Anisotropic flat sheet membrane formation via TIPS

The anisotropic flat sheet i-PP membranes have a vast variety of applications in bio-engineering such as oxygenators and artificial organs. This type of membranes was prepared via thermally induced phase separation (TIPS), by using of diphenyl ether (DPE) as a diluent. Anisotropic structure was gained by evaporating diluent from one surface of a polymer-diluent uniform mixture, before phase separation. The effect of evaporation times (0.5, 2, 4 and 7 min.) on the membrane structure was investigated by scanning electron microscopy (SEM). Furthermore, pore size was measured to analyze anisotropy of the membranes. At the beginning of evaporation, pore size distribution is same within the membrane thickness. However, by increasing of evaporation time, gradually more diluents diffuse out and hence, polymer concentration increases and thereafter anisotropic structure takes place subsequently. So by increasing evaporation time, pore size decreases and finally by passing seven minutes of evaporation, microporous structure changes to a dense structure.

Keywords:

Thermally induced phase separation , Isotactic polypropylene , Anisotropic structure , Evaporation time