1. Permeability
The penetration of paint into the concrete base plays an important role in the good adhesion of the paint to the concrete surface. The paint can penetrate to the concrete surface to a certain depth, which will make the paint have a longer service life and better withstand the damage of the external environment to the concrete. A paint that penetrates a certain depth into a concrete base will have far greater adhesion to the substrate than one that can rely solely on the paint's adhesion to the substrate. For example, some epoxy resin coatings can penetrate into the concrete to a depth of 6mm, which not only greatly enhances the adhesion between the coating and the concrete base, but also enhances the concrete base. Of course, not all epoxy resin coatings can penetrate to such a depth. Only low viscosity coatings formulated with low molecular weight liquid epoxy resins have the ability to penetrate into concrete. Paints formulated with Polymerstar's solid epoxy resins will only penetrate to a shallow depth with the solution, but the depth of penetration will increase as the paint is further diluted.
It can be seen that for epoxy resin coatings, the penetration will be limited by the size of the resin molecules. Certain liquid epoxies have sufficiently low molecular weight and good wettability to concrete to allow good penetration. In addition, the use of solvents that wet the concrete well when formulating the paint will aid in the penetration of the paint. In this case, the epoxy resin actually reacts with the curing agent to cure after wetting the surface, so that the strength of the concrete penetrated by the paint is significantly improved, because the paint and the concrete have been integrated into a whole in this case.
Vinyl paint is a high-performance paint used in concrete earlier, and its penetration into concrete is an important method to maintain good adhesion of the paint film. Vinyl primers can penetrate concrete to a certain depth, but not to the extent that epoxy coatings can, but enough to provide a high degree of adhesion between vinyl coatings and concrete. A standard procedure in foreign early nuclear power projects is to first coat a layer of transparent vinyl coating on the concrete surface, and then apply heavy-duty anti-corrosion paint.
It can be seen that one of the important means to manufacture high permeability coatings is to use low molecular weight resins. The size of resin molecules needs to be small to a certain extent to be able to penetrate into concrete and fill various micro cracks. The lower the molecular weight of the resin, the deeper it can penetrate into the concrete. However, some low molecular weight materials are not suitable for concrete coating. For example, the molecular weight of oleoresin is very low, so it can penetrate into concrete well, but the high alkalinity of concrete will saponify it.
2. Alkali resistance
The alkali resistance of the coating is the most basic performance requirement when coating the concrete surface. Since the pH of concrete is in the 12-13 range, any paint that might react with alkali will affect the paint's adhesion. Poor alkali resistance of the paint may cause the peeling of the paint film. The best alkali resistant coatings currently available for use on concrete surfaces are vinyl and epoxy coatings. In terms of weather resistance and chemical resistance, vinyl coatings are superior to epoxy coatings; in terms of wetting and penetration, epoxy coatings are better than vinyl coatings.
3. Coating thickness
The coating film used on the concrete surface needs to have a certain thickness. In addition to penetrating into the concrete, it also needs to reach a certain thickness on the surface to overcome the defects of the coating film and the roughness of the concrete surface. The thick coating film also helps to resist the internal stress of concrete shrinkage and eliminate shrinkage cracks. For example, a coating film with a thickness of 0.3??~0.5mm can cover hair cracks to a certain extent.
4. Flexibility and extensibility
Concrete is harder than steel and more brittle than steel. Therefore, the coating on the concrete surface should have certain flexibility and extensibility to adapt to the volume change of concrete expansion and contraction. It is especially important for floor coatings and road coatings, but coatings cannot be made into elastic coatings and need to have a certain hardness. High adhesion and abrasion resistance can only be achieved when the flexibility and permeability of the coating are combined.
5. Adhesion
It is not difficult to understand that concrete surface coatings need to have high adhesion. This problem is not prominent when the concrete is in a dry state. When the concrete is in a wet state, such as in underground structures, the paint needs to improve its adhesion to the concrete surface by means of permeability and wetting of the concrete surface, so as to Resists or withstands increases in water pressure within the concrete. Due to the existence of "back water pressure" of the coating film or the immersion of the coating film in water will cause the blistering of the coating film, the coating film needs to have strong adhesion to the concrete surface. At the same time, the concrete itself also needs to have higher strength.
6. Functionality
The functionality of floor coatings is one of its main properties. In recent years, due to the continuous improvement of my country's modern industrial production level, special functional requirements such as cleanliness, wear resistance, anti-skid, anti-corrosion, and anti-static have been put forward for the production environment, so the functional requirements of floor coatings have become more and more prominent. In addition to emphasizing basic performance, the floor coating project must also give the floor reliable functionality.
