Influence of the diene monomer on devulcanization of EPDM rubber

Abstract

Ethylene-propylene-diene rubbers (EPDM) with 2-ethylidene-5-norbornene (ENB), dicyclopentadiene (DCPD), and 1,4-hexadiene (HD) as third monomers have been vulcanized with peroxide and with a conventional sulfur vulcanization recipe, and their devulcanization was subsequently investigated for recycling purposes. The behavior of these vulcanizates during pure thermal devulcanization depends on the EPDM third monomer and the crosslinker used. Peroxide vulcanizates of ENB-EPDM devulcanize only to a small extent and predominantly by random scission, whereas peroxide vulcanizates of HD-EPDM devulcanize by crosslink scission. In contrast, sulfur vulcanizates of ENB-EPDM, devulcanize mainly by crosslink scission. During devulcanization of sulfur-cured HD-EPDM, scission of both crosslinks and main chains occurs. Sulfur-cured DCPD-EPDM cannot be devulcanized but shows further crosslinking instead. In those cases, where purely thermal devulcanization is already effective to a certain extent, diphenyldisulfide as devulcanization agent increases the effectivity during thermochemical devulcanization. Hexadecylamine as an alternative devulcanization agent is effective for ENB-EPDM but does not contribute to thermochemical devulcanization of HD-EPDM. In summary, devulcanization proceeds by different mechanisms in ENB-EPDM, DCPD-EPDM, and HD-EPDM. Explanations are given in terms of the chemical structures of the third monomers, the corresponding crosslinks, and devulcanization agents.

Investigation of new composite materials based on activated EPDM rubber waste particles by liquid polymers

“…3 Among the most used types of physical processes are: mechanical, 4,5 thermo-mechanical, [6][7][8][9][10][11] ultrasonic, [12][13][14][15][16] and microwave. [17][18][19][20][21] In the chemical process different organic amines, [22][23][24] disulfides, 25,26 mercaptans, 27 and inorganic systems [28][29][30] have been intensively studied. All the above mentioned processes are aimed to break the crosslinks formed during vulcanization.…”

Effect of Temperature on Devulcanization of Waste Sidewall Rubber by Supercritical Ethanol

“…1 Various types of devulcanizing routes have been studied so far in order to improve the quality of the recycled products, such as chemical method, mechanical process, microwave technique, ultrasonic method and microbial method. [2][3][4][5][6][7][8][9][10][11][12][13] However, some processes have weaknesses such as environmental pollution and low efficiency.…”

Cross-linking of rubber in the presence of multi-functional cross-linking aids via thermoreversible Diels-Alder chemistry

“…DA cross-linking proceeds via the cycloaddition of a diene to a dienophile, typically a furan and a maleimide, at relatively low temperature (e.g. 50 °C) [16][17][18][19]. De-cross-linking via the retro DA reaction is favored at high temperature (typically above 100 °C), thus allowing the material to be reshaped or recycled.…”