Non-Solvent- and Temperature-Induced Phase Separations of Polylaurolactam Solutions in Benzyl Alcohol as Methods for Producing Microfiltration Membranes

The possibility of obtaining porous films through solutions of polylaurolactam (PA12) in benzyl alcohol (BA) was considered. The theoretical calculation of the phase diagram showed the presence of the upper critical solution temperature (UCST) for the PA12/BA system at 157 degrees C. The PA12 completely dissolved in BA at higher temperatures, but the resulting solutions underwent phase separation upon cooling down to 120-140 degrees C because of the PA12's crystallization. The viscosity of the 10-40% PA12 solutions increased according to a power law but remained low and did not exceed 5 Pa center dot s at 160 degrees C. Regardless of the concentration, PA12 formed a dispersed phase when its solutions were cooled, which did not allow for the obtention of strong films. On the contrary, the phase separation of the 20-30% PA12 solutions under the action of a non-solvent (isopropanol) leads to the formation of flexible microporous films. The measurement of the porosity, wettability, strength, permeability, and rejection of submicron particles showed the best results for a porous film produced from a 30% solution by non-solvent-induced phase separation. This process makes it possible to obtain a membrane material with a 240 nm particle rejection of 99.6% and a permeate flow of 1.5 kg/m(2)hbar for contaminated water and 69.9 kg/m(2)hbar for pure water.