Assessing the biomass loading on mechanical and physical properties of composite material of used plastic syringes and treated beans husks

This research studied the potential of utilizing waste medical polypropylene (wmPP) and alkali-treated bean husk (TBH) of two particle sizes (150 µm and 300 µm) to fabricate polymer composites at different filler loadings (5%–25%). Compounding and compression molding techniques were used to produce eleven samples, including a control sample of 100% wmPP and composites with varying TBH filler contents. The study investigated both physical and mechanical properties of the composites. For mechanical properties, tensile and flexural test were carried out, for tensile properties, the highest tensile strength was obtained at 15% TBH loading with 150 µm particles (20.017 MPa), while tensile modulus peaked at 5% TBH loading with 300 µm particles (2.039 MPa). Elongation at break decreased with increasing filler content due to stiffening of the matrix, though a slight improvement was observed at 15% TBH with 150 µm particles as a result of better particle dispersion. Flexural properties revealed that pure wmPP exhibited the highest flexural strength (37.19 MPa). Moderate filler additions improved flexural modulus, peaking at 10% TBH (725.067 MPa), but higher filler loadings reduced both strength and modulus due to particle agglomeration and weak interfacial bonding. For physical properties, density decreased progressively with filler addition and larger particle sizes, ranging from 1.299 g/cm³ for pure wPP to 0.656 g/cm³ at 25% TBH (300 µm). Water absorption increased with higher filler loading and was greater in composites with smaller particles (150 µm) due to their higher surface area and hydrophilic nature. The study validates that treated bean husk is an effective and sustainable reinforcement material. Optimal properties were achieved at moderate filler loadings, demonstrating its potential for lightweight, eco-friendly composite applications.