Current problems with waterborne polyurethane adhesives:
(1) Low solid content: At present, the solid content of water-based polyurethane (WPU) can reach 45%. Fewer systems lead to higher drying and transportation costs. Increasing the solid content leads to an increase in the viscosity of the system, which makes emulsification and dispersion difficult. Reduced emulsion stability.
(3) Poor wetting performance: The surface tension of water is three times greater than that of ordinary solvents. Using water as a solvent has poor wetting ability on low-energy surfaces.
(4) Poor initial adhesion performance: The unmodified water-based polyurethane adhesive has a lower initial viscosity than the modified one, and has a greater impact on construction.
(5) Poor water resistance and heat resistance: Most water-based polyurethane adhesives are linear thermoplastics, and their molecular chains contain hydrophilic groups, which results in poor water resistance and heat resistance.
(6) Poor storage stability: The storage stability becomes worse as the solid content of the water-based polyurethane adhesive system increases and the degree of cross-linking increases.
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