1、BRITISH STANDARD BS ISO 7780:1998 BS 7164-26.2: 1998 Rubber and rubber lattices Determination of manganese content Sodium periodate photometric methods ICS83.040.10BSISO 7780:1998 This British Standard, having been prepared under the directionof the Sector Board forMaterials and Chemicals, waspublis
2、hed under the authorityof the Standards Boardand comes into effect on 15 October 1998 BSI 04-1999 ISBN 0 580 30358 6 National foreword This British Standard reproduces verbatim ISO7780:1998 and implements it as the UK national standard. It supersedes BS7164-26.2:1990 which is withdrawn. The UK parti
3、cipation 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 the responsible international/European committee any enquiries on the interpretation, or proposals for change, and ke
4、ep 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 obtained on request to its secretary. Cross-references The British Standards which implement international or European pub
5、lications 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” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary pr
6、ovisions 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 obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, theISO title pa
7、ge, page ii, pages1 to7 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 table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBSISO 7780:1998 BSI 04-1999 i Con
8、tents Page National foreword Inside front cover Foreword ii Introduction 1 1 Scope 1 2 Normative references 1 3 General method (for samples not affected by heavy loadings of fillers 2 4 Restricted method (limited to samples with filler loadings10%) 4ii blankBS ISO7780:1998 ii BSI 04-1999 Foreword IS
9、O (the International 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 co
10、mmittee 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 electro
11、technical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least75% of the member bodies casting a vote. International Standard ISO7780 was prepared by T
12、echnical Committee ISO/TC45, Rubber and rubber products. This second edition cancels and replaces the first edition (ISO7780:1987) which has been technically revised. Descriptors: Rubber, latex, determination of content, manganese, spectrophotometric analysis.BSISO7780:1998 BSI 04-1999 1 Introductio
13、n 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 present, even in relatively large amounts, without degradation
14、 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. Clearly, it would be an advantage to distinguish analytically b
15、etween 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 influence of manganese on the catalytic oxidation of synthet
16、ic 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 less frequently carried out; nevertheless, the methods spec
17、ified 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. In this method, the ash from the rubber is taken throug
18、h 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 second method, referred to as the restricted method, is sh
19、orter 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 atomic absorption equipment, ISO6101-4:1997, Rubber Dete
20、rmination of metal content by atomic absorption spectrometry Part4: Determination of manganese content, may be used in place of ISO7780. Both standards should be consulted because there may be some background material in each which could be useful before choosing the most desirable method for the de
21、termination 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, if any, associated with its use. It is the responsibility of
22、 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 oxidation with sodium periodate, in rubbers and rubber latices.
23、 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 calcium carbonates in various forms, or by the presence of compo
24、unding 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 about10%) of inert silicate fillers or any ingredient such as titanium di
25、oxide 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 the time of publication, the editions indicated were valid. Al
26、l 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 ISO maintain registers of currently valid International Standard
27、s. ISO123:, Rubber latex Sampling 1) . ISO124:1997, Latex, rubber Determination of total solids content. ISO1795:1992, Rubber, raw, natural and synthetic Sampling and further preparative procedures. ISO4793:1980, Laboratory sintered (fritted) filters Porosity grading, classification and designation.
28、 1) To be published. (Revision of ISO123:1985)BSISO 7780:1998 2 BSI 04-1999 3 General method (for samples not affected by heavy loadings of fillers) 3.1 Principle In the presence of chlorine, digestion with sulfuricacid is required, followed by reaction with nitric acid. This procedure is carried ou
29、t in a Kjeldahl flask. If silicates are present, the digested test portion is treated with sulfuric and hydrofluoric acids to 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 pro
30、cedure, the manganese is oxidized to permanganate by boiling with sodium periodate. The manganese concentration is determined by spectrophotometric measurement at525nm. 3.2 Reagents During the analysis, wherever possible, use only reagents of recognized analytical grade, suitable for use in trace-me
31、tal analysis, and only stabilized water (see3.2.5). 3.2.1 Sodium fluoroborate If analytical grade is not available, prepare this reagent as follows. Dissolve110g of technical-grade sodium fluoroborate in100cm 3of water warmed to about35 C. After filtering through a filter paper, cool the solution to
32、 room temperature and add100cm 3of96% (V/V) ethanol whilst stirring. Filter off the crystalline precipitate on to 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 about50 C under vacuum. 3.2.2 Sodium periodate.
33、 3.2.3 Sulfuric acid, =1,84Mg/m 3 . 3.2.4 Nitric acid, =1,42Mg/m 3 . 3.2.5 Stabilized water To approximately1dm 3of water, add about0,1g of potassium permanganate together with a few drops of sulfuric acid. Distil the water through an effective spray trap, discarding the first and last50cm 3of disti
34、llate. Collect the rest of the distillate and store in a glass-stoppered bottle. 3.2.6 Potassium permanganate solution, approximately30g/dm 3 . 3.2.7 Manganese, standard solution, corresponding to10mg of manganese per cubic decimetre. A solution prepared in either of the following ways may be used:
35、a) Weigh0,720g of potassium permanganate (KMnO 4 ) into a small beaker and dissolve in water containing2cm 3of sulfuric acid(3.2.3). Add water saturated with sulfur dioxide until the solution is colourless. Boil the solution for15min, cool, transfer to a500cm 3volumetric flask and dilute to the mark
36、 with water. b) Weigh0,770g of manganese sulfate (MnSO 4 .H 2 O) into a small beaker and dissolve in water containing2cm 3of sulfuric acid(3.2.3). Transfer the solution to a500cm 3volumetric flask and dilute to the mark with water. This solution should be stable for at least a month. Pipette10cm 3of
37、 either solutiona) or solutionb) into a second500cm 3volumetric flask and again dilute to the mark with water. 1cm 3of this standard solution contains0,01mg of manganese. Prepare the solution just before use. 3.2.8 Hydrogen peroxide, 30% (V/V) solution in water. 3.2.9 Hydrofluoric acid, =1,12Mg/m 3
38、. 3.3 Apparatus Ordinary laboratory apparatus, plus the following: 3.3.1 Photometer or spectrophotometer, capable of measuring absorbance at approximately525nm, and matched cells. 3.3.2 Platinum crucible (30cm 3nominal capacity is suitable). 3.3.3 Heat-resistant, thermally insulating board, approxim
39、ately100mm square and6mm thick, with a hole in the centre to support the crucible so that approximately two-thirds projects below the board. 3.3.4 Muffle furnace, capable of being maintained at a temperature of550 C 25 C. 3.3.5 Sintered-glass filter, porosity grade P40 (seeISO4793). 3.3.6 Electrical
40、 heating plate or gas burner with sandbath. 3.3.7 Kjeldahl flask, of capacity250cm 3 . 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 ISO1795.BSISO7780
41、:1998 BSI 04-1999 3 3.4.2 Latex Perform sampling in accordance with one of the methods specified in ISO123. 3.4.3 Compounded and vulcanized rubbers Cut out a50g sample, if necessary from more than one piece so that proper representation is achieved. 3.5 Procedure 3.5.1 Preparation of test portion 3.
42、5.1.1 Raw rubber From the sample taken in3.4.1, weigh out a10g test portion to the nearest10mg. 3.5.1.2 Latex Thoroughly mix the latex obtained in3.4.2, take a portion containing about10g of total solids, dry to constant mass as specified in ISO124, and cut into small pieces. 3.5.1.3 Compounded and
43、vulcanized rubbers From the sample taken in3.4.3, weigh out a10g test portion to the nearest10mg. 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 crucible(3.3.2) which is supported in the hole in the heat-r
44、esistant, 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. Heat the crucible and contents with a gentle gas flame unti
45、l a dry carbonaceous residue remains and then transfer the crucible to the muffle furnace(3.3.4) maintained at a temperature of550C 25C and heat until all carbon has been oxidized. Allow the crucible to cool in a desiccator, weigh it to determine the mass of ash and then, from a fine pipette, add an
46、 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 about550C for a few minutes. Repeat the treatment of the ash with the sulfuric acid, adding the acid as before from a fine pipette, heati
47、ng gently until fuming ceases, and then again at about550C for a few minutes. After cooling again to room temperature, add to the crucible8 parts by mass of sodium fluoroborate(3.2.1), up to a maximum of8g, to1 part by mass of the ash. Gently heat the crucible in a fume cupboard until fusion is comp
48、lete, and then more strongly until the molten material becomes clear, or until no further reaction takes place and any insoluble matter is dispersed in the melt. 3.5.2.2 Ashing the test portion in the presence of chlorine Place the test portion in a Kjeldahl flask(3.3.7), add10cm 3of sulfuric acid(3
49、.2.3) and heat moderately until the test portion has disintegrated. Carefully add5cm 3of nitric acid(3.2.4). If the reaction becomes too vigorous, cool the flask in a beaker of cold water and store at room temperature for at least two hours before reheating. As soon as the initial reaction has subsided, heat the mixture gently until the reaction has ceased, and then more strongly until the mixture darkens. Add a1cm 3portion of nitric acid and heat until darkening takes place again. Repeat the nitric acid addition and heating until the solutio
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