Styrene butadiene rubber (SBR) is the outcome of synthetic rubber research that took place in the United States and Europe under the impact of the shortage of natural rubber during World Wars I and II. In 1929, a German chemist developed a series of synthetic elastomers by copolymerization of two compounds (styrene and butadiene) in the presence of a catalyst. The first step involved in the process is to let styrene and butadiene react together. The new synthetic rubber that was formed consists of about 25% styrene, with butadiene making up the rest, which in principle had the same properties as natural rubber. These rubber is considered to be the highest volume general purpose and the most common type of synthetic rubber.