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Ceutics(2) Exam 1 - Rheology 3

Terms in this set (22)

Rheopexy is to ______ flow what thixotropy is to ______ and _____ flow
Dilatant
Plastic and Pseudoplastic
______ is a phenomenon in which a solid forms a gel more readily when sheared than when allowed to form a gel while the material is kept at rest
Rheopexy
_____ will not start unless activation energy is provided
Flow
Flow of pharmaceuticals cannot be characterized by viscosity only, because they have _______ property of solids as well
Elastic
_______ materials possess both viscous properties (of liquids) and elastic properties (of solids)
Viscoelasticity
Viscoelasticity measurements test rheologic ________ state
Ground
_______ measurements do not employ continuous shear to deform/destroy material structure
Viscoelasticity
Both Maxwell and Voigt elements measure _______ which is defined as strain per unit stress
Compliance J
Two type of viscoelasticity meters
Maxwell
Creep
Al of the following are pharmaceutical applications of ________
Modifications and improvement of non-Newtonian dermatologic and cosmetic vehicles
Analysis of sputum for the design of mucolytic agents
Measurement of shear in synovial fluids during the simulated movements of joints
Viscoelasticity
Ideal suspension will have ______ viscosity at negligible shear and _____ viscosity at higher shear
High
Low
______ substances with thixotropic properties achieve the goal of an ideal suspension
Pseudoplastic
The _____ material should not interfere (by adsorbing) with the availability of drug
Structural
_______ entrap particles in a deflocculated manner to prevent settling and are pseudoplastic or plastic in nature
Structured Vehicles
Pharmaceutical emulsions are mostly ________
Non-Newtonian
At low PVR (phase volume ratio) the system is _____
Newtonian
As the PVR increasers, the system attains what characteristics?
Pseudoplasticity and Plasticity
At PVR=0.74, phase inversion may occur with a sharp change in ______
n (eata)
Reduction in droplet size _____ viscosity of emulsion
Increases
The wider the size distribution of droplets ______ the viscosity
Lower
Viscosity of ______ phase has small impact on the flow properties of an emulsion
Continuous
_________ affects particle flocculation and interglobule attraction
Emulsifying Agent
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