What Is Rubber Definition Types Structure and Uses in Polymer Chemistry
You must have used an eraser while writing or an elastic hair band to tie your hair. Do you know what they are made of? Well, all these are made of rubber. Rubber is one of the most important products of rainforests which we have been using for over 1000 years in various fields. Initially, we used to get rubber from natural sources only, but due to its versatile uses, natural rubber was not able to fulfill all our needs. Soon we felt the need for synthetic rubber production.
What is Rubber?
Rubber is a polymer which can stretch and shrink. It occurs naturally and can be synthesized as well. We have been using rubber products since ancient times. But during the 19th century it became a highly useful industrial raw product for various purposes.
Types of Rubber
Rubber can be divided into following two types based on its origin –
Natural Rubber
Synthetic Rubber
There is a wide variety of synthetic rubber available such as EPDM (Ethylene Propylene Diene Monomer) rubber, commercial black rubber, SBR (Styrene butadiene rubber), NBR (nitrile butadiene rubber), IIR (Isobutylene-isoprene) etc.
What is Natural Rubber?
Natural rubber is a natural polymer of organic compound isoprene obtained from the bark of tropical and subtropical trees. The milky white fluid which is obtained from trees is called latex. This is the reason natural rubber is also known as latex. Natural rubber is also called India rubber, Amazonian rubber and caucho. Leading producers of natural rubber are Thailand and Indonesia.
Monomer Unit of Natural Rubber – 2-methyl 1,3-butadiene (it is also called isoprene)
Structure of Natural Rubber – It is called polyisoprene or cis-1,4-polyisoprene. Its structure is given below –
Preparation of Natural Rubber
Natural rubber or rubber latex is directly collected from plants. Then it is processed for common use by various methods. It is a polymer of 2-methyl 1,3-butadiene (or isoprene).
Vulcanization of Rubber
Reaction of natural rubber with sulfur molecule (S8) in presence of heat to improve its properties is called vulcanization of rubber. In general, natural rubber is very sticky in nature, but vulcanization removes its stickiness and enhances its qualities. Vulcanization of rubber was discovered by Charles Goodyear in 1839.
Comparison Between Natural Rubber and Vulcanized Rubber
Synthetic Rubber
Synthetic rubber is a man made polymer. It is synthesized under controlled conditions by petrochemicals. Many types of synthetic rubber have been synthesized. So, all polymers or synthetic rubbers have different monomer units as well. Although the basic monomer unit for synthetic rubber can be 2-chloro -1,3-butadien or 1,3-butadiene. Neoprene is a synthetic rubber made up of monomer unit chloroprene.
Preparation of Synthetic Rubber
Over 20 types of synthetic rubbers are available today. Out of these we are describing preparation of two synthetic rubbers which are part of your syllabus as well –
Neoprene
Neoprene is a synthetic rubber formed by the free radical addition polymerization of chloroprene. Thus, its monomer unit is 2-chloro-1,3-butadiene. Polymerization reaction is given below –
Buna S (SBR)
Buna S is also a synthetic rubber. In Buna S, Bu stands for butadiene, Na for sodium or natrium (Latin name) and S for styrene. It is also called styrene-butadiene. It is known by its abbreviation SBR (styrene butadiene rubber) as well. It is an additional co-polymer. Its monomer units are butadiene and styrene.
Difference Between Natural Rubber and Synthetic Rubber
Uses of Rubber
Both natural and synthetic rubber are useful in various fields. Even if you look around, you will find many things around you in which rubber has been used. Few uses of rubber are stated below –
Uses of SBR
SBR is used in pneumatic tires.
SBR is used in chewing gum.
SBR is used in gaskets.
SBR is used in shoe heels and soles as well.
SBR is one of the cheapest resins to bind pigmented coatings.
SBR is used in place of PVA in construction as a binding agent.
SBR is used in waterproofing systems.
SBR is used by speaker driver manufacturers as well.
SBR is used as rubber cutting boards
SBR is used in batteries as well.
SBR is used in heat exchangers as well.
Uses of Neoprene
It is relatively inert than natural and other synthetic rubbers which makes it suitable for hoses, gaskets, corrosion resistant coatings.
It can be used as a base for adhesives.
It is used for noise cancellation.
It is used in face masks and gloves.
Neoprene foam is also used in many things.
It is used in construction of buildings as a load bearing base.
It is most commonly used for making clothing for aquatic activities.
It is used in laptop, tablet holders, remote controls, mouse pads etc.
It is used in electric pianos with hammer tips.
It is used in wheelchairs as well.
Uses of Vulcanized Rubber
It is resistant to abrasion which makes it suitable for conveyor belts.
It is used in vehicle tires.
It is used in pumps.
Its elasticity makes it useful for machines as shock absorbers.
It is used in balloons, balls and cushions.
Its resistance to water has made it useful for rainwear and diving gear.
It is inert towards most fluid chemicals which led its use in chemical and medicinal tubing.
It is used in railroad tank cars and lining for storage tanks.
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FAQs on Rubber in Chemistry Structure Classification and Applications
1. What is rubber in chemistry?
Rubber is a natural or synthetic polymer made of long-chain hydrocarbons that exhibit high elasticity and flexibility. In chemistry, natural rubber is primarily composed of cis-1,4-polyisoprene, formed by polymerization of the monomer isoprene (C5H8).
- Natural rubber is obtained from latex of the rubber tree (Hevea brasiliensis).
- Synthetic rubber is produced by polymerization of petroleum-based monomers.
- The elasticity arises from coiled polymer chains that stretch and return to their original shape.
2. What is the chemical formula of natural rubber?
The chemical formula of natural rubber is (C5H8)n, representing a polymer of isoprene units. Each repeating unit is derived from 2-methyl-1,3-butadiene (isoprene).
- Monomer: C5H8
- Polymer structure: cis-1,4-addition of isoprene
- General representation: n C5H8 → (C5H8)n
3. How is natural rubber formed from isoprene?
Natural rubber is formed by addition polymerization of isoprene molecules through cis-1,4-linkage. During polymerization, the double bonds rearrange to connect monomers into a long chain.
- Monomer: CH2=C(CH3)–CH=CH2
- Polymerization reaction: n C5H8 → (C5H8)n
- The resulting structure is cis-1,4-polyisoprene.
4. What is the difference between natural rubber and synthetic rubber?
The main difference between natural and synthetic rubber is that natural rubber is derived from latex, while synthetic rubber is chemically manufactured from petrochemicals. Key differences include:
- Natural rubber: Polymer of isoprene ((C5H8)n), high elasticity, obtained from plants.
- Synthetic rubber: Made from monomers like butadiene or styrene (e.g., styrene-butadiene rubber, SBR).
- Synthetic types often have better resistance to heat, oil, or chemicals.
5. What is vulcanization of rubber?
Vulcanization is the chemical process of heating rubber with sulfur to form cross-links between polymer chains. This process improves strength, elasticity, and temperature resistance.
- Rubber is heated with 3–5% sulfur for soft rubber.
- Sulfur forms –S–S– cross-links between polyisoprene chains.
- Produces stronger, more durable vulcanized rubber.
6. Why is rubber elastic?
Rubber is elastic because its long polymer chains are coiled and can stretch and return to their original shape. The elasticity is due to:
- Flexible polymer backbone chains.
- Weak intermolecular forces between chains.
- Cross-links (after vulcanization) that prevent permanent deformation.
7. What are the types of synthetic rubber?
Common types of synthetic rubber include polymers made from butadiene and its derivatives. Important examples are:
- Styrene-butadiene rubber (SBR) – used in car tires.
- Neoprene – polymer of chloroprene, resistant to oil and heat.
- Buna-N (NBR) – copolymer of butadiene and acrylonitrile.
- Buna-S – copolymer of butadiene and styrene.
8. What is the structure of cis-1,4-polyisoprene?
Cis-1,4-polyisoprene is a polymer in which isoprene units are linked through 1,4-addition with a cis-configuration around the double bond. Its repeating unit can be represented as:
- –[CH2–C(CH3)=CH–CH2]–n
- The double bond remains between carbon 2 and 3.
- The cis arrangement causes chain bending and coiling.
9. What happens when rubber is heated without vulcanization?
When unvulcanized rubber is heated, it becomes soft and sticky because there are no cross-links between polymer chains. Key effects include:
- Increased molecular motion at higher temperature.
- Polymer chains slide past each other easily.
- Permanent deformation under stress.
10. What are the uses of rubber in chemistry and industry?
Rubber is widely used due to its elasticity, chemical resistance, and insulating properties. Major uses include:
- Automobile tires (mainly SBR and natural rubber).
- Laboratory tubing and stoppers due to flexibility.
- Electrical insulation because rubber is a poor conductor.
- Seals and gaskets resistant to chemicals and oils.
