HG/T 2708-1995 Determination of acid value in polyester polyols HG/T2708-1995 Standard download decompression password: www.bzxz.net

Chemical Industry Standard of the People's Republic of China
Determination of Acid Value in Polyester Polyols
1 Subject Content and Applicable Scope
This standard specifies the method for determining the acid value in polyester polyols by acid-base titration. This standard is applicable to polyester polyols prepared by polycondensation reaction of adipic acid and low molecular weight polyols. 2 Reference Standard
GB/T601 Preparation of Standard Solution for Titration Analysis (Volumetric Analysis) of Chemical Reagents 3 Definition
Acid value: the number of milligrams of potassium hydroxide required to neutralize the acidic substances in 1g of sample. 4 Principle
HG/T2708--95
The sample is dissolved in toluene-ethanol solution, and phenol anhydride is used as an indicator. It is directly titrated with potassium hydroxide ethanol standard titration solution. At the same time, a blank test is performed, and the acid value of the sample is calculated from the difference. 5 Reagents
5.1 Methyl extract (GB/T684)-ethanol (GB/T679) mixture, 2+1 (V/V. 5. 2 Potassium hydroxide ethanol standard titration solution, c(KOH)=0.1mo1/L, calibrated every two weeks. 5.2.1 Preparation: Referring to the method specified in GB/T601, weigh 7g potassium hydroxide (GB/T2306), dissolve it in 20mL water, and dilute it to 1000mL with ethanol (GB/T679). Leave it for one week and take the supernatant for use. 5.2.2 Calibration: Use the method specified in 4.1.2 of GB/T601 to calibrate 5:3 phenolic acid indicator solution, 10g/L ethanol solution. 6 Instruments
6.1 Conical flask with stopper, 100mL or 150mL
6.2 Microdroplet Fixed tube, 5mL.
6.3 Analytical balance, sensitivity 0.1mg.
7 Analysis steps
According to the provisions in Table 1, weigh an appropriate amount of sample (accurate to 0.2mg) into a conical flask, add 20~30mL of toluene ethanol mixture, shake the conical flask to dissolve the sample completely, and heat it if necessary. Add 10 drops of phenolic acid indicator solution, and titrate with potassium hydroxide ethanol standard titration solution until the reddish color remains unchanged for 30s. Perform a blank test at the same time. Approved by the Ministry of Chemical Industry of the People's Republic of China on May 5, 19958
Implemented on January 1, 1996
Acid value, mg KoH/
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8 Calculation and expression of analysis results
8.1 The acid value x is calculated according to formula (1):
where: X——acid value, mg KOH/g
HG / T 2708 —95
(V, - V,) + c × 56. 10
V-Amount of potassium hydroxide ethanol standard titration solution used in titration of sample, mL; Vi
Amount of potassium hydroxide ethanol standard titration solution used in blank test, mL; Concentration of potassium hydroxide ethanol standard titration solution, mol/L; Mass of a sample, more
Molar mass of potassium hydroxide, g/mol,
Sample weight. g
The measurement result is expressed as the arithmetic mean of two parallel measurements, and retains two significant figures, 8.2 Allowable difference
The difference between the two parallel measurement results shall not be greater than
Acid value, mg KOH/g
Test report
The test report shall include the following items
Indicate reference to this industry standard:
Specimen name, model, grade, batch number;, Sample delivery unit:
Results expressed in accordance with Article 8;
Test personnel:
Test date.
Allowance, mg KOH/g
Additional instructions:
HG / T 2708- 95
This standard was proposed by the Technical Supervision Department of the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Plastic Resin Products Branch of the National Plastic Standardization Technical Committee (TC15/SC4). This standard was drafted by Jiangsu Chemical Research Institute. The main drafter of this standard is Xu Miaoling,
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