Rheological properties of sodium alginate and xanthan pastes on cotton with reactive dye in screen printing

In this study, sodium alginate (SA) and xanthan (XG), selected as two typical pastes, were intensively investigated by steady, transient, and dynamic rheological methods. Compared with SA, in the steady-shear tests it was found that XG showed a prominent shear-thinning feature at low shear rates and low concentrations. In addition, the transient tests suggested that XG had more remarkable hysteresis thixotropy and that the structural viscosity needed more time to return to its original level after shears. What is more, two pastes in the same concentration performed totally different viscoelastic behaviors from the dynamic tests. SA exhibited more viscous behavior and XG more elastic behavior. Furthermore, experimental data have been correlated with different models: flow curves with the Cross and power-law model, mechanical spectra with the Friedrich-Braun model and Generalized Maxwell model. The relationship between dynamic and steady-shear properties (Cox-Merz rule) was satisfactory for SA while undesirable for XG. Through the rheological properties, it may be inferred that those who show weaker elasticity, stronger viscosity, relatively steady viscoelasticity, and the structural viscosity liable to restore the original level after shears may be more appropriate as the pastes to achieve better printing qualities on cotton printing with reactive dye.