Butyl rubber

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Butyl rubber gloves

Butyl rubber, sometimes just called "butyl", is a

viscoelastic
material. It is generally odorless and tasteless, though it may exhibit a slight characteristic odor.

Properties

Butyl rubber has excellent impermeability to gas diffusion, and the long polyisobutylene segments of its polymer chains give it good flex properties.

The formula for PIB is: –(–CH2–C(CH3)2–)n–

The formula for IIR is:

It can be made from the

cationic addition polymerization
.

A synthetic rubber, or

fuel additive, and chewing gum. The first major application of butyl rubber was tire inner tubes
. This remains an important segment of its market even today.

History

Isobutylene was discovered by Michael Faraday in 1825. Polyisobutylene (PIB) was first developed by the BASF unit of IG Farben in 1931 using a boron trifluoride catalyst at low temperatures and sold under the trade name Oppanol B [de]. PIB remains a core business for BASF to this day.

It was later developed into butyl rubber in 1937, by researchers

Robert M. Thomas, at Standard Oil of New Jersey's Linden, N.J., laboratory. Today, the majority of the global supply of butyl rubber is produced by two companies, ExxonMobil (one of the descendants of Standard Oil) and Polymer Corporation, a Canadian federal crown corporation established in 1942 to produce artificial rubber to substitute for overseas supply cut off by World War II. It was renamed Polysar in 1976 and the rubber component became a subsidiary, Polysar Rubber Corp. The company was privatized in 1988 with its sale to NOVA Corp which, in turn, sold Polysar Rubber in 1990 to Bayer AG of Germany. In 2005 Bayer AG spun off chemical divisions, including most of the Sarnia site, creating LANXESS AG, also of Germany.[1]

PIB homopolymers of high molecular weight (100,000–400,000 or more) are polyolefin elastomers: tough extensible rubber-like materials over a wide temperature range; with low density (0.913–0.920), low permeability and excellent electrical properties.

In the 1950s and 1960s,

tubeless tires. Francis P. Baldwin received the 1979 Charles Goodyear Medal
for the many patents he held for these developments.

In the spring of 2013 two incidents of PIB contamination in the English Channel, believed to be connected, were described as the worst UK marine pollution 'for decades'. The RSPB estimated over 2,600 seabirds were killed by the chemical and hundreds more were rescued and decontaminated.[2]

Uses

Fuel and lubricant additive

Polyisobutylene can be reacted with

crude oil it increases the oil's viscoelasticity
when pulled, causing the oil to resist breakup when it is vacuumed from the surface of the water.

As a

engine knock.[7]

Polyisobutylene is used in some formulations as a thickening agent.

Explosives

Polyisobutylene is often used by the

explosives industry as a binding agent in plastic explosives such as C-4.[8]
Polyisobutylene binder is used because it makes the explosive more insensitive to premature detonation as well as making it easier to handle and mold.

Speakers and audio equipment

Butyl rubber is generally used in speakers, specifically the surrounds. It was used as a replacement for foam surrounds because the foam would deteriorate. The majority of modern speakers use butyl rubber, while most vintage speakers use foam.

Sporting equipment

Butyl rubber is used for the bladders in sporting balls (e.g. Rugby balls, footballs, basketballs, netballs) and to make bicycle inner tubes to provide a tough, airtight inner compartment.

Damp proofing and roof repair

Butyl rubber sealant is used for damp proofing, rubber roof repair and for maintenance of roof membranes (especially around the edges). It is important[citation needed] to have the roof membrane fixed, as a lot of fixtures (e.g., air conditioner vents, plumbing, and other pipes) can considerably loosen it.

Rubber roofing typically refers to a specific type of roofing materials that are made of ethylene propylene diene monomers (EPDM rubber). It is crucial to the integrity of such roofs to avoid using harsh abrasive materials and petroleum-based solvents for their maintenance.

Polyester fabric laminated to butyl rubber binder provides a single-sided waterproof tape that can be used on metal, PVC, and cement joints. It is used for repairing and waterproofing metal roofs.

Gas masks and chemical agent protection

Butyl rubber is one of the most robust elastomers when subjected to

gas masks
and other protective clothing.

Pharmaceutical stoppers

Butyl and bromobutyl rubber are commonly used for manufacturing rubber stoppers used for sealing medicine

bottles.[9]

Chewing gum

Gumdrop chewing gum collecting bin

Most modern chewing gum uses food-grade butyl rubber as the central gum base, which contributes not only the gum's elasticity but also gives it a stubborn, sticky quality which has led some municipalities to propose taxation to cover costs of its removal.[10]

Recycled chewing gum has also been used as a source of recovered polyisobutylene. Amongst other products, this base rubber has been manufactured into coffee cups and 'Gumdrop' gum-collecting bins.[11][12] When filled, the collecting bins and their contents are shredded together and recycled again.

Tires

Because of their superior resistance to gas diffusion, butyl rubber and halogenated rubber are used for the innerliner inside pneumatic tubeless tires, and for the inner tube in older tires.

Insulating windows

Polyisobutylene is used as the primary seal in an insulating glass unit for commercial and residential construction providing the air and moisture seal for the unit.

Notes

  1. ^ "Butyl Rubber: A Techno-commercial Profile". Chemical Weekly. 55 (12): 207–211. November 3, 2009.
  2. ^ "biggest UK pollution incident for decades". London Guardian. 3 May 2013.
  3. ^ "Polyisobutylene Succinimides in Engine Oil". Lubrizol. Archived from the original on 2017-02-15. Retrieved 2017-02-14.
  4. doi:10.4271/2013-01-2682
    .
  5. ^ "Case Studies: Minimizing Worker Exposure to Mist in the Auto Industry". Green Engineering. Environment Protection Agency. 29 April 2015.
  6. PMID 7529704. Archived from the original
    on 2005-11-25.
  7. ^ "04-87 BASF Corp. v. United States" (PDF). Slip Opinions. United States Court of International Trade. 2004-07-15. Archived from the original (PDF) on 2006-09-23.
  8. ^ "Explosives - Compounds". Global Security.
  9. ^ "Halobutyl rubber for pharmaceutical stoppers and seals". ExxonMobil Chemical.
  10. ^ "Making "Greener" Chewing Gum". American Chemical Society. Archived from the original on 2015-12-24. Retrieved 2015-12-23.
  11. ^ "Gumdrop Ltd". Retrieved 2018-03-13.
  12. ^ Shaw, Dougal (2018-03-06). "The chewing gum you don't mind stuck to your shoe". BBC News Online. Retrieved 2018-03-13.

External links

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