Exploring tire crumb as activator for sulfur vulcanization

In this study, a new approach to reduce the environmental effects of end of life and waste rubber and, at the same time, to minimize the ZnO levels in rubber compounds is presented. The use of tire crumb as activator for sulfur vulcanization is investigated. To give an insight into the reaction mechanism, the approach is tested using model compound vulcanization (MCV) with squalene as a model molecule. The results showed that the use of the new recipe does not alter the kinetics of the vulcanization and that the cross-link degree achieved is nearly equivalent to using ZnO. However, in real rubber mixtures [natural rubber (NR), butadiene rubber (BR), and styrene-butadiene rubber (SBR)], there is not a correlation between the promising characteristics seen in MCV and the actual performance of tire crumb. The extent of cross-linking is significantly lower and the mechanical properties are worst in most of the cases. In spite of that, the results found in MCV suggest that further research should be carried out in order to take advantage of the features observed by improving or facilitating the interaction between the chemicals present in the tire crumb and the ingredients added to the rubber matrix.