Structure–Property Relations in Epoxidized Natural Rubber/Ethylene–Vinyl Acetate/Polypropylene Thermoplastic Vulcanizates: Combined Effects of Co‐Agent Loading and Rubber Blend Ratio

ABSTRACT Polypropylene (PP)‐based thermoplastic vulcanizates (TPVs) often suffer from limitations in strength, elasticity, and durability due to an incomplete understanding of how curing chemistry and rubber blend composition control network formation and interfacial structure. In this work, epoxidized natural rubber (ENR)/ethylene–vinyl acetate (EVA)/PP TPVs were prepared via peroxide curing using trimethylolpropane trimethacrylate (TMPTMA) as a co‐agent and phenolic‐modified polypropylene as a compatibilizer. Increasing the TMPTMA loading from 7.5 to 20.0 phr enhanced the tensile strength and hardness but reduced the elongation at break, reflecting higher crosslink density and restricted chain mobility. Additionally, an intermediate loading of 12.5–15.0 phr provided the best balance of strength, recovery, and processability. At a fixed PP content of 40 wt% (TMPTMA loading of 12.5 phr), the 30/30/40 ENR/EVA/PP blend exhibited the finest rubber dispersion (~1.90 μm) and the highest tensile strength (~11.44 MPa), storage modulus, and complex viscosity, consistent with strong interfacial adhesion. Furthermore, EVA‐rich blends showed superior aging resistance and the lowest oil uptake, whereas ENR‐rich blends exhibited higher swelling but lower tension set and improved elastic recovery. Increasing the EVA content caused the glass transition temperatures of both phases to shift upward due to interfacial constraints and a larger constrained amorphous fraction.