Determination of isocyanate (NCO) content in adhesives | Autotitrator COM-A19 - JM Science
HIRANUMA APPLICATION DATA Automatic Titrator Data No. M9 Apr. 19, 2018
Resins, Oils and Fats, Rubber, Adhesives, Paints Determination of isocyanate (NCO) content in adhesives

1. Abstract

Synthetic adhesives like hydrophilic macromolecule –Isocyanate type wood adhesives are consisted of base compound and cross-linker; the principal components of base compound are macromolecule aqueous solution or aqueous dispersing element, or those combination. The principal components of cross-linker is isocyanate compounds. The measurement procedure of isocyanate (NCO) content described in this report is standardized by JIS K 6806. NCO content is determined by the neutralization titration which excess di-n-butylamine is titrated with hydrochloric acid standard solution after sample and di-n-butylamine are mixed and reacted. A measurement example of potentiometric titration for NCO determination is introduced in this report.

2. Configuration of instruments and reagents

(1) Configuration    
  Main unit : Hiranuma Automatic Titrator COM series
  Electrode : Glass – Reference electrode GR-522BZ
  Option : Buret tip (Tube Type)
(2) Reagents    
  Titrant : 0.5 mol/L Hydrochloric acid standard solution
  Solvent : 2-propanol (Isopropyl alcohol)
  Additive : Di-n-butylamine – toluene solution
Dissolve 130 g of di-n-butylamine in dehydrated toluene.

3. Measurement procedure

(1) Take about 2 g of the sample into Erlenmeyer flask and accurately weigh it.
(2) Dispense 25 mL of di-n-butylamine – toluene solution with volumetric pipette.
(3) Add stirring bar and close it with a stopper. Gently stir the solution for 15 min with stirrer.
(4) Add 150 mL of 2-propanol.
(5) Immerse the electrode and titrate with 0.5 mol/L hydrochloric acid standard solution.
(6) Measure the blank value by operation of (2) ~ (5) without sample.

4. Measurement conditions and results

Examples of titration conditions

Measurement of blank

Cndt No. 1
Method Autot
Buret No. 1
Amp No. 1
D. Unit pH
S-Timer 5 sec
C.P. mL 45 mL
T Timer 0 sec
D.P. mL 0 mL
End Sens 1000
Over mL 0.3 mL
Max.Vol. 60 mL
ConstantNo. 1
Size 0 g
Blank 0 mL
Molarity 0.5 mol/L
Factor 1.005
K 0
L 0
Unit mL
Formula D
Digits 3
Auto In Pram.
Non
Mode No. 4
Pre Int 0 sec
Del K 9
Del Sens 0 mV
Int Time 3 sec
Int Sens 3 mV
Brt Speed 2
Pulse 40

 

Measurement of sample

Cndt No. 2
Method Auto
Buret No. 1
Amp No. 1
D. Unit pH
S-Timer 10 sec
C.P. mL 27 mL
T Timer 10 sec
D.P. mL 0 mL
End Sens 1000
Over mL 0.3 mL
Max.Vol. 60 mL
ConstantNo. 2
Size 2.0412 g
Blank 50.196 mL
Molarity 0.5 mol/L
Factor 1.005
K 42.02
L 0
Unit %
Formula (B-D)*K*F*M/(S*10)
Digits 4
Auto In Pram.
Non
Mode No. 4
Pre Int 0 sec
Del K 9
Del Sens 0 mV
Int Time 3 sec
Int Sens 3 mV
Brt Speed 2
Pulse 40

 

Measurement results

  Number of
Measurements
Size
(g)
Titrant
volume (mL)
NCO content
(%)
Statistical calculation
results
Blank 1 50.178 Avg.
(Blank)
50.196 mL
2 50.214
             
Sample 1 2.0412 32.105 18.714 Avg. 18.74 %
2 2.0429 32.035 18.771 SD 0.0287 %
3 2.0473 32.017 18.749 CV 0.15 %

 Examples of titration curves

 Measurement of blank Measurement of sample

 

5. Note

(1) Dehydrated toluene (less than 50 ppm water content) is used as a solvent to dissolve sample. Please note that the water in solvent causes measurement error because it reacts with isocyanate group.
(2) Electrode which can be directly inserted into Erlenmeyer flask is preferred for this titration.

 

Keywords: Isocyanates, NCO, Neutralization titration, JIS K 6806, JIS K 1603, JIS K 7301

 

*Some measurement would not be possible depending on optional configuration of system.

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