We study the influence of the surface energy and contamination films on rubber adhesionand sliding friction. We find that there is a transfer of molecules from the rubber to thesubstrate which reduces the work of adhesion and makes the rubber friction insensitive tothe substrate surface energy. We show that there is no simple relation between adhesionand friction: adhesion is due to (vertical) detachment processes at the edge of the contactregions (opening crack propagation), while friction in many cases is determined mainly by(tangential) stick-slip instabilities of nanosized regions, within the whole sliding contact.Thus while the pull-off force in fluids may be strongly reduced (due to a reduction of thework of adhesion), the sliding friction may be only slightly affected as the area of realcontact may be dry, and the frictional shear stress in the contact area nearly unaffected bythe fluid.
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