Rheological properties of multiphase polymer systems

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The overall objective of this project is to develop novel rheological methods and models to characterize and predict the performances of polymer multiphase systems and optimize their properties in relation to processing. This innovative program should generate new and highly pertinent data, as well as new ideas for the modeling of these complex systems. Well characterized polymer blends (such as olefin blends of polypropylene (PP) and metallocene catalyzed ethylene copolymers (EC)) will be used to investigate the effect of imposed strain on the morphological changes as functions of the volume fraction of the dispersed phase and the elasticity of the polymer components. The role of added nanoparticles to modify the properties of the components and stabilize the morphology of the blends will be examined. The experimental data will be compared to the predictions of the rare models proposed in the recent literature to predict morphological changes in immiscible blends. These models will be generalized to account for the elasticity of the polymer components. The understanding of the rheological properties of filled polymers remains very poor, especially for suspensions of nano and interactive particles. We will examine the non-linear viscoelastic properties of model polymer suspensions consisting of multiwalled carbon nanotubes (MWCNTs) in a Newtonian epoxy and Boger fluids to mimic viscoelastic effects. Untreated and treated WMCNTs will be mixed to an epoxy or Boger fluids using a 3-roll mixer. We will establish the rheological behavior of these model suspensions as functions of concentration, surface treatment of the MWCNTs, elasticity of the matrix and pre-shearing (deformation history), using a unique 2D rheometric technique developed to probe the internal structure, anisotropy and orientation of nanoparticles under flow. The data will be used to assess and generalize existing structural- and Jeffery-type models.