Modified Kubelka's layer model for calculation of infrared properties of low emissivity coatings with optically-rough surface

A Modified Kubelka's layer model is developed to accurately predict the infrared emissivity of low infrared emissivity coatings. The coatings are formed by mixing aluminum flakes with polymeric binders. According to distribution of the flake pigment, the Modified Kubelka's layer model is constructed with two sub-models: rough-surface and Kubelka's layer models. The facts of root-mean-square roughness (δ), root-mean-square surface slope (δ/a), thickness and volume concentration of flake pigment are systematically discussed. The results show that the flat distribution and high volume concentration of thin flake pigment result in low infrared emissivity. Our works offer the possibility of predicting the infrared optical properties of coatings.