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1、BRITISH STANDARD BS 6057-3.5: 1996 ISO 127:1995 Incorporating Amendment No. 1 Rubber latices Part 3: Methods of test Section 3.5: Determination of KOH number of natural rubber latices ICS 83.060 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:23:57 GMT+00:00 2006, Uncontrolled Copy, (c) BS
2、I BS 6057-3.5:1996 This British Standard, having been prepared under the direction of the Sector Board for Materials and Chemicals, was published under the authority of the Standards Board and comes into effect on 15 June 1996 BSI 2006 First published November 1985 Second edition June 1996 The follo
3、wing BSI references relate to the work on this standard: Committee reference PRI/51 Draft for comment 92/38077 DC ISBN 0 580 25594 8 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee PRI/51, Latex, upon which the following
4、bodies were represented: British Rubber Manufacturers Association Ltd. Malaysian Rubber Producers Research Association Medical Sterile Products Association Amendments issued since publication Amd. No.DateComments 1624428 April 2006 See national foreword Licensed Copy: sheffieldun sheffieldun, na, We
5、d Dec 06 15:23:57 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6057-3.5:1996 BSI 2006i Contents Page Committees responsibleInside front cover National forewordii Foreword to amendment A1iii 1Scope1 2Normative references1 3Definition1 4Reagents1 5Apparatus1 6Sampling1 7Procedure1 8Expression of resu
6、lts2 9Precision statement2 10Test report3 Annex A (informative) Determination of formaldehyde4 Annex B (informative) Example of a typical titration and calculation of end-point4 Figure B.1 Illustrative curve showing change of pH during titration5 Table 1 Estimate of precision of determination of KOH
7、 number3 Table B.1 Example of a typical filtration to show variation in pH4 List of references6 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:23:57 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6057-3.5:1996 ii BSI 2006 National foreword This British Standard has been prepared by Technic
8、al Committee PRI/51 and is identical with ISO 127:1995 Rubber, natural latex concentrate Determination of KOH number, including amendment 1:2006, published by the International Organization for Standardization (ISO). It supersedes BS 6057-3.5:1985 which is withdrawn. The start and finish of text int
9、roduced or altered by ISO amendment is indicated in the text by tags !“. Tags indicating changes to ISO text carry the number of the ISO amendment. For example, text altered by ISO amendment 1 is indicated in the text by !“. This publication does not purport to include all the necessary provisions o
10、f a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references Publication referred toCorresponding British Standard ISO 123:1985BS 6057 Rubber latices Part 2:1987 Sampling (Identical) IS
11、O 124:1992Part 3 Methods of test Section 3.2:1992 Determination of total solids content of rubber latices (Identical) ISO 125:1990Section 3.3:1990 Determination of alkalinity of natural rubber latex concentrate (Identical) ISO 976:1986Section 3.9:1990 Determination of pH (Identical) ISO 1802:1992Sec
12、tion 3.12:1992 Determination of boric acid content of natural rubber latex concentrate (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 6, an inside back cover and a back cover. This standard has been updated (see copyright date) a
13、nd may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:23:57 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6057-3.5:1996 BSI 20061 WARNING Persons using this standard should be famili
14、ar with normal laboratory practice. This 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 health practices and to ensure compliance with any national regulatory conditions. 1 Sco
15、pe This International Standard specifies a method for the determination of the KOH number of natural rubber latex concentrate which is preserved wholly or in part with ammonia. The method is applicable to latices containing boric acid. The method is not applicable to latices preserved with potassium
16、 hydroxide. It is not necessarily suitable for latices from natural sources other than Hevea brasiliensis, or for latices of synthetic rubber, compounded latex, vulcanized latex or artificial dispersions of rubber. 2 Normative references The following standards contain provisions which, through refe
17、rence in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the
18、 most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. !ISO 123:2001“, Rubber latex Sampling. !ISO 124:1997“, Rubber latices Determination of total solids content. !ISO 125:2003“, Natural rubber latex concentrate
19、Determination of alkalinity. !ISO 976:1996, Rubber and plastics Polymer dispersions and rubber latices Determination of pH. “ ISO 1802:1985, Natural rubber latex concentrate Determination of boric acid content. !ISO/TR 9272, Rubber and rubber products Determination of precision for test method stand
20、ards. “ 3 Definition For the purposes of this International Standard, the following definition applies. 3.1 KOH number (of latex) the number of grams of potassium hydroxide equivalent to the acid radicals combined with ammonia in latex concentrate containing 100 g of total solids (Definition taken f
21、rom ISO 1382:1982, Rubber Vocabulary/Add.2:1982.) 4 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water free of dissolved carbon dioxide, or water of equivalent purity. 4.1 Potassium hydroxide, standard volumetric solution, c(KOH) = 0,1 mol/dm3, ca
22、rbonate-free. 4.2 Potassium hydroxide, standard volumetric solution, c(KOH) = 0,5 mol/dm3, carbonate-free. 4.3 Formaldehyde, 45 g to 50 g in 1 dm3 of solution c(HCHO) = 1,5 mol/dm3 to 1,67 mol/dm3, acid-free, prepared by diluting concentrated formaldehyde with water and neutralizing with 0,1 mol/dm3
23、 potassium hydroxide solution (4.1), using as indicator the faint pink colour of phenolphthalein. Determine the concentration of the formaldehyde solution as described in Annex A. 5 Apparatus Standard laboratory glassware, plus the following: 5.1 pH-meter, conforming to ISO 976 but capable of being
24、read to 0,01 units. 5.2 Glass electrode, of a type suitable for use in solutions of pH up to 12,0. 5.3 Mechanical stirrer, with earthed motor and glass paddle, or magnetic stirrer. NOTE 1 An automatic titrator may be used provided it has been checked as giving the same result as the standard method.
25、 6 Sampling Carry out the sampling in accordance with one of the methods specified in ISO 123. 7 Procedure Calibrate the pH-meter by the method specified in ISO 976. If the total solids (wTS) and alkalinity (A) of the latex are not known, determine them in accordance with ISO 124 and ISO 125 respect
26、ively. If the latex contains boric acid and the content is not known, determine it in accordance with ISO 1802. Carry out the determination in duplicate. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:23:57 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6057-3.5:1996 2 BSI 2006 Weigh, to t
27、he nearest 0,1 g, into a 400 cm3 beaker a test portion (mass m) of the test sample containing approximately 50 g of total solids. If necessary, adjust the alkalinity to (0,5 0,1) % ammonia calculated with respect to the water phase by adding, while stirring, the required quantity of formaldehyde sol
28、ution (4.3). !Calculate the volume, in cubic centimetres, of formaldehyde solution to be added from the formula“ ! “ where c(HCHO) is the actual concentration, expressed in moles per cubic decimetre, of the formaldehyde solution (4.3). Dilute the latex with water to about 30 % total solids. Insert t
29、he electrodes of the pH-meter (5.1) into the diluted latex concentrate and record the pH. If the initial pH is less than 10,3, slowly add 5 cm3 of 0,5 mol/dm3 potassium hydroxide solution (4.2) while stirring slowly with the glass paddle or magnetic stirrer (5.3). Record the resultant equilibrium pH
30、 reading. With continued stirring, add 0,5 mol/dm3 potassium hydroxide solution (4.2) in 1 cm3 increments at regular (e.g. 15 s) intervals, recording the resultant equilibrium pH after each addition. Continue until the end-point has been passed. If the initial pH is 10,3 or higher, omit the initial
31、addition of 5 cm3 at one time and proceed directly to “add 0,5 mol/dm3 potassium hydroxide solution (4.2) in 1 cm3 increments” as described above. The end-point of the titration is the point of inflexion of the titration curve of the pH-value against the volume, in cubic centimetres, of potassium hy
32、droxide solution. At this point, the slope of the curve, i.e. the first differential, reaches a maximum and the second differential changes from a positive to a negative value. The end-point shall be calculated from the second differential on the assumption that the change from a positive to a negat
33、ive value bears a linear relation to the addition of potassium hydroxide during the 1 cm3 interval involved. An example of a typical titration and the calculation of the end-point is given in Annex B. The results of duplicate determinations shall agree to within 5 % (m/m). 8 Expression of results Ca
34、lculate the KOH number, expressed as a percentage by mass, of the latex concentrate from the formula where If the latex concentrate contains boric acid, subtract the KOH number equivalent to the boric acid from the KOH number obtained above. Calculate the KOH number equivalent to the boric acid pres
35、ent from the formula where wBA is the boric acid content, expressed as a percentage by mass. !9 Precision statement 9.1 The precision of this method was determined in accordance with ISO/TR 9272. Refer to this document for terminology and explanations of statistical concepts. 9.2 The precision detai
36、ls in this precision statement give an estimate of the precision of this test method with the materials used in the particular interlaboratory programme as described below. The precision parameters should not be used for acceptance/rejection testing of any group of materials without documentation th
37、at the parameters are applicable to those particular materials and the specific test protocol of this test method. 9.3 The precision results are given in Table 1. The precision is expressed on the basis of a 95 % confidence level for the values established for repeatability r and reproducibility R.“
38、 cis the actual concentration, expressed in moles of KOH per cubic decimetre, of the potassium hydroxide solution (4.2); Vis the volume, in cubic centimetres, of the nominally 0,5 mol/dm3 potassium hydroxide solution (4.2) required to reach the end-point; wTSis the total solids content, expressed as
39、 a percentage by mass, of the latex concentrate; mis the mass, in grams, of the test portion. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:23:57 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6057-3.5:1996 BSI 20063 !9.4 The results contained in Table 1 are mean values and give an estima
40、te of the precision of this test method as determined in an interlaboratory test programme (ITP) conducted in 2001. Thirteen laboratories performed triplicate analyses on two samples, A and B, which were prepared from highly ammoniated latex. The bulk latex was strained and then homogenized by thoro
41、ugh blending and stirring prior to being subsampled into 1-litre 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 out the test using these two samples on the dates
42、which had been given to the participants in the ITP. 9.5 A type 1 precision was determined, based on the sampling method used for the latex samples in the ITP. 9.6 Repeatability: The repeatability r (in measurement units) of this test method has been established as the appropriate value tabulated in
43、 Table 1. Two single test results, obtained in the same laboratory under normal test conditions, that differ by more than the tabulated value of r (for any given level) shall be considered to have come from different (non-identical) sample populations. 9.7 Reproducibility: The reproducibility R (in
44、measurement units) of this test method has been established as the appropriate value tabulated in Table 1. Two single test results, obtained under normal test conditions, that differ by more than the tabulated value of R (for any given level) shall be considered to have come from different (non- ide
45、ntical) sample populations. 9.8 Bias: In test method terminology, bias is the difference between an average test value and the reference (or true) test property value. Reference values do not exist for this test method since the value (of the test property) is exclusively defined by the test method.
46、 Bias, therefore, cannot be determined for this particular test method. Table 1 Estimate of precision of determination of KOH number 10 “ Test report The test report shall include the following information: a) a reference to this International Standard; b) all details necessary for complete identifi
47、cation of the sample; c) all details necessary for complete identification of the pH-meter used; d) the result obtained; e) the correction applied for boric acid, if present; f) details of any operation not included in this International Standard or regarded as optional; g) the date of the test. Mea
48、nWithin laboratoryBetween laboratories srrsRR 0,570,0070.020.0270,08 r = 2,83 sr where r is the repeatability (in measurement units) and sr is the within-laboratory deviation. R = 2,83 sR where R is the reproducibility (in measurement units) and sR is the between-laboratory standard deviation. Licen
49、sed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:23:57 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6057-3.5:1996 4 BSI 2006 Annex A (informative) Determination of formaldehyde The method given in previous editions of this International Standard appears not to have been widely used due to the fact that standard solutions of ammonia are considered to be unsatisfactory. Having regard to the consistent quality of analytical-grade concentrated formaldehyde solution, the majority of users prepare a standard solution of formaldehyde d