• Buna-3 is also known as styrene-butadiene
• Buna-S name is derived from Bu-butadiene and Na-sodium/ natrium and S-styrene
• It is a replacement for natural rubber.
• It is derived from two monomers, styrene and butadiene. The mixture of these two monomers is polymerized by two basically different processes: from solution (S-SBR) or as an emulsion (E-SBR).
• It has good abrasion resistance and good aging stability when protected by additives.
• The styrene/butadiene ratio influences the properties of the polymer: with high styrene content, the rubbers are harder and less rubbery.

• It is the most commonly used synthetic rubber.

   

Preparation:

• It is a random co-polymer formed by the emulsion polymerization of a mixture of 1:3 butadiene and styrene in the presence of peroxide catalyst at 5 degree Celsius and therefore the product is called as cold rubber. The rubber obtained is also called Styrene butadiene rubber (SBR).

• It is vulcanized with sulfur. The rubber is slightly inferior to natural rubber in its physical properties.

   

Uses:

• 1) It is used for the manufacture of passenger car tyres and treads, motor cycle and scooter tyres, cycle tyres and tubes.
• 2) They are also used for the manufacture of conveyor belts, foot-wares, shoe soles, hoses and electrical insulation.