SURFACE CHARACTERIZATION OF ETHYLENE VINYL ALCOHOL COPOLYMER MEMBRANES PREPARED UNDER VARIOUS CONDITIONS

Surface characteristics of EVA membranes were investigated using ESCA. The membranes were prepared by dipping polymer solution cast on various substrates into a coagulation bath (the phase-inversion method). The ESCA results demonstrated that there were significant differences in the surface composition of EVA membranes prepared under various conditions. The more hydrophobic the substrate, the more the substrate side surface was enriched in the ethylene component. Thus the surface characteristics can be controlled by the kind of the substrate without changing the membrane structure such as pore size. For membranes subjected to hot water treatment, the composition of the substrate-contacting surface gradually approached that of the water side surface with increasing temperature. These results suggest that the ethylene and vinyl alcohol components migrated in order to lower the surface free energy at the surface of the membrane.