Preparation And Characterization Of Hydroxypropyl Guar Gum

Guar gum, a water-soluble natural polymer, is often chemically modified to improve its physical and chemical properties. Pure and modified guar gums are widely used as thickeners or protective colloids in the food, textile, petroleum and mining industries. In this work, hydroxypropyl guar gum is prepared and characterized. The preparation is based on the reaction of guar gum with propylene oxide. The characterization is focused on the determination of molar substitution and the connection between guar gum and hydroxypropyl chain. Spectrometry and 1H NMR are used to determine molar substitution, and the results determined by the two methods are in good agreement. 13C NMR is used to assume the connection between guar gum and Hydroxypropyl and the length of polyoxypropyl chain. The effects of introduction of hydroxypropyl group are evident from rheological parameters such as r\0 and E. The n0 and E of hydroxypropyl guar gum are smaller for a given concentration than those of guar gum, and the decreases are morepronounced with the increasing of molar substitution. The introduction of hydrophobia hydroxypropyl group in guar gum is quite favorable for its practical application.