Download - 2004 Training Seminars Interpreting Data
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2004 Training Seminars
DSC
3
Interpreting DSC Data
Glass Transition & Melting
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Glass Transitions
The glass transition is a step change inmolecular mobility (in the amorphous phase of
a sample) that results in a step change in heat
capacity
The material is rigid below the glass transitiontemperature and rubbery above it. morphousmaterials flow! they do not melt (no "#$ melt
pea%)
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Glass Transitions
The change in heat capacity at the glasstransition is a measure of the amount of
amorphous phase in the sample
nthalpic recovery at the glass transition is a
measure of order in the amorphous phase.nnealing or storage at temperatures 'ust
below Tg permit development of order as the
sample moves towards euilibrium
l i
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Heat Flow & Heat Capacity at
the Glass Transition
eat *low
eat $apacity
Temperature +elow Tg, lower $p, lower -olume, lower $T&, higher stiffness, higher viscosity
, more brittle, lower enthalpy
Glass Transition is "etectable by "#$+ecause of a #tep,$hange in eat $apacity
,./
,/.0
,/.1
,/.2
,/.
,/.4
,/.5
,/.3
67777789eat*low
(m:)
/.4
./
.4
;./
eat$apacity($)
2/ 0/ /
Temperature (>$)
&o Hp Hniversal -3.1 T Instruments
Polystyrene
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Measuring!eporting Glass Transitions
" The glass transition is always a temperature range
" The molecular motion associate# with the glasstransition is time #epen#ent$ There%ore Tg increases
when heating rate increases or test %re'uency (MDSC)
DM* D+* etc$, increases$
" -hen reporting Tg it is necessary to state the test
metho# (DSC DM* etc$, e.perimental con#itions
(heating rate sample si/e etc$, an# how Tg was
#etermine# Mi#point 1ase# on Cp or in%lection (pea3 in #eriatie,
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Glass Transition *nalysis
Polystyrene
5$67mg
809Cmin
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Glass Transition *nalysis
Polystyrene
5$67mg
809Cmin
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Step Change in Cp at the Glass Transition
: *morphous ; 0$84
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Aged Epoxy Sample
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Effect of Annealing Time on Shape of Tg
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Importance of Enthalpic Relaxation
Is enthalpic recovery at the glass transition important?
>Sometimes" Glass transition temperature shape an# si/e proi#e use%ul
in%ormation a1out the structure o% the amorphous component
o% the sample$" This structure an# how it changes with time is o%ten
important to the processing storage an# en#?use o% a
material$" +nthalpic recoery #ata can 1e use# to measure an# pre#ict
changes in structure an# other physical properties with time$
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+%%ect o% *ging on *morphous Materials
Temperature
Max TgStorage
timeH
MS
+'uili1rium
@i'ui#
+'uili1rium
Glass
Aau/mannTempB @owest Tg
(+ntropy o% Crystal,
-here H ; High relatie cooling rate
M ; Me#ium relatie cooling rat
S ; Slow relatie cooling rate
Decreases+ntropy
Decreases+nthalpy
DecreasesHeat Capacity
DecreasesCoe%%icient o%+.pansion
ncreasesMo#ulus
DecreasesSpeci%ic olume
!esponse on
S
Physical Property
+ntropy
+nthalpy
Coe%%icient o%
Mo#ulus
Speci%ic olume
!esponse on
Storage Eelow Tg
Physical Property
!
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Suggestions %or Fin#ing -ea3
Glass Transitions" Anow your empty?pan 1aseline
" Get as much material in the amorphous state
" Cool slowly through the glass transition
region
" Heat rapi#ly through glass transition region
" se MDSC)
" r use uasi?sothermal MDSC
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Glass Transition Summary
" The glass transition is #ue to *morphous
material
" The glass transition is the reersi1le change
%rom a glassy to ru11ery state & ice?ersa
" DSC #etects glass transitions 1y a step
change in Cp
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Melting De%initions
" Melting the process o% conerting crystalline
structure to a li'ui# amorphous structure
" Thermo#ynamic Melting Temperature the
temperature where a crystal woul# melt i% it ha# a
per%ect structure (large crystal with no #e%ects,
" Metasta1le Crystals Crystals that melt at lower
temperature #ue to small si/e (high sur%ace area, an#poor 'uality (large num1er o% #e%ects,
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De%initions (cont$," Crystal Per%ection the process o% small less per%ect
crystals (metasta1le, melting at a temperature 1elowtheir thermo#ynamic melting point an# then (re,
crystalli/ing into larger more per%ect crystals that
will melt again at a higher temperature
" True Heat Capacity Easeline
o%ten calle# thethermo#ynamic 1aseline it is the measure# 1aseline
(usually in heat %low rate units o% m-, with all
crystalli/ation an# melting remoe#>$ assumes no
inter%erence %rom other latent heat such as
polymeri/ation cure eaporation etc$ oer the
crystalli/ationmelting range
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Melting o% n#ium
42./>$
4./>$;1.4/$=min
,;4
,;/
,4
,/
,4
/
eat*low(m
:)
4/ 44 / 4
Temperature (>$)
&Go Hp Hniversal -5./+ T Instruments
@ea% Temperature
trapolated
Jnset
Temperature
eat of
*usion
*or pure! low
molecular weight
materials (mwK4//
g=mol) usetrapolated Jnset as
Melting Temperature
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Melting o% P+T
;50.2/>$
;3.4>$4;.0$=min
,2
,
,4
,5
,3
,;
,
eat*low(m:)
;// ;/ ;;/ ;3/ ;5/ ;4/ ;/ ;2/
Temperature (>$)
&Go Hp Hniversal -5./+ T Instruments
trapolated
Jnset
Temperature
@ea% Temperature
eat of
*usion
*or polymers! use @ea% as Melting Temperature
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Comparison o% Melting
;50.2/>$
;3.4>$4;.0$
4./>$;1.4/$=min
@&T.20mg/>$=min
,;4
,;/
,4
,/
,4
/
eat*low(m:)
5/ / 1/ ;// ;;/ ;5/ ;/ ;1/
Temperature (>$)&Go Hp Hniversal -5./+ T Instruments
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*naly/ingnterpreting !esults
" t is o%ten #i%%icult to select limits %orintegrating melting pea3s
ntegration shoul# occur 1etween two points on
the heat capacity 1aseline
Heat capacity 1aselines %or #i%%icult samples can
usually 1e #etermine# 1y MDSC)or 1y
comparing e.periments per%orme# at #i%%erent
heating ratesSharp melting pea3s that hae a large shi%t in the
heat capacity 1aseline can 1e integrate# with a
sigmoi#al 1aseline
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Easeline Due to Cp
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Easeline Type
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"SC of #olymer $lend
-here is theCp 1aselineI
More on this sample in
the MDSC) section
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s it a meltI
J+SK
nset shi%ts 1y only 0$=9C
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s it a MeltI
LK
nset shi%ts 1y almost =09C
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+%%ect o% Heating !ate on Melting
/>$=min
4/>$=min
//>$=min
4/>$=min
/
;
5
1
/
eat$apacity($)
,5/ / 5/ 1/ ;/ / ;// ;5/ ;1/Temperature (>$)
Melt
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+%%ect o% Heating !ate on Polymorph
"#$ at $=min
"#$ at /$=min
"#$ at 4/$=min
"#$ at $=min
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+%%ect o% mpurities on Melting
ffect of p,minobenAoic cid Impurity $oncentration
on the Melting #hape=Temperature of @henacetin
ppro. mg
$rimped l @ans
;>$=min
L+# 45
Thermal nalysis@urity #et
Melting of
utectic Miture
// @ure
04./ @ure
00.3 @ure
0./ @ure
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ant Ho%% Purity Calculation
33./
33.4
35./
35.4
34./
Temperatur
e(>$)
,; / ; 5 1 /
Total rea = @artial rea
;4.;/>$32.24>$
@urity? 00.43mol Melting @oint? 35.0;>$ (determined)"epression? /.;4>$"elta ? ;.44%$NM# "eviation? /./>$
,;.;
,;./
,.1
,.
,.5
,.;
,./
,/.1
eat*low(:=g)
;; ;5 ; ;1 3/ 3; 35 3 31
Temperature (>$)&Go Hp
5
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2004 Training Seminars
DSC
5
Interpreting DSC Data
$rystalliAation! eat $apacity!
and $rosslin%ing
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CrystallinityDe%initions
" Crystalli/ation the process o% conerting eithersoli# amorphous structure (col# crystalli/ation on
heating, or li'ui# amorphous structure (cooling, to a
more organi/e# soli# crystalline structure
" Crystal Per%ection the process o% small less per%ect
crystals (metasta1le, melting at a temperature 1elow
their thermo#ynamic melting point an# then (re,
crystalli/ing into larger more per%ect crystals thatwill melt again at a higher temperature
"
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Change in Crystallinity -hile Heating
/4.//>$;24.//>$
35.3>$
;2.1>$/.122$
;3/./>$
2.0$)
&Go Hp Hniversal -5./+ T Instruments
Ouenched @T
0.4mg
/>$=min
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Crystalli/ation
" Crystalli/ation is a 3inetic process which can 1e
stu#ie# either while cooling or isothermally
" Di%%erences in crystalli/ation temperature or time(at a speci%ic temperature, 1etween samples can
a%%ect en#?use properties as well as processing
con#itions
" sothermal crystalli/ation is the most sensitie wayto i#enti%y #i%%erences in crystalli/ation rates
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Crystalli%ation
" Crystalli/ation is a two step processN
LucleationGrowth
" The onset temperature is the nucleation (Tn,
" The pea3 ma.imum is the crystalli/ation
temperature (Tc,
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/./
/.4
./
.4
;./
eat*lo
w(:=g)
5/ 4/ / 2/ 1/ 0/ // / ;/ 3/ 5/ 4/ /
Temperature (>$)&Go Hp
P@JP!PJ@+L+-TH LC@+*TLG
*G+LTS
P@JP!PJ@+L+-THT
LC@+*TLG *G+LTS
,.4
,./
,/.4
/./
eat*low(:=g)
/ 1/ // ;/ 5/ / 1/ ;//
Temperature (>$)&o Hp
crystalli%ation
melting
+%%ect o% Lucleating *gents
-h i h l C lli i I
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-hat is sothermal Crystalli/ationI
" * Time?To?+ent +.periment
*nnealing Temperature
Melt Temperature
sothermal Crystalli/ation
Temperature
Tem
perature
Time
Oero Time
h l C lli i
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sothermal Crystalli/ation
117.4 oC
117.8 oC
118.3 oC
118.8 oC
119.3 oC
119.8 oC120.3 oC
0
1
2
3
4
5
HeatFlow
(mW
!1 1 3 5 7 9
"ime (min
@olypropylene
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Speci%ic Heat Capacity (Cp,
" Heat capacity is the amount o% heat re'uire# to
raise the temperature o% a material 1y 89C %rom T8
to T2
" True Heat Capacity (no transition, is completely
reersi1leB the material releases the same amount
o% heat as temperature is lowere# %rom T2to T8
"Speci%ic Heat Capacity re%ers to a speci%ic massan# temperature change %or a material (g9C,
-h i H C i I
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-hy is Heat Capacity mportantI
" *1solute thermo#ynamic property (s$ heat
%low, use# 1y engineers in the #esign o%
processing e'uipment
" Measure o% molecular mo1ility Cp increases as molecular mo1ility increases$
*morphous structure is more mo1ile than crystalline
structure
" Proi#es use%ul in%ormation a1out the
physical properties o% a material as a %unction
o% temperature
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Does DSC Measure Heat CapacityI
" DSC or MDSC) #o not measure heat
capacity #irectly$ They measure heat %low ratewhich can 1e use# to calculate heat capacity
which is more appropriately calle# apparent
heat capacity DSC calculate# Cp signals inclu#e all transitions 1ecause
the heat %low signal is simply #ii#e# 1y heating rate (an
e.perimental constant, to conert it to heat capacity units
* true alue o% Cp can only 1e o1taine# in temperatureregions where there are no transitions
C l l i H C i (C ,
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Calculating Heat Capacity (Cp,
" Depen#ing on the DSC that you hae there
are three #i%%erent ways to calculate Cp8, Three !un Metho# *STM +8265
*pplica1le to all DSCQs
2, Direct Cp Single !un Metho# *pplica1le to 8000 only
=, MDSC) ? Single !un Metho#
*ny T* nstruments DSC w MDSC option
Most accurate #etermination
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Cp 1y Stan#ar# DSC
" Generally three e.periments are run in aDSC oer a speci%ic temperature range
+mpty pan run
Sapphire run
Sample run
C l l ti C 1 St # # DSC
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Calculating Cp 1y Stan#ar# DSC
" Three e.periments are run oer a speci%ic
temperature range *llow < minute isothermal at start se 209Cmin heating rate
8$ +mpty pan run Match panli# weights to R 0$0< mg
se# to esta1lish a re%erence 1aseline
Calculating Cp 1y Stan#ar# DSC
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Calculating Cp 1y Stan#ar# DSC
2$ Sapphire run
se# to #etermine cali1ration constant se same weight o% panli# as %or 1aseline R
0$0< mg
Typical weight is 20 2< mg
=$ Sample run Typical weight is 80 8< mg
se same weight o% panli# as 1e%ore R 0$0< mg
C 1 T #iti l DSC = !
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Cp 1y Tra#itional DSC = !uns
,//
/
//
;//
3//
5//
Temperature
(>$)
,3/
,;4
,;/
,4
,/
,4
/
4
eat*low(m:)
/ / ;/ 3/ 5/
Time (min)
eat *low
+aseline Nun
#ample Nun
$alibration Nun
1 #i i l
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Cp 1y Tra#itional DSC = !uns
/
//
;//
3//
5//
4//
Totaleat($)
4/.// >$. $
4/.// >$./0 $
;1/.// >$.0;5 $
;1/.// >$
545. $25. $35.05
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Speci%ic Heat Capacity
" MDSC) & T/ero DSC hae the a1ility
to calculate a heat capacity signal #irectly
%rom a single run$
" Eene%its o% using a heat capacity (instea# o%heat %low, signal inclu#eNThe a1ility to oerlay signals %rom samples run
at #i%%erent heating ratesThe a1ility to oerlay signals %rom heating an#
cooling e.periments
Direct Cp %rom a 8000
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Direct Cp %rom a 8000
;24.//>$43/.1$
/.23$)
/ 4/ // 4/ ;// ;4/ 3//
Temperature (>$)
Hniversal -3.1 T Instruments
Fatent eat of
Melting is Lot eat
$apacity
Fatent eat of
$rystalliAation is Lot
eat $apacity
bsolute integral
calculates total heat
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Heat Flow w Di%%erent Heating !ates
Heat Flow Signal# In$rea#e in Si%e
wit& In$rea#ing Heating 'ate
E %it % Pl tti H t C it
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Eene%it o% Plotting Heat Capacity
Nemember! "#$ and M"#$
$p signals are really
Apparent Cp signals;
crystalliAation and melting
are latent heats! not $p
eat $apacity #ignals reLormaliAed for eating Nate and
@ermit $omparison of periments
"one at "ifferent eating Nates
H t Fl & C Si l
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Heat Flow & Cp Signals
PolypropyleneSi/eN 5$28 mg
DSC Cycle 80#egCmin
Heat Capacity on Heating
Heat Capacity on Cooling
Heat Flow on Heating
Heat Flow on Cooling
-ea3 Tg isi1le in Cp Signal
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-ea3 Tg isi1le in Cp Signal
SampleN Polypropylene
Si/eN 5$28 mg
DSC Cycle 80Cmin
Heat Capacity on Heating
Heat Capacity on Cooling
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Thermoset Curing & !esi#ual
Cure" * UthermosetV is a cross?lin3e# polymer
%orme# 1y an irreersi1le e.othermic
chemical reaction* common e.ample woul# 1e a 2 part epo.y
a#hesie
" -ith a DSC we can loo3 at the curing o%these materials an# the Tg o% %ull or
partially cure# samples
Curing o% a Thermoset
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Curing o% a Thermoset
34.;>$
01.34>$;41.3$=min to 0/ >$
5
1
/
;
eat*low
(m:)
5/ / 1/ // ;/ 5/ / 1/ ;//
Temperature (>$)
# ti ll C d S t
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#artially Cured System
;ndheat shows increased
Tg! due to additional
curing during st heat
Lote? #mall eotherm due to residual cure
Ph l C 1 PC*
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Photopolymer Cure 1y PC*
./1min
./min;/0.$;? Isothermal for .// min3? Fight? on B ;/m:=cm;5? Isothermal for 4.// min4? Fight? off? Isothermal for ;.// min2? &nd of method
$ure of a @hotopolymer by @$
/
4/
//
4/
;//
;4/
eat*low
(m:)
/ ; 5 1
Time (min)
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