Rheology application emulsions

At an applied level, study of the rheology of emulsions is vital in many industrial applications of personal care products. It is useful to summarize the factors that affect emulsion rheology in a qualitative way. One of the most important factors is the volume fraction of the disperse phase, ( ). In very dilute emulsions (( )< 0.01), the relative viscosity, Tir, of the system may be related to ( ) using the simple Einstein equation (as for solid/ liquid dispersions) (15) i.e.. 

Tadros T (2004) Application of rheology for assessment and prediction of the long-term physical stabdity of emulsions. Adv CoU Interface Sci 108 227-258 Talibuden O (1981) Cation exchange in soils. In Greenland DJ, Hayes MHB (eds) The chemistry of soil processes. WUey, Chichester, pp 115-178 Taylor AW, Spencer WF (1990) Volatilization and vapor transport processes. In Cheng HH (ed) Pesticides in the soil environment. Soil Sci Soc Amer Book Ser 2, Madison, Wisconsin, pp 213-369... 

In much of the work on rheology, foams and HIPEs have been considered as analogous. The expressions derived are applicable to both systems, only the actual values are different. Consequently, workers in this area choose to study either emulsions or foams (or both) and so, in this section, the rheological properties of HIPEs and high gas-fraction (or dry ) foams will be discussed jointly. 

In addition to suspensions, pharmaceutical products may be emulsions or foams. In any case the rheological properties have to be tailored to suit the nature of the application [215], Therapeutic ointments are usually not very viscous and encounter only moderate shear rates upon application, about 125 s-1 when gently smeared on with fingers, and about 210 s-1 when smeared on with a spatula [215], An opthalmic ointment is usually very soft, with a viscosity of about 20-30 mPas, whereas a medicated ointment needs to be soft enough to apply easily but stiff enough to remain on the area to which it was applied, with a viscosity of about 30-40 mPas [215], A protective ointment like zinc oxide paste needs to be hard and stiff enough to stay in place where applied, even when moist. 

Malhotra, A.K. Wasan, D.T. Interfacial Rheological Properties of Adsorbed Surfactant Films with Applications to Emulsion and Foam Stability in Thin Liquid Films, Ivanov, I.B. (Ed.), Dekker New York, 1988, pp. 829-890. 

New starch products might be derived from emulsion copolymerization with synthetic monomers and the replacement of all-synthetic polymers. Potential applications could be in flocculation, sizing, modified rheological characteristics, bonding to a wide range of substrates, film formation and in effluent treatment. A critical requirement will be the removal of hazardous residuals and Food and Drug Administration (FDA) approval for use in specific paper grades. 

Because of this interaction, PVP has found application in surfactant formulations, where it functions as a steric stabilizer for example to generate uniform particle-size polystyrene emulsions (110—112). In a variety of formulations, a surfactant s ability to emulsify is augmented by PVP s ability to stabilize colloids sterically and to control rheology. 

Many epoxy dispersions are compatible with most types of latex emulsions including acrylic, urethane, styrene butadiene, vinyl chloride, and polyvinyl acetate. The epoxy dispersion can be used as a modifier for these emulsions to alter handling and application characteristics such as emulsion rheology, foaming tendencies, pH sensitivity, wetting properties, and coating coalescence. They can also be reacted into the latex resin either by reacting the epoxy with a functionalized latex or by use of an epoxy with a coreactant. In this way adhesive systems can be formulated that are cured at room or elevated temperatures. 

Before we discuss the applications of US-based detection techniques, we should emphasize the difference between the measured data and the desired output parameters. In ultrasound spectrometry, the measured data can be the attenuation coefficient, the sound speed and the acoustic impedance. However, the researcher is rarely interested in these measured properties, but rather on elastic moduli of solid samples particle size distributions or rheological properties of heterogeneous samples and concentrations, rheology, stability and chemical reactivity of liquids (particularly emulsions). 

Acrylic emulsion copolymer with same advantages and applications as ACRYSOL TT-615 but not as efficient at low shear rates. Is less shear thinning and imparts a leggier rheology. 

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