Effect of Plasma, Gamma and Chemically Surface Modified MWNTs on the Rheological and Electrical Properties of Ethylene Methyl Acrylate (EMA) Nanocomposites.

Surface modifications of the MWNTs have been carried out by treating the as received MWNTs with plasma (N2 and O2), piranha (H2SO4/H2O2) and γ-ray irradiation under well specified conditions. Surface modifications introduce polar functional groups onto MWNTs surfaces. A variety of characterization techniques including FTIR, Raman spectroscopy, and XPS were employed to characterize the functional group introduced onto MWNTs after the modification. A series of poly(ethylene-comethyl acrylate) (EMA) based nanocomposites containing modified MWNTs has been prepared. Mechanical, morphological, thermal, rheological and electrical properties of these nanocomposites have been investigated. Morphological analyses revealed that MWNTs are more uniformly dispersed in EMA especially for plasma modified MWNTs. Rheological and electrical properties of the nanocomposites are also studied. The nanocomposites register a slightly higher viscosity than that of neat EMA depending on the type of treatment. Storage modulus (in dynamic shear) increases especially at higher frequency levels due to increased polymer-filler interactions. The EMA/MWNT nanocomposites were tested to evaluate their electromagnetic interference (EMI) shielding effectiveness. The enhancements of mechanical properties along with the improvements in electrical and electromagnetic properties by the addition of modified MWNTs have been observed. The MWNTs treated by O2 plasma provides EMA nanocomposites with a higher conductivity than those produced by N2 plasma or by chemical oxidation or by γ-ray irradiation. Overall, the improvements of technical properties of the matrix have been found to be highest with the plasma modified MWNTs in comparison with other modified MWNTs.