Encyclopedia entry

Silicone (circa 1901)

         Silicone is a generic term denoting compounds which have a backbone of alternating silicon and oxygen atoms with additives hanging off the silicon atoms as pendant groups. Silicon and oxygen are the two elements in greatest supply on the Earth's crust.
         Silicon was first isolated by J. J. Berzelius in its amorphous state in 1824. In 1854 Deville obtained it in crystalline form. Charles Friedel researched silicon compounds as part of his search for synthetic diamonds. By 1863 Friedel and his partner James Craft had produced the first organosilicon compound. Alfred Stock, Albert Ladenburg and A. Polis all conducted research into carbon-silicon bonds. It was not until Victor Grignard had discovered Grignard reagents, organomagnesium compounds, that Frederic Stanley Kipping prepared a silicone. He used the Grignard reagents in the preparation of his first silicone. While there is some doubt as to whether he was the very first to form a silicone, he was the first to use the term.
         Kipping was a Scottish chemist born in Manchester, England on August 16, 1863. He Attended Owens College in Manchester and graduated with a chemistry degree. He then moved on to the University of Munich and worked in Baeyer's laboratory as a graduate student. He received his doctorates from the University of Munich and the University of London in 1887. He taught at the Heriot-Watt College, the Imperial College of Science and Technology, and at the University of Nottingham. Kipping retired from teaching in 1936 and continued his research. He died in England on May 1, 1949.
         His use of Grignard reagents to form silicones led him to further research the compounds. He conducted many experiments trying to synthesize a double bonded silicone compound. He never succeeded , but he published more than fifty papers on silicones which laid the foundation for the industry which even today manufacture over 500,000 tons of silicone for use in a wide range of products.
         It was not until the 1940's that silicone industry was able to make use of Kipping's research. In 1940 E.G. Rochow, a chemist with the General Electric Company discovered an easy way to form silicones. He combined methyl chloride gas and heated silicon and copper to form compounds with silicon-carbon bonds. Earlier research by Kipping proved that these compounds could be reacted with water to form silicones. Rochow's discovery and the pressure of World War II led to a silicone boom. General Electric, Dow-Corning, Union Carbide, Stauffer Chemical, Wacher-Chemie, Farbenfabriken Bayer, A. G. all began large scale silicone production within ten years of Rochow's discovery. Other companies soon followed their lead. Further research by James F. Hyde of Dow-Corning lead to the production of silicon rubber. Silicone rubber is particularly useful because it useful temperature range is -178 degrees F. (-117 degrees C.)to 600 degrees F. (315 degrees C.).  The range of natural rubber is -60 degrees F (-51 degrees C.) to 180 degrees F. (82 degrees C.)
         Silicones played a part in the war effort. Electronic equipment, radios and aircraft spark plugs, were waterproofed with silicones. Silicone rubber was used in gaskets for searchlights, and superchargers in aircraft engines. 
         Silicones are found in thousands of applications. They are used primarily as release agents, lubricants and sealants. Silicone treated fabrics, bricks, and concrete walls resist water. The silicones in paints give them improved weatherability. They are used as electrical insulation and oven and aircraft door gaskets. Silicone rubber is used in high temperature applications and left footprints on the moon when it was used in the boot soles of astronauts. Most of silicone produced is used in paper and textile applications, about a fourth is used  in electrical/ electronic products. The remaining silicone is divided between construction, automobile, office equipment, and food and medical applications. Silicones owe their great strength and stability to the unique characteristics of the silicon-oxygen bond.