Determination of Optical Constants of Polymer Films Using a Fourier Transform Infrared Reflection Method; Polyethylene Terephthalate (PET)

The determination of optical constants of polymer films is of interest in the study of surfaces for radiative cooling, photothermal solar energy conversion, solar energy conversion systems, and electric conductors, as well as in the use of evaporated films for space applications. These applications have increased the demand for experimentally straightforward techniques for the determination of optical constants of polymer films in the infrared region. There are several methods available for such determinations. However, the calculations are complicated because of the complex dependence of the optical constants on the transmittance (T), the reflectance (R), and the nature of the substrate.