Frank L. Saunders

Rheological properties of monodisperse latex systems I. Concentration dependence of relative viscosity

Abstract The relations of relative viscosity ηr to volume fraction φ for a series of monodisperse polystyrene latexes were determined for particle diameters between 990 A and and 8710 A. Volume fractions up to about 0.25 were considered above which the latexes were non-Newtonian as indicated from flow curves obtained with a rotational viscometer. Experimental results obtained with a capillary viscometer appeared to fit the general equation ηr = exp. α0φ/1 − kφ with a value of 2.504 for α0 in good agreement with the Einstein coefficient of 5 2 . The constant α0 was found to be independent of particle diameter provided the measured volume fraction was corrected for an adsorbed layer of emulsifier. The interaction coefficient k varied from 1.118 to 1.357 increasing with decreasing particle diameter.

The effect of methylcellulose on the electrolyte stability of dilute synthetic latexes

Abstract The effect of Methocel (Dow methylcellulose) on the electrolyte stability of dilute synthetic latexes has been studied using a centrifuging technique in conjunction with turbidity measurements as a means of determining stability. Stability studies on dilute styrene latexes appear to conform to the general concepts associated with hydrophobic colloids. The effect of the addition of Methocel on the electrolyte stability of the dilute latex is similar to the sensitizing and protecting action exhibited by certain hydrophilic colloids on hydrophobic colloids. The protecting effect occurs at approximately theoretical surface coverage of the latex particles by a monolayer of Methocel. The electrolyte stability under these conditions is much less sensitive to small changes in electrolyte concentration. The molecular weight of the Methocel does not appreciably affect the amount necessary for the protecting action. With addition of emulsifier to the diluted latex, the amount of Methocel required for the protecting effect is decreased and precluded from adsorption when the particles are covered by emulsifier.

Adsorption of methylcellulose on polystyrene latexes

Abstract The adsorption of sodium lauryl sulfate and methylcellulose on monodisperse polystyrene latexes has been studied to determine the effect of emulsifier surface coverage on the adsorption of methylcellulose. A differential refractive index technique has been used to determine the concentration of the adsorbate in the serum phase of the centrifuged latex. With latexes containing added sodium lauryl sulfate to vary the surface coverage of the latex by emulsifier, the amount of methylcellulose that was adsorbed depended on the amount of free surface available. Esentially no methylcellulose was adsorbed on the latex having complete surface coverage by emulsifier. The effective molecular adsorption area for a methylcellulose monomer unit was found to be ∼33 A 2 .

Rheological properties of monodisperse latex systems: Flow curves of thickened latexes

Abstract The rheological flow curves of a series of monodisperse polystyrene latexes thickened with methylcellulose and soya protein have been measured with a rotational viscometer. The effects of latex particle size and thickener concentration on thixotropy, yield value, and plastic viscosity are compared for the two thickeners.

Adsorption of Methylcellulose on Polystyrene Latexes

The adsorption of sodium lauryl sulfate and methylcellulose on monodisperse polystyrene latexes has been studied to determine the effect of emulsifier surface coverage on the adsorption of methylcellulose. A differential refractive index technique has been used to determine the concentration of the adsorbate in the serum phase of the centrifuged latex. With latexes containing added sodium lauryl sulfate to vary the surface coverage of the latex by emulsifier, the amount of methylcellulose that was adsorbed depended on the amount of free surface available. Esentially no methylcellulose was adsorbed on the latex having complete surface coverage by emulsifier. The effective molecular adsorption area for a methylcellulose monomer unit was found to be ~33 A 2 .