The application characteristics of talc powder in coating industry
The main composition of talc powder is water-containing magnesium silicate, molecular formula Mg3[Si4O10](OH)2, structural formula 3MgO·4SiO2·H2O, so the theoretical talc can be calculated SiO2 63.5%, MgO 31.7%, H2O 4.8%, But the natural mine mined talc also contains CaO, Fe2O3, Al2O3 and other impurities.
The common SiO2 content of talcum powder sold on the market is 10-50%, and SiO2 content > 60% is relatively small, belonging to high-end talcum powder. The parameters of talcum powder of our company are shown in the following table:
Item | Parameter |
Brand | Xufeng |
Mesh | 325目mesh～5000目mesh |
SiO2 | 20%～61% |
MgO | 28%～31% |
loss on ignition | 6%～40% |
packing size | 10kg～25kg |
Talc powder has lubricity, viscosity resistance, flow aid, fire resistance, acid resistance, alkali resistance, insulation, high melting point, chemical inactive, good hiding power, soft, good luster, strong adsorption and other excellent physical and chemical characteristics.
The application of talc in coating has the characteristics of good suspension, easy dispersion, corrosion resistance and so on. Talc powder as a coating filler, can play a skeleton role, reduce the manufacturing cost at the same time improve the hardness of the coating film, increase the stability of the product shape, tensile strength, shear strength, flexural strength, pressure strength, reduce elongation rate, coefficient of thermal expansion.
Talc powder is mainly used in primer and intermediate coating, many products flash baking primer and transport tools with paint filler preferred talc powder, steel structure primer can be used in whole or part of talc, in order to improve the precipitation of coating, coating mechanical force and recoating property.
Specific performance characteristics and applications:
① Improve adhesion and solvent resistance: ultrafine talc in solvent-based wood coatings, water-based coatings and other different coatings, for some difficult to adhere to the substrate, such as polished aluminum parts, stainless steel and other smooth, difficult to adhere to the surface, can improve the adhesion and solvent resistance of the coating;
②Improve the processing properties of coating: ultrafine talc used in water-based latex paint can give the latex paint good brushing property, leveling property, light retention, the resulting coating has good impact resistance and flexibility, but also effectively improve the corrosion resistance and dry property of the coating. Talc can improve the filling of the coating and prevent the film from cracking, because of the low hardness of talc characteristics, but also help to improve the polish of the film;
③Improve the heat resistance of heat resistant coating: studies have shown that using talc as the main filler and epoxy modified silicone resin as the base material, the preparation of epoxy silicone high temperature resistant coating, under the appropriate proportion of addition, talc can make the high temperature adhesion of the coating increase;
④For coating strengthening: because talc has a special layered structure and a larger diameter to thickness ratio, when it is added to polyurethane, the content is small, it can effectively prevent the expansion of polyurethane cracks under the action of stress, play the role of stress concentration point, so as to improve the tensile strength.
