Q: Silicone rubber

General Properties

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Q

Silicone rubber


Hydrogenated acrylonitrile butadiene rubber (HNBR) is a saturated (or only slightly unsaturated) copolymer of acrylonitrile and butadiene and is obtained by selective hydrogenation of the butadiene groups of NBR (see page 162). Due to fewer double bonds, it is considerably more inert than NBR.

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-135 to -120°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-50 to -40°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 Enthalpy35 J/g
Decomposition Temperature530 to 600°C
Young's Modulus1 to 10 MPa
Coefficient of Linear Thermal Expansion190 to 255 *10-6/K
Specific Heat Capacity1.3 to 1.5 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 Conductivity0.22 W/(m*K)
Density1.25 g/cm³
MorphologySemi-crystalline rubber
General propertiesGood aging, ozone and weather resistance. Good electrical insulating properties. Good cold flexibility
ProcessingCross-linking mostly by means of peroxides
ApplicationsElectrical industry (e.g., electric cable insulation). Aircraft industry (e.g., seals for window and cabin doors in planes). Accessories for instrument and apparatus engineering (e.g., O-rings)

NETZSCH Measurement

InstrumentDSC 204 F1 Phoenix®
Sample Mass12.81 mg
IsothermalTests at controlled and constant temperature are called isothermal.Isothermal Phase8 min
Heating/Colling Rates10 K/min
CrucibleAl, pierced lid
AtmosphereN2 (40 ml/min)

Evaluation

The amorphous portion of silicone rubber (Q) exhibits a very low 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 of -120°C (midpoint, 2nd heating, red). The crystalline portion exhibits a sharp melting transition with a peak temperature of -45°C (both heatings). The detected 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 with step heights (Δcp) of 0.08 J/(g*K), even in the 2nd heating after a controlled cooling at 10 K/min, indicates a relatively high amorphous content. Highly crystalline silicone rubbers often must be quenched (cooled very quickly) in order to make 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 visible. Due to the very low 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 (-120°C), it is recommended to select a start temperature that is approx. 45°C to 50°C below 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 temperature, i.e., in this case at -165°C.