Steady rheological behaviors of UV-curable waterborne hyperbranched polyurethane acrylate dispersions

A rotational rheometer was used to investigate the steady rheological behaviors of UV-curable waterborne hyperbranched polyurethane acrylate dispersions (WHBPUADs). The flow curves of WHBPUADs were fitted mathematically using the Cross model. The effects of many factors including solid content, concentration of hydrophilic groups, and degree of neutralization on the rheological behaviors were studied and discussed. It was found that the viscosity of WHBPUAD decreased with increasing shear rate, indicating that WHBPUAD was pseudoplastic. On the other hand, at the same shear rate, the viscosity of WHBPUAD increased with increasing solid content and degree of neutralization but decreased with increasing concentration of hydrophilic groups. The Cross model could describe the flow curve of WHBPUAD accurately, with square of correlation coefficient (R ²) above 0.9. Moreover, most of the zero-shear viscosity values (η ₀) obtained by the Cross model were located in the range of 0.2–10 Pa·s, which could fully meet the practical application requirement.