The Effect of Diluent Mixture with Upper Critical Solution Temperature on Membrane Formation Process, Microstructure, and Performance of PVDF Hollow Fiber Membrane by TIPS Process

Abstract

Thermally induced phase separation (TIPS) is a technique to prepare commercial membrane. However, the quick polymer crystallization during the quenching process will bring about a dense and thick skin layer and thus decrease permeability markedly. In this paper, a diluent mixture with upper critical solution temperature (UCST) was used to prepare polyvinylidene fluoride (PVDF) hollow fiber membrane. That is, the separation between diluent (propylene carbonate (PC)) and non-diluent (dioctyl terephthalate (DOTP)) occurred during the quenching process when the temperature of the dope was lower than 110 °C. The effects of separation between PC and DOTP and the resulting coalescence of DOTP on the PVDF crystallization process, microstructure, and the permeability of the membranes were analyzed. The results showed that the suitable PC/DOTP weight ratio reduced the thickness of the skin layer near the outer surface markedly and resulted in a porous outer surface, and the microstructure evolution process was proposed. The maximum pure water flux for the prepared membrane is up to 128.5 L·m −2 ·h −1 even in a dry mode without using a hydrophilizing agent. The rejection rate of the carbonic particle is nearly 100%. This study presents a novel and simple way to fabricate the microporous membrane with the interconnected pore structure.

Development of A Novel Corrugated Polyvinylidene difluoride Membrane via Improved Imprinting Technique for Membrane Distillation

“…Meanwhile, PTFE has the best hydrophobicity, chemical and thermal stable yet it is not the best option for MD due to its high thermal conductivity other than relatively expensive material and too stable for modification and functionalization [10,11]. Thus, PVDF received great attention by researchers since it possesses outstanding properties suitable for MD membrane which are high hydrophobicity, high thermal stability, good chemical resistance and excellent mechanical strength [9,12,13].…”

Experimental and theoretical studies on the formation of pure β-phase polymorphs during fabrication of polyvinylidene fluoride membranes by cyclic carbonate solvents

“…For instance, Su et al 32 and Yang et al 33 studied the PVDF membrane formation by using several solvents, including PC. Cui et al 34 studied the effect of diluents mixture (PC/dioctyl terephtalate) on PVDF hollow fiber membrane characteristics. Fang et al 35 used a mixture of PC and diphenyl carbonate for polymer dope solution preparation and PC solution as an extruding solvent for the outer layer to prepare dual-layer PVDF hollow fiber membrane.…”