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Fully compliant

ASTM D5946 / ISO 15989: corona treated polymer films using water contact angle measurements

Check how well corona treatment took on polymer film by reading the water contact angle, the measurement ASTM D5946 and ISO 15989 describe. A lower angle means a stronger treatment. The Dropometer runs this measurement at the line or in the lab, with ±0.35° accuracy (Dropometer product specification), on a drop shape method validated in two peer reviewed papers.

What brings you here?

Who this is for
Film converters, printers, laminators and resin or additive suppliers who check corona treated polymer film.
Compliance tier
Fully compliant: the Dropometer measures the static water contact angle this method describes.
Measurement
Sessile drop water contact angle, 10° to 175° range, ±0.35° accuracy (Dropometer datasheet).
Setup
About 2 minutes. Battery powered, 1 kg, runs at the line or in the lab.
Last updated
October 20, 2026
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Free one page checklist for ASTM D5946 / ISO 15989: what to prepare, the settings to lock, how many drops to place and what to record. Made for film QC benches.

Talk to an expert

Book a 15 minute demo on your film

Tell us your film, treater and current check. We will show the measurement live and tell you plainly where the Dropometer fits your QC plan and where it does not.

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View the official standard
Gurdeep-Saini-Photo
Written by
Gurdeep Singh Saini
Holds a BASc in Mechanical Engineering from Ryerson University (now Toronto Metropolitan University) and an MASc from York University. He develops the automatic edge and baseline detection behind the Dropometer's analysis.
COO at Droplet Lab
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Droplet-Lab logo
Technical Review by
Droplet Lab Team
Droplet Lab builds precision instruments and software for surface science measurement, specialising in contact angle analysis and surface tension characterisation. Used by researchers across materials science, pharmaceuticals, coatings, and advanced manufacturing, Droplet Lab's Dropometer has contributed to studies published in peer-reviewed journals including Advanced Functional Materials (Impact Factor 19). The team combines instrument engineering with deep domain knowledge in wettability science with a focus on practical accuracy.
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Verified against ASTM D5946/ISO 15989 WCA Measurement Corona-Treated Polymer Films
Gurdeep-Saini-Photo
Written By

Gurdeep Singh Saini

COO at Droplet Lab

Holds a BASc in Mechanical Engineering from Ryerson University (now Toronto Metropolitan University) and an MASc from York University. He develops the automatic edge and baseline detection behind the Dropometer's analysis.

Droplet-Lab logo
Reviewed By

Droplet Lab Team

Droplet Lab builds precision instruments and software for surface science measurement, specialising in contact angle analysis and surface tension characterisation. Used by researchers across materials science, pharmaceuticals, coatings, and advanced manufacturing, Droplet Lab's Dropometer has contributed to studies published in peer-reviewed journals including Advanced Functional Materials (Impact Factor 19). The team combines instrument engineering with deep domain knowledge in wettability science with a focus on practical accuracy.

Featured Studies & Publications

Research Paper Contact angle measurement with a smartphone
Research Paper Surface tension measurement with a smartphone using a pendant drop

Evidence box

Standard

ASTM D5946-24, Standard Test Method for Corona-Treated Polymer Films Using Water Contact Angle Measurements, from ASTM Subcommittee D20.19. ASTM states it is identical to ISO 15989:2004. Corona treatment is an electrical discharge treatment, one of several surface treating techniques used on polyolefins and other polymer films to increase the wetting tension, so that inks, coatings and adhesives wet and hold.

Compliance tier

Fully compliant. The Dropometer measures the static water contact angle on the treated film, which is what this method reads.

Instrument performance

Contact angle range 10° to 175°, accuracy ±0.35°, display resolution 0.01°, from the Dropometer product specification.

Peer reviewed method

The drop shape method is validated against a KRUSS DSA100E in two peer reviewed papers. See our validation publications.

Customer evidence

A labels and office products manufacturer uses the Dropometer to see how inks and adhesives wet film, paper, board and plastic. Read the case study.

What it does not tell you

ASTM notes that contact angle alone does not fully measure ink, coating or adhesive adhesion. Pair it with your adhesion test.

Executive summary

What this standard measures, who uses it and how the Dropometer fits

ASTM D5946 and ISO 15989 check corona treatment on polymer film by measuring the water contact angle: a lower angle means a stronger treatment. Film converters, printers and laminators use it for incoming and in process QC. The Dropometer is fully compliant with this measurement and reads each drop with ±0.35° accuracy.

The method uses deionised water on the treated side of the film. You read the contact angle of water droplets from the drop profile, repeat across the web, and compare the mean with your own limits. ASTM also gives a guide table that links angle ranges to the level of surface treatment.

The Dropometer contact angle and surface energy kit runs the test on battery power, so you can check film at the treater or in the lab. For a line focused workflow, see corona treatment monitoring for print quality. A labels manufacturer uses the Dropometer to check how inks and adhesives wet film, paper and board. For background on polymer films, read our plastics guide and the contact angle measurement guide.

Further reading: how to keep results comparable in reproducible contact angle measurement, what to look for in a goniometer for ISO and GLP regulated QC, reference values in surface free energy of common polymers, a classroom version in contact angle on treated and untreated surfaces, and why drying drops leave rings in the coffee ring effect.

How the Dropometer fits the contact angle measurement

The ASTM D5946 measurement, step by step, in our own words

From film sample to a recorded angle

These steps outline the procedure. They do not replace the standard. Buy the current edition and follow its drop volume, reading time and specimen rules.

±0.35°

Contact angle accuracy

From the Dropometer product specification. Display resolution is 0.01°.

About 2 min

Setup

Base plate, phone holder, LED and syringe. No PC needed.

8 h

Battery time

5 V battery only operation, so the unit can sit at the treater.

1

Take and mark the specimens

Cut strips across the web width and mark the treated side. Handle them by the edges. Skin oils change the angle. Condition them as the standard describes.

2

Set up the Dropometer

Place the base plate on a level bench, mount the phone and LED, and fill the Hamilton syringe with deionised water. Lay the strip flat on the sessile stage with the treated side up.

3

Place the drop

Dispense the drop volume the standard specifies onto the film. Keep the volume the same for every drop. Do not touch the film with the needle.

4

Capture and read the angle

Capture the drop at the reading time the standard sets. Automatic edge and baseline detection reads the left and right angles from the profile, so two operators get the same reading from the same image.

5

Repeat across the web

Place several drops at each position across the web. Treatment varies across the width and with surface texture, so one drop is not enough.

6

Record and compare

Record the mean, spread, positions, film grade, treatment date and room conditions. Compare the mean with your accept limit. If you also check the ink or fountain solution itself, see dynamic surface tension.

7

Watch the full measurement

This video shows a complete Dropometer contact angle measurement, from setup to result. It covers all the steps above in one run.

Dropometer contact angle measurement, start to finish.

Validated measurement approach

Independent benchmarking and publication-based validation references.

Peer reviewed method

The Dropometer drop shape method is validated against a KRUSS DSA100E in two peer reviewed papers, one in Review of Scientific Instruments and one in Colloids and Surfaces A. Published contact angle accuracy is ±0.35°.

Read the validation papers

Customer evidence

We have no published client paper on corona treated film yet. A labels manufacturer uses the Dropometer in two labs to check how inks, adhesives and coatings wet film and other substrates.

Read the case study

Set treatment limits from your own polymer film

ASTM D5946 · treatment level · film QC

ASTM gives a guide table that links water contact angle to treatment level. In summary: above 90° means little or no treatment, 85 to 90° is low, 78 to 84° is medium, 71 to 77° is high and below 71° is very high (source: ASTM D5946-24 summary).

ASTM also says each film and treatment needs its own capability study before you use the angle as a specification. So treat the table as a starting point. Measure film that printed and laminated well, and film that failed, then set your accept limit from that data.

Repeat the study when you change resin, slip additive or treater settings.

Example output: water contact angle across a BOPP polymer film

Example data for illustration only. These are not measured results. Your own film, treatment and limits decide the numbers.

Example: corona treated BOPP film, three positions across the web

Position Drops (n) Mean angle (°) Std dev (°) ASTM guide band Decision
Operator side574.21.1HighAccept
Centre576.80.9HighAccept
Drive side586.51.4LowHold the roll, check the treater

How to read this table

Each row is the mean of five drops at one position. The band column uses the ASTM guide table. The decision column uses an example accept limit of 78° or lower, set from a capability study.

Example output chart

The same example data as the table, plotted against the ASTM guide bands and an example accept limit.

Bar chart of example water contact angles at three web positions on corona treated BOPP film, with ASTM D5946 guide bands and a 78 degree accept limit

Example data, not measured results. Dashed lines are the ASTM D5946-24 guide band boundaries.

Business impact

What changes when the check is a measured angle

Metric Before Dropometer With Dropometer Results
How the check is made Dyne pens or test inks, read by eye Water contact angle read from the drop image No published benchmark
Result format Pass or fail at each ink level An angle per drop, 0.01° display, ±0.35° accuracy Dropometer product specification
Record Operator note Drop image and angle saved per measurement No published benchmark
Where it runs Shared lab goniometer At the treater, on battery for up to 8 h Dropometer product specification

See the measurement on your own film

Bring two rolls: one that printed well and one that did not. We will measure both live.

Book a 15 minute demo Request a quote
ROI estimate

Estimate the cost of the treatment failures this test can catch

Enter your own numbers. The defaults are examples, not Droplet Lab results.

Quality cost snapshot

Estimate what wetting related failures cost you.

Example only. Use what you see in a trial on your own samples.
Your own figure.
Your own estimate.

Result

~0
Estimated annual cost today
~0
Estimated annual cost avoided
~0
Payback period

Annual exposure combines audit/CAPA cost, customer rejections, and recall probability; avoided exposure applies the risk reduction percentage.

Measurement settings for polymer film

Lock these before you compare results between shifts or sites

Parameter Recommended Setting Technical Rationale
Test liquid Deionised water This is a water contact angle method. Other liquids belong to other standards.
Drop type Sessile drop, static angle The method reads a resting drop on the treated side.
Drop volume As the standard specifies, fixed for every drop A changing volume adds spread that is not about treatment.
Reading time As the standard specifies, fixed for every drop Water can spread or evaporate on the film, so the time must not vary.
Fit model Young-Laplace or polynomial, the same for every run Both models are in the Dropometer software. Do not mix them within one study.
Replicates Several drops at each position across the web ASTM notes treatment and roughness vary, so multiple measurements are needed.
Side tested Treated side, marked before cutting The untreated side reads a much higher angle.
Environment Record room temperature and humidity The Dropometer runs at 10 to 45 °C and has no temperature control.

Is ASTM D5946 the right test method?

Pick the method by the question you need answered

Start: What do you need to know about the treated surface?

Treatment level as a number

Signals:

You want a measured value per roll for film QC or treater control.

Rule-out:

Use ASTM D5946 / ISO 15989, this page. The Dropometer is fully compliant.

Fast pass or fail in mN/m

Signals:

Your customers specify a wetting tension in mN/m and you need a fast check at the line.

Rule-out:

Use test inks to ISO 8296. Contact angle complements that check.

Surface free energy with polar and dispersive parts

Signals:

You need to know why a coating or adhesive fails, not just whether treatment is present.

Rule-out:

Use a two liquid method such as ASTM D7490.

Paper or board, not film

Signals:

Your substrate absorbs water over time.

Rule-out:

Use TAPPI T 458 / ASTM D724.

Decision tree at a glance

Start from the question you need answered. Blue boxes are measurements the Dropometer runs.

Decision tree for choosing between ASTM D5946 water contact angle, ISO 8296 test inks, a two liquid surface energy method and TAPPI T 458

Pick the method by the question you need answered.

Interpreting contact angle measurement results

What the angle tells you, and what it does not

Lower angle, stronger treatment: Corona treatment adds polar functionalities to the polymer film surface and raises its wetting tension and surface energy, so water spreads more and the angle drops.
Spread across the web matters: A good mean with one high position points to a treater or electrode problem on that side.
Treatment can fade: Record treatment date and test date. Film tested weeks later can read higher than at the line.
Angle is not adhesion: A low angle shows the surface wets. It does not prove an ink or adhesive will bond.
Expert perspective

Why water contact angle tracks treatment

What a liquid responds to is only the outermost few ångström of a surface: the skin, not the bulk. Change that skin and you change the wetting, even if the material underneath is identical.

Dr. Alidad Amirfazli

Department of Mechanical Engineering, York University, Co-founder and Scientific Advisor, Droplet Lab

Common pitfalls and limits

Honest limits of the method and of the Dropometer

Fingerprints, gloves with powder and slip additive bloom all raise the angle. Handle strips by the edges.
Rough or embossed film gives an apparent angle that reflects texture as well as treatment.
The Dropometer has no temperature or humidity control. Record room conditions and keep them steady.
The camera runs at 10 frames per second. That suits a reading at a fixed time, not millisecond spreading studies.
The guide table is a starting point. ASTM says each film and treatment needs its own capability study.
FAQ

Frequently asked questions

Is ASTM D5946 the same as ISO 15989?

Yes, in content. ASTM states that D5946 is identical to ISO 15989. Both measure the water contact angle on corona treated polymer film. Check which designation your customer names in the specification, and quote that one in your test report.

What water contact angle shows good corona treatment?

ASTM gives a guide: above 90° means little or no treatment, 78 to 84° is medium and below 71° is very high. ASTM also says each film needs its own capability study. Set your accept limit from film that printed and laminated well.

Can the Dropometer run ASTM D5946?

Yes. The Dropometer measures the static water contact angle on the treated film, which is what the method reads. Accuracy is ±0.35°. Buy the current edition of the standard, follow its drop volume and timing, and validate the method in your own lab.

How is this different from dyne pens?

Dyne pens and test inks give a pass or fail at set wetting tension levels, judged by eye. ASTM D5946 gives a measured angle per drop. Many converters use both: inks for a fast check, contact angle for a number they can trend. See ISO 8296.

Does a low contact angle guarantee ink adhesion?

No. A low angle shows the surface wets well. ASTM notes that contact angle alone does not fully measure ink, coating or adhesive adhesion. Keep your tape or peel test, and use the angle to catch treatment problems early.

How many drops should I measure?

More than one at each position. Treatment and surface roughness vary across the web, so ASTM calls for multiple measurements. Many labs place several drops at operator side, centre and drive side, then compare the means.

Legal note

This page summarises ASTM D5946 and ISO 15989 in our own words and does not reproduce either standard. Buy the current edition from ASTM or ISO before you write a procedure. Droplet Lab does not certify compliance. Your own method validation does.

View the official standard Book a 15 minute demo

How this page was created

Sources, review and tools

Transparency 4 checklist items
01

Sources

ASTM D5946-24 summary from ASTM, ISO 15989:2004 listing from ISO, the Dropometer product specification and Droplet Lab validation papers.

02

Drafting assistance

Drafted with Claude (Anthropic) from the sources listed, then reviewed by Droplet Lab.

03

What we did not do

We did not copy text from the standard. Buy the current edition for the full procedure.

04

Last checked

October 2026

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Correction Request

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References

1. ASTM International. ASTM D5946-24, Standard Test Method for Corona-Treated Polymer Films Using Water Contact Angle Measurements. store.astm.org/d5946-24.html
2. ISO. ISO 15989:2004, Plastics: Film and sheeting: Measurement of water-contact angle of corona-treated films. iso.org/standard/29046.html
3. Droplet Lab. Peer reviewed validation papers in Review of Scientific Instruments and Colloids and Surfaces A. dropletlab.com/validation/publications/
4. Droplet Lab. Dropometer product specification, 2026. dropletlab.com/products/dropometer/