Elastomeric materials are used as barriers to protect workers against exposure to chemicals. The effectiveness of a polymer as a chemical protective material depends on the rate of permeation of chemicals through it. The permeation rate is dependent on the type and amount of fillers added into the polymer matrix. In this study, Chlorobutyl nanoclay composites were prepared by addition of organically modified and unmodified nanoclays at different filler loadings. The nanocomposites were swollen in three solvents of varying cohesive energy density until equilibrium and desorption experiments were carried out. The data obtained from desorption experiments was used to determine the diffusion coefficients. The concentration-dependent diffusion coeffecient (D) was calculated at high and low concentration regions and it was found that D is one-order less in lower concentration region than in the higher concentration range. The aspect ratio of the nanoclay fillers in the composite was calculated by assuming square and disc shapes and it was found to vary with the type of solvent and the used and filler loading. (c) 2006 Wiley Periodicals, Inc.