Nanostructured Fillers for Tailoring the Mechanical Properties of Polypropylene: Recent Advances and Structure-Property Relationships

Abstract

Polypropylene (PP) is widely used in engineering applications because of its low density, chemical resistance, processability, and favourable cost-to-performance ratio; however, its mechanical performance is often limited by the trade-off between stiffness, strength, ductility, and toughness. Nanostructured fillers provide an effective strategy for modifying these properties through interfacial reinforcement, stress transfer, crystallization control, and microstructural modification. This review examines recent advances in PP nanocomposites containing carbon-based nanostructures, layered nanomaterials, inorganic nanoparticles, bio-based nanostructures, and hybrid filler systems. Particular emphasis is placed on the relationships among nanofiller architecture, dispersion, interfacial adhesion, orientation, processing conditions, crystallization, and mechanical response. The review compares the mechanisms governing tensile strength, modulus, elongation, impact resistance, fracture behaviour, creep, and fatigue, highlighting the frequent trade-off between stiffness enhancement and toughness retention. Hybrid nanofiller systems and interfacial modification are discussed as approaches for achieving more balanced mechanical performance. Processing–structure–property relationships are further considered to identify the factors controlling reproducibility and scale-up. Finally, challenges associated with dispersion, interfacial engineering, standardized mechanical comparison, sustainability, and predictive modelling are discussed, with emphasis on structure-controlled design of PP nanocomposites for application-specific mechanical performance.

Keywords: Polypropylene; Nanocomposites; Nanostructured Fillers; Mechanical Properties; Interfacial Adhesion; Dispersion; Crystallization; Structure–Property Relationships; Hybrid Nanofillers; Toughening