STATIC LIGHT-SCATTERING ON DENSE COLLOIDAL SYSTEMS - NEW INSTRUMENTATION AND EXPERIMENTAL RESULTS

Particle sizing of dense colloidal systems is a very practice-oriented problem. Using optical methods multiple scattering often makes the de termination of correct particle sizes impossible. We introduce a new s tatic light scattering instrument which allows the investigation of de nse colloidal systems. This instrument is a modification of a Fraunhof er setup featuring a flat sample cell, Fourier optics, and an array de tection. The thickness of the flat sample cell can be varied from abou t 10 mu m to 5 mm. The small sample thickness highly reduces multiple scattering and allows for the investigation of dense colloidal systems . In most cases multiple scattering can be avoided by reducing the sam ple thickness only. In addition, data with remaining multiple Mie scat tering can be inverted if the sample transmittance if above 0.3. The a ngular regime of the instrument is 1 degrees to 60 degrees, the minimu m measuring time is 1 s and the smallest amount of substance necessary is about 0.5 mt. We present our instrumentation, the evaluation techn ique, and the application to latex suspensions, fat emulsions, and mil k as typical colloidal systems. (C) 1998 Academic Press.