Polymethylene polyphenyl isocyanate - Determination of isocyanato content
1 Subject content and applicable scope
This standard specifies two methods for determining the isocyanato content in polymethylene polyphenyl isocyanate by potentiometric titration.
It is applicable to the determination of isocyanato content in polymethylene polyphenyl isocyanate for polyurethane foam.
2 Normative references
GB 601 Chemical reagent - Preparations of standard volumetric solutions
3 Method A
3.1 Principle
Isocyanate reacts with dibutylamine to produce urea, and excessive dibutylamine is subjected to potentiometric titration with hydrochloric acid standard solution to determine the isocyanato content.
3.2 Reagents
In the analytical method, analytically pure reagent and distilled water or water of equivalent purity shall be used.
3.2.1 Toluene (GB 684): dehydrated by 4A molecular sieve.
3.2.2 Isopropanol.
3.2.3 c[NHC(C4H9)2]＝2mol/L dibutylamine toluene solution: weigh 260g of dibutylamine in a 1,000mL volumetric flask, dissolve it with toluene dehydrated by 4A molecular sieve and dilute to the scale.
3.2.4 Hydrochloric acid standard solution: c(HCl)＝1mol/L, prepared and calibrated according to GB 601, 4.2.
3.3 Apparatus
1 Subject content and applicable scope
2 Normative references
3 Method A
4 Method B
5 Calculation and representation of results
6 Tolerance
7 Test report
8 Arbitration method
Additional explanation
