Polypropylene-Based Hybrid Composites: Interplay of Elastomeric Toughening, Mineral Reinforcement and Structure–Property Relationships

Abstract

Polypropylene (PP) is widely used in engineering applications because of its low density, chemical resistance, processability, and favourable mechanical properties; however, its stiffness–toughness balance often limits performance in demanding applications. Hybrid modification through the incorporation of elastomeric toughening agents and mineral fillers provides an effective approach to tailoring this balance. This review examines PP-based hybrid composites containing elastomers, particularly polyolefin elastomer (POE) and propylene-based elastomers, together with mineral fillers such as talc, calcium carbonate, and mica. Emphasis is placed on the relationships among composition, phase morphology, filler dispersion, polymer–filler interactions, crystallization, processing, and mechanical and thermal performance. The effects of elastomer content and mineral-filler type and loading on stiffness, tensile strength, flexural behaviour, impact resistance, hardness, thermal stability, and dimensional stability are critically discussed. Particular attention is given to the competing and synergistic effects arising in ternary PP/elastomer/mineral systems. The review highlights the importance of controlling multiphase morphology and interfacial interactions to achieve an optimized stiffness–toughness balance and identifies key research directions for structure-based design of high-performance PP hybrid composites.

Keywords: Polypropylene; Hybrid composites; Elastomeric toughening; Polyolefin elastomer; Mineral fillers; Talc; Calcium carbonate; Mica; Structure–property relationships; Stiffness–toughness balance.