Re-aggregation of carbon nanotubes in two-component epoxy system

Carbon nanotubes, because of their outstanding features, are one of the potential reinforcements for thermosetting polymers. Among many other processing issues, which need to be solved, re-aggregation of the nanotubes in polymer colloidal mixtures is a major one. Re-aggregation of different nanotubes (single walled, double walled, amino-modified double walled, thin multi walled and COOH-modified thin multi walled) in a two-component epoxy system (liquid epoxy, liquid hardener and a liquid epoxy-hardener mixture) was investigated involving a nano-particle size analyzer. Dispersion characterization of cured samples was carried out using scanning electron microscopy. Re-agglomeration with time was observed in all samples and was found to be least in liquid epoxy compared to liquid hardener and the liquid epoxy-hardener mixture. Along with other processing factors, like curing and degassing, the hardener in the liquid-epoxy mixture was mainly responsible for re-aggregation. Suggestions for altering processing parameters in order to avoid this are discussed.