Polyurethane is the abbreviation of urethane resin. Its molecule contains characteristic unit structure carbamate. Polyurethane is widely used. It has good wear resistance, corrosion resistance, chemical resistance, hardness and high. Elasticity and other advantages
Waterborne polyurethane is a kind of development potential in waterborne coatings. It has been widely used in many fields. It includes two-component polyurethane coatings and two-component polyurethane coatings. It is a binary colloidal state with water as the medium. The system not only has the advantages of non-toxic, non-flammable, non-polluting, environmentally-friendly, energy-saving, safe and reliable, not easy to damage the surface to be painted, easy to operate and modify, and also has some important performance characteristics of solvent-based polyurethane, making it in the fabric. Many fields such as leather finishing and adhesives have been widely used. One-component water-milk polyurethane is characterized by high elongation at break and high tensile strength, but because of its linear structure, the molecule contains a hydrophilic gene, and its water resistance and solvent resistance are poor. Limited.
The application of water-based two-component polyurethane coatings is basically equivalent to solvent-based coatings. It can be used for both heat-sensitive materials and large objects that cannot be baked, as well as for baked goods such as automobiles, by comparing actual data from experiments. It indicates that the water-based two-component polyurethane coating has the same decorative time, mechanical properties, chemical resistance and weather resistance as the solvent-based two-component coating, except for a long drying time and a short trial period.
The advantages of waterborne coatings are obvious, but they are also problematic. Compared with organic solvents, the heat of evaporation of water is higher, which requires other means to help it evaporate. For the special cases of high temperature and low temperature, the evaporation of water is slower, so the drying time is longer. The addition of co-solvents is even worse. Cosolvents are an indispensable component of aqueous coatings in helping to form films and improve film properties. Therefore, removing the solvent is not an easy task.