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How to Test Polymer Water Absorption

ASTM International, originally the American Society for Testing and Materials, has developed a reputation around the world for collecting and distributing voluntary standards for a variety of materials testing. ASTM D570 is the most commonly used test for water absorption of polymers and some other plastics. It has two purposes: to give testers a rate for water absorption over time, and to express a sense as to what the specific effects of a humid environment or long-term exposure to water would be on the polymer under examination.

Things You'll Need

Oven
Analytical balance
Desiccator
Water
Soaking container
Drying sheet

Instructions

- 1
  Soak your polymer sample in water, inside a larger container, for a predetermined period of time. While the specific amount of time is not important, it is important to use the same period of time if you are comparing different polymers.
- 2
  Take the sample out of the water and weigh it on the analytical balance. Record your results.
- 3
  Preheat the oven to the appropriate temperature. This will vary depending on the polymer in question. For example, PA6 should be dried at 167 degrees Fahrenheit, while PE requires 185 degrees Fahrenheit. Drying time will vary as well: PE dries in about one-fourth the time as PA6.
- 4
  Place the dried samples into a desiccator to cool to room temperature. Then weigh them again and record the results.
- 5
  Subtract the sample's dry weight from its wet weight. Then divide that answer by the dry weight and multiply by 100. This will give you the polymer's percent water absorption.

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