Dynamic Mechanical Analyzer
EC-Twist
1
Rheology Road
Rheology describes the flow and deformation behaviour
2
Polymer Characterization
3 Groups
Poly(many)Mer(many) 103 – 106
Thermo-Melts
 Linear or branched
 Start melting above melting temperature
Elastomers
 Sparsely linked
 Do not melt at higher temperatures
Thermo-Sets
 Densely linked
 2K adhesives, epoxy resin based materials
 Do not melt at higher temperatures
 Mechanical properties almost independent from
temperature
3
EC-Twist
Dynamic Mechanical Analyzer
Melts
Material
characterization
DMTA
Sealants,
Adhesives
Mechanical
properties
Elastomers
4
Time, temperature, frequency
http://www.anton-paar.com/DE/de/Web/Document/download/11158?clng=en
Curing
EC-Twist
Melt rheology in tensile mode
MELT
RHEOLOGY
UXF, SER
STEP RATE TEST
Extensional viscosity
Branching
5
Extensional
viscosity
Extensional viscosity
Measurements with UXF or SER
 Setting: constant tensile rate
Setting

E 
 tensile stress

[Pas]

tensile rate
Zeit t
Measurement until strain hardening or melt fracture
Extensional
viscosity E
1.0s-1
0.1s-1
time t
6
slope is a
qualitative measure for
the degree of cross
linkage or branching of
polymer melts or
elastomers
EC-Twist
Melt rheology in shear mode
MELT
RHEOLOGY
Shear-rheology
PP25 (PP35), CP25-3/TG
(CP35-3/TG)
FLOW CURVE,
FREQUENCY SWEEP
 Zero shear viscosity




Relaxation time
Power law exponent
Deborah number
Master Curve
 Mw, MMD (relative)
7
.
g
Viscosity Curve
Orientation and relaxation
 Shear thinning due to orientation,
which results in lower viscosities
 Polymer melts or highly concentrated solutions
entangled

orientation time
relaxation
shear
.
g
disentangled
8
Viscosity Curve, Composites
Finding structures...
 Lower shear rates: more sensitive to interacting forces
 High shear rates: orientation of structures
High concentration of filler

Low concentration of filler
.
g
9
Viscosity Curve, Composites
Finding structures...
 By regression the viscosity for any
concentration can be found -> can be done by
copying viscosity values into Excel
Particle-Particle interactions ->
Friction due to high
concentration

Particles are “free” to move
within the matrix liquid
5% 10%
20%
cv
Solid-volume concentration Cv [%]
10
Viscosity Curve – Carreau-Yasuda Regression
What‘s the meaning of the 3 ranges?
0 Zero shear viscosity = proportional to molar mass
n
Power law exponent = qualitative measure for the macro molecules to orient
in shear direction und to reduce flow resistance
a
l
Width of transition range = proportional to MMD and PDI
-> narrow MMD=steep, broad MMD=flat)
Relaxation time = time dependent recovery of internal stresses
De Deborah Number
De 
*
11
Relaxat ionT ime
 l  g
P rocessingT ime
Rule of thumb for processing
Make sure that De value is as low as
possible
w
Solving Processing Issues
Too much elasticity and relaxation issues
Unwanted side effects due to long relaxation times
and high shear processing speeds
 Die swell
 after leaving the nozzle
 Melt fracture
 limited processing speed
 Sharkskin
 often found with LLDPE and HDPE
 Strategy:
 Processing additives (e.g. PPA) => reduced risk of melt fracture during extrusion
 Modification of MMD => lower storage modulus G‘ at higher frequencies (shifted cross over
towards higher frequencies) or lower N1 at higher shear rates
 Deborah-Number De = processing shear rate (smallest diameter) * relaxation time
12
Frequency Sweep
Visco-elastic liquid (no gel, unlinked, no filler)
 Long term: newtonian behaviour
 Short term: viscoelastic behaviour
 No network
structure
 No links between
macro-molecules
Complex viscosity
G‘‘ G‘
1
2
1
1
13
Angular frequency w
Frequency Sweep
Visco-elastic, partially linked
 No long term relaxation
 Gel stability due to 3D-network structure
G‘
G‘‘
Slope:
 Strength of structure
at rest
Absolute value:
 Stiffness of gel
Complex viscosity
Angular frequency w
14
Damping G‘‘/G‘
 Damping behaviour
Flow Curve with N1 (Polycarbonate)
1. Normal Stress Difference N1 causes flow phenomena
 1st normal stress difference
 causing: melt fracture and die swell effects
 edge effects at higher shear rates
-> therefore only limited chance to measure these samples !
 NOTE: If N1 > t, then measuring data is no longer stable
10.000
100.000
Pa
10.000

Pa·s
1.000
t
N1
100
1.000
0,01
10
0,1
1
.
Scherrate g
15
1/s
10
Frequency Sweep – Master Curve
Time Temperature Superposition
Background:
 Due to increasing T the relaxation times are getting shorter
 Shift factor aT=l(T)/l(Tref) or based on viscosity aT=(T)/(Tref)
 Frequency sweeps (FS) measured at various T can be shifted horizontally
 Only applicable for unlinked and unfilled polymers
 Each FS measured at T can be shifted by aT to the so called reference temperature T0
(+) Enlarged frequency range
(+) Information about practically relevant shear rates up to 100.000s-1
(+) Determination of the zero shear viscosity
16
Frequency Sweep – Master Curve
Horizontal shift towards the reference temperature T0
 TTS example: horizontal shift of storage modulus G‘
Storage modulus G‘
160°C
180°C
200°C
230°C
260°C
Angular frequency w
17
Frequency Sweep – Master Curve
Horizontal shift towards the reference temperature T0
 TTS example: shift of storage modulus G‘
 The range abover the transition region is called glassy region
18
Frequency Sweep – Master Curve
Workbook assistant and loop temperature
 The FS is executed 1x for each of the Loop-T defined in the
list:
e.g. T0=190°C
 The first Loop-T in the list must be the reference temperature T0
 Temperature in the “Start Dialog” is automatically replaced by the
next T from the list
 A macro ‘@consttemp@ in
the data series name ensures
that the Loop-T is part of the
data series name
 Optimized settings for CTD or ETD ensure perfect temperature
equilibration
19
Frequency Sweep – Master Curve
Specific settings of the analysis method
 Shift is done automatically
 Target temperature is entered which is equal to the reference T0
 In the case of any issue with auto calculation the parameters must be defined
manually
 The following settings may solve the issues with unsteady or badly
overlapping measuring data:
 Range = valid range of deviation (will stop analysis if exceeded for a single
point of the shifted curve
 Shift horizontal OR hirizontal and vertical (vertical = correction of density)
 Scattering at lower frequencies -> increase value for lower points
 Scattering at higher frequencies -> increase value for higher points
 The reduced range is only used for shifting the curves; all points are included
in the resulting master curve at T0
20
Frequency Sweep – Master Curve
Further analysis – Activation Energy
 WLF (amorphous polymers T>/=Tg) and Arrhenius (partially
crystalline polymers T>>Tg) allowing a regression of
 shift factors against temperature
 E  1 1 
Arrhenius mit T0=160°C
a T  exp 0    
 R G  T T0 
1
[Arrhenius]
0,1
aT
a = 0,99886; b = 1.543,3; c = -325,29; x0 = 159,99 °C
aT
0,01
Horizontaler Verschiebungsfaktor
[WLF]
0,001
200
°C
a = -14,361; b = 108,38; x0 = 159,99 °C
250
aT
Horizontaler Verschiebungsfaktor
 calculated activation energy E0 = 12,831 kJ/mol
 Gas constant RG = 8.314*10-3 kJ/(mol*K)
 E0 is calculated from E0 = RG * b
 Flow activation energy describes E0 the amount of energy needed to move the molecules at a
certain temperature T0
 Based on WLF or Arrhenius regression a FS at any temperature of the curve can be calculated
21
EC-Twist
DMTA in torsion and extension
DMTA TORSION &
EXTENSION
SRF
Trange, 1Hz
g  0.01-0.1%
G‘, G‘‘, tan()
Size: 40mm, 1mm-2mm, 10mm
UXF
Trange, 1Hz
sRotation = 2MPa-0,4MPa
sOscillation = 1MPa-0,2MPa (50%)
E‘, E‘‘, tan()
Size: 20mm, 0.05mm, 5mm
22
DMTA
Tension
DMTA
Torsion
DSC: Thermal Analysis
Detection of Tg
DSC
Power Compensated
DSC
Theater = constant
Power = measured
Heat Flux
DSC
Tdisk = const.
Tsample = measured
Treference = measured
sample
reference
Thermo
couple
heater
heater
sample chamber
sample
reference
Constant heating disk
Thermo
couple
23
Differential
Scanning
Calorimetry
DMTA in Torsion
Benefits compared to alternative methods
 Separate pretension and compensation of thermal
expansion by the stepper motor
 Oscillatory signal measured by the EC motor, without
superposition of a pretension force
 Optimal measuring signal, especially in borderline
areas – the extremely low temperatures below the glass
temperature (below Tg) and the high temperatures close to
the melting point
Benefits:
 Most sensitive method
 Best signal to noise ratio
 Most sensitive thermal technique for Tg
 Widest temperature range
Application:
 Enables a practically relevant dynamic load
 Measurement of the true thermo-mechanical behavior
24
Elasticity law
DMTA in Torsion
DMTA in Tension
Shear Modulus
Tensile Modulus
G
*
tˆ shear st ress
 
gˆ shear st rain
E*
sˆ tensilestress


ˆ tensilestrain
Sir Robert
Hooke
1635-1703
Conversion
2
G* 
E *  1  m 
25
* with Poisson's ratio m [1]
E *  2  G * 1 m
Poisson’s Ratio m:
Rubber: 0.5
Thermo-melts: 0.35 ... 0.45
Poisson’s ratio µ
Rule of thumb:
• For most isotropic polymers the Young’s modulus E is about 2.85 time higher than the
shear modulus G
• This complies to a Poisson’s ration of 0.43
Poisson’s Ratio m:
26
Rubber: 0.5
Polymers - isotropic
Poisson‘s
ration
E=x*G
PS
0.38
x = 2.76
PMMA
0.40
x = 2.8
PC, PPS, PVC-rigid
0.42
x = 2.84
PP, PET
0.43
x = 2.86
PTFE, PA66
0.46
x = 2.92
HDPE
0.47
x = 2.94
LDPE
0.49
x = 2.98
* with Poisson's ratio m [1]
Thermo-melts: 0.43
DMTA in torsion versus tension
+ DMTA in torsion is more sensitive than DMTA in tension
+ DMTA in torsion is more sensitive than DSC and delivers mechanical properties
+ DMTA torsion: Separate motor for measuring and pre-tension
DMTA TEST
10,000
EC-Twist301
MPa
1,000
G'
G'
Storage Modulus
G''
Loss Modulus
100
Myrenne Torsional Pendulum
G''
10
1
Storage Modulus
G''
Loss Modulus
Typical
DMTA in tension from competitor
Q800 TA-Inst
with conversion G‘=E‘/3, G‘‘=E‘‘/3:
0.1
-150 -100 -50
0
Temperature T
50
°C
Anton Paar GmbH
27
G'
150
G'
Storage Modulus
G''
Loss Modulus
DMTA
How about our performance?
DMA in tension (data from competition):
-> issue if material becomes soft
-> due to superimposed pre-tension and measuring signal
DMTA TEST
10,000
EC-Twist301
MPa
1,000
G'
G'
Storage Modulus
G''
Loss Modulus
100
Myrenne Torsional Pendulum
G''
10
130 140 150 160
Temperature T
170
Anton Paar GmbH
28
Storage Modulus
G''
Loss Modulus
Typical DMTA in tension from competitor
Q800 TA-Inst
with conversion G‘=E‘/3, G‘‘=E‘‘/3:
1
0.1
120
G'
°C
190
G'
Storage Modulus
G''
Loss Modulus
DMTA
How about our performance?
-> Tg at Peak tan(delta) delivers the same result
Tg at Peak tan(delta)
3
2.5
EC-Twist301
tan( )
2
Damping Factor
Myrenne Torsional Pendulum
tan( )
1.5
tan( )
Typical DMTA in tension from competitor
with conversion G‘=E‘/3, G‘‘=E‘‘/3:
1
Q800 TA-Inst
tan( )
0.5
0
100
120
140
Temperature T
°C
160
Anton Paar GmbH
29
Damping Factor
Damping Factor
DMTA: Thermo-Melt
Glassy, rubber-elastic, melt
SRF
typical:
1 MPa
3000 MPa
glassy
rubberelastic
100 Pa
melt
G‘
tan()
G“
glasstransition
T
30
 Strain 0.01-0.1%
 Frequency 1Hz
 NF = 0 N
 MS: SRF12
 (40x10x1)mm
DMTA: Amorphous Thermo-Melt
Glassy, rubber-elastic
Amorphous
typical:
glastransition
G‘
or
E‘
1 MPa
3000 MPa
100 Pa
quasi
rubber
elastic
use
temperature
flow region
energy elastic
entropy elastic
T
31
random order
SRF
 Def. 0.01%-0.1%
 Frequency 1Hz
 NF = 0 N
 MS: SRF12
 (40x10x1)mm
Melt:
 CP25-2/TG
CP35-3/TG
PP25, PP35
DMTA: Partially Crystalline Thermo-Melt
Glassy, rubber-elastic
Partially crystalline
typical:
1000 MPa
3000 MPa
G‘
oder
E‘
glass
transition
100 Pa
melting
region
use
temperature
flow
region
energy elastic
T
32
crystalline regions
SRF
 Def. 0.01%-0.1%
 Frequency 1Hz
 NF = 0 N
 MS: SRF12
 (40x10x1)mm
DMTA: Elastomer or Rubber
Glassy, rubber elastic
typical:
1000 MPa
0.1MPa...100MPa
permanent links
G‘
glass
transition
E‘
degradation
rubber
elastic
oder
use
temperature
energy elastic
entropy elastic
T
33
SRF
 Strain 0.01%
 Frequency 1Hz
 NF = 0 N
 MS: SRF12
 (40x10x1)mm
DMTA: Thermo-Plastic Elastomer (TPE)
Glassy, rubber elastic
+ thermo-melt
typical:
1000 MPa
G‘
0.1MPa...100MPa
+ synthetic rubber
glass
transition
rubber
elastic
oder
E‘
or:
flow
region
use
temperature
thermo forming
energy elastic
entropy elastic
T
34
crystalline
block-copolymere
DMTA: Thermosetting Plastics
typical:
3000 MPa
permanent links
G‘
degradation
oder
SRF
 Def. 0.01%-0.1%
 Frequency 1Hz
 NF = 0 N
 MS: SRF12
 (40x10x1)mm
E‘
use
temperature
energy elastic
T
35
DMTA - How to determine Tg
Tg according to DMA-Method: Peak tan()
1. Some years ago G‘ or E‘ could not be measured in the glassy state
2. The measurement of the damping factor  was quite accurate
3. Historically the Tg was calculated as the maximum in tan()
All DMA analyzers are getting the same results for Peak tan() but vary in absolute
measurements for E‘, E‘‘ or G‘, G‘‘
Disadvantage of the method:
 Peak tan() is above glassy state (approximately 10°C to 30°C)
glassy
G‘
rubber
elastic
melt
sample is getting
solid like (inbetween rubber
elastic and solid
sample has
reached a glassy
state
Tg(Peak tan-)
G‘
‘
glass
transition
T
36
DMTA - How to determine Tg
Tg according to the Peak G‘‘ method: ASTM D4065
 Below Peak-G‘‘ the molecular structure is getting rigid and unflexible
 Peak G‘‘ method is easy to evaluate
 Disadvantage: Some polymers are not showing the Peak-G‘‘
glassy
G‘
rubber
elastic
melt
Tg (Peak G’’):
value similar
to Onset G’
Tg(Peak G’’)
G‘‘
glass
transition
T
37
DMTA – How to determine Tg
Tg according to the step analysis: (ISO 11357-1)




Analysis of step in Storage Modulus from glassy to rubbery state
Similar to DSC analysis according to ISO 11357-1
The step can be analyzed mathematically or graphically using the tangent method
Teig is equal to Tgo
glassy
Storage
& Loss
Modulus
Teig=Onset
rubber
elastic
melt
Tmg
Tefg
glass
transition
T
38
DMTA – Tg
Frequency dependency of Tg


The glass transition is a relaxation process
and therefore frequency-dependent
glassy
glass
transition
rubber
elastic
G'
tan()
f=0.1Hz/-> 10Hz
T
39
Crystallization in Tg region
Partially crystalline polymer: ramp down and ramp up
glassy
G’
rubber
elastic
Teig=Onset
Tefg
T
40
Crystallization in Tg region
Partially crystalline polymer: fast & slow cooling
G’
slow cooling
rapid cooling
T
41
Tg and plasticizer (additive)
Mixture of polymer & plasticizer
By adding a plasticizer to a polymer
 Tg can be moved towards lower temperatures
 G’ can be reduced
Tg
% of plasticizer
42
Crystallization
Time & cooling rate dependent
Crystallization strongly depends on the temperature:
 the rate of crystal growth
 the size of the nuclei
many
but small
a few
but larger
Tm
Tg
rate of
crystal growth
43
size of
nuclei
Crystallization
Isothermal crystallization
 The degree of crystallization is a time dependent process
 If there is no more space for further growth
the maximum degree of crystallization is reached
 PP, if stored at RT, shows increasing G’ values over time (secondary crystallization
process by growth in diameter and size)
 Shear can also force crystallization (shear induced crystallization)
maximum
e.g. 90%
relative
degree of
crystallization
time
44
DMTA – Torsion SRF
Measuring parameter
Measuring Profile:
Control, Gap-Setting:
 Standard Workbook
o DMTA Torsion -> DMTA Tg: SRF Rectangular
Fixture
 Frequency and measuring point duration
Measuring profile, standard:
o f = 1Hz and tmp=0.5min
o Number of points = DT / [°C] + 1
 Strain
o Start with g=0.01% below Tg
o Finish with lin slope until g= 0.1% before Tm
o Single check by AS if within LVE-range
 Heating rate
o 2K/min better lower (or practically relevant)
o Precission measurements around Tg with 0.5K/min
o DIN 53445: 1K/min
 Pre-Tension
.
o NF = -1N (negative = Tensional force)
o Gap setting: DMTA Torsion SRF
o SRF moved into position using ‚Touch Control‘
45
Measuring pfofile, precise:
.
DMTA Tests
SRF and Touch Control (Auto tension during sample cooling)
Gap setting profil: DMTA SRF
Do not touch the SRF during auto detection by Toolmaster.
The NF will be reset to zero during the automatic detection of the SRF.
Control 1 ON = Auto NF Compensation ON
Measuring position => Compensation on with 1N compression force (Control 1)
Lift position => Compensation on with -1N tension (Control 1)
STOP => Compensation off
Warning:
Without “Control 1” activated the normal force load may exceed the maximum allowed
force
46
DMTA - Tension UXF
Measuring conditions
Tension
UXF: Universal Extensional Fixture
 Working range
 from rubber like behaviour to solid but below 2000MPa
 for thin films (and fibers)
 Product categories
 Thermo-melts, Elastomer, Rubber, Paint films
 Most common test(s)
 Temperature sweep, , Shrinkage, Contraction
 Recommended sample dimensions
 20mm x 5mm x 0.05mm for stiff samples
 20mm x 10mm x 0.05mm for soft samples
 Typical settings
 Pre-Tension 1MPa...0.2MPa
 1Hz, Amplitude 0.5MPa...0.1MPa, 2K/min, 1Point/K
47
 , s (tensile strain and
tensile stress)
 Moduli E‘, E‘‘, E*
 Loss Factor: tan()
DMTA - Tension UXF
Measuring parameter for thinn polymer films (PE, PP)
Typical measuring profile for films with 5mm width:
• Rotational component = pre-tension
• Oscillating component = tensile stress
• Sample is getting softer with T => Tensile stress should get lower
48
EC-Twist
Reaction kinetics, curing or resins
REACTION
KINETICS
D-PP15
Reaction Kinetics
Tconst or range
NFcontrol
1Hz (10Hz if < 100s)
g  10%-0.05%
G‘, G‘‘, tan()
ISOTHERMAL or T-RAMP
 Softening point
 Pot life
 Gel point
 Curing point
49
D-PP08/15/25
Curing materials
From raw material to final product (Epoxy resins,
elastomers, adhesives)
What can be measured?
 Materials before curing
 Viscosity as a function of shear
 Flow behaviour, yield point
 Thixotropy, time dependent recovery of viscosity after
shear
 Curing behaviour
 Isothermal test or temperature ramp
 Process of curing from liquid to solid
 Degree of cross-linkage
 Stiffness as well as viscous and elastic properties
 Final product after curing
 Material characterization of the final product (DMTA)
 Mechanical parameter such as G or E modulus
 Temperature dependent mechanical behaviour
 Working / use temperature range
50
Raw materials,
before mixing
Liquid+chemicals
(initiator)
Liquid1+liquid2 (2K
adhesive)
Powder (epoxy resin)
Resins before curing
These materials are almost newtonian
Oils and resins must be trimmed in measuring position
 Reason: samples to not adhere to spatula
Better: Use cap plate with 50mm diameter
 CP50-1 and CP50-2 are ideally filled
 no more trimming
 Caution: may require temperature calibration
for higher temperatures
Or: Inset variant with 50 mm screwable plate
 CP50-1 and CP50-2 are ideally filled
 no more trimming
OR: Concentric cylinder CC27 (disposable)
51
!!! Curing reaction of resins are measured using disposables (D-PP15) !!!
Disposable Lower Plate
Mounting the disposable dish
52
PTD – Disposable Dishes
Measuring curing resins with disposable meas. systems
 D-CP/PP7
 D-PPxx
 Disposable dishes
 Fixture for disposable dishes
 INSETxxmm
as an alternative to the disposable dishes (for high
precision measurements using standard
geometries)
53
DMTA Reaction Kinetics
Measuring Parameter
 Standard profile
o Constant strain and frequency, e.g. g = 0.5%, f= 1Hz
 Measuring time
o short (<100s)?
o fast reactions (e.g. within 10s)?
o then frequency = 10Hz
 Always with time setting
o T-Ramp with 0.5min/measuring point
o Time test 0.1min/measuring point
o For shorter times the frequency must be adapted
o tmp,min = 1 / f
o DSO helps to improve measuring results and allows higher data rates
 Always use: PPxx (PP15), better D-PP15 (disposable plates)
 Variable gap
o NF-compensation (NF=0N +/- Hysteresis von 0.5N)
o Minimum position e.g. 0.75mm in „Gap setting parameter for measurement“
 Terminate test by event control?
54
DMTA: Reaction Kinetics
Crosslinking reaction: from liquid to solid
55
DMTA: Reaction Kinetics
Crosslinking reaction: from powder to solid
56
DMTA – Reaction Kinetics
Working with PP – Parallel Plates
General rules
parallel-plate
 Working range
 from melt to solid < 1000MPa
 Product categories
 PSA’s, Hotmelts
 Most common tests
 Temperature sweep, time-temperature superposition
 Shrinkage, contraction
 Recommended plates and maximum allowd G’ in [MPa]
Name Compliance
G',max
G',max, safe
 red: best case with ideal
[rad/Nm]
SRF
UXF
PP08
PP10
PP12
PP15
PP20
PP25
57
1,65E-03
0,95
1,65E-03
1,62E-03
1,55E-03
1,50E-03
1,45E-03
1,40E-03
[MPa]
400.000
200
1.350
280
130
55
12
7,5
[MPa]
80.000
2000
150
30
15
6,25
1,3
0,85
meas. system compliance
 green: safe range with
relatively low error in G’
 Moduli: G‘, G‘‘, G*
 Complex viscosityI*I
 Loss factor: tan()
Tribological Measurement: Stribeck Curve
Example: Steel on polymer
0,7
Steel on PMMA dry
0,6
0,5
m = friction coefficient
0,4
m 0,3
Steel on POM dry
0,2
0,1
0
10-6
10-4
Sliding Speed
58
m/s
1