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D3137-81 – Standard Test Method Technical Guide
ASTM D3137 – 81 (Reapproved 2018) establishes a definitive standard test method for evaluating the hydrolytic stability of vulcanized rubber. This procedure rigorously assesses a material’s ability to withstand the degradative effects of high humidity and elevated temperature. By measuring the change in tensile strength after exposure over distilled water, this method provides critical comparative data for research, development, and quality control in applications where moisture resistance is paramount.
📐 Scope and Significance of the Test
The primary objective of this test method is to determine the ability of rubber to resist environmental degradation in moisture-laden atmospheres. It is specifically designed for test specimens cut from standard vulcanized sheets prepared in accordance with Practice D3182. The accelerated conditions of high humidity and elevated temperature allow for the assessment of performance properties over time. While service conditions vary, this method yields reliable comparative data for judging service quality and is highly valuable in research and development. It is important to note that climactic variations in service may mean results do not correlate exactly with field performance.
⚠️ Important Limitation: This test method is explicitly not applicable to coated fabrics. Its use for materials other than solid rubber has not been established within the scope of this standard.
⚙️ Test Procedure and Exposure Conditions
Specimens are subjected to a controlled humid environment to accelerate hydrolytic degradation. The core procedure involves exposing the material over distilled water, followed by a precisely specified conditioning period before tensile testing. Adherence to these strict parameters is essential for reproducibility.
| 📏 Parameter | ⚡ Specified Value |
|---|---|
| Test Temperature | 85 ± 1°C (185 ± 2°F) |
| Exposure Period | 96 ± 1 hour |
| Exposure Environment | Over distilled water (high humidity) |
| Post-Exposure Conditioning Time | 16 to 96 hours |
| Conditioning Temperature | 23 ± 2°C (73.4 ± 3.6°F) |
| Conditioning Relative Humidity | 50 ± 5 % |
💡 Best Practice: For maximum reproducibility, laboratories should standardize the post-exposure conditioning period within the allowed 16 to 96 hour window. Consistent conditioning minimizes variances in the subsequent tensile testing, which is performed according to Test Methods D412.
📊 Key Measured Properties and Referenced Standards
The core metric for determining hydrolytic stability is the measured change in tensile strength after controlled environmental exposure. The specimens are examined after removal from the moisture-laden environment, and their tensile strength is directly compared against unexposed control specimens to quantify the extent of degradation. The standard is under the jurisdiction of ASTM Subcommittee D11.15 on Degradation Tests.
| 📐 Referenced Standard | 🎯 Role in D3137 |
|---|---|
| ASTM D412 | Standard test methods for tension testing of vulcanized rubber and thermoplastic elastomers. |
| ASTM D573 | Standard test method for rubber—deterioration in an air oven (related thermal aging context). |
| ASTM D3182 | Standard practice for mixing standard compounds and preparing standard vulcanized sheets. |
❓ Frequently Asked Questions
🔍 What is the fundamental purpose of ASTM D3137?
The standard is designed to measure the hydrolytic stability of rubber by determining its ability to withstand the environmental effects of high humidity. This is accomplished by examining the change in tensile strength of the material after removal from a moisture-laden environment over distilled water.
💡 What are the exact test temperature and exposure time requirements?
Specimens must be exposed to a temperature of 85 ± 1°C (185 ± 2°F) for a period of 96 ± 1 hour. After exposure, a specific conditioning period of 16 to 96 hours at 50 ± 5 % RH and 23 ± 2°C is mandatory before tensile properties can be measured.
⚡ How is hydrolytic degradation measured and evaluated in this standard?
Degradation is quantified by measuring the change in tensile strength. The tensile strength of specimens exposed to the humid environment is compared to that of unexposed control specimens, providing a direct and quantifiable measure of the material’s performance loss.
📌 Is this test method applicable to all types of rubber goods?
No. This test method is specifically intended for rubber materials cut from standard sheets prepared according to Practice D3182. The standard explicitly states that it is not applicable to coated fabrics and that its use for materials other than rubber has not been established.