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Waterborne polyurethane (PU) is a kind of waterborne coatings with great development potential and has been widely used in many fields. It includes one-component polyurethane coatings and two-component polyurethane coatings. It is a binary colloidal system with water as the medium. It is not only non-toxic, not easy to burn, not polluting the environment, energy saving, safe and reliable, and not easy to damage the painted surface Easy operation and modification; At the same time, it also has some important performance characteristics of solvent polyurethane, which makes it widely used in many fields such as fabric, leather finishing and adhesives. Single component water emulsion polyurethane is characterized by high elongation at break (more than 800%) and high tensile strength (about 20MPa). However, its application is limited because of its linear structure and hydrophilic groups in its molecules
The application field of waterborne two-component polyurethane coatings is basically equivalent to that of solvent based coatings. It can be used not only for thermal sensitive materials (such as wood and plastics) and large objects that can not be baked, but also for baked objects such as automobiles. Through the comparison of the reported experimental data, it is shown that in addition to the longer drying time and shorter application period of waterborne two-component polyurethane coatings, The decoration, mechanical properties, chemical resistance and weather resistance of the film are comparable to those of solvent based two-component pur coatings.
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