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Mullite is an excellent material due to its high temperature stability, strength and creep resistance. It is similar to Cordierite, although it is not as good an insulator and has a higher coefficient of thermal expansion. It is commonly used in heater exchange parts and electrical insulators.

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PropertyASTM MethodUnitsMullite
Color--gray - tan
Gas Permeability--n/a
DensityC 20-97g/cc2.96
Hardness-Mohs Scale8
Water AbsorptionC 20-97%0
Flexural StrengthF417-87psi25,000
Tensile Strength-psi15,000
Compressive Strength-psi150,000
Elastic ModulusC848psi x10626
Shear ModulusC848psi x10610
Poisson's RatioC848none0.24
C.T.E., 25 - 100°CC372-96x10-6/°C3.6
C.T.E., 25 - 300°C--4.1
C.T.E., 25 - 600°C--4.8
Thermal Conductivity, 25°CC408W/m-K4
Max Use Temperature (Non-Loading)-°F3100
Max Use Temperature (Non-Loading)-°C1700
Dielectric Strength
(.125" Thick)
Dielectric Constant
@ 1MHz
Dielectric ConstantD2520-95-6.7
Dielectric Loss @ 1MHZD150-98-0.003
Dielectric LossD2520-95-0.003
Volume Resistivity,
D257ohms-cm>1E + 14
Volume Resistivity,
--4E +10
Volume Resistivity,
--2E +09

Note: The information in this data sheet is for design guidance only. STC does not warrant this data as absolute values. Forming methods and specific geometry could affect properties. Slight adjustments can be made to some of the properties to accommodate specific customer requirements. Most of the dense materials in the table are resistant to mechanical erosion and chemical attack. STC has performed ASTM testing qualification for certain compositions, in accordance with ASTM D2442. Please consult our technical staff for appropriate material and specifc test results.

Note: In addition to the above compositions, STC offers a wide range of alternative materials. Please contact one of our applications engineers for material requirements that may not be shown above.

Download the chart as shown above.