2.6. Characterization of SAN Nanofiber Membranes

The morphology observation was conducted by a scanning electron microscope (SEM) (Seron technology, Gyeonggi-do, Korea). Membrane samples were coated with gold before the SEM test. The fiber diameter of the fabricated samples was measured using Digimizer software, and an average of 100 measurements was reported. The membrane surface pore size was measured using the same software; then, the mean and maximum pore size was reported.

The porosity of the SAN samples was measured before and after soaking in IPA, and the pre-measured samples were weighed before and after wetting. The full description of the applied method can be found in the literature [40]. Membrane thickness was measured using an accurate digital micrometer and five measurements were conducted and mean value reported.

A custom-made set-up was used to measure the liquid entry pressure (LEP) of water. The samples were fastened between two semi-cells, and by helping the pressure of nitrogen, the pressure of the deionized (DI) water was increased step by step. The pressure where the water droplets were firstly seen on the membrane surface is regarded as the LEP value. The tests were repeated three times to ensure their reproducibility.

The water contact angle (WCA) of SAN membranes was assessed using a drop shape analyzer (KRUSS analyzer-G10 Drop Shape Analyzer, Germany). Glass slides were used to fix the sample on the holder, and 2 µL DI water was gently placed on the surface. The average value of three tests was then reported.

The mechanical properties were evaluated by a tensile testing device (Model 5566, Intron dynamometer, Buckinghamshire, UK). The load and stretching speed were 50 N and 5 mm/min, respectively. To conduct the tests accurately, the samples were strengthened with two rectangular cardboard frames, and the frame was scissored from both sides before the test.