1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 188:2011Rubber, vulcanized orthermoplastic Acceleratedageing and heat resistancetestsBS ISO 188:2011 BRITISH STANDARDNational forewordThis British Standard is the UK imple
2、mentation of ISO 188:2011. Itsupersedes BS ISO 188:2007 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee PRI/22, Physical testing of rubber.A list of organizations represented on this committee can beobtained on request to its secretary.This publication
3、does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2011ISBN 978 0 580 73712 1ICS 83.060Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of
4、theStandards Policy and Strategy Committee on 31 October 2011.Amendments issued since publicationDate Text affectedBS ISO 188:2011Reference numberISO 188:2011(E)ISO 2011INTERNATIONAL STANDARD ISO188Fifth edition2011-10-01Rubber, vulcanized or thermoplastic Accelerated ageing and heat resistance test
5、s Caoutchouc vulcanis ou thermoplastique Essais de rsistance au vieillissement acclr et la chaleur BS ISO 188:2011ISO 188:2011(E) COPYRIGHT PROTECTED DOCUMENT ISO 2011 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any mea
6、ns, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyr
7、ightiso.org Web www.iso.org Published in Switzerland ii ISO 2011 All rights reservedBS ISO 188:2011ISO 188:2011(E) ISO 2011 All rights reserved iiiContents Page Foreword iv Introduction . v 1 Scope 1 2 Normative references 1 3 Principle . 1 4 Apparatus . 2 5 Calibration 4 6 Test pieces . 4 7 Time in
8、terval between vulcanization and testing . 5 8 Ageing conditions (duration and temperature) 5 9 Procedure . 6 10 Expression of results 6 11 Precision 6 12 Test report 7 Annex A (informative) Determination of the air speed in ovens with forced air circulation . 8 Annex B (informative) Precision 10 An
9、nex C (informative) Guidance for using precision results . 17 Annex D (normative) Calibration schedule 18 Bibliography 20 BS ISO 188:2011ISO 188:2011(E) iv ISO 2011 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bo
10、dies (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 committee has been established has the right to be represented on that committee. International organizatio
11、ns, 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 electrotechnical standardization. International Standards are drafted in accordance with the rules given in the
12、ISO/IEC Directives, Part 2. The main task 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 th
13、e member bodies casting a vote. 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 identifying any or all such patent rights. ISO 188 was prepared by Technical Committee ISO/TC 45, Rubber and rub
14、ber products, Subcommittee SC 2, Testing and analysis. This fifth edition cancels and replaces the fourth edition (ISO 188:2007), of which it constitutes a minor revision to include an annex (Annex D) specifying a calibration schedule for the apparatus used. BS ISO 188:2011ISO 188:2011(E) ISO 2011 A
15、ll rights reserved vIntroduction 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 subjected to controlled deteriorating influences for definite periods, after which appro
16、priate properties are measured and compared with the corresponding properties of the unaged rubber. 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 resistance tests, the rubber is subjected t
17、o prolonged periods at the same temperature as that which it will experience in service. Two types of method are given in this International Standard, namely an air-oven method using a low air speed and an air-oven method using forced air ventilation for a high air speed. The selection of the time,
18、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 air-oven methods, deterioration is accelerated by raising the temperature. The degree of acceleration thus produced varies from one rubber to
19、 another and from one property to another. Degradation can also be accelerated by air speed. Consequently, ageing with different ovens can give different results. Consequences of these effects are: a) Accelerated ageing does not truly reproduce under all circumstances the changes produced by natural
20、 ageing. b) Accelerated ageing sometimes fails to indicate accurately the relative natural or service life of different rubbers; thus, ageing at temperatures greatly above ambient or service temperatures may tend to equalize the apparent lives of rubbers, which deteriorate at different rates in stor
21、age or service. Ageing at one or more intermediate temperatures is useful in assessing the reliability of accelerated ageing at high temperatures. c) Accelerated ageing tests involving different properties may not give agreement in assessing the relative lives of different rubbers and may even arran
22、ge them in different orders of merit. Therefore, deterioration should be measured by the changes in property or properties which are of practical importance, provided that they can be measured reasonably accurately. Air-oven ageing should not be used to simulate natural ageing which occurs in the pr
23、esence of either light or ozone when the rubbers are stretched. To estimate lifetime or maximum temperature of use, tests can be performed at several temperatures and the results can be evaluated by using an Arrhenius plot or the Williams Landel Ferry (WLF) equation as described in ISO 113462. BS IS
24、O 188:2011BS ISO 188:2011INTERNATIONAL STANDARD ISO 188:2011(E) ISO 2011 All rights reserved 1Rubber, vulcanized or thermoplastic Accelerated ageing and heat resistance tests WARNING Persons using this International Standard should be familiar with normal laboratory practice. This standard does not
25、purport to address all of the safety problems, if any, associated with its use. It is the responsibility 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
26、 or heat resistance tests on vulcanized or thermoplastic rubbers. Two methods are given: Method A: 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 me
27、ans of a fan and a ventilation of 3 to 10 changes per hour. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (i
28、ncluding any amendments) applies. ISO 37, Rubber, vulcanized or thermoplastic Determination of tensile stress-strain properties ISO 48, Rubber, vulcanized or thermoplastic Determination of hardness (hardness between 10 IRHD and 100 IRHD) ISO 18899:2004, Rubber Guide to the calibration of test equipm
29、ent ISO 23529, Rubber General procedures for preparing and conditioning test pieces for physical test methods 3 Principle 3.1 General Test pieces are subjected to controlled deterioration by air at an elevated temperature and at atmospheric pressure, after which specified properties are measured and
30、 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 tensile strength, stress at intermediate elongation, elon
31、gation at break (in accordance with ISO 37) and hardness (in accordance with ISO 48) be measured. BS ISO 188:2011ISO 188:2011(E) 2 ISO 2011 All rights reserved3.2 Accelerated ageing by heating in air In this method, the test pieces are subjected to a higher temperature than the rubber would experien
32、ce in service in order to produce the effects of natural ageing in a shorter time. 3.3 Heat resistance test In this method, the test pieces are subjected to the same temperature as they would experience in service. 4 Apparatus 4.1 Air oven 4.1.1 General The oven shall be of such a size that the tota
33、l volume of the 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 o
34、f the oven shall be controlled so that the temperature of the test pieces is kept within the specified tolerance for the specified ageing temperature (see Clause 8) for the whole ageing period. A temperature sensor shall be placed inside the heating chamber close to the samples to record the actual
35、ageing temperature. No copper or copper alloys shall be used in the construction of the heating chamber. 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. Care shall be taken to ensure that the incoming air is heated to
36、 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 oven chamber and the flow of air through the chamber. NOTE To ensure good precision when doing ageing and heat resistance te
37、sts, it is very important to keep the temperature uniform and stable 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 ventil
38、ation influence the ageing results. With a low air speed, accumulation of degradation products and 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
39、. 4.1.2 Cell-type oven The oven shall consist 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). Air passing through one cell shall n
40、ot enter other cells. Provision shall be made for a slow flow of air through the cell. The air speed shall depend on the air change rate only. 4.1.3 Cabinet oven This shall comprise a single chamber without separating walls. Provision shall be made for a slow flow of air through the oven. The air sp
41、eed shall depend on the air change rate only, and no fans are allowed inside the heating chamber. BS ISO 188:2011ISO 188:2011(E) ISO 2011 All rights reserved 34.1.4 Oven with forced air circulation Either of the following two types shall be used: a) Type 1 oven with laminar air flow (see Figure 1).
42、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 to avoid disturbing the air flow. The air speed shall be between 0,5 m/s and 1,5 m/s. The air speed near the test pieces can be
43、measured by means of an anemometer. Key 1 test pieces 2 laminar air flow 3 heating element 4 air inlet 5 air blower 6 air outlet Figure 1 Type 1 oven with laminar air flow b) Type 2 oven with turbulent air flow (see Figure 2). The air entering from a side-wall air-inlet into the heating chamber is t
44、urbulent around the test pieces, which are suspended on a carrier rotating at a speed of five to ten rotations per minute so that they are exposed to the heating air as uniformly as possible. The average air speed shall be 0,5 m/s 0,25 m/s. The average air speed near the test pieces can be calculate
45、d from measurements made with an anemometer at nine different positions (see Figure A.1 in Annex A). A suitable method of measurement is described in Annex A. BS ISO 188:2011ISO 188:2011(E) 4 ISO 2011 All rights reservedKey 1 test piece carrier 2 test pieces 3 turbulent air flow 4 laminar air flow (
46、inlet, outlet and near to wall) 5 heating element 6 motor 7 air inlet 8 air blower 9 air outlet Figure 2 Type 2 oven with turbulent air flow 5 Calibration The test apparatus shall be calibrated in accordance with Annex D. 6 Test pieces It is recommended that the accelerated ageing or heat resistance
47、 test be carried out on test pieces prepared and conditioned as required for the appropriate property tests, and not on complete products or sample sheets, and that their form be such that no mechanical, chemical or heat treatment will be required after ageing. Only test pieces of similar dimensions
48、 and having approximately the same exposed areas shall be compared with each other. The number of test pieces shall be in accordance with the International Standard for the BS ISO 188:2011ISO 188:2011(E) ISO 2011 All rights reserved 5appropriate property tests. The test pieces shall be measured befo
49、re heating but, whenever possible, marking shall be carried out after heating as some marking inks can affect the ageing of the rubber. Care shall be taken to ensure that the markings used to identify the test pieces are not applied in any critical area of the test piece and will not damage the rubber or disappear during heating. Avoid simultaneous heating of different types of compound in the same oven, to prevent the migration of sulphur, antioxidants, peroxides or plasticizers. For this purpose, the use of indiv
