ASTM D4661 Determination of Total Chlorine in Isocyanates

Introduction

ASTM D4661 test method provides information about polyurethane raw materials by measuring the chlorine content of aromatic isocyanates. The amount of o-dichlorobenzene and other ringed chlorine products is determined by calculating the difference between the total chlorine content and the hydrolyzable chlorine content. Measure the final results in SI units.

Scope

The ASTM D4661 test method is essential in determining the chlorine content of isocyanates through titration. This test method is necessary 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

To begin with, ensure the ignition vessel, oxygen lines, and fittings are free of oils and grease, as this minimal quantity can ignite, leading to dangerous explosions. Take a sample of 0.9 g for which an accuracy of measurement of 60.0005 g has been recorded; add this to the combustion capsule. Mount on electrodes with a 100-mm iron-nickel fuse wire while placing the capsule on loop electrodes. Add about 5 ml of Na₂CO₃ solution to the ignition vessel and wet its interior wall using a rubber policeman. Place the head of the ignition vessel in the cylinder using its cap. Close the outlet valve and slowly add oxygen to a pressure of 20 to 25 atmospheres, checking for leaks by reading the pressure gauge.

Once sealed, immerse the ignition vessel in a cooling water bath and attach the ignition unit. Ignite the vessel; the red indicator light flashes on and off to indicate that it has successfully ignited. As soon as the vessel ignites, allow it to cool for at least 10 minutes before slowly releasing its pressure. Open the vessel, allowing an observation of any unburned sample or soot indicating incomplete combustion. Finally, clean the ignition vessel with water, acidify the washings, and titrate its analysis solution.

Alternative methods

ASTM D4661 chlorine determination in isocyanates can be done using the following methods.

Specimen size

The sample size should be as per the requirements, usually 0.9 grams.

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.

Result

The total chlorine content in the isocyanate sample is determined through titration with silver nitrate (AgNO₃)

Conclusion

ASTM D4661 is a test method providing a reliable and accurate measure of chlorine content in isocyanates. Thus, it is critical to determine the quality and suitability of isocyanates for use in producing polyurethane-based materials. It quantitatively determines total chlorine through titration using silver nitrate, ensuring the performance and consistency of isocyanate-based materials in various applications.

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