Elmer Keiser Bolton - The Stevenson Act and Synthetic Rubber

The Stevenson Act and Synthetic Rubber

In the early 1920s the supply and demand of natural rubber became a concern in international trade. In November 1922 England enacted the Stevenson Act that was intended to protect rubber producers by restricting production. This caused a great deal of concern in the United States because an expanding supply of rubber was needed to support the growing number of automobiles in use. Bolton saw this as an opportune time to start research on synthetic rubber. However, research did not begin in earnest until 1925 when the high price of rubber was attracting considerable attention and other scientists such as Thomas Edison were also taking an interest in the problem.

Work on synthetic rubber began with the polymerization of butadiene obtained from the hydrogenation of diacetylene, and at first not much progress was made. At the end of 1925 Bolton met chemist Julius Arthur Nieuwland from the University of Notre Dame who had discovered a way to polymerize acetylene using a cuprous oxide catalyst. Unfortunately the resulting polymer would explode when struck, but Bolton believed the process could be modified to produce a stable compound that would replace butadiene in the reaction. Bolton brought Nieuwland into the project as a consultant to DuPont, and Nieuwland taught the DuPont chemists how to use his catalyst. A continuous-flow reactor was developed that would produce a good yield of the stable polymer Bolton was seeking. While the polymer was highly chemical resistant, it degraded with exposure to light.

In 1927 DuPont's Chemical Director C.M.A. Stine persuaded the company to take on a fundamental research project for synthetic rubber and received $250,000 in funding for this purpose. In 1928 Wallace Carothers, an instructor at Harvard University, was hired to lead the newly formed group. Bolton operated within this group and by 1929 had discovered that his polymer could be readily converted into 2-chlorobutadiene (chloroprene) with a copper catalyzed addition of hydrogen chloride. This material was both chemical and light resistant, with the properties of a synthetic rubber.

The new material was announced at the Rubber Division of the American Chemical Society on November 2, 1931, and was called Duprene (today it is called neoprene). By this time the Stevenson Act had been repealed and the Great Depression had begun. Rubber prices were low and the new material cost twenty times what natural rubber cost. Therefore it never became a substitute for natural rubber, but it did find commercial use in applications where a rubber compound was needed that was more resistant to oils and outdoor degradation. Applications of neoprene include: the Rigid-hulled inflatable boat; diving suits, and diveskins; gloves, balaclavas, sleepsacks, Knee high boots, wetsocks and other protective clothing; radar absorbent material; plumbing fixtures; gaskets, hoses, seals and belts; foam (mousepad, wetsuit); orthopedic braces; and solid fuel rocket propellant (see AGM-114 Hellfire).