Membrane formation of poly(vinylidene fluoride)/poly(methyl methacrylate)/diluents via thermally induced phase separation

Abstract

The role of the single diluents and mixed diluents on the poly (vinylidene fluoride) (PVDF)/poly (methyl methacrylate) (PMMA) blend membranes via thermally induced phase separation (TIPS) process was investigated. The crystallization behaviors of PVDF in the diluted samples were examined by differential scanning calorimetry. The melting and crystallization temperatures of those diluted PVDF blend were decreased with the enhanced interactions between polymer chains and diluent molecules. The crystallinity of PVDF in the diluent was always higher than that obtained in PVDF blend sample. This can be explained by the dilution effects, which increased the average spatial separation distances between crystallizable chains. Thus, the PVDF crystallization was favored. Additionally, solid-liquid (S-L) phase separation occurred in the quenched samples. Illustrated by scanning electron microscopy, inter-and intraspherulitic voids were formed in the ultimate membranes, which related to the polymer/diluent interactions, the kinetics of crystallization and diluent rejection from the growing crystal. The porosity of the PVDF blend membranes obtained from the mixed diluents was higher than those obtained from the single diluent samples.

Preparation of polypropylene microfiltration membranes via thermally induced (solid–liquid or liquid–liquid) phase separation method

“…Nevertheless, the crystallization temperature slightly increases by increasing the PP concentration. As reported, the addition of diluent lowers the chemical potential of the polymer in the solution . So addition of the binary diluent here also lowers the chemical potential, leading to the depression of the crystallization temperature of PP.…”

The Effect of Chain Structures on the Crystallization Behavior and Membrane Formation of Poly(Vinylidene Fluoride) Copolymers

“…During the TIPS process, the liquid-liquid (L-L) phase separation, solid-liquid (S-L) phase separation or a combination of both of these two separations, followed by polymer crystallization, offers great flexibility in controlling the microscopic morphology of polymeric membranes [7,8,9,10,11]. In the membrane preparation by TIPS, selecting a proper solvent is one of the key factors for controlling the pore structure.…”

Formation of an interconnected lamellar structure in PVDF membranes with nanoparticles addition via solid‐liquid thermally induced phase separation

“…As illustrated by the membrane performance,17, 18 a bicontinuous pore structure but poor mechanical properties were obtained, because the L‐L phase separation occurred when the polymer concentration was in the low range. Some researchers incorporated amorphous poly(methyl methacrylate) (PMMA) into PVDF diluted systems and a short L‐L phase separation region was obtained 20, 21. In a U.S. patent,22 the inventor applied a powdery hydrophobic silica as an inorganic filler to PVDF diluted system in which dibutyl phthalate (DBP), dioctyl phthalate (DOP), or mixtures of them were used as diluents.…”