Principio de Medida DSC

�

Introduction to DSC Basics

Author: Ni JingReview: Rudolf RiesenDate: Jan 12, 2010

Madrid

Mayo 2012

1 Internal usage only

Agenda

� How does a DSC work?� Temperature and heat flow measurement � Heat flow by a DSC� Schematic diagram of DSC 1

� Where to use a DSC?� Main effects� Industry

� Summary

�

2

1899: W. Roberts-Auston measures the temperature diffe-rence between the sample and an inert reference, thus establishing DTA.

Heater

Brief history of DTA/DSC

1887: Le Chatelier measures the temperature of claysas a function of time.

3

DSC working principle

39 C56 C

�

4

1955: Boersma invents the heat flow DSC-technique

Ingenious idea of Boersma: thermal resistance of theinstrument isindependant of thesample; therefore, theheat flux can bemeasuredquantitatively.

NiCeramic Plate

Lit.: S. L. Boersma, J. Am. Ceramic. Soc., 38, 281 - 284, 1955

Brief history of DTA/DSC

5

(T1+ T2)/2

∆T

cooler

heatercooler

T

P1 T2P2T1

Power compensation DSCHeat flux DSC

Principle of Heat Measurement

�

6

Ice

Ts Tr

Hot Plate

Heat the hot plate from -20 °C to 30 °C,

What will happen to ice?

How do Ts and Tr react?

How do the Ts and Tr relate to each other?

Air

Heat Flow Measurement

7

Timeor Tr

TemperatureTr

Ts

Tf

Time�T =Ts-Tr

0

-0.5

Tf

DSC raw signal


�

8

DSC raw signal,

Timeor Tr

�T =Ts-Tr

0

-0.5

Tf

Timeor Tr

Heat flow (mW)

0

-10DSC signal, Φ

Peak integral �� H

Φ=�

T/Rth

Rth, thermal resistence of thesystem

�H


9

Baseline Slope

Where,

m is the sample masscp is the specific heat capacity

of the sampleβ is the heating rate

Timeor Tr

Heat flow Φ(mW)

0

-10

Initial deflectionΦ

A normal DSC curve is not horizontal, its baseline shows a slope.

�⋅⋅=Φ��

�

10

What does a DSC measure?

Where

m is the sample masscp is the specific heat capacity

of the sampleβ is the heating rate∆∆∆∆Hp is the enthalpy of a process, e.g.

melting, reaction, evaporationis change of conversion per unittime

Φ = mcpβ + ∆HPdαdt

Time

Heat flow Φ(mW)

0

-10

Initial deflection

Φ

∆Hp

sensible heat flow,due to increase oftemperature;no structural change

latent heat flowdue to structuralchanges

Total heat flow,measured

dαdt

11

Typical DSC curve

A typical DSC curve of a semicrystalline polymer:1 initial deflection proportional to the sample’s heat capacity

2 DSC curve with no thermal effect (baseline)

3 glass transition of amorphous fraction

4 cold crystallization

5 melting of the crystalline fraction

6 oxidative degradation in air

12

ICTA and Anti-ICTA

ICTAC (International Confederation for Thermal Analysis and Calorimetry)

Direction of DSC signal

��

��

mW

-20

-10

0

°C120 130 140 150 160 170

��

��

��

��

��

�

�

��

�

��

��

!! !! " #" #" #" # $$ $$ %% %% ! &�' ( ) *! &�' ( ) *! &�' ( ) *! &�' ( ) *+ ! ,.- / 0+ ! ,.- / 0+ ! ,.- / 0+ ! ,.- / 0 11 11 2 32 32 32 3

ICTAendothermic downward,

exothermic upward.

Anti-ICTAendothermic upward,

exothermic downward.

∆Η∆Η∆Η∆Η = -28.45 J/g ∆Η∆Η∆Η∆Η = +28.45 J/g

13

How to measure temperature?

Thermometer or Pt100 measures T

Au-AuPd thermocouple measures ∆T

Gold Gold

Gold/Paladium Au

AuPd Hot

Cold Au

AuCold

Hot

14

Schematic diagram of DSC 1

Furnace lid

Heater

Temperature sensor

DSC sensor

Cooling flange

Purge gas inletDry gas inlet

15

Melting onset and peak temperatures

��

��

��

��

!��

!�

!��

!�

!��

!�

!�

�� " ��# ��

Peaks of melting of indiumPeaks of melting of indiumPeaks of melting of indiumPeaks of melting of indium 10101010....03030303.... 2006 122006 122006 122006 12::::54545454::::44444444

SSSSTATATATARRRReeee SW 9.01 SW 9.01 SW 9.01 SW 9.01DEMO VersionDEMO VersionDEMO VersionDEMO Version

��

��

��

��

��

��

��

!��

!�

!��

!�

!��

!�

!�

�� " ��# ��



��

��

��

��

��

��

��

��

��

��

!��

!�

!��

!�

!��

!�

!�

�� " ��# ��



��

��

��

��

��

��

��

��

��

��

��

��

��

!��

!�

!��

!�

!��

!�

!�

�� " ��# ��



Melting onset is independent of m and ββββ; Peak temperature dependent.

�

16

Dilemma of the DSC sensor design:

• High Rth → high heat flows, large signals

→ high τSignal → far from equilibrium

• Low Rth → low heat flow, small signals

→ low τSignal → close to equilibrium

Cs (and thereby τSignal) is strongly influenced by thechoice of the pan: a light pan decreases Cssignificantely.

τSignal of the sensor can be further decreased by usingHe as purge gas.

DSC sensor design

17

Sensitivity and resolution

� Sensitivity indicates the ability of a DSC to measure very small and weak effects.

� Resolution indicates the ability of a DSC to separate two close-lying effects.

� Sensitivity and resolution are main characteristics of a measurement signal.

��

18

a/b

Resolution

Resolution

How to improve?

19

c/d

Sensitivity

Sensitivity

How to improve?c: peak heightd: noise

��

20

Agenda

� How does a DSC work?� Temperature and heat flow measurement

� Heat flow by a DSC

� Schematic diagram of DSC 1

� Where to use a DSC?� Main effects

� Industry

� Summary

21

Melting

Are there phase transitions which may influence the biological activity of the active pharmaceutical ingredients (API)?

What makes the Lindor irresistible? Hard outer layer and soft inner filling …

Why do the castors on one desk chair work well and break on another?

Is it made from POM (polyoxymethylene) copolymer or PP?

Melting behavior: melting point/range, melting enthalpy

��

22

Melting and crystallization

amorphous crystalline

Crystallization

Melting

23

Melting and crystallization of PP

� Polymers do not have a melting point but a melting range!� Peak temperature (depends on β and m) is used to characterize

the melting peak.

��

24

In: 6.18 mg10 K/min

Integral -193.95 mJ normalized -28.52 Jg -1Onset 156.58 °C

Integral 194.27 mJ normalized 28.57 Jg -1Onset 153.43 °C

mW

-10

0

10

20

°C140 145 150 155 160 165

exoexoexoexo prod 1prod 1prod 1prod 1 13.03.2006 13:58:2913.03.2006 13:58:2913.03.2006 13:58:2913.03.2006 13:58:29

SSSSTATATATARRRReeee SW 9.01 SW 9.01 SW 9.01 SW 9.01MSG2006: MarcoMSG2006: MarcoMSG2006: MarcoMSG2006: Marco

Melting and crystallization of indium

Melting point of pure metal and small organic molecules:onset (independent of heating rate)

25

Curing reactions

At what temperature does the glue get

hard and how long does it take to

function fully?

Do they need winter and summer tires?

What makes them different?

Curing reaction: temperature range, heat of reaction, speed

��

26

Chemical reaction by DSC

� Energy is absorbed or released during a reaction (enthalpy of reaction)� Peak temperature and shape depend on heating rate� Peak area corresponds to enthalpy of reaction and is independent of heating rate

27

Glass transition

Why don’t the lunch box and the cup distort with hot drinks and food?

Glass transition: temperature, step height ∆cp

How much filler is added to the plastic to lower the price?

Why does the CD case “melt” in the hot sun?

��

28

Glass transition

• The glass transition temperature, Tg, is the characteristic temperature at which a liquid supercools during cooling and becomes glassy.

• The mechanical behavior changes from the viscous liquid to solidwithout structural change.

• The materials can be wholly or partially amorphous, e.g. plastics.

Tg

Heating

29

amorphous solid,rigid, brittle

liquid (non polymers)rubber like (polymers)

Glass transition

Glassy state Rubbery stateGlass transition

The glass transition is the cooperative movement of chain segments.

��

30Temperature

Ent

halp

y or

V

olum

e

Tg

Physical aging

Heating (with relaxation)

Cooling

Enthalpyrelaxation

Glass transition: Background

Glassy state Rubbery state

Physical aging and enthalpy relaxation

Heating (no relaxation)

31

Glass transition: Background

Physical aging and enthalpy relaxation

�

32

� Glass transition temperature, Tg [K] ≈ 2/3 Tmelt [K]PET example: Tmelt = 256 °C = 529 K� Tg ≈ 353 K = 80 °C

� Glass transition is a kinetic phenomenon. The Tg depends on the cooling rate (β) and the measurement and evaluation procedures.

|β1|> |β2| �� Tg (β1) > Tg (β1)

� Very often an enthalpy relaxation peak is observed. Enthalpy relaxation depends on the history of the sample. Long physical aging below Tg

leads to more pronounced enthalpy relaxation

Glass transition: Remarks

To report glass transition temperatures, one should always state the measurement conditions.

UserCom 10: The glass transition; Part 1: basic principlesUserCom 11: The glass transition; Part 2; information for the characterizationUserCom 17: The glass transition temperature measured with different TA techniques; Part 1UserCom 18: The glass transition temperature measured with different TA techniques; Part 2

33

Tg, Cristallization and Melting

Differential Scanning Calorimetry (DSC) allows you to determine the energy absorbed or released by a sample as it is heated or cooled.

The frozen lake of Sihlsee

Signal curves and mass units:

�

34

Effects and industries

Industries

Pol

ymer

s (T

herm

opla

stic

s,

Ther

mo

sets

and

Ela

stom

ers)

Pet

roch

emic

als

Che

mic

al

Pha

rmac

eutic

als

Aut

omot

ive

Mic

roel

ectr

oni

cs

Food

Co

smet

ics

Aca

dem

ia/S

cien

ce

Physical properties

Melting/crystallization X x X X X X X X

Glass transition X X X X X

Enthalpy of melting; content X x x x X X X x

Vaporization, drying x X X X x x

Sorption and desorption x X X x

Specific heat capacity X X x X

Polymorphism, crystalline transitions X X X x X

Solid fat index X x

Purity determination, phase diagram X X

Liquid-crystalline transitions x X X X

35

Effects and industries

Industries

Pol

ymer

s (T

herm

opla

stic

s,

Ther

mo

sets

and

Ela

stom

ers)

Pet

roch

emic

als

Che

mic

al

Pha

rmac

eutic

als

Aut

omot

ive

Mic

roel

ectr

onic

s

Food

Cos

met

ics

Aca

dem

ia/S

cien

ce

Chemical changes

Decomposition, pyrolysis X x x X X x

Curing, vulcanization, vitrification X X X x

Reaction process, enthalpy, kinetics X X X X X X

Oxidation, stability X X X X x x x

Dehydration X X X x

Denaturation x X x x

X : Main applicationsx : Secondary applications

��

36

Summary

� Differential scanning calorimeter (DSC) measures the difference between the heat flows from the sample and reference sides on a sensor as a function of temperature or time.

� A heat flow arises when a sample absorbs or releases heat due tothermal effects such as melting, crystallization, chemical reactions, polymorphic transitions, vaporization and many other processes.

� Specific heat capacities and changes in heat capacity, for example during a glass transition, can also be determined from the difference in heat flow.

37

Summary

� Sensitivity and resolution are main performance characteristics of a DSC. High sensitivity allows weak effects to be detected and the use of small sample size; good resolution allows close-lying effects to be separated.

� DSC is used to analyze and study polymers such as thermoplastics, thermosets, elastomers and adhesives, foodstuffs, pharmaceuticals, chemicals and composite materials.

��

Thank You

Documents

Principio de Medida DSC