DSC原理與應用

TA Instruments User Training

許炎山

TA Instruments, Waters LLC

美商沃特斯國際股份有限公司台灣分公司

TA Taipei office: 104臺北市長安東路1段23號4F之5

Tel: 02-25638880 Fax: 02-25638870

C/P: 0928-168676 E/M : jhsu@tainstruments.com

2012年9月7日國立台灣大學化學系 潘貫講堂 (B棟積學館2樓演講廳)

基礎應用

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 →

exot

herm

ic

GlassTransition Crystallization

Melting

Cross-Linking(Cure)

Oxidation or

Decomposition

-0 .4

-0 .3

-0 .2

-0 .1

0 .0

0 .1

Hea

t Flo

w (W

/g)

0 2 5 5 0 7 5 1 0 0 1 2 5 1 5 0

T e m pe ra tu re (蚓 )E xo U p

Endothermic Heat Flow

Heat FlowEndothermic: heat flows into the sample as a result of either heat capacity (heating) or some endothermic process (glass transition, melting, evaporation, etc.)

-0 .1

0 .0

0 .1

Hea

t Flo

w (W

/g)

0 20 40 60 80 100 120 140 160

Tem perature (蚓 )Exo Up

Exothermic Heat Flow

Heat FlowExothermic: heat flows out of the sample as a result of either heat capacity (cooling) or some exothermic process (crystallization, cure, oxidation, etc.)

Understanding DSC Signals (cont.)

Heat Flow (cont.)

Where:= measured heat flow rate

Cp = sample heat capacity= specific heat (J/g°C) x mass (g)

= measured heating rate

f (T,t) = heat flow due to kinetic processes (evaporation, crystallization, etc.)

dtdH

dtdT

Understanding DSC Signals (cont.)

Heat Flow Due to Heat CapacityHeat Capacity = Specific Heat (J/g°C) x mass (g)For a given sample, the higher the heating rate, the higher the heat flow rate. Therefore, high heating rates increase sensitivity to detect weak transitions

Heat Flow Rate = mWatt = mJ/sec

The heat flow rate becomes endothermic as heating of the sample begins (due to sample Cp at that temperature) and becomes more endothermic at higher temperature due to increasing sample Cp at higher temperature During cooling, the heat flow signal is exothermic

Understanding DSC Signals (cont.)

Heat Flow Due to Heat Capacity (cont.)Absolute Heat Capacity or Specific Heat (J/g°C) is important because:

1. It is required by engineers to develop systems that heat or cool materials

2. It is a measure of molecular mobilityVibration – occurs below and above TgRotation – polymer backbone and sidechains (in and above Tg)Translation – polymer molecule (above Tg)

Changes in heat capacity are important because they signal significant changes in the physical properties of a material

Heat Flow Due to Heat Capacity

Tg is a Step Change in Heat Capacity

Heat Flow

Heat Capacity

Temperature Below Tg - lower Cp - lower Volume - lower CTE - higher stiffness - higher viscosity - more brittle - lower enthalpy

Glass Transition is Detectable by DSCBecause of a Step-Change in Heat Capacity

-1.0

-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

[ –––

–– ·

] Hea

t Flo

w (m

W)

0.5

1.0

1.5

2.0

Hea

t Cap

acity

(J/g

/°C

)

70 90 110

Temperature (°C)Exo Up Universal V3.8A TA Instruments

Heat Flow Due to Kinetic Events

Applications

ThermoplasticsThermosetsPharmaceuticalsHeat Capacity Glass TransitionMelting and CrystallizationAdditional Applications Examples

Thermoplastic Polymers

Semi-Crystalline or Amorphous

Crystalline Phasemelting temperature Tm(endothermic peak)

Amorphous Phaseglass transition temperature (Tg)(causing ΔCp)

Tg < TmCrystallizable polymer can crystallize

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

DSC of Thermoplastic Polymers

TgMelting CrystallizationOxidative Induction Time (OIT)

General Recommendations10-15mg in crimped panH-C-H @ 10°C/min

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 Flo

w (W

/g)

[

] Te

mpe

ratu

re (°

C)First Heat Cooling

SecondHeat

Thermoplastic: Heat Flow vs. Temperature for H-C-H

Second HeatFirst Heat

Cool

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5H

eat F

low

(W/g

)

20 60 100 140 180 220 260Temperature (°C)

Quenched PET

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

Calculation of % Crystallinity

For standard samples:

% crystallinity = 100* ΔHm / ΔHlit

For samples with cold crystallization:

% crystallinity = 100* (ΔHm - ΔHc)/ ΔHlit

78.99°C(I)

75.43°C

80.62°C

134.62°C

127.72°C53.39J/g

256.24°C

242.91°C74.71J/g

-1.5

-1.0

-0.5

0.0

0.5

1.0H

eat F

low

(W/g

)

50 100 150 200 250 300Temperature (°C)

PET – Initial Crystallinity

32.2139.5371.74 =−Initial Crystallinity

Crystallinity by DSC

Example: Crystallinity of Polyethylene

%100% ×Δ

Δ= °

f

obsf

HH

ityCrystallin

Q: “Where is my polymer in this table?”

Table: Heats of fusion of 100% crystalline polymers

PET Initial Crystallinity Calculation

78.99°C(I)

75.43°C

80.62°C

134.62°C

127.72°C53.39J/g

256.24°C

242.91°C74.71J/g

-1.5

-1.0

-0.5

0.0

0.5

1.0H

eat F

low

(W/g

)

50 100 150 200 250 300Temperature (°C)

( ) %15140

39.5371.74100 =−×

% crystallinity = 100* (ΔHm - ΔHc)/ ΔHlit

PET % Crystallinity

21J/g Initial Crystallinity or 15% CrystallineDoes that sound right?

The sample is quenched cooled PETWe know that quenched cooled PET is 100% amorphousWhy does DSC give us the wrong answer?

Change in Crystallinity While Heating

105.00蚓275.00蚓

134.63蚓

127.68蚓0.6877J/g 230.06蚓

230.06蚓71.96J/g

0

20

40

60

Inte

gral

(J/g

)

-1.5

-1.0

-0.5

0.0

0.5

1.0

Hea

t Flo

w (W

/g)

-50 0 50 100 150 200 250 300 350

Temperature (蚓 )Exo Up Universal V4.0B TA Instruments

Quenched PET 9.56mg 10°C/min

Crystallization

Crystallization is a kinetic process which can be studied either while cooling or isothermallyDifferences in crystallization temperature or time (at a specific temperature) between samples can affect end-use properties as well as processing conditionsIsothermal crystallization is the most sensitive way to identify differences in crystallization rates

Crystalline Structures

Single Crystals Polymer Spherulites

Sharmistha Datta & David J. W. Grant, Nature Reviews Drug Discovery 3, 42-57 (January 2004)

Physical State Transitions

Glass

Incr

easi

ng T

empe

ratu

re

Liquid

Flexible Thermoplastic

Gum

Rubber

Amorphous Polymer Crystalline Polymer

TgTg

LiquidTm

Crystalline Structures

Spherulite Morphology Folding and “Re-entry”

Youyong Li and William A. Goddard IIIMacromolecules 2002 35 (22), 8440-8455

(from Odian)

Effect of Cooling Rate on Crystallization

當結晶速率太快，或是結晶熱太高時的回溫現象

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

0

50

100

150

200

250

Temperature (°C)

Hea

t Flo

w (m

W)

+-4.36°C

-15.55°C+

Supercooling of Water

Crystallization

•Crystallization is a two step process:NucleationGrowth

The onset temperature is the nucleation (Tn)The peak maximum is the crystallization temperature (Tc)

•Crystallization is Temperature and Time dependence

0.0

0.5

1.0

1.5

2.0H

eat F

low

(W/g

)

40 50 60 70 80 90 100 110 120 130 140 150 160Temperature (蚓 )Exo Up

POLYPROPYLENEWITH NUCLEATING AGENTS

POLYPROPYLENEWITHOUT NUCLEATING AGENTS

-1.5

-1.0

-0.5

0.0

Hea

t Flo

w (W

/g)

60 80 100 120 140 160 180 200Temperature (蚓 )Exo Up

crystallization

melting

Effect of Nucleating Agents

What is Isothermal Hot Crystallization?

• A Time-To-Event ExperimentAnnealing Temperature

Melt Temperature

Isothermal Crystallization Temperature

Time

Zero Time

Isothermal Crystallization

117.4 oC

117.8 oC

118.3 oC

118.8 oC

119.3 oC119.8 oC

120.3 oC

0

1

2

3

4

5

Hea

t Flo

w (m

W)

-1 1 3 5 7 9Time (min)

Polypropylene

降溫速率夠快嗎?Project RHC: Crystallization of LDPE

What is Isothermal Cold Crystallization?

• A Time-To-Event Experiment

Annealing Temperature

Melt Temperature

Isothermal Crystallization Temperature

TimeZero Time

Glass Transition Temperature

Stand-by Temperature

DSC Applications:Quench-Isothermal-Cold Crystallization

Method Log:1: Initial temperature: 高於Tm2: Initial temperature: Tm與Tg之間3: Mark end of cycle 14: Isothermal 恆溫結晶一段時間5: Mark end of cycle 26: Ramp 10.00C/min to高於Tm7: Mark end of cycle 3

DSC Applications: Quench-Isothermal-Cold Crystallization of PET

Isothermal

Ramp 10C/min

以MDSC決定樣品的初始結構

Modulated DSC® Theory & Applications

Advanced Tzero™ technology included in the Q2000, makes MDSCexperiments both faster and the results more accurate. Heating rates equivalent to those commonly used in standard DSC (10°C / min) are now possible. Over

90% of the leading researchers performing MDSC, use systems from TA Instruments - a point to note when choosing a DSC system. * US Patent Nos. B1

5,224,775; 5,248,199; 5,335,993; 5,346,306; 5,439,291

DSC Heat Flow

t)(T,dtdT Cp

dtdH f+=

signalflow heat DSC dtdH

= WeightSample x HeatSpecific Sample

Capacity Heat Sample Cp==

Rate Heating dtdT

=(kinetic) re temperatuabsolutean at

timeoffunction is that flowHeat t)(T, =f

Comparison of DSC and MDSC ® Signals

t)(T, dtdT Cp

dtdH f+=

Kinetic component of total heat flow

Nonreversing Heat Flow

All calculated heat flow signals are also available in heat capacity units

Heat Capacity

Heat capacity component of total heat flow

Reversing Heat Flow

Quantitatively the same in both techniques at the same average heating rate

Total Heat Flow

Signals contain all thermal events occurring in the sample

Modulated Heat Flow

Total Heat Flow

COMMENTSMDSCDSC

Average & Modulated Temperature: Heat-Iso Conditions

Average Temperature

Modulated (Actual)Temperature

Amplitude

Period

Average & Modulated Heating Rate: Heat-Iso Conditions

Period

Note that the rate never decreases below 0ºC/min

MDSC ® Heat-Cool Temperature Modulation

Heating Rate goes below 0ºC/min

Calculation of MDSC ® Signals

Total Heat FlowEquivalent to standard DSC at the same average heating rateCalculated from the average value of the Modulated Heat Flow

The average and amplitude values of the Modulated Heat Flow are calculated continuously (every 0.1 seconds) using Fourier Transform analysis. This provides much better resolution than would be obtained from using the actual average and amplitude values that occur only twice over each modulation cycle.

MDSC ® Raw Signals

Signals have an “Average” and an “Amplitude”

Quenched PET MDSC .424/40@4

Calculation of MDSC ® Total Heat Flow

Quenched PET – 8.99mg

.424/40@4

Calculation of MDSC ® Signals

Reversing Heat FlowCalculated from Reversing Heat Capacity signal

Rev KCp x AmpRate Heating

Flow Amp Heat Cp Rev =

Rate Heat x AvgCp Rev Flow Heat Rev =

Calculation of Reversing Heat Capacity Signal

Rev KCp x AmpRate Heating

Flow Amp Heat Cp Rev =

MDSC ® Reversing Heat Capacity Signal

Reversing Heat Flow and Heat Capacity

Calculation of MDSC ® Signals

Nonreversing Heat FlowCalculated by subtracting the Reversing Heat Flow signal from the Total Heat Flow signal

Total = Reversing + NonreversingNonreversing = Total – Reversing

t)(T, dtdT Cp

dtdH f+=

Total Heat Flow

t)(T,dtdT Cp

dtdH f+=

Reversing Heat Flow

Non-Reversing Heat Flow

•Heat Capacity•Glass Transition•Most Melting

•Enthalpy Recovery•Evaporation•Crystallization•Thermoset Cure•Denaturation•Decomposition•Some Melting

MDSC ® Heat Flow Signals

•All Transitions

Calculated MDSC ® Heat Flow Signals

Quenched PET – 8.99mg

.424/40@4

MDSC ® Applications: True Range of Melting

Estimated Onset of Melting from Standard DSC

MDSC ® Applications: True Range of Melting

Estimated Onset of Melting from Standard DSC

Estimated Onset of Melting from MDSC

The onset of melting is shown to be 65ºC lower than estimated from Standard DSC

Polymers; DSC of Complex Polymer Blend

Where are the glass transitions in this engineering plastic?

Polymers; MDSC of Complex Polymer Blend

Polymers; DSC of PET/PC Mixture

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

[ –––

–– ·

] Hea

t Flo

w (m

W)

-22

-18

-14

-10

-6

-2

Hea

t Flo

w (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

Where is the glass transition of the 100% amorphous polycarbonate?

Polymers; MDSC of PET/PC Blend

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

[ –––

–– ·

] Rev

Hea

t Flo

w (m

W)

-3.2

-3.0

-2.8

-2.6

-2.4

-2.2

-2.0

Hea

t Flo

w (m

W)

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

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

EPOXY ResinTime-Temperature-Transformation (TTT) diagram

Phase Transformations – (Gel and Vitrification)

EPOXY Resin Curing 的過程

Gel 凝膠化 / Vitrification 玻璃化

DSC of Thermosetting Polymers

TgCuring Residual Cure

General Recommendations10-15 mg in crimped pan if solid; hermetic pan if liquidH-C-H @ 10°C/min

R

t

HH

ΔΔ

=α

如何表徵熱固性樣品 : DSC動態升溫法與恆溫法

The degree of cure is defined as follows:

Thermoset: Comparison of 1st & 2nd Runs

0 50 100 150 200 250 300-0.24

-0.20

-0.16

-0.12

-0.08

-0.04

Temperature (蚓 )

Hea

t Flo

w (W

/g)

Tg

Tg

155.93蚓

102.64蚓20.38J/g

Residual Cure

First

Second

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蚓 (H)

DSC Conditions:Heating Rate = 10蚓 /min.Temperature Range = -50蚓 to 250蚓N2 Purge = 50mL/min.

-12.61蚓 (H)

-0.5

0.0

0.5

1.0

1.5

2.0H

eat F

low

(W/g

)

-50 0 50 100 150 200 250

Temperature (蚓 )Exo Up Universal V2.4F TA

Effect of Aging/Storage below Tg

Physical property Response on storage below Tg

Specific Volume DecreasesModulus IncreasesCoefficient of thermal expansion

Decreases

Specific Heat DecreasesEnthalpy DecreasesEntropy DecreasesEnthalpic

RelaxationIncreases

Temperature

V,1/E,

CTECpHS

Storage time

物理老化的影響

(Xiangxu Chen, Shanjun Li,1990)

物理老化對於DSC熱流在Tg範圍產生的影響

Determination of Tg/Cure Factor (Delta Tg)

發生錯誤的判斷

剖析 ΔTg 的爭議革新DSC實驗手法的結果

預熱法可以釐清 ΔTg 的爭議

MDSC® Glass Transition of Epoxy Coating

TOTAL

REVERSING

MDSC® Glass Transition of Solder Mask

MDSC ® Applications: Separating Overlapping Transitions in Epoxy Prepreg

Enthalpy recovery peak due to physical aging

Glass Transition of Epoxy

MDSC ® Applications: Separating Overlapping Transitions in Epoxy Prepreg

Tg is over 3ºC higher in aged sample

Aged EpoxyCycled Epoxy (physical aging removed)

MDSC® of Thermoset Cure While Heating

103.62°C319.8J/g

Total Heat Flow

ReversingHeat Capacity

Increase in Cp Dueto Linear Polymerization

Decrease in Cp Dueto Crosslinking (Vitrification)

Increase in Cp Dueto Devitrification

1.0

1.2

1.4

1.6

1.8

[ –––

–– ·

] Rev

Cp

(J/g

/°C

)

-0.5

0.0

0.5

1.0

1.5

2.0H

eat F

low

(mW

)

50 100 150 200

Temperature (°C)Exo Up Universal V3.8A TA Instruments

Sample: EpoxySize: 9.79 mgMethod: MDSC at 0.5°C/min

Epoxy Cure with Isothermal MDSC®

256.4J/g

50.73min

75.30min

31.06J/g

Iso @ 100°C for 160 min

Temperature

Heating@ 3 °C/min

Residual Cure

Cure Exotherm @ 100°C

Decrease in Cp Due to Crosslinking(Kinetics become Diffusion Controlled)

100

150

200

250

300

350

[ ––

–– –

] Te

mpe

ratu

re (°

C)

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

[ –––

–– ·

] Rev

Cp

(J/g

/°C

)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5H

eat F

low

(mW

)

0 50 100 150 200 250

Time (min)Exo Up Universal V3.8A TA Instruments

Sample: EpoxySize: 10.85 mgMethod: MDSC Iso at 100°C

Polymers; Advantage of MDSC for Post Cure Analysis of Epoxy Resin

Note Onset of Decomositionbefore Complete Cure

Note Inability to Measure Tg

117.14°C31.08J/g

119.12°C(H)0.2810J/g/°C

110.75°C

Total

Reversing

Nonreversing

All Signals atSame Sensitivity

Heating Experiment at 3°C/minafter 160min Isothermal Cure @ 100°C

-0.4

0.0

0.4

[ ––

–– –

] N

onre

v H

eat F

low

(mW

)

-1.2

-0.8

-0.4

0.0

0.4

[ –––

–– ·

] Rev

Hea

t Flo

w (m

W)

-1.4

-1.0

-0.6

-0.2

0.2H

eat F

low

(mW

)

52 102 152 202 252

Temperature (°C)Exo Up Universal V3.8A TA Instruments

Sample: EpoxySize: 10.85 mg

Heating Experiment at 3°C/minAfter 160 min Isothermal Cure at 100° C

Note inability to see Tg in Total (like DSC) signal

Most Common Applications of MDSC; Amorphous Structure

The size (J/g°C) and temperature of the glass transition provide useful information about the amount and physical state of amorphous material in a sample.The glass transition temperature (Tg) is important because the sample undergoes a significant change in physical and reactive properties at this temperatureMeasurement of the glass transition is important to nearly all DSC users. Because of the significant change in properties at Tg, it is often difficult to measure Tg by standard DSC.

Polymers/Drugs; DSC @ 5°C/min for Drug Delivery System Using Polymer Microspheres

Where are the glass transitions of amorphous drug dispersed in amorphous polymer?

Polymers/Drugs; MDSC® @ 2°C/min for Drug Microspheres Shows Polymer/Drug Miscibility

Single Tg seen in Reversing signal indicates Drug is soluble in polymer

Drugs; Use of MDSC to Detect Tg in Drug Formulation

Drugs; MDSC of a Cold/Allergy Tablet Indicates Decomposition, Not Melting

Lack of endothermic peak in the Reversing signal indicates the sample is decomposing and not melting

Drugs; TGA Analysis of Cold/Allergy Tablet Shows Decomposition Between 100 and 150ºC

Selecting MDSC® Experimental Conditions (Pan Type)

Pan Type• Always do TGA experiment to determine volatile

content and decomposition temperature○ Volatilization can hide other transitions○ Volatilization can affect sample properties or even

structure ○ Select pan type (crimped vs. hermetic) based on

volatile content and desire to lose or retain volatiles

• In general, select thinnest, lightest pan possible for the sample/application○ Thin, light pans provide better heat transfer and will

permit shorter modulation periods and faster average heating rates

TGA Data Shows 5% Weight Loss in Drug Monohydrate

It Does Matter What Pan you use

Monohydrate Pharmaceutical

sample

MDSC Shows Increase in Cp During Loss of Water Due to Dehydration of Crystalline Hydrate

Non-Hermetic Pan

Drugs; MDSC Provides Sensitive and Accurate Measurement of Cp for Casein Protein

20.0°C 1.33J/(g°C)

Drugs; MDSC of Albumin Protein Shows Broad Glass Transition and an Endothermic Process at Tg on 1st Heat

Drugs; MDSC of Albumin Protein Shows ShowsJust a Broad Glass Transition on 2nd Heat

Drugs; MDSC® Provides an Accurate Measurement of Tg’ for Freeze-Drying

Enthalpy Plots Are Integrals of Heat Capacity Plots

Figure 1 Drug 3.75mg MDSC® .159/60/1

Integrals of 100% Crystalline and 100% Amorphous Heat Capacity Curves Can Be Used to Create an Enthalpy Plot

Figure 2Effect of the Temperature-Dependence of the Heat of Fusion on Crystallization and Melting

Peak Areas for a Drug

The Enthalpy Plot Can Be Used to Calculate % Crystallinity

Illustrating the Temperature Dependence of the Heat of Fusion on the Monohydrate Form of the DrugFigure 3

Figure 4; % Crystallinity of PET @160 °C

20°C/min

Use of ATHAS Databank to Calculate % Crystallinity on 12.64mg Sample of Quench Cooled PET after Cold Crystallization