Structure-property correlations of polymeric films for transparent insulation wall applications. Part 2: Infrared optical properties

In this paper the results of a research project to establish a fundamental understanding of the physical relationships between the material structure and the infrared optical properties of polymeric transparent insulation (TI) materials are described. First, a systematic characterization of potential materials for TI applications in respect to their relevant physical properties in the infrared radiation range was done. Second, based on the investigation of polymer films with different thicknesses model functions for the infrared optical properties were established. Third, the infrared optical properties were interpreted on base of polymerphysical relations. The characterization in the infrared range and the calculation of infrared optical film properties have revealed, that various functional groups of the macromolecular structure are highly absorbing. For polymers with service temperatures of about 100 °C the carbon-oxygen single bond was identified as highly effective. For 50 μm thick films a good correlation between the concentration of the functional carbon-oxygen group and the non-spectral infrared optical thickness as well as the hemispherical emittance was found. An outstanding performance profile for TI wall applications with black absorbers was obtained for cellulose based materials.