Enhanced mechanical and thermal properties of green PP composites reinforced with bio-hybrid fibers and agro-waste fillers

Abstract The present work discusses the mechanical and thermal properties of novel green hybrid composites manufactured from a polypropylene (PP) matrix, reinforced by bio-hybrid fibers-short woven flax fiber (SWF) and short basalt fiber (BF)-and agro-waste fillers, such as rice husk powder (RHP). Interfacial bonding was enhanced by a coupling agent, such as maleic anhydride grafted polypropylene (MAPP). These hybrid composites were prepared using the twin-screw extrusion and injection molding process. Extensive tests were conducted to study the effects of reinforcement and MAPP on tensile strength, flexural strength, tensile modulus, flexural modulus, and dynamic mechanical properties. The obtained results showed a large improvement in mechanical properties: tensile strength improved up to 57.68% (from 35.82 to 56.48 MPa), flexural strength improved up to 52.59% (from 58.08 to 88.65 MPa), the value of tensile modulus improved up to 147% (from 2.00 to 4.94 GPa), and flexural modulus improved up to 86.04% from 2.65 to 4.93 GPa—in comparison to a plain 25% SWF/PP composite. DMA represented that the storage modulus increased by 129% from 2159.69 to 4938.20 MPa, while tan delta values reduced by 15%, signifying enhanced stiffness in concert with a reduction in molecular mobility. Thermal analysis exhibited enhanced thermal stability as char residue was increased from 1.82 to 16.81% at 700 °C in the optimum composites containing RHP and MAPP. These morphological and structural characteristics were characterized by using techniques from FTIR and 3D-OM to SEM–EDS; indeed, the enhanced interfacial bonding and homogeneous distribution of reinforcement were verified with MAPP assistance. The findings of this study demonstrate the potential of these green composites for high-performance applications in the automotive and construction industries.