Reduced zinc oxide levels in sulphur vulcanisation of rubber compounds: mechanistic aspects of the role of activators and multifunctional additives

This thesis has been devoted to a great many different possibilities to reduce the level of ZnO in rubber compounds, with emphasis on the development of a new type of activator. It must be realised that vulcanisation is a complex process, whereby many ingredients and parameters play an important role. ZnO and zinc-containing species are considered indispensable for the vulcanisation process and certainly difficult to substitute. Long-term solutions for the reduction of emissions of zinc into the environment should be focused on the development of new and effective concepts for completely new zinc-free vulcanisation systems. Short-term strategies will be mainly concentrated on reduced dosages of zinc and a higher chemical activity, combined with an increased solubilisation. In this respect progress has been made by the development of the ZnClay. In summary, the research described in this thesis combines a pragmatic in-rubber investigation and a fundamental study of the chemistry all through the vulcanisation reactions cascade. It has contributed to a better understanding of the role of the activator in the sulphur vulcanisation process.