(584c) Using Surface Energy Values to Predict Mechanical Performance in Nanocomposites

The use of nanomaterials as composite reinforcing materials has shown significant interest in recent years. Both carbon nanotubes and clay nanoparticles have been studied as a means to improve composite properties. The quality and performance of nanocomposites depend strongly on the interaction of the components at their interface. Filler-matrix interactions are commonly described by adhesion and cohesion phenomena. Both properties depend on the surface energetic situation of the materials, commonly expressed by the surface energy. In this study, surface energies of different multi-walled carbon nanotubes (MWCNT) and nanoclays with various surface treatments were determined by IGC. Polyurethane (PU) was used as the model matrix material. Nanofiller-matrix interactions have been calculated by means of the thermodynamic work of adhesion from the surface energy values and correlated with composite mechanical properties measured by dynamic mechanical thermal analysis. The different surface treatments on the nanofiller materials dramatically changed the materials' surface energy and thermodynamic works of adhesion. In all cases, the ratio between thermodynamic work of adhesion (filler-matrix interactions) and thermodynamic work of cohesion (filler-filler interactions) correlated directly with changes in composite mechanical properties. Therefore, it was possible to predict changes in composite strength based on the surface energy values of the individual components.