An investigation of the activity of carbon blacks recovered from elastomer composites

The activity of carbon blacks recovered from elastomer systems is determined by use of a temperature jump technique imposed on the carbon blacks in air using a TG unit. The elastomer composites were composed of styrene-butadiene rubber (SRR), fillers, activators, accelerators together with a number of different carbon blacks. The organic content was pyrolyzed away by heating in nitrogen, the atmosphere was changed to air and the activity of the carbons was assessed by the temperature jump method. This enables the Arrhenius parameters to be established for the gasification of the carbons in air. This data was compared with the oxidation rates of carbons before they were introduced into the elastomer system. Nitrogen adsorption surface areas based on a BET analysis showed that the surface area of the carbons was similar before and after incorporation into the composite. The kinetic parameters of the carbons were however somewhat altered by incorporation into the elastomer systems, but their order of activity towards the gasification process as assessed by their relative rate of gasification remained the same. This is explained by postulating that the higher rates of oxidation is associated with the present of edge carbon atoms at the surface compared to the much slower oxidation rates of the “basel” plane carbon atoms. It appears that this surface structure is largely retained in the composite carbon-elastomer system. This enables some speculation regarding the reinforcing action of certain carbon blacks in the composite system.