王十庆-高分子流变学Introductiontopolymerrheology.doc

Introduction to Polymer RheologyShi-Qing WangDepartment of Polymer Science, University of Akron, Ohio 44325IntroductionThe missions of polymer rheologyphenomenological (Maxwell level), linear viscoelasticitya) characterization toolsstructural (molecular level), i.e., molecular weight, MWD, chain architecture (branching, functional moieties), thus heavily model dependent and theoretically intensive nonlinear aspectsb) a sub-field of polymer science fluid mechanics of polymers numerically intensive processing behaviori. Fluid dynamics/mechanics - study flow behavior of simple (Newtonian) fluids in complex geometries and complex flow conditions including turbulent flow and thermal convection.ii.Polymer rheology - explore flow behavior of polymeric (viscoelastic/non-Newtonian) fluids in simple geometries.iii.Fluid mechanics of polymers (relevant to processing) - investigate flow behavior of viscoelastic polymeric liquids in complex geometriesPART ARHEOLOGY AS CHARACTERIZATION METHODSI. Phenomenological linear viscoelasticity1. Mechanical deformationsa. Step strain b. Startup flowc. Small amplitude oscillatory shear (SAOS)2. Linear responsesa. Elastic Hookean solidsb. Viscous Newtonian liquidsc. Viscoelastic Maxellian responses3. Classical rubber elasticityIII. RheometryShear - A combination of extension and rotation1.Flow due to boundary displacementa.Linear displacementi. Sliding parallel plates ii. Co-cylinder pistonb. Rotational motioni. Parallel disksii. Cone-plateiii. Couette 2. Flow driven by pressurea. Capillary die b. Channel slit Extension1. Instron type stretcher2. Extender at fixed lengthPART B RHEOLOGY AS SCIENCEIV. Phenomenological accounts 1. Shear thinning2. Strain softening3. Wave distortion4. Extrudate swell5. Melt fractureV. Homogeneous flow1.Basic principle for rheometry2. Equivalence between controlled-rate and controlled-stress shear3. Flow homogeneity in diffusion limit terminal flow4. Non-entangled and weakly entangled polymersVI. Wall slip a case of inhomogeneous shear1. Spurt and flow oscillatory2. Navier-de Gennes extrapolation length b3. Stick-slip transitiona. capillary flowb. drag flow4. Theoretical accountsa. limit of small surface coverage - Brochard-de Gennes theoryb. saturated adsorption disentanglement pictureVII. Flow inhomogeneity strongly entangled polymers1. New considerations based on viscoelasticity concept2. Cohesion of entanglement network3. Elastic yielding4. Scaling characteristics of stress overshoot a moving target 5. Deformation-induced structural disintegration yield phenomenon6. Case studiesi. Startup shearii. Large amplitude oscillatory shear7. Uniaxial extensional flowVIII. Experimental Approaches1. Conventional rheometrya. Finite size effectsi. free surface at meniscus in rotational rheometryii. entry flow in capillary rheometryb. Improved setupsi. Cone-partitioned plate for shearii. Counter-rotation drums for extension2. Rheo-optical (in situ) methodsa. Flow birefringe