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D3199-84 – Standard Test Method Technical Guide
🧪 Overview and Scope
ASTM D3199-84 (Reapproved 1994) defines a standardized test method for measuring the water vapor transmission (WVT) rate through screw-cap closure liners. This method is critical for evaluating the barrier efficiency of liner materials used in packaging, specifically for determining suitability for moist or dry products.
The test involves sealing containers with the liner under evaluation and periodically weighing them to measure moisture gain or loss under controlled conditions of temperature and humidity. The standard explicitly covers transmission both into and outward from a container.
⚠️ Mandatory Caveat: This standard does not purport to address all safety concerns. Users must establish appropriate safety, health, and regulatory practices before use.
🔧 Essential Apparatus and Specimen Requirements
The accuracy of the D3199 test hinges on strict adherence to apparatus specifications and specimen preparation.
| 🟦 Apparatus | 📐 Specification |
|---|---|
| Test Bottles | 1/2 to 1 oz (15-30 cm³), 28mm GPI 400 or 405 finish |
| Screw Caps | 28mm Continuous Thread (CT), Metal or Plastic |
| Torque Tester | Accuracy to within ± 1/2 lbf·in (0.06 N·m) |
| Analytical Balance | Accuracy to at least 0.001 g |
| Humidity Cabinet | ± 1.8°F (±1°C), ±2% RH at 100°F (38°C) |
| Pipet or Graduate | Accuracy to ±0.1 mL for 10 mL volume |
Specimens must be die-cut uniformly without distortion, with no torn or wrinkled liners. A minimum of ten test specimens and ten control specimens is required for each liner evaluation.
⚖️ Test Procedure: Inward vs. Outward Transmission
The method defines two distinct test modes to evaluate the liner’s barrier properties under different use-case scenarios.
| ⚡ Test Mode | 🎯 Condition |
|---|---|
| Outward (8.1) | Container filled with 10 mL water, sealed with lined cap, exposed to low humidity (25% RH at 100°F). |
| Inward (8.2) | Container filled with desiccant (e.g., activated silica gel, Grade H, Type 46, 16 mesh), sealed with lined cap, exposed to high humidity (75% RH at 100°F). |
Tare the weight of each bottle with its lined closure. For the Outward test (8.1), five containers are used. For the Inward test (8.2), five containers are used. Periodic weighings track the moisture gain or loss over time.
💡 Pro Tip: Prior to sealing, ensure the liner backing is properly laminated and adhered (plastic caps) or forced in (metal caps). Select test bottles for uniformity of flatness of finish, and apply caps following standardized torque methods per ASTM D3198 to ensure reproducible results.