Investigations of the effect of dispersing medium by ultrasonic method on rheology and viscoelastic properties of epoxy/MWCNT composite

In this study, the effect of the weight percentage of multi-walled carbon nanotubes (MWCNT) and the distribution medium of carbon nanotubes were used as the main factor to investigate the rheological and viscoelastic properties of epoxy/MWCNT composites. To distribute carbon nanotubes, pure epoxy media and a mixture of tetrahydrofuran (THF) solvent and epoxy polymer were used. The quality of the distributor medium was evaluated using rheology, dynamic-thermo-mechanical (DMTA) and scanning electron microscope (SEM) tests. The results of the rheology test showed the values of G and G for the composites produced after distribution of carbon nanotubes in the epoxy/solvent environment were higher than those without solvent. After evaluating the DMTA data, it was found the highest and lowest storage modulus (ʹE) in the glass state and at 37 ℃ for nanocomposite 1-50W22.5RS and pure epoxy were obtained, which were 2855 and 2100 MPa, respectively (about 36% increase for nanocomposite). Also, nanocomposite 1-50W22.5RS, compared to a similar sample without solvent, has increased the storage modulus by 19%. The distribution of 1% by weight of MWCNT in epoxy in the presence of solvent increased the activation energy of nanocomposite 1-50W22.5RS by 26.5% compared to the sample without solvent 1-50W22.5R. The viscoelastic behaviour was modeled by drawing Cole-Cole diagrams using DMTA test results, and the Perez model was used to analyse the viscoelastic behaviour of nanocomposites. The results of tests and analysis of the Perez model showed the best rheological and viscoelastic properties were obtained for the dispersion of 1% by weight of MWCNT in THF/epoxy medium. Comparing Perez's model and DMTA data of nanocomposites, the χ parameter was estimated to be 0.47 and 0.55 for nanocomposites 1-50W22.5RS and 1-50W22.5R, respectively. This decrease indicates the proper distribution of carbon nanotubes in the epoxy field, which is consistent with results of electron microscope images.