With the increasing interest in the reuse of polymeric materials, recycling of rubber is receiving a lot of attention. The aim of devulcanization is to bring vulcanized rubber back to a plastic state by breaking down the polymer network. In the present study, a sulfur vulcanized EPDM ENB-terpolymer was used to investigate its devulcanization reaction at temperatures of 200°C (commonly used for NR recycling) and higher. Preferably only the sulfur cross-links should be broken during devulcanization. Theories of gel formation can be used to correlate the amount of polymer released from the network to the decrease in network chain density in the two extreme cases of random main chain scission and selective cross-link scission. This provides a tool to determine whether cross-links or polymer chains are broken in thermal devulcanization of EPDM. Desulfurisation of the cross-link sites was investigated with solid state NMR on devulcanized EPDM with ~(13)C-labeled olefinic carbons.
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