Post-consumer rubber waste is a problem, but at the same time also a challenge with a large potential: If the concentration of recycled rubber in e.g. tires can be increased significantly, the amount of reused rubber will increase considerably. The challenge is to develop a technology allowing to produce recycled rubber of a high quality. One of the problems is related to the source of the end-of-life rubber, its homogeneity and purity: rubber products in general consist of different compounds, and can contain external contaminations from the service life as well as internal ones such as reinforcing fibers.
The most promising technology for a high quality recycled rubber is devulcanization. In this process, in the ideal case, only the sulfur crosslinks will be broken, resulting in a processable rubber with properties comparable to the ones of the feedstock.
An extensive study was done to devulcanize different types of feedstock and determine the quality of the resulting products. The feedstock was varied in terms of age, single compounds versus a blend of different types of rubber, particle size of the feedstock, carbon black versus silica filled rubber, and different silica-silane combinations. In terms of the devulcanization process, pre-treatment of the ground rubber, type of process as well as processing time are discussed. Besides, the analysis of the recycled rubber will be discussed.
Finally, the sum of these considerations will result in an overview of the challenges and chances of devulcanization and reuse of rubber.