synthtic rubber

• A synthetic rubber is any artificial elastomer, mainly polymers synthesized from petroleum byproducts, two thirds of which are synthetic.
• Natural rubber exhibits many excellent properties in terms of mechanical performance, but is often inferior to certain synthetic rubbers, especially with respect to its thermal stability and its compatibility with petroleum products.
• Styrene-Butadiene Rubber (SBR) is the most widely used elastomer worldwide, with the single largest application in passenger car tires, particularly in tread compounds for superior traction and treadwear.
• Considering the appropriate combination of elastic and plastic properties, the most advantageous are rubbers with styrene content from 23 to 25%.
• SBR with high content of styrene (40-55%) are known as self-reinforcing rubbers or fillers (70 – 90% of styrene).
• SBR with low styrene content (3-13%, E-SBR) are suitable for low-temperature applications.
• Polybutadiene Rubber (BR) has better low temperature flexibility and higher resilience at ambient temperatures.
• L-SBR with styrene content around 15% are used in combination with BR rubbers for production of radial tires.
• Butyl Rubber (IIR) is highly resistant to the diffusion or solution of gas molecules.
• Neoprene (CR) has high tensile strength.
• Nitrile Rubber (NBR) has exceptional resistance to attack by most oils and solvents.
• Polyisoprene (IR) is easier to process and gives a less variable product.
• Silicone Rubber is more expensive than other types of elastomer.
• Polybutadiene rubber (BR) is a synthetic rubber derived from the polymerization of butadiene, a petrochemical monomer, and belongs to the class of elastomers known as polybutadienes.
• The monomer of Polybutadiene rubber (BR) is produced by the polymerization of 1,3-butadiene, a hydrocarbon with two double bonds in its structure.
• Polybutadiene rubber (BR) consists primarily of long chains of butadiene molecules joined together through double bonds.
• The properties of Polybutadiene rubber (BR) depend on the polymerization method and type of initiator, and it determines basic properties of BR.
• Trans-1,4-polybutadienes do not have elastic property.
• 1,2-polybutadienes do not have elastic properties.
• cis-1,4-polybutadienes have best elastic properties.
• Pure cis-1.4-polybutadiene has T g below –100 °C and pure 1,2-polybutadiene around –15 °C.
• The T g of commercially produced polybutadienes depends on the mutual arrangement of these units in their macromolecules and it normally varies in between –100 and –80 °C.
• Polybutadiene rubbers have low tensile strengths.
• Polybutadiene rubbers have high resistance against abrasion, which increases with increased content of 1.2 structural units in their macromolecules.
• The mutual arrangement of styrene and butadiene units in SBR can have random, partially-block or block character.
• Polybutadiene rubbers react slower with oxygen and ozone than Natural Rubber (NR), but presence of antidegradants in their compounds is necessary.
• A water-soluble initiator or redox system is introduced to initiate the polymerization reaction in emulsification.
• Styrene-butadiene rubbers (SBR) are copolymers of styrene and butadiene.
• In the solution polymerization of butadiene, butadiene monomers are dissolved in a non-polar solvent such as benzene, hexane or cyclohexane along with a catalyst.
• Various catalysts like organolithium compounds or transition metal catalysts (Ziegler-Natta catalysts based on Ti, Co, Ni or Ne salts and alkyl aluminium compounds) are used in the catalysis of the reaction.
• The styrene and butadiene monomers randomly join together along the polymer chain to form the copolymer structure of SBR.
• Emulsion polymerization is the predominant method for producing SBR due to its efficiency in producing versatile grades of SBR with different properties suitable for a wide range of industrial applications.
• SBRs are the most commonly used rubbers and their properties are influenced not only by micro- and macrostructure of polymer chains but also by styrene content.
• Increasing content of styrene and 1,2 structural units in SBR contributes to increase of T g of SBR.
• The content of the cis-1.4 structural units is high and it normally varies between 90 and 98 % in the polybutadiene produced by solution polymerization.
• Variability of arrangement of structural units and content of styrene and butadiene in copolymer molecules allow production of SBR rubbers with various properties.
• The largest portion of the globally produced BR is obtained by the solution polymerization of butadiene.
• The resulting polybutadiene solution is then purified to remove any unreacted monomers and catalyst residues.
• The catalyst initiates the reaction, causing the butadiene monomers to join together, forming long chains of polybutadiene in the solution.
• Polybutadiene produced in these polymerization systems have molecular weights of approximately 250 000 – 300 000 g mol -1, are branched by long chains and have rather broad distribution of molecular weights.