1、December 2016 English price group 9No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 83.040.10!%n=“2597526www.din.deD
2、IN ISO 976Rubber and plastics Polymer dispersions and rubber latices Determination of pH (ISO 976:2013),English translation of DIN ISO 976:2016-12Kautschuk und Kunststoffe PolymerDispersionen und KautschukLatices Bestimmung des pHWertes (ISO 976:2013),Englische bersetzung von DIN ISO 976:2016-12Caou
3、tchouc et plastiques Dispersions de polymres et latex de caoutchouc Dtermination du pH (ISO 976:2013),Traduction anglaise de DIN ISO 976:2016-12SupersedesDIN ISO 976:200807, withdrawn 201504www.beuth.deDocument comprises 13 pagesDTranslation by DIN-Sprachendienst.In case of doubt, the German-languag
4、e original shall be considered authoritative.01.17DIN ISO 976:2016-12 2 A comma is used as the decimal marker. Contents Page National foreword . 3 National Annex NA (informative) Bibliography 4 1 Scope 5 2 Normative references 5 3 Reagents . 5 4 Apparatus . 6 5 Sampling . 6 6 Procedure. 7 6.1 Genera
5、l 7 6.2 Maintenance of the electrode . 7 6.3 Calibration of the pH-meter 8 6.4 Measurement of the pH of the test sample. 9 7 Expression of results . 10 8 Test report 10 Annex A (informative) Precision . 11 Bibliography . 13 DIN ISO 976:2016-12 3 National foreword This document (ISO 976:2013) has bee
6、n prepared by Technical Committee ISO/TC 45 “Rubber and rubber products”, Subcommittee SC 3 “Raw materials (including latex) for use in the rubber industry”. The responsible German body involved in its preparation was DIN-Normenausschuss Kunststoffe (DIN Standards Committee Plastics), Working Commit
7、tee NA 054-01-03 AA Physikalische, rheologische und analytische Prfungen. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. DIN and/or DKE shall not be held responsible for identifying any or all such patent rights. The DIN Standard
8、s corresponding to the International Standards referred to in this document are as follows: ISO 123 DIN ISO 123 ISO 3696 DIN ISO 3696 ISO 15528 DIN EN ISO 15528 Amendments This standard differs from DIN ISO 976:2008-07 (withdrawn 2015-04) as follows: a) the scope has been revised; b) normative refer
9、ences have been updated; c) in Subclause 4.2, the contact data of a manufacturer of combined electrodes have been deleted; d) Annex A “Precision” has been revised; e) a Bibliography has been included; f) the standard has been editorially revised. Previous editions DIN 53785: 1971-12 DIN 53606: 1980-
10、08 DIN ISO 976: 1998-05, 2008-07 DIN ISO 976:2016-12 4 National Annex NA (informative) Bibliography DIN EN ISO 15528, Paints, varnishes and raw materials for paints and varnishes Sampling DIN ISO 123, Rubber latex Sampling DIN ISO 3696, Water for analytical laboratory use Specification and test meth
11、ods 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 use.
12、 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 syn
13、thetic) 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 Norma
14、tive 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 amendments) a
15、pplies.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 of co
16、mmercial 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 dih
17、ydrogen 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.Dissolve 10
18、,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.5 DIN ISO 976:2016-12 3.3 Buffer solution, of nominal pH 9Dissolv
19、e 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 chemicals, and fitted with a soda-lime carbon
20、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 pH 4.3.4 Reference electrolyte.Use 3 mol/d
21、m3potassium chloride solution saturated with silver chloride.4 ApparatusUse usual laboratory equipment and the following.4.2 Combined electrode, in which the glass electrode is surrounded concentrically by the silver reference electrode. The reference electrolyte (3.4) is kept in electrical contact
22、with the test sample by a chemically inert diaphragm, e.g. a retractable sleeve made of polytetrafluoroethylene or glass. This is 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 manuf
23、acturer as suitable over the pH range to be encountered (0 to 14 in the case of polychloroprene latices).Electrical contact between 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
24、and the appearance of the alkaline error, which, depending on the sodium ion concentration, usually does not appear until the pH 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
25、the methods specified in ISO 123 or ISO 15528.6DIN ISO 976:2016-12 N1)National footnote: There is an error in the original ISO document. The correct unit is “”. 4.1 pH-meter, with an input impedance of at least 1012QN1), a resolution of 0,01 pH units and equipped for temperature compensation. anothe
26、r as possible. The temperatures of the test samples and buffer solutions shall not differ 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 compen
27、sator in the instrument should be set at the actual temperature.6.2 Maintenance of the electrodeThe 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)
28、through the filling hole, first removing the filling cap if one is fitted. Slightly withdraw 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 ho
29、le to allow the reference electrolyte to be at atmospheric pressure.b) When it is not in use, keep the electrode with the junction immersed in the electrolyte.7 DIN ISO 976:2016-12 6 Procedure6.1 GeneralIn order to reduce thermal and electrical hysteresis effects, ensure that the temperatures of the
30、 test samples, electrode, demineralized or distilled rinsing water and buffer solutions are as close to one 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 internal electrodeFigure 1
31、 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 solutions (see Clause 3
32、), 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 appropriate prepared buffer
33、 solutions (3.1 and 3.2 or 3.3).8DIN ISO 976:2016-12 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 temperature correction on the pH-meter to correspond.6.3.4 Rinse t
34、he 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 into a suitable clean, dry glass or inert plastic vessel. Imme
35、rse 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 to stabilize. Adjust the pH-meter using the zero-point adjustm
36、ent 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 pH 9 (3.3), as described in 6.3.4.Instead of the prepared solut
37、ion 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 before adjusting the meter to the pH of the buffer solution, using
38、 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 unit at 23 C).If the electrode is outside this range, carry out t
39、he 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 vessel, first with distilled or demineralized water, and then wit
40、h 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 reading to stabilize and record the pH.Clean the electrode by rins
41、ing 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 unit, the determination is complete.If the two readings differ by
42、 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 6.3 at 30 min intervals or more frequently depending on the c
43、hange found at each successive check.9 DIN ISO 976:2016-12 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 te
44、mperature of the determination.8 Test reportThe test report shall contain the following information:a) a reference to this International Standard, i.e. ISO 976;b) sufficient information to identify the sample;c) the pH of the rubber latex or polymer dispersion, expressed to the nearest 0,1 pH unit,
45、and the temperature of the determination;d) any particular features noted during the test;e) any departure from the procedures specified in this International Standard or the International Standards to which it refers, as well as any operation considered as optional; f) the date and the place of the
46、 test.10DIN ISO 976:2016-12 Annex A (informative) PrecisionA.1 GeneralThe precision of this method was determined in accordance with ISO/TR 9272. Make reference to this Technical Report for terminology and explanations of statistical concepts.The precision details in this precision statement provide
47、 an estimate of the precision of this test method with the materials used in the particular interlaboratory programme (ITP) as described below. The precision parameters should not be used for acceptance/rejection testing of any group of materials without documentation that the parameters are applica
48、ble to those particular materials and the specific test protocol of this test method.The precision results are given in Table A.1. The precision is expressed on the basis of a 95 % confidence level for the values established for repeatability, r, and reproducibility, R.The results in Table A.1 are m
49、ean values and give an estimate of the precision of this test method as determined in the ITP conducted in 2011. Sixteen laboratories performed duplicate analyses on two samples, A and B, which were prepared from highly ammoniated latex. The bulk latex was strained and then homogenized by thorough blending and stirring prior to being subsampled into 1-l bottles labelled A and B. Thus, essentially, samples A and B were the same and were treated as such in the statistical computations. Each participating laboratory was required to carry
