Classification of waterborne polyurethane

According to the dispersion state, waterborne polyurethane can be divided into water-soluble polyurethane, polyurethane dispersion and polyurethane emulsion, and its characteristics are as follows:

According to the emulsification method, waterborne polyurethane can be divided into internal emulsification method and external emulsification method. Internal emulsification method refers to the presence of hydrophilic components in the polyurethane chain segment, so a stable emulsion can be formed without emulsifier; external emulsification method refers to molecular emulsification method, in which the molecular chain contains only a small amount of hydrophilic segments or groups that are not sufficient for self-emulsification, or does not contain hydrophilic components at all. Emulsifier is added and mechanical stirring is used to force dispersion into a stable emulsion. Its characteristics are as follows:

Comparatively speaking, in the emulsion prepared by the external emulsification method, the residual amount of hydrophilic small molecule emulsifier is large, which affects the performance of the polyurethane coating after curing, and the internal emulsification method eliminates this shortcoming. Therefore, the preparation of waterborne polyurethane is mainly based on the ionic internal emulsification method, and the internal emulsification method can be divided into anionic waterborne polyurethane, cationic waterborne polyurethane, non-ionic waterborne polyurethane, etc. according to the different hydrophilic chain extenders.

According to the method of use, waterborne polyurethane can generally be divided into one-component waterborne polyurethane and two-component waterborne polyurethane. One-component waterborne polyurethane can be used directly, is easy to operate, and has a long open time; isocyanate curing agent needs to be mixed evenly before use, and the mixed glue must be used up within a certain period of time.

Composition of waterborne polyurethane

Waterborne polyurethane is mainly composed of macromolecular polyols, polyisocyanates, hydrophilic chain extenders, chain extenders, salt forming agents, catalysts, crosslinking agents and other additives.

Other additives

According to industry needs and laws and regulations, defoamers, leveling agents, thixotropic agents, light stabilizers, antioxidants, etc. are often required.

Application of waterborne polyurethane

Waterborne polyurethane has the advantages of low VOC, low odor, non-flammable, easy to modify, and excellent mechanical properties. It is widely used in adhesives, inks, leather finishing, automotive paints, and high-grade wood paints.