Promotion of desulfurization of vulcanized rubber by plasma treatment

Abstract

Molecular chains of vulcanized rubber are strongly linked by sulfur bridges, that is, covalent bonds via sulfur atoms. In order to recycle vulcanized rubber, it is necessary to cut sulfur bridges. We conceived the idea of shortening the desulfurization process, lowering the temperature, and making the desulfurization process dry by using plasma treatment, which can be expected to lower the activation energy of the cutting reaction by the action of radicals. As a first step, in this study, plasma treatment of vulcanized EPDM (Ethylene Propylene Diene Monomer) rubber was performed in a vacuum chamber. As a result, when hydrogen plasma was used, generation of sulfide water, which should be a product of the desulfurization reaction, was detected by QMS; in addition, the swelling rate of EPDM, or expansion rate after immersion in toluene container, after plasma treatment increased significantly compared to untreated EPDM. On the other hand, no such change was observed when argon or oxygen plasma was used.