EFFECT OF SURFACE-PROPERTIES ON POLYMER MELT SLIP AND EXTRUSION DEFECTS

The purpose of this study is to analyse the flow of a linear polydimet hylsiloxane of high molecular weight on plane surfaces that may intera ct differently with the silicone fluid used. Stainless steel surfaces and slightly rough silicon surfaces were examined, including silica su rfaces where monolayers of fluorine chains were grafted on by silanati on reactions. The interest and principle of these reactions are briefl y recalled. The quality of the surface treatment was checked by wettin g experiments. For each ''fluid-wall material'' pair, flow rate measur ements were performed under a given pressure. In addition, the extruda te was photographed under various flow regimes. Combined analysis of t he flow curves and observations at the die outlet helped to determine the effect of roughness and of the wall material for the specific flow conditions considered.