Water based polyurethane emulsion has soft properties, so that it has good adhesion when attached to the surface of the object; At the same time, it can maintain a certain strength and does not crack. It is especially suitable for articles in high temperature, humid and chemically corrosive environment. This substance also has superior wear resistance and film smoothness, so it can form a uniform and tight film on the surface of metal, plastic, etc., and further enhance the surface adhesion of treated PE, OPP film, TPU, PU leather and other materials to ensure long-term protection and maintenance of objects

The viscosity of waterborne polyurethane emulsion has different distribution range, and the viscosity of waterborne polyurethane emulsion has different requirements when applied in different fields. In addition to adjusting the viscosity by adding thickening agents, it can also affect the viscosity of waterborne polyurethane emulsion from the molecular structure, including the content of hydrophilic groups, the solid content of waterborne polyurethane emulsion, and the degree of neutralization. The content of hydrophilic groups on the structure of waterborne polyurethane affects the size of emulsion particles and its viscosity. In anionic waterborne polyurethane, when the carboxylic acid hydrophilic groups increase, the size of the colloidal particles decreases, the distribution Narrows, and the viscosity of the emulsion increases, because the force between the colloidal particles and water increases. The viscosity of polyurethane emulsion is related to the hydrophilicity of hydrophilic monomer, particle size and size distribution, and particle density in polyurethane emulsion. The influence of solid content on the viscosity and particle size of waterborne polyurethane is also obvious. When the solid content of waterborne polyurethane is low, the content of hydrophilic monomer is fixed, and when the solid content increases, the number of particles in the emulsion also increases, and the force between the latex particles and water increases, so the viscosity of the emulsion increases. When the solid content of waterborne polyurethane emulsion is too large, the prepolymer is difficult to disperse in water, the size of latex particles becomes larger, the distribution becomes wider, and the viscosity of emulsion becomes smaller. The degree of neutralization also affects the viscosity of aqueous polyurethane emulsion. During the preparation of waterborne polyurethane, due to the double action of hydrophilic group and neutralizer, the double electric layer effect affects the viscosity change. As the neutralization increases, the viscosity may increase more, so the neutralization should be strictly controlled when preparing waterborne polyurethanes.

Due to the hydrophobic properties of waterborne polyurethane resin, it is difficult to dissolve in water or disperse uniformly, and the high reactivity of isocyanate groups to water, the direct synthesis of waterborne polyurethane faces many challenges. Therefore, to achieve the preparation of waterborne polyurethane, the primary strategy is to cleverly integrate hydrophilic functional groups (such as carboxyl, sulfonic acid, etc.) into the polymer chain structure of waterborne polyurethane, and then use the force of these hydrophilic groups to promote the successful dispersion of polyurethane in the water phase, so as to prepare water-dispersed polyurethane. In order to further optimize the comprehensive properties of waterborne polyurethane coatings, the researchers explored the technical path of introducing sealers. Specifically, the sealer is able to selectively react with part of the isocyanate group (i.e. -NCO) in the prepolymer to form a stable aminoester bond. In this process, the ammonia ester bond is like a "sleeping" isocyanate reservoir, which can "wake up" and split under appropriate heating conditions, re-release the isocyanate group, and then efficiently combine with the hydroxyl group on the fabric surface to form a strong polyurethane crosslinking network. This significantly enhances the adhesion strength and bonding firmness of the waterborne polyurethane coating and the fabric substrate. Sinograce Chemical is specialized in the production of water based polyurethane resin used on the surface of textile supplies, welcome to consult.

The final state of waterborne polyurethane is a solid film. During the process from emulsion to solid film, accompanied by the evaporation of water and the concentration of water dispersion, the latex particles are close to each other. Before the solid content reaches 74%, the dispersion particles can move in the continuous phase of water. Under the influence of water/air interfacial tension, the particles fuse with each other, and finally diffuse through the molecular chain between the dispersion particles, resulting in a homogeneous film with certain mechanical properties.From the basic principle of film forming, the key to the film forming performance of polymer emulsion lies in the deformability of latex particles and the molecular chain diffusion movement. Polyurethane emulsion particles are an open water swelling structure, latex particles contain a certain amount of water, with strong deformation ability, and the characteristics of polyurethane particles swelling can cause particles to produce a very large surface area, with the swelling of small particles, to promote the polyurethane emulsion has a strong film forming ability. Even at a lower film forming temperature, it still has a high film hardness. In addition, when the film is dry, the moisture in the emulsion particles will help soften the polymer, making it easy to deform and form a film. Because the polyurethane molecule is composed of soft and hard segments, its special molecular structure determines that the polyurethane molecular chain has a strong diffusion movement ability, and the glass transition temperature of the soft segment is about 60~30℃, low glass transition temperature will reduce the minimum film forming temperature of the coating film, which can significantly help the film formation of the emulsion. Therefore, polyurethane emulsion has excellent film forming properties. In addition, when the film is dry, the moisture in the emulsion particles will help soften the polymer, making it easy to deform and form a film. Because the polyurethane molecule is composed of soft and hard segments, its special molecular structure determines that the polyurethane molecular chain has a strong diffusion movement ability, and the glass transition temperature of the soft segment is about 60~30℃, low glass transition temperature will reduce the minimum film forming temperature of the coating film, which can significantly help the film formation of the emulsion. Therefore, polyurethane emulsion has excellent film forming properties. The main medium of waterborne polyurethane is water, the volatility of water is lower than that of general organic solvents, and the evaporation heat of water is larger than that of organic solvents. The biggest drawback is that aqueous polyurethane adhesives dry slowly compared to solvent-based ones. However, the lowest film forming temperature of waterborne polyurethane is about 0℃, and because it does not contain emulsifier, it can form a film with lust...