1、BS ISO 6235:2016 Rubber, raw Determination of block polystyrene content Ozonolysis method BSI Standards Publication WB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS ISO 6235:2016 BRITISH STANDARD National foreword This British Standard is the UK implementation of ISO 6235:2016. The UK part
2、icipation 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
3、provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2016. Published by BSI Standards Limited 2016 ISBN 978 0 580 92746 1 ICS 83.040.10 Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard wa
4、s published under the authority of the Standards Policy and Strategy Committee on 30 September 2016. Amendments/corrigenda issued since publication Date Text affectedBS ISO 6235:2016 ISO 2016 Rubber, raw Determination of block polystyrene content Ozonolysis method Caoutchouc brut Dosage du polystyrn
5、e squenc Mthode de lozonolyse INTERNATIONAL STANDARD ISO 6235 Third edition 2016-09-15 Reference number ISO 6235:2016(E)BS ISO 6235:2016ISO 6235:2016(E)ii ISO 2016 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2016, Published in Switzerland All rights reserved. Unless otherwise specified, no
6、part of this publication 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
7、 body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.orgBS ISO 6235:2016ISO 6235:2016(E)Foreword iv 1 Scope . 1 2 Normative references 1 3 Principle 1 4 Reaction
8、s 1 5 Reagents 2 6 Apparatus . 2 7 Sample preparation . 2 7.1 General . 2 7.2 Latex . 3 7.3 Oil-extended solid rubber 3 8 Procedure. 3 9 Expression of results 4 10 Test report . 4 Bibliography 5 ISO 2016 All rights reserved iii Contents PageBS ISO 6235:2016ISO 6235:2016(E) Foreword ISO (the Internat
9、ional Organization for Standardization) is a worldwide 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 bee
10、n 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 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical stand
11、ardization. The procedures used to develop this document 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 accorda
12、nce with the editorial rules of the ISO/IEC Directives, 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
13、of any patent rights identified during the development 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 endor
14、sement. For an explanation on the meaning of ISO specific terms and expressions related to conformit y 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.htm
15、l. The committee responsible for this document is ISO/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 fo
16、llowing changes. the Normative References have been updated; 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 ST ANDARD ISO 6235:2016(E) Rubber,
17、 raw Determination of block polystyrene content Ozonolysis method WARNING 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 respo
18、nsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions. 1 Scope This International Standard specifies a method for the determination of the long polystyrene block content of raw uncompounded styrene-butadiene rubber
19、 (SBR) and raw uncompounded blends of block SBR. It is not applicable 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 f
20、rom 5 % (by weight) to 100 % (by weight). Rubbers having block 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 ma
21、y be used on rubbers containing gel if it has been proved that the gel does not interfere. 2 Normative references The 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.
22、 For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 1407, Rubber Determination of solvent extract ISO 4793, Laboratory sintered (fritted) filters Porosity grading, classification and designation 3 Principle A test portion is dissolved in dic
23、hloromethane and the ethylenic bonds in the rubber ruptured by reaction with ozone. The ozonides thus formed are subsequently decomposed by methanolic sulfuric acid solution. 4 Reactions The reactions upon which the method is based are as follows. a) Long, saturated, polystyrene blocks are not attac
24、ked by ozone, but small fragments (aldehydes and carboxylic acids) produced 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 b
25、locks are insoluble in methanolic sulfuric acid solution. ISO 2016 All rights reserved 1BS ISO 6235:2016ISO 6235:2016(E) c) It is possible to separate the relatively high molecular mass polystyrene blocks, which constitute the homopolymer blocks, from other soluble products, using methanolic sulfuri
26、c acid solution. 5 Reagents During the analysis, use only reagents of recognized 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
27、. 5.2 Methanol. 5.3 Potassium iodide, 3 % (by mass) solution. 5.4 Sulfuric acid, concentrated, = 1,84 Mg/m 3 . 5.5 Ethanol-toluene azeotrope (ET A). 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 boi
28、l the mixture with anhydrous calcium oxide (quicklime) under reflux for 4 h. Then distil the azeotrope and collect the fraction with a boiling range not exceeding 1 C, for use in the test. 5.6 2-Propanol. 6 Apparatus Use ordinary laboratory apparatus and the following. 6.1 Gooch crucibles, of fritte
29、d glass, having fine porosity, and of capacity 20 cm 3to 25 cm 3 , complying with the requirements 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. IM
30、PORTANT To minimize health hazards due to ozone, locate the ozone generator in a fume cupboard. 6.4 Magnetic stirrer. 6.5 Air condenser, if necessary (see 8.8). 7 Sample preparation 7.1 General In all cases, use random, unhomogenized test samples.2 ISO 2016 All rights reservedBS ISO 6235:2016ISO 623
31、5:2016(E) Do not mill the test samples before analysis. 7.2 Latex If the sample is latex, prepare a dried film as follows. Dilute 5 g of latex with 2 cm 3to 3 cm 3of water. Using a dropping tube, add the diluted latex to 100 cm 3of the vigorously stirred 2-propanol (5.6) at approximately 23 C. Allow
32、 to settle and decant the supernatant liquid. Stir vigorously with water to wash the coagulum and drain thoroughly 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 approxi
33、mately 50 C to constant mass. All handling shall be carried out in such a way as to avoid contamination. Use part 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 rubber For oil-extended solid rubb
34、ers, extract with ETA (5.5) using the apparatus specified in ISO 1407, dry and use part of this as the test portion. 8 Procedure WARNING Ozone reacts with unsaturated compounds to yield ozonides. Ozonides are stable in dilute solutions and these solutions are not hazardous. However, when concentrate
35、d and/or dried, the ozonides quickly decompose and may, in some cases, explode. Concentrated solutions of ozonides are 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
36、as a function of the expected block polystyrene content. 8.2 Place the test portion in a Drechsel bottle (6.2) and add 50 cm 3of 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 co
37、nnected to the oxygen tank. Connect the Drechsel bottle outlet to the inlet of another Drechsel bottle containing 100 cm 3of 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 s
38、top the flow of ozone and carefully add fresh solvent to the original solvent level. 8.4 Allow a flow of about 100 cm 3 /min of 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 fro
39、m the potassium iodide, appears. Prolonged reaction with ozone could produce cleavage of the saturated carbon chains. Therefore, 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 t
40、emperature of 25C for the ozonolysis, has been used to reduce cleavage of the saturated carbon chains. 1 8.5 Disconnect the Drechsel 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 Al
41、l rights reserved 3BS ISO 6235:2016ISO 6235:2016(E) 8.6 Transfer the dichloromethane solution, slowly and with constant stirring, into a 600 cm 3beaker containing 350 cm 3of methanol (5.2) to which five drops of concentrated sulfuric acid (5.4) have been added. Wash the Drechsel bottle with a few cu
42、bic centimetres of dichloromethane and transfer the washings into the beaker. 8.7 In most cases, the insoluble polystyrene settles to the 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 sol
43、ution, using the magnetic stirrer (6.4). To ensure that dichloromethane does not evaporate excessively, place the solution in a flask fitted 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,
44、after transferring to a suitable centrifuge container. 8.10 Transfer the precipitated polystyrene to a tared Gooch crucible (6.1) with the aid of a rubber “policeman”. Wash the precipitate copiously with methanol (5.2) to remove the dichloromethane, then with 100 cm 3of hot water to remove surfactan
45、ts 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. Repeat 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
46、 two determinations. 9 Expression of results Calculate the block styrene content, C, as a percentage by mass, to the nearest 0,2 %, from the following formula: where m 0 is the mass of the test portion, in grams; m 1 is the mass of the Gooch crucible and block polystyrene precipitate, in grams; m 2
47、is the mass of the Gooch crucible, in grams. 10 Test report The test report shall include the following information: a) a reference to this International 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 tw
48、o results from each determination, as well as the units in which they are expressed; d) any unusual features noted during the determination; e) any operation not included in this International Standard or in the International Standards to which reference is made, as well as any operation regarded as
49、 optional; f) the date of the test.4 ISO 2016 All rights reservedBS ISO 6235:2016ISO 6235:2016(E) Bibliography 1 Barnard D. Ozonolytic degradation of interpolymers 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 reserved IC S 83.040.10 Price based on 5 p
