One of the main objectives of this thesis is to disperse double-walled carbon
nanotubes (DWNT) in a polyvinylidene fluoride (PVDF) matrix, and to characterize the
resulting composite using electrical, thermal, and mechanical characterization techniques.
DWNTs are successfully dispersed in the PVDF, and this dispersion is assessed by using
optical microscopy and both scanning and transmission electron microscopy.
The second objective of this study is to investigate the morphology of the PVDF after
adding the carbon nanotubes. The results using the x-ray diffraction technique do not
show change in the PVDF morphology with addition of DWNTs. In Differential scanning
calorimetry study the results show that the melting temperature does not vary much with
addition of DWNTs. An increase in the crystallization temperature and a decrease in the
percent crystallinity is also observed as DWNT content increases.
The electrical and mechanical properties of the composites are measured and data is
used to calculate the percolation volume fraction using electrical conductivity. The results
show that the percolation threshold occurs at 0.23 vol%, which is a low volume fraction
further indicating a good dispersion. The critical exponent implies a three dimensional
dispersion. The predicted volume fraction at percolation using the excluded volume approach indicates that the DWNTs are dispersed in small bundles of seven hexagonally
closed packed tubes. The mechanical properties are done using dynamic mechanical
analysis to study the effect of the nanotubes on the mechanical properties. The results
show that the storage modulus is enhanced 84% by adding 4.51 vol% DWNT-PVDF
below the glass transition temperature which is in a -45ðC region and it is increased by
about 97% at 40ðC.
Electromechanical performance of the composites is assessed by testing the actuation
behavior using DC voltage. The results show no actuation for volume contents below
percolation, and a measurable actuation at volume contents above percolation.
Results from the different characterization techniques indicate that the DWNTs are
successfully dispersed. An enhancement in electrical conductivity and dielectric constant
is achieved by addition of DWNTs. At DWNT volume content above percolation, both
mechanical and electromechanical enhancements are observed, as evidenced by DMA
and electroactive characterization techniques.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4920 |
| Date | 25 April 2007 |
| Creators | Almasri, Atheer Mohammad |
| Contributors | Ounaies, Zoubeida |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 2490282 bytes, electronic, application/pdf, born digital |
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