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Preparation of Polydienes

Two of the commercially important polymers of dienes are: neoprene and Buna-S.

1. Neoprene: this is synthetic rubber which resembles natural rubber in its properties. It is obtained by polymerisation of chloroprene (2-chloro- 1, 3-butadiene) in the presence of potassium persulphate.

Characteristics and uses: Neoprene is superior to natural rubber in its stability to aerial oxidation and also in its resistance to oils and other solvents. It is generally used for making: hoses, shoeheels, stoppers and belts.

2. Buna-S: It is a copolymer of 1, 3-butadiene and styrene. It is obtained by the polymerisation of butadiene and styrene in the ratio of 3:1 in the presence of sodium. It is also known as styrene butadiene rubber (SBR).

In Buna-S, Bu stands for butadiene, na stands for sodium which is polymerizing agent and S stands for stryrene.

Characteristics and uses: SBR has slightly less tensile strength than natural rubber. It is used in the manufacture of:

Automobiles tyres, rubber soles, belts, hoses, etc.