Full factorial experimental design to study the devulcanization of ground tire rubber in supercritical carbon dioxide

tIn this study a 24factorial design was employed to investigate the supercritical CO2devulcanization pro-cess of ground tire rubber from end of life tires performed using diphenyl disulfide (DD) as devulcanizingreagent.The aim of the experimental design was to investigate the influence on the process of temperature,pressure, amount of devulcanizing reagent, treatment time and their interactions.The crosslink density, sol fraction, gel fraction and sulfur content were chosen as experimentalresponses. Multiple linear regression was used for modeling the relationship between each responseand the process variables. Reduced regression models were obtained for each response, considering onlythe significant variables and interactions. The predicted results from these reduced models showed goodagreement with the experimental values.Temperature, amount of DD and DD–temperature interaction resulted the relevant parameters for theprocess. On the contrary, the influence of treatment time, pressure and all other interactions proved tobe negligible.These results have an important outcome since this devulcanization process can be carried out in ashort time and at relatively low pressure, with subsequent energy saving.