Characteristics of the treated ground calcium carbonate powder with stearic acid using the dry process coating system

Abstract

This study examined the surface properties, fluidity, flowability and floodability of untreated ground calcium carbonate (GCC) powder and treated GCC powder with stearic acid (SA) using a dry process coating system. The surface of GCC powder is generally hydrophilic, but was changed to a hydrophobic surface when coated with SA. The contact angle of water on the coated GCC powder surface increased with increasing concentration of SA. The contact angle and hydrophobicity on the GCC powder treated with 1.0 mass% SA was 105° and 100%, respectively. The dispersive component of the surface free energy, γSD of the untreated GCC powder determined using inverse gas chromatography (IGC) was 103mJ·m-2 at 100°C. However, that of the GCC powder treated with 1.0mass% SA was 34.8mJ.m -2. Kawakita's equations were used to characterize the properties of the powder. The fluidity index was increased from 18.60 to 30.39 when the surface of GCC powder was modified with SA. On the other hand, the characterization based on the method suggested by Carr showed that the flowability and the floodability of the GCC powder treated with SA increased from 45 to 53 and from 30 to 69, respectively. Therefore, the flowability and floodability of the GCC powder treated with SA were superior to the untreated GCC powder. © 2009 The Japan Institute of Metals.