流变学PPT演示课件

RobynMcMillanOctober11,2002,Rheology,1,WhatisRheology?,Rheology:ScienceofDeformationandFlow-FromtheGreekWord“Rheos”(River)-ReferstobothLiquidsandSolids,2,Motivation,-optimizetheprocessofsynthesis,formulationandapplication?-achievegoodappearance(nosag,noorangepeel,)?-achievegooddefectresistance?,Wouldyouwishto,Allrheologyrelated!,3,EdgeCoverageandCorrosion,4,Cratering,5,TypesofResponses,Viscousdeformation,Applyforce,Materialflows,Irreversible,Elasticdeformation,Applyforce,Materialreturnstooriginalshape,Reversible,Visco,-elastic,Bothresponsesobserved,6,ShearDeformation,7,Definition:Viscosity()=ShearStress()/ShearRate()Units:CommonUnits:Poise(P,cP)SIUnits:Pascal.seconds(Pa.s,mPa.s)Conversion:1P=100cP=100mPas1cP=1mPa.sExamplesofViscosityValue:MaterialApproximateViscosity(cp)Air10-2Water1OliveOil10Honey104Asphalt1011Glass1015(molten);1040(solid)CommonCoatings1-108,Viscosity()-ResistancetoFlow,8,FlowBehaviors:Newtonianvs.ShearThinningvs.ShearThickening,NewtonianFluids:-Viscosityisindependentofload-Examples:water,mineraloils,solvents,ShearThinningFluids(Pseudoplastic):-Viscositydecreaseswithincreasingload-Examples:polymersolutions/melts,shampoo,glue,blood,ShearThickeningFluids:-Viscosityincreaseswithincreasingload-Examples:wetsand,highconcentrationofstarch,9,Example:ShearThinningofAutomotiveWaterborneBasecoat,10,11,ApplicationShearRateRange,12,FlowBehavior-Plastic(YieldPoint),ShearstressmustsurpasssomecriticalvaluebeforeflowoccursExample:toothpaste,ketchups,lipstick,butter,dispersionpaint,Toothpaste:thedailyovercomingofyieldstress,13,Example:YieldStressofAutomotiveWaterborneBasecoat,YieldStress,14,FlowBehavior-Thixotropy,Viscosityistime-dependent-Degradesduringloadedphase-IncreasesduringunloadedphasesExamples:ketchup,15,MeasurementofViscosity-Flow(Efflux)Cups,16,MeasurementofViscosity-SpindleViscometer,17,MeasurementofViscosity-Cone/PlateViscometer,18,19,SignificanceofViscositytoSagResistance,Thedrivingforceforsaggingisgravity.Underanidealcondition,thesaggingcanbequantifiedby,20,SillyPutty,21,PowderCoatings,22,ElectrocoatAdditiveStudy,23,CorrelationofEdgeCorrosionandMinimumViscosity,24,Microdielectrometry,25,HowDoWeControlRheology?,26,Summary,Rheologyhasasignificantinfluenceoncoatingsprocess,app