Enhancing Mechanical and Morphological Performance of Recycled Polypropylene Bamboo Fiber Composites Using Palm Stearin Biohybrid Resin

Plastic pollution has become a critical global concern, with poly(propylene) (PP) being a major contributor to solid waste. Recycling PP (rPP) is a viable strategy to mitigate this issue; however, the material often suffers from degradation and reduced mechanical performance. To overcome these limitations, natural fibers and bio-based additives can be incorporated to improve reinforcement and compatibility. In this study, bamboo fiber (BF) and palm stearin biohybrid resin (PS) were introduced into rPP composites to evaluate their influence on mechanical and morphological properties. Composite specimens were prepared by drying, dispersion mixing, and hot pressing, followed by tensile, flexural, and impact testing. Morphological features were examined using scanning electron microscopy (SEM). Results revealed that untreated BF reduced tensile (4.37 MPa) and impact strength (6.88 kJ/m²) compared to neat rPP (6.1 MPa and 13.11 kJ/m², respectively). In contrast, the incorporation of treated BF with PS enhanced tensile strength (6.45 MPa, + 5.77%) and impact strength (16.52 kJ/m², + 26.02%). Although flexural strength (36.52 MPa) was lower than neat rPP (42.03 MPa), it remained within acceptable limits for structural applications. SEM analysis confirmed improved fiber dispersion and interfacial adhesion in treated BF–PS composites compared to untreated counterparts. These findings demonstrate that palm stearin biohybrid resin, in combination with treated bamboo fiber, offers a promising pathway to develop sustainable, high-performance rPP-based composites for applications such as eco-friendly pallet production.