CHARACTERIZATION AND PROPERTIES OF DOUBLE-WALLED CARBON NANOTUBES FILLED EPOXY NANOCOMPOSITES

Double-walled CNTs (DWNTs) synthesis was performed by CCVD [4]. Extraction and purification was performed by a non-damaging soft soaking in a HCl aqueous solution, to prepare a DWNTs suspension [4]. The used polymer matrix is an epoxy resin (RTM6 from Hexcel Composites France). RTM6 was supplied as a mono-component resin in which prepolymer and hardener are previously mixed increasing the difficulty to disperse the DWNTs. A specific experimental process assisted by amphiphilic molecules (hexadecylamine C16-H33-NH2, or HDA) was set up to disperse the DWNTs into RTM6. The DWNTs suspension, in water or water-HDA (0.4 wt. %) solution, was mixed with the epoxy resin. After water evaporation, a fraction of this mixture was molded and cured according to the resin manufacturer specifications. Bar and disklike nanocomposites samples, for dynamical mechanical and electrical conductivity measurements respectively were prepared. The rest of the uncured viscous mixture was used to the viscosity measurements useful to control the RTM processing. The DWNTs mass fraction in samples was 0.4 wt.%. FEG-SEM images (Fig. 1) reveal a better dispersion of the DWNTs in the matrix for samples prepared with HDA. The electrical conductivity of the DWNTs-(HDA)-RTM6 nanocomposite (10 S/m) is one order of magnitude higher that (10 S/m) for the DWNTsRTM6 nanocomposite. For the mechanical properties, the addition of HDA yields a 15% increase in storage shear modulus (G’) at ambient temperature (Fig. 2). It is proposed that the amine groups of HDA interact with the epoxy matrix, while the aliphatic chains wrap the DWNTs. Although a low DWNTs content (< 0.1 wt.%) is enough to synthesize conducting nanocomposites, a mass fraction of at least about 0.2 wt.% is necessary to improve the mechanical properties. However, ongoing studies will enable to define a mass fraction upper limit with respect to a relatively low viscosity of uncured nanocomposites, to maintain the good processing of epoxy resin for injection on a fibrous preform. Fig.1. FEG-SEM images of the DWNTs-RTM6 (a) and DWNTs-(HDA)-RTM6 (b) epoxy-matrix nanocomposites. Fig. 2. Storage shear modulus (G’) and loss factor of RTM6 resin, DWNTs-RTM6 and DWNTs-(HDA)-RTM6 epoxy-matrix nanocomposites. 1. F.H Gojny, M.H.G Wichmann, B. Fiedler, W. Bauhofer, K. Schulte. “Influence of the nano-modification on the mechanical and electrical properties of conventional fibrereinforced composites”. Composite part A. Vol. 36, pp 1525-1535, 2005. 2. H. Park, J. Zhao, J. Ping Lu. “Effects of side wall functionalization on conducting properties of single wall carbon nanotubes”. Nanoletters, Vol. 6 N. 5, pp 916-919, 2006. 3. S. Barrau, P. Demont, E. Perez, A. Peigney, Ch. Laurent, C. Lacabanne. “Effect of palmitic acid on the electrical conductivity of carbon nanotubes epoxy resin composites”. Macromolecules, Vol. 36, pp 9678-9680, 2003. 4. E. Flahaut, R. Bacsa, A. Peigney, Ch. Laurent. "Gram-scale CCVD synthesis of double-walled carbon nanotubes". Chem. Commun., 2003, pp 1442-1443, 2005. b) a) b) 50 100 150 200 250 1E7 1E8 1E9