Muscovite and Phlogopite Mica – Thermal and dielectric insulation materials

Supplier & Converter · Standard Sheets and Custom Machined Parts

Industrial micas, specifically muscovite mica (white mica) and phlogopite mica (amber mica), are high-performance rigid insulation materials. Thanks to their exceptional thermal resistance (up to 1,000°C for phlogopite) and high dielectric strength, these natural materials provide effective protection against heat and electricity in the most demanding industrial environments.

Available in sheets, tubes, or custom machined parts, ELIT mica solutions meet the requirements of the glass, metallurgical, electrotechnical, thermal, and nuclear sectors... They also provide a safe, durable alternative to legacy asbestos-based insulation.

Our Mica product lines – Muscovite & Phlogopite

Why choose mica for thermal and electrical insulation

Balance between thermal insulation, electrical insulation, and mechanical strength

Mica sheets and machined parts, manufactured from muscovite or phlogopite mica bonded with high-temperature silicone resin, are engineered specifically for industrial environments subjected to extreme temperatures. They deliver outstanding thermal and electrical insulation, high dimensional stability, and robust mechanical strength, making them ideal for critical applications.

Key Applications:

Owing to their unique combination of thermal resistance, electrical insulation, and stability, muscovite and phlogopite micas are utilized across numerous industrial sectors. Below are several application examples where these mica insulators particularly excel:

High-temperature industrial furnaces: insulation and lining for melting furnaces, induction furnaces, electric arc furnaces, and incinerators. Mica sheets act as thermal barriers within furnace walls, protecting the steel structure while withstanding extreme heat. Phlogopite, in particular, is used for internal linings of furnaces requiring temperature resistance > 800°C.
Electric heating elements: supports and sheaths for heating resistors, induction coils, and other heating components. Since muscovite mica is an excellent electrical insulator, it serves as an insulating carrier for heating resistors, heating coils, and radiant tubes, preventing short circuits while resisting generated heat.
Molds, presses, and thermal machinery: fabrication of thermal insulation platens for injection molding or forging presses, thermal shims in foundry or glassmaking molds, and hot runner insulation. Interposed between a heat source and a surface requiring protection, mica sheets reduce heat loss and shield sensitive machine components (cylinders, frames, etc.) from high temperatures.
Gaskets and thermal barriers: production of sealing and insulating gaskets for furnace flanges, burners, exhaust manifolds, and heat exchangers. Non-combustible and chemically inert, mica is a proven replacement for former asbestos packings, ensuring reliable sealing in very high-temperature zones (several hundred degrees) without outgassing smoke or deteriorating.

These examples are non-exhaustive. More generally, wherever a material is required to provide thermal insulation in an extreme-heat zone while delivering electrical insulation or a non-flammable barrier, muscovite or phlogopite mica stands out as a premier solution. ELIT technical experts can assist you in determining the most suitable mica grade and configuration for your specific application (industrial furnace, heating appliance, electrical equipment, etc.).

Available Mica product ranges:

Muscovite mica

The Muscovite mica is a potassium aluminum silicate belonging to the mica family. It is valued for its light color and purity, as well as its superior insulating properties. Muscovite delivers one of the highest dielectric strengths among insulating materials, making it an exceptional electrical insulator. It also resists heat up to approximately 500–600°C continuously (peaks up to ~700°C) without degrading, while maintaining outstanding mechanical properties at room temperature.

- - Density: ~2.2 g/cm³ (compact rigid mica sheet)
  - Operating temperature: ~550°C continuous, up to 700°C peak
  - Dielectric strength: ~20–25 kV/mm (exceptional electrical insulator, even at thin gauges)
  - Mechanical strength at 20°C: very high (compressive strength > 400 MPa, flexural strength ~180 MPa)
  - Color and appearance: transparent to silvery white (natural muscovite in thin sheets)

Thanks to this combination of properties, muscovite mica is often preferred for applications demanding optimal electrical insulation coupled with solid temperature resistance. For instance, it is ideal as an insulator in electronic or electrical components exposed to heat, ensuring reliable dielectric protection. Conversely, for continuous temperatures exceeding 600–700°C, phlogopite is generally preferred, as detailed below.

Phlogopite mica

The Phlogopite mica is a magnesium silicate, ranging in color from golden brown to amber. It is renowned for its exceptional resistance to extreme temperatures. Phlogopite withstands severe thermal conditions of approximately 700–800°C continuously, and up to 1,000°C peak without delaminating. It also exhibits superior resistance to repeated thermal shock compared to muscovite. Its dielectric strength remains excellent (in the same order of magnitude as muscovite), guaranteeing reliable electrical insulation even at high temperatures.

- - - Density: ~2.2 g/cm³ (similar to muscovite mica)
    - Operating temperature: ~750°C continuous, up to 1,000°C peak without degradation
    - Dielectric strength: ~20–25 kV/mm (very good electrical insulator, including in high-heat environments)
    - Mechanical strength at 20°C: high (compressive strength ~300 MPa, flexural strength ~120 MPa), slightly lower than cold muscovite, but retains its properties well at high temperatures
    - Color and appearance: amber-brown to dark gray, sometimes referred to as “black mica” due to its tint

In summary, phlogopite mica is the material of choice for the most extreme temperature environments. It is utilized in applications where muscovite would reach its thermal limits: ultra-high temperature industrial furnace insulation, components subjected to severe thermomechanical stresses, etc. While slightly less effective in pure electrical insulation than muscovite, phlogopite offers superior thermal resistance and reliable dimensional stability even when temperatures rise above 700°C. Muscovite and phlogopite are frequently combined with high-performance binders (silicone resin, etc.) to form rigid sheets maximizing the specific advantages of each mica grade.

Technical Comparison: Muscovite Mica vs. Phlogopite Mica

Technical specifications	Muscovite Mica	Phlogopite mica
Composition	KAl₂(AlSi₃O₁₀)(OH)₂	KMg₃(AlSi₃O₁₀)(OH)₂
Color	Transparent to silvery white	Amber brown to dark grey
Density	~2.2 g/cm³	~2.2 g/cm³
Maximum continuous temperature	~550 °C	~750 °C
Maximum peak temperature	~700 °C	~1000 °C
Dielectric strength	25 kV/mm	25 kV/mm
Compressive strength	> 400 MPa at 20 °C	~300 MPa at 20 °C
Flexural strength	~180 MPa at 20 °C	~120 MPa at 20 °C
Thermal shock resistance	Moderate	Excellent
Chemical resistance	Excellent (acids/bases)	Very good (slightly lower than muscovite)
Machinability	Good, more brittle material	Very good, more flexible material
Typical applications	Electrical equipment, heating elements, high-voltage components	Furnaces, moulds, parts subjected to severe thermal stress