Waterproof effect of polyurethane coatings;
1. One-component polyurethane waterproof coating is a reactive flexible waterproof coating with isocyanate and polyether as main raw materials and various additives. The product has good physical properties, strong adhesion and wet curing at room temperature. Some polyurethane waterproof coatings are slightly sticky and their performance is up to standard.
2. It has high strength, high elongation, high solid content and strong adhesion. Natural leveling, good ductility, can overcome the leakage caused by cracking of the base. Normal temperature construction, simple operation, non-toxic, excellent weather resistance and aging resistance. The construction is convenient, which overcomes the shortcoming that the two-component polyurethane waterproof coating needs to be metered and stirred, and ensures the stability of product quality and the waterproof effect of the project.
Classification of polyurethane coatings:
1, two-component polyurethane coatings have excellent properties such as low film forming temperature, strong adhesion, good wear resistance, high hardness, good chemical resistance and weather resistance, and are widely used in industrial protection, wood furniture and automobile coatings. Waterborne two-component polyurethane coatings combine the high performance of two-component solvent-based polyurethane coatings with the low VOC content of waterborne coatings, which has become a research hotspot in the coating industry. Waterborne two-component polyurethane coating is composed of waterborne polyol containing -OH group and low viscosity polyisocyanate curing agent containing-NCO group, and its coating performance is mainly determined by the composition and structure of hydroxyl resin.
2. One-component waterborne polyurethane coatings are based on waterborne polyurethane resin and water as dispersion medium. Crosslinked modified waterborne polyurethane coatings have good storage stability, film mechanical properties, water resistance, solvent resistance and aging resistance, which are similar to traditional solvent-based polyurethane coatings and are an important development direction of waterborne polyurethane coatings.
3. The UV-curable waterborne polyurethane coating uses electron beam radiation and high-intensity ultraviolet radiation to trigger the crosslinking curing of low-activity prepolymer system, mainly in the form of UV curing. Firstly, prepolymer was prepared from unsaturated polyester polyol, and then particle gene was introduced by conventional method. After hydrophilic treatment, waterborne polyurethane dispersion with double bonds in the main chain was prepared, and then mixed with soluble high-activity alkoxy triacrylate monomer, photosensitizer and other additives to obtain light-cured waterborne polyurethane coating.
4. Curing waterborne polyurethane coating at room temperature. For some heat-sensitive substrates and large parts, cross-linking cannot be carried out by heating, and room-temperature cross-linked waterborne polyurethane coatings must be used. By combining with water-dispersible polyisocyanate, the properties of waterborne hydroxyl-terminated polyurethane prepolymer/acrylate mixture, especially hydroxyl acrylate mixture, can be improved. This kind of waterborne polyurethane coating adopts a special polyisocyanate crosslinking agent, that is, an isocyanate prepolymer containing-NCO end groups. After hydrophilic treatment, it is dispersed in various hydroxyl-containing polymers to form a dispersion, which can be cured at room temperature with various hydroxyl-containing polymer aqueous dispersions.
5. Compared with solvent-based products, the third generation waterborne polyurethane coating (PUA), polyurethane (PU) emulsion and polyacrylic acid (PA) emulsion have the advantages of low cost, safety, non-combustion, non-toxicity and no environmental pollution. The disadvantages of pure PA emulsion are poor wear resistance, water resistance and chemical resistance, high solid content and not wide application range. PU and PA are complementary in nature. PUA composite emulsion has the advantages of wear resistance, corrosion resistance and brightness, softness and elasticity, good water resistance and mechanical properties, and good weather resistance, etc. It is known as the "third generation waterborne polyurethane" and has become the development trend of today's coatings.
6. Environmental-friendly low aromatic polyurethane coatings can make up for the lack of performance of water-based coatings and maintain the excellent performance of solvent-based coatings. But also can reduce the influence of the coating on the environment. Considering both performance and environmental protection, this problem has been well solved. The coating system adopts petroleum low-polarity solvent with little smell and low toxicity as diluent. It can significantly reduce the emissions of substances that pollute the environment, such as benzene, xylene and harmful waste gas pollutants (HAPs). As a solvent-based coating, it also has good painting performance and application performance, and can be applied in winter at low temperature. In addition, because the solvent in the coating system has low solubility and will not corrode, it is easy to recoat. Can be used to spray materials that are easily corroded by solvents.
The above is a concrete introduction to the waterproof effect and classification of polyurethane coatings. The waterproof effect of polyurethane coating increases its application scope in building construction, and the performance of polyurethane coating is diverse and adjustable. If the formula can be improved, the effect of polyurethane coating can be better reflected. Polyurethane coatings can be coated with high hardness, and some elastic coatings with excellent flexibility have greatly enhanced the application effect and scope of polyurethane coatings.
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