Measurement of radiative thermal properties of thin polymer films by FTIR

Abstract

Although a number of test methods have been reported for the characterization of radiative thermal properties of semi-transparent materials and textile fabrics, the need for specialized equipment limited the application of these test methods. This paper reports on the use of a conventional instrument, viz. Fourier transform infrared (FTIR) spectroscopy, for the characterization of radiative thermal properties of thin polymer films for application within an intermediate temperature range. Experimental measurements on spectral transmission with FTIR were performed on four types of thin films with high mass fraction, viz. one made of polyethylene (PE), two made of polyamide (NB and NW) and one made of aluminium foil (AF). From the measurements, extinction coefficients were calculated by using Beer's Law, and then the Rosseland mean extinction coefficients and radiative thermal conductivities were determined. The results showed that the thin AF film was the best at blocking radiation, whereas the thin PE film was the weakest. The two polyamide films (NB and NW), made of the same polymer but different in colour, had similar intermediate capability in blocking radiation, indicating colour has little effect on radiative thermal properties of polymeric materials.