Optical and Thermal Properties of Paints Mixed with Metal-Coated Glass Flakes

Abstract

We focused on the development of paints with low infrared emissivity and low thermal conductivity. To achieve the goal, glass flakes coated with copper or silver were selected as additives. These were mixed in commercially available phthalic acid resin paint, and ordinary painting was carried out. The spectral infrared emissivity of metal-coated glass flakes added paints decreased to 0.75 or less. Particularly, for the 20 wt% Ag-coated glass flakes added paint, it was very effective as 0.37 in the middle infrared ray (4.5 μm) and 0.55 in the far infrared ray (11.5 μm). And the thermal conductivity also fell very well. The values of the 20 wt% Ag-coated glass flakes added paint and 20 wt% Cu-coated glass flakes added paint were 0.11, 0.08 [Wm⁻¹K⁻¹] respectively. That is, by adding metal-coated glass flakes to the paint, we succeeded in reducing both infrared emissivity and thermal conductivity. Further, the specular reflectance (5° incidence) of infrared rays was very low at around 0.03 to 0.04, which was almost the same value as the base paint. From the microscope observation, the glass flakes were stacked and clogged. This would have resulted in the above performance.