Ethylene vinyl acetate/expanded graphite nanocomposites by solution intercalation: preparation, characterization and properties

Nanodimensional reinforcing agents are introduced to polymer matrices to improve properties at very low loading. Natural graphite (NG) as such is not reinforcing in nature. But when modified to expanded graphite (EG) by high temperature heat treatment, this may be used as reinforcing nanofiller. In the present study, ethylene vinyl acetate (EVA) was reinforced with EG by solution intercalation, and the composite properties were compared with those of the virgin polymer and NG filled composite. The tensile strength exhibited an improvement of 35% with 4 wt% EG addition, while the modulus at 100% elongation was increased by 150% with respect to the control EVA. Another interesting feature was that unlike the conventional fillers, addition of EG did not reduce the elongation at break, due to the lubricating action of graphite. However, at a high loading of 8 wt%, the tensile strength showed a lower value, due to the agglomeration of graphite platelets. The storage modulus also showed increment with the addition of graphite without much change in the glass transition temperature. In addition to these, the EVA-EG nanocomposites exhibited high thermal conductivity and thermal degradation stability as compared to the virgin polymer. About 4 wt% of EG shifted the temperature of maximum rate of degradation by 14 °C towards higher temperature. These results were well supported by the swelling and morphological studies. The NG filled composite exhibited inferior properties to EVA-EG nanocomposites.