Brookfield DV-I Prime Manual de usuario descargar pdf (Pagina 36)

Brookeld Engineering Laboratories, Inc. Page 36 Manual No. M/07-022-D0613

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 II-46, they learn that

their ointment has a higher yield stress,

€

, 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 (

€

) = 325.8 dynes/cm

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Brookfield DV-I Prime Manual de usuario Pagina 36