Studies of dispersions of organic and inorganic pigments in non-aqueous media
The behaviour of pigment dispersions containing high solid concentrations has been studied when the dispersions settled in such a manner that the classical Stokes' Law was inoperative. The sedimentation of the solid particles in such suspensions occurs with the movement of an interface, and this is termed "hindered settling" when above the interface is the clear supernatant liquid and below the interface is the suspended solid. The properties of the suspensions were judged in terms of the interface's behaviour as a function of time. The observation of the interface's behaviour as a function of time, was used to determine the effect of adsorbed alkyd resin (a polyester) from xylene onto the surface of iron oxide, titanium dioxide and alpha copper phthalocyanine had on hindered settling parameters. The measurement of the mass of polymer absorbed was undertaken by infrared spectroscopy and a radio-active tracer method. The work was concerned with the inorganic and organic pigments in the same bulk solution and provided information about each pigment in the same solution. The hindered settling experiments took place at specific points on each pigment's alkyd resin adsorption isotherm to provide an understanding of parameters involved in sedimentation equations in chemical and physical terms.