SBR-BR

SBR

 

Common name:

SBR or styrene-butadiene rubber

 

Common chemical composition:

Copolimero di stirene e butadiene

General properties:

It is characterized by good dielectric properties, compatible with silicone oils, water and solutions diluted with acids, bases and salts

It shows poor resistance to oxygen, ozone, UV radiation and oxidizing agents, unless in the form of a specially formulated compound. It is incompatible with mineral, vegetable and animal oils as well as aliphatic, aromatic and chlorinated hydrocarbons.

The operating temperatures are between -45 and +100°C. It shows low resistance to heat and zero resistance to flame, while demonstrating good resistance to the cold, even if the glass transition temperature is -60°C.

SBR is produced by polymerizing the base monomers in an emulsion. Two processes are used for industrial synthesis:

K2S2O7 + 2 RSH → KHSO3 + KHSO4 + 2 RS·

2. Cold rubber method: performed at 5-8°C and the radical initiator is generated by a redox reaction between a hydroperoxide and ferrous ions:

ROOH + Fe2+ → Fe3+ + OH- + RO·

In both cases, the butadiene copolymerizes with styrene especially in 1,4 (cis and trans), but also in 1,2.

Fields of Application:

SBR is primarily used in the tire industry for the production of various parts such as shoulders or tire treads.

In addition to this, there are many other uses including:

  • Flooring Industry;
  • Conveyor belts;
  • Shock absorber – Anti-vibration systems;
  • Sleeves;
  • Mill lining systems;
  • Tank lining systems

SBR ensures finished parts featuring a good balance between wear resistance, wet grip and high workability in the raw form.

BR

 

Common name:

Polybutadiene

 

Common chemical composition:

1,4 cis butadiene

Caratteristiche Generali:

Polybutadiene is a synthetic rubber which has high wear resistance. Its elasticity ensures a post-stress recovery of 80%. Chemically, polybutadiene is a polymer consisting of monomeric units of cis-1,4-butadiene. The polymerization mechanism depends on the reaction conditions, specially on the catalysts used. The formation of bridges due to the presence of double bonds, contributes to the elasticity of the polymer. Polybutadiene undergoes vulcanization to further improve its chemical, physical and mechanical quality, in relation to the intended use.

Depending on the percentages of specific isomeric subunits present, the following categories of polybutadiene can be obtained:

High-cis polybutadiene. Consisting of a large quantity of cis units (> 93%) and just a few vinyl units (<4%), it is synthesized using Ziegler-Natta catalysts and its properties vary depending on the metal used. They can have from low to high mechanical strength. Low-cis polybutadiene. Obtained by using an alkyl-lithium as a catalyst (e.g. N-butyl lithium), it typically contains 40% cis, 50% trans and 10% vinyl units. It is used as an additive for other plastics.

High-vinyl polybutadiene. Synthesized using an alkyllithium catalyst, it contains more than 70% vinyl units. It is used to produce quality tires. A particular type, with 90% vinyl content and a syndiotactic configuration, is sold by a Japanese company and represents a thermoplastic elastomer (at room temperature).

High-trans polybutadiene. Obtained with catalysts similar to those used for the high-cis variety, it is a crystalline plastic (not elastic) that melts at 80°C. It is used in the production of golf balls.

Metallocene polybutadiene.Newly synthesized by Japanese researchers, a metallocene is used as a catalyst, enabling various percentages of cis/trans/vinyl units in the composition.

Fields of Application:

It is used in the production of car tires. Other common uses include the production of rubber objects such as shoe soles or conveyor belts in industrial plants. It is also an additive used in the production of polystyrene and ABS.

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