Alkyl Modified Siloxane manufacturer introduces the 6 major characteristics of adhesives :
1. Most water-based polyurethane adhesives do not contain -NCO groups, so they mainly rely on the cohesion and adhesion of the polar groups in the molecule for curing, while solvent-based or solvent-free one-component and two-component Polyurethane adhesives can make full use of the -NCO reaction to enhance the bonding performance during the bonding curing process. The water-based polyurethane contains carboxyl, hydroxyl, and other groups, which can participate in the reaction under appropriate conditions to cause the adhesive to crosslink.
2. In addition to the external polymer thickener, important factors affecting the viscosity of waterborne polyurethane are ion charge, core-shell structure, emulsion particle size, etc. The more ions and counterions on the polymer molecule, the greater the viscosity and the solid The content (concentration), the molecular weight of the polyurethane resin, the crosslinking agent, and other factors have no obvious influence on the viscosity of the waterborne polyurethane, which is conducive to the high molecular weight of the polyurethane to improve the cohesive strength of the adhesive.
3. Viscosity is an important parameter of adhesive performance. The viscosity of water-based polyurethane is generally adjusted by water-soluble thickener and water, while solvent-based adhesives can be adjusted by increasing the solid content, the molecular weight of the polyurethane, or selecting a suitable solvent.
4. Because water is less volatile than organic solvents, water-based polyurethane adhesives dries slowly, and because of the large surface tension of water, the ability to wet the surface hydrophobic substrate is poor. If most of the water has not been removed from the adhesive layer, The coating volatilizes into the air, or it is heated and dried after being absorbed by the porous substrate, it is difficult to obtain a continuous glue layer.
5. The water-based polyurethane adhesive can be mixed with a variety of water-based resins to improve performance or reduce costs. At this time, attention should be paid to the ionic nature and acidity and alkalinity of the ionic water-based adhesive, otherwise, it may cause agglomeration. Because of its compatibility or solubility in certain solvents, solvent-based polyurethane adhesives can only be blended with a limited number of other resin adhesives.
6. The water-based polyurethane adhesive has a small odor, is easy to operate, and the residual glue is easy to clean. However, solvent-based polyurethane adhesives sometimes need to consume a lot of solvents, and cleaning is not as convenient as water-based adhesives.