Composition–Structure–Property Relationships in Natural Rubber/Ethylene–Vinyl Acetate Blend Foams: Associations Among Atomistic Descriptors, Cellular Morphology, and Abrasive Wear

ABSTRACT

Natural rubber (NR)/ethylene–vinyl acetate (EVA) blend foams containing 15, 18, 20, 22, or 25 parts EVA per 100 parts total polymer were examined using molecular dynamics (MD) simulations and experiments. The simulations compared elastic moduli, cohesive energy density (CED), mean‐square displacement (MSD), and fractional free volume (FFV). The experiments measured cure parameters, expansion ratio, cellular morphology, tensile properties, hardness, and dry‐sand abrasion. The expansion ratio increased from 1.025 to 1.144 with EVA content. In contrast, the 20‐part formulation had the highest tensile strength (7.90 MPa) and elongation at break (160.90%) and the lowest volumetric wear rate (5.75 × 10 ⁻⁵  mm ³  N ⁻¹  m ⁻¹ ). In the single scanning electron microscopy (SEM) field analyzed for each formulation, the 20‐part sample had the lowest observed cell‐size coefficient of variation (24.2%). The same composition had the highest CED and relative atomistic moduli and the lowest MSD and FFV among the modeled cells. Together, these composition‐dependent trends support an association among segmental packing, cellular morphology, and measured properties across the formulation series.