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 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 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
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 Temperatura di transizione vetrosaLa transizione vetrosa è una delle più importanti proprietà chimico-fisiche dei materiali amorfi e semi-cristallini, come, ad esempio, vetri, metalli (amorfi), polimeri, ingredienti farmaceutici e alimentari e definisce l’intervallo di temperatura in cui le proprietà meccaniche die materiali variano da duro e fragile a più morbido, malleabile o gommoso.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 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 step visible. Due to the very low glass transition (-120°C), it is recommended to select a start temperature that is approx. 45°C to 50°C below the glass transition temperature, i.e., in this case at -165°C.