ADHESIVE-FREE ADHESION OF GRAFTED SURFACES WITH DIFFERENT WETTABILITIES

A polyester film surface was graft-polymerized with various water-soluble monomers by a combination of plasma pretreatment and photoirradiation. The grafted surfaces showed strong adhesion to another non-grafted or grafted film when brought into direct contact in the presence of water and subsequently dried. The adhesion force depended on the hydrophilicity of the adhering surfaces and the graft density. The film having a larger graft density generally showed stronger adhesion in the final stage of drying, but it took longer to achieve high adhesion because of the larger amount of water existing in the interfacial region between the two surfaces. On the other hand, substantial adhesion was obtained almost instantaneously upon contact when one was grafted with an anionic polymer and the other grafted with a cationic polymer. Adhesion between similarly charged surfaces was very weak at the beginning of drying, probably because of the electrostatic repulsion between the charged groups.