Effect of Mercaptobenzothiazole on Rubber Structure during Oxidation, Heating and Milling

Abstract

Abstract 1. Mercaptobenzothiazole (MBT) accelerates the oxidation of natural rubber and considerably increases the rate of its oxidative degradation. 2. When benzene solutions of natural rubber are heated in an inert gas atmosphere at 100°, no irreversible changes occur in the rubber whether in presence or in absence of MBT. 3. Plasticization of natural rubber in air at 100–150° is intensified in presence of MBT, which is caused mainly by the accelerating action of the latter on the oxidative degradation of rubber. 4. Mercaptobenzothiazole assists plasticization of rubber at low temperatures in an inert gas atmosphere. MBT is consumed in the process, owing to its interaction with the polymeric radicals formed by mechanical rupture of the rubber molecules. 5. The amount of MBT reacting with the rubber increases with increasing contents of 1, 4 structure in the rubber molecules. 6. It is shown that different fractions of the masticated product contain different amounts of MBT, indicating that MBT reacts preferentially with the end valencies of the radicals formed by cleavage of diallyl bonds. 7. Reaction schemes for the interaction of MBT with rubber in mechanical and oxidative processes are suggested.