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Dyne level (wetting tension)

Pronunciation: /daɪn ˈlɛvəl/

Dyne level is the wetting tension of a solid surface, expressed in dyn/cm (equal to mN/m). It is the surface tension of the test liquid that just wets the surface, found by applying a series of liquids of known surface tension and seeing which one holds a continuous film.

Also called

Wetting tension Dyne value Dyne test Treatment level

Related terms

Critical surface tension (Zisman) Surface free energy

Topics

Surface energy Wetting Surface treatment
Book a 15 minute demo Read the surface energy measurement guide

At a glance

What a dyne number means, where it comes from and what it can and cannot tell you.

What it is

A dyne level is a pass or fail wetting result turned into a number. You apply test liquids of rising surface tension until one no longer wets the surface. The highest value that still wets is the dyne level.

  • Units: dyn/cm, numerically equal to mN/m
  • Common on polymer films after corona, flame or plasma treatment

Typical values

Rough guide for polymer films at room temperature:

  • Untreated polyethylene: about 30 to 32 dyn/cm, close to its Zisman critical surface tension of about 31 mN/m
  • ASTM D2578 notes that 35 dyn/cm or higher has generally indicated adequate treatment for some tubular polyethylene film in flexographic printing
  • Many printers work to 38 dyn/cm or more

Our surface free energy of common polymers dataset lists comparable values.

How it is measured

Dyne inks and dyne pens apply liquids of known surface tension and you judge by eye whether the film holds or breaks into drops. Contact angle is the other route: it gives an angle with each liquid and, with two or three liquids, a full surface energy. The surface energy measurement guide explains that method.

Expert view

“Because only the top few ångström decide wetting, an invisible contaminant film, even a monolayer picked up from the air, is enough to change how a liquid behaves on the surface.”

Dr. Alidad Amirfazli, Co-founder and Scientific Advisor, Droplet Lab

What the terms mean

What you see on the film when a test liquid is below, at or above the dyne level.

Test liquid below the dyne level

The liquid wets the surface and stays as a continuous film. The wetting tension of the surface is at least this value.

Test liquid at the dyne level

The highest surface tension liquid that still holds a continuous film for the set time. Its surface tension is reported as the wetting tension.

Test liquid above the dyne level

The film shrinks back or breaks into droplets within moments. The surface energy is too low for this liquid to wet it.

A dyne test reads the point where cos θ reaches 1 for a series of liquids. It does not measure θ itself.

γLV Surface tension of the test liquid, mN/m (equal to dyn/cm)
γc Zisman critical surface tension of the solid, mN/m
θ Contact angle of the test liquid on the solid, degrees
dyn/cm Dyne per centimetre; 1 dyn/cm = 1 mN/m

Key equations

How a dyne number connects to contact angle and surface energy.

Equation: dyne level ≈ γLV of the highest liquid with cos θ → 1

Variable legend:

  • γLV: surface tension of the test liquid (mN/m or dyn/cm)
  • θ: contact angle of that liquid on the solid (°)

Interpretation: The surface just wets with a liquid of this surface tension. Liquids with higher surface tension bead up.

When to use: Use it to compare treatment levels on the same material with the same ink set.

Assumptions:

  • Test liquids of a single, consistent chemistry
  • Fresh inks and a clean, dry surface

Common mistakes:

  • Treating the number as the full surface free energy of the solid
  • Comparing dyne levels from different ink families without noting it

Equation: cos θ = 1 at γLV = γc

Variable legend:

  • γc: critical surface tension found by extrapolating cos θ against γLV to cos θ = 1 (mN/m)

Interpretation: The dyne test is a quick, visual cousin of the Zisman plot. Both look for the surface tension at which a liquid just spreads.

When to use: Use it to see why a dyne level and a Zisman critical surface tension often land close together.

Assumptions:

  • A homologous or consistent series of test liquids

Common mistakes:

  • Expecting either number to split polar and dispersive parts

How to read it

What a dyne result usually tells you on a converting or bonding line.

A dyne level is a threshold, not a full description of the surface. It says whether a liquid of a given surface tension will wet, not how strongly an ink or adhesive will bond. Our article Beyond 38 dynes: what surface energy really tells you about adhesion covers that gap. Students can see the effect of treatment in experiment 4 on contact angle of treated and untreated surfaces.

From dyne result to meaning

If you see It usually means Check next
Dyne level at the untreated value Treatment did not reach the surface or has faded Treater power, line speed, and time since treatment
Dyne level meets target but ink still lifts Wetting is fine but adhesion depends on more than wetting Polar part of surface energy, ink chemistry, cure
Different results from different operators The visual end point is being judged differently Shared criteria for film break and timing
Dyne level drops over days or weeks Treatment decay or additive migration to the surface Storage time and slip or antistatic additives

Common misconceptions

Where dyne numbers are most often over read.

The dyne level is the surface energy of the material

ASTM D2578 itself states that wetting tension is not a fundamental property of the surface. It depends on the test liquids used. Surface free energy, found from contact angles with two or three liquids, also splits into polar and dispersive parts.

Wetting tension here means the same as γSV − γSL

In the Young equation, the same words describe γLV cos θ for one liquid. In a dyne test, wetting tension is the surface tension of the liquid that just wets. The two are related but are not the same number.

Passing the dyne target guarantees good adhesion

Wetting is necessary for adhesion but not sufficient. Two films can share a dyne level and still bond differently because their polar character differs. A comparison of contact angle measurement and dyne pens sets out what each method reports.

Any dyne pen gives the same answer

Results depend on ink chemistry, ink age, contamination of the pen tip and how the end point is judged. Use one ink family, replace inks on schedule and record which you used. Contact angle results from several liquids can be checked with our surface free energy calculator.

Related terms

Where the dyne level sits among other wetting and surface energy terms.

Broader term

  • Wettability
  • Surface free energy

Related terms

  • Critical surface tension (Zisman)
  • Surface free energy
  • Corona treatment
  • Contact angle

Often confused with

  • Surface tension of a liquid
  • Wetting tension in the Young equation

FAQ

Short answers to the questions people ask most about dyne levels.

What does 38 dyne mean?

It means the surface is wetted by a test liquid with a surface tension of 38 dyn/cm, which equals 38 mN/m. Many printers and converters use 38 dyn/cm as a working target for polymer films before printing or laminating. It is an industry rule of thumb rather than a physical limit.

What standard covers dyne testing?

ASTM D2578 is the Standard Test Method for Wetting Tension of Polyethylene and Polypropylene Films. It uses mixtures of formamide and ethyl Cellosolve of known surface tension. ISO 8296 covers determination of wetting tension for plastics film and sheeting. Commercial dyne pens and dyne inks apply the same idea in a handy format.

How is a dyne level different from contact angle?

A dyne test gives one threshold: the highest liquid surface tension that still wets. A contact angle measurement gives an angle for each liquid, which shows how far a surface is from wetting. With two or three liquids, contact angles also give the surface free energy and its polar and dispersive parts.

References

Standards and primary sources.

1. ASTM D2578-23. Standard Test Method for Wetting Tension of Polyethylene and Polypropylene Films. ASTM International, West Conshohocken, PA. https://store.astm.org/d2578-23.html
2. ISO 8296:2003. Plastics: Film and sheeting: Determination of wetting tension. International Organization for Standardization, Geneva.
3. Zisman, W. A. (1964). Relation of the equilibrium contact angle to liquid and solid constitution. In Contact Angle, Wettability, and Adhesion, Advances in Chemistry, Vol. 43, American Chemical Society, 1 to 51. https://doi.org/10.1021/ba-1964-0043.ch001
4. Surface energy measurement guide
5. Critical surface tension (Zisman)
6. Surface free energy