The 6 characteristics of water-based polyurethane are as follows:

Most water-based polyurethane adhesives do not contain -NCO groups, so they mainly rely on the polar groups within the molecules to generate cohesive forces and adhesive forces for curing. Solvent-based or solvent-free one-component and two-component polyurethane adhesives can fully utilize the reaction of -NCO to enhance the bonding performance during the bonding and curing process. Water-based polyurethane contains carboxyl and hydroxyl groups, which can participate in reactions under suitable conditions to make the adhesive cross-link.

In addition to added polymer thickeners, important factors that affect the viscosity of water-based polyurethane include ion charges, core-shell structure, and emulsion particle size. The more ions and counterions （free ions in the solution that are opposite in polarity to the ion groups contained in the main chain and side chain of polyurethane） there are on the polymer molecules, the higher the viscosity. The influence of factors such as solid content （concentration）, molecular weight of polyurethane resin, and cross-linking agent on the viscosity of water-based polyurethane is not significant, which is conducive to the high molecular weight of polyurethane to improve the cohesive strength of the adhesive. In comparison, the main factors affecting the viscosity of solvent-based polyurethane adhesives are the molecular weight of polyurethane, branching degree, concentration of the adhesive, etc. At the same solid content, the viscosity of water-based adhesives is smaller than that of solvent-based adhesives.

Viscosity is an important parameter for the performance of adhesives. The viscosity of water-based polyurethane is generally adjusted by water-soluble thickeners and water. Solvent-based adhesives can be adjusted by increasing the solid content, molecular weight of polyurethane, or choosing appropriate solvents.

Due to the poorer volatility of water than organic solvents, water-based polyurethane adhesives dry more slowly, and due to the large surface tension of water, their ability to wet hydrophobic substrates is poor. If most of the water has not evaporated from the bonding layer or coating into the air, or has been absorbed by porous substrates during heated drying, it is difficult to obtain a continuous layer of adhesive.

Water-based polyurethane adhesives can be mixed with various water-based resins to improve performance or reduce costs. At this time, attention should be paid to the ionic properties and acidity and alkalinity of the ionic water-based adhesives, otherwise condensation may occur. Due to the influence of compatibility between polymers or solubility in certain solvents, solvent-based polyurethane adhesives can only be blended with a limited number of other resin adhesives.

Water-based polyurethane adhesives have a small odor, convenient operation, and easy residue removal, while solvent-based polyurethane adhesives sometimes require a large amount of solvent consumption during use, and the cleaning process is not as convenient as that of water-based adhesives.

Solution to the problem of waterborne polyurethane adhesive debonding: Water-based polyurethane adhesives are widely used in the adhesive and flocking fields of automotive interiors, such as glove boxes, storage boxes, and central armrest boxes. However, in automotive interior parts, PP materials are widely used. Due to the non-polar nature of PP materials, it is difficult to bond the surface, and problems such as debonding between the PP substrate and the water-based polyurethane adhesive often occur. An effective solution is to pretreat the surface of the PP material, apply a layer of PP treatment agent between the substrate and the adhesive to enhance the bonding strength, and solve the problem of unreliable bonding and debonding.