Investigation On Modification Of Guar Gum Using Amino Acid

With the rapid development of society,petroleum resources are gradually depleted.Meanwhile,energy shortage and environmental pollution are becoming more and more serious.Natural biomaterials have attracted more and more attention due to their advantages of wide source,renewable and degradable.The natural polysaccharide of guar gum extracted from guar is widely used as a thickener in the daily chemical field because of its biocompatibility,degradability,non-toxicity,harmlessness and high viscosity.As the smallest unit of protein,amino acid is one of the essential substances needed by the human body.Modifying guar gum with amino acids can endow guar gum with the biological characteristics of amino acids and increase the affinity between guar gum and skin.In this project,amino acid modified guar gum was prepared by two methods:p-toluenesulfonyl chloride method and epichlorohydrin method.Glycine-modified guar gum was prepared by the p-toluenesulfonyl chloride method.TGA and DSC analysis showed that the thermal stability of glycine-modified guar gum decreased and the melting temperature increased.The determination of S element showed that glycine could not completely replace p-toluenesulfonyl group,which could also be indirectly verified by FTIR and TGA.The influence of the addition amount of p-toluene sulfonyl chloride on the solubility of the product was tested.The results showed that the product did not dissolve when the addition amount of p-toluene sulfonyl chloride was higher than1/11.Glycine modified guar gum was prepared by epichlorohydrin method,and its structure was characterized by FTIR and ¹³C NMR.The results showed that Glycine modified guar gum was successfully prepared.The synthesis formula and process conditions were optimized to determine the amount of glycine and guar gum 1:1.The reaction temperature is 50℃,and the reaction time is 5 h.The analysis results of heat resistance determined by TGA and DSC were consistent with those determined by p-toluene sulfonyl chloride method.The salt resistance and acid alkali resistance of the aqueous solution modified by glycine were better than guar gum.After 5 cycles of freeze-thaw,the aqueous solution appeared to precipitate,which indicated that the gel solution had poor freeze-thaw stability.The transmittance of guar gum modified by glycine was lower than 50%.According to the ash content,the unreacted impurity molecules can be completely removed by washing the product with 70%ethanol water solution for 4 timesThe hydrogen bond association of guar gum is serious.Glycine modified guar gum has poor solubility and low light transmittance.The hydroxypropyl guar gum was modified by hydroxypropylation.The optimum reaction conditions were determined by orthogonal experiment.When the degree of substitution is 1.72,the light transmittance of the solution can reach more than 98%.Glycine modified hydroxypropyl guar gum was prepared by epichlorohydrin method.The results showed that the ratio of glycine to hydroxypropyl guar gum was 0.8:1,the reaction temperature was 55℃,and the reaction time was 5 h.TGA and DSC results showed that the thermal stability and melting temperature of glycine modified hydroxypropyl guar gum were lower than those of hydroxypropyl guar gum and glycine modified guar gum,respectively.Glycine modified hydroxypropyl guar gum has good salt resistance and acid and alkali resistance.After freeze-thaw cycle,the water solution does not appear to precipitate,and the light transmittance of the glue solution can reach more than 98%.Hydroxypropyl guar gum modified by glycine has good structural stability,salt resistance,acid and alkali resistance,and has good development and utilization value.On the basis of the basic formula of mask essence,adding glycine modified hydroxypropyl guar gum as thickening agent,the essence is uniform and easy to be coated,almost without bubbles,which improves the sticky feeling of thickeners such as carbomer or xanthan gum commonly used in the market.Mask essence has low water loss rate,good water retention,high skin absorption rate,good heat resistance,cold resistance and centrifugal stability,which is expected to become a new thickener for facial mask essence.