Plasma treatment of polymers for surface and adhesion improvement Dirk Hegemann * , Herwig Brunner, Christian Oehr Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, Nobelstrasse 12, 70569 Stuttgart, Germany Abstract DifferentplasmatreatmentsinarfdischargeofAr,He,orN 2 areusedtoetch,cross-link,andactivatepolymerslike PC,PP,EPDM,PE,PS,PETandPMMA.Duetothenumerouswaysaplasmainteractswiththepolymersurface,the gas type and the plasma conditions must be adjusted on the polymer type to minimize degradation and aging effects. Wetting and friction properties of polymers can be improved by a simple plasma treatment, demonstrated on PC and EPDM, respectively. However, the deposition of ultra-thin layers by plasma enables the adjustment of wetting prop- erties,usingsiloxane-basedorfluorocarbonfilms,andfurtherreductionofthefrictioncoefficient,applyingsiloxaneor a-C:Hcoatings.Nevertheless,theadhesionofplasma-depositedcoatingsshouldberegarded,whichcanbeenhancedby depositing a graded layer. Ó 2003 Elsevier B.V. All rights reserved. Keywords: Polymers; Rf plasma; Aging; Wettability; Adhesion; Friction 1. Introduction Polymersaredistinguishedbytheirlowdensity, flexibility, ease of manufacture, and cost-effec- tiveness. However, their surface properties often do not meet the demands regarding scratch-resis- tance, wettability, biocompatibility, gas transmis- sion, adhesion, or friction. Hence, an additional surface modification is required to achieve the desired properties, while maintaining the charac- teristics of the volume [1]. Primarily, a plasma treatment provides manifold possibilities to refine a polymer surface, enabled by the adjustment of parameters like gas flows, power, pressure and treatment time. Depending on the gas composition and plasma conditions, ions, electrons, fast neutrals, radicals and VUV radiation contribute to the polymer treatment, resulting in etching, activation and/or cross-linking [2,3]. Degradationofpolymersurfacesmainlyoccurs when a rapid interaction with radicals or ions takes place. Here, intensity and duration of the plasmatreatmentareofimportance.Whileashort treatment of PP causes only outer chain scissions, which may lead to improved surface properties, a more intense treatment also yields inner chain scissions, supported also by VUV radiation [4]. Plasma treatment of polymer surfaces causes not only a modification during the plasma expo- sure, but also leaves active sites at the surfaces * Corresponding author. Tel.: +49-711-970-4028; fax: +49- 711-970-4200. E-mail address: hegemann@igb.fraunhofer.de (D. Hege- mann). 0168-583X/03/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0168-583X(03)00644-X Nuclear Instruments and Methods in Physics Research B 208 (2003) 281–286 www.elsevier.com/locate/nimb