Thermal Analysis of Thermosets Noah Menard Veritas Testing and Consulting, LLC Denton, TX.

Thermal Analysis of Thermosets

Noah MenardVeritas Testing and Consulting, LLC

Denton, TX

©Veritas Testing and Consulting. LLC 2

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


Differential Scanning Calorimetry (DSC)

• Looks at changes in a materials heat capacity. • Detects energy released or absorbed.

4 Feb 2015


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


So from the cure, we predict cure time

4 Feb 2015


Then on the reheat,

4 Feb 2015


Tracking Cures by Tg

4 Feb 2015


Now in real life

• The Tg can be hidden by residual curing or by stress relief

4 Feb 2015


MT-DSC – cleaning up the Tg and more

4 Feb 2015


TTT Diagrams

4 Feb 2015


Fast Scanning DSC

4 Feb 2015

Single run at 10 C/min


The high rates let us…

4 Feb 2015

See under the exothermMakes transitions more visible


Linking Tg to chemistry of cure

4 Feb 2015

IR Scan of Epoxy over 3 Hour Period

Epoxy at Specific Times


Thermogravimetric Analysis (TGA)

4 Feb 2015


TGA-IR or MS

4 Feb 2015

Best match: C3H8O2N2

To MS

A


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)


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


CTE

4 Feb 2015


TMA - Dilatometry

4 Feb 2015

Dilatometer

Al203

Sample

TMA Probe


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


DMA gives you modulus and viscosity in cure

4 Feb 2015


As well as Tg

4 Feb 2015


DMA – Strain, Frequency, other effects

4 Feb 2015


Immersion Testing

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Previous immersed & run in air

Previous Immersed & run in salt water

Failing Epoxy Marine Paint

Never wet sample in air


Humidity

4 Feb 2015


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

Thank you.

Thermal Analysis of Thermosets Noah Menard Veritas Testing and Consulting, LLC Denton, TX.

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