Infrared radiative properties of polymer coatings containing hollow microspheres

Infrared radiative properties of a polymer containing hollow glass microspheres are studied by means of the measurements of directional-hemispherical reflectance and transmittance in the wavelength range from 2.6 to 18 μm. The measurements are performed for several samples containing different series of microspheres of volume fraction from about 6% to 66%. Relatively strong peak of reflectance at the wavelength 4.5 μm was observed. This peak is explained in terms of theoretical model based on Mie theory calculations for single microspheres and modified two-flux approximation proposed recently by the authors. The reflectance of the composite material in the important range from 8.5 to 13.5 μm is determined mainly by rough surface layer of microspheres and it does not described by the model for semi-transparent media. The conditions of a considerable decrease in radiative heat losses from the buildings due to paint coatings containing hollow glass microspheres are discussed.