Emulsion polymerised styrene- butadiene rubber (E- SBR) is one of the most widely used polymers in the world today. Emulsion polymerised styrene- butadiene rubber is employed in many demanding applications, which enhance the quality of life and contribute significantly to our economy and standards of living.
Since styrene- butadiene rubber lacks the self- reinforcing qualities of natural rubber due to stress induced crystallisation, gum vulcanizates of styrene- butadiene rubber have lower tensile properties. The tensile property of Emulsion polymerised styrene- butadiene rubber vulcanizates depends in great measure on the type and amount of filler in the compound. Cured gum stocks have only 2.8 to 4.2 MPa tensile strength, while fine particle carbon black loadings can produce tensile strength of 27.6 MPa. Though the compression set of some of the common emulsion polymerised styrene- butadiene rubber compounds is high, by proper compounding and blending, it is possible to obtain emulsion styrene- butadiene rubber vulcanizates with a low compression set.
Styrene- butadiene rubber is a non- polar polymer and its vulcanizates are poor conductors of electricity.
The electrical properties of emulsion polymerised styrene- butadiene rubber depend to a large extent on the amount and type of emulsifier and coagulating agent(s) used.
Resistance to Fluids
While emulsion polymerised styrene- butadiene rubber vulcanizates are resistant to many polar solvents such as dilute acids and bases, they will swell considerably when in contact with gasoline, oils, or fats. Due to this limitation, styrene- butadiene rubber cannot be used in applications that require resistance to swelling in contact with hydrocarbon solvents.
Styrene- butadiene rubber can be cured with a variety of cure systems including sulfur (accelerators and sulfur), peroxides and phenolic resins. Processing of styrene- butadiene rubber compounds can be performed in a mill, internal mixers or mixing extruders. Styrene- butadiene rubber compounds are cured in a variety of ways by compression, injection moulding, hot air or steam autoclaves, hot air ovens, microwave ovens and combinations of these techniques.