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| Cellulose |
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| They called the result
celluloid. It would eventually be used not only to replace ivory
as the material for billiard balls, but also for making combs,
brushes, photographic film, shirt collars and
false teeth. |
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| After rubber came cellulose, a major component of all vegetable matter, especially of cotton. Before the middle of the 19th century, chemists had discovered that cotton dipped in nitric acid produced an explosive material, nitrocellulose, and an even better one if sulphuric acid was mixed with the nitric acid. That led to a product called guncotton that was added to gunpowder in the 1860s. Soon after, two printers in Albany, New York, found that by dissolving nitrocellulose in camphor it became mouldable under heat and pressure. They called the result celluloid. It would eventually be used not only to replace ivory as the material for billiard balls, which had been the printers’ aim, but also for making combs, brushes, photographic film, shirt collars and false teeth. |
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| In 1892 a trio of English chemists dissolved cellulose in ammonia in which a copper salt had been dissolved. They called that solution "viscose", and the silk-like fibre they recovered from it "rayon". By 1895, the British company Courtaulds was producing rayon commercially. |
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| Shortly before World War One broke out in 1914, two Swiss brothers, Camille and Henri Dreyfus, began producing lacquers and plastic film out of cellulose nitrate. Then they tried to produce continuous filament from it.When they eventually succeeded, they took the next train out of Basle for England. The war was still on, and they rightly reasoned there would be good money in selling their non-flammable lacquer as dope for the fabric that then covered aircraft wings. When the war was over, they began developing the continuous filament side of the business, naming their "artificial silk" Celanese (cellulose + ease of care). |
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| Out of cellulose, too, came a transparent film, the dream of another Swiss chemist who had been looking for a way to make natural textiles impervious to dirt and stains. He sold his patent rights to the US company, Du Pont, which marketed the film as cellophane. |
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| Unlike these man-made materials, those termed "synthetic" result entirely from laboratory experiments in manipulating and reacting the molecules of different compounds to achieve new molecular compositions. When it comes to the plastics that resulted from these experiments, the first successes were in what are called thermosets. When the plastic resin has been put in a mould and subjected to heat, then cooled and removed from the mould, subsequent heating will not soften it, as it will with the other category, known as thermoplastics. |
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| The first thermoset was produced early in the 20th century by
Dr Leo Baekeland, a Belgian living in Yonkers, New York. It was
a resin formed from phenol reacted with formaldehyde;
Baekeland called it Bakelite. It was not only mouldable and impervious to heat, but also non-absorbent and a poor
conductor of electricity. These qualities would see it used
eventually for a wide range of products, from moulded
electrical parts and insulating varnishes to table tops, gear
wheels and pump housings. |
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| A British company, British Cyanides, decided to replace the
phenol with either of two other organic compounds, urea and
melamine, to make a resin that would be free of Bakelite’s
odour. It called the result "Beetle", changed its own name to
British Cyanamid and licensed a US company, American
Cyanamid Company, to produce it, too. |
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| Thermosetting plastics offered little versatility, however, so in
the early 1930s research chemists began looking more closely at
what potential lay in thermoplastics. That required abandoning
their scepticism towards revelations coming out of Europe. |
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| Nineteenth-century scientists had calculated that certain
natural substances were composed either of enormous
molecules - starch molecules, they reckoned, had molecular
weights of 40 000: that is, weighed 40 000 times as much as
one hydrogen atom - or of many smaller ones that were
somehow held together in clusters or networks. The latter
theory was dismissed when, in the 1920s, the Swedish scientist
Theodor Svedberg invented a device he called an
ultracentrifuge, which could generate a centrifugal force
hundreds of thousands of times greater than gravity. The
machine, which helped him win a Nobel Prize for Chemistry in
1926, enabled him to determine with great precision the
molecular weights of highly complex substances. Single
molecules, he reported, could consist of hundreds of thousands
of atoms and thus have molecular weights of 1 000 000. |
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