Synthetic Rubber
In the 1920s, the German government began developing processes to produce synthetic rubber, in order to decrease its dependence on foreign sources for natural rubber. Its first efforts with dimethylbutadiene resulted in inferior grades of rubber, but further research spawned the discovery of emulsion copolymerization of butadiene and styrene. The United States, facing a natural rubber supply crisis when supplies in Southeast Asia were cut off during World War II, established its own synthetic rubber research based on the earlier developments.
In 1940, the Rubber Reserve Company was founded, and the US government financed the construction of various styrene-butadiene rubber (SBR), butadiene, and styrene plants. The synthetic rubber produced in these facilities was called Government Rubber-Styrene (GR-S). However, the new synthetic rubber resolved the problem only partially, because it could be used for tire treads, but natural rubber was still required for sidewalls and for inner tubes. The US government under the Eisenhower administration privatized the synthetic rubber industry following the Korean War. As the synthetic rubber market developed, solution methods of polymerization were popularized. This led to the production of solution-polymerized polybutadiene in the early 1960s, which quickly became the second most widely used synthetic rubber (behind emulsion SBR).