The melting point of PET film is generally 250°C–265°C, with 255°C–260°C used as a common industrial reference range. This value shows when the crystalline PET base film begins to melt. In actual converting, the film should not be judged by melting point alone. More practical data include PET film service temperature, glass transition range, thermal shrinkage, MD/TD dimensional stability, coating heat limit, surface treatment, and thickness tolerance. PET film may stay solid at high temperature, but it can still shrink, curl, or lose flatness before reaching its melting range.
Quick Data Snapshot
Item | Typical Data |
Material | Polyethylene terephthalate film |
Common name | PET film / polyester film |
Typical melting range | 250°C–265°C |
Practical melt reference | 255°C–260°C |
Glass transition range | 70°C–85°C |
Common working range | 120°C–150°C |
Short-term heat exposure | 180°C–240°C, depending on grade and time |
Density | 1.35–1.40 g/cm³ |
Thermal conductivity | 0.13–0.15 W/m·K |
Common shrinkage test | 150°C / 15–30 min |
Melting point test method | DSC / DTA |
Technical Overview
PET film is used where a thin film needs stable thickness, good tensile strength, clean surface quality, electrical insulation, and better heat resistance than PE or PP film. The PET film melting temperature is high, but the working limit is normally much lower than the melt range.
In factory sample checks, the first heat-related issue is usually not melting. More common problems are curl, edge wave, size change, web tension change, coating softening, or poor flatness after heating. For this reason, useful polyester film thermal data should show both the melt range and real processing behavior.
Core Technical Data
Property | Typical Value | Practical Meaning |
PET film melting temperature | 250°C–265°C | Base resin melting range |
Glass transition temperature | 70°C–85°C | Film stiffness may begin to reduce |
PET film service temperature | 120°C–150°C | Common long-use reference for many grades |
Short-term heat resistance | 180°C–240°C | Needs grade and process confirmation |
Heat shrinkage | 0.5%–3.0% | Depends on heat setting and MD/TD direction |
Tensile strength | 150–250 MPa | Affects slitting, die cutting, and web handling |
Elongation at break | 80%–170% | Changes with thickness and orientation |
Thickness tolerance | Usually ±3% to ±10% | Affects insulation gap and die-cut precision |
Surface treatment | Untreated / corona / chemical treated | Affects ink, coating, adhesive bonding |
Coating heat limit | Depends on coating system | May fail earlier than the PET base film |
Temperature Behavior Guide
Temperature Range | Expected Film Behavior |
Below 70°C | Film usually keeps good stiffness and flatness |
70°C–85°C | Near glass transition range; stiffness may reduce |
100°C–130°C | Shrinkage, curl, or tension change may appear |
130°C–150°C | Common upper working range for many industrial uses |
150°C–180°C | Short-time exposure; sample testing is recommended |
180°C–240°C | Special process conditions only |
250°C–265°C | Typical PET base film melting range |
Above 300°C | Thermal decomposition risk increases |
The melting point of PET film should not be treated as the maximum working temperature. A film with a melt reference near 260°C may still deform at 120°C–150°C if the grade is not heat-stabilized, the web tension is too high, or the heating time is too long.
Thermal Shrinkage Control
The thermal shrinkage of PET film is often more important than the melt range for printing, coating, lamination, insulation, and die-cut applications. PET film is stretched and oriented during production. When heat releases internal stress, the film can shrink before it melts.
Shrinkage Level | Practical Meaning |
Below 0.5% | Better for precision die cutting, lamination, and tight registration |
0.5%–1.5% | Acceptable for many standard converting processes |
1.5%–3.0% | Needs testing for flatness, curl, and size change |
Above 3.0% | Higher risk for wrinkle, misalignment, and unstable roll tension |
MD and TD shrinkage should be checked separately. MD shrinkage affects web length, tension, and die-cut size. TD shrinkage affects width stability, edge flatness, and lamination alignment. Uneven MD/TD shrinkage is a common reason for curl after heating.
Data to Confirm Before Use
If your application needs a transparent PET film for display panels, touch screens, or electronic assemblies, this thermal data can support selection of our high temperature polyester film.
Use Condition | Main Data to Confirm |
Hot air drying | Temperature, dwell time, MD/TD shrinkage |
Printing | Surface energy, drying temperature, ink adhesion |
Coating | Coating heat limit, surface treatment stability |
Release liner | Base film flatness, release layer temperature limit |
Electrical insulation | Thickness tolerance, dielectric strength, service temperature |
Thermal lamination | Heat time, pressure, shrinkage, cooling flatness |
Die-cut parts | Thickness tolerance, tensile strength, dimensional stability |
Industrial tape carrier | PET film heat resistance, coating adhesion, roll stability |
For coated PET film, heat performance should not be judged only by the base film. The coating, adhesive, ink, release layer, or primer may have a lower heat limit than the PET substrate.
Practical Testing Conditions
A lab value is useful, but final performance should be checked under real process conditions. In factory testing, temperature alone is not enough. The same film may behave differently when pressure, dwell time, web tension, roll width, or coating structure changes.
Test Factor | Recommended Check |
Temperature | Match actual machine temperature |
Time | Use real dwell time, not only peak temperature |
Pressure | Important for lamination and hot-press use |
Web tension | High tension can increase deformation risk |
Cooling method | Uneven cooling may affect flatness |
Coating layer | Check whether coating fails before base PET |
Roll width | Wide rolls are more sensitive to edge wave |
Final structure | Test the coated or laminated structure, not only raw film |
Extra testing is recommended for long exposure above 150°C, direct hot-plate contact, strict shrinkage requirements below 0.5%, high-pressure lamination, adhesive curing, or coated film used near the coating temperature limit.
FAQ
What is the melting point of PET film?
The melting point of PET film is usually 250°C–265°C. Many industrial polyester films use 255°C–260°C as a practical technical reference.
Is PET film melting temperature the same as service temperature?
No. PET film melting temperature is the base polymer melting range. PET film service temperature is much lower and is more useful for real processing.
What is the normal PET film service temperature?
For many industrial grades, PET film service temperature is commonly around 120°C–150°C. Higher short-term exposure depends on grade, thickness, coating, tension, and heating time.
Why does PET film shrink before it melts?
PET film is oriented during production. Heat can release internal stress, causing shrinkage, curl, or tension change before the film reaches its melting point.
Which data is more important than melting point in heated processing?
Thermal shrinkage, MD/TD stability, service temperature, coating heat limit, thickness tolerance, tensile strength, and real machine testing are more important for final performance.