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Leo Baekeland and the Invention of Bakelite

Posted by petar krastev on

By 1899, the invention of Velox photographic paper had already made Leo Baekeland a wealthy man. At his Snug Rock estate in Yonkers, New York, he maintained a home laboratory where he and his assistant, Nathaniel Thurlow, involved themselves in a variety of projects.

Like other scientists of their day, Baekeland and Thurlow understood the potential of phenol-formaldehyde resins. The chemical literature included reports written decades earlier by the German chemist Adolf von Baeyer and by his student, Werner Kleeberg. Von Baeyer had reported that when he mixed phenol, a common disinfectant, with formaldehyde, it formed a hard, insoluble material that ruined his laboratory equipment, because once formed, it could not be removed. Kleeburg reported a similar experience, describing the substance he produced as a hard amorphous mass, infusible and insoluble and thus of little use.

In 1902, German chemist Adolf Luft patented a resin made by modifying Kleeburg's composition in the hope that it could compete commercially with celluloid. At least seven other scientists tried phenol and formaldehyde combinations in their attempt to create a commercially viable plastic molding compound. But no one was able to create a useful product.

Hoping to capitalize on shortages of naturally occurring shellac—used to insulate electrical cables in the early years of the 20th century—Baekeland and Thurlow, as well as several other investigators, were experimenting with soluble resins. (Shellac was made from a resin secreted by the East Asian lac bug; it was harvested by the labor-intensive process of scraping the hardened deposits from the trees these insects inhabited.) Eventually, they developed a phenol-formaldehyde shellac called Novolak, but it was not a commercial success. By the early summer of 1907, Baekeland changed his focus from trying to create a wood coating to trying to strengthen wood by actually impregnating it with a synthetic resin.

On June 18, 1907, Baekeland began a new laboratory notebook (now in the Archives Center of the Smithsonian's National Museum of American History) documenting the results of tests in which he applied a phenol and formaldehyde mixture to various pieces of wood. An entry made the following day states:

All these tests were conducted in concentrated horizontal digester and the apparatus was reasonably tight. Yet the surface of the blocks of wood does not feel hard although a small part of gum that has oozed out is very hard. I began to think that the formaldehyde evaporates before it can act and that the proper way would be to impregnate with the viscous liquid which is obtained by boiling CH2O+C6H5OH together without a catalytic agent. In order to determine in how far this is possible I have heated in sealed tubes a portion of this liquid so as to determine whether there is a further separation of H2O or whether this is simply a solution of the hard gum in excess of phenol, then by simple open air evaporation I shall be able to accomplish hardening while I shall not succeed in closed sealed tubes.

I have also heated an open tube rammed with a mixture of asbestos fiber and liquid.

Also a sealed tube rammed with mixture of asbestos fiber and liquid. Everything heated 4 hours at 140° C -159° C.

The notebook description of the last experiment of that day states:

Asbestos + A in sealed tube. I found tube broken perhaps in irregular expansion but the reactions seems to have been satisfactory because the resulting stick was very hard and below where there was some unmixed liquid A there was an end (?) of solidified matter yellowish and hard and entirely similar to the product obtained by simply heating A alone in sealed tube. This looks promising and it will be worth while to determine in how far this mass which I will call D is able to make moulded materials either alone or in conjunctions with other solid materials as for instance asbestos, casein, zinc oxid (sic), starch, different inorganic powders and lamp black and thus make a substitute for celluloid and for hard rubber.

A day later, Baekeland listed four different products, designated A, B, C, and D. Substance D was "insoluble in all solvents, does not soften. I call it Bakalite (sic) and it is obtained by heating A or B or C in closed vessels." Baekeland later decided that "C" and "D" were equivalent.

The key to reaching the final product "C" from "A" or "B" were machines that subjected earlier stages to heat and pressure. Baekeland called these machines "Bakelizers."

Baekeland made the first public announcement of his invention on February 8, 1909, in a lecture before the New York section of the American Chemical Society. Previous reactions had resulted in slow processes and brittle products, he said; then he continued "...by the use of small amounts of bases, I have succeeded in preparing a solid initial condensation product, the properties of which simplify enormously all molding operations..."

Baekeland's first patent in the field had been granted in 1906; in all, he took out more than 400 patents related to the manufacture and applications of Bakelite. He started semi-commercial production in his laboratory and, in 1910, when daily output had reached 180 liters, (most of it for electrical insulators), he formed a U.S. company to manufacture and market his new industrial material. By 1930, the Bakelite Corporation occupied a 128-acre plant at Bound Brook, New Jersey.