Polypropylene Hybrid Composites Reinforced With Glass and Sisal Fibers

Polypropylene (PP) composites reinforced with sisal fiber, glass fiber, and hybrid sisal/glass systems were produced by twin‐screw extrusion followed by injection molding to evaluate the combined effects of fiber type and content on mechanical, thermal, dynamic mechanical, rheological, and morphological properties. Composites containing 10 and 20 wt% fibers were analyzed and compared with neat PP. Glass‐fiber‐reinforced composites exhibited the highest strength and stiffness, while sisal fiber promoted moderate mechanical improvements accompanied by increased porosity. Hybrid composites displayed intermediate tensile strength but a remarkable increase in elastic modulus, indicating stiffness‐driven synergistic effects. Density and porosity analyses demonstrated that pore formation was mainly associated with sisal fiber, whereas glass fiber promoted denser microstructures. Thermogravimetric analysis showed slightly reduced thermal stability for sisal‐containing composites, while glass fiber and hybrid systems maintained degradation temperatures close to neat PP. Dynamic mechanical analysis confirmed fiber reinforcement through increased storage modulus, reduced damping, and improved reinforcement effectiveness. Rheological measurements revealed pronounced shear‐thinning behavior and increased complex viscosity and viscoelastic moduli at low frequencies, reflecting restricted chain mobility and structured melt networks. Morphological analysis supported these results. Overall, sisal/glass hybridization represents an effective strategy to balance stiffness, density, and thermal stability, enabling lightweight, cost‐effective PP‐based composite development applications.