What Makes Butyl Rubber Unique in Chemistry?
The element, which is used in making the inner tubes of balls, gloves and other such elements, is butyl rubber. It is formed with the combination of isoprene and isobutylene. Another name for this rubber is IIR which means Isobutylene Isoprene Rubber.
Its commercialization took place in 1943, making it the first rubber that was synthesized. It is used for several applications such as butyl rubber adhesive, the key reason being its gas permeability, low moisture and shock absorption.
The first production of Butyl rubber was carried out by two American chemists, Robert Thomas and William Sparks. This took place at Standard Oil Company in New Jersey in the year 1937.
They copolymerized isobutylene with isoprene present in less than 2%. Earlier, Butyl Rubber was called ‘Futile Butyl’. During the time of world war-2, this was called GR-2. It stood for Government Rubber-Isobutylene.
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Production of Butyl Rubber
The production of both isoprene and isobutylene is carried out through thermal cracking of the natural gas. Or it is even done through lighter fractions of the gas oil. Under normal temperature and pressure conditions, physically, isobutylene is obtained in a gaseous form while isoprene occurs as a volatile liquid.
To convert isobutylene into butyl rubber, it is stored under very low temperatures and is further diluted with methyl chloride. Following this, the addition of isoprene is done in the presence of aluminium chloride. This initiates the reaction leading to copolymerization of these elements. This makes isoprene gain good strength, just like natural rubber.
Further, the presence of unsaturated groups makes it resistant to oxidation. In the case of temperature above glass transition, butyl rubber exhibits an unusually slow molecular motion rate.
Fundamentals of Butyl Rubber
The following points can help you understand the structure and properties of Butyl rubber:
It is a vinyl elastomer. It has a similar structure to polypropylene and polyethylene.
The process of its formation is called cationic vinyl polymerization and is formed from the monomer of isobutylene.
The reaction is usually carried out under low temperatures, the reason being that its process is very fast.
The double bonds are created through the addition of isoprene making it crosslinked through vulcanization, and further exhibiting a nature similar to natural rubber.
With the development of its halogenated, chlorinated and brominated forms, the curing rates were improved in the 1960s.
Charles Goodyear did the invention of the process of vulcanization in 1839. It is a process for thermosetting, which allows vulcanization after product formation.
Advantages of Butyl Rubber
Among all elastomers, Butyl rubber is the only one known which is impervious to gases. The various advantages of butyl rubber are as follows:
Flexibility in the material
Butyl rubber is biocompatible. This makes it resistant to alkaline and acidic chemicals, weathering and it has good ageing properties.
The performance of Butyl rubber is reduced in the presence of petroleum-based fluids, minerals, hydrocarbons, and others.
It offers good insulation.
The usability temperature of the Butyl rubber is between -50 to 250℉. However, at even higher temperatures, its damping characteristics start diminishing.
The Various Mechanical Strengths and Weaknesses of Butyl Rubber are Listed below:
A fair compression set
It has a very bad rebound rating
It offers excellent flex cracking resistance
It has good abrasion resistance
The tear resistance is good
It has excellent resistance towards weather and sunlight
It has poor resistance to flame
The oxidation, water, steam and ozone resistance are excellent
Applications of Butyl Rubber
The various applications that Butyl rubber is used for are as follows:
The Butyl rubber tube can be formed through this easily. The key reason for this is low gas and vapour permeability. Alongside, it is also used to manufacture inner tubes, gloves, ball bladders, etc.
After combining with other elements, the liquid butyl rubber leads to the formation of polyisobutylene, which makes oil and other additives of fuel for machining lubricants.
It also serves the use as a sealant to insulate the windows.
The Butyl rubber strip is used for car and truck body mounts, suspension bushings, and others.
The stoppers utilized in labs and equipment are also made of this material.
The Butyl rubber sheet is also used for making gas masks, considering its low permeability.
It is also available in the form of Butyl rubber adhesive.
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FAQs on Butyl Rubber: Structure, Production & Applications
1. What exactly is butyl rubber?
Butyl rubber is a type of synthetic rubber, chemically known as isobutylene-isoprene rubber (IIR). It's a copolymer, meaning it's made by polymerizing two different monomers: a large amount of isobutylene and a small amount of isoprene. This unique composition gives it excellent airtight and watertight properties.
2. What are the most important properties of butyl rubber?
The key properties of butyl rubber that make it so useful are:
- Low Gas Permeability: It is exceptionally good at trapping air and other gases.
- Chemical Resistance: It shows high resistance to acids, alkalis, and polar solvents.
- Weather and Ozone Resistance: It doesn't degrade easily when exposed to sunlight, ozone, or general weather conditions.
- High Damping: It is excellent at absorbing shock and vibrations.
- Thermal Stability: It can withstand a wide range of temperatures.
3. How is butyl rubber prepared?
Butyl rubber is produced through a process called cationic polymerization. This involves mixing its two main ingredients, isobutylene and isoprene, at very low temperatures (around -100°C). A catalyst, typically aluminum chloride, is used to start the reaction, which links the monomers together to form long polymer chains.
4. What are some common real-world examples of butyl rubber use?
Because it's so airtight, butyl rubber is most famously used for the inner linings of car and bicycle tires to keep them inflated. Other common applications include sealant tapes, stoppers for pharmaceutical vials, protective clothing, speaker surrounds, and even as the base for some chewing gums.
5. What are the main disadvantages of using butyl rubber?
Despite its strengths, butyl rubber has some limitations. Its main disadvantage is its poor resistance to non-polar solvents like gasoline, kerosene, and petroleum-based oils. It also has lower tensile strength and abrasion resistance compared to natural rubber and can be difficult to process during manufacturing.
6. Why is butyl rubber so effective at holding air in tires compared to other rubbers?
The reason lies in its molecular structure. Butyl rubber is made mostly from isobutylene, which creates a very tightly packed and regular polymer chain with minimal empty space. This dense structure makes it extremely difficult for small gas molecules to wiggle through, giving it exceptionally low gas permeability. Natural rubber, in contrast, has a less compact structure that allows air to escape more easily.
7. How does the chemical structure of butyl rubber differ from that of natural rubber?
The primary difference is in their polymer backbones. Butyl rubber has a mostly saturated backbone from the isobutylene units, with very few double bonds (from the isoprene). This makes it very stable and resistant to attack by ozone and heat. Natural rubber (polyisoprene) has a backbone full of double bonds, which makes it more flexible and strong but also much more reactive and susceptible to degradation from heat, UV light, and ozone.
8. What does the chemical name 'isobutylene-isoprene rubber' tell us about the material?
The name itself explains its composition perfectly. It tells us that butyl rubber is a copolymer, not a single-monomer polymer. The name specifies the two monomers involved: isobutylene, which forms the bulk of the polymer, and isoprene, which is added in small amounts. The isoprene introduces the double bonds necessary for vulcanization (hardening with sulfur), a crucial step to make the rubber useful.
