Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D3855-84 – Standard Test Method Technical Guide
🧪 Scope and Significance of the Test Method
ASTM D3855-84 (Reapproved 2010) provides a standardized laboratory procedure for evaluating the resistance of bare rubber threads to deterioration when exposed to a standard washing solution, followed by room-temperature drying and accelerated heat aging. As noted in Section 1.1, this test method is strictly comparative. It is designed to assess relative performance rather than to predict absolute service life, as the actual durability of threads in garments depends on numerous factors beyond the scope of this test. The values stated in SI units are regarded as the standard.
Section 4.1 highlights a key challenge addressed by this method: rubber threads and garments are subjected to washing treatments with widely varying compositions and temperatures. Because the exact formulation of commercial detergents is often proprietary and variable, this test method establishes a fixed, reproducible benchmark for evaluating deterioration under a known chemical stress.
⚙️ Apparatus and Standard Washing Solution
The test requires specific apparatus to ensure consistent conditions. A Constant-Rate-of-Extension (CRE) tensile testing machine with a load capacity of 0.1 to 20 N (10 to 2000 gf), equipped with hooks, is essential for measuring physical properties. For holding the specimens at their extended state, a form made of Masonite, stainless steel, or glass is required, measuring 100 by 300 by 3 mm (4 by 12 by 1/8 in.) with a cut-out center section and rounded outside edges (Section 5.2).
⚠️ Important Note: The standard text provided for this summary is truncated. Section 6 details the complete formula for the Standard Washing Solution. Users must consult the full, official ASTM D3855 document for the exact chemical constituents and their concentrations to be dissolved in 1 L of distilled water. Using an incorrect or approximate solution formulation will invalidate the test results.
A constant-temperature water bath and a thermometer (0 to 100°C, graduated in 0.2°C divisions) are needed for precise control of the washing solution temperature. Heat aging is conducted in a circulating hot-air oven conforming to Specification E145, capable of maintaining a temperature of 125 ± 2°C. Additionally, 1500 cm³ beakers are specified for preparing and holding the washing solution.
| 🟦 Apparatus | 📏 Specification | 🎯 Tolerance / Range |
|---|---|---|
| Tensile Testing Machine | CRE Type with Hooks | 0.1 to 20 N (10 to 2000 gf) |
| Specimen Form | Masonite, Steel, or Glass | 100 x 300 x 3 mm |
| Air-Oven | Circulating, per E145 | 125 ± 2°C |
| Thermometer | Partial Immersion | 0 to 100°C, 0.2°C divisions |
| Beaker | Laboratory Glassware | 1500 cm³ |
📊 Key Measured Properties and Procedure Summary
According to the Summary of Test Method (Section 3), the initial properties of the thread are determined in accordance with Test Methods D2433. The same test specimens, extended to 100% elongation, are then subjected to a single cycle: immersion in the standard washing solution, drying at room temperature, and heat aging in the oven. After aging, the physical properties are re-measured to determine deterioration.
Section 3.2 specifies the physical properties that can be evaluated. While any property from Sections 18 to 37 of D2433 is acceptable, the standard specifically identifies the Schwartz value (Section 25) or stress retention at 100% elongation (Section 35) as the most suitable measures of deterioration for this test. A critical note (Note 1) advises that when using the Schwartz value, the maximum massaging extension should be restricted to 300% to prevent excessive breakage after aging. Conversely, when testing stress retention, the thread must be massaged to 300% extension for six cycles immediately prior to the stress measurement.
💡 Pro Tip: Consistently follow the pre-conditioning massage protocols. The distinction between restricting the massage extension (for Schwartz value) and requiring six cycles to 300% (for stress retention) is critical for avoiding skewed results or specimen damage.
| 📐 Parameter | ⚡ Specified Value / Property | 📝 Notes |
|---|---|---|
| Specimen Extension | 100% Elongation | Maintained during washing and aging cycle |
| Aging Temperature | 125 °C | Tolerance ± 2°C |
| Primary Measured Properties | Schwartz Value, Stress Retention | Defined in Test Methods D2433 |
| Washing Solution Volume | 1 L Distilled Water + Ingredients | Refer to Section 6.1.1 of the full standard |
❓ Frequently Asked Questions
🔍 What is the primary purpose of ASTM D3855?
The standard covers the measurement of the relative deterioration resistance of bare rubber threads subjected to a standard washing solution, room temperature drying, and air-oven aging. It is designed for comparative evaluation, not absolute service life prediction (Section 1.1 and 1.2).
💡 What specific physical properties should be measured?
While several properties from Test Methods D2433 can be used, the standard recommends the Schwartz value (Section 25 of D2433) or stress retention at 100% elongation (Section 35 of D2433) as the most suitable indicators of deterioration due to washing (Section 3.2).
⚡ What are the specified dimensions of the specimen form?
The form used to hold the thread loops at 100% elongation must be 100 by 300 by 3 mm (4 by 12 by 1/8 in.), with the center section cut out and the outside edges rounded (Section 5.2.1).
📌 What is the required temperature for the aging oven?
The circulating hot-air oven must conform to Specification E145 and be capable of maintaining a temperature of 125 ± 2°C throughout the aging period (Section 5.5).