Multifunctional hydrolyzed EVA membranes with tunable microstructure and water barrier properties

A new functional membrane based on poly(ethylene-co-vinyl acetate) (EVA) and poly(ethylene-co-vinyl alcohol) (EVOH) was obtained by hydrolysis reaction on both surfaces of an EVA film, and as a result a three-layered structure (EVOH/EVA/EVOH) was formed. The chemical modification of the film and the thickness of hydrolyzed layer were controlled by FTIR and fluorescent microscopy measurements, respectively. The influence of the hydrolysis time (th) on the thermal properties and membrane microstructure, studied by thermal analysis and X-ray diffraction measurements, indicated the evolution from the amorphous state to the semicrystalline one. The impact of the microstructure modification on the water transport properties was evaluated by permeability and sorption measurements. The plasticization effect of the three-layered membrane was found to be 2 times higher than that in the case of the completely hydrolyzed membrane (th>72h). Such behavior was related to the amorphous/crystalline state of EVOH in the membrane. The results of water sorption measurements indicated that the water desorption is delayed at the highest temperatures in the case of the three-layered membranes. A strong correlation between the water properties of the hydrolyzed EVA membranes and the EVOH structure was observed. In addition, to providing details on structural characteristics of the three-layered multifunctional membrane with tunable water barrier properties, some possible applications where controlled moisture is necessary (such as food packaging or proton exchange fuel cell membrane) were discussed. [Display omitted] •Study of the surface hydrolysis of the EVA films.•Influence of the hydrolysis time on the polymer microstructure (amorphous/semicrystalline).•Three-layered EVOH/EVA/EVOH multifunctional membrane with tunable water barrier properties.•Two times higher plasticization effect in the case of three-layered membrane than in the case of the EVOH film.