Studies On Preparation And Properties Of The Multi-walled Carbon Nanotubes / Epoxy Nanocomposites

Although some reports have been reported on carbon nanotubes/epoxy composites also have made some progress, the problem of carbon nanotubes well dispersion in polymer matrix has still not been resolved. Some appropriate methods of carbon nanotubes uniformly dispersed in nanoscale to the epoxy resin are the most problem for fabricating perfect performance carbon nanotubes/epoxy composites.In this paper, three different surface modification methods were used to modify MWNTs. After modification a large number of active groups are present on the surface of MWNTs, it is not only effectively prevented MWNTs aggregation but also improved its dispersion in epoxy resin. The composites were produced by solution blending method. The dispersion of different carbon nanotubes in epoxy resin and the performance of the nanocomposites were discussed.The tetraethylenepentamine (TEPA) was grafted to the MWNTs by mixed acid oxidation, acylation and amidation. The test results show that TEPA grafted to the MWNTs increased the spacing between the tubes, and the aggregation had declined. MWNTs-TEPA better than MWNTs can improve the tensile strength, thermal and dielectric properties of nanocomposites. When the MWNTs-TEPA content is 1.5 wt%, the nanocomposites tensile strength and elongation at break compared with pure epoxy resin increased by 84.3% and 150%, respectively, and the glass transition temperature (Tg) increased 18.8 oC, the dielectric constant increased from 6.2 to 25.8, but the value of dielectric loss almost the same with pure epoxy resin.The triethylenetetramine (TETA) was grafted to the MWNTs by mixed acid oxidation and amidation two steps reaction. Influence of the different carbon nanotubes on the mechanical, thermal and dielectric properties of their nanocomposites was investigated. The result indicated that MWNTs-TETA better than MWNTs to improve the overall performance of nanocomposites. When the MWNTs-TETA content is 2.0 wt%, the tensile strength and elongation at break increased by 105.68% and 114.16%, respectively. And the Tg increased 21.55 oC, the dielectric constant increased from 6.2 to 27.6, but the value of dielectric loss almost not increased compared with pure epoxy resin.The MWNTs were coated with polyaniline (PANI) by in situ chemical oxidation polymerization method. PANI coated on carbon nanotubes not only reduced theπ-πbond force but also brought a large number of active groups such as amines, amine can react with the epoxy resin increased the degree of curing reaction. The results show that the MWNTs-PANI can well dispersed in epoxy matrix, produced a well interaction between MWNTs-PANI and epoxy matrix, using MWNTs-PANI as fillers composites have a better overall performance. When the MWNTs-PANI content is 2.0 wt%,the nanocomposites tensile strength and elongation at break increased by 71.49% and 143.67%, respectively. And the Tg increased 26.07 oC, the dielectric constant of nanocomposites gets up to 47, increasing about 7 times of that neat epoxy resin, the value of dielectric loss increased slightly.