Fabrication of Polyamide-6 Membranes—The Effect of Gelation Time towards Their Morphological, Physical and Transport Properties

Porous polyamide-6 membranes were fabricated via a non-solvent induced phase inversion method, and the influence of gelation time on the properties of the membranes was investigated. Membrane samples with various gelation times were prepared. The evaluation of the membranes’ properties was carried out by various analyses and tests, such as scanning electron microscopy, atomic force microscopy, contact angle, wet and dry thickness, mean pore size measurements, porosity, water uptake, mechanical resistance, hydrodynamic water fluxes, membrane hydrodynamic permeability, and retention testing. The scanning electron microscopy images (both surface and cross-section) demonstrated that the increase in gelation time from 0 (M(0)) to 10 (M(10)) min led to the morphological change of membranes from isotropic (M(0)) to anisotropic (M(10)). The wet and dry thickness of the membranes showed a downward tendency with increasing gelation time. The M(0) membrane exhibited the lowest bubble contact angle of 60 ± 4° and the lowest average surface roughness of 124 ± 22 nm. The highest values of mean pore size and porosity were observed for the M(0) sample (0.710 ± 0.06 µm and 72 ± 2%, respectively), whereas the M(10) membrane demonstrated the highest tensile strength of 4.1 MPa. The membrane water uptake was diminished from 62 to 39% by increasing the gelation time from 0 to 10 min. The M(0) membrane also showed the highest hydrodynamic water flux among the prepared membranes, equal to 28.6 L m(−2) h(−1) (at Δp = 2 bar).