Polypropylene Composites and Hybrid Composites Reinforced With Sugarcane Bagasse Fibers and Nanoclays: Structure–Processing–Properties Relationships

Abstract

ABSTRACT This study investigates the development of environmentally improved hybrid composites by incorporating sugarcane bagasse (SCB) fibers (15 wt.%) and hydrophobic nano‐clay fillers (3 wt.%) into a polypropylene (PP) matrix. Although PP is a petroleum‐based thermoplastic, its widespread availability, recyclability, and compatibility with conventional processing routes make it a suitable matrix for transitional sustainable composite systems. The sustainability of the proposed materials is primarily achieved through the valorization of agro‐industrial waste and the partial replacement of synthetic reinforcements without increasing polymer content. The composites were fabricated via twin‐screw extrusion, a scalable and energy‐efficient processing technique that enables uniform dispersion of multiscale reinforcements. Morphological, structural, and thermal characterizations were subsequently performed. Alkali treatment of SCB fibers was employed to improve fiber–matrix compatibility by removing surface impurities, increasing surface roughness, and enhancing interfacial stiffness. Furthermore, the use of a coupling agent (PP‐g‐MA) promoted strong interfacial adhesion between the bio‐based fibers, nano‐clay fillers, and the PP matrix, contributing to efficient stress transfer and reduced material failure. Thermal analysis revealed a slight increase in the crystallinity index for the hybrid sample, corresponding to an improvement of about 5%, attributed to the nucleating effect of fibers and nanoclays. In terms of mechanical performance, the Young's modulus of injection‐molded hybrid composites reached 2154 MPa compared to 1600 MPa for neat PP, representing an enhancement of nearly 35%. However, it was also observed that the Young's modulus increased from PP‐3D to PP‐M‐S‐3D, corresponding to an improvement of approximately 36%. A slight decrease was then recorded for the hybrid sample, attributed to defects between layers, as shown by the morphological analysis. Furthermore, the incorporation of organo‐modified nanoclays (OMMT) contributed to improved mechanical, thermal stability and structural integrity, suggesting a synergistic reinforcement effect. Overall, these results demonstrate the potential of multiscale PP‐based composites for developing more sustainable materials compatible with both conventional processing and additive manufacturing. The combined use of micro‐ and nano‐fillers improved thermal stability and adhesion. SEM and rheology confirmed good dispersion of fibers and nanoclays in the matrix. Tensile properties of injection‐molded and 3D‐printed samples were compared. Injection molding provided higher mechanical properties than 3D printing.