Abstract:

Using aluminium sulfate and sodium hydroxide as raw materials, hydroxyl aluminium oxide （AlOOH） coated iron oxide yellow pigment was prepared by the co-precipitation method. The effects of AlOOH coating amount on the lattice structure, infrared spectrum, microscopic morphology, reflectance rate, thermal weight loss, Zeta potential and heat resistance of iron oxide yellow pigment were studied. The results show that AlOOH of the Boehmite type synthesized by the co-precipitation method is spherical particles with a size of 15-25 nm. The granular AlOOH is coated on the surface of the plate-shaped morphology of the iron oxide yellow pigment, reducing the direct heating and oxidation of the iron oxide yellow pigment at high temperatures and improving the thermal stability of the pigment. The weight loss of 15% AlOOH at 800 ℃ is 3.2%, indicating the best thermal stability. The Zeta potential of iron oxide yellow pigment continuously increases with the increase of the coating amount of AlOOH, and the Zeta potential of 20% AlOOH is the maximum value of 26.8 mV. The reflectivity of 15% AlOOH pigment in visible light reaches the maximum value of 49.3%. After heating at 240 ℃ for 30 minutes, the physical color changes and color difference value changes of iron oxide yellow pigments with different AlOOH coating amounts were tested. The color difference value ΔE of 15% AlOOH pigment is the lowest value of only 3.65, and the lowest Δa is 0.53. The degree of reddening of the pigment is the smallest and its thermal stability is the best.

Key words: co-precipitation method, iron oxide yellow, hydroxy-alumina, pigments, cladding, heat resistance