Alleviation of the plastic deformation of gel ink under strong stress through an esterification of xanthan gum reinforcing its double helix structure

As a natural organic polymer, xanthan gum (XG) can alleviate the plastic deformation of gel ink under strong stress and realize the reasonable regulation of the rheological properties of gel ink. However, as the double-helix structure connected by hydrogen bonds cannot resist the mechanical environment of strong stress, XG shows poor shear resistance. In this study, a polymer gel with interpenetrating polymer network structure was prepared by esterifying XG, taking polystyrene maleic anhydride (SMA) as the modifier. In addition to retaining the excellent rheological properties of XG, the generated polymer gel also exhibited high shear resistance. The optimal addition amount of the esterification reaction modifier was determined as mXG: mSMA = 5:3 according to the gel ink standard. With this amount, the viscosity of the modified xanthan gum (SXG) gel increased to 1578.8 mPa·s and 100.7 mPa·s at shear rates of 4 s−1 and 383 s−1, respectively, and the shear resistance increased more than 2 times compared to the unmodified one. It is because of the ester bond formed by esterification that the reaction strengthens the interaction between molecular segments, enabling the new gel to resist to strong mechanical stress. The new polymer gel studied in this paper and the proposed mechanism of action provide new insights for the development of high-end gel ink and also provide theoretical support for the study of rheological properties of non-Newtonian fluids.