Changes in the physical properties of kaolin on exposure to elevated temperature

Pigments prepared from beneficiated middle Georgia kaolins by heat treating or "calcining" are important commercial products. This study, carried out using a fine particle (98% less than 2ц\m, 0.27 цm median size) kaolin, shows how various physical properties of the resulting product vary with heat treatment temperature in the range of 100 to 1000°C. In the metakaolin range, the calcined product exhibits increased acid solubility, a slightly higher surface area and a slightly lower density. Calcination also aggregates the kaolin particles giving products of coarser particle size than the original kaolin. The opacity imparted to paper coatings and paint films by the calcined kaolins is increased threefold compared to the uncalcined kaolin.Sennett Paul. Changes in the physical properties of kaolin on exposure to elevated temperature. In: Proceedings of the 9th international Clay Conference, Strasbourg, 1989. Vol V : Industrial applications of clays. Analytical techniques and teaching of clay mineralogy. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1990. pp. 71-79. (Sciences Géologiques. Mémoire, 89