The effect of molecular structure of amine moieties of multiwall carbon nanotubes (MWCNTs) on mechanical properties of reinforced composites was investigated. Functionalization of MWCNTs was performed via a quick, one-pot and microwaveassisted method, using aminobenzene (AB), ethylenediamine (EDA), 1,6-hexamethylenediamine (HDA), and 1,4-diaminobenzen (DAB). Quantitative (FT-IR) and quantitative (TGA) characterizations were carried out and degree of functionalization was measured. The power of microwave radiation and exposure time of samples were considered as two main operational parameters for control of functionalization degree. Quantitative evaluations revealed that the microwave irradiation power is more effective than exposure time for enhancement of functionalization degree. MWCNTs were highly functionalized with all amine functionalities and among them, all diamine functionalities showed higher functionalization degree than AB. Moreover, DAB introduced more amine moieties on surface of MWCNTs than other two diamines due to its higher reactivity. Functionalization degree of EDA was also higher than HAD due to its shorter molecular chain and consequently lower steric hindrance. Mechanical properties of amine-functionalized MWCNT/epoxy composites showed remarkable improvements. Investigations revealed that mechanical properties of composites are considerably influenced by functionalization degree of MWCNTs. Functionalized MWCNTs with equal functionalization degree were used to study the effect of amine moieties on mechanical properties of composites. Results indicate that diamine functionalities can better strengthen the epoxy resin than AB due to high potentials in covalent binding of MWCNTs to the epoxy resin. Moreover, EDA and HDA as aliphatic compounds were more successful in reinforcing epoxy resin than DAB as an aromatic compound which can be attributed to higher stress tolerance of them. Finally, dispersibility of as-received and functionalized MWCNTs in epoxy resin was studies through SEM observation of fractured surface of composites. In contrast to as-received MWCNTs with severe agglomerations, functionalized MWCNTs were uniformly dispersed in matrix. Detailed examination of amine moieties demonstrates that although aromatic compounds provide higher functionalization degree on MWCNT, aliphatic compounds have higher stress tolerance that resulted in better reinforcement of MWCNT/epoxy composites.

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