Differential Scanning Calorimetry (DSC)

Theory and Experimental ConditionsGlass TransitionMelting and CrystallizationHeat CapacityMDSC

Differential ScanningCalorimetry (DSC)

Differential Scanning Calorimetry (DSC) measures the temperatures and heat flows associated with transitions in materials as a function of time and temperature in a controlled atmosphere.

These measurements provide quantitative and qualitative information about physical and chemical changes that involve endothermic or exothermic processes, or changes in heat capacity.

DSC: The Technique

TA Instruments DSC’s

DSC 2010 DSC 2910 DSC 2920

DSC: What DSC Can Tell You

Glass TransitionsMelting and Boiling PointsCrystallization time and temperaturePercent CrystallinityHeats of Fusion and ReactionsSpecific HeatOxidative/Thermal StabilityRate and Degree of CureReaction KineticsPurity

DSC: Definitions

A calorimeter measures the heat into or out of a sample.

A differential calorimeter measures the heat of a sample relative to a reference.

A differential scanning calorimeter does all of the above and heats the sample with a linear temperature ramp.

Endothermic heat flows into the sample.

Exothermic heat flows out of the sample.

DSC: Heat Flow/Specific Heat Capacity

∆H = Cp ∆Tor in differential form

dH/dt = Cp dT/dt + thermal eventswhere:

Cp = specific heat (J/g°C)T = temperature (°C)H = heat (J)dH/dt = heat flow (J/min.)mW = mJ/secdT/dt = heating rate (°C/min.)

assuming work & mass loss are zero

DSC: Measurement of HF and T

Sample Ref

chromel alumel

constantanCu-Ni

Ni-Cr Ni-Al

Platinel ControlThermocouple

Ag furnace

DSC: Temperature Measurement

Sample Temperature Ts

Sample Ref

FurnaceTemperature

Tc

DSC: Heat Flow Measurement

Sample Ref

Potential Difference ∆UTemperature Difference ∆T

Heat Flow dQ/dt

Alumel wire (sample temp)

Chromel wires (∆T)

DSC: Cell Schematic DiagramDynamic Sample Chamber

Reference PanSample Pan

Lid

Gas Purge Inlet

Chromel Disc

Heating Block

Chromel Disc

Alumel Wire

Chromel Wire

Thermocouple Junction

Thermoelectric Disc (Constantan)

DSC: Cell Components

Silver Furnace: for good temperature uniformity

Sample Purge: for excellent oxidative stability measurements

Purge Preheated: for very low noise from turbulence

Air Cool: for fast return to room temperature

DSC: Heat Flux Principle

The differential temperature ( ) between the sample andreference is converted to differential heat flow in a way thatis analogous to current flow in Ohms Law.

I = E/R where: I = currentE = voltage (potential)R = electrical resistance

∆ T

THeat Flow =R

k1 k2 where:

T = temperature difference (potential)R = thermal resistance of constantan disk

k1 = factory-set calibration valuek2 = user-set calibration value

∆

∆

DSC: How Heat Flux is Measured

• Heat flow through the chromel wafer causes a temperature difference ∆T. The temperature difference is measured as the voltage difference ∆Ubetween the sample and reference constantan/chromeljunctions. The voltage is adjusted for thermocouple response S and is proportional to heat flow.

∆T = ∆U / S ∆T in °C∆U in µVS in µV/°C

DSC: Related Instrumentation

• Modulated DSC (MDSC) : sinusoidal oscillation superimposed on linear temperature ramp

• Differential Thermal Analysis (DTA)

• Pressure DSC (PDSC)

• Differential Photocalorimetry (DPC)

• Dual Sample DSC

• SDT 2960 Simultaneous DSC-TGA

DTA

Differential Thermal Analysis (DTA) : measures the temperatures and temperature differences (between sample and reference) associated with transitions in materials as a function of time and temperature in a controlled atmosphere

(TAI DTA: up to 1600°C <-> TAI DSC: up to 725°C)

PDSC

Pressure DSC (PDSC) : capability of operating at elevated pressure or at a vacuum (TAI PDSC: 1 Pa - 7 Mpa)

DPC & Dual Sample DSC

•Differential Photocalorimetry (DPC) :sample is exposed to UV/Vis radiation

•Dual Sample DSC: Allows two samples to be ran simultaneously

SDT 2960

•SDT 2960 Simultaneous DSC-TGA: measures heat flow and weight changes simultaneously

DSC: Heat Flow Measurements

Calorimeter SignalsTimeTemperatureHeat Flow

Signal Change Properties MeasuredHeat Flow, absolute Specific HeatHeat Flow, shift Glass TransitionExothermic Peak Crystallization or CureEndothermic Peak MeltingIsothermal Onset Oxidative Stability

DSC: Typical DSC Transitions

Temperature

Hea

t Flo

w -

> e

xoth

erm

ic

GlassTransition

Crystallization

Melting

Cross-Linking(Cure)

Oxidation or

Decomposition

Available Method Segments

Method Design Rules

Typical Methods (Examples)

DSC: Experimental Design

DSC: Available Method Segments

JUMP ABORT NEXT SEG*EQUILIBRATE SAMPLING INTERVALINITIAL TEMPERATURE SELECT GASRAMP EXTERNAL EVENTISOTHERMAL DATA STORAGEISO-TRACK AIR COOL*STEP LNCA CONTROL*INCREMENT MARK END OF CYCLE*REPEAT SEGMENT x FOR y TIMES MODULATE#REPEAT SEGMENT x TILL y °C

* Available on DSC 29XX only# Available on MDSC 29XX only

DSC: Method Design Rules

Start TemperatureGenerally, the baseline should have three (3) minutes to completely stabilize prior to the transition of interest. Therefore, at 10°C/min., start at least 30°C below the transition onset temperature

End TemperatureAllow a three (3) minute baseline after the transition of interest in order to correctly select integration or analysis limits

DSC: Heating/Cooling Method

Heating Method(NOTE: No equilibrate segment necessary ifstarting at or near ambient temperature.)1) Ramp 10°C/min. to 300°C

Cooling Method1) Equilibrate at 300°C2) Ramp 10°C/min. to 25°C

DSC: Heat-Cool-Reheat Method

Heat-Cool-Reheat Method

1) LNCA control: High2) Ramp 10°C/min. to 300°C3) Mark cycle end 04) Ramp 10°C/min. to 25°C5) Mark cycle end 06) Ramp 10°C/min. to 300°C7) Mark cycle end 0

The first segment in this method allows for rapid coolingafter Segment 2 is complete.

DSC: Oxidative Stability (OIT) Method

OIT Method

1) Equilibrate at 60°C2) Isothermal for 5.00 min.3) Ramp 20°C/min. to 200°C4) Isothermal for 5.00 min.5) Abort next seg. if W/g > 1.06) Select gas: 27) Iso-track for 200.00 min.

DSC: Modulated DSC Method

MDSC Method

1) Data storage: off2) Equilibrate at -20°C3) Modulate ±1°C every 60 seconds4) Isothermal for 5.00 min.5) Data storage: on6) Ramp 3°C/min. to 300°C

DSC: Calibration & Sample Preparation

Instrument CalibrationDifferential Heat Flow (Cell Constant)TemperatureBaseline

MiscellaneousPurge GasCooling AccessoriesEnvironment

Sample PreparationSelecting Experimental ConditionsRoutine Maintenance/Sample Press

DSC: Heat Flow Calibration

Differential Heat Flow (ASTM E968)Heat of fusion (melting) standardsHeat capacity (no transition)

MiscellaneousUse specific purge gas at specified rateCalibrate w/cooling accessory functioning if it will be used to run samplesSingle point used for heat of fusion which is typically accurate to +/- 1-2% from -50°C to 350°CCalibration should not change w/heating rate

DSC: Heat Flow Calibration

Prepare a 10 to 15 mg. sample of indium and premeltprior to first use

Use this sample a maximum of 10 times

Calibrate at least once a month

Typical values for cell constant: 1.0 to 1.2

DSC: Calorimetric Calibration

150 155 160 165 170-15

-10

-5

0

5

Temperature (°C)

Hea

t F

low

(m

W)

157.44°C

Sample: Indium, 5.95 mg.CALIBRATION MODE; 10°C/MINCALIBRATION BASED ON 28.42J/g

Cell Const.: 1.0766Onset Slope: -20.82 mW/°C

DSC: Temperature Calibration

ASTM Method E967Pure metals (indium, lead, etc.) typically usedExtrapolated onset is used as melting temperatureSample is fully melted at the peak

MiscellaneousWith metal standards, calibration should change very little with heating rate

With metal standards, it is not practical to calibrate forchanges in heating rate on polymer samples


150 152 154 156 158 160 162 164-5

-4

-3

-2

-1

0

1

0

10

20

30

40

50

Temperature (°C)

Hea

t F

low

(W

/g)

Der

iv. T

emp

erat

ure

(°C

/min

)Extrapolated Onset

156.61°C28.36J/g

HEATING RATE

157.09°CPEAK


Calibrate at least once a month

Use at least two calibration points up to a maximum of five points

Use tin, lead, and zinc one time only

Benzoic acid (147.3 J/g) Tm = 123°CUrea (241.8 J/g) Tm = 133°C Indium (28.45 J/g) Tm = 156.6°CAnthracene (161.9 J/g) Tm = 216°C

Cyclopentane* -150.77°CCyclopentane* -135.09°CCyclopentane* -93.43°CCyclohexane# -83°CWater# 0°CGallium# 29.76°CPhenyl Ether# 30°Cp-Nitrotoluene 51.45°CNaphthalene 80.25°CIndium# 156.60°CTin# 231.95°CLead* 327.46°CZinc# 419.53°C

DSC: Recommended Temperature &Enthalpy Standards

* GEFTA recommendedThermochim. Acta, 219 (1993) 333.

# ITS 90 Fixed Point

Zone refined organic compound(sublimes)

Enthalpy(cell constant)

Temperature

DSC: Traceable Calibration Materials

NIST DSC calibration materials:SRM 2232 Indium Tm = 156.5985°CSRM 2220 Tin Tm = 231.95°CSRM 2222 Biphenyl Tm = 69.41°CSRM 2225 Mercury Tm = -38.70°CSRM 2221b Zinc Tm = In Preparation

NIST: Gaithersburg, MD 20899-0001Phone: 301-975-6776Fax: 301-948-3730Email: [email protected]: HTTP://ts.nist.gov/srm


LGC DSC Calibration Materials:LGC2601: Indium (TA p/n: 915060-901)LGC2608: LeadLGC2609: TinLGC2611: Zinc

Laboratory of the Government Chemist, UKPhone: 44 (0) 181 943 7565Fax: 44 (0) 181 943 7554Email: [email protected]


Certified materials used to establish traceability of instrument calibration

ISO/GLP certification often requires third party calibration of instruments:

Service provided by TA Instruments service representative using certified materialsCertificate of Calibration issued showing traceability of calibration to a national laboratory

DSC: Effect of Heating Rateon Indium Melting Temperature

154 156 158 160 162 164 166 168 170-5

-4

-3

-2

-1

0

1

Temperature (°C)

Heat Flow (W/g)

Heating Rates = 2, 5, 10, & 20°C/min

DSC: Effect of Heating Rateon Indium Melting Temperature

Heat Rate Onset Peak ∆HOnset

Variationto 10°C/min

2°C/min 156.49°C 156.61°C 28.46 J/g -0.12°C

5 156.54 156.75 28.45 -0.07

10 156.61 156.87 28.46 0

20 156.76 157.08 28.44 +0.15

DSC: Polymer Sample w/InternalTemperature Calibration Material

2 Layersof Polymer

Film

Melting PointStandard, e.g.

Indium

Typical weight of polymer sample is 10mg(2 films at 5mg each) with 1-3mg of Indium

DSC: Indium Sample Placed BetweenTwo HDPE Film Samples

PolyethyleneMelt

IndiumMelt

20 40 60 80 100 120 140 160 180-6

-4

-2

0

Temperature (°C)

Heat Flow (W/g)

Sample: Linear Polyethylene-IndiumSize: 10.0000 mg Operator: LabMethod: VarHeat Run Date: 11-Jun-97 12:43Comment: DSC @ 2,5,10%20°C/min; crimped pans, HS Cmpd

DSC

DSC: Effect of Heating Rate on HDPEand Indium Melting

PolyethyleneMelt

IndiumMelt

20 40 60 80 100 120 140 160 180-8

-6

-4

-2

0

Temperature (°C)

Heat Flow (W/g)

DSC: Effect of Heating Rate on Indium Melting When Placed Between Polymer Films

154 156 158 160 162 164 166 168 170

-2.0

-1.5

-1.0

-0.5

0.0

0.5

Temperature (°C)

Heat Flow (W/g)

Heating Rates = 2, 5, 10 & 20°C/min

DSC: Effect of Heating Rate on Indium MeltingWhen Placed Between Polymer Film

Heating RateStandardSample

Polymer SandwichSample

2°C/min -0.12°C +.03°C

5 -0.07 +.16

10 0 +0.44

20 +0.15 +0.82

Onset Variation When Calibrated at 10°C/min.

DSC: Baseline Calibration

SlopeCalibration should provide flat baseline with empty pansPolymers should always have an endothermicslope due to increasing heat capacity withincreasing temperature

CurvatureNot normally part of calibration procedureCan be eliminated if necessary with baselinesubtractionCurvature can cause errors in analyses

DSC: Baseline Slope

20 40 60 80 100 120 140 160 180 200-2.0

-1.5

-1.0

-0.5

0.0

0.5

Temperature (°C)

Hea

t F

low

(W

/g)

Empty Pans

10 mg Polystyrene

DSC: Baseline Curvature

100 150 200 250 300 350-0.2

-0.1

0.0

0.1

-0.2

0.0

0.2

0.4

Temperature (°C)

Hea

t F

low

(W

/g)

Hea

t F

low

(W

/g)

Heating @ 1°C/min

Heating @ 3.5°C/min

SDT 2960 Calibration

•DTA Baseline and empty beams

TGA Weight Calibration calibration weights

•Temperature Calibration up to 5 temperature

standards

•DSC Heat Flow Calibration sapphire

SDT 2960 DSC Heat Flow Calibration

•Two scans from ambient to 1500°C at 20 °C/min•empty alumina pans•sapphire in alumina sample pan

•Use Thermal Solutions/Thermal Advantage NT Software to analyze

•E-curve will be calculated and transferred to the module when the user accepts the results

DSC: Instrument Preparation

Purge GasType of purge gas and flow rate affect calibration and therefore

should be controlledNitrogen is preferred because it is inert and calibration is least

affected by changes in flow rate

Cooling AccessoriesIf used, they should be operating and equilibriated prior to

calibration or sample runs

Warm-up Time/EnvironmentElectronics should be given at least one hour to stabilize for

important samples if the instrument has been turned OFFElectronics are effected by ambient temperature. Avoid areas such

as hoods or near an air conditioner

DSC: Recommended Purge Gas FlowRates & Effect of Flow Rate

Purge Port (mL/min.)

Module Purge Cool VacuumDSC 2920/2910/2010 50 (N ) 50*

25 (He) 50

* Only needed for subambient or MDSC use. Use dry nitrogen or He gas

Purge Gas Flow Rate Too Slow: Moisture Accumulation and Early Aging of the Cell

Purge Gas Flow Rate Too Fast: Excessive Noise

2

DSC: Effect of Flow Rate on Cell Constant

1.00

1.10

1.20

1.30

1.40

1.50

1.60

1.70

1.80

0 10 20 30 40 50 60 70 80 90 100 110

Purge Gas Flow Rate

Cel

l Con

stan

t

Nitrogen Cell Constant

Helium Cell Constant

DSC: Sample Preparation

Sample WeightSelection of the optimum weight is dependent on a number of factors. The sample to be analyzed must be representative of the total sample

The change in heat flow due to the transition of interest should bein the range of 0.1 - 10mW

- metal or chemical melting: <5mg- polymer Tg or melting: 10mg- composites or blends: >10mg

The accuracy of the analytical balance- sample weight should be accurate to +1%

DSC: Heat Flow Change During aTransition

+

40 60 80 100 120 140 160 180 200 220-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

Temperature (°C)

Heat Flow (mW)

161.17°C1.593mW

69.41°C

73.37°C(H)0.4881mW

143.70°C34.95J/g

DSC: Sample Preparation (cont.)

Sample ShapeKeep sample as thin as possible and cover as much of the pan bottom as possibleSamples should be cut rather than crushed to obtain a thin sampleLids should be used with sample pans in order to keep the sample in contact with the bottom of the pan

Sample PansUse lightest, flattest pan possibleUse hermetic pans to prevent evaporation if it occurs in the same temperature range as the transition of interest

DSC: Experimental Conditions

Reference Pan

Always use a reference pan of the same type used to prepare the sample

Never use a material in the reference pan that has a transition in the temperature range of interest

Because DSC measures the difference in heat flow between a sample and reference, the baseline stabilizes faster if the difference in heat capacity between the sample and reference is kept small by adding weight (same material as pan) to the reference pan so that it is similar in total weight to the sample pan.

DSC: Effect of Reference Pan Weighton DSC Baseline

REFERENCE PAN WITH 2 LIDS1.688mW

REFERENCE PAN WITH 1.5 LIDS

REFERENCE PAN WITH LID

NO REFERENCE PAN

-0.6018mW

-1.953mW

-10.04mW

90 110 130 150 170-12

-10

-8

-6

-4

-2

0

2

4

Temperature °C

Hea

t F

low

(m

W)

Sample: EpoxyWeight: Approx. 10mgHeat Rate: 20°C

DSC: Comparison of DSC Tg Using No ReferencePan and One of Equal Cp to Sample

90 110 130 150 170-0.8

-0.6

-0.4

-0.2

0

0.2

Temperature (°C)

Hea

t F

low

(m

W)

Cp REF = Cp SAMPLE

NO REFERENCE


Heating/Cooling RatesHigh rates increase sensitivity

Low rates increase resolution by providing more time at any temperature

Purge Gasnitrogen increases sensitivity because it is a relatively poor thermal conductorhelium increases resolution because it is a good conductor of heat to or from the sample

dQ

dt = Cp x

dT

dt + (T, t)f

heat flowmeasuredby DSC

= heat capacityor weightof sample

x heatingrate

+ time dependentor kineticcomponent


General Summary

ConditionTo IncreaseSensitivity

To IncreaseResolution

Sample Size Increase Decrease

Heat Rate Increase Decrease

Ref Pan Weight Increase No Effect

Purge Gas Nitrogen* Helium*

*instrument should be calibrated with the samepurge gas as used to run a sample

DSC: Sample Pan Types

Pan TypeAluminumCopperGoldGraphiteAl HermeticAl Alodined HermeticGold HermeticHigh Volume (100µL)Al Solid Fat Index (SFI)Platinum

Upper Temp Limit600°C725°C (in N2)725°C725°C (in N2)600°C (3 atm.)600°C (3 atm.)725°C (6 atm.)250°C (safety lid)600°C (no cover)725°C (no cover)

DSC: Sample Pan SelectionStandard Aluminum Pans

Use a thin layer

Distribute materialevenly

DSC: Sample Preparation – Hermetic Pans

Spread Material Evenly

Do not overfill!!

Sample Type Measurement Pan Type

solid Tg,Tm std., hermetic, open(nonvolatile) OIT SFI, open

Cp std.solid (volatile) Cp hermeticliquid Tn,Tc,Tg,Tm hermetic, SFI, open

Cp hermeticOIT SFI, open

aqueous solution Cp,Tm,Tg alodined or goldhermetic

foods/biologicals denaturation high volume (100µL)

DSC: Sample Pan Selection

DSC: Recommended Cell Maintenance

Cleaning the DSC cell (bakeout)(use this procedure for cleaning a contaminated cell)

Air purge = 50mL/min.Ramp 20°C/min. to 600°CIsothermal for 10 min.Cool cell to room temperatureBrush out cell with fiberglass brushCheck for improved baseline performance

NEVER use solvents to clean DSC cell

Thermoplastic Polymers

Semi-Crystalline (or Amorphous)

Crystalline Phasemelting temperature Tm(endothermic peak)

Amorphous Phaseglass transition temperature (Tg)(causing ∆Cp)

Tg < TmCrystallizable polymer can crystallize

on cooling from the melt at Tc(Tg < Tc < Tm)

DSC: Selecting Experimental Conditions

Thermoplastic Polymers

Perform a Heat-Cool-Heat Experiment at 10°C/min.

First heat data is a function of the material and an unknown thermal history

Cooling segment data provides information on the crystallizationproperties of the polymer and gives the sample a known thermal history

Second heat data is a function of the material with a known thermal history

DSC: Thermoplastic: Heat/Cool/Heat

0 20 40 60 80-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0

50

100

150

200

250

300

Time (min)

Hea

t F

low

(W

/g)

[

] T

emp

erat

ure

(°C

)First Heat Cooling

SecondHeat

DSC: Thermoplastic: Heat Flow vs.Temperature for Heat/Cool/Heat

20 40 60 80 100 120 140 160 180 200 220 240 260 280-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

Temperature (°C)

Hea

t F

low

(W

/g)

Second HeatFirst Heat

Cool

191.41°C

223.01°C48.03J/g


Thermoplastic Polymers (con't)Interpreting Heat-Cool-Heat Results:One of the primary benefits of doing Heat-Cool-Heat is for the comparison of two or more samples which can differ inmaterial, thermal history or both

If the materials are different then there will be differences in the Cool and Second Heat resultsIf the materials are the same and they have had the same thermal history then all three (H-C-H) segments will be similarIf the materials are the same but they have had different thermal histories then the Cool and Second Heat segments are similar but the First Heats are different

Selecting Experimental Conditions

• During first heat the maximum temperature must be higher than the melting peak end; eventually an isothermal period must be introduced

– too high temperature/time: decomposition could occur

– too low temperature/time: possibly subsequent memory effect because of the fact that crystalline order is not completely destroyed

• For non-crystallizable (amorphous) thermoplastics the maximum temperature should be slightly above Tg (removal of relaxation effects, avoid decomposition)

Thermosetting Polymers

Thermosetting polymers react (cross-link) irreversibly. A+B will give out heat (exothermic) when they cross-link (cure). After cooling and reheating C will have only a glass transition Tg.

A + B C

GLUE


Thermosetting PolymersAnneal the sample, then Heat-Cool-Heat at 10°C/min.

Anneal approximately 25°C above Tg onset for 1 minute to eliminate enthalpic relaxation from TgFirst Heat is used to measure Tg and residual cure (unreactedresin). Stop at a temperature below the onset of decompositionCooling segment gives the sample a known thermal historySecond Heat is used to measure the Tg of the fully cured sample. The greater the temperature difference between the Tg of the First and Second Heats the lower the degree of cure of the sample as received

DSC: Effect of Annealing on the Shapeof the Glass Transition

0 10 20 30 40 50 60 70 80 90 100-0.4

-0.3

-0.2

-0.1

0.0

-0.2

0.0

0.2

0.4

Temperature (°C)

Hea

t F

low

(W

/g)

Hea

t F

low

(W

/g)

annealed

aged

DSC: Thermoset: Comparison of Firstand Second Heating Runs

0 50 100 150 200 250 300-0.24

-0.20

-0.16

-0.12

-0.08

-0.04

Temperature (°C)

He

at

Flo

w (

W/g

)

Tg

Tg

155.93°C

102.64°C20.38J/g

Residual Cure

First

Second

DSC: Determination of % Cure

79.33J/g75.21 % cured

NOTE: Curves rescaled and shifted for readability

145.4J/g54.55 % cured

Under-cured Sample

Optimally-cured Sample-5.27°C(H)

DSC Conditions:Heating Rate = 10°C/min.Temperature Range = -50°C to 250°CN2 Purge = 50mL/min.

-12.61°C(H)

-0.5

0.0

0.5

1.0

1.5

2.0

He

at F

low

(W

/g)

-50 0 50 100 150 200 250

Temperature (°C)Exo Up Universal V2.4F TA Instruments

DSC: Characterization of Epoxy Prepreg

What is it?

How is it observed and measured?

What affects the Glass Transition?

DSC: The Glass Transition (Tg)

DSC: What is the Glass Transition?

The Glass Transition is the reversible change of the amorphous region of a polymer from, or to, a viscous or rubbery condition to, or from, a hard and relatively brittle one.

The Glass Transition Temperature is a temperature taken to represent the temperature range over which the glass transition takes place.

DSC: Some Properties Affected at Tg

Physical property Response on heating through Tg

Specific Volume Increases Modulus DecreasesCoefficient of thermal expansion

Increases

Specific Heat IncreasesEnthalpy IncreasesEntropy Increases Temperature

V,1/E,

CTE

CpH &S

Tg

DSC: Measurements of the Tg

TEMPERATURE (°C)

en

do

HE

AT

FL

OW

exo

To Tf

TmTi Te Tr

T = Temperature of First Deviation ( C)

T = Extrapolated Onset Temperature ( C)

T = Midpoint Temperature ( C)

T = Inflection Temperature ( C)

T = Extrapolated Endset Temperature ( C)

T = Temperature of Return-to-Baseline ( C)

oo

fo

mo

io

eo

ro

1/2h

1/2h

DSC: Polyethylene TerephthalateGlass Transition

40 60 80 100 120-1.0

-0.9

-0.8

-0.7

-0.6

Temperature (°C)

Hea

t F

low

(m

W)

71. 54° C

0. 3005mW

79. 88° C

DSC: What Affects the Glass Transition?

Heating Rate Crystalline ContentHeating & Cooling CopolymersAging Side ChainsMolecular Weight Polymer BackbonePlasticizer Hydrogen BondingFiller

DSC: Heating Rate

Heating Rate Sensitivity Reproducibility(°C/min)

5 poor very good20* good good40 very good poor

* Recommended heating rate for measuring Tg.

DSC: Heating/Cooling of Polystyrene

75 80 85 90 95 100 105 110 115-0.10

-0.05

0.00

0.05

0.10

0.15

Temperature (°C)

DS

C H

eat

Flo

w (

W/g

) 10 °C/min COOLING

10 °C/min HEATING

MDSC: Heating/Cooling of Polystyrene

75 80 85 90 95 100 105 110 1150.50

0.60

0.70

0.80

0.90

1.00

Temperature (°C)

Hea

t C

apac

ity

(J/g

/°C

)

5 °C/min COOLING

5 °C/min HEATING

Effect of Cooling Rate on Tg

increased amorphousfraction

Quench

20

10

0.2

Heat Capacity MeasuredAfter Cooling at Quench,20, 10, 5, 2, 1 and 0.2°C/min

20 40 60 80 100 120 140 160

1.0

1.2

1.4

1.6

1.8

2.0

Temperature (°C)

Hea

t C

apac

ity

(J/g

°C)

DSC: Effect of Aging on the GlassTransition [M. Todoki, Polymer Data Handbook]

0 50 100 150Temperature (°C)

Glass Transition

Cold Crystallization

As-Spun

2 days

28 days

196 days

3 years and2 months

4 years and11 months

DSC: Effect of Annealing on Polystyrene

40 60 80 100 120 140 160-0.3

-0.2

-0.1

0.0

0.1

0.2

Temperature (°C)

Heat Flow (W/g)

Sample: Polystyrene; effect anneal @ 95°Size: 11.6600 mg Operator: LabMethod: Anneal Times Run Date: 3-Jun-97 16:41Comment: DSC @ 10°C/min; N2 @ 50cc/min; 12.8mg A1 in ref.; crimped pans

DSC

Anneal Times = 0, 10, 100 & 1000 minutes

DSC: Effect of Annealing Time at 95°Con Shape of Polystyrene Tg

80 90 100 110 120 130- 0. 25

- 0. 20

- 0. 15

- 0. 10

- 0. 05

Temper at ur e ( ° C)

He

at

F

lo

w

(W

/g

)

0. 00Anneal Times = 0, 10, 100 & 1000 minutes

DSC: Effect of Molecular Weighton the Tg (for Styrene Oligomers/Polymers)

Molecular Weight Tg104 -138°C524 - 40°C

2,210 40°C3,100 62°C

15,100 86°C36,000 94°C

170,000 100°C

Turi, pg 249 Kumler, 1977

DSC: Effect of Plasticizer on the Tg

for Polyamides

Water Content (%) Tg (°C)0.35 940.70 841.17 711.99 562.70 454.48 406.61 23

10.33 6

DSC: Effect of Filler and CrystallineContent on the Tg

Decreases magnitude of Cp shift

Broadens temperature range of Glass Transition

Increases the Tg

DSC: Copolymers

0 20 40 60 80 100

370

410

450

490

PPO (wt. %)

Tg

(K)

DSC: Effect of Side Chains on the Tg

for - CH2 - CH(R) -

Side Chain Tg (°C)-H

-CH3

-CH2(CH3)

−C6H5

cyclohexyl

-C6H4 - (4 - C6H5)

-36

-12

64

100

120

161

DSC: Effect of Polymer Backboneon the Tg

N Tg (°C)2 -413 -784 -84

for -O-(CH2)n -

DSC: Effect of Hydrogen Bondingon the Tg

Polyamide Tg (°C) HBondingNylon 12,2 59 LeastNylon 10,2 56Nylon 8,2 93Nylon 6,2 159 Most

DSC: Melting and Crystallization

Terminology

Observations of Melting and Crystallization

Crystallinity Calculations

Applications

DSC: Terminology

Amorphous Phase - The portion of material whose molecules are randomly oriented in space. Liquids and glassy or rubbery solids. Thermosets and some thermoplastics.Crystalline Phase - The portion of material whose molecules are regularly arranged into well defined

structures consisting of repeat units. Very few polymers are 100% crystalline.Semi-crystalline Polymers - Polymers whose solid phases are partially amorphous and partially

crystalline. Most common thermoplastics are semi-crystalline.Endothermic - A transition which absorbs energy.Exothermic - A transition which releases energy.Melting - The endothermic transition upon heating from a crystalline solid to the liquid state. This process

is also called fusion. The melt is another term for the polymer liquid phase.Crystallization - The exothermic transition upon cooling from liquid to crystalline solid. Crystallization

is a function of time and temperature.Cold Crystallization - The exothermic transition upon heating from the amorphous rubbery state to the

crystalline state. This only occurs in semi-crystalline polymers that have been quenched (very rapidly cooled from the melt) into a highly amorphous state.Enthalpy of Melting/Crystallization - The heat energy required for melting or released upon

crystallization. This is calculated by integrating the area of the DSC peak on a time basis.

Observation of Melting

250.61°C

236.94°C45.30J/g

12.73°C

Peak Temperature

Extrapolated Onset Temperature

Area under the curve (Heat of Fusion)

Width @ half height

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

He

at

Flo

w (

W/g

)

180 200 220 240 260 280 300 320

Temperature (°C)Exo Up

DSC: Melting Points and Ranges

• To is the onset to melting• Tp is the melting peak temperature• Te is the end of melting

Pure, low molecular weight materials (mw<500 g/mol)• To is used as the melting temperature (Tm)• Between To and Tp the sample is melting• Between Tp and Te the molten sample is returning to the

DSC temperature

Polymers• Tp is used as the melting temperature (Tm)• Between To and Tp crystal perfection is occurring (both

melting and crystallization occurs simultaneously)• Between Tp and Te the sample is finishing melting and

returning to the DSC temperature

DSC: Polyethylene and Indium Melting

100 110 120 130 140 150 160 170-20

-15

-10

-5

0

5

Temperature (°C)

Hea

t F

low

(m

W)

126.96°C191.7J/g

157.59°C28.46J/g

131.12°C157.85°C

Baseline Types: Linear

12.20°C

22.27(24.02)J/g

16.10°C

1.754J/g

0.0

0.1

0.2

0.3H

eat F

low

(W

/g)

-20 -10 0 10 20 30 40

Temperature (°C)Exo Up Universal V2.5D TA Instruments

Baseline Types: Sigmoidal

12.20°C

23.04J/g

0.0

0.1

0.2

0.3

Hea

t Flo

w (

W/g

)

-20 -10 0 10 20 30 40

Temperature (°C)Exo Up Universal V2.5D TA Instruments

DSC: Observation of Crystallization

100 120 140 160 180 200-1.5

-1.0

-0.5

0.0

0.5

1.0

Temperature (°C)

Hea

t F

low

(m

W)

Tn

Tc152.62°C

163.24°C

139.47°C36.60J/g

Te

DSC: Crystallization Point

Crystallization is a two step process:NucleationGrowth

The onset temperature is the nucleation (T )

The peak maximum is the crystallization temperature (T )

N

C

DSC: PET/ABS Blend "As Received"

50 100 150 200 250-0.8

-0.6

-0.4

-0.2

Temperature (°C)

Hea

t F

low

(W

/g) +

67. 38° C

70. 26° C( H)

120. 92° C

111. 82° C9. 016J/ g

249. 75° C

235. 36° C22. 63J/ g

STANDARD DSCFIRST HEAT ON MOLDED PART

Sample must be pure material, not copolymer or filledMust know enthalpy of melting for 100% crystalline material (∆H )You can use a standard ∆H for relative crystallinity

DSC: Calculation of % Crystallinity

lit

lit

For standard samples:

% crystallinity = 100* ∆Hm / ∆Hlit

For samples with cold crystallization:

% crystallinity = 100* (∆Hm - ∆Hc)/ ∆Hlit

DSC: Polymer Crystallinity - Polyolefin

EN

DO

H

EA

T F

LO

W

E

XO

0TIME (min)

4 8 122 6 10 14

Size: 10.5mg Prog: 5° C/min

190

170

150

130

110

90

TE

MP

ER

AT

UR

E (

°C)H = 141 J/g

% Crystallinity = X 100%141

290= 49%

∆

DSC: Applications

Effect of heating/cooling rate

Crystallization kinetics

Effects of polymer structure/composition

Effects of thermal/mechanical processing

DSC: Effect of Heating Rate onNylon 66 Melting Behavior

1 2 3 4Temperature (°C)

end

o

HE

AT

FL

OW

e

xo

240 260 280 300

0.2 mW

1 mW

5 mW

5 mW

10 mW

50°C/min

20°C/min

10°C/min

2°C/min

0.5°C/min

DSC: Effect of Cooling Rate onCrystallization of HDPE

100 110 120 130-10

10

30

50

70

Temperature (°C)

Hea

t F

low

(m

W)

32°C/min

16 8

4

2

1 0.5

DSC: Crystallization Kinetics

Two step processNucleationCrystal growth

Nucleation may beNaturalInduced (using nucleation agents)

Thermally influenced processNatural nucleationCrystal growthModeled by Isothermal Kinetics using the Autocatalytic Model

DSC: Isothermal CrystallizationProcedure

Heat to 10°C above T

Hold for 5 minutes to remove local order

Cool rapidly to below melt onset (DO NOT OVERSHOOT TEMP)

Hold isothermally

Record time to crystallization peak (t )

M

c

DSC: Isothermal Crystallization ofPolyethylene Terephthalate

0 1 2 3 4 5 6

Time (min)

∆T

T1

T2

T3

T4

T T T1 3 4

< < <T2

Blank run

DSC: Effect of Nucleating Agentson Crystallization

8090100110120130140150T (°C)

Exo

ther

mic

NUCLEATEDPOLYPROPYLENE

NON-NUCLEATEDPOLYPROPYLENE

DSC: Supercooling of Water

-30 -25 -20 -15 -10 -5 0 5 10-50

0

50

100

150

200

250

Temperature (°C)

Hea

t F

low

(m

W)

+-4.36°C

-15.55°C

+

DSC: Purity of PharmaceuticalCompounds

Temperature (°C)

-0.8

-1.0

-1.2

-1.4

-1.6

-1.8

-2.0

-2.2

Hea

t Flo

w (

mW

/mg)

122 126 130124 128 132

Total Area/Partial Area

134 136 138

Purity: 99.55 mole % Melting Pt: 134.9°CDepression: 0.24°CDelta H: 26.4 kJ/moleCorrection: 8.11%Mol. Weight: 179.2 g/moleCell Const: 0.977Onset Slope: 10.14 mW/°C

135.0

134.5

134.0

133.5

133.0

132.5

Tem

pera

ture

(°C

)

108 6420

DSC: Effect of Polymer Typeon Melting

Class Structure Melting RangePolyolefins -CH -CH - 85 - 174°CPolyamides -CH -NH-C(O)-CH - 190 - 265°CPolyesters -CH -O-C(O)-CH - 220 - 270°CPolyphenylene

Sulfides -Ph-S- 300 - 360°C

2 2

2 2

2 2

DSC: Effect of Molecular Weighton Melting

Olefin Formula Mole. Wt. Tm

(g/mol) (°C)C12H26 170 -10C24H50 339 54C30H62 423 66C35H72 493 75

DSC: Effect of Hydrogen Bondingon Melting

Polyamide Tm H BondingNylon 12,2 236 LeastNylon 10,2 242Nylon 8,2 279Nylon 6,2 326 Most

Nylon x,y where:x = carbons in diamine sectiony = carbons in diacid section

DSC: Effect of AnnealingPoly(ethyletherketone) (PEEK) on Melting

Heat F

low

(W/g

)

260 280 300 320 340 360 380-0.3

-0.2

-0.1

0.0

Temperature (°C)

PEEK annealed@ 300°C

PEEK

303.61°C

DSC: Effect of Draw Ratioon Melting Temperature

1.0 3.0 5.0 7.0129

133

137

λ

Tm

(°C

)

DSC: Effect of Aromaticity on Melting

Polymer % Aromatic Melting Range

-CH2 - CH2 - 0 105 - 135°CPET 39 250 - 275°C-(Ph)-O- 62 300 - 315°C-(Ph)-S- 70 300 - 360°C

DSC: Effect of Branching on Melting

Polyolefin Branching Tm

LDPE irregular ~ 105°Crandom lengths

LLDPE irregular ~ 127°Cfixed lengths

HDPE none ~ 135°C

PP regular ~ 150°Cfixed lengths

DSC: Melting and Crystallization -Summary

Melting and crystallization are phase changes from organized solid to amorphous phases and vice-versa.

Melting is a one-step process while crystallization involves nucleation and crystal growth.

The enthalpy of melting can be used to measure crystallinity or filler.

Any process that makes it easier for molecules to be organized will raise the melting temperature.

What is it?

How is it observed and measured?

Methods for calculating specific heat capacity

What affects the specific heat capacity of a polymer?

DSC: Specific Heat Capacity

DSC: What is Specific Heat Capacity?

Specific Heat Capacity (Cp) is the amount of heat required to raise the temperature of one gram of a particular material one kelvin of temperature. Specific Heat Capacity is due to the molecular motion in a material (units of J/g K).

Heat Capacity is the amount of heat required to raise the temperature of a material one kelvin of temperature. This is unnormalized specific heat (units of J/K).

Specific heat is the specific heat capacity of an analyte compared to the specific heat capacity of a reference material (dimensionless).

DSC: How are Heat Capacity andSpecific Heat Measured?

In a DSC experiment, heat capacity is measured as the absolute value of the heat flow, divided by the heating rate, and multiplied by a calibration constant.

dH/dt = Cp (dT/dt)or

Cp = [(dH/dt)/(dT/dt)] x E

E = calibration constant

DSC: How Heating Rate ShiftsHeat Flow

40 60 80 100 120 140 160 180 200-10

-8

-6

-4

-2

0

Temperature (°C)

Hea

t F

low

(m

W)

5°C/min

10°C/min

20°C/min

106. 85° C- 2. 137mW

106. 85° C- 40175mW

106. 85° C- 8. 104mW

Cp = Specific Heat Capacity (J/g/°C)E = Calibration Constant (dimensionless)H = Heat Flow (mW)60 = conversion constant (min sec)Hr = Heating Rate (°C/min)M = Sample Mass (mg)

DSC: Specific Heat Capacity Equation

Cp = E x H x 60

Hr x M

DSC: Specific Heat CapacityStep 1. Run Empty Pans

Create Thermal Method, e.g.,

1) Equilibrate @ 50°C2) Isothermal for 10 min.3) Ramp 20°C/min to 300°C4) Isothermal for 10 min.

Run Empty Pans to determine background heat flow

Subtract background heat flow from subsequent measurements

DSC: Specific Heat CapacityStep 2. Determine Value of E

E is temperature-dependant

Heat sapphire disc (Cp standard) through thermal profile

At temperature of interest, calculate E

DSC: Specific Heat CapacityStep 2. Determine Value of E (cont.)

For example, at 380 K (106.85°C), sapphireCp = 0.9161 J/g/°CM = 25.20mgHr = 20°C/minMeasured Heat Flow = 7.25 mW

E = (0.9161 mJ/mg/°C) x (20°C/min) x (25.20 mg)

(7.25 mW (mJ/sec)) x (60 sec/min)

Cp Hr M

H

at 380K, E = 1.06

DSC: Specific Heat CapacityStep 3. Measure Unknown Sample

Use exact same thermal profile as empty pans and sapphire

Measure sample mass, e.g., 14.20 mgMeasure Heat Flow at 380K, e.g., 4.60 mWSubstitute E into equation on page 103.

Cp = (1.06) x (4.60 mW (mJ/sec)) x (60 sec/min)

(20°C/min) x (14.20 mg)Hr M

HE

Cp = 1.030 mJ/mg/°C (J/g/°C)

DSC: What Affects the Specific HeatCapacity?

Amorphous Content

Aging

Side Chains

Polymer Backbone

Copolymer Composition

DSC: Effect of Amorphous Contenton Cp

Amorphous Cp is greater than Crystalline Cp

Amorphous Content increases Specific Heat Capacity

Crystalline polymers contain more order and thus fewer degrees of molecular motion. Less molecular motion results in lower specific heatcapacity.

DSC: Effect of Annealing(Crystallization) on Cp of PEEK

100 110 120 130 140 150 1601.2

1.4

1.6

1.8

2.0

2.2

Temperature (°C)

Co

mp

lex

Cp

(J/

g/°

C)

Amorphous PEEKPEEK annealed at 300°CPEEK annealed at 330°C

DSC: Effect of Aging on the SpecificHeat Capacity of Polystyrene

360 380 400 420Temperature (K)

End

oth

erm

406

272

240120

66

24

3

0

tg (h)

DSC: Effect of Side Chains on SpecificHeat Capacity

Polymer Side Chain Cp (J/g/°C)PE -H 2.763PP -CH 2.752PS -Ph 2.139

As the steric bulk of the side chain increases, molecular mobility decreases resulting in lower specific heat.

B. Wunderlich, ATHAS Cp Data Bank, 1985.

DSC: Effect of Polymer Backbone on Specific Heat Capacity of Polyoxyalkenes @ -153°C

# of Methylenes Cp (J/g/°C)

1 0.62262 0.69183 0.70884 0.75978 0.7736

OCH2n)

O([ ]

As the number of methylenes increase, mobility isincreased in the polymer, resulting in higher heat capacity.


DSC: Effect of Copolymer Composition on Specific Heat Capacity of PE/PP Copolymer @ -93°C

Composition Copolymer Cp(%PP) (Type) (J/°C/mol)

6.0 block 15.127.5 random 16.39

15.5 random 18.54

As PP concentration is increase, the number of methylenesincreases, resulting in a rise in specific heat capacity. Also, with randomness comes entropy, increase in mobility, and increasein specific heat capacity.


Theory

Signals

Applications

Experimental Conditions

Calibration

DSC: Modulated DSCTM

MDSC Theory

Heat Flow Equation

),( tTfdt

dTCp

dt

dH+=

dHdt

= Total Heat Flow measured by the calorimeter

Cp = Specific Heat Capacity

dTdt

= Underlying Heating Rate

f(T,t) = kinetic response of sample

Heat Flow Due to Heat Capacity

4060

80100

120140

160180

200

Temperature (°C)

(10)

(8)

(6)

(4)

(2)

0

Hea

t F

low

(m

W)

5°C/min

10°C/min

20°C/min

106.85°C-2.137mW

106.85°C-4.018mW

106.85°C-8.104mW

Kinetic Heat Flow

time0 t t1 2

Hea

t Flo

w

The magnitude of measured kineticheat flow is a function of time at aconstant temperature.

Isothermal Temperature

Standard DSC Measures the Sum of Heat Flow

Temperature

Hea

t Flo

w

Heat Flow due toHeat Capacity

Heat Flow due toKinetic Events

Heat Flow Can Be Separated

Heat Flow due toHeat Capacity

Heat Flow due toKinetic Events

f(T,t)

CpdT

dt

Temperature

Hea

t Flo

w

General Theory of MDSC

Heat flow from DSC experiments is composed of two partsbut DSC can only measure the sum of the two.

dH/dt = Cp (dT/dt) + f (T,t)

Total = Heat Capacity + KineticHeat Flow Component Component(DSC) = Heating Rate + Time Dependent Dependent

= MDSC Reversing + MDSC Nonreversing

Distribution of Transitions in MDSC Experiments

Total = Heat Capacity + KineticComponent Component

= Reversing Heat Flow + Nonreversing Heat Flow

glass transition melting (some)

enthalpic relaxationevaporationcrystallizationdecompositioncuremelting (some)

Physical Measurement Technique

Apply Stimulus Measure ResponseStimulus Response

FTIR IR Radiation AbsorbanceWavelength

NMR Magnetic Field ResonanceFrequency

X-Ray Diffraction X-Ray Radiation Angle ofDiffraction

MDSC SinusoidalHeating Rate

Amplitude ofHeat Flow

Raw Signals in MDSC

TimeModulated Temperature (Stimulus)Modulated Heat Flow (Response)

All Modulated DSC Signals are derived fromthree measured parameters.

MDSC Raw Signal

MODULATED HEAT FLOW(Response) CRYSTALLIZATION DURING MELTING

MELTING

GLASS TRANSITION

COLD CRYSTALLIZATION

NOTE: ALL TRANSITIONS OFINTEREST ARE CONTAINED INMDSC RAW DATA SIGNALS

MODULATED HEATING RATE(Stimulus)

50 100 150 200 250 300

0

2

4

6

8

-0.6

-0.4

-0.2

0.0

0.2

Temperature (°C)

Deriv. Modulated Temp (°C/min)

Modulated Heat Flow (W/g)

Temperature Change (MDSC)

200

210

220

230

240

Mo

dul

ate

d T

em

p (

°C)

200

210

220

230

240

Te

mp

era

ture

(°C

)

38 39 40 41 42 43 44 45

Time (min)

Exo Up Universal V2.5D TA Instruments

ACTUAL MEASURED TEMPERATURE

CALCULATED AVERAGE

TEMPERATURE

PA

MDSC Signals: Total Heat Flow

The average value of the modulated heat flow signal. This signal is qualitatively and quantitatively equivalent to the heat flow signal from conventional DSC at the same average heating rate.

Definition: The sum of all thermal events in the sample

Calculation: Fourier Transformation analysis of the modulated heat flow signal is used to continuously calculate its average value

Total Heat Flow: Average of Modulated Heat Flow Signal

50 100 150 200 250 300-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

-0.4

-0.2

0.0

0.2

Temperature (°C)


Heat Flow (W/g)

MDSC Signals: Heat Capacity

Where:AMHF = Amplitude of Modulated Heat FlowAMHR = Amplitude of Modulated Heating Rate

K = Heat Capacity Calibration Factor

Definition: The amount of heat required to raise the temperature of a material 1°C.

Calculation: The basis for making the heat capacity measurement in MDSC can be explained from a series of conventional DSC experiments at different heating rates.

K x A

A Cp

MHR

MHF=

Conventional DSC Cp Measurement

x wtRateHeat

HF– HFK x Cp

MTS=

HF

endo

0HFMT

HFS

Temp.

Where:

K = Calibration constant

HFS = Differential heat flow with sample

HFMT = Differential heat flow with empty pans

wt = weight of sample

Alternative DSC Cp Measurement

HF

endo

0HFHR1

HFHR2

Temp.

wt)HR– (HR

HF– HFK x Cp

12

HR1HR2=

Where:

K = Calibration constant

HFHR1 = Differential heat flow of sample at HR1

HFHR2 = Differential heat flow of sample at HR2

HR2 = Heating rate 2

HR1 = Heating rate 1

wt = weight of sample

Heat Capacity from MDSC Raw Signals

50 100 150 200 250 300

0

5

10

-0.6

-0.2

0.2

0.6

Temperature (°C)

Deriv. Modulated Temp (°C/min)


4

2

0

2

4

6

Complex Cp (J/g/°C)HEAT CAPACITY

MODULATED HEAT FLOW

MODULATED HEATING RATE

MDSC Signals - Reversing Heat Flow (Heat Capacity Component)

Reversing Heat Flow is the heat capacity component of the total heat flow. It is calculated by converting the measured heat capacity into a heat flow signal using the classical heat flow equation as a theoretical basis.

Reversing Heat Flow = –Cp x Avg. Heat Rate

t)(T, dt

dT Cp

dt

dHf+=

Basis for Calculation

ing)(Nonrevers process kinetic from flowheat t)(T,

)(Reversingcomponent capacity heat dt

dT Cp

rate heating average dt

dT

capacityheat measured Cp

flowheat total dt

dH

:Where

=

=

=

=

=

f

Reversing Heat Flow from MDSC Raw Signals

50 100 150 200 250 300

-8

-4

0

4

8

-0.25

-0.15

-0.05

0.05

0.15

Temperature (°C)

Co

mp

lex

Cp

(J/

g/°

C)

Rev

Hea

t F

low

(W

/g)

HEAT CAPACITY

REVERSING HEAT FLOW

Quench Cooled PET: Total vs. Reversing Heat Flow

50 100 150 200 250 300-0.3

-0.2

-0.1

0.0

0.1

-0.25

-0.15

-0.05

0.05

0.15

Temperature (°C)

Hea

t F

low

(W

/g)

[

]R

ev H

eat

Flo

w (

W/g

)

TOTAL

REVERSING

MDSC Signals - Nonreversing Heat Flow (Kinetic Component)

Nonreversing Heat Flow is the kinetic component of the total heat flow. It is calculated by subtracting the heat capacity component from the total heat flow using the classical heat flow equation as a theoretical basis.

Nonreversing = Total – Reversing

Basis for Calculation

ing)(nonreverscomponent kinetic t)(T,

)(reversingcomponent capacity heat dt

dT Cp

flowheat total dt

dH

t)(T, dt

dT Cp

dt

dH

=

=

=

+=

f

f

Quench-Cooled PET: Deconvoluted Signals

50 100 150 200 250 300-0.25

-0.15

-0.05

0.05

0.15

0.25

-0.25

-0.15

-0.05

0.05

0.15

0.25

Temperature (°C)

Hea

t F

low

(W

/g)

Rev

Hea

t F

low

(W

/g)

-0.2

-0.1

0.0

0.1

No

nre

v H

ea

t F

low

(W

/g)

NONREVERSING

TOTAL

REVERSING

Glass Transition of Polymer Resin

MDSC: Glass Transition of Epoxy Coating

0 20 40 60 80 100 120 140-0.30

-0.28

-0.26

-0.24

-0.22

-0.20

-0.10

-0.08

-0.06

-0.04

-0.02

0.00

Temperature (°C)

Hea

t F

low

(m

W)

Rev

Hea

t F

low

(m

W)

TOTAL

REVERSING

NOTE: Sensitivity is 100µW Full Scale

PET/ABS Blend - Conventional DSC

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

-0.8

Temperature (°C)50 100 150 200 250

Hea

t Flo

w (

W/g

)

first heat on molded part

(Curve shifted on Y axis to avoid overlap)

second heat after 10°C/min cooling

120.92°C67.38°C

70.262°C (H)235.36°C

111.82°C9.016J/g

22.63J/g

249.75°C

9.22 mg sample, nitrogen purge 10°C/minute heating rate

PET/ABS - MDSC

8.46mg sample

nitrogen purge

2°C/minute heating rate, ±1°C amplitude, 60 second period

first heat on molded part

PET Tg

ABS Tg

-0.10

-0.11

-0.12

-0.13

-0.14

-0.15

Temperature (°C)

40 60 100 120 140

Hea

t Flo

w (

mW

)

20 80 160

-0.02

-0.03

-0.04

-0.05

-0.06

-0.04

-0.05

-0.06

-0.07

-0.08

-0.09

(

)

Non

rev.

Hea

t Flo

w (

W/g

)

(

)

Rev

. Hea

t Flo

w (

W/g

)

67.00°C+72.89°C (H)

104.45°C

107.25°C (H)

180 200

MDSC: Detection of Two GlassTransitions in PC/PEE Blend

40 60 80 100 120 140 160

-0.12

-0.10

-0.08

-0.06

-0.04

-0.02

-0.005

-0.004

-0.003

-0.002

-0.001

Temperature (°C)

Re

v H

eat

Flo

w (

W/g

)

De

riv.

Re

v H

ea

t F

low

(W

/g/m

in)

3 CONSECUTIVE HEATING RUNS AFTER 2deg/min COOLING

DERIVATIVE

NOTE 81°C WIDTH OF GLASS TRANSITION

3

2

1

62. 58° C

141. 45° C

MDSC ±0.424°C, 40 sec. period4°C/min underlying ramp rate

+

+

MDSC: Heat Capacity for PET DuringIsothermal Steps

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

1.0

1.2

1.4

1.6

60

80

100

120

140

Time (day)

Hea

t C

apac

ity

(J/g

/°C

)

Tem

per

atu

re (

°C)

PLOT vs TIME

Heat Capacity

Temperature

MDSC ±0.30°C, 40 sec. period1°C isothermal steps

MDSC: PET Heat Capacity During GlassTransition & Cold Crystallization

60 70 80 90 100 110 120 130

1.1

1.2

1.3

1.4

1.5

1.6

Temperature (°C)

Hea

t C

apac

ity

(J/g

/°C

)

COLD CRYSTALLIZATION(First-Order Transition)

GLASS TRANSITION(Second-Order Transition)

MDSC ±0.30°C, 40 sec. period1°C isothermal steps

Isothermal Epoxy Cure

∆H of Cure6

4

2

0

Time (min)5 10 20 25 30

Non

rev.

Hea

t Flo

w (

mW

)

Heat Capacity

Isothermal 80°C helium purge ±0.5°C amplltude 60 second period

DMA 1Hz

0 15 35 40

30

20

10

0

(

)

Hea

t Cap

acity

(m

J/°C

)14.5

14.0

13.5

13.0

12.5

12.0

11.5

(

)

E' (

GP

a)

MDSC: Heat Capacity vs. Cure TimeTM =Epoxy-Amine System MDSC Result at 70°C Cure

Thermochimica Acta, 268, 121-142 (1995), Dr. B. Van Mele, et alat Vrije Universiteit Brussels (Belgium)

=

0 100 200 3000

30

60

90

120

1.0

1.5

2.0

2.5

Time (min)

(

)

No

nre

vers

ing

Hea

t F

low

(m

W/g

)

(

) H

eat

Cap

acit

y (J

/g/K

)

exo

t1/2 Cp∆

t1/2 Cp

vit

= 97 mi

X = 0.53∆

Nonreversing Heat Flow

Heat Capacity

MDSC: Experimental Considerations

Modulation Period?

Modulation Amplitude?

Sample Dimensions?

Purge Gas?

Sample Preparation?

Phase Correction?

Calibration?

MDSC: Sample Preparation

Thin, Low Mass SamplesMinimize Thermal GradientsAllow for Faster Periods, Larger

Modulation Amplitudes

Thicker, Heavier SamplesMinimize Baseline CurvatureImprove Sensitivity

Low, Consistent MassBest Choice for MDSC MeasurementsSolids, Powders, FilmsVolatility may be an issue

MDSC: Sample PansStandard Crimped

MDSC: Sample PansStandard Hermetic

Use for liquid/volatile samplesHigher Mass, Less SensitivityUse Heat Sink Compound

NitrogenEconomicalWide Operating RangeProvides Good Sensitivity

HeliumHigher Thermal ConductivityFacilitates Wider Range of Modulation ConditionsReduces Baseline Curvature

MDSC: Purge Gas

MDSC: Purge Gas Flow Rates

Use Purge Gas Flow Rate of 50 mL/min. (N2) & 25 ml/min (He)

Faster rates increase noiseSlower rates decrease sensitivity, increase baseline curvature

Flow Purge Gas through Vacuum Portat 50 mL/min.Improves response of furnaceFacilitates wider range of modulationparameters

MDSC: Baseline Calibration

Identical to Standard DSC experimentEliminates Baseline DriftDoes not affect curvature -Slower heating rates contribute tocurvature-Heavier sample masses minimize curvature

-200 -100 0 100 200 300 400-10

-8

-6

-4

Temperature (°C)

Del

ta (

V

)µ

Baseline Calibration - 2920 MDSC (4)<

Sample: Empty Pans DSC File: D:\TA\DSC\...BASE1102.001

Baseline CalibrationSlope: -0.0005Offset: -8.564Cell Number: 319

-90.29°C287.04°C

MDSC: Heat Flow (Cell Constant)Calibration

Identical to Standard DSC CalibrationBaseline Calibration - 2920 MDSC (4)v

Sample: Indium Metal DSC File: D:\TA\DSC\DATA\CAL0512.001

150 152 154 156 158 160 162 164-25

-20

-15

-10

-5

0

Temperature (°C)

Hea

t F

low

(m

W)

Cell Constant CalibrationIndium Standard Heat: 28.71 J/gCell Constant: 1.5555Onset Slope: -40.63 mW/°CCell Number: 319

157.74°C

MDSC: Cell Constant Effect onModulated Heat Flow

25 75 125 175 225 275-4

-2

0

2

4

Temperature (°C)

Mo

du

late

d H

eat

Flo

w (

mW

)

E = 0.5E = 1.0E = 1.6

MDSC: Heat Capacity Calibration

Provides for Accurate Heat Capacity MeasurementsUse Either Sapphire Disc (wide temperature range) or HDPE (polymer melt)Choose one-point or average valuesEffects of Experimental Conditions

MDSC: Heat Capacity Calibration-Frequency Dependence

0.8

0.9

1

1.1

1.2

1.3

0 10 20 30 40 50 60 70 80 90 100

Temperature (°C)

K(C

p)

10 Sec20 Sec30 Sec40 Sec50 Sec60 Sec70 Sec80 Sec90 Sec100 Sec

MDSC: Heat Capacity CalibrationFrequency Dependence (cont.)

0.85

0.87

0.89

0.91

0.93

0.95

0 10 20 30 40 50 60 70 80 90 100

Temperature (°C)

K(C

p)

40 Sec50 Sec60 Sec70 Sec80 Sec90 Sec100 Sec

MDSC: Heat Capacity CalibrationAmplitude Dependence

0.84

0.85

0.86

0.87

0.88

0.89

0.9

0.91

0.92

0.93

0.94

0 10 20 30 40 50 60 70 80 90 100Temperature (°C)

K(C

p)

0.10°C0.25°C0.50°C0.75°C1.00°C1.25°C1.50°C1.75°C2.00°C

MDSC: Heat Capacity Calibration -Heating Rate Dependence

0.84

0.86

0.88

0.9

0.92

0.94

0 10 20 30 40 50 60 70 80 90 100

Temperature (°C)

K(C

p)

1°C/min

3°C/min

5°C/min

Isothermal

Effect of Modulation Conditions on K

Period (sec)

Each color gradient represents a 5% change in K.

10 20 30 40 50 60 70 80 90 1000.1

0.2

0.4

0.81

1.21.4

1.61.8

2

1.00

1.10

1.20

1.30

1.40

1.50

1.60

K

Amplit

ude (±°C

)

He purge @ 25 ml/min.

Differential Scanning Calorimetry (DSC)

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