Layered Poly(ethylene-co-vinyl acetate)/Poly(ethylene-co-vinyl alcohol) Membranes with Enhanced Water Separation...

A three-layered membrane based on poly(ethylene-co-vinyl acetate) (EVA) and hydrolyzed EVA-poly(ethylene-co-vinyl alcohol) (EVOH), was elaborated by the surface hydrolysis of a dense EVA membrane. Because of the chemical modifications, the three-layered EVOH/EVA/EVOH membrane was characterized by the particular microstructure (amorphous EVA and semicrystalline EVOH) and the tunable hydrophilic/hydrophobic balance. Also, these modifications led to the membrane with the selective barrier properties compared with the pure EVA and completely hydrolyzed EVOH membranes. The water barrier behavior was related to the strong hydrogen-bond interactions of water and vinyl alcohol groups, whereas the weak chemical interactions were revealed for gases (N₂ and O₂). Furthermore, the influence of the polymer rubbery or glassy state on the permeation kinetics was established. In the case of the three-layered membrane, the considerably high selectivity values were obtained for H₂O/O₂ (∼11 900) and H₂O/N₂ (∼48 000) at 25 °C. In addition to these highly selective properties, the three-layered structure does not present delamination features due to its elaboration procedure. Thus, these new layered membranes are very promising as selective materials for the water and gas separation and can be potentially used in food packaging or for the gas dehydration.