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54 Cards in this Set

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