Preparation of IR Reflective Green Pigment

This research article reports a development on green pigments having high reflectance of NIR radiation from the sun. The aim of the development is to use the green pigments as a component of building paint to reduce heat penetrating into the building. Cr2O3, a green pigment oxide, was used as the host component and the mixtures of Al2O3, V2O5 and TiO2 were used as the guest components. Al2O3, V2O5 and TiO2 were mixed at different 36 compositions according to triaxial diagram. For each sample preparation, 80% wt Cr2O3 was mixed with 20%wt of guest component for each composition. Then the mixed sample were calcined at 1150 °C for 4 hours and were ground with an agate ball mill for 7 minutes at a speed of 250 rev/min. Finally, the pigments were sieved to obtain the particle sizes of 0.5 - 2.0 µm. The pigment powders were compressed in a mold to get samples in the form of thin disks, each one with a diameter of 2.7 cm and a thickness of 4 mm. The reflectance for all samples was measured using a spectrophotometer in the wavelength ranging from 300 – 2100 nm in accordance with ASTM E891. It was found that the maximum reflectance, in the wavelengths ranging from 780 – 2100 nm, of 82.83% was obtained from the sample with a composition of 80%Cr2O3, 14%Al2O3, 4%TiO2 and 2% V2O5.