Prediction of heat build-up of solar reflecting coatings based on physico-chemical properties of complex inorganic colour pigments (CICPs)

Heat build-up of coated surfaces – such as roofs, facades and other construction elements, as well as fuel tanks, cooler jackets and warehouses – due to solar radiation and the resulting temperature increase of interiors is highly undesirable and can even be dangerous. One of the methods used to decrease the heat build-up of surfaces is the subsequent application of pigmented organic coatings with high IR reflectance properties. Investigations of the morphology, chemical composition and optical properties of complex inorganic colour pigments (CICPs) were performed and the heat build-up of the coatings was measured. The sedimentation method and laser scattering method were used to determine particle sizes and particle size distribution. The composition of pigments and shape of their particles were evaluated by energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). Phase analysis was carried out by the X-ray diffraction method (XRD). Spectral characteristics of pigments were measured at wavelengths from 250 nm to 2500 nm. The total solar reflectance (TSR) was calculated according to ASTM E903. Heat build-up testing was carried out in a box designed and constructed according to ASTM D4803. Mathematical methods were used to describe dependencies between the tested variables. These dependencies may serve as data that allow to predict heat build-up of coated surfaces as a consequence of the absorption of solar energy.