A MELT RHEOMETER WITH INTEGRATED SMALL-ANGLE LIGHT-SCATTERING

A stress-controlled commercial rheometer has been equipped with small-angle light scattering (SALS) instrument working in a range of wave-vectors between 0.5 and 4.2 mum-1. By a specially designed optical system the scattered light is focused directly on the square chip of a CCD-detector with high dynamical range allowing quantitative two-dimensional (2D) intensity measurements of polarized and depolarized scattering. The rheo SALS system is suited for simultaneous fast measurements of 2D SALS and rheological material functions of polymer melts and liquid crystals. As a first application results on the influence of shear rate on the late stage of spinodal decomposition of a polybutadiene/polyisoprene blend are reported. A second application concerns a creep experiment in the liquid crystalline phase of a lyotropic non-ionic surfactant with simultaneous measurement of the time-dependent compliance and associated changes of the 2D intensity patterns of the polarized and depolarized scattering.