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Carbon Nanotubes Filled Polymer Composites: A Comprehensive Study on Improving Dispersion, Network Formation and Electrical Conductivity

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dc.contributor.advisor Barrera, Enrique V.
dc.creator Chakravarthi, Divya Kannan
dc.date.accessioned 2011-04-20T15:49:16Z
dc.date.available 2011-04-20T15:49:16Z
dc.date.issued 2010
dc.identifier.uri http://hdl.handle.net/1911/61368
dc.description.abstract In this dissertation, we determine how the dispersion, network formation and alignment of carbon nanotubes in polymer nanocomposites affect the electrical properties of two different polymer composite systems: high temperature bismaleimide (BMI) and polyethylene. The knowledge gained from this study will facilitate optimization of the above mentioned parameters, which would further enhance the electrical properties of polymer nanocomposites. BMI carbon fiber composites filled with nickel-coated single walled carbon nanotubes (Ni-SWNTs) were processed using high temperature vacuum assisted resin transfer molding (VARTM) to study the effect of lightning strike mitigation. Coating the SWNTs with nickel resulted in enhanced dispersions confirmed by atomic force microscopy (AFM) and dynamic light scattering (DLS). An improved interface between the carbon fiber and Ni-SWNTs resulted in better surface coverage on the carbon plies. These hybrid composites were tested for Zone 2A lightning strike mitigation. The electrical resistivity of the composite system was reduced by ten orders of magnitude with the addition of 4 weight percent Ni-SWNTs (calculated with respect to the weight of a single carbon ply). The Ni-SWNTs - filled composites showed a reduced amount of damage to simulated lightning strike compared to their unfilled counterparts indicated by the minimal carbon fiber pull out. Methods to reduce the electrical resistivity of 10 weight percent SWNTs -- medium density polyethylene (MDPE) composites were studied. The composites processed by hot coagulation method were subjected to low DC electric fields (10 V) at polymer melt temperatures to study the effect of viscosity, nanotube welding, dispersion and, resultant changes in electrical resistivity. The electrical resistivity of the composites was reduced by two orders of magnitude compared to 10 wt% CNT-MDPE baseline. For effective alignment of SWNTs, a new process called Electric field Vacuum Spray was devised to overcome viscosity within the dispersed nanotube polymer system, and produce conductive MDPE-SWNT thin films. Polarized Raman spectroscopy and scanning electron microscopy (SEM) analysis on the samples showed an improvement in SWNT -- SWNT contacts and alignment in the polymer matrix. The resistivity of the samples processed by this new method was two order magnitudes lower than the samples processed by hot coagulation method subjected to electric field.
dc.format.extent 149 pages
dc.format.mimetype application/pdf
dc.language.iso eng
dc.relation.ispartofseries AAT 3425206
dc.subject Carbon nanotubes
Polymer composites
Dispersion
Network formation
Electrical conductivity
dc.title Carbon Nanotubes Filled Polymer Composites: A Comprehensive Study on Improving Dispersion, Network Formation and Electrical Conductivity
dc.type.genre Thesis
dc.type.material Text
thesis.degree.discipline Mechanical Engineering
thesis.degree.discipline Materials Science
thesis.degree.discipline Nanotechnology
thesis.degree.grantor Rice University
thesis.degree.level Doctoral
thesis.degree.name Doctor of Philosophy
dc.identifier.citation Chakravarthi, Divya Kannan. (2010) "Carbon Nanotubes Filled Polymer Composites: A Comprehensive Study on Improving Dispersion, Network Formation and Electrical Conductivity." Doctoral Thesis, Rice University. http://hdl.handle.net/1911/61368.

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