Preparation of microporous PVDF membrane via tips method using binary diluent of DPK and PG

Abstract

Microporous polyvinylidene fluoride (PVDF) membrane was prepared via thermally induced phase separation (TIPS) method using a binary diluent of diphenyl ketone (DPK) and 1,2-propylene glycol (PG). The phase diagram for the PVDF/binary diluent of DPK and PG system was measured in the range of the PG/DPK mass ratio changing from 0 to 2/3. Then the effects of the PG/DPK mass ratio and the PVDF concentration on membrane cross-section structures and tensile strength were also investigated. The results showed that the addition of PG brought about a shift of the cloud point curve to a higher temperature and the extension of the liquid-liquid phase separation region to a higher polymer concentration. Therefore a bicontinuous cross-section structure was obtained when the PG/DPK mass ratio was 3/7 and the polymer concentration was 30 wt %. As an increase of the PG/DPK mass ratio, the tensile strength increased gradually at a fixed PVDF concentration. Moreover, for the same PG/DPK mass ratio, the cross-section microstructure changed from a bicontinuous or a cellular structure to a spherulitic structure, and the tensile strength increased drastically as the polymer concentration increased from 20 to 50 wt %.

Surface anti-biofouling control of PEGylated poly(vinylidene fluoride) membranes via vapor-induced phase separation processing

“…Phase separation processes are extensively used to prepare PVDF membranes as well [13][14][15][16], but to the best of our knowledge, VIPS process has never been tried and reported before to prepare low-biofouling PVDF membranes. Yet, the slowness of mass transfers at the gas-liquid interface allows an outstanding control and tuning of membrane formation as long as the important parameters are well controlled and properly chosen [17][18][19][20][21][22].…”

Investigation on the membrane formation process of polymer–diluent system via thermally induced phase separation accompanied with mass transfer across the interface: Dissipative particle dynamics simulation and its experimental verification

“…During the TIPS membrane formation process, a homogeneous polymer solution at a high temperature is cast into a desired shape and then immersed in a coagulation bath at a low temperature to induce phase separation and solidification. Therefore, the heat transfer and the mass transfer across the interface between the polymer solution and the coagulation bath are both very important for the phase separation process and the ultimate membrane morphology [14][15][16][17][18]. In the previous studies, the methodology has investigated the dynamics of phase separation for a polymer-dilute system after a quench but has not included the interface between the polymer solution and the coagulation.…”

Bicontinuous and cellular structure design of PVDF membranes by using binary solvents for the membrane distillation process

“…Tang et al introduced a binary solvent of diphenyl ketone (DPK) and 1,2-propylene glycol (PG) to control the mechanisms of the phase separation, and the bicontinuous cross-section structure was obtained when the PG/DPK mass ratio is 3/7 and the polymer concentration is 30 wt%. 9 Zhou et al employed a binary solvent of dibutyl phthalate/dioctyl phthalate (DBP/DOP) to prepare PVDF hollow ber membranes via a TIPS process, and found that the membrane morphology changed from spherulite structure to uniform interconnected sponge-like structure when the weight ratio DBP to DOP was changed. 10 Song et al used a binary solvent consisting of DBP and dibutyl sebacate (DBS) to fabricate PVDF membranes, and found that the morphology of the membrane cross-section changed from spherulitic to bicontinuous structure as the DBS mass fraction increased in the mixed solvent.…”

“…The defects caused by the NIPS process resulted in unsatisfactory mechanical properties, which are detrimental to long-term practical application especially at high temperature. The thermally induced phase separation (TIPS) method, 9 by contrast, is a promising approach for preparing porous membranes due to several accepted advantages, such as fewer inuencing factors, easy operation, uniform pore size distribution, high porosity, excellent mechanical properties and so on.…”

“…Following the disciplines outlined above, we have selected four solvents for PVDF membrane fabrication by TIPS method, the parameters of which were listed in (8)(9) and DOP (5.3), DOA (4)(5) and DOS (<4) demonstrated a great difference in polarity. Therefore, the poor compatibility between PVDF and the other three solvents were characterized and listed in Table 1.…”