ASTM D3985 Oxygen Transmission Rate (OTR)
ASTM D3985 Oxygen Transmission Rate of Plastic Film and Sheeting
ASTM D3985 measures the amount of Oxygen that passes through a film in 24 hours. One side of the specimen is exposed to oxygen, the other to a nitrogen carrier stream, and a coulometric sensor counts every oxygen molecule that arrives. This number forms the basis for shelf life for oxygen-sensitive food, pharmaceutical blister packs, and electronic component packaging. MatX Lab performs OTR testing on films, laminates, coated substrates, and barrier structures aligned to ASTM D3985.
What Is ASTM D3985?
ASTM D3985 is the standard test method for oxygen gas transmission rate through plastic film and sheeting using a coulometric sensor. The specimen is clamped between two chambers, sealing them from each other.
Oxygen passes through the top chamber under atmospheric pressure. Nitrogen flushes the bottom chamber and transports whatever has permeated into it to the detector. Coulometric sensors react with oxygen present and generate current in proportion to its concentration, making the reading an absolute value rather than relative.
The results are measured in volume per unit area per day, generally in cubic centimeters per square meter per day for a one atmosphere difference in partial pressure. The standard is 23 degrees Celsius and dry, and this is an intentional oversimplification to help you understand the figure before using it.
ASTM D3985 Scope and Applications
The technique is applicable to films, sheets, laminates, coatings, and metalized structures that can be mounted and sealed under pressure. Another type of mounting device is needed for rigid containers.
Applications:
- Shelf life calculation. Feeding a permeation figure into an oxidation model for packaged food, beverage, or pharmaceutical product.
- Barrier structure development. Comparing EVOH content, layer thickness, metallization, and coating chemistry during structure design.
- Converting process verification. Detecting whether lamination, printing, or orientation damaged a barrier layer, which is a common and expensive problem.
- Incoming film verification. Confirming supplied film meets its stated barrier specification before it runs on a packaging line.
- Failure investigation. Testing film from a batch where packaged product spoiled early.
- Seal and defect screening. Identifying pinholes and coating discontinuities, which show up as an OTR far above what the structure should give.
Water vapor transmission is measured separately under ASTM F1249. ASTM D570 measures water absorption into the bulk polymer. MatX Lab reports measured values and does not certify products or act as a standards body.
D3985 Test Procedure
The two things that ruin OTR results are a leaking seal and calling a measurement finished before it reached steady state.
| Step | What happens |
| Specimen cutting | Specimens are cut oversize and handled by the edges, since a crease or pinhole anywhere in the test area dominates the result. |
| Thickness measurement | Thickness is measured at several points, because permeation scales inversely with it and the value is needed to normalize results. |
| Conditioning | Specimens are conditioned at the test temperature and humidity, which matters greatly for EVOH and polyamide barrier layers. |
| Mounting | The specimen is mounted in the cell with grease applied to the sealing surfaces, then clamped. Masking reduces the test area for very high barrier films. |
| Purging | Both chambers are purged with nitrogen until the residual oxygen signal falls to a stable baseline. High barrier films need many hours here. |
| Oxygen introduction | Oxygen or air is introduced to the upper chamber at a controlled flow, starting the permeation. |
| Steady state | The signal rises and is tracked until it plateaus. High barrier structures can take days to reach that plateau. |
| Calculation | Transmission rate is calculated at steady state, normalized to area and, where requested, to thickness. |
Limitations: Standard conditions are dry, and many barrier polymers behave completely differently when humid. Seal quality decides everything, since a leak at the clamp reads as permeation and always in the direction of the worse barrier.
Pinholes and flex cracks produce results that describe a defect rather than the material, which is useful information but has to be identified as such; the thickness normalization assumes a uniform monolithic film and is misleading on multilayer structures where one thin layer provides the barrier.
Permeation is highly temperature-dependent, so results obtained at 23 °C cannot be applied to a chilled or hot-fill application.
ASTM D3985 Specimen Requirements and Test Conditions
| Parameter | Typical requirement |
| Specimen form | Flat film, sheet, laminate, or coated substrate |
| Test area | Commonly 50 cm², masked down for very high barrier structures |
| Material required | Enough to cut three specimens plus spares, sent flat |
| Replicates | Two per condition minimum, three for high barrier structures |
| Temperature | 23 °C standard, other temperatures on request |
| Humidity | Dry as standard, humidified testing available as a modification |
| Duration | Hours for permeable films, days for high barrier structures |
| Orientation | Marked, with the product-contact side identified |
Send film flat and interleaved. Rolled film carries creases, and a crease through the test area produces an OTR that describes the handling rather than the structure.
Tell us the humidity your application involves.
A dry test on an EVOH or polyamide barrier will not represent a moist packaged product, and running the humidified condition is a different setup that has to be planned rather than added.
ASTM D3985 Test Results and Reporting
Your report gives oxygen transmission rate per specimen in cubic centimeters per square meter per day, with the test conditions stated as part of the result.
Specimen thicknesses are listed separately, while permeability per unit thickness is shown when normalization is needed because of the structure.
We note temperature, humidity, test surface, masking, and the time required to reach steady state because the latter indicates confidence in the plateau.
Where a specimen gave an anomalously high result, we describe what was found.
A pinhole, a crease, or a seal problem each produces the same symptom, and separating a defect from genuine material behavior is usually the point of the investigation.
ASTM D3985 FAQs
How long does a high barrier film take to test?
Not hours, but days. Both purging back to baseline and achieving steady state require more time as the barrier matures. Metal-coated and coated systems come under the category of the slower side, and the timetable must accommodate it.
What does a high result on one specimen mean?
Usually a defect rather than the material. Testing further specimens separates a one-off pinhole or flex crack from a structural problem in the barrier layer.