1、BRITISH STANDARDBS ISO 24698-1:2008Rubber, raw Determination of bound acrylonitrile content in acrylonitrile-butadiene rubber (NBR) Part 1: Combustion (Dumas) methodICS 83.040.10g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g5
2、4g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS ISO 24698-1:2008This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 June 2008 BSI 2008ISBN 978 0 580 58386 5National forewordThis British Standard is the UK imple
3、mentation of ISO 24698-1:2008. The UK participation in its preparation was entrusted to Technical Committee PRI/23, Test methods for rubber and non-black compounding ingredients.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does no
4、t purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.Amendments/corrigenda issued since publicationDate CommentsINTERNATIONALSTANDARDISO24698-1First edition2
5、008-05-15Reference numberISO 24698-1:2008(E)Rubber, raw Determination of bound acrylonitrile content in acrylonitrile-butadiene rubber (NBR) Part 1:Combustion (Dumas) methodCaoutchouc brut Dtermination du contenu en acrylonitrile li dans le caoutchouc acrylonitrile-butadine (NBR) Partie 1: Mthode pa
6、r combustion (Dumas)BS ISO 24698-1:2008ii iiiContents Page1 Scope 12 Normative references 13 Principle 14 Reagents and materials 25 Apparatus . 26 Sampling and preparation of the sample for the determination . 37 Procedure . 38 Calculation of bound acrylonitrile content 49 Precision . 410 Test repor
7、t 4Annex A (informative) Examples of automatic analysers based on the Dumas combustion method . 5Annex B (informative) Precision . 6BS ISO 24698-1:2008ivForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies(ISO member bodies). The wor
8、k of preparing International Standards is normally carried out through ISOtechnical committees. Each member body interested in a subject for which a technical committee has beenestablished has the right to be represented on that committee. International organizations, governmental andnon-governmenta
9、l, in liaison with ISO, also take part in the work. ISO collaborates closely with the InternationalElectrotechnical 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 ta
10、sk of technical committees is to prepare International Standards. Draft International Standardsadopted by the technical committees are circulated to the member bodies for voting. Publication as anInternational Standard requires approval by at least 75 % of the member bodies casting a vote.Attention
11、is drawn to the possibility that some of the elements of this document may be the subject of patentrights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 24698-1 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, SubcommitteeSC 2, Testing
12、and analysis.ISO 24698 consists of the following parts, under the general title Rubber, raw Determination of boundacrylonitrile content in acrylonitrile-butadiene rubber (NBR): Part 1: Combustion (Dumas) method Part 2: Kjeldahl methodBS ISO 24698-1:20081Rubber, raw Determination of bound acrylonitri
13、le content in acrylonitrile-butadiene rubber (NBR) Part 1:Combustion (Dumas) methodWARNING Persons using this part of ISO 24698 should be familiar with normal laboratory practice.This part of ISO 24698 does not purport to address all of the safety problems, if any, associated with itsuse. It is the
14、responsibility of the user to establish appropriate safety and health practices and toensure compliance with any national regulatory conditions.CAUTION Certain procedures specified in this part of ISO 24698 may involve the use or generation ofsubstances, or the generation of waste, that could consti
15、tute a local environmental hazard. Referenceshould be made to appropriate documentation on safe handling and disposal after use.1ScopeThis part of ISO 24698 specifies a method for the determination of the bound acrylonitrile content in NBR by anautomatic analyser which uses a combustion process. The
16、 method is also applicable to NBR latex.NOTE Parts 1 and 2 of this International Standard may not necessarily give the same result for any given rubber sample.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For datedreferences, only th
17、e edition cited applies. For undated references, the latest edition of the referenced document(including any amendments) applies.ISO 123, Rubber latex SamplingISO 1407:1992, Rubber Determination of solvent extractISO 1795, Rubber, raw natural and raw synthetic Sampling and further preparative proced
18、ures3 PrincipleThe nitrogen in a sample of raw rubber is converted into oxides of nitrogen in an atmosphere of high-purityoxygen in the combustion unit of the analyser. The oxides of nitrogen are then converted into elemental nitrogenby a catalyst in the reduction unit. The carbon dioxide and water
19、vapour produced are removed by absorption oranother means of separation. Finally, the resultant gas is passed, with a carrier gas, into a thermal conductivitydetector (TCD) to determine the nitrogen content.BS ISO 24698-1:200824 Reagents and materials4.1 Reference materials: L-aspartic acid, purity
20、; L-glutamic acid, purity ; EDTA, purity .4.2 Oxygen gas, purity or in accordance with the analyser manufacturers instructions.4.3 Carrier gases: helium gas, purity or in accordance with the analyser manufacturers instructions; carbon dioxide gas, purity or in accordance with the analyser manufactur
21、ers instructions.4.4 Ethanol, purity by volume.4.5 Methanol, purity by volume.5 Apparatus5.1 Automatic analyser.5.1.1 GeneralThe automatic analyser consists of the following components:a) a combustion unit, capable of maintaining a minimum operating temperature in accordance with themanufacturers in
22、structions for combustion of the sample in an atmosphere of high-purity oxygen;b) a high-purity oxygen feeder, capable of feeding enough high-purity oxygen for complete combustion;c) a reduction unit, capable of fully converting liberated nitrogenous compounds to nitrogen gas;d) an absorber (or anot
23、her type of separator) of by-products, capable of removing the water and carbondioxide formed;e) a TCD, capable of detecting the nitrogen gas formed;f) a microprocessor, capable of calibrating the apparatus with a standard reference material and of convertingthe detector response into mass of nitrog
24、en in the sample.5.1.2 Performance requirementsThe accuracy of the system shall be demonstrated by performing ten successive determinations using areference material such as L-aspartic acid, L-glutamic acid or EDTA. The mean of the ten determinations withthe reference material shall be within percen
25、tage points of the theoretical value. The relative standarddeviation shall be within by mass of nitrogen for the reference material.NOTE Relative standard deviation ( ) whereis the standard deviation;is the mean nitrogen content, in mass .5.2 Balance, weighing to the nearest .5.3 Extraction apparatu
26、s, as specified for method B in ISO 1407:1992.5.4 Beaker, capacity .greaterorequalslant 99 %greaterorequalslant 99 %greaterorequalslant 99 %greaterorequalslant 99,99 %greaterorequalslant 99,995 %greaterorequalslant 99,995 %greaterorequalslant 95 %greaterorequalslant 99,8 %0,20,5 % =swN 100swN%0,1 mg
27、300 cm3BS ISO 24698-1:200835.5 Stirrer.5.6 Sieve, aperture .5.7 Absorbent tissue.5.8 Drying oven, capable of maintaining a temperature of .5.9 Roll mill, the temperature of whose rolls can be maintained at .5.10 Combustion container, in accordance with the analyser manufacturers instructions.6 Sampl
28、ing and preparation of the sample for the determination6.1 Raw NBR rubberTake a sample of to in accordance with the method specified in ISO 1795, and pass the samplebetween the surfaces of the mill rolls with the nip set at and with the surface temperature ofthe rolls maintained at .Take a portion o
29、f about to from the sample prepared as specified above.Extract this portion with ethanol by method B in ISO 1407:1992 and rinse the extracted material twice with asmall amount of fresh ethanol. Pour the contents of the flask onto a clean sieve to recover the extractedmaterial. Gently blot the extrac
30、ted material with absorbent tissue to remove excess solvent, and dry the piecesof extracted rubber, separated from each other, in the oven at until the mass does not change bymore than over a period of .6.2 NBR latexTake about of NBR latex sample by the appropriate method in ISO 123.In order to coag
31、ulate the latex, add dropwise a small portion of the NBR latex sample, containing approximatelyof solid NBR, to of ethanol or methanol in the beaker, stirring the ethanol or methanol atthe same time. After all the latex has been added, continue stirring for another . Then pour the contents ofthe bea
32、ker onto a clean sieve to recover the coagulated polymer. Place the recovered polymer andof fresh solvent into the beaker and stir for . Again pour the contents of the beaker onto thesieve to recover the polymer. Finally, dry the recovered polymer between the surfaces of the mill rollswith the nip s
33、et at and with the surface temperature of the rolls maintained atuntil the mass does not change by more than over a period of .7 Procedure7.1 Operate the apparatus in accordance with the manufacturers instructions. A general procedure is asdescribed in 7.2 to 7.11.7.2 Take as the test portion to of
34、the extracted material prepared by the appropriate method inClause 6 and weigh it to the nearest in the combustion container. The size of the test portion shouldpreferably be chosen so that its total nitrogen content is between and . Input the mass of the testportion into the microprocessor.7.3 Plac
35、e the combustion container in the analyser and switch on the apparatus to start the determination.7.4 The combustion container is moved into the combustion unit where combustion of the test portion in anatmosphere of high-purity oxygen takes place.150m100C 2C100C 5C10 g 50 g0,2 mm 0,05 mm100C 5C3g 5
36、g150m100C 2C0,1 mg 10 min500 g5g 150 cm3300 cm35 min150m100 cm35 min150m0,2 mm 0,05 mm100C 5C 0,1 mg 10 min50 mg 500 mg0,1 mg5mg 15 mgBS ISO 24698-1:200847.5 The combustion gases are then transferred to the reduction unit by a carrier gas. (If necessary, a portionof the combustion gases is measured
37、by means of a measuring tube before being transferred to the reductionunit.)7.6 In the reduction unit, nitrogenous compounds in the combustion gases are completely converted intonitrogen gas, and residual oxygen gas is removed by absorption.7.7 The water and carbon dioxide formed are removed by an a
38、bsorber or another type of separator.7.8 Finally, the reduced combustion gases are passed into a TCD which determines the amount of nitrogengas produced.7.9 Residual combustion gases in the system are swept out with carrier gas or oxygen gas.7.10 The microprocessor converts the detector response int
39、o the nitrogen content of the test portion, inmass .7.11 Calibrate the apparatus with a reference material before carrying out each determination or series ofdeterminations.8 Calculation of bound acrylonitrile contentCalculate the bound acrylonitrile content of the sample, in mass , from the followi
40、ng equation:where is the nitrogen content determined, in mass .The test result is the value from a single determination of bound acrylonitrile content.9PrecisionAn interlaboratory test programme to determine the precision of this combustion method using automaticanalysers was conducted on NBR in 200
41、6 (see Annex B).10 Test reportThe test report shall include the following particulars:a) a reference to this part of ISO 24698;b) full identification of the rubber tested;c) full identification of the apparatus used;d) the reference material used;e) the result of the test;f) the date of the test.%wA
42、%wA= 3,79wNwN%BS ISO 24698-1:20085Annex A(informative)Examples of automatic analysers based on the Dumas combustion methodA.1 GeneralThere are differences between automatic analysers with regard to the combustion conditions (including thecombustion temperature) and the catalyst. There are also diffe
43、rences with regard to the method of reduction,the method of absorption of the by-products and the method of conversion of the detector response into themass of nitrogen in the sample. However, all automatic analysers based on the Dumas combustion methodwhich meet the performance requirements specifi
44、ed in 5.1.2 are suitable for the determination of the boundacrylonitrile content of NBR by the method specified in this part of ISO 24698.A.2 Examples of suitable automatic analysers Vario MAX CN, Rapid N III: Elementar Analysensysteme GmbH; Sumigraph NC-220F: Sumika Chemical Analysis Service, Ltd.;
45、 Macro Corder JM1000CN, Macro Corder JM3000N: J-Science Lab Co., Ltd.; Turbo Nitrogen 4040 Protein Analyzer: Costech International S.p.A.; Tru Spec N, CNS-2000: LECO Corporation.NOTE These are examples of suitable instruments available commercially. This information is given for the convenience ofus
46、ers of this part of ISO 24698 and does not constitute an endorsement by ISO of these instruments.%BS ISO 24698-1:20086Annex B(informative)PrecisionB.1 GeneralAn interlaboratory test programme (ITP) to determine the precision of this test method was conducted, usingautomatic analysers based on the co
47、mbustion method, on NBR in 2006. The precision evaluated was a type 1precision in accordance with ISO/TR 92721).Ten laboratories participated in the ITP and two of these analysed with two different analysers. For thelaboratories that submitted data from two types of analyser, the data from these sep
48、arate analysers wereincluded in the ITP as data from individual laboratories. This gave a database for twelve laboratories orpseudo-laboratories.Two different materials (NBR rubbers) were used in the ITP. A test result was taken to be the value from a singledetermination of bound acrylonitrile. Test
49、 results were obtained on three different days, at intervals of four daysbetween each of the three tests.The precision results as determined by this ITP should not be applied to acceptance or rejection testing of anygroup of materials or products without documentation that the results of this precision evaluation actually applyto the products or materials tested.B.2 Precision resultsThe precision results are based on test results
