Table Of ContentDifferential Scanning Calorimetry
(DSC)
Basic Theory &
Applications Training
©2009 TA Instruments
Agenda
(cid:1) Understanding DSC
(cid:1) Experimental Design
(cid:1) Calibration
(cid:1) Optimization of DSC Conditions
(cid:1) Interpretation of Undesirable Events in DSC Data
(cid:1) Applications
DSC Training Course
1
2900 Series DSC’s
DSC 2010 DSC 2910 DSC 2920
DSC Training Course
First Generation Q Series™ DSCs
Q1000
Q100
Q10
DSC Training Course
2
Second Generation Q-Series™ DSCs
Q2000 Q200 AutoQ20
Q2000 is top-of-the-line, research grade with all options
Q200 is research grade and expandable
Q20 is a basic DSC – Available as an
Auto Q20 & also Q20P
DSC Training Course
Understanding DSC - Agenda
(cid:1) What does a DSC measure?
(cid:1) How does a DSC make that measurement?
(cid:1) How is a Tzero™ DSC different?
(cid:1) Tzero Results
(cid:1) Advanced Tzero
DSC Training Course
3
Agenda
(cid:1) What does a DSC measure?
(cid:1) How does a DSC make that measurement?
(cid:1) How is a Tzero™ DSC different?
(cid:1) Tzero Results
(cid:1) Advanced Tzero
DSC Training Course
What Does a DSC Measure?
A DSC measures the difference in heat flow rate (mW =
mJ/sec) between a sample and inert reference as a
function of time and temperature
DSC Training Course
4
Endothermic Heat Flow
0.1
(cid:1) Heat flows into the sample as a result of either
(cid:1) Heat capacity (heating)
0.0
(cid:1) Glass Transition (Tg)
(cid:1) Melting
-0.1 (cid:1) Evaporation
W/g) (cid:1) Other endothermic processes
Flow ( -0.2
Heat
-0.3
-0.4 Endothermic
0 25 50 75 100 125 150
Exo Up Temperature (°C)
DSC Training Course
Exothermic Heat Flow
Exothermic
0.1
W/g)
w (
Flo
Heat (cid:1) Heat flows out of the sample as a result of either
0.0
(cid:1) Heat capacity (cooling)
(cid:1) Crystallization
(cid:1) Curing
(cid:1) Oxidation
(cid:1) Other exothermic processes
-0.1
0 20 40 60 80 100 120 140 160
Exo Up Temperature (°C)
DSC Training Course
5
Temperature
(cid:1) What temperature is being measured and displayed
by the DSC?
Sensor Temp: used by most DSCs. It is measured at the
(cid:1)
sample platform with a thermocouple, thermopile or PRT.
Sample Platform
Chromel Area Detector
Reference Platform
Constantan Body Thin Wall Tube
Base Surface
Constantan Wire
Chromel Wire
Chromel Wire
DSC Training Course
Temperature
(cid:1) What temperature is being measured and displayed
by the DSC?
Pan Temp: calculated by TA Q1000/2000 based on pan
(cid:1)
material and shape
(cid:1) Uses weight of pan, resistance of pan, & thermoconductivity of
purge gas
What about sample temperature?
(cid:1)
(cid:1) The actual temperature of the sample is never measured by DSC
DSC Training Course
6
Temperature
(cid:1) What temperatures are not typically being displayed?
Program Temp: the set-point temperature is usually not
(cid:1)
recorded. It is used to control furnace temperature
Furnace Temp: usually not recorded. It creates the
(cid:1)
temperature environment of the sample and reference
DSC Training Course
Understanding DSC Signals
Heat Flow
(cid:1) Relative Heat Flow: measured by all DSCs except TA
Q1000/2000. The absolute value of the signal is not
relevant, only absolute changes are used.
(cid:1) Absolute Heat Flow: used by Q1000/2000. Dividing
the signal by the measured heating rate converts the
heat flow signal into a heat capacity signal
DSC Training Course
7
DSC Heat Flow
dH Cp = Sample Heat Capacity
= DSC heat flow signal
dt = Sample Specific Heat x Sample Weight
dH dT
= Cp + f (T, t)
dt dt
dT f(T,t) = Heat flow that is function of time
= Heating Rate
dt
at an absolute temperature (kinetic)
DSC Training Course
Agenda
(cid:1) What does a DSC measure?
(cid:1) How does a DSC make that measurement?
(cid:1) How is a Tzero™ DSC different?
(cid:1) Tzero Results
(cid:1) Advanced Tzero
DSC Training Course
8
How does a DSC Measure Heat Flow?
(cid:1) DSC comprises two nominally identical calorimeters in a
common enclosure that are assumed to be identical.
(cid:1) Advantages of a twin calorimeter:
Noise reduction by cancellation of common mode noise.
(cid:1)
Simplified heat flow rate measurement.
(cid:1)
Cancellation of calorimeter and pan heat capacities.
(cid:1)
Cancellation of heat leakages.
(cid:1)
DSC Training Course
Heat Flux DSC Cell Schematic
2900 Series DSC
Reference Pan
Sample Pan
Dynamic Sample Chamber
Lid
Gas Purge Inlet Thermoelectric Disc
(Constantan)
Chromel Chromel
Disc Disc
Heating
Block
Chromel Wire
Thermocouple
Alumel Wire Junction
DSC Training Course
9
Perfectly Symmetrical?
(cid:1) The heat flow rate of an empty perfectly symmetrical
twin calorimeter should be zero.
(cid:1) However, it almost never is because the DSC is rarely
symmetrical as assumed.
(cid:1) The asymmetry is the inevitable result of manufacturing
tolerances and is unavoidable.
For example, thermal resistance of the Tzero DSC cell is determined
by the wall thickness of the “top hat”which is .005”(0.13mm). To
achieve 1% thermal resistance imbalance would require
manufacturing tolerance of .00005”(.00127mm).
DSC Training Course
Conventional DSC Measurements
2900 Series
Heat Flow Heat Balance Equations
Measurement Model
T −T T −T
q = fs s q = fr r
qs qr s R r R
s r
Conventional DSC Heat
Ts Tr Flow Rate Measurement
R R q = q −q
s r s r
T −T −∆T
q = r s =
R R
T T
fs fr
This model assumes that the sample and reference calorimeter thermal resistances
are identical, the temperature of the furnace at the sample and reference
calorimeters are equal and does not include other known heat flows.
DSC Training Course
10
Description:A DSC measures the difference in heat flow rate (mW = mJ/sec) between by
the DSC? ▫ Pan Temp: calculated by TA Q1000/2000 based on pan flow heat.
DSC dt. dH. = Weight. Sample. Heat x. Specific. Sample. Capacity. Heat. Sample
For example, thermal resistance of the Tzero DSC cell is determined
