Rubber materials normally break down at high temperatures and become brittle when too cold, but to remains stable over a wide range of high temperature. Recently Japan researchers have developed a new viscoelastic material based on nanotechnology.

Viscoelastic materials behave like thick liquids but are also reversibly elastic at room temperature as seen in a variety of materials, including amorphous and semi crystalline polymers, some biomaterials, crystals and even some metallic alloys and at high temperature these materials are unstable. But the new rubber material developed has the same viscoelasticity as that of the most thermally resistant silicone rubber and remains stable over a wide temperature range of –196 °C to 1000 °C.

Metal catalysts which act as seeds for growing the nanotubes from a carbon source, such as ethylene are deposited on a silicon substrate and a drop of water (100–200 ppm) is added to the mix to enhance the growth of long carbon nanotubes. The new rubber is made from a random network of interconnected single, double and triple walled carbon nanotubes. The carbon nanotubes normally just grow upwards using such a technique, but by pre-treating the catalyst, the researchers succeeded in lowering the density of the tubes to create an entangled network of long tubes as growth progresses. An individual carbon nanotube cannot stand on its own, so as one tube grows from the substrate, it touches another tube for support. This results in a network of tubes that contact each other via Van der Waals forces.

Silicone rubber only retains its viscoelasticity between –55 °C and 300 °C, but the new material remains flexible over a much higher temperature range. According to the researchers, the network is highly stable over a broad temperature range due to the energy dissipated as the individual nanotubes zip and unzip at the points of contact. The carbon nanotubes themselves are also very heat resistant between 2000 °C and 3000 °C so an even broader temperature range might be possible for this rubber. This rubber can recover its shape after being repeatedly deformed and has excellent fatigue resistance.

This material may find use in space vehicles, wrinkle-free textiles or viscoelastic shoe insoles that reduce mechanical shocks, cold interstellar space or inside a high-temperature vacuum furnace. These viscoelastic properties in the nanotube networks of the material can be tailored to create softer, stronger or more elastic materials and in other more down-to-earth applications.