Author: Site Editor Publish Time: 2024-07-10 Origin: Site
The combination of high and low temperature resistance, corrosion resistance and excellent mechanical properties of silicone with polyurethane can significantly improve the comprehensive properties of waterborne polyurethane.
Silicone modified polyurethane was prepared from toluene diisocyanate, silicone modified polyether polyol and 1, 4-butanediol as main raw materials. The research group carried out the performance comparison test of silicone modified two-component polyurethane coating and polyurethane coating without silicone.
The test results show that ,On the basis of maintaining excellent mechanical properties of polyurethane coatings, silicone modified polyurethane coatings have stronger hydrophobic properties than those without silicone modified polyurethane coatings. The enhanced hydrophobic properties are due to the low surface tension and high hydrophobicity of methyl groups in silicone.
Polyurethane /SiO2 hybrid containing modified SiO2 was synthesized in situ by hydrolysis and condensation by introducing tetraethoxysilane (TEOS) or methyl triethoxysilane (MTES) into polyurethane dispersions, and was added to waterborne polyurethane emulsion to prepare polyurethane composite emulsion. Compared with the polyurethane composite film containing unmodified SiO2, the modified SiO2 functionalized polyurethane composite film has better hardness and wear resistance even when the silicon content is 2% to 3%.
Acrylate modification
Polyurethane resin has good strength, elasticity and bonding properties. Compared with polyurethane resin, polyacrylate materials have better weather resistance, water resistance, solvent resistance and light preservation properties. Polyacrylate and polyurethane have a good complementary effect in performance, and acrylate modified waterborne polyurethane can effectively combine the advantages of both to have better performance.
Using diacetone acrylamide (DAAM) as crosslinking agent, the aqueous polyurethane-polyacrylate hybrid emulsion was prepared by physical blending method.
The film performance test results show that The acrylic modified polyurethane coating has excellent hardness, gloss, water resistance and water absorption. In addition, the paint has excellent moisture sensitivity and moisture retention.
The water-based acrylate emulsion was prepared by emulsion polymerization, and then polyurethane was modified by the acrylate to obtain polyurethane-acrylate (PUA) composite emulsion. The composite emulsion has excellent properties of waterborne polyurethane and polyacrylate, and has good film forming performance.
Epoxy resin modification
Epoxy resin (EP) material has the advantages of high modulus, high strength and good chemical resistance. The epoxy resin contains active epoxy groups, which can directly participate in the synthesis reaction of waterborne polyurethane and improve its performance.
Aqueous polyurethane modified by epoxy resin with an epoxy value of 0.44 was prepared. The hardness of the polyurethane coating can be increased to 0.70, and its mechanical properties are positively correlated with the content of epoxy resin. After epoxy resin modification, waterborne polyurethane coating has higher film hardness, better water resistance and solvent resistance.
A series of MDI aqueous polyurethane emulsions modified by epoxy resin were prepared by internal emulsifying method with 4,4 '-diphenylmethane diisocyanate (MDI) as monomer, and the effect of epoxy resin E-51 on the coating properties was studied.
The test results show that The comprehensive properties of aqueous polyurethane emulsion film modified by epoxy resin are improved. When the addition of epoxy resin E-51 is 4% ~ 6%, the comprehensive properties of emulsion and film are the best.
Nanomaterial modification
Nanomaterials have excellent properties such as small size quantum effect and surface effect. The organic combination of nanomaterials and WPU can meet the demand for WPU composites in different application fields.
Polyurethane/nano-calcium carbonate nano-composite coating was prepared by mixing KH560 modified nano-calcium carbonate with pure polyurethane, and its properties were tested.
The test results show that
The dispersion of modified nano-calcium carbonate in polyurethane matrix is improved. At the same time, the heat resistance of polyurethane coating is also improved, and its thermal conductivity increases with the increase of nano-calcium carbonate.
Water-based polyurethane composites modified by carbon nanotubes (A-DOA/CNTs) functionalized by dopamine (DOA) and γ-aminopropyl triethoxysilane (APTES) were prepared by reaction with water-based polyurethane prepolymers, and their properties were tested.
When the mass fraction of A-DOA/CNTs was 0.75%, the comprehensive properties of the film were the best. Compared with the unmodified polyurethane, the thermal decomposition temperature of the modified polyurethane is increased by 28℃, and its heat resistance, water resistance and mechanical properties are greatly improved.
Organofluorine modification
In recent years, organofluorine polymers have attracted extensive attention because of their unique solvent resistance and high hydrophobicity. The C-F bond in organic fluorine has the characteristics of bond length and high bond energy, which gives the fluorine-containing materials excellent properties of high stability and good heat resistance. The properties of waterborne polyurethane can be improved by combining organic fluorine with waterborne polyurethane.
Uv-curable polyurethanes were prepared by using hexanols and fluorinated diols as monomers. The effects of monomer ratio and reaction conditions on the coating properties of waterborne polyurethanes were investigated in detail.
Research shows that
The hardness and tensile strength of the film are affected by hyperbranched structure and fluorine content. The hyperbranched structure of PU and the increase of fluorine content increase the hardness and tensile strength of PU film.
In addition, the increase of fluorine content also improves the hydrophobicity and water resistance of the film. At the same time, the particle size of the emulsion and the thermal stability of the film were increased with the increase of the content of fluorinated diols. However, when the fluorine content is too high, the performance of polyurethane coatings decreases, and when the fluorine diols content is 8%, the overall performance of the coatings is the best
Using perfluoroalkylethyl acrylate and vinyl triethoxysilane as modifiers, the modified waterborne polyurethane emulsion was prepared by copolymerization of isocyanate monomer and polyol monomer with the modifiers. The test results show that after modification, the water resistance, heat resistance, hardness and chemical resistance of waterborne polyurethane coatings are improved, and the fracture surface and surface smoothness are also improved compared with before modification.
Vegetable oil modification
Vegetable oil can be used as an ideal modifier for waterborne polyurethane due to its renewability, easy degradation, low cost and easy availability. Its long hydrophobic fatty acid chain segment can improve the water resistance of the film. The functional degree of hydroxyl group in vegetable oil is > 2, which can form a cross-networking structure with polyurethane to enhance its mechanical strength. The unsaturated double bonds contained in vegetable oil can be further oxidized and crosslinked during curing to optimize the performance of polyurethane coatings
Tricarboxylic castor oil (MACO) containing carbon carbon double bond was synthesized by maleic anhydride modified castor oil, and used as internal crosslinking agent to prepare castor oil modified waterborne polyurethane emulsion (MACO-WPU).
The test results show that
The water resistance and mechanical properties of the modified polyurethane emulsion were improved. When the amount of MACO is 3%, the emulsion is stable, the film is complete and the performance of the product is excellent. With the addition of MACO, the thermal stability of the modified waterborne polyurethane emulsion was improved, while its crystallinity was decreased
A new vegetable oil modified two-component wood coating for wood furniture was prepared by using soybean oil modified waterborne polyurethane and acrylic emulsion as the main body and Hexamethylene diisocyanate (HDI) as the curing agent, and its properties were tested.
The results show that the obtained coating dries quickly and feels good. After curing, the surface of the film is smooth and smooth, the adhesion can reach 0 level, and the resistance to water, alcohol, alkali, tea and vinegar has been significantly improved.
Compared with unmodified polyurethane coating, soybean oil modified polyurethane coating has excellent performance, environmental protection and no odor.