SILICA AEROGELS 5 0 0 billion particles per cubic inch produce remarkable physical structure which enables aerogels to kill weevils, flat varnishes, or thicken liquids wdth equal ease HE STORY of aerogels begins in the
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early thirties with a brilliant experiment by Dr. S. S. Kistler. Working in the laboratory, he produced gels unlike any ever made. Gels in which air replaced water. With them, he clearly proved that water is not an integral part of gel structure. And he named the new materials aerogels. There the story should end. Aerogels were only part of the experiment. They were difficult to make. They were expensive. They would soon be forgotten. But it didn't turn out that way, for one important reason — physical structure. As the first commercial producers of a silica aerogel—we call it Santocel — we found its structure worth a lot of trouble to obtain. And we did have trouble. W e had to find a production method which would (a) wring the water out of the silica hydrogel, (b) replace the water with air, and (c) still allow no shrinkage in volume. (We finally did it, but how is another story for another time.) The structure itself, when first studied, reminded one of our workers of Churchill's phrase about "a riddle wrapped in a mystery inside an enigma." We finally picture Santocel (see photograph) as a tenuous webbing of microscopic filaments which envelop thousands of minute air cells. This means Santocel has a remarkably large surface area, is chemically inert, highly porous and incredibly light. We've found this structure ideal for some unusual jobs. In thickening, for example, Santocel is extremely effective for altering the viscosity of nonpolar liquids. This has made it worthwhile as a thickener in printing inks, resins and various pastes. Santocel is also versatile in other ways. Laboratory tests show that it has the lowest thermal conductivity of any known substance. This makes it ideal for extremely low temperature insulation in liquid oxygen plants and similar applications, where it saves up to 50% on insulation space. Santocel does other things, too. It is a flatting agent for varnishes and lacquers; a grinding aid for powdery materials; an anticaking agent for insecticide dusts;
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S T R U C T U R K O F S I L I C A ARROCEL shown in Horiron p h o t o m i c r o g r a p h consists of p r i m a r y particles of B-Crystobalile. a b o u t 8 Angstroms in d i a m e t e r . T h e s e chain together to form " a tangled brush p i l e " of interlocked fibers a n d give t h e gel its u n u s u a l properties.
and a mold lubricant. It can even act as an insecticide in nonfood grains and kill weevils and other insects by abrading the coating of their cuticle. Moral of our story: in all of these applications the unusual properties of San-
tocel perform unusual jobs. Perhaps these same properties can now help solve the processing or product problem facing you. For more information why not send in the coupon? Santocel may be what you've been looking for. Santocel: Reg. U.S. Pat. Off.
MONSANTO CHEMICAL COMPANY
Department C-2 Inorganic Chemicals Division 1700 South Second Street St. Louis 4 , Missouri Gentlemen:
Serving Industry... Which Serves Mankind
Please send booklet, "Industrial Applications for SANTOCEL." I am interested in Santocel for Name
Title.
Company Street City
AUGUST
..Zone..
2,
1954
. .State..
3059
