INTRODUCTION OF FUNCTIONAL-GROUPS ON POLYETHYLENE SURFACES BY A CARBON-DIOXIDE PLASMA TREATMENT

Poly(ethylene) (PE) films were treated with a carbon dioxide (CO2) plasma to study the formation of oxygen-containing functional groups at the surface. Modified and nonmodified films were characterized by X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. During the CO2 plasma treatment, the PE surface is etched and oxidized, yielding films with a very hydrophilic surface. The oxygen incorporation at the surface is fast and can be described by a combination of a zero-order incorporation and a first-order etching process. Several oxygen functionalities such as carboxylic acid (approximately 14% of the oxygen present), ketone/aldehyde (25%), and hydroxyl/epoxide (5-9%) groups were introduced at the surface by the plasma treatment. This was shown by using derivatization reactions for specific functional groups followed by XPS analysis. The wettability of the plasma-treated surfaces decreased when the films were stored for prolonged periods of time in air. This aging process could not be completely reversed by immersion of the films in water. (C) 1995 John Wiley and Sons, Inc.