ITLApplied  Computational Mathematics Division
ACMD Seminar Series
Attractive Image NIST

Microstructure Modeling of Polymer Blends in Complex Flows

Fredrick R. Phelan Jr.
Multiphase Material Group, Polymer Division, NIST

Tuesday, December 18, 2001 15:00-16:00,
Room 145, NIST North (820)
Tuesday, December 18, 2001 13:00-14:00,
Room 4511

Abstract: Polymer blends are mixtures of two or more polymers that are usually processed in a phase-separated state in which droplets are suspended in a matrix phase. The fluid mechanical deformation experienced by the mixture during the processing causes the drops to deform, breakup and/or coalesce, which alters the local size, shape and orientation of the microstructure. Since the structural properties of the blend are in large part determined by the structure of the droplet-phase, there is great incentive to modle the evolution of teh blend morphology during processing. Modeling of polymer blends in complex flows such as injection molding is highly complicated by the fact that that the non-homogeneous deformation inherent to such flows leads to large spatial gradients in microstructure. Since drop densities may be as high as 1.E11 drops per cubic centimeter, modeling of such flows using rigorous multi-phase methods is untenable, as no single unit cell structure can be used to represent the entire medium. For this reason, we are investigating a multi-scale modeling approach for such flows. Volume averaged methods which compute the average microstructure within a meso-volume that is larger than the length scale of the mixture, but much smaller than overall volume are used to predict overall average flow characteristics. Rigorous two-phase simulations using diffuse interface methods are being used to model the details of flow at the drop level. Combining these two approaches, we hope to satisfy the need for both gross information such as pressure drop important to a process engineer designing tooling, and detailing information on microstructure important to materials engineer interested in properties.
Contact: A. J. Kearsley

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