Coating classification: performance adjustment in the formulation of waterborne coatings -- water resistance

Core tip: a considerable number of surfactants or hydrophilic monomers are used in the synthesis of waterborne wood paint base materials, resulting in poor water resistance of the film after film formation, making the film softer, hardness decreased, strength decreased, the higher the water absorption, the greater the loss of film strength, so the water absorption of waterborne wood paint should be as small as possible There is no corresponding relationship between the water absorption and the whiteness of the film after immersion The whiteness phenomenon is caused by the change of light refraction, and is the result of the joint action of water molecules and polymer segments in the film on the light Some paint films with high water absorption are obviously white after being immersed in water Paint knowledge how about Akzo Nobel Powder Coating Recommended introduction: powder coating is a kind of coating with different form from general coating, which is in powder form It is a new type of coating, because of its own advantages and more and more known by people Let's introduce Akzo Nobel Powder coating Akzo Nobel Powder coating is a cost-effective coating solution, which can be applied to different kinds of products After the treatment of static electricity and fire baking, a tough and durable coating surface will be formed, with the least impact on the environment Since the introduction of this technology, powder coating has been able to continue to maintain the Paint Home News: a considerable number of surfactants are used in the synthesis of waterborne wood paint base materials, or hydrophilic monomers are used to synthesize polymers, resulting in poor water resistance of the film after film formation, which makes the film softer, hardness decreased, and strength deteriorated The higher the water absorption, the greater the loss of film strength, so the smaller the water absorption, the better the waterborne wood paint should be There is no corresponding relationship between the water absorption and the whiteness of the film after immersion The whiteness phenomenon is caused by the change of light refraction, and is the result of the joint action of water molecules and polymer segments in the film on the light Some paint films with high water absorption are obviously white after immersion Therefore, it is impossible to judge the hydrophilicity and water resistance of the film only from its whiteness after immersion After absorbing water and whitening, most paint films can be restored to transparent state by drying again However, for thicker films, the process of whitening recovery may be very long, sometimes as long as several weeks It has also been observed that some paint films can't return to transparent state after drying for a long time at room temperature The first reason is that the paint film is too thick and the water can't completely migrate out It is also possible that the molecular structure of the polymer changes and the refractive property changes after the paint film is soaked in water, which is an irreversible process, so the whitening can't be restored Adjusting the water resistance of waterborne coatings can be considered from three aspects: 1) waterborne resins, such as waterborne polyurethane and waterborne acrylic polymers, are all two surfactants when they are used in structural emulsion polymerization, that is, one end is lipophilic and the other is hydrophilic After polymerization, these surfactants still remain in the emulsion, and remain in the paint film after film formation After encountering water, the affinity of the water and water makes the water more permeate, diffuse and migrate in the paint film, and increase the water absorption rate In order to overcome the adverse effects of surfactant, soap free polymerization method has been used to prepare emulsion The water resistance of emulsion synthesized by emulsion polymerization has been significantly improved The water absorption of different emulsions or water dispersions is very low, below 10%, and high can be more than 100%, mainly determined by the structure of polymers The hydrophilic structure of polymer and the hydrophilic monomers used in the synthesis have a great influence on the water absorption and water resistance of the film (methyl) acrylic acid, hydroxyethyl methacrylate, hydroxypropyl (methyl) acrylate, maleic anhydride, dimethyl hydroxypropionic acid, hydroxymethyl butyric acid and other hydrophilic monomers can improve the dispersion of polymers in water, which is conducive to the formation and stability of emulsion or water dispersions, and at the same time bring about the drawback of water absorption and water resistance of film after film formation The water absorption will increase when there is polyethylene glycol chain segment in polyurethane structure, while the possibility of hydrolysis degradation of polyurethane with polyester structure is great, and the water resistance will be affected The fluorocarbon monomer or organosilicon compound can improve the water resistance of the paint film and increase the water resistance with the increase of fluorocarbon and silicon compounds 2) The water resistance of the film can be significantly improved by adding crosslinking agent When the same paint is crosslinked by the addition of a diplomatic agent, whether it is crosslinked by isocyanate curing agent, aziridine or epoxy compound, the water absorption of the same paint can generally be reduced to less than 15%, although there are differences in the reduction range The stronger the hydrophilicity of the hydrophilic chain segment in the hydrophilic modified isocyanate curing agent, the higher the water absorption of the crosslinked film Water resistant emulsion or water dispersions themselves are very low in water absorption, and the water absorption rate decreases slightly after crosslinking On the contrary, the water absorption of the film with high hydrophilicity decreased greatly after crosslinking 3) The hydrophobicity of the film can be improved by adding hydrophobic compounds to the formulation of water-resistant coating, and the infiltration of the film can be reduced or reduced Wax emulsion and wax powder are the most commonly used additives to improve hydrophobicity, of which PE wax emulsion is the best In addition, some hydrophobic additives have better effect It can produce lotus leaf effect This hydrophobic effect is due to the regular aggregation of hydrophobic additives on the surface of the paint film, and the transfer of hydrophobic agent will make the lotus leaf effect disappear, so the paint film added with hydrophobic agent will lose its hydrophobic effect after repeated scrubbing Home of coatings is specialized in coatings, diatom mud, paint coating, coating technology, fire retardant coating news and coating, diatom mud, paint coating, coating technology, fire retardant coating decoration knowledge and decoration renderings,