ASTM D 618 Conditioning Plastics Testing

ASTM D 618 Standard Test Practice covers conditioning plastics for testing is crucial as their physical and electrical properties are significantly influenced by temperature and humidity. Standardizing these conditions ensures consistent and accurate results for reliable comparisons between different materials and laboratories.

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ASTM D 618 Conditioning Plastics Testing

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Precision-driven testing for dimensional accuracy and compliance

Overview
Scope, Applications, and Benefits
Test Process
Specifications
Instrumentation
Results and Deliverables

Overview

ASTM D618 describes the standard conditioning procedures for plastic materials prior to testing. Conditioning is used to achieve consistent results by stabilizing moisture and temperature.

Achieving full equilibrium may require a considerable amount of time, which can range from 20 to 100 days, depending on the material and its thickness. Conditioning is essential for general purchase specifications, product control tests, and material comparisons.

Scope, Applications, and Benefits

Scope

ASTM D618 applies to plastic materials prior to performing mechanical, physical, and electrical tests. It ensures that test specimens are properly conditioned in accordance with the relevant ASTM plastic test method to achieve consistent and reliable results.

Standardized Conditioning Procedures:

Procedure A: Standard laboratory atmosphere conditioning
Procedure B: Oven conditioning followed by desiccation
Procedure C: Water immersion conditioning
Procedure D: High humidity conditioning

The quantity and type of specimens must conform to the requirements specified in the applicable ASTM material test method.

Applications

Quality control testing of plastics
Preconditioning for mechanical property evaluation
Electrical property testing
Dimensional stability assessment
Moisture absorption studies
Research and development of polymer materials
Comparative material performance evaluation

Benefits

Ensures repeatable and standardized testing conditions
Controls moisture and temperature effects on plastics
Improves reliability of test data
Supports accurate purchase specifications
Reduces variability between laboratories
Enhances consistency in product evaluation
Provides uniform conditioning terminology

Test Process

Procedure A

Condition at 23°C, 50% RH for 40 h (≤7 mm) or 88 h (>7 mm).

Procedures B & C

B: 50°C for 48 h, then desiccator cooling. C: Water immersion at 50°C for 48 h, cool to 23°C before testing.

Procedure D

Condition at 23°C and 96% RH as specified.

Compliance

Maintain humidity per ASTM E104 and use required specimen type and quantity.

Technical Specifications

Parameter	Details
Applicable Materials	Plastic materials
Standard Laboratory Atmosphere	23°C ± 1°C, 50% ± specified RH
Oven Conditioning Temperature	50 ± 2°C
Water Conditioning Temperature	50 ± 1°C
High Humidity Condition	96 ± 1% RH at 23 ± 1°C
Specimen Thickness Criteria	≤7 mm or >7 mm determines conditioning duration
Condition Notation Format	Time/Temperature/Humidity or immersion medium
Output	Condition designation and pre-test conditioning record

Instrumentation Used for Testing

Environmental conditioning chamber
Circulating-air oven
Desiccator with anhydrous calcium chloride
Distilled water bath
Humidity control system
Thermometer and hygrometer
Specimen racks or mesh supports

Results and Deliverables

Conditioning designation (e.g., 48/50/water, 96/23/50)
Pre-test environmental conditioning record
Documented temperature and humidity conditions
Quality control documentation

Frequently Asked Questions

The conditioning process reduces the effects of the environment by equalizing the moisture content and temperature of the polymer. This ensures that the results of the tensile, flexural, and impact tests are accurate and representative of the true physical state of the material.

While applied in a similar manner, composites often need longer exposure times to achieve equilibrium because of their complex internal structures. Controlled cycles also prevent the absorption of moisture from artificially lowering the glass transition temperature (Tg) during testing.

The most generally specified conditioning environment is 23 ± 2°C and 50 ± 10% relative humidity. However, alternative temperature and humidity conditions may be required depending on the material type and applicable test method.

ASTM D618 is normally applicable to most thermoplastic and thermosetting plastics used in laboratory testing. However, specific product standards may override these requirements.

If the specimens are not conditioned properly, then the results of strength, stiffness, and dimensional stability could be affected by the variations in moisture content and temperature.