Pore Size Control of Microporous Polyethylene Membrane Using Diluents Mixture Containing Poly(tetramethylene glycol) and Paraffin

摘要

In the TIPS process, the homogeneous polymer/diluent mixture is prepared by melt mixing at a relatively high temperature wherein the mixture undergoes phase separation (liquid-liquid phase separation) upon cooling due to upper critical solution temperature (UCST) type phase behavior. After liquid-liquid phase separation, the polymer- diluent mixture is solidified by further cooling below the crystallization temperature (solid-liquid phase separation). The polymer-rich phase becomes the matrix of a microporous membrane upon removal of the polymer-lean phase, which is composed of nearly pure diluents, and forms droplets dispersed uniformly in the matrix. Subsequently, the polymer-lean phase is easily eliminated to form pores in the microporous membrane.