1、 FORD LABORATORY TEST METHOD EU-AO 050-03 Date Action Revisions 2001 01 30 Revised Editorial no technical change A. Cockman 2000 04 17 Editorial no technical change A. Cockman 1993 10 18 Printed copies are uncontrolled Page 1 of 2 Copyright 2001, Ford Global Technologies, Inc. DETERMINATION OF NCO C
2、ONTENT IN ISOCYANATES Application This method is used to determine the NCO content in isocyanates used in the manufacture of polyurethane foam, by reaction of the NCO groups with dibutylamine or di-isobutylamine and titration with hydrochloric acid. Apparatus and Reagents Required Erlenmeyer Flask -
3、 250 mL Graduated Flask - 1000 mL Burette - 50 mL Hydrochloric Acid - 0.1 N Methanol - (A.R.) Bromophenol Blue - 0.04 % in ethanol Dibutylamine or Di-isobutylamine (A.R.) Dibutylamine or di-isobutylamine is refluxed over barium oxide as drying agent for 3 h and then distilled. Use a guard tube fille
4、d with sodium hydroxide and calcium oxide to avoid contact of the distillate with water vapour or carbon dioxide. Monochlorobenzene Monochlorobenzene must be redistilled. Discard the first azeotropic runnings. Distilled monochlorobenzene is water-free. Conditioning and Test Conditions All test value
5、s indicated herein are based on material conditioned in a controlled atmosphere of 23 +/- 2 C and 50 +/- 5 % relative humidity for not less than 24 h prior to testing and tested under the same conditions unless otherwise specified. FORD LABORATORY TEST METHOD EU-AO 050-03 Page 2 of 2 Copyright 2001,
6、 Ford Global Technologies, Inc. Procedure 1. Prepare a dibutylamine solution (0.1 N) by weighing 12.93 g freshly distilled dibutylamine or di-isobutylamine into a clean, dry beaker and making up to 1000 mL with monochlorobenzene. 2. Depending on the isocyanate content weigh 150 +/- 0.1 mg to 250 +/-
7、 0.1 mg of material under test into the Erlenmeyer flask, add 20 mL of the 0.1 N dibutylamine solution. If the isocyanate is not dissolved completely add a few mL of chlorobenzene. Allow to stand for 10 minutes. Note: Any precipitate is ignored. 3. Dilute with 100 mL methanol and add the 0.04 % brom
8、ophenol blue solution until a faint blue colour develops in the test solution. 4. Titrate the test solution with the 0.1 N hydrochloric acid. The colour changes from blue to colourless or very slight yellow. 5. Run a blank test using the relevant solutions. (20 mL dibutylamine solution 0.1 N) Evalua
9、tion Calculate and report the NCO content using the following formula: NCO (%) = (B-A) x f x 4.2 x 100 W Where: A = HCl (0.1 N) used for the test solution (in mL) B = HCl (0.1 N) used for the blank test (in mL) f = Factor of the HCl W = Sample weight in mg Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities.
