CASE WESTERN (US)—The same kind of freeze-drying process used to make banana chips is allowing researchers to create clay-based polymers. The foam-like materials can be molded into any shape and are environmentally friendly.
Called clay aerogel composites, the patented polymers were discovered by engineering professor David Schiraldi and his research group at Case Western Reserve University.
The polymers are inexpensive and can take on the shape and size of any container that can hold water—from ice cube trays to rubber ducky molds to clam-shell packaging molds that hold and ship electronics.
“This is cool stuff,” says Schiraldi.
When fired in a kiln-like furnace to 800 degrees centigrade, the material undergoes a chemical transformation. It can become a hard, lightweight ceramic. When mixed with latex, the clay and water mixture becomes a bendable material like rubber. If magnetic materials are included in the clay concoction, it becomes a super-lightweight magnet. Combined with the right materials, it can even be an electrical conductor or a catalyst for chemical reactions.
“The flexibility of the clay aerogel composites is amazing,” adds Schiraldi, who says that almost anyone can make the composites if they have pure clay in a form that resembles cat litter pellets, a blender, and a $50,000 freeze dryer.
The materials feel and act like foam, without the injection of gas bubbles or the use of environmentally unfriendly CFC blowing agents.
Recently, the group experimented with the composition by combining clay, water, and the milk protein, casein, found in waste water left over from making cheese. The result is a bio-based polyamide (a high-temperature polymer) with insulating properties to withstand heat at temperatures of 300 degrees centigrade.
Currently, oil-based polymer foam insulation degrades at high temperatures, says Schiraldi. Clay aerogel composites have the potential to insulate hundreds of miles of noninsulated piping carrying high-temperature materials throughout refineries.
But milk is not the only bio-based substance the group has used. The team has also experimented with the seaweed protein alginate used to thicken ice creams and materials from corn like corn starch, but so far casein has offered the best results.
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