PhD thesis defence Rounak Ghosh

The research aims to develop a more environmentally sustainable devulcanization process for rubber sourced from silica-silane based passenger car tires to achieve a high-quality devulcanizate. A comprehensive literature review covers various aspects, including tire tread compounding, devulcanization mechanisms, and recent developments in devulcanization of ground tire rubber (GTR).

A screening of devulcanization aids (DAs) for passenger car tire tread granulate chosen from commonly used rubber chemicals, is conducted to identify the most promising one: vinyl silane with peroxide (VP). Optimization of devulcanization parameters using VP is performed for model tire tread material and whole tire granulate. Further investigations involve varying combinations of DAs assessing a synergistic effect, exploring the impact of individual constituents, and investigating devulcanization solely employing peroxides. The devulcanization reaction mechanism of vinyl silane and VP is analyzed using a liquid model compound.

In the next step devulcanization with variation in processing aid is carried out to pinpoint the optimal one. An examination of the influence of fillers and the effect of the silanization reaction on the devulcanizate properties is conducted.

The best devulcanizate is blended with a model passenger tire tread compound, and its applicability for tires is comprehensively analyzed. A comparison between newly developed devulcanizates and commercial counterparts is conducted, establishing a correlation between tensile strength and miscibility for samples devulcanized using various DAs and process conditions.

Results are transferred from a batch process and upscaled to an continuous extruder process, aiming to achieve increased productivity and to facilitate industrialization. The future of rubber recycling through devulcanization holds promise for reducing waste, conserving resources, and establishing sustainability in the rubber industry.