BR: Butadiene rubber

General Properties

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BR

Butadiene rubber


BR stands for “butadiene rubber” and designates, along with SBR (styrene butadiene rubber), the most commonly used synthetic rubber. BR is produced from 1,3-butadiene. The monomers can be connected on both ends (1,4 bonding) or only on one end (1,2 bonding, vinyl group in the side chain) producing diff erent BR types with different properties. The 1,4 bonding can further be classified into 1,4 cis and 1,4 trans, where “cis“ means that the substituents are on the same side of the double bond; “trans” means they are on the opposite side of the double bond.

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-106 to -95 (1.4 cis), -107 to -83 (1,4 trans), -15 (1,2)°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-25 to 12 (1,4 cis), 97 / 145 (1,4 trans), 126 (1,2)°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 Enthalpy46/170 (1,4 cis), 70 to 140 (1,4 trans) J/g
Decomposition Temperature370 to 385 / 460 to 475°C
Young's Modulus-
Coefficient of Linear Thermal Expansion-
Specific Heat Capacity1.76 to 1.96 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 Conductivity0.25 W/(m*K)
Density0.9 to 1.0 g/cm³
MorphologyElastomer with hard and soft segments
General propertiesHigh elasticity. High stability. High abrasion resistance
ProcessingExtrusion, calendering, injection molding, vulcanization
ApplicationsTire industry (blends with NR or SBR). Mechanical engineering. Technical rubber goods (e.g., band conveyors). Golf balls, shoe soles

NETZSCH Measurement

InstrumentDSC 204 F1 Phoenix®
Sample Mass12.29 mg
IsothermalTests at controlled and constant temperature are called isothermal.Isothermal Phase8 min / 3 min / 8 min
Heating/Colling Rates10 K/min
CrucibleAl, pierced lid
AtmosphereN2 (40 ml/min)

Evaluation

Polybutadiene or butadiene rubber has both soft and hard segments. For this reason, the above graphic 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 -101°C (midpoint) in both heatings with a step height (Δcp) of approx. 0.27 J/(g.K) from the soft segments and a melting endotherm with a peak temperature of -5°C from the hard segments. It can be concluded that the sample is mainly a 1,4 cis type.