Ultrasonic devulcanization reactors for recycling of GRT: Comparative study

The present paper describes the comparative study of a continuous ultrasonic devulcanization of ground tire rubber (GRT) using two reactors. The devulcanization zone in the first reactor (coaxial reactor) is located at the exit from an extruder without imposition of additional shearing. In the second reactor (barrel reactor), the devulcanization zone is located in barrel where additional shearing takes place due to screw rotation. Gel fraction, crosslink density, cure behavior and physical properties of GRT obtained in these two reactors were measured. Also, the distribution of gel fraction and crosslink density at various locations in the devulcanization zone of the barrel reactor were determined. Gel fraction and crosslink density show that GRT in both reactors is partially devulcanized. A unique correlation between gel fraction and crosslink density obtained in both reactors indicated that additional shearing had a positive influence on improving the efficiency of devulcanization. Under the optimal devulcanization condition, the physical properties of revulcanized GRT and the output are higher in the barrel reactor. Power consumption density in the barrel reactor is found to be significantly higher.