Surface Reactions of Ethylene-Vinyl alcohol Copolymer and Its Adhesion through Covalent Bonding

Abstract

Isocyanato groups were introduced onto the surface of an ethylene-vinyl alcohol copolymer film by urethanation with hexamethylene diisocyanate. The films having amino groups or gelatin molecules on the surface were prepared by modifying the isocyanato group of the copolymer film. The adhesion through the covalent bonding of the two surface-modified films was studied. When the film with the isocyanato group was lapped over the film with the amino group under a pressure in dry state, no adhesion took place. This may be explained in terms of roughness of the surfaces which prevents the two films from effective molecular contact. When a gelatin-glutaraldehyde mixture was used as an adhesive for bonding the two films, both of which had amino groups, the peel strength was apparentl y higher than that estimated from the experimental error. For instance, the dry peel strength was 30 g⋅cm^-1 when the two gelatin-bound films were bonded with the adhesive. When adhesion was carried out after capping the functional groups, the peel strength became practically zero. The result strongly indicates that adhesion through the covalent bonding occurs between the two films having the functional groups on the surface, if the adhesive, capable of reacting with the groups, is used.