Barium Sulphate role in the paints

Filler in the paint (physical pigments), usually white or slightly colored, is a class of pigments whose refractive index is less than 1.7. It has the basic physical and chemical properties of paint pigments, but due to the similar refractive index and film-forming material, it is transparent in the paint and does not have the ability to color and cover the paint. It is an indispensable pigment. Due to the vast majority of fillers coming from natural ore processing products, they have characteristics such as chemical stability, wear resistance, water resistance, and low prices, so they play the role of the skeleton in the paint. Through filling, it can increase the thickness and improve the mechanical properties of the coating, and can also play roles such as durability, anti-corrosion, heat insulation, and extinction. On the other hand, as a way to reduce the manufacturing cost, it is useful because of its lower cost than that of color pigments. Under the premise of meeting the film coverage, appropriately adding physical pigments can supplement some volume of the color pigments.

There are two kinds of barium sulphate used as physical pigments. Natural products are called barite powder, and synthetic products are called precipitated barium sulfate. Barium sulfate is a dense white powder, an inert substance, with a density of 4.5g/cm³, which is the heaviest among physical pigments. It has chemical stability, is almost insoluble in water, ethanol and acids, is soluble in hot sulfuric acid, alkali, and has lightfastness. When the impurity content is low, it shows glass luster, and the cleavage surface shows pearl luster. Barite powder has a very low oil absorption (6g/100g). Precipitated barium sulfate has superior color and fine particles. Barite powder fillers are mainly used in industrial coatings that require high coating strength, filling strength, chemical inertness, and automotive intermediate coatings, as well as topcoats that require high gloss. In latex paint, because the refractive index of barite is high (1.637), fine barite powder can have a certain hiding power.