Comparative study of conventional rubber additives as devulcanization aids

Rounak Ghosh, Olivier Prud'homme (Contributor), Peter Uytterhaegen (Contributor), Jacques W.M. Noordermeer (Contributor), Wilma K. Dierkes (Contributor), Anke Blume (Contributor)

Research output: Contribution to conferencePosterAcademic

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In this study, sulfur-vulcanized natural rubber is thermo-mechano-chemically devulcanized in the presence of oil and a devulcanization aid (DA). Three potential DA’s are compared in terms of efficiency, as well as processability and mechanical properties of the devulcanizate:
1. N-cyclohexyl-2-benzothiazole sulfenamide (CBS)
2. Bis-3-triethoxysilylpropyldisulfide (TESPD)
3. Bis-3-triethoxysilylpropyltetrasulfide (TESPT)
The feedstock was aircraft tire treads, and the process was based on a devulcanization step in an internal mixer followed by homogenization on a two roll mill. The process parameters for the devulcanization like temperature, residence time, fill factor, rotor speed, oil and DA concentration were optimized for the best balance of degree of crosslink scission and mechanical properties. Using these optimized parameters, the three devulcanization aids were added separately in variable quantities, and the results were comparatively analyzed in terms of Mooney viscosity, crosslink density as measured by equilibrium swelling as well as the ratio of crosslink to random scission according to the Horikx-Verbruggen method. A white rubber test allowed to analyze the number and size of insufficiently devulcanized particles by blending with a bright white compound. Devulcanized material was finally revulcanized without any further additives than the curatives.
The use of TESPD as devulcanization aid resulted in the highest quality devulcanizates within this series: a tensile strength of 12.8 MPa at 204% elongation with 76% network breakdown by mainly crosslink scission. Technical rubber goods like shock absorbers, floorings or insulation materials can be made from 100% devulcanizate. It can also be blended with compounds for high performance rubber products like tires, seals, conveyor belts etc. in considerable quantities.
Original languageEnglish
Publication statusPublished - Jun 2021
EventDKG Elastomer Symposium 2021 - online, Germany
Duration: 28 Jun 20211 Jul 2021


ConferenceDKG Elastomer Symposium 2021


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