Sulfur Migration In Recycled Ground Rubber Containing Compounds And Its Impact on Dynamic-Mechanical Properties

Stefan Achim Frosch, V. Herrmann (Contributor), Fabian Grunert (Contributor), Anke Blume (Contributor)

Research output: Contribution to conferenceAbstractAcademic

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Recycling waste is an essential part of Circular Economy. In the case of rubber products, the use of ground rubber is one possible recycling method to partially reuse the waste. For this, parts of the waste rubber of end-of-life tires are ground into small particles. This material can then be incorporated into new compounds to reduce the use of virgin material and thus the carbon footprint. However, the addition of Ground Rubber Particles (GRP) causes a deterioration in mechanical properties compared to compounds without recycled material.
To further investigate this characteristic behavior, two spatially resolved analytical methods were applied: the micro-X-Ray fluorescence analysis (μ-XRF) and the micro-dynamic-mechanical-indenter (μ-DMI). Using μ-XRF, it could be shown that sulfur migrates from the matrix into the already vulcanized GRP. The μ-DMI is able to determine viscoelastic properties: It reveals, that the elasticity is increased inside GRP whereas it is decreased in the matrix.
Sulfur migration gives a possible explanation for the observed property change. It is responsible for locally changing the crosslink density (CLD), which directly influences the viscoelasticity: The CLD is increased in the GRP and decreased in the matrix. Consequently, the poor crosslinking of the matrix is a possible reason for the deterioration of mechanical properties.
In addition, results of fundamental migration experiments provided further information about the sulfur migration process during mixing, vulcanization and storage: For this purpose, the degree of sulfur migration of pure sulfur and sulfur in presence of ZnO and / or stearic acid and / or accelerator was investigated.
The findings will help to improve the understanding of the migration process of sulfur into GRP. These results are also transferable to other applications such as retreading of truck tires and migration of sulfur between individual plies of passenger car tires that have not yet been vulcanized.
Original languageEnglish
Publication statusPublished - 10 May 2023
EventIRC RubberCon 2023 - University of Edinburgh, Edinburgh, United Kingdom
Duration: 9 May 202311 May 2023


ConferenceIRC RubberCon 2023
Country/TerritoryUnited Kingdom
Internet address


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