What Dyne Level Is Required for Printing on Plastic Films?
Successful printing on plastic films depends heavily on surface energy. When the surface energy of a substrate is too low, inks cannot properly wet the material, resulting in poor adhesion and print defects.
Dyne levels are used to measure the surface energy of a substrate. The higher the dyne level, the easier it is for inks, coatings, and adhesives to spread evenly across the surface.
In most printing applications, the dyne level of the substrate must be higher than the surface tension of the ink to achieve proper wetting and adhesion.
Typical Dyne Levels Required for Printing
Different materials require different surface energy levels for reliable printing performance.
| Material | Typical Dyne Level Required |
|---|---|
| Polyethylene (PE) | 38 dynes/cm minimum |
| Polypropylene (PP) | 38–42 dynes/cm |
| PET | 42–50 dynes/cm |
| Nylon | 46–56 dynes/cm |
For most flexographic printing and gravure printing applications, a surface energy level of 38 dynes/cm or higher is considered the minimum acceptable value.
Higher dyne levels may be required for certain coatings or high-performance inks.
Why Untreated Plastics Are Difficult to Print
Many plastics used in packaging have inherently low surface energy.
For example:
untreated polyethylene: 30–32 dynes/cm
untreated polypropylene: 29–31 dynes/cm
These values are significantly lower than the surface tension of most inks, which prevents proper wetting.
To overcome this problem, plastics are commonly treated using corona discharge, flame treatment, or plasma treatment.
How Corona Treatment Improves Printability
Corona treatment modifies the polymer surface by introducing polar functional groups that increase surface energy.
This allows inks and coatings to spread evenly across the substrate, improving:
ink anchorage
coating uniformity
adhesive bonding.
However, the effect of corona treatment can decrease over time due to corona treatment decay, which causes the dyne level to gradually decrease during storage.
How to Verify Surface Energy Before Printing
The most common method used in production environments to verify surface energy is dyne testing.
Dyne test pens allow operators to quickly confirm whether the surface energy of the film meets the required level for printing.
If the dyne test fluid forms a continuous film for approximately two seconds, the surface energy is equal to or higher than the dyne level of the pen.
If the fluid beads up or retracts, the surface energy is below the tested level.
Best Practices for Maintaining Proper Dyne Levels
To ensure consistent printing quality, converters often follow several quality control procedures:
test dyne levels before printing
avoid contamination during handling
store treated films properly
monitor corona treatment levels during extrusion.
Regular surface energy testing helps prevent adhesion failures and ensures consistent print performance.
Conclusion
Dyne levels are a critical parameter in printing on plastic films. Most flexographic and gravure printing applications require surface energy levels of at least 38 dynes/cm to ensure proper ink wetting and adhesion.
Because surface energy can change over time, regular testing with dyne test pens is essential for maintaining consistent print quality.
