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Test method of phenolic resin for ablative materials - Test of free phenols
1 Subject content and applicable scope
This standard specifies the method of determining free phenols in phenolic resin by bromine content method.
It is applicable to the determination of free phenols in phenolic resin for ablative materials. It may be used as a reference for other phenolic resins.
2 Normative references
GB 601 Chemical reagent - Preparations of standard volumetric solutions
GJB 1059.1 Test method of phenolic resin for ablative materials - Test of solid content
3 Summary method
The free phenol is separated from the resin matrix by steam distillation, and reacts with known excessive bromine. The percentage of free phenol is calculated by back titration of the excessive bromine with sodium thiosulfate solution.
4 Reagents
4.1 Hydrochloric acid: complying with GB 622, chemically pure.
4.2 Bromine solution: c (1/5kBrO3) = 0.1mol/l, weigh 3g of potassium bromate and 25g of potassium bromide, dissolve them in 1,000ml of water, and shake well.
4.3 Potassium iodide solution: 100g/l, weigh 10g of potassium iodide (chemically pure), dissolve it in 100ml of water, and shake well.
4.4 Phosphoric acid solution: 15%(v/v), inject 13ml of phosphoric acid into 87ml of water and shake well.
4.5 Sodium hydroxide solution: 100g/l, weigh 100g of sodium hydroxide, dissolve it in 1,000ml of boiled and cooled water, and shake well.
4.6 Sodium thiosulfate standard solution: c(Na2S2O3)=0.1mol/l, it shall be prepared and calibrated in accordance with GB 601, 4.6.
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4.7 Starch indicator solution: 10g/l, weigh 1.0g of soluble starch, add 10ml of water to make paste, pour it into 100ml of boiling water while stirring, boil it slightly for 2min, then let it stand, and take the supernatant for use. This solution is prepared before use.
5 Apparatus
5.1 Long-necked flask: 500ml.
5.2 Volumetric flask: 1,000ml.
5.3 Pipette: 20ml and 25ml.
5.4 Alkali burette: 50ml.
5.5 Measuring cylinder: 5ml, 50ml and 100ml.
5.6 Iodine flask: 500ml.
5.7 Analytical balance: with a sensitivity of 0.0001g.
5.8 Steam generator.
6 Test piece
Ethanol solution of phenolic resin.
7 Analytical procedures
7.1 Weigh 1.5~2.0g of test portion from test piece (6) by decrement method, accurate to 0.0001g, put it into a long-necked flask, add 20ml of sodium hydroxide solution (4.5), shake and dissolve it, then add 40ml of phosphoric acid solution (4.4) and 60ml of water, and connect it with steam generator (5.8) for distillation. Receive the distillate in a volumetric flask (5.2). When the distillate reaches more than 700ml, or the distillate is tested with bromine water and there is no white precipitation, stop distillation. Remove the volumetric flask, dilute it with water to the marking line, and shake well to obtain Solution A.
7.2 Pipette (5.3) 25ml of Solution A into iodine flask (5.6), add 20.0ml of bromine solution (4.2) and 5ml of hydrochloric acid (4.1), plug the stopper immediately, seal the flask with water, shake well, and place it in the dark for 15min. Take out the iodine flask, carefully open the stopper, slowly inject 20ml of potassium iodide solution (4.3) along the gap between the stopper and the mouth, plug the stopper, fully oscillate, and place it in the dark for 10min. Flush the stopper and wall of flask with water, and then titrate with sodium thiosulfate standard solution (4.6). When the solution is light yellow, add 1ml of starch indicator solution (4.7), and continue to titrate it until the blue color disappears. Record the volume of the sodium thiosulfate standard solution consumed (v1).
7.3 Carry out blank test under the same conditions. Record the volume of the sodium thiosulfate standard solution consumed (v2).
8 Result calculation
8.1 Calculate the content of free phenol (FP) using the following equation:
where,
FP——the content of free phenols, %;
V1——the volume of sodium thiosulfate standard solution consumed by the test portion, ml;
V2——the volume of sodium thiosulfate standard solution consumed in blank test, ml;
c——the actual concentration of sodium thiosulfate standard solution, mol/l;
m——the mass of test portion, g;
SC——the solids content of the test piece, %;
0.01568——the mass of phenol equivalent to 1.00ml of sodium thiosulfate solution [c(Na2S2O3)=1.000mol/l], g;
The solid content shall be tested in accordance with GJB 1059.1.
8.2 The analytical result is expressed by the arithmetic mean of at least two parallel determined values, which shall be rounded to two decimal places.
1 Subject content and applicable scope
2 Normative references
3 Summary method
4 Reagents
5 Apparatus
6 Test piece
7 Analytical procedures
8 Result calculation
9 Allowable deviation
10 Test report
Additional explanation
