Processing-structure-property relationships of SWNT-epoxy composites prepared using ionic liquids

Experimentally achieved mechanical properties of nanotube-epoxy composites fail to match theoretical expectations; shortcomings are mainly attributed to poor dispersion. The elastic modulus of a well-dispersed single walled carbon nanotube (SWNT)-ionic liquid-epoxy composite was evaluated in tension and compared to predictions by a micromechanics homogenization model. The model takes into account the mechanical properties of the constituent phases in addition to SWNT aspect ratio, spatial distribution, dispersion, and agglomeration. These parameters were evaluated using information obtained via scanning and transmission electron microscopy. The Young's modulus of the composite shows excellent agreement with the model at low concentrations, while discrepancies at high SWNT concentrations are possibly due to composite processing limitations. At high concentrations the uncured composite mixture is above the rheological percolation threshold. As the polymer network reaches its maximum capacity for well-dispersed SWNTs, increasing volume fraction does not result in further significant reinforcing effects.