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...

The hardness and softness of the water-based acrylic resin can be adjusted according to specific needs, but it is usually biased towards the harder side. First, the characteristics and application of water-based acrylic resin Water-based acrylic resin is an environmentally friendly water-based resin, with non-toxic, easy to clean, dry fast and other characteristics, widely used in furniture, packaging, building materials, auto parts and other fields. Second, the factors affecting the hardness of water-based acrylic resin The hardness and softness of water-based acrylic resins are affected by many factors, mainly including the characteristics of the resin itself, crosslinking agents, additives, solution concentration and external environmental factors such as light and temperature. 1. Resin characteristics: the degree of polymerization, molecular weight and distribution of acrylic monomers directly affect the molecular structure and strength of the resin, thus affecting the softness and hardness. 2. Crosslinking agents and auxiliaries: the types of crosslinking agents and auxiliaries, the amount of addition and reaction conditions will also affect the hardness and softness of the resin, such as hardness agents can increase the hardness of the resin, and softness agents can reduce the hardness of the resin. 3. Solution concentration: The change of solution concentration will affect the viscosity and drying speed of the resin, which will have a certain impact on the softness and hardness. 4. External environmental factors: the external environment such as light and temperature will also affect the softness and hardness of water-based acrylic resin. Third, adjust the hardness of water-based acrylic resin according to demand Since the softness and hardness of water-based acrylic resin are affected by many factors, the softness and hardness of the resin can be changed by adjusting these factors. 1. Add different kinds of crosslinking agents or auxiliaries According to the need, different kinds of crosslinking agents or auxiliaries can be added appropriately to adjust the hardness and softness of the resin. For example, hardness agents can increase the hardness of the resin, and softness agents can reduce the hardness of the resin. 2. Change the solution concentration of the resin Changing the concentration of the resin solution can also change the hardness of the resin, if a harder resin is needed, the solution concentration can be increased; If a softer resin is required, the solution concentration can be reduced. 3. Control heating time and temperature The heating time and temperature of the resin will affect its cross-linking degree and molecular structure, which will affect the softness and hardness of the resin. Therefore, controlling the heating time and temperature is also an important method to adjust the softness and hardness of the resin. Fourth. Conclusion In general, water-based acrylic resins are usually ...