FEP(F46) Polyimide Composite Film

FEP (F46) Coated Polyimide Film – FH and FHF Types

FEP Coated Polyimide Film, commonly referred to as FEP Coated Kapton Film, combines the high-temperature resistance of polyimide film with the heat-sealing capability of fluorinated ethylene propylene (FEP). 

The polyimide base film provides high dielectric strength, mechanical strength and thermal stability, while the FEP coating adds heat-sealing capability, moisture resistance, chemical resistance and a smooth, low-friction surface.

Chengrui Insulation Material Co., Ltd. supplies two standard types:

• FH type: FEP coating on one side of the polyimide film

• FHF type: FEP coating on both sides of the polyimide film

These FEP coated polyimide films are mainly used for magnet wire, high-temperature lead wire, electrical cable wrapping and insulation structures that require thermal bonding.

What Is FEP (F46) Coated Polyimide Film?

FEP coated polyimide film is a composite insulation material consisting of:

Polyimide Film (PI Film)

FEP Fluoropolymer Coating

Unlike an ordinary polyimide film, FEP-coated polyimide film can bond to itself or to compatible materials after controlled heating and pressure. The FEP layer acts as athermoplastic heat-sealing layer rather than a pressure-sensitive adhesive.

The finished product combines:

The electrical and mechanical properties of polyimide film

The heat-sealing properties of FEP

Improved moisture and chemical resistance

Good flexibility for winding and wrapping

Stable insulation performance in demanding electrical applications

FH and FHF Film Structures

FH film has an FEP coating on only one side. It is suitable when only one surface needs to be thermally bonded.

Typical uses include:

• Single-side thermal lamination

• Electrical insulation wrapping

• Bonding polyimide film to metal foil

• Heater and sensor insulation

• High-temperature wire insulation

FHF Type: Double-Side FEP Coated Polyimide Film

FHF film has an FEP coating on both sides. Both surfaces can be heat-sealed, making it more suitable for overlapping wraps and fully bonded insulation structures.

Typical uses include:

• Magnet wire wrapping

• High-temperature cable wrapping

• Overlap sealing

• Coil insulation

• Flexible heating elements

• Electrical components requiring double-side thermal bonding
  
  

  FH vs. FHF Polyimide Film
  Item	FH Type	FHF Type
  Construction	FEP/PI	FEP/PI/FEP
  FEP coating	One side	Both sides
  Heat-sealable surface	Single side	Double side
  Tensile strength	≥90 MPa	≥80 MPa
  Standard thicknesses	38, 50, 63 and 75 μm	30, 50, 75 and 125 μm
  Main advantage	Lower thickness and material cost	Double-side bonding and better sealing
  Typical application	Single-side lamination	Magnet wire and cable wrapping

Type: FEP coatd polyimide film

Thickness: 38um, 50um, 75um, 125um etc

Standard width: 6–1000 mm

Width for 125 μm FHF film: 6–520 mm

Roll length ≥300 m

Standard core diameter: 76 mm / 3 inches

Custom widths may be supplied according to the customer’s winding equipment and insulation design.

FEP Coated Polyimide Film vs Standard Polyimide Film

The most important advantage over standard polyimide film is FEP coated polyimide film is Heat Sealable. Standard polyimide film performs extremely well as an electrical insulation material. However, when insulation layers need to be joined together, additional adhesive systems are often required.

FEP coated polyimide film solves this problem.

When heated above the melting temperature of FEP, the coating forms a strong bond with adjacent surfaces, creating a sealed insulation structure without separate adhesives.

This simplifies production and improves long-term reliability.

How to Select the Correct Type

Choose FH film when:

Only one surface needs to be heat-sealed

The opposite side should remain as a polyimide surface

Lower total thickness is preferred

Material cost needs to be controlled

The film will be laminated to another substrate on one side

Choose FHF film when:

Both surfaces need to be heat-sealed

The film will be overlap-wrapped

Multiple film layers must bond together

Better sealing and moisture protection are required

The product is used for magnet wire or cable insulation

Applications:

Flexible Heaters: Flexible heater manufacturers are among the largest users of FEP coated polyimide film.

Aerospace and Aviation Insulation: Weight reduction and reliability are critical in aerospace systems.

Battery Systems: Modern battery systems require insulation materials capable of handling heat, vibration and long service life.

High-Temperature Wire Harnesses: Many aerospace, railway and industrial wire harnesses require insulation materials that can be wrapped and sealed around conductors.

Frequently Asked Questions

Q1:What is the difference between FEP polyimide film and FH/FHF film?

A: FEP coated polyimide film is the general product category. FH and FHF describe the coating structure:

FH: FEP coated on one side

FHF: FEP coated on both sides

Q2: Does FHF film have adhesive on both sides?

A: It has FEP layers on both sides, but it is not a conventional double-sided adhesive film. The FEP layers become bondable after heating.

Q3: Why not use ordinary Kapton film?

A: Standard Kapton film cannot be heat sealed. FEP coated polyimide film provides the same high-temperature performance while allowing thermal bonding.

Q4: What temperature can FEP coated polyimide film withstand?

A: The material typically operates continuously at temperatures up to 260°C.