Waterborne polyurethane possess good film covering property in itself. If we introduce cationic chain extender at the time of compounding polyurethane, we can get cationic waterborne polyurethanne. The waterborne polyurethane dye-fixing principle is as follows:
1. Decreasing the solubility: there are large quantity of cation on the dye fixing agent molecular. It will combine with the anion of the dye and produce insoluble color lake, which will help to improve the water washing fastness.
2. Increasing the adhesion between dye and fabric. The carbamic acid ester in the dye-fixing agent is easy to combine with the fabric and forming the hydrogen bond, which will improve the fastness greatly.
3. Covering the dye and water soluble group. Waterborne polyurethane is net cross-linked structure. It have good film-forming property. Because of the relative molecular mass, it will cover onto the surface of the fabric and form a sealing film which will cover the color lake. By this way, it will improve the fabric’s color fastness, washing fastness and fastness to wet rubbing.
The extensive use of environment friendly dye-fixing agent represent the developing trend.The clean and environmental protection properties of waterborne polyurethane has opened up a new path for the development of dye-fixing agent. At present, waterborne polyurethane have shown certain fixing property, and the fabric overall performance have been improved after it is dealt with the modified waterborne polyurethane.But the waterborne polyurethane dye-fixing agent can not replace other types dye-fixing agent. So more studies still need to be done.
1. The modified waterborne polyurethane introduce long abdication chain, with less cation. So its ability to combine with inionic dye molecular and forming saline is weak. How to introduce more cation will be the lecture need to study.
2.There are large quantities of study that focus on the waterborne polyurethane fixing reactive dyes and dyeing cotton fabrics. But as dye-fixing agent, its study of fixing other dye and dyeing on the other fabrics is very less. How to modify the waterborne polyurethane and let it apply to varieties of dye and dyeing the fabrics with different materials is the study need to be done in future.
3. On the base of keeping the fabric’s original glossiness and improving the fabric’s fastness to wet rubbing, the study of developing waterborne polyurethane dye-fixing agent’s function is the trend. For example, by modifying treatment, after the finishing the fabric, the fabric will get more property,such as, anti-ultraviolet property, anti-microbial property, anti-radiation property and water-resistance property. We believe that, with the further study of the waterborne polyurethane, it is possible to develop broadly used modified waterborne polyurethane with better fastness, and other functions.