1 Department of Mechanical Engineering, Technical University of Denmark2 Materials and Surface Engineering, Department of Mechanical Engineering, Technical University of Denmark3 Department of Photonics Engineering, Technical University of Denmark4 Optical Microsensors and Micromaterials, Department of Photonics Engineering, Technical University of Denmark5 Solid Mechanics, Department of Mechanical Engineering, Technical University of Denmark6 Centre for oil and gas – DTU, Center, Technical University of Denmark
This paper presents the results of a physical simulation carried out using TiO2-Polyurethane composite coating on bright aluminium surface to understand the light scattering effect for designing white surfaces. Polyurethane matrix is selected due to the matching refractive index (1.7) with Al2O3 layer on anodized aluminium surfaces. Three different TiO2 particle distributions were dispersed in polyurethane and spin coated onto high gloss and caustic etched aluminium substrates. Reflectance spectra of TiO2-polyurethane films of various concentrations were analysed using an integrating sphere. The results show that the TiO2-polyurethane coatings have a high diffuse reflectance as a result of multiple scattering from TiO2 particles. Diffuse reflectance spectra of TiO2 containing films vary weakly with particle concentration and reach a steady state value at a concentration of 0.75 wt.%. Using the Kubelka Munk two-stream model, the scattering and absorption coefficient of the TiO2 particles embedded in polyurethane was determined. These studies can serve on understanding the fundamental requirements for generating a bright and white decorative anodized aluminium surface.