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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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?
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.
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
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
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
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
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
Eng8450
Effect of the temperature
Annealing Studies for some Eng/MWNT samples
Effect of the amount of filler
12% MWNT
Pure Eng
1Hz
1% MWNT
Annealing Studies for some Eng samples
Effect of the kind of filler
1% MWNT
1% SWNT
Annealing Studies for some Eng samples
Effect of the kind of matrix
Eng
1% MWNT
PE3732C
1% MWNT
Annealing Studies for some Eng samples
Effect of the kind of matrix
Eng
12% MWNT
PE3732C
12% MWNT
1Hz
Annealing Studies for some Eng samples
Effect of the kind of matrix
Eng
1% SWNT
PE3732C
1% SWNT
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
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!!!
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!!!!
Eng8450 + MWNT
Effect of the strain on the composite dynamic
12% MWNT
Eng8450 + MWNT
Effect of the strain on the composite dynamic
12% MWNT
10 Hz
Eng8450 + SWNT
Effect of the strain on the composite dynamic
0.05% SWNT
1.0% SWNT
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
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
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
PE3732C + MWNT
Effect of the strain on the composite dynamic
0.05% SWNT
1% MWNT
1% SWNT
6% MWNT
PE3732C + MWNT
6% MWNT
PE3732C + MWNT
Effect of the strain on the composite dynamic
12% MWNT
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
PE3732C + SWNT
Effect of the strain on the composite dynamic
0.05% SWNT