Ink adhesion on corona‐treated polyethylene studied by chemical derivatization of surface functional groups

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Abstract
Corona discharge (CD) treated polyethylene films were examined using X‐ray photoelectron spectroscopy (XPS) and a variety of chemical derivatization techniques. The composition of the CD‐treated surfaces were found to be relatively unaffected by aging at temperatures between 70 and 80°F. Ink adhesion testing of films treated under progressively more serve conditions indicated the efficiency of adhesion varied directly with the severity of treatment. Derivatization of CDtreated polyethylene films with pentaflurophenylhydrazine (PFPH) resulted in the formation of a stable hydrazone complex. The PFPH complex extends the detection limit for enolizable carbonyl groups ca. eight‐fold and provides relative quantitation of the number of these groups on variously treated polyethylenes. Formation of the hydrazone complex destroyed ink adhesion, indicating that the complex had blocked the site responsible for chemical bonding to the ink. Adhesion of water‐soluble printing inks to CD‐treated polyethylene is a direct consequence of hydrogen bonding between enolic hydroxyls on the polymer surface and carbonyl groups of the ink.