1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 3384-2:2012Rubber, vulcanized or thermoplastic Determination of stress relaxation in compressionPart 2: Testing with temperature cyclingBS ISO 3384-2:2012 BRITISH STANDARD
2、National forewordThis British Standard is the UK implementation of ISO 3384-2:2012. 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 be obtained on request to its secretary.This pu
3、blication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2013. Published by BSI Standards Limited 2013ISBN 978 0 580 72185 4 ICS 83.060 Compliance with a British Standard cannot confer immun
4、ity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 March 2013.Amendments issued since publicationDate T e x t a f f e c t e dBS ISO 3384-2:2012 ISO 2012Rubber, vulcanized or thermoplastic Determination of stress rel
5、axation in compression Part 2: Testing with temperature cyclingCaoutchouc vulcanis ou thermoplastique Dtermination de la relaxation de contrainte en compression Partie 2: Essais avec cycles de tempratureINTERNATIONAL STANDARDISO 3384-2First edition2012-11-15Reference number ISO 3384-2:2012(E)BS ISO
6、3384-2:2012ISO 3384-2:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise 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, wit
7、hout permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 3384-2:2012ISO 3384
8、-2:2012(E) ISO 2012 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 24 Principle 25 Apparatus . 26 Calibration 37 Test piece 37.1 Type and preparation of test piece 37.2 Measurement of dimensions of test pieces 47.3 Number of
9、test pieces . 47.4 Time interval between forming and testing 47.5 Conditioning of test pieces . 48 Duration, temperature and test liquid 48.1 Duration of test . 48.2 Temperature of exposure . 58.3 Immersion liquids 59 Procedure. 59.1 Preparation 59.2 Thickness measurement . 59.3 Method A 59.4 Method
10、 B 710 Expression of results 811 Precision . 912 Test report . 9Annex A (normative) Calibration schedule 10Bibliography .12BS ISO 3384-2:2012ISO 3384-2:2012(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies).
11、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 non-g
12、overnmental, 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.
13、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 the member bodies casting a vo
14、te.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 3384-2 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee
15、SC 2, Testing and analysis.ISO 3384 consists of the following parts, under the general title Rubber, vulcanized or thermoplastic Determination of stress relaxation in compression: Part 1: Testing at constant temperature Part 2: Testing with temperature cyclingiv ISO 2012 All rights reservedBS ISO 33
16、84-2:2012ISO 3384-2:2012(E)IntroductionWhen a constant strain is applied to rubber, the force necessary to maintain that strain is not constant but decreases with time; this behaviour is called “stress relaxation”. Conversely, when rubber is subjected to a constant stress, an increase in the deforma
17、tion takes place with time; this behaviour is called “creep”.The processes responsible for stress relaxation can be physical or chemical in nature, and under all normal conditions both types of process will occur simultaneously. However, at normal or low temperatures and/or short times, stress relax
18、ation is dominated by physical processes, while at high temperatures and/or long times chemical processes are dominant.If the life-time of a material is to be investigated, it can be determined using the method described in ISO 11346 (see the Bibliography).In addition to the need to specify the temp
19、eratures and time intervals in a stress relaxation test, it is necessary to specify the initial stress and the previous mechanical history of the test piece since these can also influence the measured stress relaxation, particularly in rubbers containing fillers.The two cycling test methods specifie
20、d are designed to carry out the following: age the test piece by stress relaxation and determine the sealing force at low temperatures (method A); introduce thermal stress by stress relaxation and determine the sealing force at low temperatures (method B).For products used in outdoor applications wh
21、ere the temperature can cycle between a low temperature (e.g. 40 C) and a high temperature (e.g. 150 C), it is important to also consider the shrinking of the rubber at low temperatures when assessing performance in the anticipated application and life-time.For polymers that crystallize at low tempe
22、rature, the crystallization will add to the shrinking of the rubber. For example, for hoses and seals in automotive applications, the product might work satisfactorily at the normal working temperature, but might leak at a low temperature. ISO 2012 All rights reserved vBS ISO 3384-2:2012BS ISO 3384-
23、2:2012Rubber, vulcanized or thermoplastic Determination of stress relaxation in compression Part 2: Testing with temperature cyclingIMPORTANT 1 Persons using this part of ISO 3384 should be familiar with normal laboratory practice. This part of ISO 3384 does not purport to address all of the safety
24、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.IMPORTANT 2 Certain procedures specified in this part of ISO 3384 might involve the use or generation
25、of substances, or the generation of waste, that could constitute a local environmental hazard. Reference should be made to appropriate documentation on safe handling and disposal after use.1 ScopeThis part of ISO 3384 specifies two methods for determining the decrease in counterforce exerted by a te
26、st piece of vulcanized or thermoplastic rubber which has been compressed to a constant deformation and then undergoes temperature cycling.Method A: The temperature is cycled at intervals between a high temperature for ageing and a low temperature for checking the sealing force at this low temperatur
27、e.Method B: The temperature is cycled continuously between a high temperature and a low temperature to introduce thermal stress in the test piece.The counterforce is determined by means of a continuous-measurement system.Two forms of test piece are permitted: cylindrical test pieces and rings. Diffe
28、rent shapes and sizes of test piece give different results, and comparison of results should be limited to test pieces of similar size and shape.The use of ring test pieces is particularly suitable for the determination of stress relaxation in liquid environments.2 Normative referencesThe following
29、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 (including any amendments) applies.ISO 37:2011, Rubber, vulcanized or thermoplastic Determination o
30、f tensile stress-strain propertiesISO 188:2011, Rubber, vulcanized or thermoplastic Accelerated ageing and heat resistance testsISO 1817, Rubber, vulcanized or thermoplastic Determination of the effect of liquidsISO 18899:2004, Rubber Guide to the calibration of test equipmentISO 23529, Rubber Gener
31、al procedures for preparing and conditioning test pieces for physical test methodsINTERNATIONAL STANDARD ISO 3384-2:2012(E) ISO 2012 All rights reserved 1BS ISO 3384-2:2012ISO 3384-2:2012(E)3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1compres
32、sion stress relaxationreduction in compressive force, expressed as a percentage of the initial force, which occurs with time after the application of a constant compressive strain3.2thermal stressmechanical stress induced in a body when some or all of its parts are not free to expand or contract in
33、response to changes in temperature4 PrincipleA test piece of vulcanized or thermoplastic rubber is compressed to a constant deformation at which it is maintained. The decrease in counterforce is then measured.The temperature is cycled between a high temperature and a low temperature to check the sea
34、ling force at this low temperature. The shrinkage of the rubber in going from the high to the low temperature decreases the counterforce.5 Apparatus5.1 Compression device, consisting of two parallel, flat, highly polished plates made from chromium-plated or stainless steel or other corrosion-resista
35、nt material, between the faces of which the test pieces are compressed. Flatness, surface roughness, parallelism and rigidity of the plates are all important.The surfaces of the compression plates shall be ground and polished. The compression plates shall be flat and parallel and shall not undergo a
36、ny distortion when the test load is applied.NOTE A finish to the surface giving a roughness profile Ra (see ISO 4287) of not worse than 0,4 m has been found to be suitable. Such a roughness profile Ra can be obtained by grinding or polishing.When the apparatus is assembled without a test piece, the
37、gap between the plates shall not vary by more than 0,01 mm.When the test assembly is subjected to the test load with a test piece between the plates, neither compression plate shall bend by more than 0,01 mm.The plates shall be of sufficient size to ensure that the whole of the compressed test piece
38、 is within the area of the plates and can expand freely laterally.For ring test pieces, the plates shall have holes of at least 2 mm diameter drilled through their centre portions to allow equalization of pressure and circulation of fluid inside the ring-shaped test piece.It shall be possible to con
39、nect the compression device to suitable equipment for compressing the test piece to the specified compression at the specified speed and for measuring the counterforce exerted by the compressed test piece with an accuracy of 1 % of the measured value.The device shall be capable of setting the compre
40、ssion and maintaining it during the whole duration of the test, and it shall be possible to keep the device in a temperature chamber at the specified test temperatures. Care shall be taken to ensure that there is no loss of heat from the test piece, for example by conduction through metal parts whic
41、h are connected with the outside of the chamber.2 ISO 2012 All rights reservedBS ISO 3384-2:2012ISO 3384-2:2012(E)5.2 Counterforce-measuring device, capable of measuring compression forces in the desired range with an accuracy of 1 % of the measured value.The continuous-measurement system monitors t
42、he test piece during the whole duration of the test, thus making continuous measurement of the change in counterforce with time possible. The deformation of the test piece shall be kept within 0,01 mm for the duration of the test.5.3 Temperature chamber: For tests in air, a well designed, uniformly
43、heated air temperature chamber shall be used, complying, for temperatures above standard laboratory temperature, with the requirements specified for one of the ovens used in ISO 188:2011, method A.For cycling the temperature, the temperature chamber shall have a cooling and heating capability and be
44、 able to change the temperature at a rate of 1,0 C/min 0,5 C/min.In the case of high-temperature tests and to avoid the surface oxidation of test pieces, other atmospheres may be used, such as nitrogen. For tests in liquids, the compression device shall be totally immersed in the liquid in a bath, o
45、r a closed vessel for volatile or toxic fluids, such that free circulation of the liquid can take place through the holes in the compression plates. The liquid shall be maintained at the specified temperature by proper control of a heater and circulation of the liquid in the bath or, alternatively,
46、by placing the liquid bath and compression device within a temperature chamber as specified above.NOTE It is recommended that the air used for air exchange be passed through an air dryer to give it a dew point not higher than 40 C in order to avoid ice formation which can introduce friction in the m
47、easuring system.5.4 Temperature-measuring equipment, with a sensing element having appropriate precision. The temperature-sensing element shall be installed in such a way that it accurately measures the temperature of the test piece.NOTE A Pt100 sensor has been found to be suitable for temperature m
48、easurement.6 CalibrationThe requirements for calibration of the test apparatus are given in Annex A.7 Test piece7.1 Type and preparation of test piece7.1.1 GeneralTest pieces shall be prepared either by moulding or by cutting from moulded sheets or products, in accordance with ISO 23529.NOTE The res
49、ults obtained from test pieces of different sizes are not comparable.7.1.2 Cylindrical test piecesThe test piece shall be a cylindrical disc of diameter 13,0 mm 0,5 mm and thickness 6,3 mm 0,3 mm.7.1.3 Ring test piecesThe preferred ring test piece is a ring of square cross-section cut from a flat sheet of the test material by means of rotary cutters. For a suitable machine for the preparation of small ring test pieces, see Annex A of ISO 37:2011.The dimensions of test pieces shall be: thickness: 2,0 mm 0,2 mm IS
