Visualization of polymer blending and drop breakup

Polymer blends are attractive because they provide improved performance and enhanced properties over homopolymers. The final blend properties depend on morphology, and the morphology, in turn, is controlled by the blending process. Therefore, it is vital to understand how one polymer drop incorporates into a second kind of polymer and how the final particle distribution is obtained. Accordingly, this thesis focuses on visualization of one polymer drop melting, deforming and breaking up inside another polymer melt under shear flow.; Two kinds of visualization geometries were used: parallel plate and Couette. It was found that drop breakup in polymer systems can occur at all viscosity ratios even when the viscosity ratio is greater than 3.5. This has been proven to be impossible for Newtonian systems in simple shear flows. At least four kinds of distinct drop breakup mechanisms were observed in uncompatibilized polymer systems subject to simple shear: "erosion", "parallel breakup", "vorticity alignment and breakup" and "tip streaming". The first three mechanisms are unique to viscoelastic systems.; In Newtonian systems, drop breakup can be well described with Capillary number and viscosity ratio. For polymer systems, besides interfacial tension, viscosity ratio and shear rate, there are other important governing factors, such as shear history, normal stresses and relaxation time. The stress ratio and the drop Deborah number are two important dimensionless parameters that were used to describe drop breakup in polymer systems.; In compatibilized systems, the copolymer may promote drop breakup if the copolymer is saturated and distributes homogeneously across the interface; conversely, it may stabilize the drop if there is a concentration gradient and insufficient coverage at the interface in which case a tiny tip develops. Fast in-situ reaction assists drop breakup by stretching the drop into a thin sheet, whereas slow reaction delays drop breakup since newly formed copolymer product accumulates at the drop tips.; Finally, this thesis shows that deformation, melting and mixing mechanisms affect the morphology of compatibilized polymers blends. By controlling melting and mixing sequences, it is possible to control the final mean particle size and particle size distribution and thereby influence final properties.