Unique viscosity mutation of multi-generation hyperbranched waterborne polyurethane

Abstract

Different generation hyperbranched polyurethanes (HBPUs) were synthesized through the A 2 +B'B 2 strategy. The molecular structures and viscosity were characterized by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). The NMR results confirmed the formation of the branched units between the segments contained in the HBPU structure. The GPC with a four-capillary bridge design differential viscometer and the Ubbelohde viscometer showed a different viscosity. For the HBPUs, the viscosity first increased to higher values then decreased to lower values, and finally increased with increasing weight, which can be attributed to the spherical structure. The growth degree of HBPUs spherical structure depends on the forming hydrogen bonds; when the hydrogen bonds reach a certain degree, the spherical structure becomes compact.

Novel Waterborne UV-Curable Hyperbranched Polyurethane Acrylate/Silica with Good Printability and Rheological Properties Applicable to Flexographic Ink

“…Figure 7a shows that the viscosity of ink will decrease with increasing content of HBWPUA/SiO 2 , which can be explained by the fact that viscosity is affected by intermolecular forces. 25,26 The higher the HBWPUA/SiO 2 content, the lower the number of particles in the multiunit system, causing less twine and physical interaction between particles, which decreases the viscosity. With the increase of shear rate, at first, the ink remains stable like Newtonian fluid, and then the viscosity decreases and the ink behaves like pseudo-plastic fluid, finally approaching a constant value.…”

Continuous Production of Water-Borne Polyurethanes: A Review

“…The viscosity of water-borne polyurethanes is low and it can be adjusted by adding water-soluble thickening agents and water. In addition to external polymer thickening agents, ion charge, core-shell structure, and emulsion particle size also affect the viscosity [18]. The higher the density of free radicals in the main chain and side chains of water-borne polyurethanes, the greater the viscosity of the resulting polyurethane emulsion.…”