SMALL-ANGLE LIGHT-SCATTERING STUDY OF DROPLET BREAK-UP IN EMULSIONS AND POLYMER BLENDS

The potential of using small-angle light scattering (SALS) to probe mo rphological changes induced by flow in immiscible polymer blends is in vestigated. Well-defined flow histories are shown to result in SALS pa tterns that are characteristic for the morphology involved. The pertin ent structural change caused by either suddenly applying flow or drast ically increasing the shear rate is the stretching of inclusions into long filaments, which subsequently break up by Rayleigh instabilities. Scattering models are developed to calculate the SALS patterns result ing from a filament with a sinusoidally disturbed surface and from a s eries of aligned spheres. These models capture the main features of th e measured SALS patterns and are used to extract quantitative morpholo gical information of the system. This is demonstrated by comparing cal culated and measured results for droplet and filament size. In this ma nner an in situ, time-resolved technique becomes available to follow f low-induced structural changes such as those occurring during processi ng of blends. (C) 1998 Elsevier Science Ltd. All rights reserved.