However, in the late 1970s, ASTM reorganized its numbering system. The current active standard is . If you find a document labeled "ASTM D123," it is likely an obsolete version (pre-1979). Modern laboratories, ISO standards, and material data sheets reference ASTM D1238 .
This article serves as a comprehensive resource. We will explain what ASTM D123 (now officially ASTM D1238) is, why the PDF is essential for your lab, how to legally obtain it, and how to interpret the data it produces. By the end, you will understand why this 70+ year-old standard remains the lifeblood of the plastics industry. astm d123 pdf