GB/T 12008.3-1989 English PDF (GBT12008.3-1989)

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GB/T 12008.3-1989: Palyether polyols--Determination of hydroxyl number
GB 12008.3-1989
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
Polyether polyols - Determination of hydroxyl number
ISSUED ON: DECEMBER 25, 1989
IMPLEMENTED ON: NOVEMBER 01, 1990
Issued by: State Bureau of Technical Supervision
Table of Contents
1 Scope ... 3 
2 Normative references ... 3 
3 Definition ... 3 
4 Principle ... 3 
5 Reagents ... 3 
6 Instruments ... 4 
7 Specimen ... 4 
8 Analytical procedures ... 4 
9 Calculation and expression of determination results ... 5 
10 Precision (95% confidence level) ... 6 
Appendix A Determination of base number (Supplementary) ... 7 
Additional information: ... 8 
Polyether polyols - Determination of hydroxyl number
1 Scope
This standard specifies the method for determining the hydroxyl number of
polyether polyols by the phthalic anhydride esterification method.
This standard applies to the determination of the hydroxyl number of polyether
polyols for polyurethane foams which are made by the ring-opening
polymerization of polyols, ethylene oxide and propylene oxide under the action
of a catalyst.
2 Normative references
GB 601 Chemical reagent - Preparations of standard volumetric solutions
GB 12008.5 Polyether polyols - Determination of acid number
3 Definition
Hydroxyl number: The number of milligrams of potassium hydroxide equivalent
to the hydroxyl content in each gram of specimen.
Alkali value: The number of milligrams of potassium hydroxide equivalent to the
alkaline substance in each gram of specimen.
4 Principle
Under reflux conditions of 115 °C, the hydroxyl group and phthalic anhydride
dissolved in pyridine undergo an esterification reaction; the excess phthalic
anhydride is titrated by a standard sodium hydroxide solution.
5 Reagents
In the analysis method, it shall use analytical reagents and distilled water or
water of corresponding purity.
5.1 Pyridine (GB 689).
5.2 Phthalic anhydride pyridine solution: Weigh 111 ~ 116 g of phthalic
anhydride into 700 mL of pyridine. Shake to dissolve it. Place it in a brown bottle
overnight before use. If the solution appears colored, it shall be discarded.
When performing blank titration according to the analysis steps in Chapter 8,
25 mL of this solution shall consume 45 ~ 50 mL of 1 mol/L sodium hydroxide
standard solution.
5.3 Phenolphthalein indicator solution: 1% pyridine solution.
5.4 Sodium hydroxide (GB 629) standard solution: c (NaOH) = 0.1 mol/L, c
(NaOH) = 1 mol/L, which is prepared and calibrated according to clause 2 of
Chapter 2 in GB 601.
5.5 Hydrochloric acid (GB 622) standard solution: c (HCl) = 0.1 mol/L, which is
prepared and calibrated according to clause 3 of Chapter 2 in GB 601.
6 Instruments
6.1 Esterification bottle: 250 mL, which has a ground-mouth air condenser, the
length of which is greater than 60 cm.
6.2 Oil bath: 115 ± 2 °C.
6.3 Burette: 50 mL, alkaline.
6.4 Pipette: 25 mL.
6.5 Dropper weighing bottle.
6.6 Conical flask: 250 mL.
6.7 Analytical balance: Sensitivity of 0.1 mg.
7 Specimen
If the moisture in the specimen exceeds 0.2%, it must be determined after
dehydration.
8 Analytical procedures
8.1 Weigh the specimen (calculated according to 561/estimated hydroxyl
number), accurate to 0.1 mg. Place it in an esterification bottle (do not let the
specimen expose to the bottleneck).
8.2 Use a pipette to take 25 mL of phthalic anhydride pyridine solution. Add it
to the esterification bottle which contains the weighed sample. Shake the bottle