Rubber

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 fulfil all our needs. Soon we felt the need of 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). Polymerization involved can be written as follows –

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. Reaction involved can be written as follows –

Above reaction can also be represented in easier way as follows –

Comparison Between Natural Rubber and Vulcanized Rubber 

Difference between natural rubber and vulcanized rubber is given below –

Natural Rubber 

Vulcanized Rubber 

It is soft and sticky. 

It is hard and non-sticky. 

It has low tensile strength. 

It has high tensile strength. 

It has lower elasticity. 

It has higher elasticity. 

It can be used over a narrow range of temperature (10-60). 

It can be used over a wide range of temperature (-40 to 100).

It has low wear and tear resistance. 

It has high wear and tear resistance. 

It is soluble in solvents like ether, CCl4, petrol etc. 

It is insoluble in all common solvents. 


Synthetic Rubber 

Synthetic rubber is a manmade 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 addition co-polymer. Its monomer units are butadiene and styrene. Polymerization reaction is given below –

Difference Between Natural Rubber and Synthetic Rubber 

Natural Rubber 

Synthetic Rubber 

It is a natural polymer. 

It is a synthetic or manmade polymer. 

It is obtained from plants. 

It is made from petrochemicals. 

Its monomer unit is 2-methyl 1,3-butadiene or isoprene. 

Monomer units are different in different synthetic rubbers. 

It has higher impurities than synthetic rubber. 

It has a very low amount of impurities. 

Its properties either cannot be changed or very difficult to change.

Synthetic rubbers can be customized according to need. 

It's eco-friendly as obtained from the bark of plants. 

It's not eco-friendly but can be recycled. 

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 cancelation. 

  • 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 in 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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