Propylene/1-hexene copolymer as a tailor-made poly(propylene) for membrane preparation via the thermally induced phase separation (TIPS) process

Abstract

Poly[propylene-co-(1-hexene)], one example of a "tailor-made poly(propylene)", was synthesized using an iso-specific metallocene catalyst in order to study the influence of copolymer composition on the pore size of isotactic poly(propylene) (iPP) membranes prepared by the TIPS process. The structure of the copolymers and their properties in solution were analyzed and discussed in relation to the polymer-diluent phase diagram, the droplet growth kinetics during the TIPS process, the viscosity of the system and the final pore size of the membranes. The crystallization curve in the phase diagram was found to shift significantly as comonomer content increased and thus the droplet growth period was drastically increased. The resulting increase of the characteristic pore size in the membranes demonstrated that it is possible to use tailor-made poly(propylene)s to control the pore size in porous membranes prepared via the TIPS process (under otherwise constant conditions).