| Résumé : |
Effect pigments display a wide range of properties such as colour-travel, reflect or refract light. When substrate used are flat regular, laminar in shape then the effect pigments are mirror type. Basic lead carbonate and bismuth oxy chloride fall under this category. Basic Lead carbonate pigment is obtained by passing carbon dioxide gas in lead acetate solution having luster and brilliance that equals or excels. These pigments are used in textile, plastics, paints, artificial pearls. Lead based pearlescent pigments are having excellent pearlescent effect but considered to be toxic, so banned in most places. Bismuth Oxy chloride (BiOCI) crystals are flat, regular, octahedral in structure. These pigments look smooth microscopic compared to mica coated pearl. Despite higher refractive index (2.15) than basic Lead carbonate, bismuth oxy chloride does not show the brilliance of basic lead carbonate due to its inferior crystal forms. BiOCI is prepared reacting bismuth nitrate in presence of chloride ions with sodium hydroxide. The crystal quality can be adjusted by the chosen reaction parameters, such as bismuth salt concentration, temperature, pH-value, reactor geometry, and addition of surfactants. BiOCI is used in plastics, paints, inks, textiles artificial jewelry, and automotive coatings. The major limitation would be the higher cost and its higher density that makes it settli n application media. |
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Effect pigments - Basic lead carbonate & bismuth oxy chloride based pearlescent pigments in PAINTINDIA, Vol. LXVII, N° 8 (08/2017)
