Rubber

Rubber is one of the most important raw materials used today. It is a naturally available elastic polymer. Ordinary rubber is a thermoplastic substance. Rubber is especially useful for several reasons. It does not easily conduct electricity and retains air and moisture. However, the fact that it is elastic is what matters most to us. A rubber band's elasticity allows it to rapidly return to its original shape after being stretched. A rubber ball bounces because of this same springiness. The rubber heels absorb shock while walking because they have elasticity. We depend so much on rubber that it would be almost impossible to get along without it. This is not the case with most other materials. Rubber dissolves in Benzene.

Types of Rubber

Rubber is broadly classified into three as natural rubber, synthetic rubber and vulcanized rubber. 

1. Natural rubber

Natural rubber comes from the juice of a tree. It is derived from the latex of rubber trees. Polyisoprene, an elastomer is an example for Natural Rubber. Natural Rubber is known for its elasticity, flexibility, and high tensile strength. 

2. Synthetic rubber

Synthetic rubber is made from chemical polymerization and other manufacturing processes. It is a man made polymer produced from petrochemicals. The first synthetic rubber is Neoprene. Buna Rubber, Styrene Butadiene Rubber (SBR), Butyl Rubber and Thiokol are examples of synthetic rubber.

i. Neoprene Rubber 

The main properties of Neoprene Rubber are not easily flammable, does not easily reacts with oils and solvents and stable at high temperature. Its main uses is in the manufacture of cable insulation, conveyor belt in coal mines, making hose etc.

ii. Buna Rubber 

Buna Rubber is a synthetic rubber with a variety of uses. The two types of Buna Rubber are Buna-S (Styrene-Butadiene Rubber) and Buna-N (Nitrile Rubber). Tires and soles are made from Buna-S, whereas oil seals and gloves are made from Buna-N.

iii. Styrene Butadiene Rubber (SBR)

High frictional force, not easily broken, resists ozone and gets easily oxidised are the properties of Styrene Butadiene Rubber (SBR). Tyres and Foot wears are made from Styrene Butadiene Rubber.

iv. Butyl Rubber

Butyl Rubber has high air impermeability and is used in tire inner tubes and other sealing applications.

v. Thiokol

High elasticity, hardness, doesn't dissolve in organic solvents are the properties of Thiokol. It is used in the manufacture of tanks for storing solvents, making seal and making hoses.

3. Vulcanized Rubber

In 1770, the English chemist Joseph Priestly discovered the substance would rub out pencil marks and named it rubber. It was a sticky material until in 1839 when the American inventor Charles Goodyear accidentally dropped a mixture of sulphur and rubber on a hot stove and found that it was soft and pliable even when cold. The process of heating rubber with sulphur for the betterment of its properties is called vulcanisation. Vulcanisation enhances the following properties of rubber: tensile strength, hardness, elasticity, ability to withstand heat changes. These properties can be varied by changing the quantity of sulphur, temperature and time taken for vulcanisation. Goodyear's discovery began the rubber industry, including the manufacture of rubber tyres. Thomas Hancock got the patent for the invention of vulcanisation.

Rubber Tyre - Although the discovery of vulcanized rubber took place in 1839, it was not until 1887 that the Scottish born inventor John B.Dunlop made his first pneumatic tyre for a biycle. Tyres filled with air are called pneumatic. By 1890 the pneumatic tyre business was in full swing in Ireland. In time the tyres were made for automobiles also. Tubeless tyres and modern materials have greatly improved tyre performance in recent years.