Effect of Temperature on Devulcanization of Waste Sidewall Rubber by Supercritical Ethanol

The influence of temperature on devulcanization of waste sidewall rubber via supercritical ethanol was investigated. The effect of parameters on devulcanizing process was analyzed by a full factorial experimental design. The devulcanized products at different temperatures were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetry and derivative thermogravimetry (TG-DTG) and Fourier transform infrared (FTIR) spectrophotometry. In addition, the kinetics analysis for the devulcanizing process via supercritical ethanol was established. It was found that the reaction temperature was the only significant parameter. When the temperature rose above 240 ºC, the reaction rate increased dramatically. A special phenomenon was observed that the devulcanizing reaction rate of natural rubber (NR) was faster than that of butadiene rubber (BR) in supercritical ethanol. Moreover, when the reaction temperature reached 270 ºC, the use of the devulcanizing reagent did not significantly affect the sol fraction. The analysis of experimental results indicated that supercritical ethanol beyond the critical temperature could strongly promote the devulcanizing reaction, maintaining polymer structure of products as the most intact state.