Effect of different devulcanization agents on the mechano-chemical devulcanization process of waste tires

Abstract

Herein, the effects of two devulcanization agents, i.e., disulfide oil (DSO) and tetramethyl thiuram disulfide (TMTD), byproducts of gas refineries, on the mechano-chemical devulcanization process of waste tires were investigated. The response surface methodology (RSM) involving Box-Behnken Design (BBD) was utilized for the optimization of different factors, i.e., reaction temperature, reaction time, and the content of devulcanization aids. Samples were prepared in a Brabender mixer at a temperature of 100°C, and a rotor speed of 80 RPM for 15 min, and the devulcanization percentage of the samples was determined using swelling test, Mooney viscosity, and Horikx’s theory. The results demonstrated that when 5 phr devulcanization agents were used, the devulcanization percentages for samples containing DSO and TMTD were 73 and 80%, respectively. In addition, the effect of reaction temperature, reaction time, and the content of devulcanization agents on the crosslink scission was also investigated. It was found that by increasing these three parameters, the crosslink density decreased while the devulcanization percentage increased. All in all, the results indicated that the performance of TMTD as devulcanization agent was better than that of DSO. We believe that our presented research study will open new avenues for effective recycling of waste rubbers.