Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D5155-19 – Standard Test Method Technical Guide
🏷️ Scope and Application
These test methods (D5155-19) are designed to measure the isocyanate content of aromatic isocyanates used as polyurethane raw materials. They cover three distinct test methods: Test Method A for refined toluene diisocyanate (TDI), Test Method B for crude or modified isocyanates using heat, and Test Method C for crude or modified isocyanates without heat. The standard specifies SI units for all measurements. Users are responsible for establishing appropriate safety protocols.
Test Method A is suitable for refined TDI isomers, including 2,4- and 2,6-diisocyanate, and other isocyanates of adequate reactivity. Test Method B applies to crude or modified isocyanates from TDI, MDI, and polymeric MDI, utilizing a heated toluene-dibutylamine system. Test Method C uses an unheated trichlorobenzene-toluene-dibutylamine system for similar materials and is equivalent to ISO 14896 Method B.
| 🟦 Method | 📏 Sample Type | 📐 Solvent | 🎯 Temperature |
|---|---|---|---|
| Test Method A | Refined TDI (and other suitable isocyanates) | Toluene | Unheated |
| Test Method B | Crude/Modified isocyanates (TDI, MDI, polymeric MDI) | Toluene | Heated |
| Test Method C | Crude/Modified isocyanates (TDI, MDI, polymeric MDI) | Trichlorobenzene-Toluene | Unheated |
⚙️ Test Methodology and Key Properties
Each method involves reacting the isocyanate sample with an excess of dibutylamine to form a urea derivative. The unreacted amine is then titrated to determine the amine equivalent, from which the isocyanate content is calculated. Critical technical terms are defined below.
| 🟦 Term | 📏 Definition |
|---|---|
| Amine Equivalent | Weight of sample (g) that combines with 1.0 g equivalent of dibutylamine. |
| Assay | Percent by weight of TDI in the sample. |
| Isocyanate (NCO) Content | Percent by weight of NCO groups present. |
These properties are essential for ensuring correct stoichiometry in polyurethane formulations and are determined using the specified test methods.
⚠️ Safety Warning: Isocyanates and solvents used are hazardous. Follow all safety data sheets and regulatory requirements. This standard does not cover all safety aspects.
💡 Method Selection Tip: Choose Test Method A for refined TDI, Test Method B for heated analysis of crude isocyanates, and Test Method C for unheated analysis. Method C is aligned with ISO 14896 for international use.
❓ Frequently Asked Questions
🔍 What is the primary use of these test methods?
They are used to quantify the isocyanate content in aromatic isocyanates, critical for quality control in polyurethane manufacturing.
💡 How do the test methods differ?
Method A is for refined TDI using unheated toluene-dibutylamine. Method B uses heat for crude isocyanates, while Method C uses an unheated trichlorobenzene-toluene system for similar samples.
⚡ What does amine equivalent represent?
Amine equivalent is the sample weight that reacts with one equivalent of dibutylamine, used to calculate isocyanate content.
📌 Is this standard recognized internationally?
Yes, Test Method C is equivalent to ISO 14896 Method B, ensuring global consistency.