Transcript The Piezoelectric, Electric, and Dielectric Properties of

The Piezoelectric,
Electric, and Dielectric
Properties of Amorphous
Polyimide Polymers
A research investigation by Paul Paris
and Dr. Joseph Ficht under the direct
supervision of Dr. Zoubeida Ounaies
Project One Synopsis

To investigate the effect of carbon
nanotubes (CNT’s) in terms of content
and method of processing, on the
piezoelectric, electric, and dielectric
properties of an amorphous
piezoelectric polyimide polymer.
Project Two Synopsis

To investigate the effect of carbon
nanofibers (CNF’s) and carbon
nanotubes (CNT’s) on the mechanical,
electrical, and dielectric properties of
PVDF
What is an Amorphous Polymer?





A polymer with randomly oriented molecules
that are intertwined like cooked spaghetti
The polymer has a glasslike, transparent
appearance
Examples:
Polystyrene-hard and rigid plastic at room
temperature
Polyethyl Acrylate- soft, flexible rubbery
material at room temperature
Electroactivity
E
l’<l
What Is Piezoelectricity?
Actuator function:
Sensor function:
Force
Piezoelectricity
• Requires dipole orientation
• Dipoles collectively respond to field
due to remnant polarization
• Sensing and actuation capability
What is a Polyimide ?
Structure of bCN(APB/ODPA), Polyimide





A polymer of imide monmers that in
conjunction with the carbon nanotubes, produce
a composite that has excellent physical,
electrical, and mechanical properties
Light weight and flexible
Multilayer insulators
Resistance to harsh space environment
Good support structures
What is Polyvinyl Difluoride?
Polyvinyl Difluoride (PVDF) is a polymer
comprised of hydrogen, carbon, and fluorine
atoms. It is a polar substance as the hydrogen
atoms lose electrons to the fluorine atoms. In
1969 it was first observed that this polar or
dipole nature could be used to generate
piezoelectricty.
What is a Carbon Nanotube?


A thin layer of graphene
rolled into a seamless
tube and capped at both
ends
Electrical, Thermal, and
Mechanical properties of
graphite help to improve
electrical conductivity,
thus enhancing the
structural composition
of the polymer
Single Walled Carbon Nanotube (SWNT)
What are some applications?
NASA Applications
•Electro-optical Device Technologies
• Precise positioning
• Switches
Health monitoring
Multifunctional Membranes
•Antennas
• Reflectors
• Smart skins
• Tuning and positioning inflatable
structures
Inflatable Antennae
Flow sensors and actuators
Biomedical
•Portable Artificial organs
•lightweight fetal heart monitor
•Ultrasonic imaging
•Tissue engineering
Smart Ski (ACX)
Ultrasonic imaging
Experimental Details



SEM images to investigate
dispersion of CNT’s
Electrode samples for
electrical and dielectric
measurements
Measurement comparison
using thermally stimulated
current measurements (TSC)
 Dielectric and electrical
properties as a function
of frequency at room
temperature before and
after poling
 Pole at a single voltage;
time; temperature
SEM Results of BCN SWNT
.05wt% BCN SWNT Samples
SEM Results of PVDF+ DWNT
Results of Dielectric Constant
Testing on Polyimide
Beta-CN Samples
Dielectric Constant
50
Pure CN
.05wt% HIPCO
.05wt% Laser
40
30
20
10
0
1.00E+00
1.00E+01
1.00E+02
1.00E+03
Frequency (Hz)
1.00E+04
1.00E+05
1.00E+06
Results of Dielectric Testing on
PVDF
200
0.25% CNF
180
0.25% DWNT
PVDF
Dielectric constant
160
140
120
100
80
60
40
20
0
100
1000
10000
100000
Fre que ncy [Hz]
1000000
10000000
Results of Dielectric Testing on
PVDF (Continued)
1.E+00
0.25% CNF
1.E-01
0.25% DWNT
PVDF
Conductivity [S/m]
1.E-02
1.E-03
1.E-04
1.E-05
1.E-06
1.E-07
1.E-08
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
Frequency [Hz]
1.E+05
1.E+06
1.E+07
Results of Adding CNF and DWNT
to PVDF

Pure PVDF is an insulator but adding carbon
nanofibers increased the dielectric constant
and conductivity. Adding the double walled
nanotubes, however, greatly increased the
dielectric constant and conductivity and now
shows the characteristics of a conductor.
QUESTIONS?