1、BRITISH STANDARD BS 7164-28.2: 1995 ISO 8053:1995 Chemical tests for raw and vulcanized rubber Part 28: Methods for determination of copper content Section 28.2 Photometric methodBS7164-28.2:1995 This British Standard, having been prepared under the directionof the Sector Board for Materials and Che
2、micals, was published under the authority ofthe Standards Board and comesinto effect on 15October1995 BSI 10-1999 First published July 1990 Second edition October 1995 The following BSI references relate to the work on this standard: Committee reference PRI/23 Draft announced in BSI News August 1995
3、 ISBN 0 580 24760 0 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee PRI/23, Chemical testing of rubber, upon which the following bodies were represented: Malaysian Rubber Producers Research Association Ministry of Defence
4、 RAPRA Technology Ltd. Royal Society of Chemistry Amendments issued since publication Amd. No. Date CommentsBS7164-28.2:1995 BSI 10-1999 i Contents Page Committees responsible Inside front cover National foreword ii Introduction 1 1 Scope 1 2 Normative references 1 3 Principle 1 4 Reagents and mater
5、ials 1 5 Apparatus 2 6 Sampling 2 7 Procedure 2 8 Preparation of calibration curves 4 9 Expression of results 4 10 Test report 5 List of references Inside back coverBS7164-28.2:1995 ii BSI 10-1999 National foreword This Section of BS7164 has been prepared by Technical Committee PRI/23 and is identic
6、al with ISO8053:1995 Rubber and latex Determination of copper content Photometric method published by the International Organization for Standardization (ISO). This edition supersedes BS7164-28.2:1990 which is withdrawn. The Technical Committee has reviewed the provisions of ISO648:1977 to which ref
7、erence is made in the text, and has decided that they are acceptable for use in conjunction with this standard. A related British Standard to ISO648 is BS1583:1986 Specification for one mark pipettes. A British Standard does not purport to include all the necessary provisions of a contract. Users of
8、 British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International Standard Corresponding British Standard ISO 123:1985 BS 6057 Rubber latices Part 2:1987 Sampling (Identical)
9、ISO 247:1990 BS 7164 Chemical tests for raw and vulcanized rubber Part 5:1991 Methods for determination of ash content (Identical) ISO 1042:1983 BS 1792:1982 Specification for one-mark volumetric flasks (Identical) ISO 1795:1992 BS 6315:1993 Methods for sampling and further preparative procedures fo
10、r raw, natural and synthetic rubber (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be
11、 indicated in the amendment table on the inside front cover.BS7164-28.2:1995 BSI 10-1999 1 Introduction Copper in certain forms is known to catalyse the oxidative breakdown of natural rubber although the mechanism by which degradation is brought about is not fully understood. It is recognized also t
12、hat other forms of copper can be present in the rubber even in relatively large amounts, without degradation taking place, but in these cases there is always the possibility that under the influence of some chemicals, notably unsaturated acids, the copper could assume a more aggressive oxidative cat
13、alytic role. Clearly it would be an advantage to distinguish analytically between catalytically active and inactive forms, but no generally accepted method has yet been put forward for doing so. There is no alternative therefore but to determine the total amount of copper in the rubber. The method s
14、pecified in this International Standard is applicable to all the commonly used rubbers, including those containing chlorine. Another method for the determination of the copper content of rubber and latex is given in ISO6101-3:1988, Rubber Determination of metal content by atomic absorption spectrome
15、try Part3:Determination of copper content. WARNING Persons using this International Standard shall be familiar 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 app
16、ropriate safety and health practices and to ensure compliance with any national regulatory conditions. 1 Scope This International Standard specifies a photometric method for the determination of trace amounts of copper in raw rubber, latices and compounded rubber, both natural and synthetic. This me
17、thod may be applied to rubbers containing silica, provided that treatment with hydrofluoric acid is included in the procedure. The method is sensitive down to1mg/kg copper. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions
18、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 most recent editions of the standards ind
19、icated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 123:1985, Rubber latex Sampling. ISO 247:1990, Rubber Determination of ash. ISO 648:1977, Laboratory glassware One-mark pipettes. ISO 1042:1983, Laboratory glassware One-mark volumetric flasks. IS
20、O 1795:1992, Rubber, raw, natural and synthetic Sampling and further preparative procedures. 3 Principle A test portion is subjected to ashing or digestion in a mixture of concentrated sulfuric and nitric acids, followed by removal of excessive amounts of calcium (if present) and complexing of any i
21、ron present with ammonium citrate. After making alkaline, the aqueous solution is shaken with a solution of diethyldithiocarbamate in1,1,1-trichloroethane to form and extract the yellow copper complex. Spectrometric measurement of this solution, and comparison of the result with those for standard m
22、atching solutions, permit the quantitative determination of copper. 4 Reagents and materials WARNING All precautions and safeguards for carrying out trace-metal analysis shall be observed. All recognized health and safety precautions shall be observed when carrying out the procedures specified in th
23、is International Standard. During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 4.1 Sodium sulfate, anhydrous. 4.2 Sulfuric acid, concentrated, =1,84g/cm 3 . 4.3 Nitric acid, concentrated, =1,42g/cm 3 .BS7164-28.2:1995 2 BSI 10
24、-1999 4.4 Hydrochloric acid/nitric acid mixture, prepared as follows: Mix together 2 volumes of hydrochloric acid, =1,18g/cm 3 1 volume of nitric acid, =1,42 g/cm 3 3 volumes of water 4.5 Hydrogen peroxide, 30%(m/m). 4.6 Ammonia solution, =0,890g/cm 3 . 4.7 Hydrochloric acid, c(HCl) =5 mol/dm 3 . 4.
25、8 Hydrofluoric acid, =1,13g/cm 3 . 4.9 Citric acid solution Dissolve50g of citric acid in100cm 3of water. 4.10 Zinc diethyldithiocarbamate reagent Dissolve1g of solid zinc diethyldithiocarbamate in1000cm 3of1,1,1-trichloroethane. If zinc diethyldithiocarbamate is not available, the reagent may be pr
26、epared as follows: Dissolve1g of sodium diethyldithiocarbamate in water and add2g of zinc sulfate heptahydrate. Extract the resulting zinc diethyldithiocarbamate by shaking with100cm 3of1,1,1-trichloroethane in a separating flask. Separate the1,1,1-trichloroethane layer and dilute to1000cm 3with1,1,
27、1-trichloroethane. This reagent is stable for at least6 months when stored in a bottle of non-actinic glass. 4.11 Copper, standard solution, containing0,01g of Cu per cubic decimetre. Weigh0,393g of copper sulfate pentahydrate (CuSO 4 .5H 2 O) into a small beaker and dissolve in water. Add3cm 3of co
28、ncentrated sulfuric acid(4.2), transfer the solution to a1000cm 3volumetric flask(5.6), and dilute with water to the mark to form the stock solution. Pipette10cm 3of this stock solution into a100cm 3volumetric flask(5.6), and dilute with water up to the reference mark. 1 cm 3of this solution contain
29、s0,01mg of Cu. Prepare freshly from the stock solution when required. 4.12 Magnesium oxide 4.13 Litmus paper 4.14 Filter paper (hardened paper, resistant to acids). 5 Apparatus Ordinary laboratory apparatus, plus the following: 5.1 Photometer or spectrometer, capable of measuring absorbance at appro
30、ximately435nm, with matched cells, usually10mm path length. 5.2 Kjeldahl flask, of capacity100cm 3 , of silica or borosilicate glass. 5.3 Crucibles or dishes of porcelain, silica or platinum, of capacity50cm 3for small samples, appropriately larger for large samples. Porcelain or silica ware, especi
31、ally if etched, shall be lined with about0,1g of magnesium oxide(4.12), distributed over the base and partly up the sides. This minimizes the possibility that copper will be adsorbed on the etched walls and on fillers (if present) and instead the copper will now be preferentially adsorbed on the mag
32、nesium oxide. Platinum ware need not be treated with magnesium oxide. 5.4 Pipette, 25cm 3 , complying with the requirements of ISO648. 5.5 Balance, accurate to0,1mg. 5.6 One-mark volumetric flasks, 100cm 3and1000cm 3 , complying with the requirements ofISO1042. 5.7 Electric heating plate or gas burn
33、er with sandbath 5.8 Platinum rod, as stirrer. 6 Sampling 6.1 For raw rubber, carry out the sampling in accordance with ISO1795. 6.2 For latex, carry out the sampling in accordance with one of the methods specified in ISO123. 6.3 For rubber compounds, carry out the sampling to obtain as representati
34、ve a sample of the compound as possible. 7 Procedure The determination shall be carried out in duplicate. 7.1 Preparation of solid test samples may be by milling(see7.1.1) and/or by comminution (see7.1.2). 7.1.1 Mill the test sample by passing it6times between the cold rolls of a laboratory mill set
35、 to a nip of0,5mm, rolling the rubber into a cylinder after each pass and presenting the cylinder end-on to the rolls for the next pass. 7.1.2 Cut the test sample into pieces of not more than0,1g. 7.1.3 Weigh, to the nearest1mg, a test portion of between2g and10g from the sample taken as specified i
36、n6.1, 6.2 or6.3 and, in the case of solid samples, prepared as specified in7.1.BS7164-28.2:1995 BSI 10-1999 3 The size of the test portion depends upon the amount of copper present. It shall be selected to give an absorbance reading of0,3 to0,8 absorbance units or, in the case of very low concentrat
37、ions of copper, at least10times the absorbance reading of a blank. Appropriate test portion size will depend largely upon prior experience. 7.2 Dissolution of the test portion for the measurement of copper may be by ashing(7.2.1) or by acid digestion(7.2.2). If the rubber contains chlorine, the acid
38、 digestion method(7.2.2) shall be used. 7.2.1 Ash the test portion in accordance with method A or method B of ISO247:1990. After ashing, moisten the contents of the crucible with0,5cm 3to1cm 3of water, then add10cm 3of the acid mixture(4.4), cover with a watch glass and heat at about100 C for30min t
39、o60min. If the ash is totally dissolved, transfer the solution, quantitatively, to a small conical flask and proceed in accordance with7.3. If the ash is not totally dissolved, or if silicates are known to be present, proceed as follows. Repeat the ashing in accordance with method A or method B of I
40、SO247, using a new test portion and a fresh platinum crucible. After ashing, add a few drops of sulfuric acid(4.2) and heat to fuming. Cool, and add a further3 drops of sulfuric acid and5cm 3of hydrofluoric acid(4.8). Heat on the electric heating plate or sand bath(5.7) and evaporate to dryness whil
41、e stirring with the platinum rod(5.8). Repeat this procedure twice or until all silicates have been removed as indicated by the absence of white fumes of silicon tetrafluoride. Cool, moisten the contents of the crucible with0,5cm 3to1cm 3of water, add10cm 3of the acid mixture(4.4), cover with a watc
42、h glass and heat at about100 C for30min to60min. Transfer the solution, quantitatively, to a small conical flask and proceed in accordance with7.3. 7.2.2 Digest the test portion with4cm 3of sulfuric acid(4.2) and3cm 3of nitric acid(4.3) in a Kjeldahl flask(5.2). Warm the flask to start the reaction.
43、 NOTE 1The quantities of reagents in7.2.2 are for a2g test portion. If a larger test portion is used, appropriately larger portions of acid will be required. 7.2.2.1 If the reaction becomes too vigorous, cool the flask in a beaker of cold water. As soon as the initial reaction has subsided, heat the
44、 mixture gently until the vigorous reaction has ceased, and then more strongly until the mixture darkens. Add nitric acid in1cm 3portions, heating after each addition until darkening takes place. Continue this treatment until the solution becomes colourless or pale yellow and fails to darken on furt
45、her heating. If the digestion is prolonged, it may be necessary to add about1cm 3of sulfuric acid to prevent the contents of the flask from solidifying. To destroy the last traces of organic matter, cool the mixture and add0,5cm 3of hydrogen peroxide(4.5) and2 drops of nitric acid. Then heat the sol
46、ution to fuming, repeating the additions and the heating until there is no further reduction in the colour of the solution. Cool the solution, dilute with10cm 3of water and evaporate to fuming. Finally, cool the solution and add5cm 3of water. 7.2.2.2 If the test solution at this stage is free from i
47、nsoluble matter, transfer the acid digest to a conical flask and rinse the Kjeldahl flask with three5cm 3portions of water which are also added to the conical flask. If, however, the test solution contains insoluble matter, filter the supernatant liquid through a small filter paper into a conical fl
48、ask, retaining as much as possible of the insoluble residue in the Kjeldahl flask. Add5cm 3of hydrochloric acid(4.7) to the Kjeldahl flask, heat the solution to incipient boiling and swirl vigorously to wash the sides of the flask. Then pour the flask contents into the filter and collect in the coni
49、cal flask. Rinse the Kjeldahl flask with three5cm 3portions of water which are also added to the flask.BS7164-28.2:1995 4 BSI 10-1999 7.3 Add5cm 3of citric acid solution(4.9) to the contents of the conical flask and if, on cooling, the solution remains clear neutralize it by the drop-by-drop addition of ammonia solution(4.6), using a small piece of litmus paper as indicator. If, however, calcium sulfate crystallizes out from the solution on cooling, chill the flask and contents to about10 C, filter into a second conical flask and wash and f
