Waste tire rubber with low and high devulcanization level prepared in the planetary extruder

Abstract

Waste tires management is serious and global environmental problem. Therefore, searching for new and industrially applicable solutions to convert waste tire rubber into high-value added products is gaining more and more attention. Rubber devulcanization is step forward for further developing rubber recycling and upcycling technologies. Thermo-mechanical treatment of ground tire rubber (GTR) performed in twin screw extruders is currently the most popular solution, while literature information about alternative continuous methods are very limited. In this field of research, using of planetary extruders as multi-screw reactors seems to be interesting solution, which is due to their high mixing efficiency, good heat exchange and devolatilization capacity.In this work, thermo-mechanical treatment of GTR was performed in a lab-scale planetary extruder. Devulcanization effectiveness has been investigated by extruder torque monitoring, Mooney viscosity, swelling measurements, Horikx theory, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry, curing characteristics and tensile tests. Volatile organic compounds emitted from untreated waste tire rubber and reclaimed rubbers were determined using a gas chromatography combined with flame ionization detector or mass spectrometry. The results showed that GTR devulcanization efficiency and emission levels of volatile organic compounds increased with higher temperature during planetary extrusion. Mooney viscosity and tensile properties of GTR treated using a planetary extruder were comparable to the commercially available reclaimed rubbers. This work confirms that waste tire rubber devulcanization in the planetary extruder is a promising approach for further studies towards sustainable development of rubber recycling technologies and circular economy.