Influence of Functional Groups of Silane Coupling Agents on Dynamic and Mechanical Properties

Application:

Silica reinforced tire tread compounding in a Brabender^® PLASTI-CORDER^® Lab-Station internal mixer

Keywords: Silica; Coupling agents; Tires; Silane; Dynamic properties

Monofunctional coupling agents with only ethoxy groups or only sulphur groups, respectively a coupling agent with only one ethoxy group on each side of the molecule, were synthesised.

The effect of these coupling agents on mechanical properties of tire tread vulcanizates was compared to the one of TESPT. The experimental results prove, that a proper balance in functionalities is required for a coupling agent to enhance the properties of silica-reinforced tire tread compounds.

TESPT proves to best comply with this balance, because it allows for the primary and secondary coupling reaction towards the silica via its tri-ethoxysilyl groups, resp. for a sulphur donation and a coupling reaction towards the rubber polymer via its sulphur moiety. A coupling agent with only one reactive ethoxy group attached to the silicium atom vs. three for TESPT, performs surprisingly well. This coupling agent can only perform the primary reaction with the silica, which leads to a very quick equilibrium during mixing and consequently low mixer torques. It comes closest to TESPT in vulcanised compound properties, particularly the tan at 60°C, representative for tire rolling resistance. Only the tensile strength is lower than the one achieved with TESPT.

Authors: L.A.E.M. Reuvekamp, P.J. van Swaaij, J.W.M. Noordermeer

Corresponding Author: L.A.E.M. Reuvekamp, Vredestein Banden BV, Postfach 27, 7500 AA Enschede, The Netherlands

Tel.: +31 / 53 / 488 86 87

Fax: +31 / 53 / 488 83 02

Email: reuvekampl(at)vredestein.com

KGK January / February 2009