SURFACE TENSION EFFECTS IN THE SEDIMENTATION OF POLYMER PARTICLES IN VARIOUS LIQUID MIXTURES

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Abstract
The sedimentation volume, V sed of polymer particles in mixtures of pairs of nonpoiar as well as polar liquid combinations was determined at 20°C The liquid combinations were chosen such that the interfacial tension, γSV, of the polymer particles fell between the surface tensions of the two liquids. Constant: amounts of a given polymer powder were suspended in constant volumes of liquid mixtures of different concentrations It was found that the sedimentation volume changed with the composition and hence the surface tension of the liquid mixtures. A maximum or a minimum occurred in V sed when the surface tension of the suspending liquid was equal to that of the particles, i.e., when γLV = γSV Maxima occurred in the polar and minima in the nonpoiar and slightly polar liquid mixtures The results are discussed in terms of van der Waals interactions and mechanisms of particle aggregation.