Brookfield DV3T Rheometer Manuale Utente Scaricare il pdf (Pagina 90)

Brookeld Engineering Labs., Inc. Page 90 Manual No. M13-2100

AnExampleoftheCassonModelatWork

Beforereleasinganewoverthecountergel,a

pharmaceuticalcompanyneedstolearnhow

itwillbehavewhichitisbeingusedbythe

endconsumer.Theyperformafullviscosity

proleandapplytheCassonmodel.Fromthe

results,showninFigureVII-4,theylearnthat

theirointmenthasahigheryieldstress,τ

,and

lowerplasticviscosity,

h,thantheyoriginally

intended.Asaresultitisdifcultordispensefromitscontainer(duetothehighyieldstress)

anditdoesnotholditshapeverywell(duetothelowplasticviscosity),makingitdifcultto

applyasmallamounttotheaffectedareaoftheskin.Basedonthisdata,formulatorsareable

tomodifytheingredientsaccordingly.Onceaformulationisestablished,multi-pointtestsand

theCassonmodelareperformedasaQCtooltocheckbatchesbeforeandafterprocessing.

Pharmaceutical Gel

Plastic Viscosity (

h) = 329.8 cP

Yield Stress (τ

) = 325.8 dynes/cm

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Brookfield DV3T Rheometer Manuale Utente Pagina 90