3D chemically cross-linked single-walled carbon nanotube buckypapers

Abstract

Single-walled carbon nanotubes (SWCNTs) covalently modified with OH functional groups were assembled into buckypapers through solvent dispersion and vacuum filtration. These SWCNT-OH buckypaper sheets were subsequently crosslinked by wetting with bifunctional linkers followed by hot compression causing reaction between the functional groups of the reagent and OH functional groups on the side-walls of SWCNTs to create three-dimensional (3D) covalently cross-linked buckypapers. Cross-linking also was performed using SWCNTs encapsulated with a functionalized polymer wrapping in a core-shell structure, where OH or/and NH 2 groups are available on the surface of the polymeric shell for reaction. The 3D cross-linked SWCNT buckypapers retain the porous character typical of buckypaper, and were characterized for their tensile properties and thermal and electrical conductivities. Several cross-linking approaches dramatically improved the mechanical properties. The strongest and stiffest papers (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 a high-performance epoxy resin monomer, improvements in strength and stiffness of ~5× were obtained while retaining electrical and thermal conductivity. Therefore, the optimal crosslinking approach would be determined by the desired, multifunctional properties. Additionally, the approach can be used in the preparation buckypaper composites and it is demonstrated that cross-linking using a multifunctional epoxy resin prior to impregnation with the same epoxy resin results in substantially better mechanical properties than comparison to just epoxy-impregnation of pristine buckypaper.

Epoxidized multi-walled carbon nanotube buckypapers: A scaffold for polymer nanocomposites with enhanced mechanical properties

“…Hence, the mechanical properties reported are moderate due to the low content of nanotubes. Certainly, there are literature works of buckypaper-based nanocomposites reporting very good mechanical results ( [16,18,[38][39][40], but they don't include flexural results. The best results have been observed when nanotubes are aligned [38].…”

Thermal conductivity of bulk boron nitride nanotube sheets and their epoxy‐impregnated composites

“…Thermal conductivities of the BNNT sheets were measured using the parallel thermal conductance (PTC) method , which has been applied previously to characterize CNT sheets and yarns . This steady‐state method is ideal for nanotube sheet samples because they cannot support thermometers or heaters as required by some conventional methods.…”

Effects of Conformal Nanoscale Coatings on Thermal Performance of Vertically Aligned Carbon Nanotubes

“…Although, these assemblies aim at exploiting the exceptional intrinsic properties, namely high electrical and thermal conductivity, high strength and flexibility, of an individual CNT at the macroscopic scale, they often show a remarkable drop (up to several orders of magnitude) of the abovementioned properties. This is related to the difficulty in achieving uniform distribution of catalysts, defect‐free tubes, and an effective interfacial bonding between CNTs and the substrate …”