Industrial processing of polymers by low-pressure plasmas: the role of VUVradiation

The use of low-pressure plasmas for materials processing, pioneered by the semiconductor industry since the 1960s, is now also a commercial reality in technologies which make extensive use of plastics (automotive, aerospace, packaging, pharmaceutical, textile, and other industries). A large fraction of these processes involve the surface modification of polymers for improv ed adhesion, and many of these use air or oxygen plasma to incorporate pola r functional groups into the polymer surfaces. Interaction mechanisms betwe en a plasma and a polymer surface are very complex, for they include synerg istic effects of physical bombardment by energetic particles and by ultravi olet photons, and resulting chemical reactions at and below the surface. In this article we present an overview of plasma surface modification of po lymers, in which rye identify the main variables for process control, illus trated by examples. We then show, on hand of a series of specially designed experiments, how the effects of ultraviolet photons generated in the plasm a can be assessed separately from those of other energetic and reactive spe cies, especially in the case of oxidizing plasmas. Finally, we comment on t he merits and drawbacks of industrial plasma processes in comparison with o ther competing technologies, especially those based on ultraviolet radiatio n. (C) 1999 Elsevier Science B.V. All rights reserved.