How is talc used in coatings?
Talc is a commonly used filler in solvent-based coatings. Its main component is hydrous magnesium silicate talc (3MgO·4SiO2·H2O), which is a monoclinic crystal system with pseudohexagonal or rhombic flakes. The talc made by fine grinding is a white and fine powder with a smooth touch. It has the characteristics of lubrication, fire resistance, acid resistance, insulation, high melting point, and strong chemical inertness. In recent years, with the application of precision grinding equipment, talc has been widely used in water-based coating systems, including primers, intermediate coatings, industrial coatings, and building interior and exterior wall coatings. Because of its soft texture and excellent dispersibility and suspension, it occupies an important position in the coating field.
Performance and Uses
Flake talc
It has excellent brushability, film smoothness, water resistance and impermeability, and is often used in primers and intermediate coatings. For example, adding talcto steel structure primers can improve precipitation stability, mechanical strength and recoating performance; in anti-corrosion coatings, it can extend the penetration path of corrosive media and enhance the protective effect.
Fibrous talc
Due to its long particles, high oil absorption and excellent rheology, it can prevent the coating from settling during storage, optimize the sag during construction and improve the overall performance of the coating.
Talc is also widely used in industries such as plastics, cables, inks, and papermaking. In plastics, it can improve transparency and strength; in papermaking, it can enhance gloss and ink performance. In PU, PE, UV, and NC coatings, it can increase the transparency and recoatability of the primer, optimize filling efficiency, reduce costs and improve appearance.
Particle size classification and application
Talc for coatings is divided into ordinary particle size (325 mesh), fine grade (20um, 10um), ultrafine grade (5um), nano grade and chemically modified talc according to particle size. Different particle sizes are suitable for different needs:
Ordinary particle size: used for primer intermediate layer or rough coating film, such as interior wall pattern paint.
Ultrafine grade: adjust the gloss, consistency and sag of the coating, and partially replace pigments such as TiO2.
Chemically modified talcum powder: optimize viscosity and reduce construction difficulty.
In addition, talcum powder has a high oil absorption and can be used with barite powder in situations where low oil absorption is required; other fillers need to be added for reinforcement when wear resistance is limited. Talcum powder containing impurities is not suitable for high weather resistance exterior coatings because it easily reacts with acid; industrial talcum powder with low whiteness is also not suitable for situations with high color brightness requirements.
In short, fillers can be flexibly selected according to the formula, cost and actual needs, and coating products that meet market demand can be produced by adjusting the addition amount (usually 5%-40%).
