Measurement of the Compression Set of the Rubber Vulcanizates The compression set of the rubber vulcanizates was measured at 25% compression at 100C for 24 h, using cylindrical samples, 13.1 mm thick and 28.9 mm in diameter, according to the procedure described in ASTM D395-03. The samples were placed in a compression set testing apparatus (Taha Ghaleb Toos Co. Iran) and at the end of the test, the samples were removed and allowed to cool at room temperature for 30 min and then the set was calculated using the following expression