Silica‐Ethylene Propylene Diene Monomer Rubber Networking by In Situ Sol‐Gel Method

Abstract

Triethoxysilyl‐grafted ethylene propylene diene monomer rubber (EPDM) was prepared with the silane coupling agent, bis‐[‐3‐(triethoxysilyl)‐propyl]‐tetrasulfide (TESPT), and thus modified rubber has been treated by an in situ sol‐gel method with the objective to grow silica particles inside the rubber matrix. TESPT grafted EPDM rubber, filled with the silica particles grown by making use of the described method, was found to exhibit excellent physical properties, despite the fact that the fraction of silica fillers in this material is found to be very low. In particular, thus produced filled rubber has higher reinforcing efficiency that is attributed to the formation of a rubber‐silica network. In addition, better silica dispersion is observed in the shear modulus measurements at low dynamic deformation amplitudes, which is in qualitative agreement with the ‘Payne’ effect that quantifies the ability of fillers to promote the formation of rubber‐filler networks. No such effect of network formation was observed when an in situ sol‐gel experiment was performed in the absence of TESPT. TEM observations showed that even if the amount of silica fillers in rubber is as small as 5 phr or less, the uniform mono‐dispersed distribution of the silica primary particles is still the main factor responsible for the reinforcement of the rubber matrix.

Keywords:

• silica
• silane coupling agent
• sol‐gel
• rubber
• nanocomposite

Acknowledgments

We thank to DIK (Deutsches Institut für Kautschuktechnologie e. V., Hannover (Germany)) for providing the TEM pictures. Dr. Carla Recker, Continental AG, Hannover (Germany) is acknowledged for her helpful discussion. This work was funded by the German Federal Ministry of Education and Research (BMBF) Grant 03X0002E.