Tailoring Interfacial, Rheological, and Energy Absorption Properties of In Situ Nanofibrillated Ethylene Propylene Diene Monomer Rubber for Enhanced Toughness in Polypropylene Composites

Abstract

Enhancing the mechanical performance of polymer composites is crucial for extending their service life and reducing waste. In situ fibrillation has emerged as an effective strategy for toughening rubber-modified thermoplastics. This study presents a simple yet versatile approach to further improve the toughening efficiency of in situ fibrillated rubber, focusing on polypropylene (PP) and ethylene-propylene-diene monomer (EPDM) composites. The strategy involves two steps: first, blending two EPDM grades with different viscosities in various ratios, and second, incorporating this EPDM mixture into a PP matrix, where in situ fibrillation forms nanofibrillar domains. By tuning the EPDM ratio, we control its interfacial affinity with PP, rheological behavior, and intrinsic energy absorption, producing nanofibrils ranging from ∼250 nm to <50 nm in diameter. The morphology, rheology, crystallization, and mechanical properties of the composites were investigated, revealing that an EPDM phase with equal parts of both grades achieved optimal toughening─enhancing elongation at break by ∼400% at −10 °C, ∼250% at room temperature, and impact toughness by ∼200%. This approach provides a systematic framework for optimizing in situ fibrillated rubbers, enabling more effective design of high-performance toughened thermoplastics.