Heat conductive polyethylene
Polymers are generally put to work as insulators, but a team of researchers at MIT has devised a way to turn polyethylene -- the most commonly used polymer -- into a conductor that transfers heat better than many pure metals. But the conversion of insulator to conductor is only half of the breakthrough; by coaxing all the polymer molecules into precise alignment, the researchers have created a polyethylene that conducts heat in only one direction. The plastic material remains an electrical insulator.Getting a bunch of polymer molecules to fall in line is no easy task -- left to their own devices, the molecules will settle into a chaotic arrangement that is resistant to heat transfer. But the MIT team found that by drawing polyethylene fibers slowly out of a solution they could get the molecules to line up facing the same way, creating a material that will let heat pass in one direction but not the other.This kind of one-way conductor is ripe for myriad applications in devices where heat must be drawn away from a certain place, such as heat exchangers, computer processors or portable electronics. With a thermal conductivity 300 times greater than conventional polyethylene, the polymer is actually more conductive than about half of all pure metals, meaning it could potentially replace metal conductors in several common devices.Of course, all that is dependent on scaling the process to create conductive polyethylene at market-feasible prices and quantities, something the team has not yet done. But should they find a way to produce the stuff in bulk, it could quickly jump from lab bench to commercial applications, providing a cheap alternative to certain metals used in heat exchange -- metals that add cost and sometimes an environmental toll to common devices.
Source: popsci.comAdded: 19 March 2010