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Many polymers, especially those without functional groups like polyethylene PE, polypropylene PP,
polytetrafluoroethylene PTFE etc., need a pretreatment to alter their surface properties in order to improve the adhesion to other materials which are applied by subsequent coating, printing or laminating process steps. Conventional surface modifying technologies (like flame corona 23) or plasma 4.5.6) treatment methods) typically show inherent problems related to aging effects and weak boundary layer formation, leading to a deterioration of adhesion. Additionally, the generated interface is not well defined. A so-called or corona zoo" is generated, comprising various different functional groups like hydroxyl-, carbonyl-, carboxyl, amino-, imino-groups, etc. The basic principle of these technologies is to introduce polar groups to increase surface energy. The improved adhesion to other layers is mostly due to a purely physical interaction or the formation of weak interactions like hydrogen bonds, Van-der-Waals forces or dipolar interactions only. Therefore the adhesion is also relatively weak and cannot withstand strong forces and/or high temperatures as they are often encountered in industrial applications. High temperature resistance is of highest importance whenever sterilization of the polymers is needed as for example for medical materials and for food packaging. Especially for the environmentally clean coating and printing technology of (JV-curing, which generates high quality coatings without the use of solvents and with low energy consumption, adhesion to polymers is mostly very poor. Primers can be used to circumvent the problem, but their use requires additional processing
steps and most of them use solvents and/or less environmentally friendly chemicals. The new approach, which is presented in this lecture, renders the interaction between polymer surfaces and a subsequent coating to a well defined, chemically directed mechanism. The improved adhesion is achieved by the formation of stable covalent bonds between the surface and the applied coating and is especially useful for UV-cured coatings, inks and adhesives.