The influence of synthesis conditions on the crystal and aggregate properties of calcium salt azo pigment CI Pigment Red 48:2

The influence of pH and heating time at 80 °C on the final stage (conversion to the calcium salt) of the formation of the metal salt azo pigment, CI Pigment Red 48:2, has been investigated. A series of systematically prepared pigment samples were characterized by transmission electron microscopy, X-ray powder diffraction, surface area measurement and a detailed nitrogen adsorption–desorption isotherm investigation. Significant differences in the crystal sizes and morphologies and in the crystal growth patterns were observed. The colour and lightfastness properties in air-drying alkyd paints are correlated with the physical property data.