Transmittance of Infrared Radiation Through Fabric in the Range 8-14 μm

Abstract

A mathematical model of measuring transmittance of infrared (IR) radiation through fabric is presented here. Combined with a specially made blackbody, a Fourier transform infrared (FT-IR) spectral radiometer was developed to measure the transmittances of polyester (PET) and cotton fabrics within the range of 8—14 µm at different ambient temperatures. The results showed that the influence of cover tightness on transmittance was much in evidence. For cotton fabric, the transmittance was less than 65 %, but for PET fabric, it was less than 75 %. As expected, IR radiation transmitted fabric easily, but it was limited to some extent. The hairiness in the fabric, especially those made of staple yarns, played an important role in the shading parts of IR radiation. The relationship between transmittance and cover tightness was very complicated for different fabrics (the exponential equation for cotton fabric, the linear function for polyester fabric). Similarly, the exponential relationship between transmittance and fabric thickness, the linear relationship between transmittance and area density could be obtained. The blackbody’s temperature did not have an effect on transmittance below 200 °C.