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Thermosets and Thermal Analysis
4 Feb 2015
Technique Uncured Samples Cured Samples Uncommon Methodology
DSC Time and how energetic a cure.Time/temperature/ degree of cure relationships
Glass transition temperatureResidual cure
MT-DSCFast Scan DSCUV-DSC
TGA Weight loss on curing Decomposition temperaturesFiller content
Derivative controlled methods
Hyphenated TGA What’s evolved on curing Unreacted components. TG-IR, MS, GCMS, etc
TMA Contraction on curing CTE on cured materials Dilatometry
DMA Time to gelationRe-vitrification Temperature
Glass transition temperatureBeta transition
Strain and frequency scansImmersion/humidity tests
©Veritas Testing and Consulting. LLC 3
Differential Scanning Calorimetry (DSC)
• Looks at changes in a materials heat capacity. • Detects energy released or absorbed.
4 Feb 2015
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How much did it cure?
4 Feb 2015
Blue Curve = -126 J/gGreen Curve = -191 J/g
Degree of Cure (DC) = (1 – fraction uncured)100
Uncured Fraction =
(Full Cure – unknown) Full Cure
= (-191 - - 126)/-191= .34
DC = (1- .34) = 66%
ΔΗ = -126
ΔΗ = -191
©Veritas Testing and Consulting. LLC 8
Now in real life
• The Tg can be hidden by residual curing or by stress relief
4 Feb 2015
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The high rates let us…
4 Feb 2015
See under the exothermMakes transitions more visible
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Linking Tg to chemistry of cure
4 Feb 2015
IR Scan of Epoxy over 3 Hour Period
Epoxy at Specific Times
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Analysis by TG-IR in Action
4 Feb 2015
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
Ab
s 0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
Ab
s 1000 1500 2000 2500 3000 3500 4000
TFS
Carbon dioxide
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
Ab
sorba
nce
500 1000 1500 2000 2500 3000 3500 4000
Wavenumbers (cm-1)
©Veritas Testing and Consulting. LLC 17
Thermomechanical Analysis (TMA)
• The Tg is a region (Mark)• Tg from the three techniques do not match
– DSC<TMA<DMA
4 Feb 2015
Temperature /K
Exp
ansi
on
/(m
m)
Tg= 105.3
2.945e-5/K
2.195e-2/K
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TMA - Dilatometry
4 Feb 2015
Dilatometer
Al203
Sample
TMA Probe
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Dynamic Mechanical Analysis
• The dirty secret of DMA – most of them are used for Tg measurement
4 Feb 2015
tan
d
Temperature
1.0
0.5
0.0
0 hours
1 hour
150 200175
Hea
t fl
ow (
mW
)
21.8
23.8
tan d
Heat flow20 C/min
2 - 8 hours
500 C/min
©Veritas Testing and Consulting. LLC 24
Immersion Testing
4 Feb 2015
Previous immersed & run in air
Previous Immersed & run in salt water
Failing Epoxy Marine Paint
Never wet sample in air
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Other things doable in a DMA
Film Stress Strain
0.00E+00
1.00E+07
2.00E+07
3.00E+07
4.00E+07
5.00E+07
6.00E+07
7.00E+07
8.00E+07
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Strain (%)
Str
es
s (
Pa
)
X Axis
Y Axis
4 Feb 2015
• Stress-strain Curves• Creep-Recovery Tests• Stress-Relaxation• Frequency Scans• Time Temperature
Superposition• Mastercurves• Kinetics (Roller Model)• UV curing
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