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Synthesis of epoxy resin modified waterborne polyurethane
Waterborne polyurethane is a kind of polymer material with good physical properties, mechanical properties, weather resistance and environmental friendliness. With the development of society and the progress of the times, it is gradually applied in various fields such as paint, home decoration and ink. However, due to the limitations of its synthetic means, waterborne polyurethanes are still inferior in some respects to oily polyurethanes. In order to improve the overall performance of waterborne polyurethanes, more and more researchers are investing in the modification of waterborne polyurethane resins. The main means of modification are:
1. Improve monomer and synthesis process; 2. Add auxiliary; 3. Crosslink; 4. Composite.
The optimized composite of waterborne polyurethane mainly includes epoxy resin modification, polysiloxane modification and acrylic composite modification. The epoxy resin modified waterborne polyurethane will be briefly described below.
Epoxy resin itself has the characteristics of high mechanical strength, good adhesion, good chemical stability and low cost, and has been widely used in industry. However, it also has some disadvantages, such as poor toughness, brittleness after curing, low impact resistance, etc. These defects limit its application. By combining a polyurethane having high elasticity and high adhesion with an epoxy resin, an epoxy-modified polyurethane excellent in performance can be obtained.
There are three main methods for epoxy resin modified waterborne polyurethane:
1. Mechanical blending, that is, mixing epoxy resin and waterborne polyurethane in a certain ratio;
2. Graft copolymerization of epoxy resin and polyurethane: graft copolymerization of epoxy resin and polyurethane prepolymer, and then emulsification with water to obtain epoxy resin modified waterborne polyurethane;
3. Opening of the epoxy resin into the polyurethane: the epoxy resin after the ring opening is introduced into the polyurethane prepolymer as a polyol component.