Scientists transform polyethylene into a heat-conducting material

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Washington, March 8 (ANI): A research team from the Massachusetts Institute of Technology (MIT) has found a way to transform the most widely used polymer, polyethylene, into a material that conducts heat just as well as most metals, yet remains an electrical insulator.

The new process causes the polymer to conduct heat very efficiently in just one direction, unlike metals, which conduct equally well in all directions.

This may make the new material especially useful for applications where it is important to draw heat away from an object, such as a computer processor chip.

The key to the transformation was getting all the polymer molecules to line up the same way, rather than forming a chaotic tangled mass, as they normally do.

The team did that by slowly drawing a polyethylene fiber out of a solution, using the finely controllable cantilever of an atomic force microscope, which they also used to measure the properties of the resulting fiber.

This fiber was about 300 times more thermally conductive than normal polyethylene along the direction of the individual fibers, according to the team's leader, Gang Chen, the Carl Richard Soderberg Professor of Power Engineering and director of MIT's Pappalardo Micro and Nano Engineering Laboratories.

The high thermal conductivity could make such fibers useful for dissipating heat in many applications where metals are now used, such as solar hot water collectors, heat exchangers and electronics.

According to Chen, most attempts to create polymers with improved thermal conductivity have focused on adding in other materials, such as carbon nanotubes, but these have achieved only modest increases in conductivity because the interfaces between the two kinds of material tend to add thermal resistance.

"The interfaces actually scatter heat, so you don't get much improvement," Chen said.

But using this new method, the conductivity was enhanced so much that it was actually better than that of about half of all pure metals, including iron and platinum.

If such fibers could be made in quantity, they could provide a cheaper alternative to metals used for heat transfer in many applications, especially ones where the directional characteristics would come in handy, such as heat-exchanger fins, cell-phone casings or the plastic packaging for computer chips.

Other applications might be devised that take advantage of the material's unusual combination of thermal conductivity with light weight, chemical stability and electrical insulation. (ANI)

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