EFFECT OF FLOW ON POLYMER-POLYMER MISCIBILITY

The effect of shear now on the phase behaviour of partially miscible b lends exhibiting a lower critical solution temperature behaviour has b een investigated. Miscibility limits were detected, with and without t he application of now, as changes from optical clarity to turbidity us ing light scattering and as the appearance of double glass transition temperatures. Light scattering data were collected on a rheo-optical d evice that was designed to monitor phase changes in polymer blends und ergoing shear now between parallel glass plates in a temperature contr olled environment. Glass transition temperatures of some quenched shea red blends were measured using a differential scanning calorimeter in order to confirm the conclusions from the light scattering data. It wa s found that shear induced demixing and shear induced mixing may be ob served within the same blend depending on the magnitude of the applied flow. Miscibility gaps and closed miscibility loops may appear in the phase diagrams. At certain temperatures and shear rates unusual scatt ering patterns were observed and these were associated with a ''ripple '' morphology when directly viewed through the microscope.