Waterborne polyurethane is the basic substance and key component for preparing waterborne polyurethane adhesive, and its performance directly determines the final performance of the adhesive. According to the type of charge carried by particles, waterborne polyurethane can be divided into anionic, cationic and nonionic types. The preparation of waterborne polyurethane is generally to synthesize polyurethane prepolymer with a certain molecular weight, and then disperse the prepolymer in water under the action of shear force. At present, its preparation methods are mainly hydrophilic monomer chain extension and self-emulsification (so-called hydrophilic monomer chain extension method), that is, hydrophilic chain extender is introduced into the molecular structure of polyurethane prepolymer, and the obtained polymer can be directly dispersed in water to form waterborne polyurethane without adding emulsifier. The synthesis process of hydrophilic monomer chain extension method includes solvent method, prepolymer water dispersion chain extension method, melt dispersion polycondensation method and so on.

High-performance waterborne polyurethane adhesive should have the following characteristics:

(1) has good water resistance and medium resistance.

(2) High adhesion strength and high initial adhesion.

(3) Good storage stability.

(4) Freeze-thaw resistance and high temperature resistance.

(5) Fast drying speed and good film-forming property at low ambient temperature.

(6) Good construction technology.

To achieve the above points, in addition to synthesizing high-performance waterborne polyurethane, the selection of film-forming additives is also particularly important.

For more information, please visit the Global Polyurethane Network.