Chemically crosslinked yet reprocessable epoxidized natural rubber via thermo-activated disulfide rearrangements

The thermo-activated reprocessing ability of a chemically crosslinked epoxidized natural rubber (ENR) is investigated. Disulfide groups are introduced into the rubber using dithiodibutyric acid (DTDB) as a crosslinker. DTDB-cured ENR presents strong elastomeric properties due to the high molecular weight of the rubber and efficient crosslinking. The material behaves like a standard natural rubber until 100 °C and becomes reprocessable above 150 °C, owing to disulfide rearrangements. After grinding to a fine powder, the crosslinked rubber can be reprocessed and recovers most of its initial mechanical properties. The heat-triggered disulfide rearrangements are characterized in terms of stress relaxation, creep/recovery, adhesion tests, and swelling experiments. Comparison is made with ENR samples crosslinked by permanent links.