Rheological experiment and fractional derivative model for aqueous polyurethane dispersion

Rheology of aqueous polyurethane dispersion (PUD) has a significant influence on the industry process. In this study, the aqueous PUD used in warp knitted vamp printing was characterized by Fourier transform infrared (FTIR) spectra, dynamic light scattering and laser Doppler electrophoresis. Characterization results reveal that aqueous PUD shows bimodal and broad particle size distributions as well as negative surface charges. Aiming at studying the influence of rheological property on industrial applications of aqueous PUD, dynamic oscillating shear experiments were performed, and its constitutive equation was deduced. Experimental results suggest that temperature has no distinct effect on the linear viscoelastic range, in which aqueous PUD shows a solid-like behavior. In view of advantages of fractional order constitutive equation describing the viscoelasticity of fluid, this paper optimize the fractional order element to derived fractional Zener (FZ) and Poynting-Thomson models, and FZ model performs the better. Furthermore, the application and analysis of fractional order model provide theoretic guide for industrial process in warp knitted vamp printing.