Single-walled carbon nanotube bucky paper/epoxy composites: Molecular dynamics simulation and process development

The discovery of carbon nanotubes by Iijima in 1991 has initiated a large number of scientific investigations to explore their unique properties and potential applications. One of the major applications is nanocomposites with nanotubes as the reinforcing material. Currently, nanotube composites are fabricated by using the direct mixing technique. However, this technique is limited by low weight fraction of nanotubes and uncontrollable nanostructures in the composite. This dissertation research presents a new nanocomposite processing method in which single-walled nanotubes (SWNTs) are first preformed into nanotube bucky papers (NBPs) and then liquid epoxy resins are infiltrated through the NBPs and cured to fabricate the composite. The major technical challenges for developing the NBP/Epoxy nanocomposite include (1) understanding of the molecular interactions between nanotubes and epoxy resin at the nanometer scale; (2) fabricating NBPs with uniform nano-scaled rope size and pore size; and (3) realizing resin infiltration through the nanoporous structure of NBPs.; Molecular dynamics (MD) simulations were used to examine the important molecular interactions, including affinity and interfacial bonding. The affinities of two kinds of epoxy systems were examined. Unlike the DGEBA/DETA epoxy system, both EPON 862 epoxy resin and DETDA molecules had good affinities with SWNT and were chosen as the matrix material in the nanocomposites. Pullout simulations of a SWNT from cured epoxy resins were performed to investigate the stress transfer potential of the SWNT/Epoxy interface. The estimated interfacial shear stress is up to 75 MPa. The MD simulation results were found useful to guide the process development and property prediction of NBP/Epoxy nanocomposites.; Experimentally, the fabrication process for NBPs was analyzed and optimized using the design of experiments (DOE) approach. The SEM and AFM image analyses of the resultant nanocomposites indicated observable wetting and bonding between nanotubes and the epoxy resin. The dynamics mechanic analysis (DMA) showed that a 200–250% increase of the storage modulus was achieved in the nanocomposites. This research is the first attempt to make nanocomposites using nanotube bucky papers.