The Right Chemistry: The Many Uses of Cellulose Acetate

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I am sometimes asked how the ideas for these columns come about. In this case, I was looking at a discarded overhead projector. This brought back memories of my first teaching experience in 1973, when all classrooms were equipped with such a device and we wrote on plastic sheets that we called “acetates”. I never thought of that term back then, but now that unwanted projector sitting in a dumpster somehow made me think of all the chemical reactions I used to write on those acetates. And some of them had to do with synthesizing that very substance. “Acetate” refers to cellulose acetate, a material that has played an important role in warfare, photography, fashion, packaging, and medicine.

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It all started in 1838 when the French chemist Anselme Payen isolated cellulose, the substance that forms the cell wall of plants. Then, in 1865, another French chemist, Paul Schutzenberger, reacted cellulose with acetic anhydride to form a sticky substance for which he found no use. But he did interest Camille and Henri Dreyfus, Swiss brothers who had received doctorates from the University of Basel. In 1904, they began experimenting with cellulose acetate in a shed in their father’s garden and discovered that it was soluble in acetone. When a thin layer of this solution was poured onto a surface, the acetone evaporated, leaving behind a sheet of plastic material. An idea was born immediately! Could this be a replacement for celluloid in photographic film that has been cursed with the problem of flammability?

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Now we need a bit of celluloid history. In 1832, Henri Braconnot combined wood fiber with nitric acid and unknowingly synthesized nitrocellulose, a highly flammable substance he named “xyloidine.” The German-Swiss chemist Christian Friedrich Schonbein found a more practical formulation for nitrocellulose in 1846 by treating cotton with a mixture of nitric and sulfuric acids. He enthusiastically wrote to Michael Faraday that he could mold this material into “all sorts of things and shapes”, but he did not pursue this. Schonbein was more interested in burning his “pyroxylin” without producing smoke, an observation that would lead to the production of smokeless gunpowder.

Then, in 1856, Alexander Parkes in England added camphor to nitrocellulose to produce “Parkesine”, the world’s first synthetic plastic. Almost simultaneously, a very similar formulation was devised by John Wesley Hyatt in the United States stimulated by a quest to win a $10,000 prize that had been offered by a billiard ball company to develop a substitute for ivory. It was Hyatt who coined the term celluloid for the new plastic.

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Celluloid had many uses, from replaceable collars and cuffs to combs and flexible photographic film, introduced by George Eastman in the 1880s. But all celluloid products had the same problem. They were highly flammable. Cellulose acetate was not, which is why the Dreyfus brothers thought of using it to replace celluloid in roll film. In 1912, they began producing acetate film, but then the fledgling aircraft industry got in the way.

The wings of early biplanes were covered with tarps that, when wet, created a problem for aviation. A waterproof coating with a cellulose acetate lacquer, called “dope”, solved the problem. Camille Dreyfus created the British Cellulose and Chemical Manufacturing Company along with a similar operation in the United States to make lacquer for aircraft wings. It also proved to be an excellent coating for the fabric used in the zeppelins being built in Germany.

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After the war, the Dreyfus brothers had another breakthrough. Passing a solution of cellulose acetate through tiny holes in a showerhead-like device produced a fiber suitable for weaving into a silky fabric that was widely adopted by the fashion industry. To manufacture the fiber, Camille Dreyfus founded the American Cellulose & Chemical Manufacturing Company in 1918 and then, in 1927, bought the Celluloid Company which had been founded by John Wesley Hyatt and his brother Isaiah. Dreyfus renamed it the Celanese Company of America with the Celanese name derived from “cel” for cellulose acetate, and “ese” because acetate fabrics were so easy to care for. Today, “acetate” still appears on many labels, often blended with silk, cotton, wool, or nylon to produce fabrics that have a soft feel, are wrinkle-resistant, and dry quickly.

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The Celanese Company was very successful and the Dreyfus brothers became very wealthy. When Henri died in 1944, his brother created a fund in his memory that was eventually renamed the Camille and Henri Dreyfus Foundation when Camille died in 1956. The foundation administers a series of awards intended to promote chemical research and education. chemistry. The biennial Dreyfus Prize recognizes a person who has achieved a breakthrough in chemistry through exceptional and original research and comes with a prize of $250,000. The inaugural prize in 2009 was awarded to Professor George Whitesides of Harvard, one of the most highly cited chemists in the world. He was recognized for his creation of new materials that have significantly advanced the field of chemistry and their social benefits.

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The Dreyfus brothers themselves would be worthy candidates for the prize, if they were still alive. Without a doubt, cellulose acetate has benefited society in many ways. Just think of all the elements that go back to those early experiments by Camille and Henri Dreyfus. Magnetic tape, reverse osmosis water filters, dialysis machine membranes, photographic “security film,” and of course, that roll of acetate that still stared sadly at me from that discarded overhead projector.

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Joe Schwarcz is director of the Office of Science and Society at McGill University (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3-4 p.m.