The role of bentonite in coatings can be divided into the following aspects.

① Bentonite forms flocculent substances in water and has thickening effect. Its molecular group can combine with the organic base material in the coating, which can enhance the water resistance of the coating and improve the strength and adhesion of the coating.

② Bentonite has good suspension and dispersion in water medium. Bentonite production process makes the coating not easy to precipitate, not easy to layer, and the color is uniform, so as to improve the stability of the coating suspension. Moreover, the coating performance is good, and can form a uniform, flat and smooth coating. Based on this, some heavy calcium carbonate can be added into the coating to replace light calcium carbonate, thus reducing the cost.

③ Bentonite has certain adhesion and covering power, and its price is low. Adding it to polyvinyl alcohol series coatings can greatly reduce the amount of polyvinyl alcohol and its fillers (such as light calcium carbonate), and reduce the product cost.

④ Bentonite has excellent hydrophilicity, plasticity, expansibility and cohesiveness. It can be combined with appropriate amount of water to form a colloid. Bentonite crusher can release charged ions in water. This kind of electric repulsion between ions plays a role of dispersant in the coating. In the waterproof coating, the bentonite particles in high-speed movement collide and cut with the hot asphalt, breaking and gelatinizing the asphalt. The polar substances in the gelled asphalt particles adsorb the bentonite particles, forming a colloidal hydration film on the surface of the asphalt particles, reducing the interfacial tension between the asphalt and water, preventing the asphalt particles from re-condensing, thus forming a stable dispersion phase, which acts as an emulsifier.

⑤ Bentonite has cold resistance, and the prepared coating can still be used at low temperature in winter.