Effects of mixed diluent compositions on poly(vinylidene fluoride) membrane morphology in a thermally induced phase‐separation process

Abstract

The effects of a mixed diluent (MD) composition [dibutyl phthalate/dioctyl phthalate (DOP)] on poly (vinylidene fluoride) (PVDF) membrane morphology were investigated with scanning electron microscopy, and a bicontinuous morphology could be obtained with MD in a thermally induced phase-separation process. The reasons for the morphology formation were explained according to the effect of MD on the phase diagrams. In addition, the effects of the PVDF concentration on the membrane morphology were examined. For the system with less DOP, the large spherulite morphology was obvious under all investigated concentrations, whereas no large spherulite structure existed in the membrane as the DOP content increased to concentrations other than 20%.

Preparation of polyvinylidene fluoride membrane via a thermally induced phase separation using a mixed diluent

“…In contrast with the previous work, 9 DSC curves shown in Figure 9 still display the multiple melt peaks. However, there is no obvious change in peak temperature site and shape as CBT increases.…”

“…Moreover, with the increase of concentration, the porosity of the whole membrane decreases. By contrast, the membrane in our previous work 9 presented an isotropic structure. This results from the different membrane casting processes.…”

“…This results from the different membrane casting processes. In the previous study, 9 the membrane was formed between two glass slices clipped by two alloyed plates, and thus, the diluent was not easy to evaporate; moreover, the cooling conditions of the top and bottom surface were the same. As a result, the whole body of membrane presented a symmetric morphology.…”

“…It is very difficult to prepare PVDF membrane with good properties by using the TIPS method because few kinds of solvents in industrial products can be selected as the diluent. In our previous work, 9 bi-continuous morphology was obtained by using a kind of mixed diluent (MD)-dibutyl phthalate (DBP) and dioctyl phthalate (DOP); however, the practical properties were not presented because of the membrane samples were too small.…”

Preparation of PVDF/PMMA blend hollow fiber membrane via thermally induced phase separation (TIPS) method

“…It means three peaks in range of 17-20 • were merged together. Merging of these peaks may be the possibility of coexistence of the ␣ and ␥ phases PVDF for fabricated membranes [26]. Table 1 shows the crystallinity of the different membranes before and after acetone extraction.…”