2004 training seminars dsc 5 mdsc® what it’s all about & how to get better results
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2004 Training SeminarsDSC
5
MDSC®
What it’s all about & how to get better results
What Does MDSC® Measure? • MDSC separates the Total heat flow of DSC into two
parts based on the heat flow that does and does not respond to a changing heating rate
• MDSC applies a changing heating rate on top of a linear heating rate in order measure the heat flow that responds to the changing heating rate
• In general, only heat capacity and melting respond to the changing heating rate.
• The Reversing and Nonreversing signals of MDSC should never be interpreted as the measurement of reversible and nonreversible properties
Modulated DSC® Theory
• MDSC® uses two simultaneous heating rates– Average Heating Rate
• This gives Total Heat Flow data which is equivalent to standard DSC @ same average heating rate
– Modulated Heating Rate• Purpose is to obtain heat capacity information at the
same time as heat flow
Note that temperature is not decreasing during Modulation i.e. no cooling
Modulate +/- 0.42 °C every 40 secondsRamp 4.00 °C/min to 290.00 °C
52
54
56
58
60
62
Mo
du
late
d T
em
pe
ratu
re (
°C)
52
54
56
58
60
62
Te
mp
era
ture
(°C
)
13.0 13.5 14.0 14.5 15.0
Time (min)
Average & Modulated Temperature
Modulated Temperature
Average Temperature
(Heat-Iso)
Note that temperature is not decreasing during Modulation i.e. no cooling
Modulate +/- 0.42 °C every 40 secondsRamp 4.00 °C/min to 290.00 °C
52
54
56
58
60
62
Modula
ted T
em
pera
ture
(°C
)
52
54
56
58
60
62
Tem
pera
ture
(°C
)
13.0 13.5 14.0 14.5 15.0
Time (min)
Average & Modulated Temperature
54.5
55.0
55.5
56.0
56.5
57.0
Mo
du
late
d T
em
pe
ratu
re (
°C)
54.5
55.0
55.5
56.0
56.5
57.0
Te
mp
era
ture
(°C
)
13.70 13.75 13.80 13.85 13.90 13.95 14.00 14.05
Time (min)
Modulated Temperature
Average Temperature
Amplitude
(Heat-Iso)
Average & Modulated Heating Rate
Note That Heating Rate isNever Negative (no cooling)
AverageHeating Rate
ModulatedHeating Rate
0
2
4
6
8
10
De
riv.
Mo
du
late
d T
em
pe
ratu
re (
°C/m
in)
0
2
4
6
8
10
De
riv.
Te
mp
era
ture
(°C
/min
)
13.0 13.5 14.0 14.5 15.0
Time (min)
Period
MDSC® Raw Signals
Modulated Heat Flow(Response)
Modulated Heating Rate (Stimulus)
MDSC Raw Data Signals for 13.54mg Quenched PET;+/-0.48;60sec;3°C/minNote that all transitions are visible in MHF signal
Glass Transition
Cold Crystallization
Melting
Crystal Perfection
0
4
8
12
16
20
24
Deri
v. M
odu
late
d T
em
pe
ratu
re (
°C/m
in)
-12
-8
-4
0
Mo
du
late
d H
ea
t F
low
(m
W)
0 50 100 150 200 250 300
Temperature (°C)Exo Up
Modulated DSC® Theory
• MDSC® Heat Flow & Signals
t)(T, dt
dT Cp
dt
dHf
Total = Reversing + Nonreversing
Modulated DSC® Theory• MDSC® Data Signals
t)(T, dt
dT Cp
dt
dHf
Total = Reversing + Nonreversing
Reversing Transitions
•Heat Capacity•Glass Transition•Most Melting
Modulated DSC® Theory• MDSC® Data Signals
t)(T, dt
dT Cp
dt
dHf
Total = Reversing + Nonreversing
Nonreversing Transitions
•Enthalpic Recovery•Evaporation•Crystallization•Thermoset Cure•Protein Denaturation•Starch Gelatinization•Decomposition•Some Melting
MDSC® of Quench-Cooled PET
Nonreversing
Reversing
Total
-0.4
-0.2
0.0
No
nre
v H
ea
t F
low
(W
/g)
-0.4
-0.2
0.0
0.2
0.4
Re
v H
ea
t F
low
(W
/g)
-0.4
-0.2
0.0
0.2
He
at
Flo
w (
W/g
)
0 50 100 150 200 250 300
Temperature (°C)Exo Up
When & Why to Run MDSC®
• Always run a standard DSC @ 10°C/min first
• If you’re looking for a glass transition --– If the glass transition is detectable and can be routinely
analyzed, then you don’t need to use MDSC
– However, if the Tg is hard to detect, or has an enthalpic recovery, then run MDSC
When & Why to Run MDSC®
• If looking at melting and crystallization –– If the melting process looks normal (single
endothermic peak) and there is no apparent crystallization of the sample as it is heated, then there is no need to use MDSC
– However, if melt is not straightforward, or it is difficult to determine if crystallization is occurring as the sample is heated, use MDSC
When & Why to Run MDSC®
• If you want heat capacity (Cp) – run MDSC– To get Cp by normal DSC (Q1000 is an
exception due to Direct Cp)• Use High heating rates, >10°C/min
• Three experiments required– Baseline
– Reference (sapphire)
– Sample
The Natural Limitations of DSC
• The next several slides discuss some of the natural limitations of DSC & how they are solved by MDSC®. This is by no means a complete list, just some of the more significant limitations.
The Natural Limitations of DSC1. It is not possible to optimize both sensitivity and
resolution in a single DSC experiment.
• Sensitivity is increased by increasing weight or heating rate
• Although increased sample size or heating rate improves sensitivity, they decrease resolution by causing a larger temperature gradient within the sample
• MDSC® solves this problem because it has two heating rates: the average heating rate can be slow to improve resolution, while the modulated heating rate can be high to improve sensitivity
t)(T,dt
dT Cp
dt
dHf
Sensitivity & Resolution
PC-PEE Blend 16.13mg MDSC® .424/40/1
Natural Limitations of DSC (cont.)
2. Baseline curvature and drift limit the sensitivity of DSC for detecting weak transitions
• MDSC® eliminates baseline curvature and drift in the Heat Capacity and Reversing signals by using the ratio of two measured signals rather than the absolute heat flow signal as measured by DSC.
K x Rate Heating Mod Amplitude
FlowHeat Mod Amplitude Cp
Rate Heating Avg x Cp Reversing
Where’s the Tg?
Tablet Binder, 44%RH 3.08mg MDSC® 1/60/5 Vented pan
Here’s the Tg!
Natural Limitations of DSC (cont.)
3. Transitions are often difficult to interpret because DSC can only measure the Sum of Heat Flow within the Calorimeter
• MDSC® minimizes this problem by providing not only the Total Heat Flow signal but also the heat capacity and kinetic components of it
Complicated Example
Quenched Xenoy 14.79mg 10°C/min
MDSC® Aids Interpretation
Xenoy 13.44 mg MDSC .318602
Natural Limitations of DSC (cont.)
4. It is often difficult to accurately measure the crystallinity of polymers by DSC because the crystallinity increases as the sample is being heated in the DSC cell. – To measure the correct crystallinity requires
the ability to:• determine the true heat capacity (no transitions) baseline
• quantitatively measure how much crystallinity developed during the heating process
DSC of Amorphous PET/PC Mixture…Where is the PC Tg ?
120.00°C 170.00°C
30.74J/g
215.00°C270.00°C
42.95J/g
120.00°C 270.00°C
13.31J/g
Standard DSC @ 10°C/min57% PET; 43% PC
DSC Heat Flow AnalyzedTwo Different Ways
-16
-12
-8
-4
0
4
[ ––––– · ] H
eat F
low
(m
W)
-22
-18
-14
-10
-6
-2
Heat F
low
(m
W)
50 100 150 200 250
Temperature (°C)
Sample: Quenched PET and PCSize: 13.6000 mgMethod: DSC@10Comment: DSC@10; PET13.60/PC 10.40/Al film 0.96mg
DSCFile: C:...\Len\Crystallinity\qPET-PCdsc.001
Exo Up Universal V3.8A TA Instruments
MDSC® Shows Two Tgs in Polymer Mixture
Decrease in Heat CapacityDue to Cold Crystallization
Glass Transitionof Polycarbonate
True Onset of Melting
Cold Crystallization PeakSeen Only in Total Signal
Total Heat Flow
Reversing Heat Flow
-3.2
-3.0
-2.8
-2.6
-2.4
-2.2
-2.0
[ –
––
––
· ]
Re
v H
ea
t F
low
(m
W)
-3.2
-3.0
-2.8
-2.6
-2.4
-2.2
-2.0
He
at
Flo
w (
mW
)
50 100 150 200 250
Temperature (°C)
Sample: Quenched PET and PCSize: 13.6000 mgMethod: MDSC .318/40@3Comment: MDSC 0.318/40@3; PET13.60/PC 10.40/Al film 0.96mg
DSCFile: C:\TA\Data\Len\Crystallinity\qPET-PC.002
Exo Up Universal V3.8A TA Instruments
MDSC® .318/40/3
MDSC® Gives Correct Crystallinity of Zero
Optimization of MDSC® Conditions
• Proper selection of the three experimental parameters is important in order to maximize the quality of the results.– In general, temperature is controlled to either
provide or not provide cooling during the temperature modulation
– Cooling is desirable for heat capacity transitions– Cooling is undesirable for melting &
crystallization
Select Modulated Mode
Select signals to store
Select Test (Template)
MDSC® Heat-Cool Modulation
Heating Rate goes below 0°C/min
Heating & Cooling
MDSC® Heat-Iso Modulation
Heating Rate never goes below 0°C/min
No Cooling
MDSC® Heat-Iso Amplitudes
40 50 60 70 80 90 100
0.1 0.011 0.013 0.016 0.019 0.021 0.024 0.027
0.2 0.021 0.027 0.032 0.037 0.042 0.048 0.053
0.5 0.053 0.066 0.080 0.093 0.106 0.119 0.133
1.0 0.106 0.133 0.159 0.186 0.212 0.239 0.265
2.0 0.212 0.265 0.318 0.371 0.424 0.477 0.531
5.0 0.531 0.663 0.796 0.928 1.061 1.194 1.326
HHeeaattiinngg
RRaattee
Period (sec)
This table is additive, i.e. the heat only amplitude for a period of 40 sec & a heating rate of 2.5°C/min is the sum of the values for 2.0°C/min & 0.5°C/min
Amplitude (40s,2.5°C/min)=0.212+0.053=0.265°C
No Cooling
MDSC® Conditions for Q Series DSC
Glass Transitions (Tg)Glass Transitions (Tg)• For “standard Tg”:
Sample Size: 10 – 15 mg Amplitude*: 2X Table
Period: 40 seconds Heating Rate: 3°C/min
• If Tg is Hard to Detect Sample Size: 10 – 20 mg Amplitude*: 4X TablePeriod: 60 seconds Heating Rate: 2°C/min
• If Tg has Large Enthalpic Relaxation Sample Size: 5 – 10 mg Amplitude*: 1.5X TablePeriod: 40 seconds Heating Rate: 1°C/min
*Use a minimum of 0.5°C amplitude
MDSC® Conditions for Q Series DSC
Heat Capacity (Cp)Heat Capacity (Cp)
• Heating Rate; isothermal up to 5ºC/min
• Modulation Period– 100 seconds with crimped pans– 120 seconds with hermetic pans
• Modulation Amplitude; 1.5X Table Value with a minimum of 0.5ºC
• Sample Size; 10-15mg
MDSC® Conditions for Q Series DSC
Melting and crystallinity:Melting and crystallinity:• Sample Size; 10-15mg
• Period– 40 sec. with crimped pans
– 60 sec. With hermetic pans
• Heating Rate– Slow enough to get a minimum of 4-5 cycles at half-height
of the melting peaks
• Amplitude– Use “Heat-Iso” amplitude which provides no cooling
during temperature modulation (see Table)
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