Investigation of different ingredients contributing to the cure torque in silica-filled SSBR compounds

Anmol Aggarwal, Fabian Grunert, Sybill Ilisch (Contributor), Thomas Stratton (Contributor), Anke Blume (Contributor)

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Chemical crosslinking of elastomers through the vulcanization process creates a three-dimensional network and makes them suitable for many engineering applications. During this reaction, the polymer chains are linked to each other in presence of curing agents. The extent of crosslinking can be quantified by an MDR measurement: the higher the crosslinking density the higher the measured torque. In unfilled rubber samples, the MDR torque correlates directly with the chemical crosslink density.
Active fillers like carbon black and silica are added to improve the elastomeric properties. In case of filler containing vulcanizates, the MDR torque is affected additionally by the strength of the filler network and morphological factors. However, in silica-filled compounds, silica interferes with the crosslinking mechanism of the elastomers. Due to the presence of polar hydroxyl groups on its surface, silica particles tend to form clusters, thus causing filler flocculation. Also, the adsorption of accelerators on the silica surface leads not only to a slower but also to a less efficient reaction. Furthermore, additional crosslinks can be formed in the presence of silane, resulting in a polymer-silane-silica coupling which adds to the complexity of the reaction. Therefore, in a typical tire tread compound, multiple factors can occur that contribute to the cure torque which means that the torque may not necessarily correlate to the chemical crosslink density. To evaluate this further, the different contributions to the cure torque of silica-silane-filled functionalized and non-functionalized SBR compounds were investigated: the compound viscosity, filler-filler and filler-polymer interactions, and the polymer crosslinking. At low silica loading, the polymer crosslinking dominates the cure torque. However, as the filler loading increases, the filler-filler interaction increasingly contributes to the cure torque. This understanding can help to further improve properties of tire tread compounds and also support the development of more efficient polymer-filler systems.
Original languageEnglish
Publication statusPublished - 11 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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