The phase structure and phase behavior of polymer blends undergoing simple shear flow

Date of Completion

January 1995

Keywords

Chemistry, Polymer|Engineering, Chemical|Plastics Technology

Degree

Ph.D.

Abstract

The effect of simple shear flow on the phase structure and phase behavior of polymer blends was studied using a custom-built rheo-optical instrument which consisted of a commercial rheometer and a two-dimensional light scattering device. The scattered light intensity was detected using a high resolution two-dimensional charge coupled device (CCD) detector. This instrument allowed simultaneous rheological and light scattering studies to be performed.^ When simple shear flow was applied to a phase-separated polymer blend, a bright-streak scattering pattern was observed as for many other polymer mixtures reported in the literature. Further studies showed that the bright streak pattern developed from H-shaped and dark-streak patterns. Comparison of light scattering patterns with micrographs of a sheared sample revealed that all scattering patterns were parts of a distorted spinodal ring scattering pattern.^ The rheo-optical experiments showed that the spinodal-type bicontinuous structure was stretched in the flow direction, and a spinodal ring in the light scattering pattern was correspondingly shrunk in the flow direction. The characteristic dimensions of the phase structure of a flowing polymer blend were calculated from the distorted spinodal scattering ring.^ The phase separation kinetics of a flowing polymer blend was also studied. Anisotropic phase separation was observed. H-shaped and dark-streak scattering patterns developed during the phase separation process. The domain growth was studied from the development of scattering patterns.^ Two polymer blend systems were studied in this research: polystyrene/poly-(vinyl methyl ether) and polybutadiene/polyisoprene. ^

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