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1、BRITISH STANDARD BS ISO 7780:1998 BS 7164-26.2: 1998 Rubber and rubber lattices Determination of manganese content Sodium periodate photometric methods ICS 83.040.10 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:29:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 7780:1998 This Briti
2、sh 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 October 1998 BSI 04-1999 ISBN 0 580 30358 6 National foreword This British Standard reproduces verbatim ISO 7780
3、:1998 and implements it as the UK national standard. It supersedes BS 7164-26.2:1990 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee PRI/23, Chemical testing of rubber, which has the responsibility to: aid enquirers to understand the text; present to
4、the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtai
5、ned on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” fa
6、cility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obli
7、gations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the ISO title page, page ii, pages 1 to 7 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment ta
8、ble on the inside front cover. Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:29:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 7780:1998 BSI 04-1999i Contents Page National forewordInside front cover Forewordii Introduction1
9、1Scope1 2Normative references1 3General method (for samples not affected by heavy loadings of fillers2 4Restricted method (limited to samples with filler loadings 10 %)4 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:29:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy:
10、 sheffieldun sheffieldun, na, Mon Nov 27 07:29:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:29:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 7780:1998 ii BSI 04-1999 Foreword ISO (the International Organization for Standardization) is
11、 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 been established has the right to be represen
12、ted 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 standardization. Draft International Standards
13、adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 7780 was prepared by Technical Committee ISO/TC 45, Rubber and rubber produc
14、ts. This second edition cancels and replaces the first edition (ISO 7780:1987) which has been technically revised. Descriptors: Rubber, latex, determination of content, manganese, spectrophotometric analysis. Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:29:45 GMT+00:00 2006, Uncontrolle
15、d Copy, (c) BSI BS ISO 7780:1998 BSI 04-19991 Introduction Manganese 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 that other forms of manganese can be prese
16、nt, even in relatively large amounts, without degradation taking place. However, there is always the possibility in the case of compounded rubbers that, under the influence of some constituents of the compound (notably the unsaturated acids), the manganese could assume a more aggressive role. Clearl
17、y, 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 therefore no alternative to determining the total amount of manganese in the rubber. Little is known about the inf
18、luence of manganese on the catalytic oxidation of synthetic rubbers, although it is widely accepted that its effect may be less severe than is the case with natural rubber. Possibly for this reason, the determination of manganese in synthetic rubbers and in compounds based on synthetic rubbers is le
19、ss frequently carried out; nevertheless, the methods specified in this International Standard are applicable to all the commonly used elastomers. The first of the two specified methods, referred to as the general method, is believed to be applicable to all rubbers and compounded rubbers in all forms
20、. In this method, the ash from the rubber is taken through a fusion stage in order to obtain the manganese in soluble form; it is most suited to rubber compounds containing heavy loadings of inert fillers such as clay, or materials which form insoluble phosphates, for example titanium dioxide. The s
21、econd method, referred to as the restricted method, is shorter and suitable for raw rubbers, their corresponding latices, and rubber compounds not containing a heavy loading of the fillers referred to above. It is expected that the second method would be used more frequently. For those equipped with
22、 atomic absorption equipment, ISO 6101-4:1997, Rubber Determination of metal content by atomic absorption spectrometry Part 4: Determination of manganese content, may be used in place of ISO 7780. Both standards should be consulted because there may be some background material in each which could be
23、 useful before choosing the most desirable method for the determination of manganese in raw and vulcanized rubbers and latices. WARNING Persons using this International Standard should be familiar with normal laboratory practice. This standard does not purport to address all of the safety problems,
24、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 Scope This International Standard specifies photometric methods for the determination of manganese, after oxi
25、dation with sodium periodate, in rubbers and rubber latices. Both methods contain provisions for analysis of chlorine-containing rubber. Clause 3 specifies a method for compounded or vulcanized rubbers which is not affected by heavy loadings of fillers such as synthetic and natural silicates or calc
26、ium carbonates in various forms, or by the presence of compounding ingredients which form an insoluble phosphate under the conditions of the test. Clause 4 specifies a method for raw and compounded natural and synthetic rubbers and latices which do not contain heavy loadings (more than about 10 %) o
27、f inert silicate fillers or any ingredient such as titanium dioxide which under the conditions of test will form an insoluble phosphate. 2 Normative references The following standards contains provisions which, through reference in this text, constitute provisions of this International Standard. At
28、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 indicated below. Members of IEC and IS
29、O maintain registers of currently valid International Standards. ISO 123:, Rubber latex Sampling1). ISO 124:1997, Latex, rubber Determination of total solids content. ISO 1795:1992, Rubber, raw, natural and synthetic Sampling and further preparative procedures. ISO 4793:1980, Laboratory sintered (fr
30、itted) filters Porosity grading, classification and designation. 1) To be published. (Revision of ISO 123:1985) Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:29:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 7780:1998 2 BSI 04-1999 3 General method (for samples not affected by heav
31、y loadings of fillers) 3.1 Principle In the presence of chlorine, digestion with sulfuric acid is required, followed by reaction with nitric acid. This procedure is carried out in a Kjeldahl flask. If silicates are present, the digested test portion is treated with sulfuric and hydrofluoric acids to
32、 volatilize any silicon as silicon tetrafluoride. In the absence of chlorine, the rubber is ashed in a platinum crucible and treated with sodium fluoroborate. After either procedure, the manganese is oxidized to permanganate by boiling with sodium periodate. The manganese concentration is determined
33、 by spectrophotometric measurement at 525 nm. 3.2 Reagents During the analysis, wherever possible, use only reagents of recognized analytical grade, suitable for use in trace-metal analysis, and only stabilized water (see 3.2.5). 3.2.1 Sodium fluoroborate If analytical grade is not available, prepar
34、e this reagent as follows. Dissolve 110 g of technical-grade sodium fluoroborate in 100 cm3 of water warmed to about 35 C. After filtering through a filter paper, cool the solution to room temperature and add 100 cm3 of 96 % (V/V) ethanol whilst stirring. Filter off the crystalline precipitate on to
35、 a filter paper in a Buchner funnel and drain thoroughly under slight vacuum, then transfer to a shallow porcelain or glass dish and dry at about 50 C under vacuum. 3.2.2 Sodium periodate. 3.2.3 Sulfuric acid, = 1,84 Mg/m3. 3.2.4 Nitric acid, = 1,42 Mg/m3. 3.2.5 Stabilized water To approximately 1 d
36、m3 of water, add about 0,1 g of potassium permanganate together with a few drops of sulfuric acid. Distil the water through an effective spray trap, discarding the first and last 50 cm3 of distillate. Collect the rest of the distillate and store in a glass-stoppered bottle. 3.2.6 Potassium permangan
37、ate solution, approximately 30 g/dm3. 3.2.7 Manganese, standard solution, corresponding to 10 mg of manganese per cubic decimetre. A solution prepared in either of the following ways may be used: a) Weigh 0,720 g of potassium permanganate (KMnO4) into a small beaker and dissolve in water containing
38、2 cm3 of sulfuric acid (3.2.3). Add water saturated with sulfur dioxide until the solution is colourless. Boil the solution for 15 min, cool, transfer to a 500 cm3 volumetric flask and dilute to the mark with water. b) Weigh 0,770 g of manganese sulfate (MnSO4.H2O) into a small beaker and dissolve i
39、n water containing 2 cm3 of sulfuric acid (3.2.3). Transfer the solution to a 500 cm3 volumetric flask and dilute to the mark with water. This solution should be stable for at least a month. Pipette 10 cm3 of either solution a) or solution b) into a second 500 cm3 volumetric flask and again dilute t
40、o the mark with water. 1 cm3 of this standard solution contains 0,01 mg of manganese. Prepare the solution just before use. 3.2.8 Hydrogen peroxide, 30 % (V/V) solution in water. 3.2.9 Hydrofluoric acid, = 1,12 Mg/m3. 3.3 Apparatus Ordinary laboratory apparatus, plus the following: 3.3.1 Photometer
41、or spectrophotometer, capable of measuring absorbance at approximately 525 nm, and matched cells. 3.3.2 Platinum crucible (30 cm3 nominal capacity is suitable). 3.3.3 Heat-resistant, thermally insulating board, approximately 100 mm square and 6 mm thick, with a hole in the centre to support the cruc
42、ible so that approximately two-thirds projects below the board. 3.3.4 Muffle furnace, capable of being maintained at a temperature of 550 C 25 C. 3.3.5 Sintered-glass filter, porosity grade P 40 (see ISO 4793). 3.3.6 Electrical heating plate or gas burner with sandbath. 3.3.7 Kjeldahl flask, of capa
43、city 250 cm3. 3.3.8 Platinum rod, as stirrer. 3.4 Sampling At all stages of sampling and sample preparation, take care to avoid contamination of the rubber. 3.4.1 Raw rubber Perform sampling in accordance with ISO 1795. Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:29:45 GMT+00:00 2006,
44、Uncontrolled Copy, (c) BSI BS ISO 7780:1998 BSI 04-19993 3.4.2 Latex Perform sampling in accordance with one of the methods specified in ISO 123. 3.4.3 Compounded and vulcanized rubbers Cut out a 50 g sample, if necessary from more than one piece so that proper representation is achieved. 3.5 Proced
45、ure 3.5.1 Preparation of test portion 3.5.1.1 Raw rubber From the sample taken in 3.4.1, weigh out a 10 g test portion to the nearest 10 mg. 3.5.1.2 Latex Thoroughly mix the latex obtained in 3.4.2, take a portion containing about 10 g of total solids, dry to constant mass as specified in ISO 124, a
46、nd cut into small pieces. 3.5.1.3 Compounded and vulcanized rubbers From the sample taken in 3.4.3, weigh out a 10 g test portion to the nearest 10 mg. 3.5.2 Preparation of test solution 3.5.2.1 Ashing the test portion in the absence of chlorine Transfer the test portion to a weighed platinum crucib
47、le (3.3.2) which is supported in the hole in the heat-resistant, thermally insulating board (3.3.3). Start the preparation of a blank solution at the same time, using a similar crucible but omitting the test portion, and continue by treating the test portion and the blank in an identical manner. Hea
48、t the crucible and contents with a gentle gas flame until a dry carbonaceous residue remains and then transfer the crucible to the muffle furnace (3.3.4) maintained at a temperature of 550 C 25 C and heat until all carbon has been oxidized. Allow the crucible to cool in a desiccator, weigh it to det
49、ermine the mass of ash and then, from a fine pipette, add an amount of sulfuric acid (3.2.3) drop by drop round the walls of the crucible just sufficient to moisten the ash. Heat gently until fuming ceases and then again at about 550 C for a few minutes. Repeat the treatment of the ash with the sulfuric acid, adding the acid as before from a fine pipette, heating gently until fuming ceases, and then again at about 550 C for a few minutes. After cooling again to room temperature, add to the crucible 8 parts by mass of sodium fluoroborate (3