Structural and morphological behaviour and study of the colorimetric and reflective properties of commercial inorganic pigments

Abstract

Characterization of colourful materials must include reflective, spectroscopic and colorimetric properties. Therefore, powder commercial pigments (Xadrez®) were investigated to identify their structure, morphology, composition and real colour, in order to use them as patterns to new materials. Results from X-ray diffraction, X-ray fluorescence spectroscopy and electronic spectroscopy indicated the compounds that give colour to the pigments brown, red, yellow and black as, generally, iron oxides, in the phases hematite (á-Fe2O3), goethite (á-FeOOH) and magnesium ferrite (MgFe2O4), in different proportions. Meanwhile, blue and green pigments contained copper phthalocyanine and other compounds responsible for their colour. Commercial pigments presented different degrees of solar reflectance: the highest value was 44.7 % to white pigment and the lowest 2.2 % to black pigment. Colorimetric data made it possible to calculate the real colour of the pigments, using the free software of ColorMine library, and, then, to assess the colour of new synthetic pigments.