INVESTIGATION OF THE SLIP TRANSITION AT THE MELT POLYMER INTERFACE

We present a detailed experimental investigation of the effect of mole cular parameters on the onset of strong slip at the wall for polydimet hylsiloxane melts flowing against silica surfaces on which a weak dens ity of polymer chains are anchored by adsorption. The observed variati on of the critical velocity for the onset of strong slip V proportion al to N-1.09 P-3.2, With N and P the polymerisation indices of surface and bulk chains, respectively, and the wide range of the non-linear f riction regime above V strongly support the description of the dynami c de-coupling between the surface and bulk chains in terms of progress ive disentanglement.