Corona Treatment: An Overview, 1994 Polymers, Laminations & Coating Conference Proceedings
D. A. Markgraf
Why surface treatment is necessary-
Generally, plastics including extrusion coatings have chemically inert and nonporous surfaces with low surface tensions that cause them to be nonreceptive to bonding with substrates, printing inks, coatings, and adhesives. Polyethylene and polypropylene are the lowest in surface tension of the various plastics and are the two materials most often subjected to surface treatment to improve their bolding characteristics (1, 2, 3). Surface treatment, however, is not limited to these two materials and can be used to improve the bonding ability of virtually all plastic materials as well as some nonplastic materials. The two nonplastic materials most often subjected to surface treatment are foil and paper. All substrates—plastics, films, paper, and foils—provide a better bonding surface for extrusion coatings when they are treated just prior to entering the chill-roll nip. This application of surface treatment is referred to as pretreatment. Surface treatment is also frequently used to enhance adhesion to the surface of other converting processes, i.e., printing, adhesive lamination, etc.