Shuqin Li

Effect of functionalized multi-walled carbon nanotubes on the curing behavior and thermal stability of epoxy resin

Multi-walled carbon nanotubes (MWNTs) were modified by triethlene-tetramine (TETA) in order to attain better dispersibility and stronger interfacial bonding between MWNTs and epoxy matrix. The influence of surface treated MWNTs on the cure behavior of the diglycidyl ether of bisphenol A (DGEBA)/2-ethyl-4-methyl imidazole (EMI-2,4) system was investigated with nonisothermal differential scanning calorimetry. It was found that the curing peak temperature (T P) decreased with the addition of TETA-MWNTs. The curing apparent activation energy (E a) was calculated through Kissinger method. In addition, the thermal behavior of TETA-MWNTs/DGEBA/EMI-2,4 was examined by thermogravimetric analysis, and the result showed the addition of TETA-MWNTs could increase the thermal decomposition onset temperature (T B) and the degradation peak temperature (T max) of the nanocomposites. Scanning electron microscopy images of fractured surface of MWNTs/epoxy indicated homogeneous dispersibility of TETA-MWNTs and strong interfacial adhesion between the TETA-MWNTs and the epoxy matrix in the nanocomposites.

Significantly enhanced dielectric response in composite of P(VDF-TrFE) and modified multi-walled carbon-nanotubes

Abstract To develop a high dielectric constant composite of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] and multi-walled carbon-nanotubes (MWCNTs) with desirable homogeneity, MWCNTs were treated with a nitro-sulfuric acid by ultrasonication. Improvement of the dispersibility of chemically modified MWCNTs (a-MWCNTs) in polymer matrix, in comparison with that of unmodified MWCNTs in P(VDF-TrFE), was confirmed by field emission scanning electron microscopy (FESEM)-observed morphologies. Electric behavior of the composites with different volume fraction of dispersed carbon nanotubes phase can be described mainly by percolation theory. The percolation threshold (fc) of composites with a-MWCNTs (fc=0.0308) is larger than that of composites with MWCNTs (fc=0.0216) due to better dispersion of a-MWCNTs in polymer matrix and the reduction of aspect ratio of a-MWCNTs occurred in the modification procedure. The composite with 2.98 vol% (a volume fraction close to the percolation threshold) of a-MWCNTs has a dielectric constant of 592 at 100Hz and room temperature. The composite remains very flexible with an elastic modulus close to that of the parent copolymer.