Butyl rubber (IIR):
Butyl rubber is a copolymer of isobutylene and isoprene, which was first developed by William Sparks (1976-1905) and Robert Thomas (1908-1984) in New Jersey. (This company is now called Exxon corporation) It was .produced in 1937 in America
.Before 1937, many attempts had been made to produce synthetic rubbers such as: Diene Polymerization
Using a new raw material, Sparks and Thomas copolymerized isobutylene, an olefin (a hydrocarbon containing only one double bond per molecule) with small amounts (1.5 to 4.5%) of isoprene. Isoprene provided the double bond needed to cross-link inert polymer chains such as polyisobutylene. Before adding isoprene to this rubber, butyl rubber was called futile butyl, but with the addition of isoprene, due to its low permeability to gases and excellent resistance to oxygen and ozone, it became unacceptable. It was widely enjoyed. In World War II, this rubber was also called Copolymer GR-I, which was known as isobutylene rubber in the industry
IIR:
IIR is produced by co-polymerization of isobutylene in a solution with low concentrations (1.5 to 4.5%) and isoprene. Butyl rubbers can advance the curing process with sulfur, but due to the presence of unsaturated units (DN), they need more active accelerators such as dithiocarbamate and thiuram
.Sometimes butyl rubbers are mixed with other materials such as oils, fillers, antioxidants, which allows a wide variety of thermo-physical and mechanical properties
Chemical structure:
Properties of butyl rubber:
Butyl rubber has very good resistance to oxygen and ozone and shows good chemical resistance to organic and mineral environments. Like other polymers that do not have double bonds in their main chain, IIR products ca .withstand long-term exposure to heat and usually have good stability in dilute acids and bases
Butyl rubber has very little permeability to gas and moisture. Also, these elastomers are sometimes halogenated with chlorine and bromine to improve its resistance to certain chemical environments, but in this case it loses its .electrical insulation and moisture resistance to some extent. Adding halogens increases the reactivity of rubbers and helps to complete their curing. It also improves the adhesion of this rubber to other unsaturated rubbers
Application of butyl rubber:
Butyl rubber has unique elastomeric properties that make it a good choice for a wide variety of rubber goods. Due to the low gas permeability and low flexibility of this rubber, it is very suitable for the production of inner .tubes of tires and other high pressure tubes. The very low flexibility of this rubber makes it suitable for shock and vibration damping applications
.Lighter grades of this rubber (with lower molecular weight) are used in pressure sensitive adhesives, hot melt adhesives and sealants
Other uses of this tire include the following:
1- Diaphragm
2- Washer
3- wire and cable insulation
4- O-ring
5- Rubber cover
References:
Massey, L. K. (2003). Butyl Rubber. Permeability Properties of Plastics and Elastomers, 459–463. https://doi.org/10.1016/B978-188420797-6.50079-6
Greene, J. P. (2021). Elastomers and Rubbers. Automotive Plastics and Composites, 127–147. https://doi.org/10.1016/B978-0-12-818008-2.00016-7
Britannica, T. Editors of Encyclopaedia (2016, September 13). butyl rubber. Encyclopedia Britannica. https://www.britannica.com/science/butyl-rubber
Astlett Rubber Inc.: Synthetic Rubber. (n.d.). Retrieved January 30, 2023, from https://astlettrubber.com/sr/iir.html