Mylar sheet is an insulation sheet material made from PET polyester film as the base material. The name Mylar originates from DuPont’s registered trademark for its polyester film and has now become a generic term in the PET insulation film industry. With excellent electrical insulation performance, stable mechanical strength and outstanding chemical corrosion resistance, Mylar sheet plays an indispensable role in motors, electrical appliances, electronic equipment, new energy and aerospace applications.

1. Material Composition and Manufacturing Process

The core base material of Mylar sheet is polyethylene terephthalate (PET), a high-performance engineering plastic synthesized through esterification and polycondensation reactions, then formed into film through melt extrusion and biaxial orientation. The biaxial orientation process aligns PET molecular chains in two planar directions, imparting higher tensile strength, better dimensional stability and superior optical uniformity.

DuPont’s Mylar polyester film series is divided into multiple product lines based on application requirements. The EM series, also known as motor film, is milky white in color with a thickness range of 0.075mm to 0.35mm, primarily used for motor and generator insulation as well as wire and cable insulation layers, featuring excellent mechanical properties and electrical insulation, good heat resistance, certain matting effect, and UL certification. The WC series is a transparent wire and cable base film with a thickness range of 0.019mm to 0.35mm, characterized by high tensile strength, good toughness, not easily broken, high dielectric strength, widely used in communication and power output wire and cable insulation layers. Additional series include MELLINEX-M238 and MYLAR-A, serving applications such as refrigeration compressor insulation and general electrical insulation.

2. Core Performance Characteristics

Excellent Electrical Insulation: Mylar sheet offers extremely high dielectric strength, with conventional PET Mylar sheet achieving dielectric strength above 200 kV/mm and breakdown voltage exceeding 6kV depending on thickness. The material has very low electrical conductivity, effectively preventing current leakage under high voltage stress. The dielectric constant of PET material is approximately 3.2±0.1 at 1MHz, enabling more uniform electric field distribution between insulation and conductors, reducing partial discharge risks.

Excellent Thermal Stability: Mylar polyester film has a long-term service temperature range of -70°C to 130°C, with some high-end grades capable of withstanding 150°C for short periods, and Relative Thermal Index reaching up to 140°C. At extreme low temperatures of -70°C, the material does not become brittle and maintains flexibility; at high temperatures of 130°C, it still maintains stable mechanical strength and electrical properties. Fluorine-free Mylar sheet can even extend the operating temperature range to -40°C to 180°C.

Excellent Mechanical Properties: PET polyester film offers very high tensile strength, reaching above 160 MPa, with impact strength 3 to 5 times that of other films, good folding endurance, and excellent tear strength. The biaxial orientation process further enhances mechanical balance in both longitudinal and transverse directions, preventing breakage, delamination or deformation during processing and use.

Good Chemical Stability and Weather Resistance: Mylar sheet is essentially unaffected by most solvents, oils, acids and alkalis, offering excellent chemical corrosion resistance. At 95% relative humidity, the material maintains stable electrical properties with extremely low moisture absorption. With UV coating treatment, yellowing and aging from outdoor use can be effectively delayed.

Flame Retardancy: Flame retardant Mylar sheet can achieve UL 94 V-0 or VTM-2 ratings, self-extinguishing upon flame removal without promoting flame spread, effectively ensuring safety of electronic and electrical equipment under abnormal conditions. Some high-end environmentally friendly products have achieved fluorine-free formulations, complying with RoHS, REACH and PFAS-Free international environmental standards.

Light Transmission and Optical Properties: Transparent Mylar sheet can achieve light transmittance above 90%, with high surface flatness and good gloss, suitable for applications requiring optical transparency. Matte and milky white Mylar sheets offer light diffusion effects, suitable for optical management in LED panels and display devices.

3. Product Series and Specifications

Mylar sheet is mainly classified by color into transparent, milky white, black, white and natural color types. By functional characteristics, it can be classified into insulation type, flame retardant type, anti-static type, high wear-resistant type and composite type. By form, it is available in roll and sheet forms to meet different application requirements.

Thickness Specifications: Standard thickness covers 0.012mm to 0.35mm. Thinner grades (0.012mm to 0.05mm) are suitable for capacitor dielectric films and ultra-thin insulation spacers in precision applications. Medium thickness (0.075mm to 0.188mm) is suitable for motor slot insulation, phase insulation and transformer layer insulation in conventional applications. Thicker grades (0.25mm to 0.35mm and above) are suitable for insulation barriers and structural supports requiring higher mechanical strength. Some high-end fluorine-free Mylar sheets can extend thickness up to 2.0mm.

Width and Length: Standard roll width can reach 1300mm, with length customizable according to customer requirements. Sheet processing can provide various standard sizes such as 1000mm × 2000mm.

Color Options: Transparent, milky white, black, white, light yellow, dark yellow, blue, red, green, etc., with Pantone color matching available.

Performance Parameter Reference: Dielectric strength above 200 kV/mm, breakdown voltage above 6kV depending on thickness, tensile strength above 160 MPa, elongation at break approximately 100%, long-term temperature resistance -70°C to 130°C, short-term up to 150°C, flame retardancy rating UL94 V-0 or VTM-2, surface resistance adjustable from 10⁶ to 10⁹ ohms depending on anti-static grade.

4. DuPont Mylar Brand and DuPont Teijin Joint Venture

Mylar is the registered trademark of DuPont for its polyester film. Founded in 1802, DuPont is a global leader in science-based products and services, operating in over 70 countries and regions. In the polyester film sector, DuPont established a joint venture with Toray Industries of Japan called DuPont Teijin Films, producing Mylar® brand polyester films known for excellent electrical resistance, widely used in transformers and aerospace applications with ISO 9001 certification. Toray Industries, providing high-performance PET films since 1926, offers products with exceptional thermal stability and dielectric strength, serving the global electrical insulation industry.

5. Quality Certifications and Selection Recommendations

Mylar sheet products comply with multiple international quality standards. For flame retardancy safety: UL 94 V-0 or VTM-2 certification. For environmental compliance: RoHS, REACH and SGS environmental testing, with some products holding SONY Green Partner certification. For electrical performance: IEC 60674 for plastic films for electrical purposes. For production systems: ISO 9001 quality management system certification.

Selection Guidelines:

• For general electrical insulation needs, transparent or milky white PET Mylar sheet is the first choice, offering cost-effectiveness and mature applications

• For motor insulation scenarios, the EM series milky white motor film is recommended, featuring excellent mechanical properties and insulation

• For wire and cable insulation, the WC series transparent film with high tensile strength and good toughness is recommended

• For export products with strict environmental requirements, fluorine-free Mylar sheet meeting PFAS-Free standards is available

• For applications requiring electromagnetic shielding, aluminum foil Mylar composite material is recommended

• For cleanroom scenarios with electrostatic protection requirements, anti-static Mylar sheet is available

• For high-temperature insulation in appliance compressors, the MELLINEX-M238 series with excellent refrigerant chemical resistance is recommended

6. Market Outlook

According to market research forecasts, the global Mylar film market is expected to grow at a compound annual growth rate of 7.1% from 2025 to 2035, reaching a market size of USD 5.5 billion by 2035. With the continued development of emerging industries including new energy vehicles, 5G communications, energy storage systems, smart home products and medical electronics, the application fields of Mylar sheet continue to expand with broad market prospects.