ASTM D4877 Determination of APHA Color in Isocyanates

Scope:

ASTM D4877 test technique can be used to characterize isocyanates used in polyurethane goods for research or quality control. The findings of this test technique for toluene diisocyanate can be used to determine reactivity or efficiency in polyurethane systems. It can only be used with materials whose color-producing bodies have light-absorption properties, like the platinum cobalt color standards. Toluene diisocyanate and pure or modified monomeric methylene diisocyanate are suitable isocyanates (phenyl isocyanate) for the determination.

Procedure:

In the ASTM D4877 method, one of a matched pair of 100-mL tall-form Nessler tubes is filled to the mark, and then a second tube is filled from the matched set to the mark with the standard that appears to be the closest match to the sample’s color. The samples’ colors are compared by looking vertically through the tubes against a white background. 

Specimen Size:

The substance’s color to be evaluated is compared to a set of platinum cobalt color standards, measured in milligrams of platinum per milliliter of standard solution.