To Next Page

To Previous Page

Brookeld Engineering Labs., Inc. Page 67 Manual No. M13-167

Appendix C - Variables in Viscosity Measurements

Aswithanyinstrumentmeasurement,therearevariablesthatcanaffectaViscometermeasurement.

Thesevariablesmayberelatedtotheinstrument(Viscometer),orthetestuid.Variablesrelatedto

thetestuiddealwiththerheologicalpropertiesoftheuid,whileinstrumentvariableswouldinclude

theViscometerdesignandthespindlegeometrysystemutilized.

Rheological Properties

FluidshavedifferentrheologicalcharacteristicsthatcanbedescribedbyViscometermeasurements.

Wecanthenworkwiththeseuidstosuitourlaborprocessconditions.

Therearetwocategoriesofuids:

Newtonian - TheseuidshavethesameviscosityatdifferentShearRates(differentRPMs)

andarecalledNewtonianovertheShearRaterangetheyaremeasured.

Non-Newtonian - These uids have different viscosities at different shear rates (different

RPMs).Theyfallintotwogroups:

1) TimeIndependentnon-Newtonian

2) TimeDependentnon-Newtonian

Time Independent

Pseudoplastic - Apseudoplasticmaterialdisplaysadecreaseinviscositywithanincrease

inshearrate,andisalsoknownas“shearthinning”.IfyoutakeViscometer

readingsfromalowtoahighRPMandthenbacktothelowRPM,andthe

readingsfalluponthemselves,thematerialistimeindependentpseudoplastic

(shearthinning).

Time Dependent

Thixotropic - Athixotropicmaterialhasdecreasingviscosityunderconstantshearrate.

IfyousetaViscometerataconstantspeedrecordingcPvaluesovertime

andndthatthecPvaluesdecreasewithtime,thematerialisthixotropic.

 - IfyoutakeviscometerreadingsfromalowRPMtoahighRPMandthen

backtothelowRPM,andthereadingsarelowerforthedescendingstep,

thematerialistimedependant,thixotropic.

Brookeldpublication,“More Solutions to Sticky Problems”,includesamoredetaileddiscussionof

rheologicalpropertiesandnon-Newtonianbehavior.

Brookfield DV2T User Manual

Questions and Answers: