In crude or modified isocyanates, ASTM D7252-17 measures the proportion by weight of monomeric isomers and total Monomer. The values expressed in SI units should be considered standard. This standard does not include any other units of measurement.

In crude or modified isocyanates, ASTM D7252-17 measures the proportion by weight of monomeric isomers and total Monomer. The values expressed in SI units should be considered standard. This standard does not include any other units of measurement.
Scope:
The ASTM D7252-17 test method is suitable for methylene di(the-nyl isocyanate) (MDI) and polymeric (methylene phenyl isocyanate-nate) (PMDI). This test method is used to characterize isocyanates used in polyurethane goods and for research or quality control.
Procedure
In ASTM D7252-17, firstly, to make a mixture of methyl urethanes, the material is treated (derivatized) with methanol. Secondly, normal-phase high-performance liquid chromatography is used to separate the urethanes combination (HPLC). Then, isomers are isolated and derivatized, and lastly, an internal standard is used to quantify the results.
Specimen size
Pump should be of Flow = 1.5 mL/min, Eluent A (hexane) = 90 %,Eluent B (1:1 by volume ethanol:methanol) = 10 %. Detector should have Wavelength = 235 nm, Output Range = 2.000, Injection volume = 2 μL and Column Temperature = 30°C
Data
The percent monomer is calculated in the sample by Monomer, % = Sum of all isomers, %.
Result
The weight percentage of each isomer and Monomer is calculated and reported to the nearest 0.1 percent.
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