J. Guan, M.B. Jakubinek, B. Ashrafi, M. Johnson, M.A. White, B. Simard
National Research Council Canada, Canada
pp. 144 - 147
Keywords: carbon nanotubes, buckypaper, cross-linking, nanocomposites
Single-walled carbon nanotubes (SWCNT) covalently modified with OH functional groups were assembled into buckypapers through solvent dispersion and vacuum filtration. These SWCNT-OH buckypapers were subsequently crosslinked by wetting with bifunctional linkers followed by hot compression, causing reaction with OH functional groups on the side-walls of the SWCNTs to form three-dimensional covalently cross-linked buckypapers with modified properties. Cross-linking also was performed using SWCNT encapsulated with a functionalized polymer wrapping in a core-shell structure, where OH or/and NH2 groups are available on the surface. Cross-linked SWCNT buckypapers retain the porous character typical of buckypaper. Several cross-linking approaches dramatically improved the mechanical properties. The strongest and stiffest papers (σ = 32 MPa, E = 3.1 GPa), which approach 10× stronger and stiffer than the pristine non-crosslinked buckypaper, were obtained at the expense of a loss of electrical conductivity. In other cases, such as cross-linking using an epoxy resin monomer, improvements in strength and stiffness of ~5× were obtained while retaining electrical and thermal conductivity. Epoxy-crosslinking also was found to be favorable for production of buckypaper-epoxy composites, where cross-linking using a multifunctional epoxy resin prior to impregnation with the same epoxy resin results in substantially better mechanical properties in comparison to epoxy-impregnation alone.