ASTM D4616-95 (R2018) PDF Download

ASTM D4616-95 (R2018) is a standard test method that provides instructions for conducting microscopic analysis using reflected light to identify and determine the amount and size of mesophase in a pitch. Mesophase refers to the heat-treated coal tar and petroleum pitch that forms spheroids, which may be partially soluble in quinoline and cannot be estimated using the quinoline insoluble test (Test Method D2318).

This test method specifies that mesophase initially forms as spheroids and may coalesce into various asymmetrical shapes. The smallest mesophase particle that can be reliably detected at 400× or 500× magnification is 4 µm in diameter. Any mesophase particles smaller than 4 µm should be disregarded unless they are of specific interest. In such cases, higher magnifications ranging from 1000× to 1800× should be used, and the results should be appropriately identified.

It is important to note that this test method is primarily designed for determining minor levels of mesophase, specifically those equal to or greater than 20% mesophase. The standard outlines laboratory procedures for preparing granular and melted samples for microscopic analysis.