PRESSURE-DEPENDENCE OF THE DEMIXING BEHAVIOR IN POLYMER BLENDS .1. EXPERIMENTAL PROCEDURE

The most common way to influence the liquid-liquid phase behaviour in partially miscible (co-)polymer blends is changing the blending temper ature. Since most extruders can handle pressures, up to 300 bar, press ure may also be used to influence the miscibility of polymers during b lending. We have developed equipment and an experimental procedure to study the pressure dependence of the liquid-liquid demixing behaviour of high-viscous polymer blends under equilibrium conditions. Small amo unts (1-4 grams) of specially made polymers are blended in the 'DSM MI NI EXTRUDER'. After a chosen mixing time, a small portion of the blend is injected into a small capillary tube and kept at the blending temp erature. The phase behaviour of the blends as a function of temperatur e and pressure is studied via laser light scattering (at a scattering angle of 90 degrees) in a specially made 400 bar/250 degrees C window autoclave, where the capillary cell is placed in a high temperature gr ade silicon oil.