Introduction
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
1. What is rubber from a chemical standpoint?
From a chemical perspective, rubber is an elastomer. This means it is a polymer that has the unique property of elasticity—it can be stretched to a great extent and then return to its original shape when the force is removed. Most natural rubber is a polymer of a monomer called isoprene.
2. What are the key differences between natural and synthetic rubber?
The main differences between natural and synthetic rubber lie in their origin, structure, and properties.
- Origin: Natural rubber is obtained from the latex of the rubber tree (Hevea brasiliensis), while synthetic rubbers are artificially produced from petroleum-based chemicals.
- Monomer: The monomer for natural rubber is isoprene. Synthetic rubbers use various monomers like neoprene for chloroprene rubber or styrene and butadiene for SBR.
- Properties: Natural rubber has high tensile strength and is biodegradable. Synthetic rubbers can be engineered to have specific properties, such as resistance to oil, heat, and abrasion.
3. What is the process of vulcanisation?
Vulcanisation is a chemical process used to enhance the properties of natural rubber, making it more durable and resilient. The process involves heating raw rubber with sulphur to a temperature of about 140-160°C. During this heating, sulphur atoms form cross-links between the long polymer chains of the rubber, making the material stronger and more elastic.
4. Why is raw natural rubber often vulcanised before being used in products?
Raw natural rubber has several drawbacks that limit its direct use. It becomes soft and sticky at high temperatures and brittle at low temperatures. It also has low tensile strength and can be dissolved by many solvents. Vulcanisation is necessary because it creates a stronger, more stable network structure that overcomes these issues, resulting in a material that is tough, elastic, and resistant to temperature changes.
5. How does the molecular structure of rubber allow it to be so elastic?
The elasticity of rubber comes from its long, chain-like polymer molecules, which are tangled together in a coiled, disordered state. When you stretch a piece of rubber, these long chains uncoil and straighten out in the direction of the pull. Once the stretching force is released, the chains naturally return to their original, more stable, tangled configuration. This ability to uncoil and recoil at a molecular level is what we observe as elasticity.
6. Could you give some examples of synthetic rubbers and their specific uses?
Yes, synthetic rubbers are designed for specific needs. Here are a few common examples:
- Neoprene: Known for its excellent resistance to oil, chemicals, and heat. It is used to make hoses, gaskets, and wetsuits.
- Buna-S (SBR): A general-purpose synthetic rubber that is very durable and abrasion-resistant. It is a primary material for making car tyres.
- Buna-N (Nitrile Rubber): Highly resistant to oil, fuel, and other chemicals. It's used for making fuel hoses, seals, and industrial gloves.
7. What are some everyday applications of rubber that demonstrate its key properties?
The uses of rubber are directly linked to its unique properties. For example:
- Vehicle Tyres: Use rubber's durability, elasticity, and abrasion resistance to withstand road conditions.
- Elastic Bands: A simple demonstration of rubber's ability to stretch and return to its original form.
- Waterproof Boots: Utilise rubber's property of being waterproof to keep feet dry.
- Conveyor Belts: Rely on the strength and toughness of rubber to transport heavy materials.
