Mechanistic Insights Into Thermal Conductivity of 60/40 <scp>NR</scp> / <scp>HDPE</scp> Composites: Micro Versus Nanofillers

ABSTRACT The thermal transport behavior of a 60/40 natural rubber (NR)/high density polyethylene (HDPE) polymer blend can be explained primarily through matrix crystallinity and filler‐induced network formation. Morphological features, such as spherulitic arrangement, are negligible across all filler loadings. Below the threshold filler loading, thermal conductivity is dominated by the semicrystalline HDPE phase. Beyond this threshold, conduction shifts to network‐controlled pathways, with nanocomposites exhibiting more efficient enhancement. Both micro‐ and nanocomposites follow the same mechanistic progression from crystallinity‐dominated to network‐dominated conduction, though the rate and efficiency differ depending on filler size and distribution. Temperature further modulates performance: The composites achieve optimal conductivity at 30°C, retain acceptable levels at 60°C, but show reduced thermal transport at 90°C due to increased phonon scattering and limited network effectiveness. These findings demonstrate that principles established for single‐polymer systems extend to polymer blends, providing a coherent framework for designing thermally conductive polymer composites.