1、BSI Standards PublicationBS ISO 11346:2014Rubber, vulcanized orthermoplastic Estimationof life-time and maximumtemperature of useBS ISO 11346:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 11346:2014. The UK participation in its preparation was entrusted
2、to TechnicalCommittee PRI/22, Physical testing of rubber.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The B
3、ritish Standards Institution 2014.Published by BSI Standards Limited 2014ISBN 978 0 580 81992 6 ICS 83.060 Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 Nov
4、ember 2014.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e d ISO 2014Rubber, vulcanized or thermoplastic Estimation of life-time and maximum temperature of useCaoutchouc vulcanis ou thermoplastique Estimation de la dure de vie et de la temprature maximale dutilisationINTERNA
5、TIONAL STANDARDISO 11346Third edition 2014-12-01Reference number ISO 11346:2014(E)BS ISO 11346:2014ISO 11346:2014(E)ii ISO 2014 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2014All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise
6、 in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase p
7、ostale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 11346:2014ISO 11346:2014(E)Contents PageForeword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Principle 15 Selection of tests
8、and ageing oven 26 Selection of threshold value . 27 Test pieces . 28 Exposure temperatures . 39 Exposure times . 310 Procedure. 311 Expression of results 411.1 Arrhenius procedure . 411.2 WLF procedure . 611.3 Limitations 812 Test report . 8Bibliography .10 ISO 2014 All rights reserved iiiBS ISO 11
9、346:2014ISO 11346:2014(E)ForewordISO (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
10、 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 International Electrotechnical Commiss
11、ion (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents shou
12、ld be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). 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 responsible for id
13、entifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document is information given for the conv
14、enience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword
15、 - Supplementary informationThe committee responsible for this document is ISO/TC 45, Rubber and rubber products, Subcommittee SC 2, Testing and analysis.This third edition cancels and replaces the second edition (ISO 11346:2004), of which it constitutes a minor revision.iv ISO 2014 All rights reser
16、vedBS ISO 11346:2014ISO 11346:2014(E)IntroductionThe rate of a chemical reaction normally increases with increase in temperature. By exposing test pieces to a series of elevated temperatures, the relation between the reaction rate of degradative mechanisms and temperature can be deduced. Estimates c
17、an then be made by extrapolation of the degree of degradation after a given time at a given temperature or the time at a given temperature to reach a given degree of degradation.The reaction rate/temperature relationship can often be represented by the Arrhenius equation. The reaction rate at any gi
18、ven temperature is obtained from the change in the value of a selected property with exposure time at that temperature. The reaction rate can be represented by the time to a particular degree of degradation (threshold value) and this might be the only measure to use if the property/temperature relat
19、ion is complex.The Arrhenius approach is only suitable for chemical degradation reactions and might give wrong results for tests where physical (viscoelastic) changes cannot easily be separated from chemical changes.An alternative approach for rubbers is to use the Williams Landel Ferry (WLF) equati
20、on. This equation performs a time/temperature transformation and no assumptions are made as to the form of the property/time relation at any temperature. Hence, in principle, it can be applied to any physical property, including set and relaxation, or where the property/time relation is complex. Fur
21、ther explanation of the use of the WLF equation can be found in the literature.1During the preparation of this International Standard, account was taken of the contents of ISO 25782and IEC 60216.3 ISO 2014 All rights reserved vBS ISO 11346:2014ISO 11346:2014 (E)BS ISO 11346:2014Rubber, vulcanized or
22、 thermoplastic Estimation of life-time and maximum temperature of use1 ScopeThis International Standard specifies the principles and procedures for estimating the thermal endurance of rubbers from the results of exposure to elevated temperatures for long periods.Two approaches are specified (see Int
23、roduction): one using the Arrhenius relation; the other using the WLF equation.In this International Standard, the estimation of thermal endurance is based solely on the change in selected properties resulting from periods of exposure to elevated temperatures. The various properties of rubbers chang
24、e at different rates on thermal ageing, hence comparisons between different rubbers can only be made using the same properties.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated referenc
25、es, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 188, Rubber, vulcanized or thermoplastic Accelerated ageing and heat resistance testsISO 23529, Rubber General procedures for preparing and conditioning te
26、st pieces for physical test methods3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1life-timetime at which the material under test has reached the specified threshold value for the property tested at the temperature of use3.2maximum temperature o
27、f usetemperature at which the material under test has reached the specified threshold value for the property tested after the specified time3.3threshold valueparticular degree of degradation which is taken as the maximum acceptable for the property being testedNote 1 to entry: The time to reach the
28、threshold value can be used to represent the reaction rate4 PrincipleAt a chosen test temperature, the variations in the numerical value of a chosen property, for example a mechanical or viscoelastic property, are determined as a function of time.INTERNATIONAL STANDARD ISO 11346:2014(E) ISO 2014 All
29、 rights reserved 1BS ISO 11346:2014ISO 11346:2014(E)The testing is continued until the relevant threshold value of that property has been exceeded.Further tests are carried out at least two other temperatures.For the Arrhenius procedure, the measures of the reaction rates obtained are plotted logari
30、thmically as a function of the reciprocal of temperature and the straight line obtained is extrapolated back or interpolated to the temperature of use.For the WLF procedure, the shift constants are calculated and used to transpose the property/time relation to the temperature of use.5 Selection of t
31、ests and ageing ovenThe tests chosen should preferably relate to properties which are likely to be of significance in practice. Wherever possible, use shall be made of methods of test specified in International Standards.For general evaluations, hardness, and tensile stress-strain properties are com
32、monly used, but stress relaxation or set in compression, for example, is desirable for sealing applications.For the ageing of test pieces, a circulating-air oven meeting the requirements of ISO 188 shall be used.6 Selection of threshold valueThe threshold value shall be chosen as the degree of degra
33、dation that is the maximum acceptable for the property being tested and the end use. Commonly, 50 % of the initial value of the property is chosen.The test should normally be continued for a long enough period for the threshold value to be reached. Although it is possible to extrapolate to greater d
34、egrees of degradation, this is not recommended.7 Test pieces7.1 The dimensions and method of preparation of the test pieces shall be in accordance with the relevant test method standard.7.2 The minimum total number, n, of test pieces required for a destructive test method depends on: the number of t
35、est pieces, a, required for a single test in accordance with the test method standard; the number of different ageing periods, b, necessary to obtain the property/time relationship at any one exposure temperature; the number of exposure temperatures, c.The minimum number of test pieces required is g
36、iven in Formula (1):nabc a=+ (1)It is recommended that additional test pieces are aged at each temperature in case problems occur after several weeks, months or years of ageing, or an extra exposure temperature is required to improve precision.The minimum number of test pieces required for a non-des
37、tructive test method is normally given in Formula (2):nac= (2)When measuring compression set, tension set, and relaxation, the tests are preferably done on the same test pieces, at the different times, to reduce the number of test pieces needed. This also reduces variations in the test results.2 ISO
38、 2014 All rights reservedBS ISO 11346:2014ISO 11346:2014(E)It might be necessary, in addition, to carry out trial runs to determine the exposure temperatures and the number of test points required at each temperature.NOTE While it is possible to reduce the number of test pieces for each test from th
39、at given in the test method standard to economize on testing, extrapolation of the results requires the best possible precision and in some circumstances it might be advisable to increase the number of test pieces.8 Exposure temperaturesSelection of the exposure temperatures involves knowing beforeh
40、and the approximate ageing characteristics of the material under test. With no previous knowledge of the material, exploratory tests will have to be carried out. This information will assist in selecting the exposure temperatures best suited for the evaluation of the material.Test pieces shall be ag
41、ed at not fewer than three temperatures covering a range adequate to establish the life-time estimation by extrapolation with the required degree of accuracy. The lowest exposure temperature shall be chosen so that the time taken to reach the threshold value is at least 1 000 h. Likewise, the highes
42、t temperature shall be chosen so that the time taken to reach the threshold value is not shorter than 100 h. The temperatures used should preferably be standard test temperatures taken from ISO 23529.NOTE To obtain an estimate of the life-time with adequate precision will often require more than thr
43、ee test temperatures.9 Exposure timesThe properties chosen to measure the reaction rate shall be tested after each of at least five different exposure times at each temperature, but more exposure times will normally be needed if the shape of the property/time curve is to be established.The exposure
44、times shall be such as to enable the property chosen to measure the reaction rate to be characterized adequately. For thermo-oxidative ageing, a linear progression will be satisfactory in many cases. For physical relaxation, a logarithmic progression would be more appropriate. The requirements conce
45、rning minimum exposure times in Clause 8 shall be respected.10 ProcedureMeasure the selected properties using unaged sets of test pieces conditioned as required by the relevant test method standards.Place the required number of test pieces in each of the ovens maintained at the selected temperatures
46、.At the end of each exposure time, condition the test pieces to be examined as required by the relevant test method standard and measure the selected properties.Continue this procedure until the required number of sets of test pieces have been tested. ISO 2014 All rights reserved 3BS ISO 11346:2014I
47、SO 11346:2014(E)11 Expression of results11.1 Arrhenius procedureThe Arrhenius relation can be written in Formula (3):lnKT BERT()= (3)whereK(T) is the reaction rate (min1);B is a constant;E is the activation energy (J/mol);R is the gas constant (8,314 J/mol K);T is the absolute temperature (K).The st
48、age the reaction has reached is given by the relation in Formula (4):Ft KT tx() ()= (4)whereFx(t) is a function describing the stage, x, the reaction has reached;t is the reaction time (min).There will be different reaction rates, K(T), corresponding to different temperatures, T.For each exposure te
49、mperature, plot the results for each property against time. For each plot, determine the reaction rate.Often, a convenient measure of the reaction rate is the time for the property to reach the threshold value, determined by interpolation as illustrated in Figure 1.NOTE The ideal measure of the reaction rate would be the slope of the property-time plot, but this is rarely linear i.e. Fx(t) is rarely linear. It might be possible to fit a convenient relationship to the data or to obtain a convenient plot by plotting on a logarithmic
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