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34 Cards in this Set
- Front
- Back
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What is Kinematic Viscosity
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USP term
KV= absolute viscosity/density |
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Units for Viscosity
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Stokes (s) or centistokes (cs)
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Example in pharmacy includes
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flocculated particles in a concentrated suspension
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Known as Binghman Bodies
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Simple Plastic Flow
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shows yield value, f, which is measured in dynes cm^-2
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Simple Plastic Flow
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Why is the beginning of this graph curvilinear and then later become Newtonian?
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Due to contacts between adjacent particles in suspension must be broken down (Van der Waals forces) before suspension can flow easily
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It's slope G/F (rate of shear / shearing stress) represents fluidity.
What does it's reciprocal slope represent? |
Newtonian flow; viscosity
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It's slope G/F (rate of shear / shearing stress) represents mobility.
It's reciprocal slope represents |
Simple Plastic flow
Plastic Viscosity |
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It's G/F graph does not start at the origin.
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Simple Plastic Flow
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At stresses, below yield value material acts as an ______________ material.
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Elastic
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Natural and synthetic gums, liquid dispersions of tragacanth, Na alginate Na carboxymethyl cellulose (CMC)
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Simple Pseudoplastic Flow
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No part of rheogram is linear
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Simple Psuedoplastic Flow
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Viscosity ______ with increasing rates of shear in simple pseudoplastic flow.
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DECREASES
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can only calculate _______ viscosity in simple pseudoplastic flow
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apparent viscosity
it is the slope of tangent at a specific point |
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Certain suspensions with high percentage of dispersed solids exhibit _______ in viscosity with increasing rates of shear
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Dilatant Flow
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System increases in volume when sheared
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Dilatant flow
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Explain why the Dilatant Flow system results in a higher volume
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Molecules not sufficiently wetted, insufficient vehicle
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Shear thinning
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Pseudoplastic
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Shear thickening
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Dilatant
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N>1, flow is
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pseduoplastic
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Viscosity of a gas ______ with higher temperature.
and of a liquid? |
gas: increases
liquid: decreases |
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Which equation relates temperature and viscosity
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Arrhenius Eq
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This phenemonon states that the down curve is displaced with regard to up curve. Material has LOWER viscosity on down than up
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Thixotropy
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Shows material hs lower consistency at any one rate of shear on the down curve than had on the up curve
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thixotropy
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Resembles a gel and with application of shear, a gel to solution transformation occurs and structure breaks down
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thixotropy
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How to quantify thixotropy?
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Measure hysteresis area
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What kind of gel shows "bulge' in up curve (Hysteresis Loop)?
Why does this happen? |
Bentonite gels; swelling of crystalline plates of bentonite within the 3D structure
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Spur values in hysteresis loops occur with _______ structured systems such as procaine penicillin gel formulation for IM injection
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highly
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The high yield of SPUR VALUE represents
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a sharp point of structural breakdown at low shear rates
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In what substance is Antithixotropy observed?
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Magnesia Magma
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Which shear rate viscometer is only suitable for Newtoniain systems?
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Single (ie. Hoeppler)
Use variable shear rate viscometer for for both |
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known as Ostwald Cannon-Fenske Viscometer
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Capillary viscometer.
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Needs reference material for which absolute visosity is known
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Otswald
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Strain is expressed by
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Compliance J
J is strain per unit stress |
