ASTM D4661 Determination of Total Chlorine in Isocyanates

Scope:

The ASTM D4661 test method is important in determining the chlorine content of isocyanates with the help of titration. This test method is important to get accurate readings at different sample concentrations. It defines a standard to control the quality and application of these isocyanates. It characterizes the isocyanates found in polyurethane products and is applicable for research purposes. It determines the chlorine content by destroying the organic matter of the sample. It provides information about the performance of isocyanates in polyurethane systems which helps specify their reliability and application.  

Procedure:

The apparatus used in ASTM D4661 testing consists of a weighing bottle and balance, oxygen ignition vessel, fuse wire, potentiometric titrator, silver electrodes, bubble counter, and a microburst. The vessels are cleaned to remove oil and grease. The sample is weighed, and an iron-nickel fuse wire is attached to the electrodes. The interior surface of the vessel is filled with a sodium carbonate solution and oxygen. The sample is heated in a pressurized ignition vessel for test A and at atmospheric pressure in an oxygen flask for test B.

Specimen size:

The sample size should be taken as per the requirements.

Data:

In ASTM D4661 testing, the total chlorine can be calculated as follows:

Total chlorine, % ꞊ 3.55(A – B) N/W
Where: A = AgNO₃ solution required for titration of the sample, mL.
B = AgNO₃ solution required for titration of the blank, mL.
N = normality of the AgNO₃ solution,
W = sample used, g, and 3.55 = constant combining the milligram atomic weight of chlorine.

Conclusion:

The ASTM D4661 test method is important in determining the chlorine content of isocyanates with the help of titration.