シリカ配合天然ゴムの耐熱性

抄録

The heat aging behavior of silica filled natural rubber vulcanizate was compared with that of carbon black filled vulcanizate, using an air oven operating at 100°C. In the absence of antioxidant, the reduction rate in tensile strength (T_B) of the silica filled vulcanizate during the aging test was found to be similar to that of the carbon black filled vulcanizate. In the case of elongation at break (E_B), the reduction rate of the carbon black filled vulcanizate was higher than that of the silica filled vulcanizate. In the presence of an antioxidant, the decrease in T_B and E_B of the silica filled vulcanizate was very much lower than that of the carbon black filled vulcanizate. In addition to the conventional protection against chain scission and crosslink breakage of the polymer during thermal aging, the antioxidant in the silica filled vulcanizate appeared to have also changed the crosslinking structure of the polymer, as shown by the changes in sol content, crosslinking density and structure. It seemed that the silanol group on silica surface could activate the antioxidants, such as 2-mercaptbenzimidazole (MBI) to function as a secondary antioxidant.