6021 Motor Insulation Film (Milky White PET Film)

Time: 06-30 2026 Auther: Xujue Electrical

6021 Motor Film (Biaxially-Oriented Milky White PET Film) is an indispensable core insulation material in electric motor manufacturing and repair.

Technical Guide: 6021 Motor Insulation Film (Milky White PET Film)

6021 Motor Film (Biaxially-Oriented Milky White PET Film) is an indispensable core insulation material in electric motor manufacturing and repair. Operating like a heavy-duty “high-voltage shield,” it completely isolates the energized magnet wires (enameled copper wires) from the metal stator core during motor operation.

1. Why is 6021 Essential for Motor Manufacturing?

In harsh environments characterized by high-speed rotation, intense vibration, and heat, ordinary plastic films quickly melt or rupture. 6021 motor film offers three critical physical property advantages:

High Dielectric Strength (Voltage Resistance): At standard thicknesses, it boasts a breakdown voltage of over 10kV to 15kV, effortlessly deflecting transient high-voltage spikes during motor startup and operation.

Extreme Mechanical Toughness (Tear & Tensile Resistance): Whether pulled forcefully by automated winding machines or heavily pressed with wedges during manual slot inserting, the film deforms but never cracks or splits.

Excellent Insulation Varnish Resistance: After winding, the stator undergoes varnish impregnation and high-temperature baking. 6021 film is chemically immune to harsh organic solvents like benzenes and ketones used in the varnish, ensuring it will not dissolve or swell.

2. Four Key Applications in Electric Motors

Application Position	Process Details	Primary Function
Slot Insulation	Die-cut and folded into “U-shapes”, “O-shapes”, or cuffed structures, then pre-inserted into the stator core slots.	The primary application. It completely isolates the magnet wires from the sharp metal walls of the stator slot to prevent grounding shorts.
Slot Wedges / Top Insulation	Inserted as a sealing slider over the top layer of the slot once all magnet wires are embedded.	Prevents the copper coils from shifting or flying out of the slot due to centrifugal forces at high rotational speeds.
Phase Insulation	Cut into fan, arc, or strip shapes and placed between different phase windings (e.g., U, V, W phases) at the coil ends.	Prevents phase-to-phase short circuits caused by long-term friction, vibration, or insulation wear between different coils.
End-Winding Banding & Lining	Slit into narrow tapes (e.g., 10mm or 20mm wide) to wrap and bind the coil extensions.	Increases the overall mechanical rigidity of the motor windings and adds extra moisture protection.

3. Core Technical Specifications & Common Sizes

Material & Appearance: 100% Polyethylene Terephthalate (PET), manufactured via a biaxial orientation process. It features a milky white, semi-transparent look with a smooth, mirror-like high-gloss finish on both sides.

Thermal Insulation Class: Class E (120°C) to Class B (130°C).

Common Thickness Selection (Industry standard units: mm or Microns/μm):

0.125mm (125μm) / 0.188mm (188μm): Used for household ceiling fans, handheld power tool motors, micro gear motors, etc.

0.25mm (250μm) / 0.30mm / 0.35mm: Used for standard industrial electric motors, three-phase asynchronous motors, water pump motors, etc.

4. Limitations of Pure PET Film & Industrial Upgrade Solutions

In practical production, pure 6021 glossy film has one limitation: its surface is too slick, resulting in poor varnish adhesion (poor wettability). This can affect the motor’s heat dissipation and overall structural rigidity after curing. To resolve this, the industry developed two advanced alternatives:

6021G Matte Film (Roughened Film): The film surface is physically or chemically texturized into a matte, hazy finish, multiplying its varnish absorption and adhesion capabilities.

DMD Insulation Composite Paper: A three-layer composite material consisting of 6021 PET film sandwiched between two layers of polyester non-woven fabric. This completely solves the varnish adhesion issue and upgrades the thermal rating to Class F (155°C), making it the most widely used slot insulator for modern medium-to-large motors.

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