1、BSI Standards PublicationRubber and plastics Polymer dispersions and rubber latices Determination of pHBS ISO 976:2013National forewordThis British Standard is the UK implementation of ISO 976:2013. It supersedes BS 6057-3.9:1996 which is withdrawn.The UK participation in its preparation was entrust
2、ed to TechnicalCommittee PRI/50, Rubber Raw, natural and synthetic, including latexand carbon black.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisions ofa contract. Users are respo
3、nsible for its correct application. The British Standards Institution 2013.Published by BSI Standards Limited 2013ISBN 978 0 580 77195 8ICS 83.040.10Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards
4、 Policy and Strategy Committee on 31 December 2013.Amendments/corrigenda issued since publicationDate Text affectedBRITISH STANDARDBS ISO 976:2013 ISO 2013Rubber and plastics Polymer dispersions and rubber latices Determination of pHCaoutchouc et plastiques Dispersions de polymres et latex de caoutc
5、houc Dtermination du pHINTERNATIONAL STANDARDISO976Fourth edition2013-12-01Reference numberISO 976:2013(E)BS ISO 976:2013ISO 976:2013(E)ii ISO 2013 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2013All rights reserved. Unless otherwise specified, no part of this publication may be reproduced o
6、r 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 the requester.ISO co
7、pyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 976:2013ISO 976:2013(E) ISO 2013 All rights reserved iiiContents PageForeword iv1 Scope . 12 Normative references 13 Reagents 14 Apparatus .
8、25 Sampling 26 Procedure. 26.1 General . 26.2 Maintenance of the electrode . 36.3 Calibration of the pH-meter . 46.4 Measurement of the pH of the test sample . 57 Expression of results 68 Test report . 6Annex A (informative) Precision . 7Bibliography 9BS ISO 976:2013ISO 976:2013(E)ForewordISO (the I
9、nternational 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
10、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 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnica
11、l standardization.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 a
12、ccordance 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. De
13、tails 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
14、 endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committee r
15、esponsible 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 fourth edition cancels and replaces the third edition (ISO 976:1996), which has been technically revised. It also incorporates the Amendment (
16、ISO 976:1996/Amd.1:2006). The following are the main changes: the normative references were updated; in (subclause) 4.2, the contact details of a provider of combined electrodes were deleted; the precision data were updated.iv ISO 2013 All rights reservedBS ISO 976:2013INTERNATIONAL STANDARD ISO 976
17、:2013(E)Rubber and plastics Polymer dispersions and rubber latices Determination of pHWARNING 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
18、use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.1 ScopeThis International Standard specifies a method for the determination of the pH of polymer dispersions and rubber latices (natural and
19、 synthetic) by means of a pH-meter equipped with a combined glass and silver reference electrode.The method is also suitable for prevulcanized latex and compounds containing polymer dispersions or rubber latices, including adhesives.NOTE The accuracy of the method decreases at pH values above 11.2 N
20、ormative 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 document (including any amendment
21、s) applies.ISO 123, Rubber latex SamplingISO 3696, Water for analytical laboratory use Specification and test methodsISO 15528, Paints, varnishes and raw materials for paints and varnishes Sampling3 ReagentsUse commercially available analytical-grade buffer solutions of known pH or, in the absence o
22、f commercial buffer solutions, prepare the solutions required (3.1, 3.2 and 3.3) using only reagents of recognized analytical grade and carbon dioxide-free distilled water or water of equivalent purity (grade 3 as defined in ISO 3696).3.1 Buffer solution, of nominal pH 7.Dissolve 3,40 g of potassium
23、 dihydrogen phosphate (KH2P04) and 3,55 g of disodium hydrogen phosphate (Na2HP04) in water and make up to 1 000 cm3in a volumetric flask.The pH of this solution is 6,87 at 23 C.Store the solution in a glass or polyethylene vessel, which is resistant to chemicals.3.2 Buffer solution, of pH 4.Dissolv
24、e 10,21 g of potassium hydrogen phthalate (KOOC C6H4COOH) in water and make up to 1 000 cm3in a volumetric flask.The pH of this solution is 4,00 at 23 C.Store the solution in a glass or polyethylene vessel, which is resistant to chemicals. ISO 2013 All rights reserved 1BS ISO 976:2013ISO 976:2013(E)
25、3.3 Buffer solution, of nominal pH 9Dissolve 3,814 g of sodium tetraborate decahydrate (Na2B4O710H2O) in water and make up to 1 000 cm3in a volumetric flask.The pH of this solution, when freshly prepared, is 9,20 at 23 C.Store the solution in a glass or polyethylene vessel, which is resistant to che
26、micals, and fitted with a soda-lime carbon dioxide trap. Replace the solution after one month.Alkaline buffer solutions are unstable; they absorb carbon dioxide from the atmosphere. When an alkaline buffer has been used for calibration, the accuracy can be verified by means of the buffer solution of
27、 pH 4.3.4 Reference electrolyte.Use 3 mol/dm3potassium chloride solution saturated with silver chloride.4 ApparatusUse usual laboratory equipment and the following.4.1 pH-meter, with an input impedance of at least 1012Q, a resolution of 0,01 pH units and equipped for temperature compensation.4.2 Com
28、bined electrode, in which the glass electrode is surrounded concentrically by the silver reference electrode. The reference electrolyte (3.4) is kept in electrical contact with the test sample by a chemically inert diaphragm, e.g. a retractable sleeve made of polytetrafluoroethylene or glass. This i
29、s supplied with the electrode by the electrode manufacturer.A typical combined electrode is shown in Figure 1.The glass electrode used shall be one recommended by the manufacturer as suitable over the pH range to be encountered (0 to 14 in the case of polychloroprene latices).Electrical contact betw
30、een the electrolyte and the test sample is maintained through a thin film of electrolyte between the sleeve and the electrode.The electrode functions linearly between pH 0 and the appearance of the alkaline error, which, depending on the sodium ion concentration, usually does not appear until the pH
31、 is over 11.4.3 Magnetic stirrer and magnetic bar.4.4 Electrode holder.5 SamplingCarry out the sampling of the rubber latex or polymer dispersion in accordance with one of the methods specified in ISO 123 or ISO 15528.6 Procedure6.1 GeneralIn order to reduce thermal and electrical hysteresis effects
32、, ensure that the temperatures of the test samples, electrode, demineralized or distilled rinsing water and buffer solutions are as close to one 2 ISO 2013 All rights reservedBS ISO 976:2013ISO 976:2013(E)another as possible. The temperatures of the test samples and buffer solutions shall not differ
33、 by more than 1 C. The temperature for the determination shall be 23 C 3 C (27 C 3 C in tropical countries).NOTE The pH variation over the range of 20 C to 30 C is negligible. In addition, the temperature compensator in the instrument should be set at the actual temperature.6.2 Maintenance of the el
34、ectrodeThe combined electrode (4.2) shall be maintained following the manufacturers instructions, paying particular attention to the following points.a) Refill the electrode with the reference electrolyte (3.4) through the filling hole, first removing the filling cap if one is fitted. Slightly withd
35、raw the seated sleeve to eliminate any latex deposits and allow a drop of the electrolyte to appear before reseating the sleeve. Prior to calibration and measurement, remove the cap on the electrolyte filling hole to allow the reference electrolyte to be at atmospheric pressure.b) When it is not in
36、use, keep the electrode with the junction immersed in the electrolyte. ISO 2013 All rights reserved 3BS ISO 976:2013ISO 976:2013(E)Key1 sliding head 6 reference electrolyte (3.4)2 filling hole 7 seated PTFE or glass diaphragm (sleeve)3 connector 8 internal buffer4 reference electrode 9 membrane5 int
37、ernal electrodeFigure 1 Typical combined electrode6.3 Calibration of the pH-meter6.3.1 Switch on the pH-meter (4.1) and allow the electronic circuit to stabilize. Calibrate the pH-meter following the manufacturers instructions. If not available, proceed as follows.6.3.2 Select two commercial buffer
38、solutions (see Clause 3), one of nominal pH 7 (i.e. close to the zero point of the electrode) and the other differing from the first by about 3 pH units and of a higher or lower pH corresponding to the sample to be tested. In the event that commercial buffer solutions are not available, use the appr
39、opriate prepared buffer solutions (3.1 and 3.2 or 3.3).4 ISO 2013 All rights reservedBS ISO 976:2013ISO 976:2013(E)6.3.3 Allow the temperature of the buffer solutions, the test sample, and the electrode to equilibrate at the specified temperature (see 6.1). Record the temperature and adjust the temp
40、erature correction on the pH-meter to correspond.6.3.4 Rinse the electrode with distilled or demineralized water (see Clause 3), and then with the buffer solution of nominal pH 7, so that the liquid runs down the length of the electrode.6.3.5 Introduce an adequate volume of the same buffer solution
41、into a suitable clean, dry glass or inert plastic vessel. Immerse the electrode in it, taking care that the level of reference electrolyte in the electrode remains about 5 cm higher than the level of the buffer solution to prevent any contamination of the electrode.Stir gently and allow the reading
42、to stabilize. Adjust the pH-meter using the zero-point adjustment control, so that the reading corresponds to the pH of the buffer solution. Withdraw the electrode and discard the portion of buffer solution.6.3.6 Rinse the electrode with water, followed by the chosen buffer solution, pH 4 (3.2) or p
43、H 9 (3.3), as described in 6.3.4.Instead of the prepared solution of pH 9 (3.3), commercial buffer solution with a pH in the range 9 to 11 can also be used, if available.6.3.7 Immerse the electrode in a quantity of the chosen buffer solution as described in 6.3.5. Allow the reading to stabilize befo
44、re adjusting the meter to the pH of the buffer solution, using the gradient adjustment control and without touching the zero-point control.Ensure that the electrode gradient is in the range -55,6 mV/pH unit to - 61,5 mV/pH unit, i.e. between 95 % and 103 % of the theoretical value (- 58,57 mV/pH uni
45、t at 23 C).If the electrode is outside this range, carry out the maintenance procedure specified in 6.2.Discard the portion of buffer solution.6.4 Measurement of the pH of the test sample6.4.1 Mix the test sample thoroughly to ensure that it is homogeneous.6.4.2 Rinse the electrode and measuring ves
46、sel, first with distilled or demineralized water, and then with some of the sample to be tested, as described in 6.3.4. Transfer an adequate volume into the vessel (an additional clean, dry vessel can be used) and immerse the electrode in it as described in 6.3.5. Stir gently.Allow the pH-meter read
47、ing to stabilize and record the pH.Clean the electrode by rinsing with distilled or demineralized water to remove any latex before it dries.6.4.3 Repeat the operations specified in 6.4.2 with a fresh portion of the test sample.If the new reading does not differ from the first by more than 0,1 pH uni
48、t, the determination is complete.If the two readings differ by more than 0,1 pH unit, make two further determinations, having first carried out all the checks necessary to detect any sources of error.If a series of consecutive determinations is to be made, recalibrate the pH-meter in accordance with
49、 6.3 at 30 min intervals or more frequently depending on the change found at each successive check. ISO 2013 All rights reserved 5BS ISO 976:2013ISO 976:2013(E)7 Expression of resultsCalculate the mean of the two readings that agree and round to the nearest 0,1 of a pH unit.Express the results in units of pH at 23 C if the determination was carried out at this temperature. Otherwise, specify the temperature of the determination.8 Test reportThe test report shall contain the following information:a)
