HG/T 2755-1996 Determination of hexamethylenetetramine content in phenolic resin
Some standard content:
HG /T 2755—1996
This standard is equivalent to the international standard ISO8988:1989 "Plastics-Determination of Hexamethylenetetramine Content in Phenolic Resins", and is completely identical with it in terms of technical content and writing format. This standard was proposed by the Technical Supervision Department of the Ministry of Chemical Industry of the People's Republic of China, and this standard is under the jurisdiction of the Plastic Resin Products Branch of the National Plastic Standardization Technical Committee (TC15/SC4). The drafting unit of this standard: Shanghai Plastics Research Institute The drafter of this standard: Tan Hongying,
The International Organization for Standardization (ISO) is a joint organization of national standard groups (ISO member groups) worldwide. The work of formulating international standards is carried out by ISO technical committees. Any member group interested in a project determined by a technical committee has the right to send representatives to participate in the technical committee. Governmental or non-governmental international organizations can also participate in this work by contacting ISO. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all subjects of electrotechnical standardization. Draft international standards adopted by the technical committees are circulated to the member bodies for voting before they are accepted as international standards by the ISO Council. According to ISO working procedures, at least 75% of the member bodies voting are required to vote for the standards to be valid. International Standard ISO 8988 was prepared by ISO/TC61 Technical Committee Plastics. 1 General
Chemical Industry Standard of the People's Republic of China
Determination of hexamethylenetetramine content in phenolic resin
HG / T 275S — 1996
idt ISO 8988 : 1989
This standard specifies two methods for the determination of hexamethylenetetramine content in phenolic resins. The two methods are equivalent. If other amino components are present in the phenolic resin, the Kjeldahl method described in Chapter 2 is not applicable. The perchloric acid method described in Chapter 3 is only applicable when there are no other alkaline or acidic additives in the resin.
Kjeldahl method
Warning: For safety reasons, Kjeldahl determinations must be carried out in a well-ventilated hood. 21 Scope
This chapter specifies the method for determining the total nitrogen content in phenolic resins, expressed as the hexamethylenetetramine content. 2.2 Principle
The hexamethylenetetramine in the sample and concentrated sulfuric acid are heated and decomposed in the presence of a catalytic mixture to convert it into ammonium bisulfate. The ammonium bisulfate reacts with sodium hydroxide to convert it into sodium bisulfate and ammonia. The nitrogen is evaporated and collected in the hydrochloric acid solution. The excess hydrochloric acid is titrated with a sodium hydroxide standard titration solution in the presence of an indicator. 2.3 Reagents
Unless otherwise specified, only recognized analytically pure reagents and distilled water, or water of equivalent purity, that do not contain nitrogen should be used in the analysis. 2.3.1 Concentrated sulfuric acid
2.3.2 Kjeldahl catalytic mixture: composed of 97 g sodium sulfate containing 10 crystal waters (Na,S010H,0), 1.5 g copper sulfate containing 5 crystal waters (CuSO,5H,O) and 1.5 g selenium (Se)2.3.3 Sodium hydroxide, 30% (m/m) solution2.3.4 Hydrochloric acid, c (HCI) = 0. 10 mol / L,2.3.5 Sodium hydroxide, standard titration solution, c (NaOH) = 0,10 mol / L.2.3.6 Mixed indicator solution: Dissolve 60 mg of methyl red and 40 mg of methylene blue in 100 mL of ethanol. 2.4 Instruments
Ordinary laboratory instruments and;
2.4.1 Gauge flask, capacity 250 mL or 300 mL, for heating and digestion; 2.4.2 Distillation apparatus (various commercial distiller). 2.4.3 Burette, capacity 50 mL, graduation value 0.1 mL, in line with the general requirements of laboratory glassware; 2.4.4 Analytical balance, sensitivity 1 mg
2.4.5 Silicon carbide zeolite, to prevent boiling over. 2.5 Procedure
2. 5. 1 Heating and digestion
Approved by the Ministry of Chemical Industry of the People's Republic of China on April 15, 1996, and January 1, 1997 Implementation
HG/T2755-1996
In a Kjeldahl flask (2.4.1), weigh 1-2 g of phenolic resin (accurate to 1 Ma), add 5 ml of catalytic mixture (2.3.2) and 25 mL of concentrated sulfuric acid (2.3.1), and heat carefully until the color of the digested mixture changes from black or amber to transparent. When it becomes transparent, increase the heating rate and continue heating for 5 minutes (except the time for color change), and keep boiling as much as possible. Cool the dissolved liquid to near room temperature, but do not allow it to solidify. Carefully add 100 L of water, transfer the solution quantitatively into a steaming bottle, rinse with water, add a small amount of silicon carbide zeolite (2.4.5) to prevent boiling, add sodium hydroxide solution (2.3.3) until an alkaline reaction occurs, then use a steam steamer to evaporate the generated ammonia and introduce it into a receiver containing 50 mL of hydrochloric acid (2.3.4). Continue distilling until about 300 mL of water is collected. 2.5.2 Titration
After the distillation is completed, add a few drops of mixed indicator solution (2.3.6) to the distillate in the receiver, and titrate the excess hydrochloric acid with sodium hydroxide standard titration solution (2.3.5) through a burette (2.4.3). 2.6 Explanation of results
The hexamethylenetetramine content, expressed as mass percentage, is calculated as follows: 0.35(V.-V,)
Where: V. Volume of hydrochloric acid (2.3.4) in the distillation receiver, mLY Volume of sodium hydroxide standard titration solution (2.3.5) used for back titration, mL; mo——sample mass, g.
2. Reproducibility
The reproducibility of the determination result of hexamethylenetetramine content should be within 0.30% (m/m), 2.8 Number of determinations
Carry out parallel determinations and calculate the arithmetic mean of the two test results. If the difference between the two test results is greater than 5%, repeat the parallel test.
3 High amino acid method
3.1 Scope
This chapter specifies the method for determining the hexamethylenetetramine content in phenolic resin by direct titration. The determination result may be affected by the presence of acidic or magnetic additives. In the presence of acidic or alkaline additives, the Kjeldahl method is used. 3.2 Principle
Use pernitrogen acid titration to determine the amino group of hexamethylenetetramine in the sample. 3.3 Reagents
Unless otherwise specified, only recognized analytical reagents and distilled water or water of comparable purity shall be used in the analysis. 3.3.1 Hexamethylenetetramine, dry,
3, 3.2 Acetone bZxz.net
3.3.3 Perchloric acid, 70% (m/m) solution Warning: Perchloric acid is a dangerous substance. In the presence of organic matter, excessive perchloric acid may cause an explosion. 3.4 Apparatus
Ordinary laboratory apparatus and:
3.4.1 Electromagnetic stirrer
3, 4.2 Automatic burette, nominal volume at least 15 mL, graduation value 0.1 m2 L, with polytetraoxyethylene cork. 3.4.3 Beaker, capacity 100 mL.
3.4.4 Beaker, capacity 1000 mL.
3.4.5 Analytical balance, sensitivity 0.1 mg and 1 mg respectively.3.4.6 pHt.
3.5 Procedure
3.5.1 Preparation and calibration of perchloric acid acetone solution HG/T 2755—1996
In a 1000 mL volumetric tube (3.4.4), add 8 mL of perchloric acid solution (3.3.3) and dilute to 1000 mL with acetone (3.3.2). mL.
Use hexamethylenetetramine (3.3.1) as follows to prepare the solution: In a 100mL beaker, weigh about 150~170mg hexamethylenetetramine (3.3.1), (accurate to 0.1mg), add 30~40mL acetone (3.3.2), and titrate as described in 3.5.2. Note: The blackening of the solution will not affect the titration result. The titer T, expressed in milligrams of hexamethylenetetramine per milliliter of solution, is calculated as follows: Where: m——mass of hexamethylenetetramine, g; V——volume of perchloric acid solution consumed when pH just drops to zero, mL.3.5.2 Titration
In a 100mL beaker. Weigh a quantity of phenolic resin equal to 100 times the titer measured in 3.5.1, add 30-40 mL of acetone (3.3.2), add a magnetic stirrer, place the beaker on the magnetic stirrer (3.4,1), insert the glass electrode of the pH meter (3.4.6), start the stirrer and the pH meter, and when the resin dissolves, slowly add the perchloric acid solution prepared in 3.5.1 until the pH value suddenly drops below zero. Since the resin dissolves faster in acetone than hexamethylenetetramine, some residual hexamethylenetetramine may still be dissolved, and the pH reading may rise above zero. Continue titrating until the pH reading is slightly below zero and remains constant. 3.6 Explanation of results
The content of hexamethylenetetramine is expressed as a percentage of mass and is calculated by the following formula: V,T×100
Where: V,—volume of perchloric acid solution used for titration, mLT—titer determined according to Article 3.5.1, m (hexamethylenetetramine)/mL (perfluoric acid); sample mass, mg.
37 Number of measurements
Carry out parallel measurements and calculate the arithmetic mean of the two test results. If the difference between the two test results is greater than 5%, repeat the parallel measurements.
4 Test report
The test report should include the following:
Indicate the method used in accordance with the industry standard and (Kjeldahl method or pernitrogen acid method): Complete identification of the test resin;
The content of hexamethylenetetramine expressed as a percentage of mass; - Single value:
- Average value:
Test date
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