COF of PET film is used to describe the friction behavior of polyester film surfaces during starting and sliding contact. In technical data, it is typically reported as static COF and kinetic COF under a defined method such as ASTM D1894 or ISO 8295. Public PET and polyester film datasheets show that reported values vary by grade, surface, and structure, so the result should be read as application-specific data rather than as a universal benchmark.
Key Friction Values
Property | Typical Reported Range | Common Method |
Static COF | 0.30–0.60 | ASTM D1894 |
Kinetic COF | 0.20–0.55 | ASTM D1894 |
Mid-range industrial reference | 0.35–0.55 / 0.30–0.45 | ASTM D1894 |
Alternative reporting | By product grade | ISO 8295 |
These figures reflect public technical sheets and should be treated as reference-style data only. Exact values can shift with tested side, coating, texture, and contact pairing.
Static vs. Kinetic
- Static COF: force required to start movement
- Kinetic COF: force required to maintain movement after sliding begins
Both values matter because start-up behavior and continuous running behavior are not always the same. ASTM D1894 is specifically used to determine static and kinetic coefficients of friction of plastic film and sheeting.
Public Reference Examples
Public Example Type | Static | Kinetic / Dynamic |
Coated polyester sample | 0.41 | 0.34 |
Coated polyester sample | 0.36 | 0.30 |
Surface-specific polyester sample | 0.40 | 0.37 |
Base film side example | 0.50 | 0.45 |
Lower-friction polyester sample | 0.30 | 0.2 |
Higher-friction coated sample | 0.60 | 0.55 |
Technical Data Table
Item | Unit | Typical Data |
Film Type | — | PET Film |
Static COF | — | 0.35–0.55 |
Kinetic COF | — | 0.30–0.45 |
Test Method | — | ASTM D1894 |
Alternative Method | — | ISO 8295 |
Surface Pairing | — | Film-to-film / specified side |
Thickness Range | μm | By grade |
Haze | % | By grade |
Tensile Strength MD | psi / MPa | 36,000–41,000 psi in public examples |
Tensile Strength TD | psi / MPa | 36,000–38,000 psi in public examples |
Elongation MD | % | 100–145 in public examples |
Surface Tension | dyne | 36 in one public example |
Variables That Shift the Result
Measured friction can change with:
- surface roughness
- matte or glossy finish
- coating or primer layer
- treated side versus reverse side
- slip-modified versus standard surface
- contact pairing
- temperature and humidity
- specimen preparation
ISO 8295 also notes that friction testing is mainly a quality-control method and does not fully reproduce all machine conditions in real processing.
How to Use the Data
Result Pattern | Practical Meaning |
Lower values | Easier sliding and smoother travel |
Mid-range values | Balanced movement and control |
Higher values | More hold or anti-slip behavior |
A useful evaluation normally includes static value, kinetic value, method, tested side, and contact pairing. This gives a stronger basis for process selection than one isolated number.
For adhesive converting, labelstock, die cutting, and electronics liner applications, this COF data can be used together with our Siliconized Film Release Liners product specifications.
FAQ
What is COF in PET film?
It is the measured friction level of the film surface during starting and sliding contact.
What is a common reported range?
Public technical sheets commonly show static values around 0.30–0.60 and kinetic values around 0.20–0.55, depending on structure and surface design.
Which test methods are commonly used?
ASTM D1894 and ISO 8295 are the most common methods used for plastic film friction testing.
Why can the two sides of one film test differently?
The two surfaces may differ in coating, treatment, texture, or function, so each side can produce a different measured result.