Strategic optimization of plasticizers, fillers, and blend ratios for enhanced performance of dynamically cured epoxidized natural rubber (ENR)/polypropylene (PP) thermoplastic vulcanizates

This study introduces an innovative methodology for optimizing oil, plasticizer, filler, and blend proportions in epoxidized natural rubber with 20 mol% epoxide (ENR-20) and polypropylene (PP) thermoplastic vulcanizates (TPVs), aiming to achieve superior rheological, mechanical, morphological, and thermal performance. By leveraging paraffinic oil, epoxidized soybean oil, and phthalate-based plasticizers, the research investigates their influence on tensile strength, elasticity, and processability. Among the oils and plasticizers evaluated, paraffinic oil demonstrated the most effective plasticizing performance, offering superior flexibility and elasticity. Various paraffinic oil loadings (15 phr, 25 phr, 30 phr, 35 phr, 40 phr, 45 phr, 50 phr, and 75 phr) were investigated in the 60/40 ENR-20/PP blend, with 30 phr identified as the optimum level. This formulation yielded the highest elongation at break (~410%) and a reduced tension set of less than 50%. The study also evaluates the role of carbon black and silica fillers, investigated at loadings of 10 phr, 20 phr, 30 phr, 40 phr, and 50 phr in the 60/40 ENR-20/PP blend, focusing on their reinforcement effects and contributions to thermal stability. Carbon black at 30 phr exhibited effective reinforcement, yielding tensile strength values above 7.0 MPa and elongation at break of up to 380%. Variations in ENR-20/PP blend ratios (40/60, 50/50, 60/40) demonstrate a clear pathway for optimizing phase morphology and mechanical performance. Advanced techniques such as differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) reveal critical correlations between crystallinity, glass transition behavior, and morphological features with processing parameters. These results underscore the strategic importance of tailored additive selection and precise blending methodologies, offering a roadmap to advance TPV materials for industrial applications that demand durability, flexibility, and cost-effectiveness.