Oligomer functionalization of multi-wall carbon nanotubes

Date of Award

2015

Degree Name

M.S. in Chemical Engineering

Department

Department of Chemical and Materials Engineering

Advisor/Chair

Advisor: Khalid Lafdi

Abstract

In an effort to translate the superlative mechanical properties of multiwalled carbon nanotubes (MWCNT) to polymeric media, a novel oligomeric functionalization approach is investigated here. Industrial multiwall carbon nanotubes were subjected first to a gas-phase oxidation process followed by grafting with an amine derivative based on the reaction between diaminodiphenylsulfone (DDS) and triglycidal p-aminophenol (TGAP). By reacting the TGAP with an excess of DDS, a long chain molecule with free amine groups was created that could react with the functionality of the MWCNTs. The synthesized amine derivative oligomer was reactively attached to the MWCNTs via two methods. The first used a diazonium salt reaction scheme whereby isoamyl nitrite was used to convert the aryl amine (AD) to the diazonium salt, which could then couple with the MWCNT through electron donation. The second method used a peptide coupling agent, O-Benzotriazole-N,N,N'N'-tetramethyl-uronium-hexafluoro-phosphate (HBTU), to aid in the reaction between the free amine of the DDS:TGAP amine derivative and the carboxylic acid on the nanotube. To determine the effect the oligomer functionalized carbon nanotubes had on a polymeric system, the AD grafted tubes were dispersed into tetraglycidyl methylene dianiline (TGMDA) at 0.5, 1, & 2wt% concentration and cured with DDS. Parallel plate rheometric analysis was then performed on the resulting systems to determine how the functionalized carbon nanotubes affected the rheological properties of the polymer. It was discovered that the functionalized carbon nanotubes had a catalytic effect on the polymer system, accelerating the onset of cure. Furthermore, loss and storage modulus analysis revealed uncommon behavior in the MWCNT enhanced systems, resulting in gel point determination that was not characterized by G1'G crossover. Cured specimens were then tested in oscillating torsion to determine oscillation stress increases over the unmodified polymer with increasing temperature. The greatest increase in oscillation stress over the unmodified TGMDA:DDS polymer, 67%, was recorded at 400°F by the 0.5wt% HBTU modified TGAP:DDS functionalized MWCNT system. Three point bend testing was then performed on cured specimens to determine the reinforcing properties of the oligomer functionalized carbon nanotubes. Testing revealed that the HBTU:AD functionalized MWCNT at 0.5wt% loading increased average ultimate flexural strength by 77% over the unmodified system ."

Keywords

Oligomerization, Carbon nanotubes Mechanical properties, Polymeric composites Design and construction, Chemical Engineering, Carbon Nanotube, MWCNT, Functionalization

Rights Statement

Copyright © 2015, author

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