Rheological properties of amino-acid based anionic surfactants

The rheological properties of two types of anionic surfactant were investigated. The two surfactants were used, namely Sodium Cocoyl Glutamate [commercially known as Amisoft CS-11] and [commercially known as Amilite GCS-11]. Small angle X-ray scattering [SAXS] and polarizing microscope and used for phase identification and structure characterization. Both surfactants were found to form two-phase region and micellar region. Liquid crystalline phases, for both systems, were found to form at higher surfactant concentration. The rheological investigation indicated that amisoft system showed more solid-like behaviour than that of amilite system. The dynamic viscosity measurement, for the two systems, indicated shear thinning behaviour at low frequency while Newtonian behaviour was found at high frequency range

Modelling of fractional relaxation behaviour characteristic in polysaccharide systems

Fractional calculus has become an important tool in the analysis of slow relaxation phenomena, such as stress-strain relationships in polymeric materials. The Zener model is an extension of the Maxwell model, which consists of a spring and dashpot in series, with an additional spring in parallel. A fractional rheological description is obtained by replacing the first order time-derivatives in the Maxwell-Zener equation with fractional derivatives of order q and micro. The fractional Zener model relating stress to strain is used to fit several experimental results on polysaccharide. The comparisons between the experimental results and the theoretical predictions are found to be satisfactory

Characterization of vesicles of nonionic surfactant mixtures

Nonionic surfactant vesicles are now widely studied as an alternative to liposomes. In the present work, the vesicles were prepared using mixture of nonionic surfactants and the optical microscope with cross polarizers was used in order to observe the vesicles and capture the image. The mixtures of nonionic surfactants Synperonic NP5-dodecyl-beta-D-glycopyranoside [DGP] were prepared for different mol ratio. The critical micelle concentration [CMC] of nonionic surfactant Synperonic NP5 was determined using the tensiometer with Du Nouy ring methods. The effect of different types of salt, namely; KCI, NaCI and CaCl in the CMC was also investigated. The critical vesicle concentration [CVC] for the nonionic mixtures was determined using UV-Visible Spectrophotometer at room temperature. The size of the vesicles of the nonionic mixtures was measured using particle sizer. The CMC and CVC of nonionic vesicles were found to decrease with salt concentration while, the size of the vesicles was found to increase with the salt concentrations. In addition, the rheological behaviours of the nonionic vesicles were investigated. The samples of vesicles showed liquid-like behaviours which were indicated by the domination of the loss modulus, G". The effect of salt concentrations and salt types in the rheological behaviours was also investigated. The dynamic moduli were found to decrease with salt concentration while the effect of the salt types in the elastic and storage moduli was not significant

Influence of different oil types on the rheological behaviour of nonionic oil -in- water microemulsion

Microemulsions were formed at very low oil concentration in the ternary systems. These solutions are optically isotropic with low viscosity. The rheological behaviours of microemulsion of glucopone-water-hydrocarbon systems were investigated. Four different types of hydrocarbon namely heptane, octane, dodecane and tetradecane were considered. The frequency dependent storage and loss modulus were investigated below the critical strain. The critical strain is decreased as the alkane chain lengths increased. The zero shear viscosity was found to increase when longer hydrocarbon chain lengths were considered. However, when surfactant concentrations were further increased, the value of the zero shear viscosity appeared to be going down as the alkane chain length was increased. The discrepancy between the elastic and loss modulus in heptane and octane systems was higher than that corresponds to dodecane and tetradecane systems. The complex viscosity increased as alkane chain lengths of the hydrocarbon increase. In general, the effects of different types of hydrocarbon in the rheological behaviours were found to be more profound in the heptane and octane systems than in the dodecane and tetradecane systems