Enhancement of hydrophilicity of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane using various alcohols as nonsolvent additives

Flat sheet asymmetric polymeric membranes were prepared from homogeneous solution of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) by phase inversion method using N-methyl-2-pyrrolidone (NMP) as solvent and PEG 6000 as pore forming agent. The effects of addition of different alcohols viz. methanol, ethanol, n-propanol, n-butanol and various quantity of methanol in the casting solution on membrane properties were investigated. The morphology and structure of resulting membranes were observed by field emission scanning electron microscope (FESEM). The permeation performances of the membranes were evaluated in terms of pure water flux (PWF), hydraulic permeability and solute rejection capacity. Extent of membrane hydrophilicity was evaluated in terms of porosity, equilibrium water content (EWC) and water contact angle. Solution of bovine serum albumin (BSA) of molecular weight 68,000 Da was used to study the permeation performance of prepared membranes using a batch cell of 350 mL capacity. Membranes with 5 wt.% of methanol showed highest PWF and smallest water contact angle, while membranes containing different alcohols have almost same PWF.