Today the word rubber communicates a broader meaning beyond its original definition, referring to the entire group of elastomeric materials or simply elastomers. The most renowned characteristic of elastomers are their high elasticity and low compression set. Natural rubber, after which the material is actually named, can arguably be credited as historically the most important type of rubber. Its primary source is latex, obtained or tapped from plants producing this milky organic liquid. It is believed that latex has many uses for the plant including storing nutrition, depositing waste and protecting the plant from any external harm. There are various kinds of plants producing latex. The most important one for obtaining rubber is Hevea brasiliensis, or the so-called rubber plant, originating from Amazon region in South America and accounting for almost entire production of natural rubber today. The latex is acquired by making an incision in the bark of a rubber tree and then processed afterwards to obtain natural rubber.
In 19th century seedlings of rubber plant were smuggled out of Brazil and sent to different corners of the world in search of suitable soil. Among many regions experimented British Malay, (modern day Malaysia) Indonesia and Thailand proved to be the best alternatives for rubber plantation. Today the three account for almost three quarters of the world production whereas Asia supplies 95 percent of the natural rubber harvested in the world.
First use of rubber by men is believed to go back as far as 1600 BC. Indigenous people of Central and South America played with elastic balls made of natural latex. They coated their clothes with some sort of liquid rubber to make them waterproof. Spanish and Portuguese domination of Americas in 16th century introduced the Old World to rubber. Until discovery of its main industrial uses in 19th century rubber was commercialized in a number of ways from pencil erasers to medical devices and from waterproof shoes to raincoats. No matter how it was utilized the biggest problem with unprocessed natural rubber happened to be its extremely weak resistance to heat and weathering. In high temperatures it melted away while in low temperatures it became as brittle as graphite. Life of latex-containing products tended to be very short, limiting wide use of rubber by manufacturing industries. Main reason behind this drawback is that the proteins contained with latex start to decay very quickly within a few days after extraction and oxygen in the air attacks the double-bonds within rubber, breaking them down and thus perishing the product. Despite all shortcomings of the natural rubber the demand kept increasing and the first rubber factory was opened in Paris in 1803, followed by few others. One of the important developments of the time worth of noticing was the commercial success of Charles Macintosh who using latex treated with naphtha produced waterproof coats, which later were named after him. In 1839 Charles Goodyear invented a process to treat raw rubber called vulcanization, which eventually became a breakthrough in the history of rubber. Vulcanization in brief is an irreversible process where the rubber is kept under a certain amount of pressure and heat for a certain period of time and cured with an agent (e.g. sulfur). As a result rubber does cross-linking with the cure agent and becomes a highly stable elastomeric material. Invention of vulcanization led to a rapid expansion in use of rubber and declared it as the number one preferred material for industrial sealing applications. The second biggest step with regard to development of seals came with the commercialization of synthetic rubber. Nations that lost access to natural rubber sources during wartime like Germany or the United States in WWII heavily supported efforts in synthesis of man-made rubber, which led to development of various rubber types over half a century. Synthetic rubber is a petroleum-based product and does not contain any organic latex but its mechanical behavior resembles that of natural rubber. Approximately 60 percent of rubber produced today is synthetic, while the remaining 40 percent is sourced from plantations. Most of rubber used for industrial seal manufacturing also comes from synthetic varieties since seals used for industrial applications constantly get in contact with oils and chemical fluids to which natural rubber offers very limited resistance if any at all