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Dielectro-Rheological Device (DRD)

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Dielectric Spectroscopy: The measurement

+ Dielectric +

Induction of an - electric field -

Voltage application

DC or AC voltage

Measurement of the flowing current

LCR meter

Voltage

Current

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

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Dielectro-Rheological Device (DRD)

Setup for Peltier and CTD chambersavailable

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-SpectroscopyDielectro Rheological Device DRD

An electrical potential is applied by a spring system onto the shaft and the capacitance is measured.

Measuring Plate PP25/PP50

Peltier

The bottom measuring plate is isolated to the Rheometer

Goldspring or -wire contact

Contact

Ceramic isolation

CounterCooling

Sample

Uniform temperature distribution with Peltier Hood (-40°C - +200°C)

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Dielectro Rheology Example: Polymer Carbon Black Composite

Carbon black clusters dispersed in a polymer matrix. Carbon black induces dielectric properties in the composite.

Creep Test

0

0.5

1

1.5

2

2.5

0 50 100 150 200 250 300 350

time [s]

str

ain

[%

]

Conductivity

1.00E-10

1.00E-09

1.00E-08

1.00E-07

0 50 100 150 200 250 300 350

time [s]

σ' [

S/c

m]

Rheology:(Shear stress: 65400 Pa)

Dielectricity:(Frequency: 1 kHz)

Slow mechanical relaxation of long chain polymers

Fast electrical relaxation of carbon black clusters

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Epoxy resin filled with carbon nanotubes

0.00E+00

5.00E-09

1.00E-08

1.50E-08

2.00E-08

2.50E-08

0.1 1 10 100

Shear rate [s-1]

Ca

pa

cit

an

ce

[F

]

1

10

100

1000

Vis

co

sit

y [

Pa

s]

CapacityViscosity

Flow curve: 0.1 – 100 s-1 , 1 kHz and 1V

The nanotubes are inducing electric conductivity in the resin.

Capacity changes due to an orientation of the nanotubes

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Epoxy resin filled with carbon nanotubes

0.00E+00

5.00E-09

1.00E-08

1.50E-08

2.00E-08

2.50E-08

3.00E-08

3.50E-08

4.00E-08

4.50E-08

5.00E-08

0.1 1 10 100 1000

Strain [%]

Ca

pa

cit

an

ce

[F

]

1.00E+00

1.00E+01

1.00E+02

1.00E+03

Sto

rag

e /

Lo

ss

mo

du

lus

[P

a]

CapacitanceG´G´´

Strain sweep 0.1 -1000% at 10 1/s, 1kHz and 1V

Capacity is constant within the linear viscoelastic range and decreases in the non-

linear regime due to an alignment in flow direction.