MIT researchers have produced plastic with thermal conducting properties that might be exploited for removing heat away from computer CPUs. While the technique is experimental, it offers an alternative to methods that infuse plastic with materials to achieve similar properties.
In the movie “The Graduate,” Mr. McGuire had one word for
Ben Braddock (aka the very young Dustin Hoffman), just one word: “Plastics.”
Well, fast-forward 43 years to current times, and it turns
out plastics might be the definitive word when it comes to removing heat from
PCs and in other applications that require a material with thermal conductivity
but electrical isolation.
Unfortunately, we’re not talking about all plastics. The
plastic material that might help improve a PC’s energy efficiency has only been
produced in very limited quantities in the lab by researchers at MIT.
In particular, the MIT team 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 research was
reported in a Nature
Nanotechnology Letter published
earlier this month.
In addition to the conductivity boost, the process used by
the researchers 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’s CPU.
Alignment Is the Key
The trick to achieving the material’s interesting thermal
conductivity properties has to do with the way the plastic is formed. In a
two-step process, researchers developed a technique to slowly draw a thin-thread,
polyethylene fiber out of a solution. The polymer is then heated again to
stretch it further.
Using this process, polymer molecules line up within the
material. In contrast, when this material is normally formed, these molecules
have a structure that resembles a chaotic tangled mess.
Conductive plastic’s aligned polymer molecules
(left) vs. non-conductive plastic’s jumbled molecules (right). Source: MIT
This alignment of the polymer molecules results in a fiber about
300 times more thermally conductive than normal polyethylene along the
direction of the individual fibers, according to the MIT researchers.
The team noted that 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
equipment.
The researchers noted that the high level of conductivity
distinguished this material from other thermally conductive plastics being
developed using other techniques. For instance, some work in this field has
centered on adding other materials, such as carbon nanotubes, to the mix.
However, these materials have achieved only modest increases in conductivity
because the interfaces between the two kinds of material tend to add to thermal
resistance. The MIT researchers noted that the interfaces scatter heat, thus
limiting the improvement.
With this new method developed to draw fibers out of a
solution, the material’s conductivity was enhanced so much that it was actually
better than that of about half of all pure metals, including iron and platinum.
Moving Forward
The results achieved so far already represent the highest
thermal conductivity ever seen in any polymer material, according to MIT.
Already, the degree of conductivity they produce, if such fibers could be made
in quantity, 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 (like the
coils on the back of a refrigerator or in an air conditioner), cell phone
casings or 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.
So far, the team has just produced individual fibers in a laboratory setting.
The challenge going forward is to scale production up to what the researchers
call “a macro scale,” which will allow the production of sheets of material
with the same properties.
One direction flowPosted on: 03-17-10 | By: annon1The flow of heat only in one direction is truly interesting. I could see that being very useful in a number of applications.
DefinitelyPosted on: 03-17-10 | By: Salvatore SalamoneThis material could be used in data center products that suffer for overheating today.
The real issue is whether this technique the researchers developed can produce larger quantities and produce them economically.
Data center applicationsPosted on: 03-17-10 | By: Michael SteinhartCould this kind of plastic be built into blade server chassis and racks to keep those cooler, too?
A user comment on this articlePosted on: 03-17-10 | By: BillTeeI could also see this being applied to automotive technology, aerospace, military, etc.
