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Flexible, high-strength polymer aerogels deliver "super-insulation" properties

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September 27, 2012

Flexible sheets of NASA's new polymer aerogel. A sheet this thick would provide thermal in...

Flexible sheets of NASA's new polymer aerogel. A sheet this thick would provide thermal insulation equal to about an inch (25 mm) of foam insulation (Photo: NASA)

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Often called "frozen smoke", aerogels are among the amazing materials of our time, with fifteen Guinness Book of World Records entries to their name. However, despite their list of extreme properties, traditional aerogels are brittle, crumbling and fracturing easily enough to keep them out of many practical applications. A new class of mechanically robust polymer aerogels discovered at NASA's Glenn Research Center in Ohio may soon enable engineering applications such as super-insulated clothing, unique filters, refrigerators with thinner walls, and super-insulation for buildings.

First synthesized in 1931, aerogels were the result of a bet between two chemists. Knowing that jellies are mostly pectin gelled with water, they challenged each other to remove the water without shrinking the jelly. Now aerogels are among the least dense solids, possess compressive specific strength similar to aerospace grade graphite composite, and provide the smallest thermal conductivity for any solid. With this array of amazing properties, why don't we see more aerogel applications?

Mary Ann B. Meador, Ph.D., a chemist at NASA Glenn, explains that despite these amazing properties, traditional aerogels made from silica (silicon dioxide, or beach sand) are brittle, and break and crumble easily. Not so when newer polymer aerogels are considered. Meador and her team have developed a particularly encouraging form of polymer aerogel, which is strong, flexible, and robust against folding, creasing, crushing, and being stepped upon. Their new class of polymer aerogels won a 2012 R&D100 award.

“The new aerogels are up to 500 times stronger than their silica counterparts,” says Meador. “A thick piece actually can support the weight of a car. And they can be produced in a thin form, a film so flexible that a wide variety of commercial and industrial uses are possible.”

So just how did Meador and her colleagues approach the problem of synthesizing robust, flexible aerogels? Early attempts to produce stronger and more durable aerogels focused on taking a silica aerogel, and depositing a thin layer of a polymer on the surface of the aerogel structures. This can be done using chemical vapor deposition, for example, but the process is quite slow. (Such coating can also be accomplished by putting a silica aerogel in a small container with a pool of super glue, just as exposure to superglue vapors can reveal fingerprints by coating their grease.) In addition, most of the polymers that could be deposited in this manner have rather low melting temperatures, whereas many of the potential applications require some degree of thermal tolerance.

A new idea was called for. As the only role of the silica aerogel was to give shape to the conformal polymer coating, why not see if a polymer aerogel can be directly formed? Polyimides such as Kapton generally show resistance to temperatures of 400 C (750 F) or higher, are structurally very strong, and have high glass transition temperatures, so were an obvious candidate for such applications.

Unfortunately, standard methods for forming aerogels ran into serious problems. When polyimides in a dilute solution were gelled and then subjected to supercritical drying, the gels shrank by up to 40%, leading to unacceptably dense materials. A number of variations have been tried, primarily based on altering the properties of the polyimides with a range of additives, but these were unsatisfactory in various ways.

The NASA group tried a cross-linking approach, where linear polyamides were reacted with a bridging compound to form a three-dimensional covalent polymer. Such polymers are far more stiff than linear polymers, rather like an I-beam compared to a solid round rod of the same weight. They formed the gel at room temperature, and were able to achieve virtually total coupling between the various three-dimensional polymers. When this gel was subjected to supercritical drying, they were able to form polymer aerogels with densities as small as 0.14 g/cc and having 90% porosity – far from a record, but light enough to provide useful properties such as very low thermal conductivity.

Scanning electron micrograph of the nano-sized cell structure of NASA's new polymer aeroge...

The above micrograph of the nanocellular structure of the aerogel shows pores averaging about ten nanometers in size. A quarter-inch (6 mm) sheet of this aerogel would provide as much insulation as three inches of fiberglass.

The new class of polymer aerogels also have superior mechanical properties. For example silica aerogels of a similar density have a resistance to comperession and tensile limit more than 100 times smaller than the new polymer aerogels.

A Smart car parked on top of a thick piece of NASA's new polymer aerogel (Photo: NASA)
A Smart car parked on top of a thick piece of NASA's new polymer aerogel (Photo: NASA)

Silica aerogels would crush to powder if placed under a car tire. As seen above, the same is not true of the new polymer aerogels, even if the car is only a Smart car. Overall, the mechanical properties are rather like those of a synthetic rubber, save that the aerogel has the same properties (and far smaller thermal conductivity) with only about 10 percent of the weight.

Applications in clothing as well as insulation of pipes, buildings, water heaters, and the like are enabled by these materials. Tents and sleeping bags can also benefit from the combination of light weight and thermal insulation. NASA is even considering the new polymer aerogels for use as inflatable heat shields. The practicality of many such applications will depend on the cost of polymer aerogel in commercial quantities. In any case, these types of products now have another dimension of design flexibility.

Source: NASA Glenn Research Center

About the Author
Brian Dodson From an early age Brian wanted to become a scientist. He did, earning a Ph.D. in physics and embarking on an R&D career which has recently broken the 40th anniversary. What he didn't expect was that along the way he would become a patent agent, a rocket scientist, a gourmet cook, a biotech entrepreneur, an opera tenor and a science writer.   All articles by Brian Dodson
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20 Comments

There are millions of applications for this technology. Outstanding.

Jeff Rosati
27th September, 2012 @ 07:00 am PDT

If it has enough compressive strength to hold up car... imagine making a spherical shell from it. The shell can be quite thick, since it doesn't weigh anything. Put it in a vacuum chamber to suck out all the air, then cover it with an air tight coating, like aluminized mylar. Presto: the ball floats on air; no helium required.

Put a few hundred two-meter balls on a frame with a motor and fan -- I've finally got my flying car!

piperTom
27th September, 2012 @ 09:33 am PDT

Sounds like I finally found the right insulation for cryogenic rocket propellant tanks. Than-you, NASA.

MBadgero
27th September, 2012 @ 11:02 am PDT

Way to go, NASA!

Sonya Jones
27th September, 2012 @ 11:02 am PDT

How about making a boat hull out of that stuff? Or a rocket or airplane fuselage? Think of how much more payload you could put up if you got rid of that dead weight!! Cars and trucks could get better fuel mileage, wind turbines could spin in less breeze and the list goes on and on!

Randy

Expanded Viewpoint
27th September, 2012 @ 12:07 pm PDT

You were comparing how well it insulates to fiberglass. Will this product be cheap enough to use as home insulation if made in bulk?

Joshua Young
27th September, 2012 @ 12:11 pm PDT

Super! Even if more costly, this has application whereever excellent insulation is needed but space is at a premium or unavailable.

Arf
27th September, 2012 @ 01:11 pm PDT

@Joshua - for home insulation, there's no real need for the enhanced strength this technology provides - all it has to do is sit inside a wall cavity, entirely unstressed. 'Standard' aerogel panels are just fine - take a look on alibaba.com where there are plenty of companies selling architectural aerogel insulation panels.

Synchro
27th September, 2012 @ 01:37 pm PDT

Finally, maybe a decent insulated coffee mug.

IggyDalrymple
27th September, 2012 @ 08:08 pm PDT

Areogel is also available in a "pellet" form. The standard 3 inch wall cavity has an R value of about 30 with them.

It is far more expensive than fiber glass but under some conditions may be well worth it.

If production costs can be brought down to less than 3 x fiberglass it will win out..

If the energy cost is low it will dominate, fiber glass formation uses an incredible amount of energy and until recently cost more energy to produce than it saved.

MikeFromHC
27th September, 2012 @ 10:33 pm PDT

These used to be touted as a spray-able replacement for Glass with far better insulative properties. Several houses were built using ferrocement and aerogels. have they gotten any further with the sprayable 'windows' side of the technology?

Kwazai
28th September, 2012 @ 08:25 am PDT

A small thing, but the weight and type of car are immaterial. It is only the PSI of the tire that matters.

As a hunter, I can see many uses for this product, smaller, lighter coolers with the same volume, but a higher R factor, thermal clothing of less weight and less heat loss, much lighter coffee thermoses , heated hunting blinds, much better boots and gloves.

kellory
28th September, 2012 @ 03:45 pm PDT

Better Insulation for Electric Vehicle Battery Packs - so less heating or cooling control and management is needed, with less thickness needed to do the job! Better Sound Proofing Too? - for vehicle floors, doors, firewalls, and other such things!

Also - Could be used for Fuel Tank Insulation on Fueled Vehicles to keep evaporation levels reduced!

Robert Brian Weekley
29th September, 2012 @ 11:37 pm PDT

Just imagine, a material so strong yet porous as could be; finally something to replace Dirt as a structural element. Could we be near the end of Leech-Lines?

Gus Peterson
1st October, 2012 @ 09:29 pm PDT

The future is awesome, and the possibilities keep growing :)

Brian McGee
11th October, 2012 @ 09:26 am PDT

wonderfully written article. Amazing work

Utkarsh Kumar
7th January, 2013 @ 03:17 pm PST

It would be a kewl way to make 'stained glass' windows.

I wonder if they'll be able to make a large vacuum balloon out of it at some time. Size of a semi trailer and lighter than air?

Kwazai
14th January, 2013 @ 09:58 am PST

Hopefully, NASA will work with a company that will only manufacture this in America. I am tired of gov. backed groups, including our universities, sending taxpayer developed technology to either foreign companies, or companies that will ship the work out of the nation anyways.

G Richard Raab
14th January, 2013 @ 12:25 pm PST

RE: Finally, maybe a decent insulated coffee mug.

Coffee shop downstairs at work uses these:

Fusion Cup from www.dart.biz

They are excellent (disposable) coffee cups. I used to think they were paper since the material is so thin but they seem to be a styrofoam of very hard, very small, very strong cells.

Dave B13
28th January, 2013 @ 09:42 am PST

Well written article... thank you. This could very well be used in my micro house that would give me back inches in my 'road legal' size micro house. Much valued inches, I might add.

Would you happen to know the compression strength and compaction % maximum per inch shrinkage... thank you

Brent Eagleson
7th March, 2013 @ 10:42 pm PST
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