Brookfield DV3T - Page 87

Brookeld Engineering Labs., Inc. Page 87 Manual No. M13-167-A0415
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
o
,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
o
) = 325.8 dynes/cm
2