SBR: Styrene-butadiene rubber

General Properties

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SBR

Styrene-butadiene rubber

Styrene butadiene rubber (SBR), manufactured from 1,3-butadiene and styrene, is the most widely used synthetic rubber. It usually contains 23.5% styrene and 76.5% butadiene. The rubber shows increasing thermoplastic properties with increasing styrene content, yet remains curable. With 1,3-butadiene as a co-monomer, cis-trans-isomerism also occurs.

Structural Formula

Properties

Glass Transition TemperatureThe glass transition is one of the most important properties of amorphous and semi-crystalline materials, e.g., inorganic glasses, amorphous metals, polymers, pharmaceuticals and food ingredients, etc., and describes the temperature region where the mechanical properties of the materials change from hard and brittle to more soft, deformable or rubbery.Glass Transition Temperature	-55 to -35°C
Melting Temperatures and EnthalpiesThe enthalpy of fusion of a substance, also known as latent heat, is a measure of the energy input, typically heat, which is necessary to convert a substance from solid to liquid state. The melting point of a substance is the temperature at which it changes state from solid (crystalline) to liquid (isotropic melt).Melting Temperature	(-20)°C
Melting Temperatures and EnthalpiesThe enthalpy of fusion of a substance, also known as latent heat, is a measure of the energy input, typically heat, which is necessary to convert a substance from solid to liquid state. The melting point of a substance is the temperature at which it changes state from solid (crystalline) to liquid (isotropic melt).Melting Enthalpy	(170 (cis)) J/g
Decomposition reactionA decomposition reaction is a thermally induced reaction of a chemical compound forming solid and/or gaseous products. Decomposition Temperature	435 to 470°C
Young's Modulus	2 to 10 MPa
Coefficient of Linear Thermal Expansion (CLTE/CTE)The coefficient of linear thermal expansion (CLTE) describes the length change of a material as a function of the temperature.Coefficient of Linear Thermal Expansion	180 *10^-6/K
Specific Heat Capacity	1.88 to 2.00 J/(g*K)
Thermal ConductivityThermal conductivity (λ with the unit W/(m•K)) describes the transport of energy – in the form of heat – through a body of mass as the result of a temperature gradient (see fig. 1). According to the second law of thermodynamics, heat always flows in the direction of the lower temperature.Thermal Conductivity	0.20 to 0.25 W/(m*K)
DensityThe mass density is defined as the ratio between mass and volume. Density	0.94 g/cm³
Morphology	Rubber with hard and soft segments
General properties	Good aging and abrasion resistance
Processing	Cross-linking by means of sulfur accelerating systems or peroxides
Applications	Tire industry (cap of tires). Technical rubber goods (conveyor bands, seals). Mechanical engineering. Household articles (e.g., shoe soles)

NETZSCH Measurement

Instrument	DSC 204 `F1` `Phoenix^®`
Sample Mass	13.10 mg
IsothermalTests at controlled and constant temperature are called isothermal.Isothermal Phase	8 min
Heating/Colling Rates	10 K/min
Crucible	Al, pierced lid
Atmosphere	N₂ (40 ml/min)

Evaluation

In the DSC curve from the 1^st heating (blue), SBR shows a Glass Transition TemperatureThe glass transition is one of the most important properties of amorphous and semi-crystalline materials, e.g., inorganic glasses, amorphous metals, polymers, pharmaceuticals and food ingredients, etc., and describes the temperature region where the mechanical properties of the materials change from hard and brittle to more soft, deformable or rubbery.glass transition at -45°C (midpoint), a broad, complex melting transi- tion (with peak temperatures at 19°C and 58°C and a melting enthalpy of approx. 6 J/g), caused by the melting of additives and an ExothermicA sample transition or a reaction is exothermic if heat is generated.exothermal eff ect (peak temperature: 168°C, enthalpy: approx. 10 J/g) that can be attributed to post-vulcanization. This ExothermicA sample transition or a reaction is exothermic if heat is generated.exothermal effect is absent in the 2^nd heating (red) after controlled cooling, indicating that vulcanization was completed in the 1^st heating. As a result, the T_g in the 2^nd heating is shifted to a slightly higher temperature (midpoint of -44°C compared to -45°C in the 1^st heating). The step height (Δc_p) of approx. 0.5 J/(g·K) remained almost unchanged. This small effect of post-cross-linking on temperature and height of the Glass Transition TemperatureThe glass transition is one of the most important properties of amorphous and semi-crystalline materials, e.g., inorganic glasses, amorphous metals, polymers, pharmaceuticals and food ingredients, etc., and describes the temperature region where the mechanical properties of the materials change from hard and brittle to more soft, deformable or rubbery.glass transition step is typical for elastomers. A melting transition due to additives with peak temperatures of 23°C and 34°C and an enthalpy of approx. 4 J/g is also seen in the DSC curve of the 2^nd heating.