Post-consumer tires back into new tires : de-vulcanization and re-utilization of passenger car tires

Abstract

Enabling recycling loops for used passenger car tires is a challenge and an opportunity. The challenge lies in the presence of SBR as the main elastomer in this type of tires, which makes this material difficult to reclaim due to the tendency of the elastomer chain fragments to re-combine. The opportunity lies in the wide availability of the material and in the fact that passenger car tires form a huge potential market for recycled rubber. The aim of this study is to develop a de-vulcanization process for passenger car tire rubber, as sensitive to tire compound compositions. The research described in this thesis is focused on the influence of material composition on the de-vulcanization efficiency and material properties, on choosing an appropriate de-vulcanization aid, on optimizing the de-vulcanization process conditions, and finally on an application study. Polymer chain scission mainly occurs during physical treatment, therefore a shift of the balance between physical and chemical breakdown in a thermo-chemical de-vulcanization process will lead to a higher ratio of crosslink scission to polymer chain breakage, the precondition for efficient de-vulcanization. The first objective within this study is to define the pathway for the most efficient de-vulcanization process of SBR. Secondly, a best compromise for the de-vulcanization process conditions for all tire rubbers needs to be found. Finally, the intention is to investigate the productivity of the process for whole passenger car tire material and its properties in new tire products.