Comparative evaluation of the infrared transmission of polymer films

The total infrared (IR) transmission of polymer films is a very important property in engineering, which determines their suitability for a specific application at a given temperature level. Aiming to investigate the total IR transmission of various polymer material films of a particular thickness, an analysis is developed for the comparative evaluation of this very important physical property. Excitation of the radical bonds in randomly oriented, long chain polymer molecules by absorption of IR radiation usually causes a large number of sharp resonances at various wavelengths and is responsible for the characteristic shape of the spectral transmission plot for the particular polymer material. The comparative presentation of results shows that at least as far as the accuracy of the available data is concerned, the total transmission of a polymer film is determined by the specific spectral transmission characteristics of the material and may vary remarkably as a function of the radiant source temperature. According to the derived results, polymer films made of materials like plexiglass, mylar, kapton and fiberglass appear to be remarkably less transparent than other film materials like polypropylene or, even more, polyethylene, which are remarkably transparent, almost uniformly, within the wavelength region under consideration. This certainly determines the potential of the particular films for use in a specific application like the design of solar collector glazing systems or convection suppression windscreens in radiative cooling panels. (C) 2003 Elsevier Ltd. All rights reserved.