HG/T 2409-1992 Determination of isocyanate content in polyurethane prepolymers HG/T2409-1992 standard download decompression password: www.bzxz.net

Chemical Industry Standard of the People's Republic of China
HG/T2409-—92
Determination of the content of isocyanate groups in polyurethane prepolymers
Issued on October 22, 1992
Ministry of Chemical Industry of the People's Republic of China
Standards Network m.hui5icc Various standards industry information free download Not implemented on July 1, 1993
Chemical Industry Standard of the People's Republic of China
Determination of the content of isocyanate groups in polyurethane prepolymers
Subject content and scope of application
HG/T240992
This standard specifies the method for determining the content of isocyanate groups (NCO) in polyurethane prepolymers or intermediates. This standard is applicable to the determination of isocyanate content in polyurethane prepolymers or intermediates. The diisocyanates in the samples of this standard are toxic to a certain extent (such as the allowable concentration TLV of 2,4-toluene diisocyanate is 0.02ppm). To avoid inhalation of its vapor and direct skin contact, the analysis process needs to be carried out under good ventilation. 2 Definition
Isocyanate content: Isocyanate content in polyurethane prepolymers or intermediates generated by the reaction of polymerized polyols with excess diisocyanates.
3 Principle of the method
The isocyanate group in the polyurethane precursor or intermediate product reacts with excess di-n-butylamine in toluene. After the reaction is completed, the excess di-n-butylamine is titrated with a standard hydrochloric acid titration solution. The reaction is as follows: Reaction of isocyanate group with di-n-butylamine:
R-NCO+(C,H,)NH
Reaction of hydrochloric acid with di-n-butylamine:
(C,HNH+HC)
4 Reagents
RNHCON(C,H)2
+(C,H,),NH · HCI
This standard uses analytical grade reagents and distilled water or water of equivalent purity. 4.1 Toluene: anhydrous or dried over molecular sieve balls. 4.2 Isopropanol.
4.3 Di-n-butylamine anhydrous toluene solution: c((C,Hg)NH)=0.1 mol/L, take 16.6 mL (12.9 g) of di-n-butylamine, dissolve it in toluene and dilute to 1 L,
4.4 Standard hydrochloric acid titration solution: c(HC1)=0.1 mol/L, calibrate with bromophenol blue indicator. 4.5 Bromophenol blue indicator: 1g/L, dissolve 0.1g of acidic non-water-soluble bromophenol blue in 1.5mL c(NaOH)=0.1mol/L sodium hydroxide solution, and dilute to 100mL with distilled water 5 Instruments
5.1 Acid burette: 50mL
The Ministry of Chemical Industry of the People's Republic of China approved the standard on October 22, 1992 and implemented it on July 1, 1993
5.2 Pipette: 25mL,
5.3 Analytical balance: sensitivity 0.1mg.
6 Analysis steps
HG/T240992
Weigh about 1g of 5% (m/m) isocyanate sample, accurate to 0.0002g, and put it into a 250mL stoppered conical flask, not sticking to the neck of the bottle. Add 25mL of anhydrous toluene (4.1), cover the bottle with a stopper, and shake to completely dissolve the sample. You can also heat it on a heating plate to accelerate the dissolution. Use a pipette (5.2) to draw 25mL of anhydrous di-n-butylamine solution (4.3) into the conical flask. Put the stopper in the bottle and continue shaking for 15 minutes. Then add 100 mL of isopropanol (4.2), add 4 to 6 drops of bromophenol blue indicator (4.5), and titrate with standard hydrochloric acid solution (4.4) until the solution changes from blue to yellow. Perform a blank test at the same time according to the above determination method. Note: I) If the sample is insoluble, add 10 mL of anhydrous acetone to toluene. 7 Expression of analysis results
The isocyanate content is expressed as mass percentage and is calculated by the following formula: (V,-V,)c× 0. 0420×100Www.bzxZ.net
(V,-v,)-c×4.2
Wherein: V.
The volume of standard hydrochloric acid solution consumed in the blank test, mL; V. The volume of standard hydrochloric acid solution consumed by the sample, mL; - The actual concentration of the standard hydrochloric acid solution, mol/L; - The mass of the sample, g;
0.0420——The mass of isocyanate groups equivalent to 1.00mL of standard hydrochloric acid solution [c(HCI)=1.000mo1/L), expressed in grams.
The results should be expressed to two decimal places,
8 Allowable error
The difference between two results of parallel determination shall not exceed 0.11% (m/m) NCO, 9 Test report content
The standard referenced by this test method;
Determination results and expression methods;
Any abnormal phenomena noticed during the determination process; Determination date,
Standard according to regulations www.bego80.com Various standards industry business free download Additional notes
HG/T2409-92
This standard is proposed by the Science and Technology Department of the Ministry of Chemical Industry of the People's Republic of China. This standard is sponsored by the Synthetic Rubber Subcommittee of the National Rubber Standardization Technical Committee. This standard is drafted by the Sichuan Chemical Research Institute. The main drafters of this standard are Xiao Dingfang, Zuo Min, Qiao Yue and Gong Tao. This standard refers to and adopts the American Society for Testing and Materials ASTMD2572-87 "Standard Test Method for Isocyanate Groups in Amino Acid Materials or Prepolymers"
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Chemical Industry Standards
Determination of Isocyanate Group Content in Polyurethane Prepolymers
HG/T2409-92
Editor Chemical Industry Standards Department
(Institute of Standardization, Ministry of Chemical Industry)
Postal code: 100013
Printing Institute of Standardization, Ministry of Chemical Industry
Copyright reserved. No reproduction allowed
Format 880×12301/16 Number of words on a sheet 4000 First edition in March 1993 First printing in March 1993 Number of prints 1-500
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