Preparation and characterization of polyamide thin-film composite (TFC) membranes on plasma-modified polyvinylidene fluoride (PVDF)

The use of polyvinylidene fluoride (PVDF) membrane as a support substrate layer for making a polyamide thin-film composite (TFC) has been hindered by the hydrophobic nature of PVDF. In this study, low temperature plasmas were used to treat a commercial PVDF membrane in order to improve its hydrophilicity and make it suitable for fabrication of a polyamide-polyvinylidene fluoride thin-film composite (PA-PVDF) membrane. The plasma treatment used oxygen, methane, or their 1:1 mixture gas to produce glow discharge for treatment and surface modification of the PVDF membrane. The membrane surfaces were characterized using water contact angle measurements, X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FE SEM). Pure water permeability and salt rejection tests were performed to evaluate the performance of the resulting PA-PVDF. Our experimental results indicated that plasma treatment of PVDF membrane could significantly reduce its water contact angle and thus produce a hydrophilic surface that could be then used as the support substrate layer for the fabrication of TFC membrane through interfacial polymerization. Our experimental results also demonstrated that PA-PVDF membrane supports not only demonstrated higher pure water permeability, but also higher salt rejections than those of TFC membrane with polysulfone as the support.