With the rapid development of plastic industry, plastic products are widely used in all walks of life, and become one of the indispensable important materials for national economy and national defense construction. However, the environmental aging resistance of plastics such as ultraviolet light is not ideal, and various defects often occur on the surface during the processing and forming process. Therefore, surface finishing is needed to give the plastics special color or a certain gloss, and cover the defects on the surface of plastics, so that it has a more attractive appearance [1-2].
Plastic coatings include ordinary plastic coatings and engineering plastic coatings. When used in ordinary plastics such as polystyrene products, polyester film products and plexiglass products, it can be endowed with friction resistance, non-scratch resistance and other properties; when used in metallized engineering plastics such as phenolic products and ABS products for automobile parts and instruments, it can be endowed with high hardness, non-scratch, high gloss and aesthetic properties. Material flooring, such as PVC flooring, can give it not easy to scratch, wear resistance, low gloss, beautiful and other properties .
1 Polyurethane Coatings
Polyurethane coatings have many advantages such as good weather resistance, good gloss retention, good color stability, corrosion resistance, acid rain resistance, good low temperature construction, good coating repeatability, easy repair, good coating flexibility, excellent ductility, impact resistance and anti-vibration effect, etc. , so they have been widely used in plastic coatings. Application. In view of the requirements for environmental protection and resources, the paint industry has been developing towards low toxicity and environmental protection coatings, such as water-borne coatings, high solid coatings, light curing coatings and powder coatings, the most important of which is water-borne coatings. Although plastic coatings are mainly solvent-based, the market of water-borne coatings will continue to rise with the increasingly stringent environmental regulations and the gradual improvement of their own technology. Water-borne polyurethane coatings with high performance and low VOC content for plastics are environmentally friendly finishing materials, which have broad application prospects [5-7]. This paper mainly introduces traditional water-borne polyurethane coatings for plastics and modified and functional polyurethane coatings.
There are many kinds of plastic products with different properties. Because the molecular structure and surface polarity of different plastic substrates vary greatly, different plastic substrates should choose different coating systems . Waterborne polyurethane has many advantages, such as pollution-free, wear-resistant, corrosion-resistant, adjustable softness and hardness, and has high cost performance.