Fine Particle Suspensions in Organic Liquids

Abstract

The sedimentation volumes of glass spheres, 5 to 15 microns in diameter, were determined in water and in a series of organic liquids. The sedimentation volumes in the organic liquids are identical with that in water or approach this volume as a minimum, as the system is dried more and more intensively. Flocculation of the particles causes the increase from the minimum value. The presence of water dissolved in the liquid and adsorbed on the particles produces this flocculation. The interfacial tension of the organic liquid against water is indicative of the tendency towards flocculation and the difficulty with which the minimum value may be attained. In some cases the sedimentation volume is proportional to the water content of the organic liquid. and in others the liquid must be nearly saturated before flocculation will take place.HE phenomena of setiiment'ation and agglomeration are of vital importance in many manufacturing processes, particularly to the paint and printing ink industries. Agglomeration of pigment particles affects settling and flonproperties of the paint. as well as such factors as gloss, permeability, and durability of the film. For example, the control of flocculation of dispersion is of utmost importance in the formulation of coating compositions. A high degree of dispersion of pigment particles gives improved flon-and gloss which are desirable in certain enamels. Flocculation of pigment particles which induces false bodying or reduced flow in paints is desirable in flat wall and met,al protective T compositions to permit uniform and complete coverage of the surfaces with one coat. A high degree of dispersion results in a hard cake formation of the pigments on settling, which is difficult to redisperse. On the other hand, flocculated pigments settle to a soft cake which is easily redispersed. It is evident, therefore, that a compromise between the two extremes of flocculation and dispersion must be made in pract,ice to formulate usable compositions.A suspension such as a paint is a complex syst'em consisting of a number of solid and liquid phases, and it is almost impossible to determine the effect of a single substance in the mixture. On the other hand, the behavior of glass spheres

Effect of Agglomerate Size Distribution on Loose Packing Fraction

“…18 Experimental values in this range have been observed when glass beads are sedimented in a nonpolar liquid. 19 Jullien et al modeled different degrees of adhesion and, as expected, found that the stronger the adhesion, the lower the packing fraction (Table II). 20 These simple approximations consider only the extremes of agglomerate behavior: either no bonding at all (dense packing) or strong bonding (very loose packing).…”

Capillary suspensions: Particle networks formed through the capillary force

“…The creation of the network, formed by adding a preferen-tially wetting liquid to a suspension, has been investigated previously in higher volume fraction suspensions. Early work on sedimentation determined that the addition of a secondary fluid (usually water to an organic solvent) caused the particles to flocculate and significantly increased the sedimentation volume [9]. Later, the rheological properties of the suspensions were measured where it was observed that the admixture creates a strong gel and that the yield stress greatly increases [10].…”

Structure of plastically compacting granular packings

“…The structure of mono-disperse granular media is known to be very sensitive to the shape of the grains [1], grain interactions such as cohesion [2,3], and assembling procedure [4]. Packing fractions as low as c = 0.125 have been found experimentally in 3D-systems with high grain-grain attraction [5], whereas dense systems of spherical grains can be packed to c > 0.65 [6] by a carefully selected tapping procedure.…”