Study on associating thickening mechanism and structure–efficiency relationship of hyperbranched waterborne polyurethane

The rheological behavior of waterborne polyurethane dispersion (PUD) thickened by the hyperbranched waterborne polyurethane (HWPU) was studied by rheological measurements. The results showed that the flow activation energy depended on the structure and concentration of HWPU. Based on the relationship between the structure, concentration and flow activation energy, we could infer that during HWPU associating thickening process PUD experienced Duckweed state (appropriate HWPU-latex particles linker), 3D network structure (HWPU-latex particles three-dimensional network) or Bead-like texture (HWPU monomolecular micelles or multi-molecular micelles). The role of interaction between particles in the structure of thickening system was explored by dynamic light scattering, refraction analysis and fluorescence spectroscopy. The combination of hydrophobic groups of HWPU with latex particles resulted in associating thickening, while the intramolecular or intermolecular association of HWPU might lead to a decrease in thickening efficiency or no thickening.