Quantifying and comparing the selectivity for crosslink scission in mechanical and mechanochemical devulcanization processes

Devulcanization processes have potential to increase the economic value of ground tire rubber (GTR) derived from waste tires, although the chemistry of the devulcanization process is still poorly understood. This article presents a method, based on sol extraction and swelling measurements, for quantifying the selectivity for crosslink scission over main chain scission, and applies it to extrusion-based mechanical and mechanochemical devulcanization processes at various operating conditions. The mechanochemical devulcanization process, using diphenyl disulfide and process oil, resulted in a higher selectivity for crosslink scission than the mechanical devulcanization process. Furthermore, it was shown that the process oil, along with lower reaction temperature, in the mechanochemical devulcanization process was responsible for the increased selectivity, rather than the presence of diphenyl disulfide. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43932.