Waterborne polyurethane is a kind of polymer material containing repetitive urethane unit. Because it uses water as a dispersion medium, it has the characteristics of low VOC, non-flammable, easy to store, friendly to human body and environment compared with traditional solvent-based polyurethane. Today, with the increasing emphasis on health and environmental protection, waterborne polyurethanes are used more and more widely, such as paints, synthetic leather, adhesives, fabric treatment, construction and other fields.

 

Waterborne polyurethanes are mostly linear or micro-crosslinked during the synthesis process. The synthesis method results in a small molecular weight and a low degree of crosslinking, which ultimately results in a difference in performance between the aqueous polyurethane and the solvent-based polyurethane. In order to improve the performance of waterborne polyurethanes, aqueous polyurethanes are often modified by cross-linking techniques. Compared with the internal cross-linking method, the emulsion obtained by the diplomatic association can more easily combine the advantages of other polymer materials and reduce the product cost. At present, the external crosslinking agent mainly includes alkoxylated melamine/formaldehyde, polyfunctional cyanoamide, polyfunctional aziridine, tolyl cyanoamide/triglycidyl ester, polyisocyanate, amino resin, epoxy crosslinking agent, etc. .

 

The water-containing polyurethane contains a hydroxyl group or an amino group mainly using an external crosslinking agent such as an aqueous polyisocyanate, a propylene oxide compound, an aziridine compound or an amino resin; and when an aqueous polyurethane contains a carboxyl group, an amino resin and an aziridine compound are often considered. An external crosslinking agent; for an aqueous polyurethane containing a specific group, a corresponding external crosslinking agent can be selected according to the reaction characteristics of the group itself.

 

The modified water-based polyurethane can be compared with the traditional solvent-based polyurethane in terms of handling process, bonding properties and physical and chemical properties.