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D3985-24 – Standard Test Method Technical Guide
💨 Scope and Test Summary
The ASTM D3985-24 standard specifies a quantitative procedure for determining the steady-state rate of transmission of oxygen gas through plastics in the form of film, sheeting, laminates, coextrusions, or plastic-coated papers and fabrics. This test method utilizes a coulometric sensor to provide an accurate measure of the Oxygen Gas Transmission Rate (OTR) and the derived properties of oxygen permeance (PO2) and oxygen permeability coefficient (P’O2).
| 🟦 Measured Property | 📏 Symbol | 🎯 SI Unit | ⚡ Common Unit |
|---|---|---|---|
| Oxygen Transmission Rate | OTR | mol/(m²·s) | cm³(STP)/(m²·day) |
| Oxygen Permeance | PO2 | mol/(m²·s·Pa) | — |
| Oxygen Permeability Coefficient | P’O2 | mol/(m·s·Pa) | — |
⚙️ Key Terminology and Measurement Range
Specific terminology is critical for the correct application of this test method. The Oxygen Transmission Rate (OTR) is defined as the quantity of oxygen gas passing through a unit area of the parallel surfaces of a plastic film per unit time under the test conditions. The Oxygen Permeance (PO2) is the ratio of the OTR to the difference between the partial pressure of O2 on the two sides of the film. The Oxygen Permeability Coefficient (P’O2) is the product of the permeance and the thickness of the film.
⚠️ Important Restriction: The oxygen permeability coefficient (P’O2) is meaningful only for homogeneous materials. It should not be reported as a material property unless the relationship between thickness and permeance has been verified on tests using several different thicknesses of the specific material.
The method has been statistically validated for a wide range of barrier materials. Based on the Statistical Summary of Data provided in the standard, the testing procedure is effective for the following OTR range:
| 📐 Performance Metric | ⚡ Verified Range |
|---|---|
| Low End OTR | 0.063 cc/(m²·day) |
| High End OTR | 64.4 cc/(m²·day) |
| Detection Principle | Coulometric Sensor |
📊 Data Reporting and Unit Conversion
While SI units (mol/(m²·s)) are the standard for this test method, the commonly used unit for OTR in industry is cm³(STP)/(m²·day) at one atmosphere pressure difference. The standard provides exact conversion factors: one cubic centimeter of oxygen at STP is equivalent to 44.62 µmol, an atmosphere is 0.1013 MPa, and a standard day is 86.4 × 10³ seconds. The precise test conditions, including temperature and oxygen partial pressure, must always accompany the reported data. For testing under controlled relative humidity conditions, refer to the related standard ASTM F1927.
💡 Unit Conversion Tip: To convert an OTR value from the common barrier unit of cm³(STP)/(m²·day) to the SI standard of mol/(m²·s), multiply the recorded value by 5.163 × 10⁻¹⁰. This is crucial for comparing results derived from D3985 with data from methodologies using different reporting units.
❓ Frequently Asked Questions
🔍 Can D3985-24 be used for laminated or coated film structures?
Yes. The scope explicitly covers film, sheeting, laminates, coextrusions, and plastic-coated papers or fabrics. While OTR and Permeance can be reported for any structure, the Permeability Coefficient (P’O2) is strictly defined only for homogeneous materials.
© 2026 TNLab — This article is a technical interpretation for reference only. The original standard as published by ASTM International takes precedence.