Poly(ethylene terephthalate) phase inversion membranes: Thermodynamics and effects of a poor solvent on the membrane characteristics

Abstract

Poly(ethylene terephthalate) (PET) is a worldwide established polymer that has raised the interest of researchers for the fabrication of membranes. Polymer membranes are mostly prepared by the phase inversion technique, but the literature is scarce regarding the use of PET for this purpose. The main objective of this work is to prepare PET membranes by the phase inversion technique and characterize the phase separation phenomena and the performance of membranes produced under different solution conditions. The cloud point tests showed that the addition of dichloromethane (DCM) in PET solutions with trifluoroacetic acid (TFA) turned the system more unstable because less water was necessary to promote phase separation. The poor solvent DCM neither affects the chemical structure of membranes nor the surface wettability. SEM images revealed a porous and sponge‐like structure with a thin top layer and the poor solvent seems to suppress the tear‐like macrovoid formation. Filtration experiments indicated higher pure water flux for membranes prepared with DCM in the solution but lower selectivity for model solutes.

Microstructure and performance modification of PVDF ultrafiltration membrane via adjusting the composition of coagulation Bath

“…A three‐phase diagram relying on the cloud points was plotted (Figure 7) to reflect the thermodynamic stability of the cast membrane liquid system. As shown in Figure 7, the gel point of the PVDF/DMF/water system was closer to the polymer–solvent axis, which was attributed to the fact that PVDF has the lowest affinity for water 65 . That is, the cloud point of the PVDF/DMF system appeared earlier in the WB.…”

“…As shown in Figure 7, the gel point of the PVDF/DMF/water system was closer to the polymer-solvent axis, which was attributed to the fact that PVDF has the lowest affinity for water. 65 That is, the cloud point of the PVDF/DMF system appeared earlier in the WB. Only a small amount of water could render the system thermodynamically unstable and cause local precipitation.…”