Thermal and mechanical properties of single-walled carbon nanotube bundle-reinforced epoxy nanocomposites: the role of solvent for nanotube dispersion

Single-walled carbon nanotubes (SWNTs) dispersed with various solvents were incorporated into epoxy matrix via sonication method. Dynamics differential scanning calorimetry (DSC) results indicated that even small traces of residual solvent in the composite processing had a great impact on the cure reaction and subsequently affected the endothermic behaviors of the nanocomposites. The solvent selection for nanotube dispersion also had a significant influence on the Vicker's hardness and the flexural strength of the nanocomposites. The solvent effects are in the order of DMF > ethanol > acetone. SEM observation on the fracture surfaces of the nanocomposites did not explain the variance of the nanocomposites properties. The change trend of the thermal and mechanical properties was found to be related to the boiling point of respective solvent used. The results of thermogravimetric analysis (TGA) proved the existence of the residual solvent in the resulting nanocomposites. Further evidence of the solvent influence was obtained by Fourier transform infrared (FTIR) spectra, which displayed the difference in the molecular structure of the final nanocomposites depending on the solvent used. The solvent influence is attributed to the different amount of unreacted epoxide groups and the extent of cure reaction in the manufacturing process.