Water-based polyurethane dispersion is a kind of polyurethane particles dispersed in water and swollen. The particle size is mostly 0.01~5pm, which is smaller than that of acrylic emulsion. At present, there are three types of commercial polyurethane dispersions: anionic, cationic and nonionic. Anionic polyurethane dispersions are mostly used in the coatings industry . Its characteristics are: single component, and no free isocyanate, non-toxic. The film is formed at room temperature without the need for a film-forming agent, so the content of volatile organic compounds (VOC) in the system can be reduced to zero. Although its relative molecular weight is high , its viscosity is low, easy to process and easy to construct. Its mechanical properties are comparable to those of solvent-based polyurethane, and it has outstanding hardness, abrasion resistance and chemical resistance. And choosing different types of monomers and synthesis processes can make products with different characteristics of soft and hard. It is mainly used for coating and protection of wood (including wooden furniture and floors, etc.). Due to the relatively high cost, it is generally used in coating systems with high performance requirements.
However, water-based polyurethane dispersions used in wood lacquers are limited by other , such as poor wettability to wood, poor dispersibility to pigments, and poor weather resistance of aromatic polyurethanes. . Because acrylates have excellent weather resistance and good wettability to substrates and pigments, the development of polyurethane acrylate copolymer emulsions is becoming the focus of attention.
