Application of talc powder in coating field
Because talc powder has good suspension and easy dispersion and low abrasive property, talc powder can be used as a filler for coating, flake particle structure talc can make the coating film with high water resistance and enamel impermeability, mainly used in primer and intermediate coating; The storage stability of the coating is improved because of the high oil absorption and good rheology of talc with fibrous particle structure. The rheological property and leveling property of the coating can be improved well, and the weatherability of the coating can be improved.
The coating itself is a composite material in a broad sense, and the reason why it appears in liquid form is to facilitate its construction. After the solvent volatilizes, the coating on the surface of the wall is essentially a composite material. The paint is a pseudoplastic fluid in the construction process, which is a non-Newtonian fluid whose viscosity decreases when the shear force increases. Therefore, the talc powder that is effectively dispersed and fully wetted with the paint resin can effectively improve the rheology of the paint.
According to the rheological model, the coating in the construction process can be regarded as composed of many thin layers with a thickness of dh. Under the action of external forces, the thin layers slide. Under the premise of effective wetting and complete dispersion of talc powder, the yield stress of interface sliding between thin layers increases because the interlayer cohesion of talc powder is greater than the cohesion between the coatings. It can be regarded as an increase in the thickness of the thin layer, so. The shear rate decreases and the viscosity increases. When the external force is increased, the internal structure is partially destroyed and the viscosity decreases. After the external force disappears, the recovery trend between the talc layers makes the degree of the coating partly increased, showing the properties of thixotropic fluids, and achieving ideal rheological properties with the help of other auxiliaries. The flaky structure of talc powder can effectively improve the leveling property of the coating during the process from the completion of coating construction to complete drying.
When the film is completely dried, talc powder can give the film a higher impact strength and fracture toughness due to its higher length-diameter ratio. The action of talc in a dry coating is similar to that of a polymer composite.
