《BS-ISO-2921-2005.pdf》由会员分享，可在线阅读，更多相关《BS-ISO-2921-2005.pdf（14页珍藏版）》请在三一文库上搜索。
1、BRITISH STANDARD BS ISO 2921:2005 Rubber, vulcanized Determination of low-temperature characteristics Temperature- retraction procedure (TR test) ICS 83.060 ? Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:48:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 2921:2005 This British Stan
2、dard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2006 BSI 31 January 2006 ISBN 0 580 47160 8 National foreword This British Standard reproduces verbatim ISO 2921:2005 and implements it as the UK national standard. It supersedes BS 903-A29:1997 which
3、 is withdrawn. The UK participation in its preparation was entrusted to Technical Committee PRI/22, Physical testing of rubber, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards w
4、hich implement international 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 Online. This publication does
5、not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European
6、committee any enquiries on the interpretation, or proposals for change, and keep UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii t
7、o iv, pages 1 to 6, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:48:27 GMT+00:00 2006, Uncont
8、rolled Copy, (c) BSI INTERNATIONAL STANDARD ISO 2921 Fourth edition 2005-09-15 Reference number ISO 2921:2005(E) Rubber, vulcanized Determination of low-temperature characteristics Temperature-retraction procedure (TR test) Caoutchouc vulcanis Dtermination des caractristiques basse temprature Mthode
9、 temprature-retrait (essai TR) BS ISO 2921:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:48:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:48:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iii Contents Page 1Scope 1 2Normati
10、ve references 1 3Principle 1 4Apparatus . 1 5Test pieces . 2 6Procedure . 4 7Expression of results 5 8Test report 5 BS ISO 2921:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:48:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv Foreword ISO (the International Organization for Standard
11、ization) 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 a subject for which a technical committee has been established has the right to
12、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 Commission (IEC) on all matters of electrotechnical standardization. International Stand
13、ards are drafted 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 Inte
14、rnational Standard 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 2921 w
15、as prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 2, Testing and analysis. This fourth edition cancels and replaces the third edition (ISO 2921:1997), which has been technically revised. BS ISO 2921:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 0
16、7:48:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 1 Rubber, vulcanized Determination of low-temperature characteristics Temperature-retraction procedure (TR test) WARNING Persons using this International Standard should be familiar with normal laboratory practice. This standard does not purport to
17、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. Certain procedures specified in this International Standard may involve the
18、 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. 1Scope This International Standard specifies a method for the determination of the temperat
19、ure-retraction characteristics of stretched vulcanized rubber. NOTEThis International Standard does not include thermoplastic rubbers, as many thermoplastic elastomers have a yield point in the range of to elongation. This fact may affect the result when carrying out TR tests on thermoplastic rubber
20、s, and the results obtained from such tests should be analysed with caution. 2Normative 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 refere
21、nced document (including any amendments) applies. ISO 23529, Rubber General procedures for preparing and conditioning test pieces for physical test methods 3Principle A test piece is stretched at standard laboratory temperature and then cooled to a sufficiently low temperature such that retraction d
22、oes not occur upon removal of the stretching force. The stretching force is removed and the temperature increased at a uniform rate. The temperatures at which specified percentage retractions occur are determined. NOTEIn addition to the two sizes of standard test piece, other types of test piece cut
23、 from products are described. These do not necessarily give the same values of retraction temperature, and comparison between the values obtained using different types of test pieces should be avoided. 4Apparatus See Figure 1. 4.1Bath for coolant, which is insulated and equipped with a stirrer, a th
24、ermometer and a device for heating the coolant in accordance with ISO 23529. 4.2Coolant, which does not affect the rubber material being tested, as prescribed in ISO 23529. 5 %20 % BS ISO 2921:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:48:27 GMT+00:00 2006, Uncontrolled Copy, (c)
25、 BSI 2 Gases may be employed as the coolant provided the design of the apparatus is such that results obtained using them will duplicate those obtained with liquids. The following fluids can be used: a)for temperatures down to , silicone oils of kinematic viscosity about at ambient temperature, owin
26、g to their chemical inertness towards rubbers, their non-flammability and their non-toxicity; b)for temperatures down to , methanol or ethanol; c)for temperatures down to , methylcyclohexane cooled by liquid nitrogen (found to be satisfactory with the use of suitable apparatus). 4.3Rack with test pi
27、ece holders, equipped with a loading device, holders for one or more test pieces and a locking device for the upper (movable) test piece holders (see Figure 1). The rack shall be designed to maintain a slight tension ( to ) on the test pieces and to permit them to be stretched up to a maximum of ; t
28、he design shall permit the upper test piece holder to be locked into position at the chosen elongation and subsequently released. Means shall be provided to enable the length of the test pieces to be read, at any time during the test, with an accuracy of or better. Alternatively, a series of removab
29、le scales graduated to allow the retraction to be read directly as a percentage of the elongation of the frozen rubber with an accuracy of may be used. The movable parts of the apparatus shall be constructed so that the lowest possible friction occurs. 5Test pieces 5.1Preparation Test pieces shall b
30、e prepared in general accordance with ISO 23529. 5.2Types 5.2.1Standard test piece The standard test piece shall be a strip with enlarged ends for clamping, with dimensions in accordance with Figure 2. The reference length shall be either or . The test piece with a reference length of is preferred f
31、or tests with small elongations and the test piece with a reference length of for tests with larger elongations. Test pieces shall be cut with a sharp die from a flat sheet thick. The sheets may be prepared by moulding or from finished products by cutting and buffing. The test piece can also be used
32、 with elongation if the reading accuracy of the measurement system is or better. 5.2.2Test pieces cut from products Alternatively, other types of test piece cut from finished rubber products may be used (for example an O-ring with a cross-sectional diameter between and ). 5.3Number At least three te
33、st pieces shall be used for each test. 60 C 5 mm2/s 70 C 120 C 10 kPa20 kPa 350 % 0,25 mm 0,5 % 100 mm50 mm 100 mm50 mm 2 mm0,2 mm 50 mm50 % 0,125 mm 1,5 mm4 mm BS ISO 2921:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:48:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 3 Key 1pulley 2
34、cord 3counterweight 4stirrer 5heating device (immersion heater) for coolant 6rack 7removable graduated scales 8upper part of upper test piece holder 9locking device for upper test piece holder 10thermal insulation 11container for coolant 12upper test piece holder 13test piece 14lower test piece hold
35、er Figure 1 Retraction apparatus BS ISO 2921:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:48:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 4 5.4Conditioning 5.4.1Unless otherwise specified for technical reasons, the procedure in 5.4.2 to 5.4.5 shall be followed. 5.4.2The time-inter
36、val between vulcanization and testing shall be in accordance with ISO 23529. 5.4.3Samples and test pieces shall be protected from light as completely as possible during the interval between vulcanization and testing. 5.4.4Test pieces shall be conditioned, immediately before testing, at one of the st
37、andard laboratory temperatures specified in ISO 23529. 5.4.5If samples that are apt to crystallize are exposed to low storage temperatures before testing, crystallization may occur that largely affects the TR values measured. If values for the material in the uncrystallized condition are desired, th
38、e test pieces shall be decrystallized before testing by heating them in an oven at for . They shall then be conditioned at standard laboratory temperature for at least but not more than . 6Procedure The bath shall contain enough coolant (4.2) to cover the test pieces with at least of liquid during t
39、esting. Cool the coolant, whilst stirring, to below as described in ISO 23529. While the liquid is cooling, insert the test pieces in the rack (4.3) and, at the standard laboratory temperature, stretch the reference length to the chosen elongation and lock each test piece in position. Ensure that th
40、e test piece is only kept stretched at standard laboratory temperature for the minimum time. The elongation shall be chosen in the light of the following criteria: a)provided technical reasons do not dictate otherwise and to reduce the effect of crystallization, an elongation of shall be used; Dimen
41、sions in millimetres The reference length is preferably for small elongations and for large elongations (see 5.2.1) Figure 2 Test piece l0100 mm0,2 mm50 mm0,2 mm 70 C 30 min30 min 60 min 25 mm 70 C 50 % BS ISO 2921:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:48:27 GMT+00:00 2006,
42、Uncontrolled Copy, (c) BSI 5 b)one of the following elongations shall be used to study the combined effect of crystallization and low temperature: 1), 2)half the elongation at break if is unobtainable, 3), if the elongation at break is greater than . When the coolant has reached an equilibrium tempe
43、rature between and , place the rack with the test pieces in the bath. Allow to stand for in the bath between and . Release the locking device holding the upper holder and allow the test pieces to retract freely. At the same time, raise the temperature of the liquid at the rate of , the tolerance bei
44、ng such that the temperature rise during any interval is within . Should an elongated test piece retract to the original length at , cool to a lower temperature, using, if necessary, another coolant. Take the first reading at and continue to read the actual temperature and the retracted length or th
45、e percentage retraction every until retraction has reached . NOTE 1For the study of crystallization effects or the effect of long-term exposure, longer times of exposure under strain at one or more selected low temperatures may be used depending on the purpose of the test and the material under inve
46、stigation. NOTE 2Different elongations do not necessarily give the same results. 7Expression of results The percentage retraction may be read from the graduated scales or calculated from the equation: where is the stretched length in the locked position; is the retracted length at the temperature co
47、ncerned; is the reference length. Plot against the actual temperature on a graph. From the graph, read the temperatures which correspond to retractions of , , and . These temperatures are designated TR10, TR30, TR50 and TR70. Calculate the median value of three determinations of the temperature for
48、TR10, TR30, TR50 and TR70. 8Test report The test report shall include the following information: a)sample details: 1)a full description of the sample and its origin, 2)compound details and cure details, where appropriate, 3)the method of preparation of the test pieces from the sample, for example mo
49、ulded or cut; 250 % 250 % 350 %600 % 70 C 73 C 10 min2 min70 C 73 C 1 C/min 10 min10 C 2 C 70 C 70 C 2 min75 % r r = ls lr ls l0 100 ls lr l0 r 10 % 30 % 50 %70 % BS ISO 2921:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:48:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 6 b)test method: 1)a reference to the test method used, i.e. the number of this International Standard, 2)the type of test piece used; c)test details: 1)the standard