王十庆-高分子流变学 Nonlinear rheology at USTC-new

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1、Polymerrheology:fromlineartononlinearShi-QingWangDepartmentofPolymerScienceUniversityofAkronDecember5,2008,USTC1LubricantFilmblowingGelYogurtRheology:Thestudyofflowanddeformation2Exploringtheexperimentalandtheoreticalfoundationsofpolymerrheology:lookingatthetipoficebergShi-QingWa

2、ngDepartmentofPolymerScience,UniversityofAkronOver20moviescanbeviewedonhttp://www3.uakron.edu/rheology/dielipIcebergPolybutadiene,PIP,SBR,PE,PP345Whatispolymerrheology?•RheologyastoolExperimentalmethodsMolecularlevelmodeling•Rheologyastechnology(nonlinearaspects)Morereliableexper

3、imentalmethodsBetterprocessingbehavior•Rheologyasscience(nonlinearaspects)PhenomenologicalfoundationwallslipyieldingAppliedmathematics:continuumfluidmechanicalcomputationispolymeracontinuum?67NONLINEARRHEOLOGYOFPOLYMERICLIQUIDSFromElasticYielding,InhomogeneousFlowtoMeltFractureSh

4、i-QingWang(2010)I.Phenomenologicallinearviscoelasticity(LVE)II.MolecularcharacterizationinLVEregimeIII.ExperimentalapproachesIV.PhenomenologicalaccountsofnonlinearbehaviorV.HomogeneousdeformationandflowVI.Flowvisualization–particletrackingvelocimetryVII.Wallslip–firstcaseofinhomo

5、geneousshearVIII.CohesionofentanglementnetworkandyieldingIX.ShearbandinginplasticflowX.Yieldinpressure-drivenflowXI.ParallelphenomenainuniaxialextensionXII.Challengesinpolymerprocessing8XIII.Conclusions-NewobjectivesinpolymerrheologyShearF(tF(t))ExtensionF(t)F(t)9•Rheologyastool-

6、characterizationa)Linearvs.nonlinearpolymerrheologyb)Whatischainentanglement?10•Rheologyastool-characterizationExperimentalmethodsMolecularlevelmodelingInstrumentation•Rotationalrheometers•Extensionalrheometers•Manynon-commercialdevices(nonlinear)SlidingplatePiston–co-cylinderdes

7、ignSandwichedplateProtocols•Startupshear•Oscillatoryshear•Stepshear11Akeyconceptinrheologytimescale.•Startupshear–rateofshear:γ=V/HΔx=H=Vt11H100%:Δx=H1t=H/V=1/(V/H)1Whatistcomparedto?112•Oscillatoryshearγ=γsinωt0ΔXHγ=ΔX/2H0Τ=2π/ωWhatisTcomparedto?Polymerdynamicsrepresentedbyarela

8、xationtimeτ13γ=γsinωt0γXσHγ=X/2H00tσ=σsi