Reclaiming of EPDM Rubber: A Comparative Evaluation Of Amines And Disulfides As Devulcanization Aids

While reclaiming of NR-based rubber has been in practical use for many decades, recycling of EPDM-vulcanizates turns out to be much more difficult. Three chemicals were studied as reclaiming aids for EPDM-vulcanizates differing in network structure: hexadecylamine (HDA), diphenyldisulfide (DPDS) and o’o’-dibenzamidodiphenyl disulfide (BAFD). For a conventionally cured, mainly polysulfidic EPDM vulcanizate, HDA turns out to be most effective in breaking the network compared to DPDS and BAFD. However, all three reclaims can be added up to 50 wt% to a virgin EPDM masterbatch, without significant deterioration of the re-vulcanized properties. For an efficiently vulcanized, mainly monosulfidic EPDM material, DPDS and BAFD plasticize the vulcanizate to a higher extent than HDA does. The reclaims obtained with HDA and BAFD give very good properties when added to the virgin EPDM masterbatch; some properties are even improved. The use of DPDS as reclaiming aid in this case results in a reclaim which lacks the ability to be re-vulcanized, with a significant reduction in properties as the result. Overall, HDA turns out to be the most universal devulcanization aid for EPDM, as it results in a more or less well-plasticized and re-vulcanizable material, independent of the network structure of the EPDM to be reclaimed.