The localization of organically modified nanoclays in chlorobutyl rubber (CIIR) and natural rubber (NR) blend system was carefully studied by following the vulcanization behaviour, morphology, thermal and solvent permeation characteristics. From the vulcanization studies, it was observed that incorporation of nanoclay platelets significantly affected the viscosity and vulcanization parameters such as cure time, scorch time, rate of cure and the degree of cure. Thermal analysis pointed out that the addition of nanoclay increased the thermal stability of the elastomer blends. The morphology of the blends indicated that the nanoclay platelets were localized at the interface and in both phases (mixed mode morphology) of elastomer blends and this affected the overall properties. The transport characteristics of NR/CIIR blend nanocomposites using toluene as the solvent were also studied. The transport parameters such as the equilibrium uptake, diffusion coefficient and the rate constant have been computed. The transport characteristics have been correlated with the microstructure of the blend nanocomposites. Finally, applied the Peppas–Sahlin model to fit the experimental diffusion data and the fitting was found to be reasonably good. POLYM. COMPOS., 39:E1659–E1668, 2018. © 2017 Society of Plastics Engineers