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1、BRITISH STANDARD BS ISO 188:1998 BS 903-A19: 1998 Incorporating Corrigendum No. 1 Rubber, vulcanized or thermoplastic Accelerated ageing and heat resistance tests ICS 83.060 ? Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:49:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 188:1998 T
2、his British 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 June 1998 BSI 26 November 2003 ISBN 0 580 29347 5 National foreword This British Standard reproduces ve
3、rbatim ISO 188:1998 and implements it as the UK national standard, including Corrigendum August 2003. It supersedes BS 903-A19:1986 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee PRI/22, Physical testing of rubber, which has the responsibility to: ai
4、d enquirers to understand the text; present to 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 organizat
5、ions represented on this committee can be obtained on request to its secretary. Additional information It is felt to be axiomatic that Clause5c) encompasses the recommendation that rubbers having different amounts of antioxidant should not be aged together. In 10.2.1, and Table 1, Table 2, Table 3,
6、Table 4, Table 5, Table 6, Table 7 and Table 8, reference is made to a polymer type of EACM, which is, unfortunately, not defined. It is thought this is probably a reference to an ethyl acrylate and ethylene copolymer, which is symbolized in ISO 1629:1995 as AEM. For the removal of doubt, 10.2.5 sho
7、uld be understood as referring to the “mean values of the changes in properties as defined in Clause9”. It is to be noted that the precision tables in Clause10 include some values which do not conform to normal expectations, such as, for example, the extremely high values for percentage repeatabilit
8、y and reproducibility for “EACM” type rubbers aged at low air speeds compared with the same rubber type aged at high air speeds, and also cases where the percentage reproducibility (R), is actually lower than the percentage repeatability (r), such as in Table 1, Table 2, Table 3, Table 4, Table 6 an
9、d Table 7. For these reasons it is felt that it may be unwise to place too much reliance on the values in these precision tables, although the information does reveal that there can be a great deal of variability in test results on different polymers between laboratories. Cross-references The Britis
10、h Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Onlin
11、e. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to iv, pages 1 to 9 and a back cover. The BSI cop
12、yright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No.DateComments 14802 Corrigendum No. 1 26 November 2003Changes to Table 7 and 8 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:49:06 GMT+00:00 2006, Uncontrolled
13、 Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:49:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 188:1998 ii BSI 26 November 2003 Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodie
14、s). 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 represented on that committee. International organizations, governmental and n
15、on-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 adopted by the technical committees are circulated to the member bodie
16、s for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 188 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 2, Physical and degradation tests. This third editi
17、on cancels and replaces the second edition (ISO 188:1982), which has been technically revised. Annex A of this International Standard is for information only. Descriptors: Rubber, vulcanized rubber, tests, ageing tests (materials), high temperature tests. Licensed Copy: sheffieldun sheffieldun, na,
18、Mon Nov 27 07:49:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 188:1998 BSI 26 November 2003 iii Introduction Accelerated ageing and heat resistance tests are designed to estimate the relative resistance of rubber to deterioration with the passage of time. For this purpose, the rubber is subj
19、ected to controlled deteriorating influences for definite periods, after which appropriate properties are measured and compared with the corresponding properties of the unaged rubber: The purpose of the accelerated ageing test may be to assess the deterioration of the rubber a) either during prolong
20、ed periods at normal or elevated temperatures in air; b) or during prolonged periods at elevated temperatures and at elevated oxygen pressure. In accelerated ageing, the rubber is subjected to a test environment intended to produce the effect of natural ageing in a shorter time. In the case of heat
21、resistance tests, the rubber is subjected to prolonged periods at the same temperature as that which it will experience in service. Three types of method are given in this International Standard, namely an air-oven method using a low air speed, an air-oven method using forced air ventilation and an
22、oxygen pressure method. The selection of the time, temperature and atmosphere to which the test pieces are exposed and the type of oven to use will depend on the purpose of the test and the type of polymer. In the air-oven methods, deterioration is accelerated by raising the temperature and, in the
23、oxygen pressure method, by increasing the oxygen concentration and the temperature. The degree of acceleration thus produced varies from one rubber to another and from one property to another. Degradation can also be accelerated by air speed. Consequently, ageing with different ovens can give differ
24、ent results. Consequences of this are: a) Accelerated ageing does not truly reproduce under all circumstances the changes produced by natural ageing. b) Accelerated ageing sometimes fails to indicate accurately the relative natural or service life of different rubbers; thus, ageing at temperatures g
25、reatly above ambient or service temperatures may tend to equalize the apparent life of rubbers which deteriorate at different rates in storage or service. Ageing at one or more intermediate temperatures is useful in assessing the reliability of accelerated ageing at high temperatures. c) Accelerated
26、 ageing tests involving different properties may not give agreement in assessing the relative lives of different rubbers and may even arrange them in different orders of merit. Therefore, deterioration should be measured by the changes in property or properties which are of practical importance, pro
27、vided that they can be measured reasonably accurately. Air-oven and oxygen pressure ageing should not be used to simulate natural ageing which occurs in the presence of either light or ozone when the rubbers are stretched. To estimate lifetime or maximum temperature of use, tests can be performed at
28、 several temperatures and the results can be evaluated by using an Arrhenius plot. This method is described in ISO 11346. Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:49:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:49:0
29、6 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 188:1998 BSI 26 November 2003 1 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 r
30、esponsibility 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 accelerated ageing or heat resistance tests on vulcanized or thermoplastic rubbers. The methods are: Method A
31、: air-oven method using a cell-type oven or cabinet oven with low air speed and a ventilation of 3 to 10 changes per hour; Method B: air-oven method using a cabinet oven with forced air circulation by means of a fan and a ventilation of 3 to 10 changes per hour; and Method C: oxygen pressure method
32、at 2,1 MPa and 70 C. 2 Normative references The following standards contain 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 subject to revision, and parties to agr
33、eements 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 37:1994 , Rubber, vulcanized or thermoplastic De
34、termination of tensile stress-strain properties. ISO 48:1994, Rubber, vulcanized or thermoplastic Determination of hardness (hardness between 10 IRHD and 100 IRHD). ISO 471:1995, Rubber Temperatures, humidities and times for conditioning and testing. ISO 11346:1997, Rubber, vulcanized or thermoplast
35、ic Estimation of life-time and maximum temperature of use from an Arrhenius plot. 3 Principle Test pieces are subjected to controlled deterioration by air at an elevated temperature and at atmospheric pressure (for 3.1 and 3.2) or at an elevated temperature and an elevated oxygen pressure (for 3.3),
36、 after which the physical properties are measured and compared with those of unaged test pieces. The physical properties concerned in the service application should be used to determine the degree of deterioration but, in the absence of any indication of these properties, it is recommended that tens
37、ile strength, stress at intermediate elongation, elongation at break (in accordance with ISO 37) and hardness (in accordance with ISO 48) be measured. 3.1 Accelerated ageing by heating in air In this method, the oxygen concentration is low and, if oxidation is rapid, oxygen may not diffuse into the
38、rubber quickly enough to maintain uniform oxidation. This ageing method is therefore liable to give misleading results with poor-ageing rubbers when the normal thickness specified in the International Standard appropriate to the test method is used. 3.2 Heat resistance test In this method, the test
39、pieces are subjected to the same temperature as they would experience in service and, after definite periods, appropriate properties are measured and compared with those of the unaged rubber. 3.3 Accelerated ageing by heating in oxygen In this method, the increased oxygen concentration promotes rapi
40、d diffusion and so helps to ensure uniform oxidation. On the other hand, the artificial promotion of oxidation may overemphasize oxidative changes relative to those caused by after-vulcanization, e.g. reversion, so that the total effect may not resemble that of natural ageing. Licensed Copy: sheffie
41、ldun sheffieldun, na, Mon Nov 27 07:49:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 188:1998 2 BSI 26 November 2003 4 Apparatus 4.1 Air oven (for 3.1 and 3.2) To achieve a good precision when doing ageing and heat resistance tests, it is very important to keep the temperature uniform and sta
42、ble during the test and to verify that the oven used is within the temperature limits with regard to time and space. Increasing the air speed in the oven improves temperature homogeneity. However, air circulation in the oven and ventilation influence the ageing results. With a low air speed, accumul
43、ation of degradation products and of evaporated ingredients, as well as oxygen depletion, can take place. A high air speed increases the rate of deterioration, due to increased oxidation and volatilization of plasticizers and antioxidants. The oven shall be of such a size that the total volume of th
44、e test pieces does not exceed 10 % of the free space in the oven. Provision shall be made for suspending test pieces so that they are at least 10 mm from each other and, in cabinet ovens and ovens with forced air circulation, at least 50 mm from the sides of the oven. The temperature of the oven sha
45、ll be controlled so that the temperature of the test pieces is kept within the specified tolerance for the specified ageing temperature (see Clause 7) for the whole ageing period. A temperature sensor shall be placed inside the heating chamber to record the actual ageing temperature. No copper or co
46、pper alloys shall be used in the construction of the heating chamber. For the ovens specified in 4.1.1 and 4.1.2, provision shall be made for a slow flow of air through the oven of not less than three and not more than ten air changes per hour. The air speed shall depend on the air change rate only,
47、 and no fans are allowed inside the heating chamber. Care shall also be taken to ensure that the incoming air is heated to within 1 C of the temperature of the oven before coming in contact with the test pieces. The ventilation (or air change rate) can be determined by measuring the volume of the ov
48、en chamber and the flow of air through the chamber. 4.1.1 Cell-type oven, consisting of one or more vertical cylindrical cells having a minimum height of 300 mm. The cells shall be surrounded by a thermostatically controlled good-heat-transfer medium (aluminium block, liquid bath or saturated vapour
49、). Air passing through one cell shall not enter other cells. 4.1.2 Cabinet oven, comprising a single chamber without separating walls. 4.1.3 Oven with forced air circulation, with an air speed of 0,5 m/s to 1,5 m/s. The air flow through the heating chamber shall be as uniform and laminar as possible. The test pieces shall be placed with the smallest surface facing towards the air flow direction to avoid disturbing the air flow. The air shall be changed at a rate of not less than three and not mor