Effects of ionic interactions between clay and waterborne polyurethanes on the structure and physical properties of their nanocomposite dispersions

A waterborne polyurethane (WPU)/clay dispersion is electrostatically stabilized by COO− ions of WPU. Meanwhile, a stable electrical double layer is formed around each WPU/clay particle. The cations of clay platelets interact with COO− ions and interfere with the double layer of a pristine WPU dispersion. The WPU/clay dispersion, disturbed by ionic clay platelets, has fewer effective hydrophilic groups for stabilization in water. This leads to a larger particle size. Moreover, a WPU/clay dispersion with a higher clay concentration exhibits a higher viscosity. This is due to the stronger electrostatic interactions among a larger quantity of clay ions.