In the world of plastics and materials testing, consistency is the enemy of error. If you have ever tested a plastic sample on a Monday morning and gotten different results than on a Friday afternoon, you have witnessed the effects of uncontrolled temperature and humidity. This is where ASTM D618-21 becomes the most important standard you are probably ignoring.
The "21" denotes the year of last approval—2021. While the standard is reaffirmed periodically, the 2021 version currently contains the most up-to-date requirements for humidity control, temperature tolerances, and testing timelines. Plastics are hygroscopic or hydrophobic to varying degrees. Nylon absorbs moisture from the air, becoming more flexible and impact-resistant. Polycarbonate, on the other hand, can become brittle if too dry. Without a standard like ASTM D618, one laboratory might test "dry-as-molded" nylon while another tests nylon conditioned at 50% RH. The results would disagree by 50% or more. astm d618-21 pdf
A: The 2021 revision tightens humidity tolerances, clarifies test time limits, and updates referenced standards. In the world of plastics and materials testing,
