Improvement in the physical and mechanical properties of polyethylene and recycled polypropylene composites reinforced with Musa textilis fiber

The development of composite materials offers a promising strategy for integrating thermoplastic waste into circular economy models. In this context, natural fibers, such as Musa textilis (abaca), are employed to enhance the performance of biomaterials for use in various industrial sectors. This study evaluated the compatibility of M. textilis fiber with two recycled thermoplastics: polyethylene (PE) and polypropylene (PP) in the absence of coupling agents. PE and PP were reinforced with four fiber loadings (0, 10, 20, and 30% v/v), and their physical properties (density, thickness swelling, water absorption, and weight increase), mechanical properties (dynamic modulus of elasticity, modulus of elasticity, flexural stress, and tensile stress), and specific properties (specific elastic modulus and specific tensile stress) were analyzed. In addition, tensile failure modes were examined using scanning electron microscopy (SEM), and the degree of dissimilarity between treatments (polymer × fiber loading) was assessed. Reinforcement with M. textilis improved mechanical performance by 5%–15%, specifically increasing tensile strength, flexural strength, and modulus of elasticity compared to the unreinforced control. The observed increases in tensile and flexural properties suggest potential applicability in selected industrial uses, particularly at fiber loadings of 20–30% v/v. SEM analysis revealed that unreinforced plastics predominantly failed through coarse river-line fracturing, whereas composites with 10–20% v/v fiber content exhibited interfacial voids and fiber pull-out, indicative of limited fiber–matrix adhesion. At 30% v/v fiber loading, the composites exhibited enhanced mechanical integrity and resistance to fracture, although they also demonstrated increased susceptibility to water absorption, highlighting limitations for use in outdoor or high-moisture environments. In conclusion, the incorporation of M. textilis fiber into recycled PE and PP improves the mechanical and functional performance of the resulting biomaterials, supporting their potential use in commercial applications aligned with sustainability goals.