Formation of a bicontinuous structure membrane of polyvinylidene fluoride in diphenyl ketone diluent via thermally induced phase separation

Abstract

The polyvinylidene fluoride (PVDF)-diphenyl ketone (DPK) mixture was studied as a new system to prepare PVDF membranes via thermally induced phase separation (TIPS). The phenomena of liquid-liquid phase separation was found in this mixture when the temperature of mixture was decreasing and the PVDF concentration was less than 30 wt %. Using DPK as diluent, PVDF membrane with bicontinuous structure was obtained without necessity to add a nonsolvent or a stretching process further. The phase diagram of PVDF-DPK system was also constructed to help investigate the effect of PVDF concentration and coarsening temperature on morphology of resulting membrane.The experiments showed that high coarsening temperatures and low PVDF concentrations resulted in the formation of the large pore size membrane. The strength of the wet membrane was decreasing with decreasing PVDF concentration. On condition that the PVDF concentration was larger than 30 wt %, thermally induced solid-liquid separation occurred and bicontinuous structure disappeared.

A poly(sulfobetaine) hollow fiber ultrafiltration membrane for the treatment of oily wastewater

“…(2015) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] www.deswater.com doi: 10.1080/19443994.2015.1042056 wastewater [3]. UF membrane can remove essentially all free and dispersed oil from wastewater, and the permeate is consistently able to meet Oil and Gas Standards for discharge [2][3][4][5][6].…”

Formation of a bicontinuous structure membrane of polyvinylidene fluoride in diphenyl carbonate diluent via thermally induced phase separation

“…As shown in Figure 1, the polymer concentration on the monotectic point of PVDF/DPC system was approximately 56 wt %, which was much higher than that of PVDF/DPK system (<30 wt %). 15 However, in this work, PVDF could not form homogeneous blends with DPM below the boiling temperature of DPM (534 K). This could be explained by different compatibility between the polymer and the diluent molecules, which could be analyzed by the view of the molecular structure of the diluents as follows.…”

“…15 A small piece of the solid sample was sandwiched between a pair of glass microscope coverslips with silicone rubber around to limit diluent evaporation during the experiment. It was then placed on a hot stage (Linkam THMS 600) at 493 K for 5 min, after that the sample was cooled to 373 K at a constant rate of 10 K/min.…”

“…14 Most of the PVDF/diluent systems underwent solidliquid phase separation (polymer crystallization) and got the fuzzy spherulitic structure at the PVDF concentration studied. In our preceding work, 15 the application of diphenyl ketone (DPK) as a new diluent for the preparation of microporous PVDF membrane via TIPS method was discussed. The phenomenon of liquidliquid (L-L) phase separation was found in this system and a bicontinuous structure was obtained when the temperature was decreasing and the PVDF concentration was less than 30 wt %.…”

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.…”