Degradation of styrene butadiene rubber (SBR) in anaerobic conditions

In this work, the degradation kinetics of styrene butadiene rubber (SBR) in solution was studied in anaerobic conditions. Degradation reactions in the presence of cumene hydroperoxide at different concentrations (0.20, 0.28, 0.32, 0.50, 0.60% in weight), temperatures (60, 75, 85, 100 and 120 °C) and aromatic solvent (10 and 20%) were performed. The fragmentation rates of polymer chains, which define the degradation kinetics, were calculated from the change in molecular weight distribution with time. The degradation was performed in a reactor with anaerobic conditions and the characterization was performed by multiangle light scattering coupled to size exclusion chromatography (SEC-MALS). Using population balance equations, it was possible to calculate the kinetic constants for thermal and thermooxidative degradation. Analysis of the results led to the conclusion that random scission of polymer chains produced by macroradicals formed by hydrogen abstraction constituted the predominant SBR degradation mechanism. Adding alkylbenzene as a transfer agent significantly reduced the degradation.