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Eng8450 + MWNT. Sample annealed 15 minutes in the press (140 C) Around 30 minutes between put the sample in the equipment and to start the experiment.  DC decrease with low amount of CNT!!!!!. DC region. Dielectric region. How we can understand this “rare” behavior?.

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slide1

Eng8450 + MWNT

Sample annealed 15 minutes in the press (140 C)

Around 30 minutes between put the sample in the

equipment and to start the experiment

DC decrease with

low amount of CNT!!!!!

DC region

Dielectric region

slide2

How we can understand this “rare” behavior?

Symmetric Hopping Model

Based on the study of the displacement of a charge carrier

from one position to another close by

The nearest-neighbor jump rate (frequency) is:

It is possible to show that the transition from DC to AC is determined by the smallest jump rate (c) , and the transition will be given by:

From this model is showed that:

So, it is possible to think that the presence of nanotubes increase the

activation energy for the jump-rate of charge carriers or decrease its diffusion

processes. At higher amount the last is compensated by the percolation

process.

slide3

Another approach based on the same arguments define the probability

for a electron (“hole”) transition from state “a” to “b”, as:

’s are the reorganization energy

It is showed that the response of the system to an alternating field is:

The major contribution to the conductivity comes from polymer

pair elements satisfying the last assumption!!!

The response at very low frequencies involve pair states with very low transition rates. As a consequence the rare transitions from pair states into new states become more significant.

Again, the presence of nanotubes could change the dynamic

of charge carriers, decreasing the conductivity

slide4

Another theory is based on the equivalent circuit concept:

Any solid with spatially varying free

charge conductivity and uniform

charge dielectric constant

At high frequencies the conductive regions are important

and at low frequencies the isolated areas limit the charge carrier motion.

Under AC conditions, it is defined:

Conductance

contribution

Resistor

contribution

slide5

Eng8450 + MWNT

’ is related with the current

through the resistors

Below the percolation point, the high frequency

area is influenced by the CNT (conductive)

At low frequency, the isolated-region (bulk polymer) make the greater contributions

’’ is related with the current

through the capacitors

The presence of CNT does not affect

the conductance of the sample below

the percolation point

slide6

Eng8450 + SWNT

Same behavior!!!

CNTs affect the resistor contribution of the composite, and

at low frequencies changes in the dynamicof the polymers due to CNT

decrease their conductivity

slide7

The effect of the dynamic of the polymer on the conductivity

is confirmed by the relaxation process observed in some composites

Eng + 1.0 SWNT

3 hrs annealing

140 C

Eng + 0.05 SWNT

3 hrs annealing

140 C

slide8

Eng8450

Effect of the temperature

slide9

Annealing Studies for some Eng/MWNT samples

Effect of the amount of filler

12% MWNT

Pure Eng

1Hz

1% MWNT

slide10

Annealing Studies for some Eng samples

Effect of the kind of filler

1% MWNT

1% SWNT

slide11

Annealing Studies for some Eng samples

Effect of the kind of matrix

Eng

1% MWNT

PE3732C

1% MWNT

slide12

Annealing Studies for some Eng samples

Effect of the kind of matrix

Eng

12% MWNT

PE3732C

12% MWNT

1Hz

slide13

Annealing Studies for some Eng samples

Effect of the kind of matrix

Eng

1% SWNT

PE3732C

1% SWNT

slide14

Eng8450 + MWNT

Effect of the strain on the composite dynamic

0.5 % MWNT

The system is not able to

relax during the shear-strain of 300%

Small relaxation during

shear-strain of 100%

1% MWNT

1 Hz

1 Hz

slide15

Eng8450 + MWNT

Effect of the strain on the composite dynamic

3% MWNT

The shear-strain disrupt the conductivity

but only in the beginning, after that the

system relax independent of the strain!!!!

At this condition the kinetic of the relaxation

is modified by the external forces

The location of this peak is

shear-strain dependent!!!

slide16

Eng8450 + MWNT

Effect of the strain on the composite dynamic

6% MWNT

It is clear that the drop in conductivity

depends of the shear-strain, and again the

system is able to relax independent of the

shear-strain!!!!

slide17

Eng8450 + MWNT

Effect of the strain on the composite dynamic

12% MWNT

slide18

Eng8450 + MWNT

Effect of the strain on the composite dynamic

12% MWNT

10 Hz

slide19

Eng8450 + SWNT

Effect of the strain on the composite dynamic

0.05% SWNT

1.0% SWNT

slide20

PE3732C + MWNT

Sample annealed 15 minutes in the press (140 C)

Around 30 minutes between put the sample in the

equipment and to start the experiment

Same behavior than Eng

sample, the changes are related

with the resistor contribution

slide21

PE3732C + SWNT

Sample annealed 15 minutes in the press (140 C)

Around 30 minutes between put the sample in the

equipment and to start the experiment

slide22

PE3732C + MWNT

Effect of the processing on the composite dynamic

6% MWNT

This plot shows that the decrease in the conductivity is associated with the

morphology of CNTs in the polymeric matrix

slide23

PE3732C + MWNT

Effect of the strain on the composite dynamic

0.05% SWNT

1% MWNT

1% SWNT

6% MWNT

slide25

PE3732C + MWNT

Effect of the strain on the composite dynamic

12% MWNT

slide26

PE3732C + MWNT

Effect of the strain on the composite dynamic

12% MWNT

10% strain

100% strain

Strain-induced insulation!!!

100% strain, 1 min

Effect of time

100% strain, 20 min

slide27

PE3732C + SWNT

Effect of the strain on the composite dynamic

0.05% SWNT

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