Waterborne PU resin is a new environmentally friendly polymer material that uses water instead of organic solvents as a dispersing medium in polyurethane systems. Due to its excellent environmental friendliness, excellent mechanical properties, and good compatibility with other water-based resins, water-based PU resin is widely used as an adhesive, coating, and coating product.

Synthesis of waterborne PU resin:

The synthesis of waterborne PU resin generally involves a pre polymerization reaction of diisocyanates, oligomeric polyols, and chain extenders, and the reaction mechanism of this step belongs to a stepwise polymerization reaction. After the reaction generates a certain molecular weight prepolymer or high molecular weight PU resin, it can be emulsified in water using phase transfer method to synthesize water-based PU resin.
Raw materials for water-based PU resin synthesis:
Polyisocyanates: Commonly used varieties include aromatic diisocyanates, including TDI and MDI; Aliphatic diisocyanates HDI, cycloaliphatic diisocyanates IPDI, HMDI, and so on. Aromatic PU has good mechanical properties, but due to the presence of benzene rings, it is not resistant to yellowing and has a high thermal activation temperature, which limits its application range. The hydrolysis resistance and storage temperature of aliphatic or cycloaliphatic PU are also better than those of aromatic polyurethane, and they have excellent resistance to yellowing. High quality water-based PU resins are generally synthesized using aliphatic or cycloaliphatic isocyanates.

High molecular weight polyols: The high molecular weight polyols used in the synthesis of waterborne PU resins mainly include polyether polyols, polyester polyols, polyethylene glycol, polytetrafluoroethylene ether, polyester amides, acrylic polyols, and so on. The ether group in polyether polyurethane is easy to rotate, has good flexibility, good low-temperature performance, and is not easily hydrolyzed. Its water resistance is better than that of polyester polyurethane. However, due to the poor hydrolysis resistance of polyester itself, the storage period of polyester based waterborne polyurethane produced from general raw materials is relatively short.