Hard mica sheet is used as a replacement for asbestos and other insulating boards in a variety of applications. It is a high-performance thermal and electrical insulation board designed for the demanding requirements of electromechanical applications. The board combines high mechanical strength with good heat resistance, and is a UL Recognized component to 94V-0 flame class — file card E216697.
Four figures decide the fit of this board to your application — density, heat resistance and dielectric strength. The full datasheet is below.
The datasheet below covers the complete mechanical, thermal and electrical performance of the board. Use these figures for design verification and incoming inspection.
| Item | Test Condition | B502G Value |
|---|---|---|
| Binder content | — | 10 – 15 % |
| Density | — | 2.45 g/cm³ |
| Heat resistance — continuous | — | 500 / 700 °C |
| Heat resistance — peak | — | 700 / 1000 °C |
| Weight loss — continuous | 500 °C | < 1 % |
| Weight loss — continuous | 700 °C | < 2 % |
| Water absorption | 24 h / 23 °C | < 1 % |
| Fire resistance classification | — | 94V-0 |
| Dielectric strength | 20 °C | 25 kV/mm |
| Dielectric strength | 400 °C / 1 h, tested at 20 °C | 13 kV/mm |
| Dielectric strength | 600 °C / 1 h, tested at 20 °C | 10 kV/mm |
| Volume resistivity | 20 °C | 1016 ohm·cm |
| Volume resistivity | 400 °C | 1012 ohm·cm |
| Volume resistivity | 500 °C | 109 ohm·cm |
Normal dimension: 1200 × 1000 mm, 600 × 1000 mm. Thickness: 0.2 – 80 mm. Other sizes on request.
Note: UL Recognized component 94V-0 flame class rating, file card E216697. Other sizes on requirements.
These are the three features that make hard mica sheet the standard choice for high-performance thermal and electrical insulation — and the reason it replaces asbestos in so many applications.
Instead of Asbestos
A direct, safe replacement for asbestos and other insulating boards. Delivers the same high-performance insulation duty without the health hazards — and is UL recognized to 94V-0 flame class, file card E216697.
High Mechanical Strength
The dense sheet structure (2.45 g/cm³) gives the board the rigidity and strength to be used as a structural insulation element — supporting heating elements, forming arc barriers and holding terminal assemblies in place.
Good Heat Resistance
Continuous 500/700 °C and peak 700/1000 °C with weight loss under 1% at 500 °C and under 2% at 700 °C — so the board keeps its mechanical and electrical performance through extended high-temperature service.
Hard mica sheet is used wherever a rigid, high-strength insulation board is required in combination with heat and electrical current.
Metallurgy
Insulation in metallurgical furnaces, smelting equipment and high-temperature process equipment — where the board must resist both the heat of the process and the electrical requirements of the control system.
Chemical Engineering
Insulation barriers and supports in chemical reactors, process vessels and pipeline systems — where the board is exposed to both elevated temperature and chemical process conditions.
Electric Heaters
Heating element supports, end plates, terminal boards and internal insulation in electric heaters. The high dielectric strength (25 kV/mm at 20 °C) makes the board suitable for both low and high voltage heater designs.
Electromechanical Equipment
Arc barriers, insulation spacers, terminal blocks and mounting plates in electric motors, generators, switchgear and control gear — where both the mechanical strength and the UL 94V-0 rating are required.
Both products start from mica paper bonded with resin, but the binder content and the pressing process are different, which is why they behave very differently in service. Use the table below to make the right choice.
| Property | Hard Mica Sheet (B502) | Soft Mica Sheet (B501) |
|---|---|---|
| Form | Rigid board | Soft, compressible sheet |
| Density | 2.45 g/cm³ | 1.8 – 2.1 g/cm³ |
| Mechanical strength | High — supports loads | Moderate — conforms to surfaces |
| Bolt load | Suits high bolt load joints | Suits low bolt load joints |
| Sealing performance | Limited — not a gasket | Excellent — self-adjusting seal |
| Primary use | Structural insulation board | Gaskets and spiral wound filler |
| Flame class | UL 94V-0 · E216697 | Not UL listed |
Choose hard mica sheet when the board must support a load, hold its shape and provide a rigid insulation barrier — furnace construction, heating element supports, arc barriers and terminal assemblies. Choose soft mica sheet when the priority is sealing a joint at low bolt load and adapting to uneven or changing flange surfaces.
What is a hard mica sheet used for?
Hard mica sheet is used as a rigid insulation board in metallurgy, chemical engineering, electric heaters and electromechanical applications. It is the direct replacement for asbestos and other insulating boards where high-performance thermal and electrical insulation is required alongside high mechanical strength. Typical duties include electrical insulation barriers, heating element supports, terminal boards, arc barriers and general electromechanical insulation.
Is hard mica sheet really an asbestos replacement?
Yes. Hard mica sheet is formulated as a direct replacement for asbestos and other insulating boards. It delivers the same high-performance thermal and electrical insulation duty without the health hazards of asbestos. It is UL recognized to 94V-0 flame class, file card E216697, and is asbestos-free.
What are the key technical parameters of KXT-B502 / B502G?
Binder content: 10–15%. Density: 2.45 g/cm³. Continuous heat resistance: 500/700 °C. Peak heat resistance: 700/1000 °C. Weight loss at 500 °C: <1%; at 700 °C: <2%. Water absorption (24 h at 23 °C): <1%. Fire resistance classification: 94V-0. Dielectric strength at 20 °C: 25 kV/mm; after 1 h at 400 °C: 13 kV/mm; after 1 h at 600 °C: 10 kV/mm. Volume resistivity at 20 °C: 1016 ohm·cm; at 400 °C: 1012 ohm·cm; at 500 °C: 109 ohm·cm.
What is the heat resistance of hard mica sheet?
Continuous heat resistance is 500/700 °C and peak heat resistance is 700/1000 °C. The sheet weight loss is below 1% at 500 °C and below 2% at 700 °C, so the mechanical and electrical performance is retained through extended high-temperature service. The dielectric strength also stays useful: 13 kV/mm after 1 hour at 400 °C and 10 kV/mm after 1 hour at 600 °C, both tested at 20 °C.
What sizes and thicknesses are available?
Normal dimensions are 1200 × 1000 mm and 600 × 1000 mm, with thickness from 0.2 mm to 80 mm. Other sizes are available on request — send us the required length, width and thickness and we will confirm the achievable tolerance before quoting.
What is the UL certification of the hard mica sheet?
The hard mica sheet is a UL Recognized component with 94V-0 flame class rating, file card E216697. This means the material has been independently tested for flame resistance and is approved for use in equipment that must meet UL 94V-0 requirements — including electrical appliances, switchgear, control gear and electromechanical assemblies.
Tell us the model (KXT-B502 or B502G with UL 94V-0), the sheet size (1200 × 1000 mm or 600 × 1000 mm), the thickness (0.2–80 mm), the continuous and peak operating temperature, and the quantity. If you need a custom size or a grade with a specific certification, send us the drawing and the requirement and we will confirm feasibility and lead time.
