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 ×. While the composite strength did not vary significantly with nanotube content, the ductility and so the toughness fell by a factor of 240 × on addition of ∼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.