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Plasmagestützte Nanostrukturierung von ETFE-Folie

: Steiner, Cindy

Ilmenau, 2018, 136 S.
Ilmenau, TU, Diss., 2018
Fraunhofer FEP ()
Plasma; Folie; Kunststoff; Oberfläche; Rolle-zu-Rolle

This thesis deals with the investigation of the formation of nanostructures on ethylene tetrafluoroethylene (ETFE) in a plasma etching process. The plasma source was a dual magnetron system with pulsed direct current discharge. Oxygen ions were generated in a pure oxygen plasma and were accelerated to the substrate by the electric field in the cathode sheath. The negatively charged oxygen ions interact with the ETFE surface resulting in formation of stochastic nanostructures. The first part of the thesis deals with the influence of process parameters on the formation of nanostructures. The nanostructures were characterized regarding their anti-reflective (AR) effect as well as structure size, shape and depth. The AR effect was quantified by measuring the increase in light transmittance through the treated films. Increasing the plasma intensity creates deeper structures yielding higher transmission up to a maximum. Further increase of the plasma intensity results in a reduction of transmission. The relationship between plasma intensity, change in optical transmission and structure shape and depth is discussed. Different characterization methods are used to determine geometrical properties of the nanostructures. Limitations in applicability of the methods for describing nanostructured ETFE surfaces are discussed. The orientation of crystalline areas near the polymer surface has significant influence on the formation of nanostructures. In the second part of the thesis, semi-crystalline ETFE was uniaxially stretched resulting in a changed orientation of the crystalline lamellae. The shape, size and pattern of nanostructures were different on stretched ETFE compared to cast ETFE surfaces. A detailed comparison of the dimensions of nanostructures and crystalline areas is given and discussed. Finally, application relevance of the results is demonstrated by showing different ways to enhance optical transmission of polymer webs. The plasma etching process was transferred to polyethylene terephthalate (PET) based on the findings in this thesis. The outdoor stability of a nanostructured ETFE surface is shown using an outdoor weathering test located in central Europe proving the potential of nanostructured ETFE for outdoor applications such as the encapsulation of solar cells.