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Rheology    
Director: H. Henning Winter

Equipment located in the Rheological Facility measures the steady state and dynamic response of polymers undergoing shear. This includes a Rheometrics Mechanical Spectrometer, which provides complex modulus, relaxation time spectra, and transient stress response data. Viscosity measurements are provided by a Gottfert Rheograph 2001 capillary melt rheometer and a laboratory designed and built high pressure viscometer for supercritical fluids investigations. An AIC Linear Rheometer provides measurements of external flow properties and adhesive properties of polymers.

Rheo-optical responses are monitored by use of a laboratory constructed shear cell that mounts within a Zeiss optical microscope. This arrangement permits birefringence measurements of polymeric solutions and conoscopy measurements of flowing, liquid crystalline polymers. Small angle light scattering measurements on polymeric fluids under shear are obtained through the use of a specialized, custom built instrument. Rheology is the study of the flow and deformation of materials. The complex rheology of many polymers not only constrains potential applications, but it also limits the way that these materials can be processed. The Rheology Laboratory clusters instruments that measure the mechanical and optical properties of various sorts of polymeric fluids (solutions, gels, melts) as stresses and/or strains are applied. Instruments to characterize these properties for solid polymers are located within the MRSEC Characterization Facility.

Several devices located in the Rheology Laboratory measure the steady state and dynamic mechanical response of polymeric fluids undergoing shear. These include a Rheometrics Mechanical Spectrometer (complex modulus, relaxation time spectrum, transient stress response), a Goettfert Rheograph 2001 capillary melt rheometer (viscosity), and a home-built, high pressure viscometer for supercritical fluid investigations. An AIC Linear Rheometer provides the laboratory with a capability to measure extensional flow properties and also to perform adhesion testing. Additional specialized instruments probe the rheology of low viscosity fluids such as oligomers and dilute solutions.

To monitor rheo-optical reponse, investigators in the laboratory have constructed a special shear cell that fits within a Zeiss optical microscope, an arrangement permitting flow birefringence measurements for polymer solutions and conoscopy for flowing liquid crystalline polymers. A second home-built optical instrument makes possible small angle light scattering investigations for various types of polymeric fluids under shear.