An investigation into the mechanisms for styrene-butadiene copolymer (SBR) conversion in combustion and gasification environments

The thermal degradation (pyrolysis and combustion) of styrene-butadiene rubber has been studied thermo-gravimetrically using various heating rates (10, 20, 30, 40 K/min) and various atmospheres (pure N-2, 3% H-2/N-2, air, 30% O-2/N-2). Calculation of apparent kinetic parameters pre-exponential factor, activation energy and reaction order for the different conditions was done to enable modeling efforts. Gas phase chemical species measurement provides some insight into the possible degradation mechanisms and is explained. The outcome of the experiments show under gasification there is a single reaction mechanism occurring whereas in a combustion environment a two-stage reaction sequence (primary and secondary) is present at the tested heating rates. The primary reaction exhibits a thermal degradation that follows diffusion of oxygen to the surface, followed by gas phase oxidation, while the secondary reaction is more representative of a heterogeneous decay mechanism. Testing in a hydrogen-spiked atmosphere, surprisingly, did not have a significant effect on the gasification rates of SBR. In addition, this atmosphere resulted if? a carbon residual that remained in the sample crucibles, something that was not observed in other atmospheres, including nitrogen.