Thermal Resistant Properties Improvement of Iron Oxide Yellow Pigment via Coating Substances Containing Aluminum
The application of iron oxide yellow in paints and plastics industries is restricted due to the poor heat resistance leading to water loss at 177 degC The heat resistant iron oxide yellow was prepared by combined hydrothermal and precipitation methods to coat substances containing Al on the surface of iron oxide yellow. The effects of hydrothermal reaction time, hydrothermal reaction temperature and pH value on the thermal properties of coated iron oxide yellow were investigated. The optimal reaction conditions obtained are reaction temperature of 180 reaction pH value of 8, hydrothermal processing time of 6 h, heat resistance of yellow degC iron oxides of 240 and degC color difference of 2.58. The results show that the different coating layers lead to different heat resistances of the samples. When the pH value is 4 or 6, the coating layer is natroalunite and aluminum oxyhydroxide mixture. While the pH value increases to 8 or 10, the surface of coating layer is aluminum oxyhydroxide. Based on the results by thermal analysis, the heat resistance property of coating iron oxide yellow is promoted, compared to that of ordinary pigment.