Lamellar Microstructure via Polymer Melt Processing

摘要

Lamellar microstructures can provide excellent control of polymer permeability. For example, they can stop toxic organic vapors yet transmit water vapor, be produced economically, and provide increased resistance to mechanical impact. However, the methods used to create and stabilize lamellar blends are not well understood. The key to creating lamella during melt blending is understanding the transient deformation of viscous and viscoelastic drops. In this research, the authors sheared polymer drops to very large deformation and measured their transient dimensions. Using fluorescent labeling and confocal microscopy, they showed how diblock co-polymers adsorbed on drop surfaces are convected to drop edges where they can lower interfacial tension. Drops deformed further with than without block co-polymer and generated more lamellar microstructures. At high stress, slip was observed between immiscible polymer surfaces. Slip appears to be caused by reduced chain entanglement, which generates a thin low-viscosity region in the interface. Block co-polymer can eliminate this slip. Drop deformation breakup and coalescence were modeled with new adaptive 3D finite element methods. Calculations compared well to experiments and gave insight into observation of drop widening for low- viscosity drops. The effect of block co-polymer on interfacial tension was included in the model and predicted the role of block co-polymer in suppressing coalescence. The report includes a list of 6 journal articles, 5 conference paper preprints, 10 meeting papers, 2 manuscripts, and 9 reports submitted to ARO. Two abstracts are appended: 'Drop Dynamics in Polymer Processing Flows,' by Russell W. Hooper, and 'Multilayer Coextrusion Reveals Interfacial Dynamics in Polymer Blending,' by Rui Zhao.