Effect of Polyvinylidene Fluoride Membrane Production Conditions on Its Structure and Performance Characteristics

Abstract

Poly (vinylidene fluoride) membranes were prepared by freeze-casting. The effects of PVDF concentration, and freezing temperature on the morphology, crystallization, and performance of prepared membranes were examined. Polymer concentration was varied from 10 to 25 wt%. The freezing temperature was varied from −5 to −25 °C. Dimethyl sulfoxide (DMSO) and distilled water were used as solvents and non-solvents, respectively. The first step of this study was devoted to estimating the optimal concentration of PVDF solution in DMSO. Membranes prepared at different ratios were characterized using physical and mechanical characteristics and porosity. The second step was to optimize the time required for the production of the membranes. In the third step, it was shown that the freezing temperature had a remarkable effect on the morphology of the membranes: as the temperature decreases, there is a transition from spherulite structures to interconnected pores. It was shown that the diversity in the pore pattern for PVDF affects remarkably the water permeability through the polymer membrane. During the monitoring of the spread of crystallized areas during the formation of the membrane, it was found that the crystallization of the solvent begins at localized points of the microscale, further crystallized areas spread radially or unevenly along the surface of the solution, forming contact borders, which can lead to changes in the properties of the membrane in its area.

Investigating Permselectivity in PVDF Mixed Matrix Membranes Using Experimental Optimization, Machine Learning Segmentation, and Statistical Forecasting

“…Instead of circular pores, ellipsoidal or elongated pores emerged. This noncircularity arises from heterogeneity in the polymer matrix during the phase inversion process, a phenomenon supported by similar findings in existing literature. − The underlying mechanisms involve nanoconfinement effects and geometric packing constraints, which limit the available free space within the polymer chains and impact the overall membrane structure. The influence of high surface energy from multidimensional nanomaterials (such as nanofibers and nanoparticles) further contributes to this deviation from circularity.…”

“…It also influences the membrane’s surface properties, impacting its fouling resistance. Studies have also indicated that membranes with larger pore sizes, which are associated with higher crystallinity, exhibit reduced nucleation time and increased crystal growth rate. , Prior work analyzed variations in the crystalline conformation of PVDF chains in the PVDF/poly­(methyl methacrylate) blends, where the degree of crystallinity and the molecular mobility in the amorphous phase were quantitatively estimated using the nuclear magnetic resonance spectroscopy . PVDF has been reported to possess several crystalline polymorphs, such as α-, β-, γ-, δ-, ε-, out of which α-, β-, and γ are the dominant conformations.…”

Fabrication and characterization of highly hydrophobic PVDF membrane by phase inversion method with high anti-wettability characteristics

“…PVDF is one of the extensively used polymer for the preparation of micro and ultra-filtration membranes due to its superior chemical, mechanical and heat resistance properties [7]. These advantageous properties of PVDF makes it an attractive candidate for the further fine tuning in the membrane manufacturing process [8].…”