Comparative evaluation of vascular bundle and parenchyma fillers from oil palm trunk in polypropylene wood-plastic composites

This study explores the mechanical properties and water resistance of polypropylene (PP) composites reinforced with oil palm trunk (OPT) components, specifically vascular bundles (VB) and parenchyma cells (PC) particles, at 30 and 60 wt% content levels.The research addresses challenges posed by the inherent variability in density and moisture sensitivity of OPT in composite formulation.Utilizing a hot-pressing technique, we examined the effects of OPT type, filler content, and the addition of a maleic anhydride-grafted polypropylene (MAPP) coupling agent.The findings reveal that VB-and PC-reinforced PP composites show enhanced density, moisture resistance, and overall mechanical performance relative to untreated OPT.Notably, while increasing OPT content improves modulus and density, it negatively impacts tensile and flexural strengths due to poor interfacial bonding.The incorporation of MAPP significantly enhances interfacial adhesion between the PP matrix and OPT fillers, leading to reduced moisture uptake and dimensional swelling, particularly at higher filler loadings.These results highlight the potential of VB and PC as sustainable reinforcement materials for wood-plastic composites (WPC), providing critical insights for optimizing composite designs aimed at improving durability and water resistance.