Results on blends containing different ingredients have revived the interest on the interaction parameter and crosslink density of structures that contain soft fillers. Composite blend of natural rubber and styrene butadiene rubber loaded with the percolation concentration of high abrasion furnace carbon black and different concentrations with paraffin wax were prepared. The applicability of the blends for liquid diffusion has been examined through the changes in the interaction parameter and the crosslink density at different temperatures. The transport mechanism through the vulcanized blends is governed by Fickian diffusion law at room temperatures and it becomes non-Fickian at higher temperatures. The diffusion coefficients were calculated and found to have an activated behavior with temperature from which the activation energy was calculated. The change in entropy, enthalpy, and Gibbs free energy are also studied at different temperatures. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 3232-3240,2009