Dielectro-Rheological Device
(DRD)
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Dielectric Spectroscopy: The measurement
 Electrical current flowing through a sample as a response to an alternating electric
field is measured as a function of the field frequency
 Dielectric spectrum gives information on structure and behavior of the material
Voltage application
+
Dielectric
+
Induction of an
- electric field -
Voltage
DC or AC voltage
LCR meter
Current
Measurement of the
flowing current
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Dielectro-Rheological Device (DRD)
Setup for Peltier and CTD chambers
available
Contact at upper geometry by spring
(Rotation) or wire (Oscillation)
Applications
 Filled rubbers
 Polymers nanocomposites
 carbon nanotubes
 clays
 Battery research
 Conductivity of filled polymers
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Rheo-Dielectric-Spectroscopy
Dielectro Rheological Device DRD
 An electrical potential is applied by a spring system onto the
shaft and the capacitance is measured.
Ceramic isolation
Goldspring or
-wire contact
Measuring Plate
PP25/PP50
Sample
The bottom measuring
plate is isolated to the
Rheometer
Contact
Peltier
Counter
Cooling
 Uniform temperature distribution with Peltier Hood (-40°C - +200°C)
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Dielectro Rheology Example:
Polymer Carbon Black Composite
Creep Test
2.5
Rheology:
2
strain [%]
 Carbon black clusters dispersed in a
polymer matrix.
 Carbon black induces dielectric
properties in the composite.
(Shear stress: 65400 Pa)
1.5
1
0.5
0
0
50
100
150
200
250
300
350
time [s]
Conductivity
1.00E-07
 Slow mechanical relaxation
of long chain polymers
 Fast electrical relaxation of
carbon black clusters
σ' [S/cm]
Dielectricity:
(Frequency: 1 kHz)
1.00E-08
1.00E-09
1.00E-10
0
50
100
150
200
250
300
time [s]
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350
Epoxy resin filled with carbon nanotubes
The nanotubes are inducing electric conductivity in the resin.
Flow curve: 0.1 – 100 s-1 , 1 kHz and 1V
2.50E-08
1000
Capacitance [F]
2.00E-08
100
1.50E-08
1.00E-08
10
Viscosity [Pas]
Capacity
Viscosity
5.00E-09
0.00E+00
1
0.1
1
10
100
Shear rate [s-1]
 Capacity changes due to an orientation of the nanotubes
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Epoxy resin filled with carbon nanotubes
5.00E-08
4.50E-08
4.00E-08
3.50E-08
3.00E-08
2.50E-08
2.00E-08
1.50E-08
1.00E-08
5.00E-09
0.00E+00
1.00E+03
1.00E+02
1.00E+01
Capacitance
G´
G´´
Storage / Loss modulus [Pa]
Capacitance [F]
Strain sweep 0.1 -1000% at 10 1/s, 1kHz and 1V
1.00E+00
0.1
1
10
100
1000
Strain [%]
 Capacity is constant within the linear viscoelastic range and decreases in the nonlinear regime due to an alignment in flow direction.
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