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Plasma Treatment of Transparent Plastics for Improved Wear Resistance and UV Stability

Exploitable results

The requirements of the automotive industry to reduce the fuel consumption by using light weight materials and improved aerodynamic design, demand the substitution of glass by transparent plastics (polycarbonate). Due to the poor wear resistance and the lack of chemical resistance a surface protection system for these materials is required. For outdoor applications it is moreover necessary to implement an UV radiation absorbing layer (or substances) in the mechanical protection, to avoid a detachment of the coating, caused by the destruction of the first monolayers of the plastic substrate. During this project the applicability of a Siliconoxide based plasmapolymerized scratch resistant layer in combination with a UV-screen was investigated. The production of polycarbonate head-lamp-lenses with the state of the art process for laquering was chosen, to have a realistic reference to compare to as well from the technical as the economical point of view. The test results showed that a protection system consisting of a Siliconoxide/Ceriumoxide sandwich-layer meets all Standard European and American Regulations with one exception: the weatherability. Improvement of the weatherability seems to be possible by using an improved deposition equipment. A feasibility study showed, that there is a very high application potential for protected polycarbonate not only in transport related industries. An ecological assessment (Life-cycle-assessment) showed a definite advantage of polycarbonate instead of glass for automotive glassing. The economical assessment showed that the costs of the state of the art technique of laquering could not be undercut. The situation changes, when restrictions due to new environmental regulations hit laquering processes and make them more expensive (costs of solvent recycling, expensive disposal of overspray, restricted emission of solvent vapors). For future products, when the protection-layer have to be combined with additional thin layers (e.g. dirt-repellent coatings, decorative layers), which have to be applied in vacuum, the new process may become interesting also for headlamp applications from the economical point of view.