Phase-Field Simulation of the Effect of Coagulation Bath Temperature on the Structure and Properties of Polyvinylidene Fluoride Microporous Membranes Prepared by a Nonsolvent-Induced Phase Separation

Abstract

We used the phase-field model of the existing Nonsolvent Induced Phase Separation (NIPS) method to add the variable of temperature in simulating the changes in the process of membrane formation. The polyvinylidene fluoride (PVDF) membrane system was applied to examine the influence of coagulation bath temperature change on the skin-sublayer of the membrane structure, thereby elucidating the development process of membrane structure under different conditions and shedding light on the most suitable coagulation bath temperature ranges. It was found that as coagulation bath temperature increased, the number of interface pores in the outer skin layer decreased, but the size increased. As a result, it changed from the crack shape to round-hole shape, thus making the pore structure looser. In the sublayer, the mesh support structure was increased, which enhanced the mechanical strength of the membrane. Relevant experiments also verify the effectiveness of the model.

Ternary Phase-Field Simulation of Poly(vinylidene fluoride) Microporous Membrane Structures Prepared by Nonsolvent-Induced Phase Separation with Different Additives and Solvent Treatments

“…The simulation results show that with an increase in the PEG concentration, the delayed skin layer time increases and the cortex becomes thicker and denser. According to Fang et al, , a PVDF concentration of 18 wt % has a dense cortex and produces a dense granular phase, which leads to an increase in the concentration of the casting liquid. The liquid–solid phase is more likely to occur after the addition of PEG, so the porous structure caused by liquid–liquid phase separation does not exist.…”

Connecting Structural Characteristics and Material Properties in Phase-Separating Polymer Solutions: Phase-Field Modeling and Physics-Informed Neural Networks

“…In this work, the evolving morphology in 2D is described by the Cahn–Hilliard model [ 50 ] for the spatial and temporal variations of the substance, where represents the volume fraction of the substance i , is its chemical potential, is the mobility, is the surface tension parameter, is the total surface area, is the total free energy, and is the free energy density. The mobility may be concentration-dependent due to inter-species diffusion but is generally assumed as a constant in literature [ 15 , 16 , 49 , 51 ]. Moreover, although different formulations of mobility change the scaling of the domain growth law, the morphological features are not significantly impacted [ 52 ].…”

“…The model accounts for the interfacial energy between different phases through variational formulations, guiding the system toward equilibrium by minimizing the interfacial energy by aggregating the same phases. The versatility of the Cahn–Hilliard model has made it a valuable tool for studying various systems, including polymeric multicomponent systems under different temperatures and compositions [ 15 ], those involving dynamic flows [ 16 ], bubble motion [ 17 ], elastic materials [ 18 ], and more [ 19 , 20 , 21 ]. However, it is worth noting that investigations into the impact of system parameters on the resulting morphology have often been conducted separately, with only a few comprehensive studies comparing the relative influence of the parameters [ 22 , 23 , 24 ].…”

Microstructure and performance modification of PVDF ultrafiltration membrane via adjusting the composition of coagulation Bath

“…This is due to the fact that membranes with different physical shapes exhibit different separation properties and strengths. 13 Membranes with macroporous and loose structure exhibit high water flux but poor pollutant separation performance and strength, whereas membranes with dense microporous structures demonstrate the opposite characteristics. 14 Previous research indicated that solvent and nonsolvent mixing played an important role in membrane pores and sub-layer microstructures.…”

“…The deformation of UF membranes is a widely debated topic, especially with regard to the influence of membrane microstructure. This is due to the fact that membranes with different physical shapes exhibit different separation properties and strengths 13 . Membranes with macroporous and loose structure exhibit high water flux but poor pollutant separation performance and strength, whereas membranes with dense microporous structures demonstrate the opposite characteristics 14 .…”