1、BS ISO 6235:2016Rubber, raw Determinationof block polystyrene content Ozonolysis methodBSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS ISO 6235:2016 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 6235:2016.The UK participati
2、on in its preparation was entrusted to Technical Committee PRI/50, Raw materials (including latex) for use in the rubber industry.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provision
3、s of a contract. Users are responsible for its correct application. The British Standards Institution 2016. Published by BSI Standards Limited 2016ISBN 978 0 580 92746 1 ICS 83.040.10 Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published
4、 under the authority of the Standards Policy and Strategy Committee on 30 September 2016.Amendments/corrigenda issued since publicationDate Text affectedBS ISO 6235:2016 ISO 2016Rubber, raw Determination of block polystyrene content Ozonolysis methodCaoutchouc brut Dosage du polystyrne squenc Mthode
5、 de lozonolyseINTERNATIONAL STANDARDISO6235Third edition2016-09-15Reference numberISO 6235:2016(E)BS ISO 6235:2016ISO 6235:2016(E)ii ISO 2016 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2016, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication
6、 may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of
7、the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 6235:2016ISO 6235:2016(E)Foreword iv1 Scope . 12 Normative references 13 Principle 14 Reactions 15 Reagents 26 Apparatus . 27 Sam
8、ple preparation . 27.1 General . 27.2 Latex . 37.3 Oil-extended solid rubber 38 Procedure. 39 Expression of results 410 Test report . 4Bibliography 5 ISO 2016 All rights reserved iiiContents PageBS ISO 6235:2016ISO 6235:2016(E)ForewordISO (the International Organization for Standardization) is a wor
9、ldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through 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
10、 that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this d
11、ocument and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Direc
12、tives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the develop
13、ment of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO spe
14、cific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.The committee responsible for this document is ISO/
15、TC 45, Rubber and rubber products, Subcommittee SC 3, Raw materials (including latex) for use in the rubber industry.This third edition cancels and replaces the second edition (ISO 6235:1995), of which it constitutes a minor revision with the following changes. the Normative References have been upd
16、ated; in 7.2, the text in ISO 4655:1985, 4.4 has been included, because this International Standard has been withdrawn; a Bibliography has been added.iv ISO 2016 All rights reservedBS ISO 6235:2016INTERNATIONAL STANDARD ISO 6235:2016(E)Rubber, raw Determination of block polystyrene content Ozonolysi
17、s methodWARNING Persons using this International Standard should be familiar with normal laboratory practice. This International Standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and
18、health practices and to ensure compliance with any national regulatory conditions.1 ScopeThis International Standard specifies a method for the determination of the long polystyrene block content of raw uncompounded styrene-butadiene rubber (SBR) and raw uncompounded blends of block SBR.It is not ap
19、plicable to blends of block SBR with EPDM, IIR, CSM and other halogenated rubbers.The method is applicable to raw, uncompounded latices of the above compositions and is suitable for rubbers having block polystyrene contents in the range from 5 % (by weight) to 100 % (by weight).Rubbers having block
20、polystyrene contents of less than 5 % (by weight) may yield incorrect results unless a correction factor, based on information gained by working with such rubbers, is applied.The method is intended for use on gel-free rubbers, but it may be used on rubbers containing gel if it has been proved that t
21、he gel does not interfere.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced docu
22、ment (including any amendments) applies.ISO 1407, Rubber Determination of solvent extractISO 4793, Laboratory sintered (fritted) filters Porosity grading, classification and designation3 PrincipleA test portion is dissolved in dichloromethane and the ethylenic bonds in the rubber ruptured by reactio
23、n with ozone. The ozonides thus formed are subsequently decomposed by methanolic sulfuric acid solution.4 ReactionsThe reactions upon which the method is based are as follows.a) Long, saturated, polystyrene blocks are not attacked by ozone, but small fragments (aldehydes and carboxylic acids) produc
24、ed by the ozonolysis and the relatively low molecular mass polystyrene fragments from scission within the random copolymer blocks are soluble in methanolic sulfuric acid solution.b) Relatively high molecular mass polystyrene blocks are insoluble in methanolic sulfuric acid solution. ISO 2016 All rig
25、hts reserved 1BS ISO 6235:2016ISO 6235:2016(E)c) It is possible to separate the relatively high molecular mass polystyrene blocks, which constitutethe homopolymer blocks, from other soluble products, using methanolic sulfuric acid solution.5 ReagentsDuring the analysis, use only reagents of recogniz
26、ed analytical quality and only distilled water or water of equivalent purity.5.1 Dichloromethane.It is essential that this reagent does not contain any impurities which could react with ozone to form an explosive mixture.5.2 Methanol.5.3 Potassium iodide, 3 % (by mass) solution.5.4 Sulfuric acid, co
27、ncentrated, = 1,84 Mg/m3.5.5 Ethanol-toluene azeotrope (ETA).Mix 7 volumes of absolute ethanol with 3 volumes of toluene. Alternatively, mix 7 volumes of commercial-grade ethanol with 3 volumes of toluene and boil the mixture with anhydrous calcium oxide (quicklime) under reflux for 4 h. Then distil
28、 the azeotrope and collect the fraction with a boiling range not exceeding 1 C, for use in the test.5.6 2-Propanol.6 ApparatusUse ordinary laboratory apparatus and the following.6.1 Gooch crucibles, of fritted glass, having fine porosity, and of capacity 20 cm3to 25 cm3, complying with the requireme
29、nts of ISO 4793.6.2 Drechsel (gas-washing) bottles.6.3 Ozone generator, capable of delivering about 2 % (by volume) of ozone.NOTE The actual ozone concentration depends on the type of generator used.IMPORTANT To minimize health hazards due to ozone, locate the ozone generator in a fume cupboard.6.4
30、Magnetic stirrer.6.5 Air condenser, if necessary (see 8.8).7 Sample preparation7.1 GeneralIn all cases, use random, unhomogenized test samples.2 ISO 2016 All rights reservedBS ISO 6235:2016ISO 6235:2016(E)Do not mill the test samples before analysis.7.2 LatexIf the sample is latex, prepare a dried f
31、ilm as follows.Dilute 5 g of latex with 2 cm3to 3 cm3of water. Using a dropping tube, add the diluted latex to 100 cm3of the vigorously stirred 2-propanol (5.6) at approximately 23 C. Allow to settle and decant the supernatant liquid. Stir vigorously with water to wash the coagulum and drain thoroug
32、hly on a Bchner funnel. Wash copiously with water.Steep overnight in cold water, drain off the water, rinse well with 2-propanol, shred and then dry in an open dish under vacuum at approximately 50 C to constant mass. All handling shall be carried out in such a way as to avoid contamination.Use part
33、 of this film as the test portion.If the test portion cannot be used immediately, store it under nitrogen in a cool, dark place.7.3 Oil-extended solid rubberFor oil-extended solid rubbers, extract with ETA (5.5) using the apparatus specified in ISO 1407, dry and use part of this as the test portion.
34、8 ProcedureWARNING Ozone reacts with unsaturated compounds to yield ozonides. Ozonides are stable in dilute solutions and these solutions are not hazardous. However, when concentrated and/or dried, the ozonides quickly decompose and may, in some cases, explode. Concentrated solutions of ozonides are
35、 also explosive.8.1 Cut the test sample into small pieces and weigh out, to the nearest 0,1 mg, 0,5 g to 1,0 g of the test sample thus prepared. Choose the mass of the test portion as a function of the expected block polystyrene content.8.2 Place the test portion in a Drechsel bottle (6.2) and add 5
36、0 cm3of dichloromethane (5.1).8.3 Dissolve the test portion at about 25 C with occasional stirring and connect the Drechsel bottle inlet to the ozone generator (6.3), which is connected to the oxygen tank. Connect the Drechsel bottle outlet to the inlet of another Drechsel bottle containing 100 cm3o
37、f potassium iodide solution (5.3).When performing this analysis, avoid decreasing the volume of solvent in the reaction vessel.If the level of solvent decreases, immediately stop the flow of ozone and carefully add fresh solvent to the original solvent level.8.4 Allow a flow of about 100 cm3/min of
38、oxygen, containing about 2 % (by volume) of ozone, to pass through the Drechsel bottle (6.2). Stop the gas flow 15 min after the yellow colour, due to free iodine freed from the potassium iodide, appears.Prolonged reaction with ozone could produce cleavage of the saturated carbon chains. Therefore,
39、adherence to the reaction time with ozone, as outlined in this International Standard, is mandatory. The use of di-n-butyl sulfide, which reacts with excess ozone, and a temperature of 25C for the ozonolysis, has been used to reduce cleavage of the saturated carbon chains.18.5 Disconnect the Drechse
40、l bottle (6.2) containing the dichloromethane solution from the ozone generator (6.3) and the Drechsel bottle containing the potassium iodide solution (5.3). ISO 2016 All rights reserved 3BS ISO 6235:2016ISO 6235:2016(E)8.6 Transfer the dichloromethane solution, slowly and with constant stirring, in
41、to a 600 cm3beaker containing 350 cm3of methanol (5.2) to which five drops of concentrated sulfuric acid (5.4) have been added. Wash the Drechsel bottle with a few cubic centimetres of dichloromethane and transfer the washings into the beaker.8.7 In most cases, the insoluble polystyrene settles to t
42、he bottom of the beaker after standing overnight.8.8 In some cases, the insoluble polystyrene does not settle so easily. When this occurs, agitate overnight the solution, using the magnetic stirrer (6.4). To ensure that dichloromethane does not evaporate excessively, place the solution in a flask fi
43、tted with an air condenser (6.5).8.9 If, after 24 h, the insoluble polystyrene has still not settled to the bottom of the beaker, the solution may be centrifuged, after transferring to a suitable centrifuge container.8.10 Transfer the precipitated polystyrene to a tared Gooch crucible (6.1) with the
44、 aid of a rubber “policeman”. Wash the precipitate copiously with methanol (5.2) to remove the dichloromethane, then with 100 cm3of hot water to remove surfactants and electrolytes, and finally again with methanol.8.11 Dry the precipitate for 2 h at 100 C, allow cooling in a desiccator and weigh. Re
45、peat the drying and weighing operations until the mass is constant.8.12 Carry out two determinations on each test sample. The test result is the average of the two determinations.9 Expression of resultsCalculate the block styrene content, C, as a percentage by mass, to the nearest 0,2 %, from the fo
46、llowing formula:Cmmm=120100wherem0is the mass of the test portion, in grams;m1is the mass of the Gooch crucible and block polystyrene precipitate, in grams;m2is the mass of the Gooch crucible, in grams.10 Test reportThe test report shall include the following information:a) a reference to this Inter
47、national Standard, i.e. ISO 6235:2016;b) all details necessary for complete identification of the sample;c) the individual results and the mean of the two results from each determination, as well as the unitsin which they are expressed;d) any unusual features noted during the determination;e) any op
48、eration not included in this International Standard or in the International Standards towhich reference is made, as well as any operation regarded as optional;f) the date of the test.4 ISO 2016 All rights reservedBS ISO 6235:2016ISO 6235:2016(E)Bibliography1 Barnard D. Ozonolytic degradation of inte
49、rpolymers of natural rubber with methyl methacrylate and styrene. J. Polym. Sci., Polym. Phys. Ed. 1956, 22 pp. 213216. Available at: http:/ ISO 2016 All rights reserved 5BS ISO 6235:2016ISO 6235:2016(E) ISO 2016 All rights reservedICS 83.040.10Price based on 5 pagesThis page deliberately left blankBSI is the national body responsible for preparing British Standards and other standards-related publications, information and services.BSI is incor
