Elastomeric compounds from hydrogenated acrylonitrile butadiene rubber, organomodified clay, and perfluoropolyether (PFPE) additives were prepared. Characterization of the materials included X-ray diffraction, dynamic mechanical analysis (DMA), tensile mechanical properties testing, environmental scanning electron microscopy, and solvent permeability measurements, from which the solubility coefficient (S) and diffusion coefficient (D) values were determined. A synergistic effect of the two additives was observed because the presence of clay reduced D, whereas PFPE mainly decreased S. Increasing the mixing time facilitated the dispersion of the clay layers. DMA and the diffusivity data were used to estimate the aspect ratios of the solid inclusions in the rubber. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 3476-3482, 2011