Influence of multi-walled carbon nanotubes on the cure behavior of epoxy-imidazole system

The effect of multi-walled carbon nanotubes (MWCNTs) on the cure behavior of diglycidyl ether of bisphenol-A glycidol ether epoxy resin/2-ethyl-4-methylimidazole (DGEBA/EMI-2,4) system during the cure process was studied with dynamic differential scanning calorimetry. The results showed that, at the initial curing stage, MWCNTs act as catalyst and facilitate the curing, moreover, this accelerating effect is already noticeable at the lowest content of MWCNTs investigated (1 wt%) with slightly further effect at higher contents, suggesting a saturation of catalyzing action at higher contents investigated (3.5 wt%). Then, at the later curing stage, MWCNTs prevent from the occurrence of vitrification. The cure acceleration effect caused by MWCNTs could bring positive effect on the processing of composite since it needs shorter pre-cure time or lower pre-temperature, however, the hindrance effect to vitrification phenomena would bring negative effect as it needs longer post-cure time or higher post-temperature. Furthermore, it was also found that the addition of MWCNTs does not change the autocatalytic cure reaction mechanism of the DGEBA/EMI-2,4 system, but decreases the overall degree of cure, as evidenced by lower total heat of reaction and lower glass transition temperatures of the cured composites compared to neat epoxy.