MICROPOROUS MEMBRANE FORMATION VIA THERMALLY-INDUCED PHASE-SEPARATION .3. EFFECT OF THERMODYNAMIC INTERACTIONS ON THE STRUCTURE OF ISOTACTIC POLYPROPYLENE MEMBRANES

Isotactic polypropylene membranes were prepared via thermally-induced phase separation using three isotactic polypropylene-diluent systems, at three concentrations, and two thermal histories. The three diluents had similar structure and molar volume, but differed in end-group structure and therefore differed in interactions with the isotactic polypropylene (iPP). The two thermal histories represented isothermal and non-isothermal thermally-induced phase separation processes. Membrane structure as determined by scanning electron microscopy depended on the phase separation mechanism (liquid-liquid versus solid-liquid), which depended on the concentration-dependent isotactic polypropylene-diluent interactions and the thermal history.