Emulsion rheology and properties of polymerized high internal phase emulsions
High internal phase emulsions are highly concentrated emulsion systems consisting of a large volume of dispersed phase above 0.74. The rheological properties of high internal phase water-in-oil emulsions were measured conducting steady shear, oscillatory shear and creep/recovery experiments. It was found that the yield stress is inversely proportional to the drop size with the exponent of values between 1 and 2. Since the oil phase contains monomeric species, microcellular foams can easily be prepared from high internal phase emulsions. In this study, the microcellular foams combining a couple of thickeners into the conventional formulation of styrene and water system were investigated to understand the effect of viscosity ratio on cell size. Cell size variation on thickener concentration could be explained by a dimensional analysis between the capillary number and the viscosity ratio. Compression properties of foam are important end use properties in many practical applications. Crush strength and Young's modulus of microcellular foams polymerized from high internal phase emulsions were measured and compared from compression tests. Of the foams tested in this study, the foam prepared from the organoclay having reactive group as an oil phase thickener showed outstanding compression properties.
Yield stress and viscoelastic properties of high internal phase ratio emulsions
Abstract The rheology of high internal phase ratio oil-in-water emulsions was investigated using a controlled-stress rheometer. The dispersed-phase (oil) concentration was varied from 71.24 to 89.61% by volume. Three different types of rheological experiments were conducted for each emulsion, namely: steady shear, oscillatory shear, and creep/recovery experiments. All the emulsions investigated in this study possess a yield stress. The yield-stress values obtained from different rheological experiments for the same emulsion show good agreement with each other. The yield-stress value increases exponentially with an increase in the dispersed-phase concentration. The yield-stress data of this study can be described quite well with the Princen and Kiss equation for high internal phase ratio emulsions provided that the thickness of the interdroplet films is taken into account. For any given emulsion, the storage modulus, measured in the linear viscoelastic region, is found to be constant, independent of the frequency, indicating a solid-like behaviour. The value of the storage modulus increases with an increase in the dispersed-phase concentration. The storage modulus data are interpreted in terms of the Princen and Kiss equation.
Viscoelastic properties of concentrated emulsions
A. Introducrion _ . . . _ . _ _ _ _ _ _ _ _ _ _ . . . . . . . B. The nature of viscoelastic behavior . . . . . . (i) Model representation of linear viscoelastic behavidr : : : : : : : : : (ii) The Maxwell model (iii) The Voigt (Kelvin) model’ : : : : : : : : : : : 1 : : : : 1 C. Methods of viscoelastic analysis . . _ _ _ _ . . _ . . . . . . . (i)The creep test . . . . . . . . . . . . . . . . . . . . . (ii) Dynamic analysis _ . . . . . . . . . . . _ _ _ _ _ _ _ _ (iii) Transformation of creep to dynamic parameters . . . _ _ . . . . . D. Self-bodied oil-in-water emulsions . . _ . . . . . . . . . . . _ (i) Nature of self-bodied emulsions _ _ _ __ . _ , , . . . . . (ii) Ternary systems and emulsions based on surfaetant/lbng edain alcohol/water. (iii) Kinetics of gel network formation _ . _ . _ . . . . _ . . . . (iv) Influence of temperature (v) Effect of mixed emulsifier cdnckt_ration_ : : : : : 1 : : : : 1 1 (vi) Influence of surfactant chain length . . . . _ _ _ . . . . . . . (vii) Influence of alcohol chain length . . . . . . . . . . . . . . . (viii) Correlation of v-kcoelastic functions from creep and oscillation . . . . . (ix) Summary. . . . . . . . . . . . . . . . . . . . . . . E. Water-in-oil emulsions . . . _ . . _ _ . . _ . _ . _ . . . . . F. Conclusion _ . . . . . . . . . . . . . . . . . . . . . . References _ . . . . . . _ _ . . . . . _ . . . . . . . _ . . 39 40 40 41 -12 44 44 48 54 57 57 58 59 61 62 66 69 70 71 71 73 74