Synthesis and characterization of waterborne polyurethane thickeners based on hyperbranched polyester

Octahydroxyl-terminated and hexadecahydroxyl-terminated hyperbranched polyesters (HPE-8 and HPE-16) were synthesized from 2,2-dimethylol propionic acid and 1,4-butanediol. The hyperbranched waterborne polyurethane (HWPU) thickeners containing different branching structure and length of hydrophilic chain were prepared with hexamethylene diisocyanate, polyethylene glycol (PEG), cetyl alcohol, and HPE. The structures of HPE and HWPU were characterized by Fourier transform infrared spectra and nuclear magnetic resonance ( 1 H NMR and 13 C NMR). The rheological properties of polyurethane emulsion thickened by HWPU were measured using Brookfield LVDV-III rheometer, and the effects of HPE structure and PEG molecular weight on the thickening property of HWPU were studied. The results showed that HWPU with HPE branching number of 8 and PEG molecular weight of 4000 exhibited an excellent thickening effect in the aqueous polyurethane emulsion.