CHF Polymers & People
"Of all critical and strategic materials, rubber is the one which presents the greatest threat to the safety of our nation and the success of the Allied cause. If we fail to secure quickly a large new rubber supply our war effort and our domestic economy will collapse. . . the rubber situation gives rise to our most critical problem."
-From the Baruch Committee Report to the President, 1942
The mathematization of the macromolecular world.
America's Paul Flory (left) developed a mathematical theory of the creation of polymer networks, in which polymer fluids form cross-links and become, like rubber, elastic. Flory's clear and precise explanations of polymer behavior over the next thirty years were honored in 1974 by a Nobel Prize in Chemistry. Photo courtesy of Joseph X. Labovsky.
Carothers was not the only American pioneer in polymer research. In the 1930s Du Pont's Paul Flory (1910-1985) utilized elegant statistical and kinetic considerations to explain the role of end groups in polymer formation. At the University of Illinois Carl Marvel (b. 1894) continued to initiate a legion of organic chemists into the mysteries of polymer behavior. The talents of such individuals were soon tested by one of the greatest challenges ever faced by America's chemical community: the mass production of synthetic rubber. In 1941 Japan bombed Pearl Harbor, bringing the United States into the agony of World War II. Japan seized control of much of Southeast Asia, overrunning the plantations in the Malay Peninsula and East Indies that supplied America with nearly ninety percent of its heavy demand for rubber. During a war remembered by many for its sacrifices and intense commitment at the home front, the thousands of chemists assigned to the Synthetic Rubber Project united to revolutionize our understanding of rubber and our understanding of polymer chemistry.
Commercial use of rubber had grown steadily following 1839, when American inventor Charles Goodyear (1800-1860) discovered vulcanization, a process that used varying amounts of sulfur to control the toughness and elasticity of natural rubber. In 1888, however, Scotland's John Dunlop (1840-1921) spurred the craze for bicycling and stimulated the demand for caoutchouc (natural rubber) by placing an air-filled rubber tube on his son's bicycle. Seven years later, the name Dunlop identified a twenty-five-million-dollar pneumatic tire business. The birth and boom of the automobile in America, led by the Model T, brought the center of world rubber consumption to the United States.
The great rise in demand for rubber made the search for a commercially viable synthetic product attractive long before the crisis of the 1940s. The Germans had experimented with making rubber from butadiene, a petroleum byproduct, using the metal sodium to initiate the polymerization of butadiene molecules. By 1930 they had developed two variants of these Bu-na (butadiene + Na or sodium) rubbers, in which butadiene linked in a chain with either styrene (Buna-S) or with acrylonitrile (Buna-N).
The troubled international climate of the late 1930s put the American government on notice that it should take steps to protect its own rubber future. Discussions began between Washington officials and industry executives concerning the joint administration of a synthetic rubber program. Approval of the Rubber Reserve Company came just months before Pearl Harbor. The program called for the construction of four plants, each with the capacity for 10,000 tons per year of GR-S (Government Rubber-Styrene), a general purpose rubber similar to Buna-S. Production of this modest amount would have been impressive: no American company had ever produced more than 6,000 tons of a synthetic rubber in any previous year.
The Beckman IR-1 spectrophotometer. Photo courtesy of Beckman Instruments, Inc.
An initial obstacle to the mass production of GR-S rubber lay in the separation of one of its components, butadiene, from other refinery gases. Traditional methods for analyzing refinery gases were far too time-consuming. University laboratories successfully speeded up the process of identifying the distinct spectra each gas emitted after absorption of specific wavelengths of infrared radiation. The first instruments used to measure these "rainbow" signatures were handmade in the laboratory. Different instruments often gave quite varied results. Officials of the Rubber Reserve stepped in to insure a standard design in all its production labs. Only with uniform ingredients could the many rubber factories produce a GR-S of consistent quality. Shell Development Company built a prototype analyzer, and in 1942 Beckman Instruments produced the first commercial infrared spectrophotometer, the IR-1.
In December 1941 the Rubber Reserve Company was ordered to triple its planned production to 120,000 tons. Within six months the War Production Board had raised the goal to a daunting 850,000 tons. Available butadiene supplies were limited. The only commercial source of the chemical was the petroleum and natural gas industry, which produced butadiene from butylene and butane. Yet these two distillates were already sought by another emergency group creating new high-octane aviation gasolines, the superior engine performance of which had proved invaluable for British survival in the Battle of Britain.
The petroleum industry and the War Production Board worked with great speed, accommodating both demands for distillates in a matter of months. A potentially greater obstacle appeared on the political horizon, however. In the summer of 1942 Grain Belt legislators, knowing that butadiene could be produced from ethyl alcohol, obtained congressional passage of a bill that demanded an increased supply of rubber manufactured from alcohol produced from agricultural or forest products." The political squabble over the choice of alcohol or petroleum feedstocks was settled only with the September 1942 report of the Rubber Survey Committee, a three-member commission appointed by President Franklin D. Roosevelt. The Baruch Report, as the document became known, made evident the dimensions of the rubber crisis and called for the maximum utilization of both petroleum and alcohol byproducts. Roosevelt created the Office of the Rubber Director to coordinate the use of all major types of synthetic rubbers: GR-S copolymers, butyl rubber, and neoprene. To the Rubber Directors, William M. Jeffers (1876-1953) and, later, Bradley Dewey (1887-1974), fell the challenging task of mobilizing twenty-four plants, twenty thousand workers, and over half-a-billion-dollars worth of machinery.
"Victory... will ride on the rubber you save."
-Popular slogan during the war
The myriad technical problems of scaling up GR-S production required unusual creativity for their solution Chemists and chemical engineers in the petroleum and rubber industries worked with academics at such leading institutions as the Universities of Chicago and Illinois. Analytical chemists in New Jersey gave quality control advice to manufacturers in California. Success came as it was found that the trickiest problems can often have the most elegantly simple solutions--if you know whom to ask.
Bell Laboratories was one of the places with the most experience in studying the molecular properties of rubber. Work on synthetic rubbers had begun there in the late 1930s in the hope of making these rubbers suitable for use as insulation for telephone cables. In 1943 William O. Baker (b. 1915) began serious investigation into the relation of two physical states of rubber, sol and gel, to the final rubber product. Sols are rubbers with a normal amount of cross-linkages between molecules; gels have more than their share of cross-links, often in three dimensions, and are very rigid. Baker discovered that the high temperatures used in factory drying of rubber, which made the rubber more workable, were splitting molecular chains and producing more gel. The lack of proper control over the reactions and the drying led to "tight rubber," with too high a gel content and unsatisfactory properties in the final product. Although Baker met initial resistance from manufacturers used to traditional drying methods, he succeeded in getting companies to use his techniques for monitoring and limiting gel content. Baker later played a key role in eliminating much of the variation in the styrene content of GR-S rubbers.
In 1942 production of synthetic rubbers reached 20,000 tons. At the end of 1943 the Project had turned out over 200,000 tons. By 1945 the United States' annual production was more than triple that amount. The product, and the companies which created it, had become wartime giants.
Cooperation among businesses was encouraged by the government's relaxation of patent and antitrust laws as well as by industry's strong commitment to the goal of independence from rubber imports. The success of the Synthetic Rubber Project showed that an exchange of methodologies, trade techniques, and analytical apparatus was critical to overcoming the problems of commercial production of synthetic rubber. The Project was a perfect example to invoke when scientists argued that an interdisciplinary approach was needed to understand and utilize other polymers. In 1946 the pioneer polymer researcher Herman Mark, who had been forced to leave Nazi occupied Austria in 1938, founded America's first polymer research institute at Brooklyn Polytechnic Institute. The secrets of polymer behavior and formation became open to sustained investigation.
ABOUT THE CHEMICAL HERITAGE FOUNDATION
© 2000 CHEMICAL HERITAGE FOUNDATION