Plastics are highly sensitive to their surrounding environment. Small fluctuations in room temperature or relative humidity can drastically alter a polymer's tensile strength, impact resistance, and electrical insulation properties.
Critical for outdoor consumer goods, automotive under-hood components, and marine applications. Summary of Common Procedures Temperature Relative Humidity (RH) Procedure A ≥40is greater than or equal to 40 Procedure B Desiccated (Dry) ≥48is greater than or equal to 48 Procedure C ≥96is greater than or equal to 96 Procedure D Water Immersion Why Is This Standard Critical for Testing? 1. Eliminating Material Memory and Stress
A combination of dry and humid environments, often used for accelerated aging simulations. 3. Equilibrium Time
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While the core principles of conditioning remain similar, the -21 version may contain updated: astm d618-21 pdf
The most common routine requires specimens to condition for a minimum of 40 hours at 23 ± 2°C (73.4 ± 3.6°F) and 50 ± 10% relative humidity. For materials sensitive to moisture, the humidity tolerance narrows to ± 5%.
ASTM International (formerly known as the American Society for Testing and Materials)
Explain how to set up an environmental chamber for these standards. D618 Plastic Conditioning | PDF | Humidity - Scribd
40 hours at 23°C and 50% humidity. This is the "default" for most molded plastics under 7mm thick. 23°C/75% RH for tropical simulations)
Without proper conditioning (often called "pre-conditioning"), tests like tensile strength, flexural modulus, or dielectric strength can produce wildly different results, making quality control impossible. Key Procedures in ASTM D618
: If a specific material specification exists (e.g., under ASTM D4000 ), that specification's requirements take precedence over D618. Accessing the Full Document
Heating to a specific temperature (e.g., 50°C or 105°C) for a set duration, then cooling in a desiccator.
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Yes. Section 6 allows for alternative conditions (e.g., 23°C/75% RH for tropical simulations), but you must explicitly note the deviation from the standard atmosphere.
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The standard emphasizes that conditioning is not always about reaching absolute equilibrium, which can take weeks, but about achieving a reproducible state in a practical amount of time, sometimes lasting over 100 days for thick samples. When to Use ASTM D618-21 (PDF)
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The material specification takes precedence over this practice if one exists. That means you should always check the specific material specification for your plastic before conditioning, as it may modify some procedures defined in ASTM D618-21. Table 1 in Classification D4000 lists the ASTM material specifications that currently exist.