Flexible heating films are widely used for battery heating, electronic devices, medical equipment, automotive components, packaging, and other applications where a thin and lightweight heat source is required. PET heating films and PI (Polyimide) heating films are two common solutions.
Although both types can be designed as flexible electric heaters, their substrate materials have different characteristics. Choosing between PET and PI depends on the required operating temperature, environmental conditions, flexibility, cost, and application requirements.
What Is a PET Heating Film?
PET heating film uses polyethylene terephthalate (PET) as the flexible substrate. A conductive heating layer, such as carbon, graphene, or other conductive ink, can be screen-printed onto the PET film to create the heating circuit.
A typical structure is:
Protective Layer → Printed Heating Layer → PET Film → Adhesive Layer
PET heating films are particularly suitable for low-temperature heating applications where cost, flexibility, and lightweight construction are important.
Advantages of PET Heating Films
Cost-effective – PET is generally less expensive than PI.
Thin and lightweight – suitable for space-limited applications.
Good flexibility – can conform to curved surfaces.
Suitable for screen printing – carbon, graphene, and other conductive inks can be printed onto PET.
Good for low-temperature heating – suitable for applications such as battery preheating and anti-condensation.
Easy to customize – dimensions, resistance, heating patterns, wires, and adhesive backing can be customized.
Typical Applications
PET heating films are commonly considered for:
Battery heating
UAV and drone battery preheating
Anti-condensation heating
Consumer electronics
Packaging
Low-temperature equipment
Automotive components
What Is a PI Heating Film?
PI heating film uses polyimide (PI) as the substrate. PI is a high-performance engineering polymer known for its excellent thermal stability, electrical insulation, and resistance to harsh environments.
PI heaters can be manufactured using different heating technologies, including etched metal foil, wire-based designs, and certain printed heating technologies.
A typical flexible PI heater may have a structure such as:
PI Insulation Layer → Heating Circuit → PI Insulation Layer
Compared with PET, PI is generally selected when the application requires higher temperature capability or greater environmental durability.
Advantages of PI Heating Films
- Excellent temperature resistance
- Good dimensional stability
- Excellent electrical insulation
- Good flexibility
- Suitable for demanding industrial environments
- Can provide stable heating performance over a wide temperature range
- Suitable for applications requiring compact and reliable heaters
Typical Applications
PI heating films are widely considered for:
Aerospace and UAV equipment
Battery heating
Semiconductor equipment
Optical instruments
3D printers
Sensors and electronic components
Automotive electronics
Industrial equipment
PET vs. PI Heating Film: Key Differences
| Feature | PET Heating Film | PI Heating Film |
|---|---|---|
| Substrate | PET | Polyimide |
| Flexibility | Excellent | Excellent |
| Thickness | Very thin | Very thin |
| Temperature capability | Suitable for low/moderate temperatures | Higher temperature capability |
| Low-temperature environment | Good, depending on construction | Excellent |
| Dimensional stability | Good | Excellent |
| Chemical resistance | Moderate | Excellent |
| Electrical insulation | Good | Excellent |
| Screen printing | Very suitable | Suitable depending on process |
| Cost | Lower | Higher |
| Customization | Excellent | Excellent |
| Best suited for | Cost-sensitive, low-temperature applications | Demanding/high-temperature applications |
Which Is Better for Battery Heating?
For battery heating applications, both PET and PI heating films can be suitable. The better choice depends on the battery design and operating environment.
For example, if a UAV battery needs to be preheated from a low ambient temperature to approximately 40–50°C, a PET heating film can be a cost-effective solution when the overall temperature and environmental requirements are within the material's limits.
For applications exposed to very low temperatures, wider temperature fluctuations, or more demanding environmental conditions, PI may provide a larger performance margin.
However, the substrate is only one part of the heater design. The heating material, resistance, power density, adhesive, insulation layer, wiring, temperature sensor, and temperature control system should also be considered.
PET or PI: How Should You Choose?
A simple way to select the substrate is:
Choose PET when:
The target temperature is relatively low.
Cost is an important consideration.
The heater needs to be thin and lightweight.
Screen-printed carbon or graphene heating technology is preferred.
The application has relatively moderate environmental requirements.
Large-volume production is expected.
Choose PI when:
Higher temperature resistance is required.
The heater will experience significant temperature fluctuations.
The application has demanding environmental conditions.
Long-term reliability is a priority.
Space is limited and a high-performance flexible heater is required.
The application is in aerospace, industrial electronics, or other demanding environments.
PET vs. PI for UAV Battery Heating
For UAV and drone battery applications, the decision becomes particularly important because batteries may be exposed to cold outdoor environments.
For example, a UAV battery operating in a cold climate may require a flexible heater attached directly to the battery housing. The heater needs to be thin enough not to interfere with the battery installation while providing uniform heating.
A PET screen-printed heating film can be an attractive option for applications requiring moderate heating temperatures and cost-effective mass production.
A PI heating film may be preferred when the battery system requires greater thermal durability and more robust performance in harsh environments.
For either solution, temperature control is highly recommended. A temperature sensor such as an NTC or PT1000 can be integrated into the heating system to monitor battery temperature and prevent excessive heating.
Conclusion
There is no universal winner between PET and PI heating films.
PET heating films are generally attractive for cost-sensitive, thin, flexible, low-temperature applications, while PI heating films offer superior thermal stability and are better suited to demanding environments.
For applications such as UAV battery preheating, electronics, anti-condensation, and other low-temperature heating applications, PET can be a practical solution when its environmental limits are properly evaluated.
For high-temperature, aerospace, industrial, and harsh-environment applications, PI is often the more appropriate choice.
The most suitable heating film should ultimately be selected based on the operating temperature, voltage, power, dimensions, mounting method, environmental conditions, and required service life rather than simply choosing PET or PI based on the substrate material.
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