A B S T R A C TA membrane material based on polyamide-imide (PAI) has received a great attention lately due to its thermal resistance, outstanding mechanical property, and low thermal expansion coefficient. In this study, we have focused on the preparation of porous PAI nanofiber membranes (PNMs) for water treatments. The preparation of PNMs was completed via the electrospinning method using PAI in a mixed solvent of dimethylacetamide and tetrahydrofuran. The resulting PNMs were then thermally treated to improve mechanical properties. These PAI-based membranes were characterized by scanning electron microscope, tensometer (tensile strength and elongation), pore characteristic, contact angle analyzer (contact angle), and dead-end cell device (water flux). We noticed that the pore diameter (1.0-0.3 lm) of PNMs was systematically controlled by simply increasing the number of PNMs layers. As these nanofiber membranes were found to be highly hydrophobic, we also attempted to prepare hydrophilic PNMs with a PAI solution containing 2-4 wt.% of diethylene glycol prior to the electrospinng. Based on contact angle tests, these modified PNMs exhibited very hydrophilic characteristics that could be utilized in water-filtration systems.

A B S T R AC TThis paper reports the preparation and characterization of polyvinylidene fl uoride (PVdF) nanofi ber ion exchange membrane for the application in polymer electrolyte membrane fuel cells (PEMFC). The composite membrane of PS/PVdF was prepared by using the electrospinning method with PVdF solution in a mixed solvent of DMAc and acetone by pore-fi lling with a mixture of styrene and PS using DVB as cross-linking reagent. Ion exchange mem-brane (SPS/PVdF) was then manufactured by introducing sulfonate (-SO 3 H) groups using sul-furic acid on the prepared PS/PVdF membranes. The modified membranes were characterized by fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), water uptake, ion exchange capacity (IEC), electrical conductivity and membrane & electrode assembly (MEA). By controlling the content of PS, characteristics comparable to Nafion which has water uptake, IEC and electrical conductivity values suited for the application in PEMFC could be observed in modified membranes. In particular, not only water uptake values (90-550%) were much higher than that of Nafion 115, but also IEC values were more than double the values of Nafion 115. As of the results of electrical conductivity measurements and MEA tests, SPS/PVdF membranes showed the possibility of being an alternative membrane for Nafion 115 due to their improved properties.

In this paper, poly(vinylidene fluoride) nanofiber was prepared by an electrospinning method. Graphene oxide sheets was obtained via filtration from graphene oxide aqueous solution which synthesized by Hummers method. By sonication, a homogeneously dispersed and well distributed poly acylic acid and graphene oxide nanosheets solution were obtained, and this can be used to modify the neat poly (vinylidene fluoride) nanofiber membrane for not only increasing the hydrophilic properties but also improving the mechanical properties. The poly(vinylidene fluoride)/graphene oxide composite membrane was characterized by SEM, FT-IR, pore properties and mechanical properties. The composite membrane showed an appropriate pore size, excellent mechanical property comparing with pure poly(vinylidene fluoride) membrane. The results showed the membrane could be feasibly used as a MF membrane.