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54 Cards in this Set
- Front
- Back
- 3rd side (hint)
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what is the modulated DSC?
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Superimpose a sine curve over heating rate.
Heat at an oscillated rate Sepeartes reversible and irreversale phenom. |
3 things.
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Does disorder prevent or encourage crystallinity?
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Disorder prevents crystallinity.
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Degredation causes viscosity to go______.
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Down
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Pros of the Melt Index?
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Simple.
Inexpensive. Common. |
3 Things.
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Cons of Cup and Bob system?
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Only really works in relatively low viscosity liquides.
Bob creates shear rate, rate changes. |
2 Things.
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What is Cone and Plate Rheometery?
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Most common way to determine viscosity of polymers.
Inexpensive. Precise f(gamma dot) |
3 Things.
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Traits of viscoelastic materials.
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Rate dependent behaviour in solids.
Rod climbing in liquids. Die swell in extrusion. Plastic "memory" Melt fracture. Creep/stress relaxation |
6 Things.
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For most plastics:
High strain rate = ____ viscosity. |
Lower viscosity.
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Engtanglement causes:
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Increase in Tg
Increase in Tm Increase in Stiffness Increase in Strength |
4 things.
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Behaviour at short time is equivalent to behaviour at ______.
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Low temperatures
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Behaviour over large spans of time is equivalent to behaviour at ______.
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Data taken over short spans of time.
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Factors affecting Tg:
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Molecular Weight
Secondary Bonds Pendant Groups Chain Stiffness Internal Mobility Free Volume |
6 Things.
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Applications of DSC:
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Classification/Identification
Heat capacity as a function of time. Find Tg, Tm. Level of cure of thermosets See if two polymers are mutually soluble Degredation Temp Degree Crxn. Purity Reaction Kinetics (autoclave time). |
9 Things.
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Three kinds of thermoanalysis:
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Differential Scanning Calorimetry
Thermal Gravimetric Analysis Thermomechanical Analysis |
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DSC stands for:
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Differential Scanning Calorimetery
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TGA Applications
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Find degredation temp.
Combined with mass spectrometry you can find whats coming off (chemistry) Fiber content Water/moisture content Solvent content Filler content |
6 Things
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What is Concentric Cylinder Rheometery?
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The "Bob" is super close to the cup
Creates a near perfect shear Very precise Low viscosity material only |
4 Things.
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Three methods of viscoelastic characterization.
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Creep
Stress Relaxation DMA |
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What does DMA stand for?
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Dynamic Mechanical Analysis
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All rheopectics are____.
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Dilatant
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Creep
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Stress is constant and strain is recorded as a function of time.
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E'
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Storage Modulus
Solid like behaviour Recoverable energy In phase |
4 things.
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IE*I
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Magnitude of complex modulus
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Two ways to meausre the Molecular Weight
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Gel permeation
Size exclusion chromatography |
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Stress Relaxation
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Strain is held constant and stress is recorded as a function of time.
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What is an engineering plastic?
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A polymeric material that has mechanical, thermal or chemical properties that make it suitable for use in engineering applications
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Viscosity Units
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1 Poise = 1 gm/cm*sec
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Lower melt index means ____ viscosity.
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Higher
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How does a Cup and Bob Viscometer work?
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The bob is rotated and the torque to keep it rotating is measured.
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Thermogravimetric Analysis measures what?
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How things degrade.
X-axis: temp Y-axis: % weight loss |
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E"
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Loss modulus
Liquid like behaviour Dissipates energy Out of phase component |
4 Things.
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Covalent bonds are _____.
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Backbones
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Thixotropic Fluid
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As you stir it becomes easier. Breaking up a structure as you stir.
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Ionic bonds are ______.
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Between chains.
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A polar functional group causes:
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An increase in:
Tg Tm Stiffness Strength |
4 things.
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Rheopectic Fluids
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As you stir it becomes harder. Structures are formed.
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Rheology
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Study of fluid flow.
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Three regions of the viscosity shear rate curve.
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1. Lower Newtonian: Unaligned
2. Pseudoplastic: Alignment increaes with increasing strain rate. 3. Upper New. Fully aligned (oreinted in direction of flow). |
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Viscosity is strongly _____ dependent.
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Temperature
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Two kinds of DSCs:
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Power compensated
Heat Flux |
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Pros of the Cup and Bob
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Inexpensive
Simple More accurate then others Gives viscosity |
4 Things.
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Newtonian Materials
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Materials for which viscosity is independent of shear stress/strain rates
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Applications of TMA
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Measures softening point
3 Pt. Bend/penetration tests for films. Finds Tg. Measures CTE |
4 Things.
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Thermomechanical Analysis Axis Labels
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x-Axis: Temp
Y-Axis: Position |
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Melt Index Units
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g/10 min.
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In gel permeation chromatography does high or low molecular weight come out first?
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High
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Torque Rheometry is used to
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Measure viscosity
Simulates processing Does not give a quantitative viscosity. |
3 Things.
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All thixotropics are ______.
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Pseudoplastics
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What is the DSC?
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Plots the difference in heat required to maintain constant heating rate.
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Cons of the Melt Flow Index.
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Not a true viscosity.
No shear rate Can not compare across a wide variety of materials. |
3 Things.
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S*
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Complex compliance
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What is the DMA?
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The sample is placed under a sinusoidal stress and the strain is recorded as a function of time.
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What is solution viscosity?
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Viscosity of a solution of polymer in a solvent.
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Capillary Rheometery
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Similiar to melt indexer but a controllable shear rate.
Can calculate the true viscosity as a function of shear rate. |
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