Application of supercritical carbon dioxide jet to recycle waste tire rubber: An experimental and optimization study

Abstract

Towards devising an efficient recycling technology concerning both rubber pulverization and devulcanization, this study employed supercritical carbon dioxide (ScCO2) jet for recycling waste tires. The particle size and devulcanization extent of the resulting ground tire rubber (GTR) were monitored at different processing conditions, which were optimized by adopting a response surface methodology. The use of ScCO2 jet led to fine GTR with irregular surfaces, with a sufficient pulverization of rubber observed at a high jet pressure. A higher temperature led to a high degree of devulcanization and an improved breakage selectivity of crosslinks. Moreover, it was found that an ambient pressure would not enhance rubber pulverization nor devulcanization; however, it was necessary to maintain the supercritical state of carbon dioxide. Upon optimization, the radical reactions between broken polymer chains or sulfur crosslinks led to a GTR devulcanization degree of approximately 45 %, registering a final particle size of 0.162 mm.