Study On The Rheological Properties Of Sodium Methyl Stearate Lamellar Liquid Crystal Emulsion

Lamellar liquid crystal(LLC)emulsion is a hot issue in skin care products.In this paper,new LLC systems composed of amino acid surfactant sodium N-stearoyl-N-methyl taurine(SMT),hexadecanol,oil,water soluble polymer(xanthan gum T,hydroxyethyl cellulose,carbomer)and water were studied.The influence of type and content of oil and water soluble polymer on the structure and rheological properties of LLC systems were investigated.Constitutive equations of these LLC systems were established.The rheological properties of emulsion in cooling process were studied for the first time.The stability and rheological properties of the system under different temperature were investigated.Main conclusions were obtained as follows.1)The lamellar liquid crystal was confirmed by polarizing microscope.The influence of type and content of oil and water soluble polymer on the formation of liquid crystal were achieved.A new LLC system(SMT/hexadecanol/M318/carbomer U20/water)was obtained.2)Rheological properties of these LLC systems were investigated.These LLC systems exhibited well viscoelasticity and shear thinning properties.The viscosity curve could be described by nonlinear co-rotational Jeffreys constitutive equation.The elastic modulus of these LLC systems were greater than the viscous modulus,indicating the formation of network.3)The shear rheological properties of LLC systems in cooling process were divided into three sections.The rheological properties of LLC systems did not change with temperature at 60?80?.The rheological properties of LLC systems vary rapidly with the decreasing of temperature at 50?60?.The rheological properties of LLC systems did not change with temperature at 25?50?.Four parameter model was established for the first time to describe the viscosity and elasticity modulus of these LLC systems change with temperature.Four parameter rheological dynamics equations characterized the change of viscosity with time.The relationship between microrheological properties(elastic index El,macroviscosity index MVI,solid-liquid balance SLB and flow index FI)and temperature of these LLC systems in cooling process were explicited for the first time.The results were consistent with the shear rheology properties in cooling process.4)The stability of LLC system showed that storage temperature influenced liquid crystal structure and rheological properties.The relationship between rheological properties and stability of the LLC system was defined.The results obtained in this paper are expected to provide rheological basis for the application of lamellar liquid crystal with amino acid surfactant.