Analysis of tensile strength and water absorption in recycled HDPE composites reinforced with ijuk fiber at various fiber weight fractions

While natural fiber reinforced polymer composites have emerged as sustainable solutions, most studies focus on virgin HDPE rather than recycled HDPE (rHDPE), with limited research systematically investigating the simultaneous effects of ijuk fiber (Arenga pinnata) loading on both mechanical properties and water absorption behavior. This study aims to analyze the effect of ijuk fiber content on tensile strength and water absorption of rHDPE coeposites to determine the optimal fiber fraction balancing mechanical performance and dimensional stability. Composites with fiber weight fractions of 0%, 10%, 15%, and 20% were fabricated using alkali-treated ijuk fibers, melt blending, and compression molding. Tensile testing (ASTM D638) indicated progressive strength enhancement through effective load transfer mechanisms: 11.52 MPa (0%), 13.91 MPa (10%), 17.80 MPa (15%), and 20.92 MPa (20%), representing an 81.54% improvement at maximum fiber loading. Water absorption (ASTM D570, 24h immersion) increased proportionally from 0.00% to 1.16% due to fiber hydrophilicity and interfacial diffusion pathways created by exposed fiber surfaces from specimen cutting. An optimal balance between mechanical strength and moisture resistance was achieved at 10-15% fiber content. These findings demonstrate that ijuk fiber-reinforced rHDPE composites offer viable sustainable alternatives for non-structural applications in moderate-moisture environments, contributing to waste plastic valorization and circular economy development.