One can assume that in the presence of filler particles there is a good orientation of rubber macromolecules due to the applied stress, which results in increased crystallization capabilities. Therefore, the tensile strength and the elongation at break are increased. The topics of oxidation of chromium(III) salts to the chromium(VI) salts were analysed by ourselves. Vulcanizate of carboxylated butadiene-acrylonitryle rubber includes 0.11% chromium(III) given as Cr2O3 (measurement according to the norm PN-74/P-22110) [11]. Determination quality of chromium(VI) performed according to the norm PN-EN ISO 20344:2005 (V) 6.11 –content chromium(VI) – 0.00 mg/kg did not show presence of chromium(VI) salts. From the thermogravimetry experiments