The invention of neoprene

Materials World magazine
,
1 Apr 2016

This month in history, DuPont scientists invented a much needed synthetic rubber. Simon Frost writes and Ashley Cooper illustrates. 

What do the wetsuit, cable sleeves, camera case, structural bearings and tablet sleeve illustrated above have in common? They’re all made from the synthetic chloroprene rubber invented in April 1930 by scientists at DuPont, USA – neoprene.

The supply of natural rubber was stretched by the growth of the motor industry and the First World War, during which time an early form of the synthetic rubber polybutadiene, invented in 1910 by Russian chemist Sergei Lebedev, was put into production to meet the extra demand. After the conflict, natural rubber made up the overwhelming majority of supply once again, and Lebedev set about developing a more efficient and inexpensive production process. By 1926, he had worked out how to manufacture polybutadiene from potato-derived ethanol, in 1928 to use sodium as a catalyst, and in 1930 the first pilot plant was built in the USSR. In the meantime, the global price of natural rubber grew and several companies set about developing other synthetic alternatives. 

DuPont, the American chemical giant that would later introduce nylon, teflon and kevlar, was one such company. Under research director Elmer Keiser Bolton, a DuPont team attempted with little success to develop an acetylene-based rubber, influenced by findings of studies by Lebedev, German chemist Hermann Staudinger and DuPont’s own Wallace Carothers. In 1923, at a lecture given in Rochester, New York, Belgian chemist Father Julius Nieuwland of the University of Notre Dame, France, passingly referred to his recent discovery of a rubber-like material created in a reaction between divinyl acetylene and sulphur dichloride. Bolton was in the audience, and his ears pricked. Bolton and Nieuwland made patent agreements and a 28-strong team of DuPont scientists, led by Carothers, took over the commercial development of Nieuwland’s discovery. 

Divinyl acetylene rubber was found not to retain its elasticity, so DuPont turned to the gas, monovinyl acetylene. At Nieuwland’s suggestion, they treated it with hydrogen chloride, creating a thin, clear liquid they named chloroprene. When polymerised, an elastic material similar to vulcanised rubber, but resistant to degredation by oil, sunlight and air and without the need for vulcanisation using sulphur, was created. They called it DuPrene, but dropped the trademark in 1937 in favour of the generic, and now widespread, neoprene.