SYNTHESIS, CHARACTERIZATION AND PROPERTIES OF ACETYLATED GUAR GUM

This research aimed to acetylate guar gum (GG) in granular form in order to improve its hydrophobicity. Acetylated guar gum (AGG) was synthesized using acetic anhydride as acetylating reagent and pyridine as solvent to obtain better property combination. By polarized light microscopy, infrared spectrometry, differential scanning calorimetry and thermogravimetric analyses, the appearance, structure and thermal properties of AGG were observed, characterized and measured, respectively. The most suitable process conditions for preparing AGG were found to be: reaction time of 3 h, reaction temperature of 90 degrees C and amount of pyridine of 50%. The acetylation reduced the freeze-thaw stability and the swelling power of GG, but increased its retrogradation and cold and hot viscosity stability. The appearance of GG was not changed by the acetylation. The acetylation was able to increase the onset decomposition temperature, peak temperature, final decomposition temperature and melting enthalpy of guar gum, but lowered the thermal stability of guar gum.