Butyl Rubber – From Tires to Chewing Gum
Butyl rubber is another one of the synthetic rubbers, and is a copolymer of isobutylene and isoprene. It is impermeable to air, has high dampening characteristics, and high resistance to ozone and heat ageing. It is used in the manufacture of adhesives, fiber optic compounds, caulks and sealants, gasoline/ diesel fuel additive, mounts, and even in chewing gum!
Due to its impermeability, it is used in many applications requiring an airtight rubber. The first major application of butyl rubber was tire inner tubes, and tire inner liners are by far, the largest application for butyl today.
Its vibration dampening characteristics make a very good choice for body mounts, and can be formulated to have an intermediate level of oil resistance, so it can be used in engine and transmission mounts.
Bromine or chlorine can be added to the small isoprene fraction of the butyl to make bromo-butyl or chloro-butyl (known as halobutyls). The properties of these are similar to regular butyl, but they can be cured more rapidly, and with different and smaller amounts of curative agents. As a result the bromo-butyl and chloro-butyl can be co-cured with other elastomers.
Butyl was first produced by American scientists William Sparks and Robert Thomas at the Standard Oil Company. During World War II, butyl was known as GR-I, for Government Rubber – Isobutylene. Today, the majority of butyl rubber is produced by just two companies, Exxonmobil (the successor to Standard Oil), and Lanxess AG, of Germany.
Some of the specific applications include an additive in lubricating oils and motor fuels, as a binding agent in explosives such as C-4, bladders in sporting balls such as footballs, rubber roofing, gas masks because of its impermeability to gases, medical stoppers, and chewing gum. Most chewing gum uses food-grade butyl as the central gum base, which contributes to the gum’s elasticity, and also an obstinate, sticky quality.
Remember, Stern Rubber is always available to help with your material selection. Check out the engineering resources section for more information on materials, which includes a material selection guide.
So, the next time that you are chewing gum, remember that what you are chewing on, is also found in the tires on your car!