Effect of Pigment Kinds on the Solar Heat Reflection Characteristics of Paint Film in Visible and Near-Infrared Ray Area

Abstract

In recent years, the global warming has been recognized as a serious problem throughout the world. In Japan, various global warming control technologies for slowing the global warming are being applied and verified. The high reflectance surface for structures has got a great deal of public attention as a promising technology that mitigates the heat island phenomenon which is a cause of the global warming. It is considered that the heat island phenomenon is generated by the temperature rise due to the heat release from the buildings which have a high heat absorptance and are warmed by the solar radiation during the daytime. Applying with solar heat high reflectance paint to the exterior surfaces of urban structures would suppress the increase in temperature, and make possible mitigating of the urban heat island. Solar heat high reflectance paint is composed of various raw materials to enhance the reflection in visible and near-infrared ray. This paper describes solar heat reflectance characteristics of the paint film by varying thickness of film, formulation of paint (pigments by binder mass ratio ; P/B) and kinds of pigments which are uesd for colorling structures in white, black, blue, red, and yellow. The conclusions obtained from this study are as follows : 1) With the increase in P/B, solar reflectance of paint films used organic pigments are devided into two groups. One is not influenced with the increase of P/B and the other is increased with the increase of P/B. The solar transmittance of paint films with most organic pigments is decreases with the increase of P/B. The solar reflectance and the solar transmittance of paint films with inorganic pigments are not influenced with the increase of P/B. 2) The solar reflectance is not influenced by the thickness of paint film and the solar transmittance decreases with the increase of thickness of paint film.