1、 Reference number ISO/TR 7620:2005(E) ISO 2005TECHNICAL REPORT ISO/TR 7620 Second edition 2005-05-15 Rubber materials Chemical resistance Matriaux en caoutchouc Rsistance chimique ISO/TR 7620:2005(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing pol
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6、 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2005 All rights reservedISO/TR 7620:2005(E) ISO 2005 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope 1 2 Types of chemical and physical change 1 3 Rubber polymers. 2 4 Chemicals 3 5
7、 Effect of service conditions . 3 6 Criteria applied for the ranking of chemical resistance 3 7 Chemical resistance of rubber materials 4 8 Methods for the evaluation of chemical resistance 5 9 Chemical resistance . 8 Annex A (informative) Effect of compounding variations on chemical resistance . 32
8、 Annex B (informative) References in Table 2 34 Annex C (informative) References in Table 3 35 ISO/TR 7620:2005(E) iv ISO 2005 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of
9、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 represented on that committee. International organizations, governmental and non-governmental,
10、 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. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main t
11、ask of technical committees is to prepare International Standards. 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 bodies casting a vote. In exc
12、eptional circumstances, when a technical committee has collected data of a different kind from that which is normally published as an International Standard (“state of the art”, for example), it may decide by a simple majority vote of its participating members to publish a Technical Report. A Techni
13、cal Report is entirely informative in nature and does not have to be reviewed until the data it provides are considered to be no longer valid or useful. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held respons
14、ible for identifying any or all such patent rights. ISO/TR 7620 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 4, Products (other than hoses). This second edition cancels and replaces the first edition (ISO/TR 7620:1986), which has been technically revised
15、. ISO/TR 7620:2005(E) ISO 2005 All rights reserved vIntroduction A wide range of rubber products are used in contact with liquids and other chemicals, in some cases throughout their service life, and thus require suitably resistant rubber formulations. Rubber hoses are used to convey a range of flui
16、ds from hot water to fuels, conveyor belting may have to carry aggressive slurries, seals and gaskets are installed to prevent leakage of gases and liquids, rubber-covered rollers manipulate webs as diverse as printing inks, paper pulp and textiles, and rubber-lined tanks are used to store industria
17、l chemicals, including corrosive alkalis and acids, for prolonged periods without risk of contamination. Other products, ranging from tyres to flexible roofing membranes, are exposed to rainfall and atmospheric pollutants. It is essential a suitably resistant rubber be used because contact with a ch
18、emical, whether in the form of a liquid or gas, can lead to deterioration of properties through swelling, extraction of additives and polymer degradation. The rate and extent of such attack depends not only on the chemical composition of the rubber polymer and other compounding ingredients but also
19、on the nature of the liquid or gas, its concentration, temperature, pressure and the duration of contact. The thickness of the rubber must be taken into account since the time of penetration of the swelling fluid is dependent on product dimensions, and the bulk of a very thick rubber product may rem
20、ain unaffected for the whole of the projected service life. This document has been prepared to assist the selection or evaluation of rubber for chemical resistance. It includes an extensive classification of resistance based on information in over 20 sources and involving about 400 chemicals and up
21、to 25 types of rubber. TECHNICAL REPORT ISO/TR 7620:2005(E) ISO 2005 All rights reserved 1Rubber materials Chemical resistance 1 Scope This Technical Report describes a classification system for the reporting and tabulation of the chemical resistance of rubber materials. It also provide guidance on
22、the testing and evaluation of rubber with particular reference to test chemicals described in a number of ISO standards. This document gives guidance on the behaviour of rubber in contact with chemicals such as aggressive gases and fluids, e.g. acids, alkalis, aqueous solutions, oil and solvents. Th
23、e information given in this document is based on the practical experience of manufacturers and users of rubber materials. Unless there is prior knowledge or experience of the application, a selection based on the tables should always be confirmed by tests on the proposed rubber compounds using the a
24、ctual product under the appropriate service conditions. In such tests, attention should also be given to the possibility of the rubber material contaminating the liquid or gas. 2 Types of chemical and physical change 2.1 Physical penetration Physical penetration and absorption of an agent into a rub
25、ber material, for instance of isooctane into SBR, may occur. These phenomena cause swelling of the rubber, sometimes combined with extraction of soluble material from the rubber. If the absorbed fluid is removed, for instance by drying, most of the physical properties return to their original level.
26、 If the antidegradants in the rubber are extracted, a loss in ageing resistance may result. If extender oil or plasticizer is extracted in quantity, the rubber will harden and shrink. Gases may penetrate throughout the thickness of thin-walled products without any swelling or damage to the rubber. G
27、as permeability falls outside the scope of this document but may need to be considered when selecting a rubber material. 2.2 Chemical attack The effect of reactive chemicals on rubber can in most cases be referred to one or more of the following categories: a) Hydrolysis. This is a chemical reaction
28、 between water and the rubber polymer, especially under acid and alkaline conditions, which results in degradation of physical properties. At the same time, swelling could take place but this is not always the case. A typical example is the attack of hot water on polyester urethanes. b) Oxidation. A
29、ll organic materials are more or less sensitive to oxidation. The oxidation is often associated with chemical and thermal processes. This attack will result in degradation of physical properties. Usually, the tensile strength will decrease, but hardness and elongation at break can either increase or
30、 decrease depending on the rubber type and the environment. If liquid oxidizing media are used, oxidation may be combined with swelling. A typical example of the latter is the effect of nitric acid on SBR and NBR. As with most other forms of chemical attack, the rate of oxidation increases with temp
31、erature. ISO/TR 7620:2005(E) 2 ISO 2005 All rights reservedNOTE Thermal or thermal-oxidative ageing may be the main consequence of exposure to some chemically inert fluids at high temperatures. c) Specific effects. Examples are those due to reaction with chlorine, bromine, ozone, etc. Attack by thes
32、e chemicals is usually confined to the surface of the rubber, but can become progressively deeper with time. Hardened surfaces can crack due to thermal or physical movement. 3 Rubber polymers The rubber materials considered in this document are based on the following rubber polymers: Rubber polymer
33、Symbol Natural rubber NR Butadiene rubber BR Isoprene rubber IR Styrene-butadiene rubber SBR Isobutene-isoprene rubber (butyl rubber) IIR Bromo- or chloro-isobutene-isoprene (halobutyl) rubber BIIR/CIIR Ethylene-propylene-diene rubber (terpolymer) EPDM Ethylene-propylene rubber (copolymer) EPM Acryl
34、onitrile-butadiene rubber NBR Hydrogenated acrylonitrile-butadiene rubber HNBR Chloroprene rubber CR Chloropolyethylene rubber CM Chlorosulfonyl-polyethylene rubber CSM Acrylate rubber (copolymer) ACM Ethylene-acrylate rubber (ethylene acrylic rubber) AEM Ethylene-vinylacetate rubber EVM Epichlorohy
35、drin rubber (homopolymer) CO Epichlorohydrin rubber (copolymer) ECO Polyester urethane rubber AU Polyether urethane rubber EU Polysulfide rubber T Silicone rubber MQ Fluorinated silicone rubber FMQ Fluorinated rubber FKM About half of the rubbers in the list are marketed as “oil-resistant”. Care sho
36、uld be exercised when using this term for chemical resistance because “oil-resistant” is usually defined in terms of resistance to swelling by mineral oils (or, in test terms, to swelling in one of the ISO 1817 reference oils). It should be appreciated that a rubber resistant to such oils is not nec
37、essarily resistant to oils of other types. It must also be observed that the classification of chemical resistance is also directly dependent on the compounding variations (see Annex A). ISO/TR 7620:2005(E) ISO 2005 All rights reserved 3Thermoplastic rubbers have not been included because of insuffi
38、cient experience and test data. Consult suppliers for information on chemical resistance. 4 Chemicals The chemicals listed in this document are thought to be representative of those coming into contact with rubber, and as far as possible at least one member or each class of commonly used organic che
39、mical has been included. Proprietary materials have not been included except those representative of a particular class of service or industrial fluids. The classification is for normal technically pure chemicals. The same performance may not necessarily apply to commercial chemicals even of broadly
40、 similar composition because of any effect contaminants or minor active constituents may have. Several commercial chemicals for example may contain trace quantities of oxidizing agents or pro-oxidants. Detergents provide another example: these contain chemically active materials and the type and lev
41、el will vary from supplier to supplier. It should also be noted that mineral oils and fuels vary appreciably in composition even when supplied to a recognized specification. The chemical composition governs the extent to which a rubber can swell, whereas the oil viscosity governs the rate of penetra
42、tion into the rubber. A viscous oil diffuses more slowly than a less viscous one. Common chemical names are used in this document. 5 Effect of service conditions The amount of change which may be tolerated in a rubber material depends to some extent on the application and whether it is static or dyn
43、amic. If, for instance, an O-ring is used in a dynamic application, the permissible volume change or shrinkage has to be much lower than in a static application. Several chemicals will only attack the rubber at its surface and, in the case of ozone, a tensile strain must be present for cracking (the
44、 main form of degradation with ozone) to occur. The service temperature is also important because an increase will normally raise the rate of penetration of a fluid and raise the level of swelling. 6 Criteria applied for the ranking of chemical resistance As criteria for the chemical resistance in t
45、his document the degradation of the physical properties and the change in volume are taken, and it is presumed that standard 2 mm thick test pieces are completely submerged in the medium. The data referred to for gases and organic solvents are, as far as possible, based on 4 weeks at 23 C, for oils
46、14 days at 100 C and for aqueous solutions 4 weeks at 70 C if no other conditions are stated. If no temperature is reported, this is unknown and therefore caution must be exercised when assessing the level of resistance. In many cases, no time is reported in the references. When a concentration is l
47、isted, it is in aqueous solution. Resistance is divided into four classes as defined in Table 1. For chemicals absorbed by the rubber material, resistance is classified primarily according to the extent of volume swell (column B of Table 1) and this criterion applies as long as the hardness change a
48、ccompanying the swelling is lower than the change given in column C for the same class. If the hardness decrease is higher than that indicated for a given volume swel, the material is classified by hardness change. For chemicals which do not cause swelling, shrinkage or a significant hardness change
49、, the material is classified in terms of the effect on other properties using the descriptions in column D of Table 1. These properties will include tensile stress/strain characteristics, especially in the case of chemicals able to penetrate into the bulk of the rubber, and surface changes such as crack appearance, crazing, erosion and discoloration in the case of chemicals attacking at the rubber surface. The descriptions used in column D should not be regarded as being equivalent to the changes given in columns B andC. For most applications, a
