《ISO-7780-1998.pdf》由会员分享，可在线阅读，更多相关《ISO-7780-1998.pdf（16页珍藏版）》请在三一文库上搜索。
1、A Reference number ISO 7780:1998(E) INTERNATIONAL STANDARD ISO 7780 Second edition 1998-08-01 Rubber and rubber latices Determination of manganese content Sodium periodate photometric methods Caoutchoucs et latex de caoutchouc Dosage du manganse Mthodes photomtriques au periodate de sodium Copyright
2、 International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:38:18 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 7780:1998(E) ISO 1998 All rights reserved. Unless ot
3、herwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case postale 56 CH-1211 Genve 20
4、Switzerland Internetisoiso.ch Printed in Switzerland ii Foreword ISO (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
5、. Each member body interested in a subject for which a technical committee 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 Intern
6、ational Electrotechnical Commission (IEC) on all matters of electrotechnical 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 least 75 % of the member bo
7、dies casting a vote. International Standard ISO 7780 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products. This second edition cancels and replaces the first edition (ISO 7780:1987) which has been technically revised. Copyright International Organization for Standardization Prov
8、ided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:38:18 MDTNo reproduction or networking permitted without license from IHS -,-,- ISOISO 7780:1998(E) iii Introduction Manganese in certain forms is known to catalyse the oxidative breakdown
9、 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 taking place. However, there is always the possibility in the case of co
10、mpounded 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 between catalytically active and inactive forms, but no generally accepted
11、 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 synthetic rubbers, although it is widely accepted that its effect may be less se
12、vere 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 specified in this International Standard are applicable to all the commonly u
13、sed 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 through a fusion stage in order to obtain the manganese in soluble form; it is
14、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 shorter and suitable for raw rubbers, their corresponding latices, and rubb
15、er 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, ISO 6101-4:1997, Rubber Determination of metal content by atomic absorption spectrometry Part 4: Det
16、ermination 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 useful before choosing the most desirable method for the determination of manganese in raw and vulcanized rubbers and latices. Co
17、pyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:38:18 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright International Organization for Standard
18、ization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:38:18 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD ISOISO 7780:1998(E) 1 Rubber and rubber latices Determination of manganes
19、e content Sodium periodate photometric methods 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 the user to establis
20、h appropriate safety and health practices and to ensure compliance with any national regulatory conditions. 1Scope This International Standard specifies photometric methods for the determination of manganese, after oxidation with sodium periodate, in rubbers and rubber latices. Both methods contain
21、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 compounding ingredients whi
22、ch 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 %) of inert silicate fillers or any ingredient such as titanium dioxide which under th
23、e conditions of test will form an insoluble phosphate. 2Normative 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. All standards are subje
24、ct 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 Standards. ISO 123:1), Rubber
25、 latex Sampling. 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 (fritted) filters Porosity grading, classification and designation. _ 1) To be publish
26、ed. (Revision of ISO 123:1985) Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:38:18 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 7780:1998(E)
27、 ISO 2 3General method (for samples not affected by heavy loadings of fillers) 3.1Principle 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 por
28、tion 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 procedure, the manganese is oxidized to permanganate by boiling with sodi
29、um periodate. The manganese concentration is determined by spectro- photometric measurement at 525 nm. 3.2Reagents 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 f
30、luoroborate. If analytical grade is not available, prepare this reagent as follows. Dissolve 110 g of technical-grade sodium fluoroborate in 100 cm 3 of water warmed to about 35 C. After filtering through a filter paper, cool the solution to room temperature and add 100 cm 3 of 96 % (V/V) ethanol wh
31、ilst 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 about 50 C under vacuum. 3.2.2 Sodium periodate. 3.2.3 Sulfuric acid, r = 1,84 Mg/m 3. 3.2.4 Nitric a
32、cid, r = 1,42 Mg/m 3. 3.2.5 Stabilized water. To approximately 1 dm 3 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 cm 3 of distillate. Collect the rest of the distill
33、ate and store in a glass-stoppered bottle. 3.2.6 Potassium permanganate solution, approximately 30 g/dm 3. 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 perma
34、nganate (KMnO4) into a small beaker and dissolve in water containing 2 cm 3 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 cm 3 volumetric flask and dilute to the mark with water. b) Weigh 0,77
35、0 g of manganese sulfate (MnSO4.H2O) into a small beaker and dissolve in water containing 2 cm 3 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 cm 3 of either solution a)
36、 or solution b) into a second 500 cm3 volumetric flask and again dilute to the mark with water. 1 cm 3 of this standard solution contains 0,01 mg of manganese. Prepare the solution just before use. Copyright International Organization for Standardization Provided by IHS under license with ISO Licens
37、ee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:38:18 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO ISO 7780:1998(E) 3 3.2.8 Hydrogen peroxide, 30 % (V/V) solution in water. 3.2.9 Hydrofluoric acid, r = 1,12 Mg/m 3. 3.3Apparatus Ordinary laborat
38、ory apparatus, plus the following: 3.3.1 Photometer or spectrophotometer, capable of measuring absorbance at approximately 525 nm, and matched cells. 3.3.2 Platinum crucible (30 cm 3 nominal capacity is suitable). 3.3.3 Heat-resistant, thermally insulating board, approximately 100 mm square and 6 mm
39、 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 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 ga
40、s burner with sandbath. 3.3.7 Kjeldahl flask, of capacity 250 cm 3. 3.3.8 Platinum rod, as stirrer. 3.4Sampling 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. 3.4.2 Latex Perform samplin
41、g 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. 3.5Procedure 3.5.1 Preparation of test portion 3.5.1.1 Raw rubber From the sample taken in 3.4
42、.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, and cut into small pieces. Copyright International Organization for Standardization Pr
43、ovided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:38:18 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 7780:1998(E) ISO 4 3.5.1.3 Compounded and vulcanized rubbers From the sample taken in 3.4.3, weigh out
44、 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 crucible (3.3.2) which is supported in the hole in the heat-resistant, thermally insulating board (3.3.3). Start th
45、e 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 until a dry carbonaceous residue remains and then transfe
46、r 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 determine the mass of ash and then, from a fine pipette, add an amount of sulfuric acid (3.2.3) drop by drop rou
47、nd 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
48、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 (3.2.1), up to a maximum of 8 g, to 1 part by mass of the ash. Gently heat the crucible in a fume cupboard until fusion is complete, 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 Kjeld