ULTRAVIOLET LIGHT AS AN EFFECTIVE CLEANING, AND SURFACE PREPARATION PROCESS FOR ADHESIVE BONDING AND PAINTING OF POLYMERS, COMPOSITES AND METALS Michael J. Rich and Lawrence T. Drzal Composite Materials and Structures Center Michigan State University 48824-1226 Email: drzal@egr.msu.edu ; 517-353-5466 ABSTRACT Contemporary vehicles utilize a mix of materials in their construction consisting of metals, plastics, and composites. These materials must possess suitable surface properties to achieve desired performance when these parts are adhesively bonding or painted for field service. Surface preparation methods now in place oftentimes use solvents or caustics, an increasingly unacceptable approach in an era of mounting environmental regulations. New methods of surface preparation are called for that are environmentally benign and economically feasible while meeting the stringent quality standards of the automotive industry. The use of energetic ultraviolet light is emerging as a promising technology to compete with the old methods of surface preparation. This paper reports the utility of using energetic UV light to generate appropriate surface chemical composition on plastics, composites, and metals for subsequent painting or adhesive bonding operations. UV treatments have the potential to replace the old methods of treating assorted materials used in the automotive industry in an environmentally responsible and cost-effective manner. BACKGROUND The worldwide production of passenger and commercial vehicles in 2000 approached 60 million units [1]. The need for increased fuel efficiency has resulted in greater use of plastics and composites alongside traditional metallic materials such as steel and aluminum. Increasingly, the cars of today are composed of a wide variety of raw materials that are required to have suitable surface properties in order to be effectively painted or bonded. The surface preparation of the adherend whether for adhesive bonding or painting requires careful removal of labile organic compounds as well as the addition of chemical functionalities to the adherend surface that can interact strongly with the adhesive. Manufactured polymer, polymer composite and metallic surfaces always contain undesirable compounds or additives that reduce or limit adhesion to the adhesive or paint film. Mechanical surface treatments (e.g. abrasion) are currently used as surface preparation techniques but are time consuming, labor intensive and can damage the polymer composite adherend surface. Furthermore, organic solvents used for surface preparation also are being eliminated in order to reduce volatile organic compound (VOC) emissions[2]. It is desirable to have a surface treatment method that can both clean a surface as well as create a beneficial chemistry for optimum adhesive bonding of polymer composites[3]. One environmentally acceptable alternative under study is the use of energetic ultraviolet light to clean and prepare metallic and non-metallic surfaces for painting or bonding.