Optische und mechanische Charakterisierung des Alterungsverhaltens von Materialien für die Anwendung in konzentrierenden Solarkollektoren

Translated title of the contribution: Optical and mechanical characterisation of the aging behaviour of materials used in concentrating solar-collectors

Bettina Ottersböck

Research output: ThesisMaster's Thesis


The growing demand for energy and the emission of pollutants to the atmosphere cause an increasing significance of regenerative and clean energy sources. As one of such energy sources the sun has an enormous potential. To utilize this energy type big-scaled and cost-saving, solarthermal power plants are used. As a ressource-saving alternative to conventional collectors, pneumatic pre-stressed concentrators are used. These so called HELIOtubes, produced by the company Heliovis (Wr. Neudorf, A), are completely made of polymer films. However, this technology is still in developement. The aim of this work was to identify and characterize suitable materials for HELIOtubes. Thereby three different films have to be distinguished – an upper transparent, a middle reflective and a bottom robust film. As upper transparent layer fluorpolymers were chosen. In order to fulfill optical and mechanical requirements a multilayerfilm with metallic reflective-layer as middle reflective film was selected. In terms of the robust film there are only demands concerning the mechanical properties. That is the reason why a woven fabric-matrix materialwas chosen. In the course of the optical and mechanical characterisation eleven materials were tested, thereof six were transparent, two reflective and three robust films. As characterisation methods Fourier-Transformation-Infrared (FT-IR)-, Ultraviolett/Visible light/Near-Infrared (UV/Vis/NIR)-spectroscopy and tensile testing at application relevant temperatures were used. After base characterisation, the UV stability of selected materials was tested using a fluorescence device in which the films were artificially weathered up to 1 440 hours. Considering the optical criterium all transparent materials were adequate for the use in HELIOtubes. The mechanical characterisation indicated that the tetrafluoroethylenehexafluoropropylene-vinylidenefluoride-terpolymer (THV)-material was not suitable as HELIOtube-material due to the low yield stress above room temperature. Consequently THV was excluded of artifical weathering. All other materials showed no significant weathering-influences. In conclusion tetrafluoroethylene-hexafluoropropylene-copolymer (FEP) meets the requirements of Heliovis, however, best qualified is one of the ethylenetetrafluoroethylene-copolymers (ETFE). The two reflective-films showed contrary behaviour during testing. Film 1 indicated good reflectance and failed very brittle during the tensile testing without significant temperature influences. On the other hand reflector-film 2 showed less reflectance. The substrate layer with the metallic reflective layer failed also brittle, but in contrary the thermoplastic-polyurethane (TPU)-backsheet failed very ductile. After artificial weathering a deterioration of optical and mechanical properties could be observed for both materials. Due to the very brittle failure of film 1, material 2 is more applicable despite the worse reflective properties. All woven fabric-matrix-materials showed brittle material behaviour. Because of strong delaminations between tissue- and matrix-layer the TPU- 1 material was not qualified for artifical weathering. Concerning the PE-tissue-matrix-material, no significant changes due to artificial weathering were observed. By contrast, TPU2 showed yellowing and a significant deterioration of the mechanical performance. Due to the results generated the PE-tissuematrix-material is most qualified as HELIOtube-material.
Translated title of the contributionOptical and mechanical characterisation of the aging behaviour of materials used in concentrating solar-collectors
Original languageGerman
  • Pinter, Gerald Gerhard, Supervisor (internal)
  • Oreski, Gernot, Supervisor (external)
Award date30 Mar 2012
Publication statusPublished - 2012

Bibliographical note

embargoed until 01-03-2017


  • fluoropolymer
  • mechanical characterisation
  • optical characterisation
  • aging
  • tensile testing
  • solar thermal power plants

Cite this