications due to their recyclability and processing versatility. However, their mechanical limitations restrict wider utilization in high-performance environments. This study examines the combined effects of silica reinforcement and electron beam (EB) irradiation on the mechanical, structural, and morphological properties of natural rubber/high-density polyethylene (NR/HDPE) composites. NR and HDPE were melt-blended with silica loadings of 2 and 10 phr, followed by compounding and subsequent EB irradiation at 50 and 100 kGy. Results show that silica significantly enhances tensile strength, from 5.25 MPa (0 phr) to 18.53 MPa (2 phr) and 25.65 MPa (10 phr), while EB irradiation further increases tensile performance by up to 87.2% at 2 phr and 77.5% at 10 phr. Fourier transform infrared spectroscopy (FTIR) analysis confirms the presence of Si-O-Si and Si-OH bonding structures, while scanning electron microscopic (SEM) observations reveal a transition from ductile to brittle fracture morphology with increasing irradiation, indicating higher crosslink density. The findings demonstrate that silica-polymer interactions, combined with EB-induced crosslinking, provide an effective pathway for producing stronger and more durable NR/HDPE-based TPEs suitable for engineering applications requiring improved mechanical integrity and long-term performance. These results highlight the synergistic role of silica loading and EB irradiation in tailoring the stiffness and deformation behavior of NR/HDPE composites for demanding engineering applications.