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Chemical Industry Standard of the People's Republic of China
HG / T 2501 -- 93
Determination of pH value of phenolic resin
Published on September 8, 1993
Ministry of Chemical Industry of the People's Republic of China
Implementation on July 1, 1994
Chemical Industry Standard of the People's Republic of China
Determination of H value of phenolic resin
HG / T 2501 -- 93
ISO 8975—89
This standard is equivalent to the international standard ISO8975—89 "Determination of pH value of plastic phenolic resin". 1 Subject content and scope of application
This standard specifies the method for determining the pH value of liquid phenolic resin during manufacture or sale. This standard is applicable to bulk phenolic resin: solid phenolic resin shall be carried out in accordance with Appendix A, and liquid resin with viscosity greater than 2Pa·s may also use Appendix A.
2 Principle
The pH value is determined by the potential difference between the glass electrode and the reference electrode in a solution. 3 Reagents
3.1 Potassium hydrogen phthalate standard solution
The solution with a concentration c(KCOOC,H,COOH) of 0.05mol/L has a pH value of 4.00 at 23C. Dissolve 10.21g of potassium hydrogen phthalate that has been heated to dryness at 100-130C for 2h in water and dilute to 1000mL. The solution should be stored in a glass container and away from any trace of acid or alkali. Add a little thymol crystal to allow the solution to stand for a longer time. Slightly turbid solution indicates microbial contamination, thymol is ineffective, and this solution should be discarded. 3.2 Hydrogen phosphate buffer solution
A solution containing about 0.025 mol potassium dihydrogen phosphate (KH2PO4) and 0.025 mol sodium dihydrogen phosphate (NazHPO4) per liter, with a pH value of 6.88 at 23 pm.
Dissolve 3.39 g potassium dihydrogen phosphate and 3.53 g sodium dihydrogen phosphate, which had been heated and dried at 110-130°C for 2 hours, in water and dilute to 1000 mL. Add a little thymol product to allow the solution to stand for a longer time. 3.3 Sodium tetraborate (borax) standard solution
A solution with a concentration of 0.01 mol/L (NazB,O,-10H2O), with a pH value of 9.22 at 23 pm. Dissolve 3.80g of sodium tetraborate + hydrate in water and dilute to 1000 mL.4 Instruments
4.1 pH meter, accurate to 0.1 pH unit.
4.2 Electrodes
4.2.1 Measuring electrode: glass electrode.
4.2.2 Reference electrode: calomel electrode,
4.2.3 Maintenance of electrodes: For various types of electrodes, the maintenance methods specified in the manufacturer's instructions must be followed and the electrodes must be stored under correct conditions. In special cases. The glass electrode should be cleaned regularly. When not in use for a long time, the electrode can be stored in a cool and dry place. When activating the electrode, soak the glass electrode in acidic distilled water (pH 4-5) for several hours, and soak the calomel electrode in saturated potassium chloride solution. Before each measurement, the two electrodes should be washed with water. They should be immersed in water for at least 2 minutes before measuring. Approved by the Ministry of Chemical Industry of the People's Republic of China on September 8, 1993 and implemented on July 1, 1994. 5 Test procedure 5. 1 Test temperature The test is carried out at 23 ± 0.5 °C. 5.2 Calibration of pH meter and electrode group Calibrate according to the manufacturer's instructions.
HG/T 2501—93
For calibration, use two standard solutions or buffer solutions (Chapter 3), whose pH value range should include the predetermined value to be measured. 5.2.1 Adjustment of the instrument
Rinse the two electrodes with water, gently wipe the electrode tops (e.g. with filter paper), remove the remaining water, and rinse the two electrodes with a standard solution or buffer solution in the way of rinsing the outside of the two electrode rods. Pour a sufficient amount of the standard solution or buffer solution into a clean and dry measuring pan container, and immerse the two electrodes in this solution. Set the reading of the pH meter to the pH value of the standard solution or buffer solution, and consider the temperature of the solution. Take out the electrodes and discard the standard solution or buffer solution in the measuring container. 5.2.2 Verification of instrument accuracy
As described in 5.2.1, wash the two electrodes with water first and then with the second standard solution or buffer solution. Wash the measuring container with water (or use a clean and dry container), and then rinse with the second standard solution or buffer solution. Pour enough solution into the container, immerse the two electrodes in the solution, record the reading of the pH meter, do not change the instrument settings, especially do not touch the temperature calibration knob or pH value positioning knob. If the reading is within the allowable pH value difference (± 0.1 pH unit) of the standard solution or buffer solution after considering the temperature factor, the instrument calibration is complete and can be used. If not, find out the cause (such as operating error, unqualified electrode, incorrect temperature calibration) and correct it. 5.3 Determination
5.3.1 Preparation of sample
Keep the resin temperature at 23 ± 0.5°C. Prepare 50% (m/m) resin aqueous solution. If phase separation occurs, wait until a sufficient volume of water phase can be separated in the dropping funnel for measurement, then transfer the water phase to a graduated beaker for measurement. 5.3.2pH Determination of pH value
After the instrument has been calibrated, clean the electrode (4.2) and the measuring container with water and then with the sample according to the method described in 5.2.1 and 5.2.2, stir the sample, pour a sufficient volume of sample into the measuring container (or another clean and dry container), immerse the electrode in the sample, wait for the pH meter reading to stabilize, record the reading, and repeat the above operation with a new sample. If the new reading of the pH meter is different from the previous reading or differs by only 0.2 pH units, the test is completed (unless otherwise specified in the special standard).
If this is not the case, use a new sample to perform a third sampling operation and comprehensively check the cause of the error. If the third measurement still cannot obtain a definite result, all operations including calibration should be repeated. In order to prevent the pH value of the solution from changing over time, especially when it comes into contact with carbon dioxide in the air, it can be carried out under appropriate conditions (such as purging with nitrogen flow).
6 Expression of results www.bzxz.net
Calculate the average value of the two measured values according to .5.3.2 and round it to 0.1 pH unit. 7 Test report
The test report should include the following contents:
Indicate reference to this industry standard;
HG /T 2501-93
b. Complete identification of the resin being tested:
Test results, calculated in accordance with the provisions of Chapter 6. If the test temperature is not 23±0.5℃, the test temperature should also be indicated; d.
Test period.
A1 Scope
HG/T 2501—93
Appendix A
Determination of pH value of solid phenolic resin
(reference)
This appendix describes the method for determining the pH value of solid phenolic resin during manufacture or sale. A2 Principle
Use a mixed solvent that has been pre-neutralized to a pH of 7 to prepare an organic-aqueous solution. Measure the pH value of the solution with a pH meter. A3 Reagents
In addition to the reagents specified in Chapter 3, add: A 3.1 Hydrochloric acid solution, concentration c (HCl) 0.01 mol / L A 3.2 Sodium hydroxide solution, concentration c (NaOH) about 0.01 mol / L. A3.3 Mixed solvent, its composition is water: 20±1g, methanol: 40±1g, acetone: 40±1g. Note: If the solid phenolic resin is not soluble in the above mixed solvent. A mixture of water and toluene or water and xylene can be used. A4 Instruments
In addition to the instruments specified in Chapter 4, add: A4.1 Electromagnetic stirrer.
A4.2 Balance, sensitivity 1g.
A 5 Test procedure
A5.1 Calibration of pH meter and electrode assembly
Use two standard solutions or buffer solutions (3.1 and 3.2).A 5. 2 Neutralization of mixed solvent
In a 250mL beaker, weigh 80±1g of mixed solvent (A3.3) using a balance (A4.2), stir with an electromagnetic stirrer (A·4.1), and keep the temperature of the mixed solvent at 23±0.5℃. Place the two electrodes in a beaker. If necessary, adjust the pH value of the mixed solvent to 7.0±0.1 with sodium hydroxide solution (A3.2) or hydrochloric acid solution (A3.I). A5.3 Determination
A5.3.1 Preparation of sample
Use a balance (A4.2) to weigh 20±1 of finely ground solid resin and place it in a beaker containing the neutral mixed solvent prepared according to A5.2. Stir with an electromagnetic stirrer (A4.1) until the resin is completely dissolved and keep the solution temperature at 23±0.5℃A5.3.2 Determination of pH value
Carry out the determination as described in 5.3.2, prepare the sample according to A5.3.1, A6 Expression of results
see Chapter 6,
A7 Test report
see Chapter 7.
People's Republic of China
Chemical Industry Standard
Determination of H value of phenolic resin
HG/T 2501—93
Editorial Department of Chemical Industry Standard
(Institute of Standardization, Ministry of Chemical Industry)
Postal Code: 100013
Printing Institute of Standardization, Ministry of Chemical Industry
Copyright reserved. No reproduction allowed
Format 880×1230/15 Sheet % Number of words 10000 First edition in May 1994
First printing in June 1994
Print run 1—300
Cost 2.40 Yuan
HG/T 2501 —93
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