Abstract <p>In recent years, the development of elastomeric composites with enhanced thermal stability and chemical resistance has gained momentum for advanced engineering applications. This study explores an optimized elastomeric blend matrix composed of epoxidised natural rubber (ENR, 33.33 phr), chloroprene rubber (CR, 53.33 phr), and hydrogenated nitrile butadiene rubber (HNBR, 13.34 phr), reinforced with varying contents of carbon black (CB, 30–60 phr) and hybrid combinations with silica (0–20 phr). Molecular transport kinetics was investigated using aromatic and halogenated solvents such as benzene, toluene, xylene, and carbon tetrachloride (CCl₄). Among the diffusion models studied, the Peppas–Sahlin model best described the solvent uptake mechanism, indicating the diffusion-controlled solvent uptake mechanism influenced by the filler network. Thermal degradation kinetics was studied using thermogravimetric analysis at multiple heating rates, and iso-conversional methods were employed to determine kinetic and thermodynamic parameters. Incorporating fillers significantly improved the composite performance in terms of diffusion and thermal stability. In CB-filled composites, the crosslink density increased by 316% to 477%, while hybrid systems with silica showed a further rise of 368% to 661%. The activation energy of the unfilled blend increased significantly with fillers. CB-filled systems showed enhancements of 77.6%, 80.5%, and 85.6% for CB30, CB40, and CB50, respectively. Hybrid systems with both CB and silica exhibited even greater improvements, with CB30S10, CB40S10, and CB50S10 showing increases of 109%, 122%, and 153%, and CB30S20, CB40S20, and CB50S20 displaying increases of 121%, 139%, and 144%, respectively. These results revealed that the incorporation of hybrid fillers significantly enhanced the thermal stability of the composites, as evidenced by shifts in degradation temperature, increased activation energy, and higher crosslink density.</p> Graphical Abstract <p></p>