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1.1 This test method determines the ratio of the infrared absorbance of uretidinedione (dimer) in methylene-4,4’- di(phenylisocyanate) to an infrared absorbance at a reference wavelength within the same material. It is applicable to monomeric methylene-di(phenylisocyanate), or “Pure MDI,” containing 95 % or greater methylene-4,4’-di(phenylisocyanate).

1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

5.1 This test method can be used for research or for quality control to determine the dimer ratio of Pure MDI.

5.2 Uretidinedione begins forming in Pure MDI with the rate of formation increasing with increasing temperature. High levels can affect the appearance of Pure MDI and the quality of products made from it.