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D2136-19 – Standard Test Method Technical Guide
ASTM D2136-19 defines a standard pass/fail test method for evaluating the low-temperature flexibility of coated fabrics. Fabrics coated with rubber or rubber-like materials stiffen at low temperatures, and this test determines if they can withstand a prescribed bend without fracturing or cracking.
📐 Apparatus and Specimen Requirements
The testing apparatus consists of a low-temperature chamber, a standardized bending fixture, and glass plates for conditioning. The chamber must maintain a uniform atmosphere of cold dry air or gas to within ±1°C (±1.8°F) of the set temperature and must be large enough to operate the bending fixture internally. Glass plates, approximately 125 by 175 mm (5 by 7 in.), are used to condition the coated fabric specimens prior to testing.
| 🟦 Component | 📏 Specification | 🎯 Critical Requirement |
|---|---|---|
| Low-Temperature Chamber | Uniform dry air / gas atmosphere | Tolerance of ±1°C (±1.8°F) |
| Bending Fixture | Per Fig. 1 and Fig. 2 (ASTM D2136 adjunct) | Stable horizontal base, prevents tipping |
| Glass Plates | ~125 × 175 mm (5 × 7 in.) | Sufficient quantity for all specimens |
⚙️ Test Procedure and Environmental Conditions
Test specimens are conditioned at the selected low temperature for the specified duration. While still exposed to the low temperature inside the chamber, each specimen is placed in the bending apparatus and bent through the specified angle. The standard does not mandate a single universal temperature or angle; these parameters are selected based on the material’s intended use or procurement specification.
⚠️ Critical Procedural Note: The bending operation must be performed entirely within the low-temperature chamber. Removing the specimen for bending can invalidate the results due to temperature rise, which compromises the integrity of the test.
📊 Key Measured Properties and Interpretation
The primary output is a simple Pass/Fail result. The specimen is examined for any signs of physical damage immediately after the bend is executed.
| ⚡ Result Type | 🔍 Observable Indicator | 📌 Consequence |
|---|---|---|
| Fail | Fracture of the specimen or surface cracks in the coating. | Unacceptable for use at that temperature. |
| Pass | No visual fracture or cracking of the coating. | Satisfies test requirements for that temperature. |
💡 Significance Note: This test method is suitable for specification conformance but, as stated in Section 4.1, it does not necessarily indicate the lowest temperature at which the material may be used. It is strictly a pass/fail assessment under very specific deformation conditions.
Failure directly indicates the unacceptability of the coated fabric for use at that specific test temperature under the defined deformation parameters.
❓ Frequently Asked Questions
🔍 What constitutes a failure in ASTM D2136?
A failure is indicated by the fracture of the test specimen or the appearance of surface cracks in the coating upon bending at the specified low temperature.
💡 What is the required temperature tolerance for the chamber?
The standard requires the chamber to maintain the selected low temperature within a tolerance of ±1°C (±1.8°F).
⚡ Can this test determine the absolute lowest service temperature of a coated fabric?
No. Section 4.1 explicitly states the test does not necessarily indicate the lowest temperature at which the material may be used. It predicts behavior only under deformation conditions similar to the test.
📌 Which unit system is the standard for reporting results?
According to Section 1.2, the values stated in SI units are to be regarded as the standard. The values provided in parentheses (inch-pounds) are for information only.