Rheological Properties Of Modified Xanthan Gum

In order to improve the performance of xanthan gum(XG)and broaden its application,XG was chemically modified in this paper.Amphoteric xanthan gum(AXG),hydrophobic amphoteric xanthan gum(HAXG)and carboxymethyl hydroxypropyl xanthan gum(CMHPXG)were prepared,and the effects of preparation condition on the XG derivatives were investigated.Rheological behaviors of XG derivatives were also studied by rheology method,and the gel-breaking process of AXG solution was further studied.The amphoteric xanthan gel with good properties was prepared by crosslinking AXG with organic zirconium,and the rheological properties of the gel and its gelation process were further studied.The detail works are as follows:1)Xanthan gum was chemically modified by cationic reagent(3-chloro-2-hydroxypropyl triethylammonium acetate),hydrophobic cationic reagent(3-chloro-2-hydroxypropylhexadecyl ammonium acetate),propylene oxide and sodium chloroacetate,respectively.Amphoteric xanthan gum,hydrophobic amphoteric xanthan gum and carboxymethyl hydroxypropyl xanthan gum were prepared,and their proper preparation condition were obtained.2)The properties of xanthan gum and its derivatives were studied by rheological method,and the flow curve was described by rheological constitutive equation.Due to the electrostatic interaction between AXG molecules,electrostatic interaction and hydrophobic interaction between HAXG molecules and hydrophilic groups on CMHPXG molecules,the rheological properties of the three xanthan gum derivatives were significantly enhanced.3)For the breaking process of amphoteric xanthan gum,the effects of technological conditions(temperature and concentration of ammonium persulfate)on the rheological index(loss factor and viscoelastic modulus)in the gel-breaking process were determined.The complex viscosis-time curve of AXG solution was described by rheokinetics equation.At the beginning of gel breaking,the elasticity modulus of AXG solution decreased more rapidly than that of viscosity modulus,and at the end of gel breaking,the decrease rate of elasticity modulus is more slowly than that of viscosity modulus.4)The gel system of organic zirconium crosslinked AXG was obtained and the properties of AXG gel were studied by rheological method.The AXG gel behave shear thinning,and the viscoelasticity of AXG gel increased with the increase of organic zirconium.5)For the crosslinking process of amphoteric xanthan gum,the effects of technological conditions such as pH,temperature and amount of organic zirconium on the rheological index(viscoelastic modulus and complex viscosity)during gelation were determined.For the breaking process of AXG gel,the effects of technological conditions(temperature and concentration of ammonium persulfate)on the rheological index(complex viscosity and viscoelastic modulus)in the gel-breaking process were determined.And the crosslinking and gel-breaking process of AXG gel were described by using the rheokinetics equation.This study is expected to provide a rheological basis for the application of xanthan gum.