1、BRITISH STANDARDBS EN ISO 8988:2006Plastics Phenolic resins Determination of hexamethylene-tetramine content Kjeldahl method, perchloric acid method and hydrochloric acid methodThe European Standard EN ISO 8988:2006 has the status of a British StandardICS 83.080.10g49g50g3g38g50g51g60g44g49g42g3g58g
2、44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN ISO 8988:2006This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 October
3、 2006 BSI 2006ISBN 0 580 49322 9National forewordThis British Standard was published by BSI. It is the UK implementation of EN ISO 8988:2006. It supersedes BS EN ISO 8988:1997 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee PRI/42, Fibre reinforced the
4、rmosetting plastics and prepregs.A list of organizations represented on PRI/42 can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard can
5、not confer immunity from legal obligations.Amendments issued since publicationAmd. No. Date CommentsEUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 8988September 2006ICS 83.080.10 Supersedes EN ISO 8988:1997 English VersionPlastics - Phenolic resins - Determination ofhexamethylenetetramine con
6、tent - Kjeldahl method, perchloricacid method and hydrochloric acid method (ISO 8988:2006)Plastiques - Rsines phnoliques - Dtermination de lateneur en hexamthylnettramine - Mthode Kjeldahl,mthode lacide perchlorique et mthode lacidechlorhydrique (ISO 8988:2006)Kunststoffe - Phenolharze - Bestimmung
7、desHexamethylentetramingehaltes - Kjeldahl-Verfahren,Perchlorsureverfahren und Salzsureverfahren (ISO8988:2006)This European Standard was approved by CEN on 26 August 2006.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this Europea
8、nStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, Fren
9、ch, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic
10、, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALI
11、SATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2006 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 8988:2006: EForeword This document (EN ISO 8988:2006) has been prepared by Technical
12、Committee ISO/TC 61 “Plastics“ in collaboration with Technical Committee CEN/TC 249 “Plastics“, the secretariat of which is held by IBN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by March 2007,
13、 and conflicting national standards shall be withdrawn at the latest by March 2007. This document supersedes EN ISO 8988:1997. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Be
14、lgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. Endorsement notice The text of
15、 ISO 8988:2006 has been approved by CEN as EN ISO 8988:2006 without any modifications. EN ISO 8988:2006Reference numberISO 8988:2006(E)INTERNATIONAL STANDARD ISO8988Third edition2006-09-01Plastics Phenolic resins Determination of hexamethylenetetramine content Kjeldahl method, perchloric acid method
16、 and hydrochloric acid method Plastiques Rsines phnoliques Dtermination de la teneur en hexamthylnettramine Mthode Kjeldahl, mthode lacide perchlorique et mthode lacide chlorhydrique EN ISO 8988:2006ii iiiContents Page Foreword iv 1 Scope . 1 2 Normative references . 1 3 Kjeldahl method 1 4 Perchlor
17、ic acid method 3 5 Hydrochloric acid method . 5 6 Test report . 7 EN ISO 8988:2006iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out thr
18、ough ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collabo
19、rates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Stand
20、ards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of
21、this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 8988 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 12, Thermosetting materials. This third edition cancels and replaces the second editio
22、n (ISO 8988:1995), which has been technically revised to include a hydrochloric acid method. EN ISO 8988:20061Plastics Phenolic resins Determination of hexamethylenetetramine content Kjeldahl method, perchloric acid method and hydrochloric acid method SAFETY STATEMENT Persons using this document sho
23、uld be familiar with normal laboratory practice, if applicable. This document does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any regulator
24、y requirements. 1 Scope This International Standard specifies three methods for the determination of the hexamethylenetetramine (“hexa”) content of phenolic resins. The three methods are equivalent. The Kjeldahl method described in Clause 3 is not applicable if there are other components containing
25、nitrogen in the phenolic resin. The perchloric acid method and the hydrochloric acid method described in Clause 4 and Clause 5, respectively, are only applicable if there are no other basic or acidic additives in the resin. If the resin contains additives which can be oxidized by perchloric acid, on
26、ly the hydrochloric acid method (Clause 5) is applicable. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (inc
27、luding any amendments) applies. ISO 385, Laboratory glassware Burettes 3 Kjeldahl method WARNING For safety reasons, the Kjeldahl determination must be carried out in a well ventilated fume cupboard. 3.1 General This clause specifies a method for the determination of total nitrogen, expressed as hex
28、amethylenetetramine, in phenolic resins. The method is applicable to hexamethylenetetramine contents of W 0,5 % (by mass). 3.2 Principle The hexamethylenetetramine in a test portion is converted to ammonium bisulfate by decomposition in hot concentrated sulfuric acid in the presence of a catalyst. T
29、he ammonium bisulfate is converted to sodium sulfate and ammonia by reaction with sodium hydroxide. The ammonia is distilled off and collected in hydrochloric acid. The excess hydrochloric acid is titrated with a standard volumetric solution of sodium hydroxide using a colorimetric indicator. EN ISO
30、 8988:20062 3.3 Reagents During the analysis, unless otherwise stated, use only reagents of recognized analytical grade, free of nitrogen, and only distilled water or water of equivalent purity. 3.3.1 Sulfuric acid, concentrated. 3.3.2 Kjeldahl catalytic mixture, consisting of 97 g of sodium sulfate
31、 decahydrate (Na2SO410H2O), 1,5 g of copper sulfate pentahydrate (CuSO45H2O) and 1,5 g of selenium (Se). 3.3.3 Sodium hydroxide, 30 % (by mass) solution. 3.3.4 Hydrochloric acid, c(HCl) = 0,10 mol/l. 3.3.5 Sodium hydroxide, standard volumetric solution, c(NaOH) = 0,10 mol/I. 3.3.6 Mixed indicator, s
32、olution. Dissolve 60 mg of methyl red and 40 mg of methylene blue in 100 ml of ethanol. 3.4 Apparatus Ordinary laboratory apparatus, plus the following: 3.4.1 Kjeldahl flask, capacity 250 ml or 300 ml, for the digestion. 3.4.2 Distillation apparatus (various models are available commercially). 3.4.3
33、 Burette, capacity 50 ml, graduated in 0,1 ml steps, conforming to ISO 385. 3.4.4 Analytical balance, accurate to 1 mg. 3.4.5 Silicon carbide crystals, for use as boiling chips. 3.5 Procedure 3.5.1 Digestion Weigh 1 g to 2 g of phenolic resin to the nearest 1 mg into a Kjeldahl flask (3.4.1). Add 5
34、g of the catalytic mixture (3.3.2) and 25 ml of concentrated sulfuric acid (3.3.1). Heat carefully until the colour of the mixture changes from black or amber to clear. When the mixture is clear, increase the rate of heating and heat for 5 min beyond the time of the colour change; the mixture may po
35、ssibly boil. Allow the digested liquid to cool almost to room temperature, just short of solidification. Add carefully 100 ml of water and transfer the solution quantitatively into the flask of the distillation apparatus, rinsing with water. Add a few silicon carbide crystals (3.4.5) to prevent bump
36、ing and two drops of mixed indicator solution (3.3.6). Add 30 % (by mass) NaOH solution (3.3.3) to this solution until it is basic. Then distill over the ammonia given off, together with water vapour, into a receiver containing 50 ml of hydrochloric acid (3.3.4). Continue the distillation until abou
37、t 300 ml of water has been collected. 3.5.2 Titration When the distillation is completed, add a few drops of mixed indicator solution (3.3.6) to the contents of the receiver and titrate the excess hydrochloric acid with sodium hydroxide solution (3.3.5), using the burette (3.4.3). EN ISO 8988:200633
38、.6 Expression of results The hexamethylenetetramine content, expressed as a percentage by mass, is given by the formula: 0100,35 ( )VVmwhere V0is the volume, in millilitres, of hydrochloric acid (3.3.4) in the receiver of the distillation apparatus; V1is the volume, in millilitres, of sodium hydroxi
39、de solution (3.3.5) used in the back-titration; m0is the mass, in grams, of the test portion. 3.7 Reproducibility The results are reproducible to within 0,30 % (by mass) hexamethylenetetramine. 3.8 Number of determinations Carry out the determination in duplicate. If the results differ by more than
40、5 %, repeat the determination, again in duplicate. If not, calculate the arithmetic mean of the two individual results. 4 Perchloric acid method 4.1 General This clause specifies a method for the determination of hexamethylenetetramine in phenolic resins by direct titration. The results of the deter
41、mination may be affected by the presence of acidic or basic additives. In such cases, the use of the Kjeldahl method is recommended. If additives oxidizable by perchloric acid are present, use the hydrochloric acid method. The method is applicable to hexamethylenetetramine contents of W 0,3 %. 4.2 P
42、rinciple One of the tertiary amine groups of the hexamethylenetetramine in a test portion is determined by titration with perchloric acid. 4.3 Reagents During the analysis, unless otherwise stated, use only reagents of recognized analytical grade, free of nitrogen, and only distilled water or water
43、of equivalent purity. 4.3.1 Hexamethylenetetramine, dry. 4.3.2 Acetone, analytical grade. 4.3.3 Perchloric acid, 70 % (by volume) solution. WARNING Perchloric acid is dangerous in the presence of organic matter since an explosion can occur if the perchloric acid is in excess. EN ISO 8988:20064 4.4 A
44、pparatus Ordinary laboratory apparatus, plus the following: 4.4.1 Magnetic stirrer. 4.4.2 Automatic burette, nominal volume at least 15 ml, graduated in 0,1 ml steps, with a stopcock made of polytetrafluoroethylene. 4.4.3 Beakers, capacity 100 ml. 4.4.4 Graduated cylinder, capacity 1 000 ml. 4.4.5 A
45、nalytical balance, accurate to 0,1 mg. 4.4.6 pH-meter. 4.5 Procedure 4.5.1 Preparation and titration of a solution of perchloric acid in acetone Into a 1 000 ml graduated cylinder (4.4.4), introduce 1 000 ml of acetone (4.3.2) then 8 ml of perchloric acid solution (4.3.3). Mix well. Standardize the
46、resulting solution with hexamethylenetetramine (4.3.1) as described below. Weigh 150 mg to 170 mg of hexamethylenetetramine (4.3.1) to the nearest 0,1 mg into a 100 ml beaker (4.4.3). Add 30 ml to 40 ml of acetone (4.3.2), and titrate as described in 4.5.2. NOTE 1 Darkening of the solution will not
47、affect the titration results. The titre T, expressed in milligrams of hexamethylenetetramine per millilitre of solution, is given by the formula: 12mVwhere m1is the mass, in milligrams, of hexamethylenetetramine; V2is the volume, in millilitres, of perchloric acid solution needed to reduce the appar
48、ent pH to just below zero. 4.5.2 Titration Into a 100 ml beaker, weigh (to the nearest 1 mg) a quantity of phenolic resin equal to 100 times the titre determined as in 4.5.1, add 30 ml to 40 ml of acetone (4.3.2) and insert a magnetic stirrer bar. Place the beaker on the magnetic stirrer (4.4.1). In
49、sert the glass electrode of the pH-meter (4.4.6) and switch on the stirrer and the pH-meter. When the resin has dissolved, add the perchloric acid solution prepared as in 4.5.1 dropwise until the pH-value drops suddenly below zero. As the resin dissolves in acetone more rapidly than hexamethylenetetramine, the pH-value may increase to above zero because residual hexamethylenetetramine may still be in the process of dissolving. Continue the titration until the pH-value remains constant, slightly below zero. EN ISO 89
