What Material Conducts Heat Best Science Experiment
Researchers have made thin polymer films that conduct heat better than many metals and ceramics. The material can be used to dissipate and dissipate heat in electronics, industrial equipment and automobiles.
A team of engineers from Massachusetts Institute of Technology has been able to dramatically change the properties of a standard polymer insulator. They originally created thin polyethylene fibers that conduct heat 300 times better than regular polyethylene. However, it soon became clear that for the practical application of the material in various fields, it must look like thin sheets.
The problem is that the structure of most polymers consists of intertwined molecular chains, which are excellent at trapping heat. This determines their insulating properties..
In order to get rid of these knots, the scientists dissolved polyethylene powder in a special solution in which the spiral chains expand and unravel. Further, using a specially designed system the mixture was applied to a plate cooled with liquid nitrogen. The result was a thick film that was then placed on a wire drawing machine, where it was heated and stretched until it became thinner than regular polyethylene..
During tests, it was found that the specific thermal conductivity of the new polymer is 60 W / (m ∙ K). For comparison for steel, this indicator is 15, and for ceramics 30. The resulting material conducts heat only along the length of the fibers. This unidirectionality can be used to divert energy only in the right direction inside laptops or mobile phones..
By studying the structure of the new film using X-rays, the researchers confirmed that the unusually high thermal conductivity is due to the lesser degree of coiling in the chains. Therefore, in the future, the team will continue to improve the manufacturing technology and will experiment with different types of polymers..
The image on the left shows an accumulation of molecular chains, and on the right, straight strands that conduct heat well.
Ideally, the film will be able to dissipate heat more efficiently in any direction. If scientists manage to make such a polymer, then it could potentially replace many existing heat-conducting materials. Manufacturers of heat exchangers, computer equipment and racing cars are already interested in the development..
Recently scientists also developed a technology for the production of transparent and lightweight polyethylene films, which are close to aluminum in terms of strength and elasticity.
text: Ilya Bauer, photo: MIT, alicdn