Regeneration and Devulcanization

Every year, approximately one billion used tires reach the end of their useful life worldwide. Many of these end-of-life tires end up in landfills. They provide an ideal breeding ground for pests and become a danger to the environment. Through advanced recycling techniques, high-quality rubber shredders and other state-of-the-art equipment, used tires can be transformed into new useful materials. Instead of dumping waste tires in landfills or used as fuel in cement plants, these waste materials can be seen as a new material which once recycled can substitute virgin raw material. So, recycled tires can offer both economic and environmental benefits.
Ground rubber is produced by grinding tyres at ambient temperatures or by pre-cooling them with liquid nitrogen to reduce rubber particle size to less than 500 micrometer. Ground tire rubber is used in several applications from paving, playgrounds and other surfaces to landfill liners, moulded rubber products and a small part of these granules is intended for devulcanization.
Devulcanization remains the best way to recycle used tires at the end of their life. However, improvements and optimizations of devulcanization processes are still awaited in order to obtain better quality devulcanized material that will allow this “new” secondary material to be used on a large scale.
In addition to the improvements to be made to the devulcanization process, work must be done upstream of the devulcanization process to improve the quality, Homogeneity and the cleanliness of the ground tire rubber.
Today, used tire granulators and granulate manufacturers sort the different used tires by considering the size of the tire. These tires are therefore classified into three batches: truck tires, passenger car tires, agricultural and off road tires (OTR). This method of sorting is largely sufficient to obtain an acceptable material for paving, playgrounds... etc., but is insufficient for devulcanization, which is more sensitive to variations in the input material and therefore requires a more thorough sorting.The purpose of this chapter is therefore to show the effect and importance of sorting on the quality of the devulcanized material, on its stability and on the stability of the thermomechanical devulcanization process.