Optical-properties of polymer-films for transparent insulation
Commercially available, highly transparent polymer films for transparent insulation applications were investigated systematically as to their relevant optical properties in the solar and infrared wavelength range. The photometric characterisation in the solar range and the calculation of non-spectral, solar optical film properties using models for scattering-absorbing media have shown, that the solar extinction is dominated by scattering occuring mainly at the surface. For various amorphous and semi-crystalline films the root-mean-square surface roughness correlated well with the solar optical thickness. Regarding high infrared absorptance in the wavelength range of about 10 mum the carbon-oxygen single bond is highly effective for commercial materials with maximum service temperatures of about 100 degreesC. For 50 mum thick films of different polymer types with carbon-oxygen single bonds in the molecular structure a good correlation between the concentration of the functional corbon-oxygen group and the non-spectral, infrared optical thickness was found.