A Preliminary Method for Identifying Xanthan Gum and Welan Gum

Welan gum and xanthan gum are all anionic bio-saccharide, their water solutions all have pseudo-plastic fluid characteristics and similar appearance. Welan gum has properties that are superior to those of xanthan gum, and its price is much higher than that of xanthan gum, which render necessity and importance to regulate market application and identification of the two bio-saccharides. The characteristics of the two saccharides were compared by IR spectroscopy, viscosity change with temperature and their performance in cement slurries. The results of the experiments show that the two bio gums have generally similar IR spectra, a methyl group on the unique rhamnose ring of the welan gum molecular structure has a unique absorption peak around 2,978 ± 2 cm⁻¹. At shear rate of 0.5 s⁻¹, temperature between 25 ℃ and 180 ℃, and mass concentration of 0.4%, the viscosity – temperature curves of the two gums run against each other; the viscosity of xanthan gum decreases with temperature while the viscosity of welan gum increases with temperature. At 65 ℃, a cement slurry with water/cement ratio of 1.0 treated with 0.4% welan gum has stable properties, while the same cement slurry treated with 0.4% xanthan gum does not. Using these three differences shown by xanthan gum and welan gum together, preliminary identification of xanthan gum and welan gum can be made.