Rheological properties of modified xanthan and their influence on printing performances on cotton with reactive dyes in screen printing

In this study, various modified xanthan gums (MXG) were prepared by deacetylation under alkali treatment at certain temperature. The molecular weight of xanthan gum decreased after alkali modification. Rheological properties such as flowability, thixotropy and viscoelasticity were investigated via steady-shear, transient and dynamic oscillatory tests. The results showed that the flowability and viscous effect of MXG increased, while the structural viscosity and elastic effect decreased with increasing degrees of modification. Compared to xanthan gum, printing performances using MXG as a thickener were improved, especially the screenability, color yield and penetration. In addition, the quantitative interpretation of the rheological parameters, which are strongly associated with the quality-determining parameters, was obtained using rheological models (the power-law and Friedrich-Braun models). Excellent printing performances were achieved by applying MXG under the appropriate modification conditions. These thickeners, which have better flowability, more viscous behavior and smaller structural viscosity, might be good pastes to meet the the requirements of cotton printing with reactive dyes.