1、 ISO 2012 Rubber, vulcanized or thermoplastic Determination of stress relaxation in compression Part 2: Testing with temperature cycling Caoutchouc vulcanis ou thermoplastique Dtermination de la relaxation de contrainte en compression Partie 2: Essais avec cycles de temprature INTERNATIONAL STANDARD
2、 ISO 3384-2 First edition 2012-11-15 Reference number ISO 3384-2:2012(E) ISO 3384-2:2012(E)ii ISO 2012 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2012 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, ele
3、ctronic 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 copyrightiso
4、.org Web www.iso.org Published in Switzerland ISO 3384-2:2012(E) ISO 2012 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 2 4 Principle 2 5 Apparatus . 2 6 Calibration 3 7 Test piece 3 7.1 Type and preparation of test p
5、iece 3 7.2 Measurement of dimensions of test pieces 4 7.3 Number of test pieces . 4 7.4 Time interval between forming and testing 4 7.5 Conditioning of test pieces . 4 8 Duration, temperature and test liquid 4 8.1 Duration of test . 4 8.2 Temperature of exposure . 5 8.3 Immersion liquids 5 9 Procedu
6、re. 5 9.1 Preparation 5 9.2 Thickness measurement . 5 9.3 Method A 5 9.4 Method B 7 10 Expression of results 8 11 Precision . 9 12 Test report . 9 Annex A (normative) Calibration schedule 10 Bibliography .12 ISO 3384-2:2012(E) Foreword ISO (the International Organization for Standardization) is a wo
7、rldwide 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 a subject for which a technical committee has been established has the right to be represented o
8、n 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 Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted
9、 in accordance with the rules given in the 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 Standa
10、rd requires approval by at least 75 % of the 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 3384-2 was prepared by
11、 Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee 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
12、: Testing with temperature cyclingiv ISO 2012 All rights reserved ISO 3384-2:2012(E) Introduction When 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
13、 subjected to a constant stress, an increase in the deformation 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
14、 normal or low temperatures and/or short times, stress relaxation 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
15、the Bibliography). In addition to the need to specify the temperatures 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 ru
16、bbers containing fillers. The two cycling test methods specified 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 tempe
17、ratures (method B). For products used in outdoor applications where 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 appl
18、ication and life-time. For polymers that crystallize at low temperature, 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 temperat
19、ure. ISO 2012 All rights reserved v Rubber, vulcanized or thermoplastic Determination of stress relaxation in compression Part 2: Testing with temperature cycling IMPORTANT 1 Persons using this part of ISO 3384 should be familiar with normal laboratory practice. This part of ISO 3384 does not purpor
20、t 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. I M PORT A N T 2 C er t a i n pr oce d u r es s pe c i f ie d i n t h
21、i s pa r t of ISO 3384 might involve the use or generation 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 Scope This part of ISO 3384 specifies two methods
22、 for determining the decrease in counterforce exerted by a test 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 tem
23、perature for checking the sealing force at this low temperature. 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 t
24、est piece are permitted: cylindrical test pieces and rings. Different 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 rela
25、xation in liquid environments. 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 (including any amendments) appl
26、ies. ISO 37:2011, Rubber, vulcanized or thermoplastic Determination of tensile stress-strain properties ISO 188:2011, Rubber, vulcanized or thermoplastic Accelerated ageing and heat resistance tests ISO 1817, Rubber, vulcanized or thermoplastic Determination of the effect of liquids ISO 18899:2004,
27、Rubber Guide to the calibration of test equipment ISO 23529, Rubber General procedures for preparing and conditioning test pieces for physical test methods INTERNATIONAL ST ANDARD ISO 3384-2:2012(E) ISO 2012 All rights reserved 1 ISO 3384-2:2012(E) 3 T erms a nd definiti ons For the purposes of this
28、 document, the following terms and definitions apply. 3.1 compression stress relaxation reduction in compressive force, expressed as a percentage of the initial force, which occurs with time after the application of a constant compressive strain 3.2 thermal stress mechanical stress induced in a body
29、 when some or all of its parts are not free to expand or contract in response to changes in temperature 4 Principle A 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
30、cycled between a high temperature and a low temperature to check the sealing force at this low temperature. The shrinkage of the rubber in going from the high to the low temperature decreases the counterforce. 5 Apparatus 5.1 Compression device, consisting of two parallel, flat, highly polished plat
31、es made from chromium- plated or stainless steel or other corrosion-resistant 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 polishe
32、d. The compression plates shall be flat and parallel and shall not undergo any 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 gri
33、nding or polishing. When the apparatus is assembled without a test piece, the 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 s
34、hall be of sufficient size to ensure that the whole of the compressed test piece 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 c
35、irculation of fluid inside the ring-shaped test piece. It shall be possible to connect 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 accur
36、acy of 1 % of the measured value. The device shall be capable of setting the compression 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 l
37、oss of heat from the test piece, for example by conduction through metal parts which are connected with the outside of the chamber.2 ISO 2012 All rights reserved ISO 3384-2:2012(E) 5.2 Counterforce-measuring device, capable of measuring compression forces in the desired range with an accuracy of 1 %
38、 of the measured value. The continuous-measurement system monitors the 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
39、.3 Temperature chamber: For tests in air, a well designed, uniformly 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
40、temperature chamber shall have a cooling and heating capability and be 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
41、compression device shall be totally immersed in the liquid in a bath, or 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
42、 a heater and circulation of the liquid in the bath or, alternatively, 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
43、 C in order to avoid ice formation which can introduce friction in the measuring 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
44、piece. NOTE A Pt100 sensor has been found to be suitable for temperature measurement. 6 Calibration The requirements for calibration of the test apparatus are given in Annex A. 7 Test piece 7.1 Type and preparation of test piece 7.1.1 General Test pieces shall be prepared either by moulding or by cu
45、tting from moulded sheets or products, in accordance with ISO 23529. NOTE The results obtained from test pieces of different sizes are not comparable. 7.1.2 Cylindrical test pieces The 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 piec
46、es The 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
47、 ISO 2012 All rights reserved 3 ISO 3384-2:2012(E) inner diameter: 15,0 mm 0,2 mm radial width: 2,0 mm 0,2 mm The sheets may be prepared by moulding or from finished articles by cutting and buffing. Alternatively, an O-ring with an internal diameter of 14,0 mm and a cross-section diameter of 2,65 mm
48、 may be used as the standard test piece. O-rings of other dimensions, together with seals or gaskets of other configuration, may be used as non- standard test pieces, where appropriate. 7.2 Measurement of dimensions of test pieces The dimensions of test pieces shall be measured as specified in ISO 2
49、3529. 7.3 Number of test pieces The preferred number of test pieces is three, but for routine and screening tests two test pieces are acceptable. 7.4 Time interval between forming and testing The interval between forming and testing shall be in accordance with ISO 23529. 7.5 Conditioning of test pieces 7.5.1 Prior to testing, the test pieces shall undergo first thermal and then mechanical conditioning as detailed in 7.5.2 and 7.5.3. When using method A at elevated temperature, the thermal conditi
