Thermal analysis technique used includes DSC and TGA. DSC measures the exothermic reaction and provides data for kinetic analysis. Because the samples are not very stable, dynamic experiment method is used for DSC. TGA is used to measure the thermal stability of resin systems. Kinetic analysis is done by Kissinger Method. Through calculation, pot life of the resin system at different temperatures (0-50°C) is reported based on 5% of degradation (or reaction).
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Kinetics Prediction of Pot Life
1. Prediction of Pot life of Resin System
Significance of the Project
The most important application of kinetics in thermal analysis is to
predict reaction behavior under conditions in which it is practically
impossible to make measurements, for example for very short or very
long reaction times.
Pot life is an important parameter that related to the thermal stability of
mixed resin system, which provides information for processing and
production of materials. Kinetics prediction is an efficient method to get
the information about stability of materials at use (ambient)
temperature.
Example of Application
Reaction injection molding: large component/part
Adhesives
2. Methods
Experiment
Differential Scanning Calorimetry (DSC)
Kinetic Analysis
Kissinger method
Applicable to reaction that can E
ln 2
const.
be described by the Arrhenius Tm RTm
equation and the general rate
law.. ln(1 )
t
E
Assumption: the extent of the A * EXP( )
RT0
reaction at the peak exotherm
is constant and independent
of heating rate.
3. Isothermal Kinetic Measurements
5 o
260 C
How about dynamic
exo
4 experiment?
5
-1
o
Heat Flow /W g
3 250 C
exo
4
-1
2
Heat Flow /W g
3
5
1
o
2 240 C
exo
4
0
-1
1
Heat Flow /W g
-25 0 25 50 75 100 125 3
Time /min 0
2
0 10 20 30 40
Time /min 1
The samples are not stable for isothermal 0
experiments. 0 20 40 60 80
Time /min
Maximum of heat evolution occurs at time: 0, it follows nth order kinetics.
The dynamic method should work.
4. Dynamic Kinetic Measurements
o
10 C/min
o
Pot Life of Anonymous
13 C/min
2 o
7 C/min
o
4 C/min
Resin System
-1
Heat Flow /W g
100
1
time to 5% (days)
10
0
150 200 250 300 350 400 B
o 1
Temp / C
DSC curves for sample B at A
different heating rate. 0 10 20 30 40 50
o
Temperature ( C)
Samples B is more thermally
stable.
Sample A has lower stability.
5. Summary
Kinetic analysis can be applied in kinetics prediction.
We can use the values A and E to easily obtain time to
any conversion at any temperature of interest.