Sliding friction between an elastomer network and a grafted polymer layer: The role of cooperative effects

Laboratoire de Physique de la Matière Condensée, FR 2844 du CNRS Collège de France - 11 place Marcelin Berthelot, 75231 Paris Cedex 05, France

Received: 7 September 2004
Accepted: 24 January 2005

Abstract

We study the friction between a flat solid surface where polymer chains have been end-grafted and a cross-linked elastomer at low sliding velocity. The contribution of isolated grafted chains' penetration in the sliding elastomer has been early identified as a weakly velocity-dependent pull-out force. Recent experiments have shown that the interactions between the grafted chains at high grafting density modify the friction force by grafted chain. We develop here a simple model that takes into account those interactions and gives a limit grafting density beyond which the friction no longer increases with the grafting density, in good agreement with the experimental data.