Activity: Talk or presentation › Oral presentation
Every year over 1 billion tires are discarded throughout the world, and the number keeps growing due to the increasing use of automotive transportation. In view of the depleting fossil resources used during tire production and the adverse environmental issues related to used tire disposal, there is an urgent need for effective recycling of them. Pyrolysis is a promising technology in used tire recycling. However, it has not commercially been successful mainly due to the low quality of the carbon black recovered during the process in comparison to the virgin carbon blacks used in the tire industry, the by far biggest consumer of this type of filler. This paper reviews the various used tire pyrolysis processes developed over the years and their associated products with focus on the solid product i.e. carbon black. The key parameters involved in used tire pyrolysis processes and their effects on the product yield and quality are also reviewed in this study. Furthermore, this review paper focuses on the features of pyrolytic carbon black (pCB) and its in-rubber performance. Moreover, chemical and physical treatments of pCBs are also discussed. The main features of carbon black in general are particle size, morphology, surface area and chemistry, which dictate its quality and performance in rubber composites. The major difference between virgin and pyrolytic carbon black is the presence of an inorganic ash content and impurities on the surface of pyrolytic carbon black. These impurities are non-volatile in nature, mainly based on carbonaceous deposits. Carbonaceous deposits originate from oil and elastomers condensed on the carbon black surface during pyrolysis, while the ash content comes from different ingredients used in tire manufacturing such as zinc oxide, sulfur and silica. Several studies show that the colloidal properties of pCBs are usually similar to virgin high reinforcing carbon blacks. However, when added to rubber, their performance is reported as comparable to semi reinforcing carbon blacks. This disparity in properties and performance is also discussed.