Abstract: The preparation of cross-linked guar gum was investigated by using epichlorohydrin as the cross-linking agent, sodium hydroxide as the catalyst and ethanol as the solvent in this study. The effects of epichlorohydrin amount, pH, reaction time, reaction temperature and alcohol concentration on the sediment volume of cross-linked guar gum was explored. The results showed that epichlorohydrin amount, pH, reaction time, reaction temperature and alcohol concentration had obvious impact on cross-linked reaction of guar gum. The optimal conditions for preparing cross-linked guar gum were epichlorohydrin amount of 8%, reaction time of 3.5 h, reaction temperature of 40 ℃ and ethanol concentration of 95%. Five reaction conditions were ranked in decreasing order of their effect on the sediment volume of cross-linked guar gum as follows: epichlorohydrin amount, reaction temperature, pH, reaction time and alcohol concentration. The thermal stability, enthalpy change, endothermic onset temperature, peak temperature and final temperature of cross-linked guar gum increased with increasing degree of cross-linking.

Key words: guar gum, cross-linking, epichlorohydrin, preparation