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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.
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
中华人民共和国国家军用标准 烧蚀材料用酚醛树脂测试方法 游离苯酚测试 GJB1059.3—90 Test method of phenolic resin for ablative materials Test of free phenols
式中：FP——游离苯酚含量，％； V1——试料所消耗的硫代硫酸钠标准溶液的毫升数，ml； V2——空白试验所消耗的硫代硫酸钠标准瘩液的毫升数，ml； c——硫代硫酸钠标准溶液的实际浓度，mol/1； m——试料质量，g； SC——试样的固体含量，％； 0.01568——与1.00ml硫代硫酸钠溶液[c(Na2S2O3)＝1.000mol/1]相当的苯酚的质量，g； 固体含量测试方法按GJB1059.1规定进行。 8.2 分析结果至少以两次平行测定值的算术平均值表示，保留两位小数。 9 允许差 平行测定值之间的绝对偏差不得超过0.5％。 10 试验报告 试验报告应包括以下内容： a. 本试验采用的标准； b. 样品名称、编号及批号； c. 样品来源、送样日期； d. 试验过程中的特殊现象及对结果有影响的事项； e. 试验结果； f. 试验人员、试验日期。 附加说明： 本标准由国家建筑材料工业局提出。
