Towards tough, yet stiff, composites by filling an elastomer with single-walled nanotubes at very high loading levels

We have used recent advances in nanotube dispersion technology to prepare composites based on polyurethane, with mass fractions of up to 80% polyethylene glycol functionalized nanotubes. Mechanical testing shows increases in Young's modulus compared to polyurethane films by up to 800 x. While the composite strength did not vary significantly with nanotube content, the ductility and so the toughness fell by a factor of 240 x on addition of similar to 40 wt% nanotubes. Depending on the nanotube content we can produce films ranging from the stiff and brittle at high nanotube loading to the compliant and ductile at low nanotube volume fraction.