1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 1432:2013Rubber, vulcanized orthermoplastic Determinationof low-temperature stiffening(Gehman test)BS ISO 1432:2013 BRITISH STANDARDNational forewordThis British Standard
2、is the UK implementation of ISO 1432:2013. Itsupersedes BS 903-A13:1990 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee PRI/22, Physical testing of rubber.A list of organizations represented on this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.T
3、his publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 69687 9ICS 83.060Compliance with a British Standard cannot confer immu
4、nity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 30 June 2013.Amendments issued since publicationDate Text affectedBS ISO 1432:2013 ISO 2013Rubber, vulcanized or thermoplastic Determination of low-temperature stiffeni
5、ng (Gehman test)Caoutchouc vulcanis ou thermoplastique Dtermination de la rigidit basse temprature (Essai Gehman)INTERNATIONAL STANDARDISO1432Fourth edition2013-01-15Reference numberISO 1432:2013(E)BS ISO 1432:2013ISO 1432:2013(E)ii ISO 2013 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2013Al
6、l 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, without permission in writing from either ISO at the address below or ISOs member body in the country
7、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 1432:2013ISO 1432:2013(E) ISO 2013 All rights reserved iiiContents PageForeword iv1 Scope . 12 Normative references 13
8、 Principle 14 Apparatus . 15 Calibration 36 Test piece 36.1 Preparation of test piece . 36.2 Conditioning of test piece 37 Procedure. 47.1 Mounting of test piece 47.2 Stiffness measurements in liquid media . 47.3 Stiffness measurements in gaseous media . 47.4 Crystallization 58 Number of tests 59 Ex
9、pression of results 59.1 Torsional modulus . 59.2 Relative modulus . 59.3 Apparent torsional modulus of rigidity . 510 Test report . 6Annex A (normative) Calibration schedule . 9Bibliography .12BS ISO 1432:2013ISO 1432:2013(E)ForewordISO (the International Organization for Standardization) is a worl
10、dwide 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 on
11、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 in
12、 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 Standard r
13、equires 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 1432 was prepared by Technic
14、al Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 2, Testing and analysis.This fourth edition cancels and replaces the third edition (ISO 1432:1988), which has been technically revised to allow computerized instruments to be used. In addition, a calibration schedule has been added
15、(see Annex A). It also incorporates the Technical Corrigendum ISO 1432:1988/Cor.1:2003.iv ISO 2013 All rights reservedBS ISO 1432:2013INTERNATIONAL STANDARD ISO 1432:2013(E)Rubber, vulcanized or thermoplastic Determination of low-temperature stiffening (Gehman test)WARNING Persons using this Interna
16、tional Standard should be familiar with normal laboratory practice. This standard does not 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 natio
17、nal regulatory conditions.CAUTION Certain procedures specified in this International Standard 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
18、disposal after use.1 ScopeThis International Standard specifies a static procedure, known as the Gehman test, for determining the relative stiffness characteristics of vulcanized or thermoplastic rubbers over a temperature range from room temperature to approximately 150 C.2 Normative referencesThe
19、following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 18899:20
20、04, Rubber Guide to the calibration of test equipmentISO 23529, Rubber General procedures for preparing and conditioning test pieces for physical test methods3 PrincipleThe torsional stiffness is measured as a function of temperature, starting from a low temperature. The stiffness is measured by con
21、necting the test piece in series with a calibrated spring wire and measuring the angle of twist of the test piece when the top of the wire is turned 180.4 Apparatus4.1 Torsion apparatus, consisting of a torsion head, capable of being turned 180 in a plane normal to the torsion wire. The top of the w
22、ire is fastened to the torsion head. The bottom of the wire is fastened to the test piece clamp. A device for “friction-free” indication or recording of angle by mechanical or electrical means shall be provided, permitting convenient and exact adjustment of the zero point. The indicating or recordin
23、g system shall allow reading or recording of the angle of twist to the nearest degree. This principle is shown in Figure 1.4.2 Torsion wires, made of tempered spring wire, of a length of 65 mm 8 mm, and having nominal torsional constants of 0,7 mNm, 2,8 mNm and 11,2 mNm. In cases of dispute, the 2,8
24、 mNm wire shall be used. ISO 2013 All rights reserved 1BS ISO 1432:2013ISO 1432:2013(E)KeyA torsion headB torsion wireC angle measurementD test pieceE test piece rackFigure 1 Principle of a torsion apparatus4.3 Test piece rack, made of material of poor thermal conductivity, for holding the test piec
25、e in a vertical position in the heat transfer medium. The rack may be constructed to hold several test pieces. The rack is attached to a stand. It is advantageous to make the vertical portion of the stand from material of poor thermal conductivity. The base of the stand shall be of stainless steel o
26、r other corrosion-resistant material.Two clamps shall be provided for holding each test piece. The bottom clamp shall be attached to the test piece rack. The top clamp acts as an extension of the test piece and is connected to the torsion wire by a rod.4.4 Heat-transfer medium, liquid or gaseous, wh
27、ich remains fluid at the test temperature and which does not appreciably affect the material being tested, as prescribed in ISO 23529.Gases may be employed as the heat transfer medium provided the design of the apparatus is such that results obtained using them duplicate those obtained with liquids.
28、NOTE The following fluids have been used satisfactorily:a) for temperatures down to 60 C, silicone fluids of kinematic viscosity of about 5 mm2/s at ambient temperature, which are usually suitable owing to their chemical inertness towards rubbers, their non-flammability and their non-toxicity;b) for
29、 temperatures down to 73 C, ethanol;c) for temperatures down to 120 C, methylcyclohexane cooled by liquid nitrogen (found to be satisfactory with the use of suitable apparatus).2 ISO 2013 All rights reservedBS ISO 1432:2013ISO 1432:2013(E)4.5 Temperature-measuring device, capable of measuring temper
30、ature to within 0,5 C over the whole range of temperature over which the apparatus is to be used.The temperature sensor shall be positioned near the test pieces.4.6 Temperature control, capable of maintaining the temperature of the heat-transfer medium to within 1 C.4.7 Container for heat-transfer m
31、edium, a bath for a liquid medium, or a test chamber for a gaseous medium, with means of heating the coolant.4.8 Stirrer, for liquids, or fan or blower, for gases, which ensures thorough circulation of the heat-transfer medium. It is important that the stirrer also moves the liquid vertically to ens
32、ure a uniform temperature in the liquid.4.9 Stopwatch, or other timing device, graduated in seconds.5 CalibrationThe requirements for calibration of the test apparatus are given in Annex A.6 Test piece6.1 Preparation of test pieceTest pieces shall be prepared in accordance with ISO 23529.The dimensi
33、ons of the test piece shall be: length 40 mm 2,5 mm, width 3 mm 0,2 mm and thickness 2 mm 0,2 mm. lt shall be moulded or cut with a suitable die from a moulded sheet of suitable thickness.6.2 Conditioning of test piece6.2.1 The minimum time between forming and testing shall be 16 h.For non-product t
34、ests, the maximum time between forming and testing shall be 4 weeks and, for evaluations intended to be comparable, the tests should be carried out, as far as possible, after the same time interval.For product tests, whenever possible, the time between forming and testing should not exceed 3 months.
35、 In other cases, tests shall be made within 2 months of the date of receipt by the customer of the product.6.2.2 Samples and test pieces shall be protected from light as much as possible during the interval between forming and testing.6.2.3 Prepared test pieces shall be conditioned in accordance wit
36、h ISO 23529 immediately before testing for a minimum of 3 h at a standard laboratory temperature, the same temperature being used throughout any one test or series of tests intended to be comparable. ISO 2013 All rights reserved 3BS ISO 1432:2013ISO 1432:2013(E)7 Procedure7.1 Mounting of test pieceC
37、lamp each test piece used in such a manner that 25 mm 3 mm of the test piece is free between the clamps. The test piece clamp shall be located in such a position that the specimen is under zero torque or with a slight pre-load to keep the test piece straight when the temperature changes.If the absol
38、ute modulus is required, measure the test length of the test pieces to the nearest 0,5 mm, the width to the nearest 0,1 mm and the thickness to the nearest 0,01 mm.7.2 Stiffness measurements in liquid mediaMake the reference measurement with the standard torsion wire (2,8 mNm) at 23 C 2 C, either in
39、 air or in the liquid bath.Place the rack containing the test pieces in the liquid bath with a minimum of 25 mm of liquid covering the test pieces.Adjust the angle measuring device to zero. Then turn all test pieces at the same time, or in sequence, quickly but smoothly, through 180 and record the t
40、orsion angle after 10 s. If the test pieces are measured in sequence, ensure that all the measurements are completed within approximately 2 min. If the reading at 23 C does not fall in the range of 120 to 170, the standard torsion wire is not suitable for testing the test piece. Test pieces producin
41、g twists of more than 170 shall be tested with a wire having a torsional constant of 0,7 mNm. Test pieces producing twists of less than 120 shall be tested with a wire having a torsional constant of 11,2 mNm.Remove the test pieces from the liquid bath (assuming the reference measurement has been mad
42、e in liquid) and adjust the temperature of the liquid to the lowest temperature desired.Place the test pieces in the bath with a minimum of 25 mm of liquid covering the test pieces and maintain them at this temperature for approximately 15 min.Then increase the bath temperature by one of the two fol
43、lowing methods:a) stepwise by 5 C intervals, each increase being made after approximately 5 min;b) continuously with a heating rate of about 1 C/min.Make the stiffness measurements in the stepwise case after conditioning the test piece for 5 min at each temperature and in the continuous case at inte
44、rvals of 1 min maximum. Continue the tests until a temperature is reached at which the angular twist is within 5 to 10 of the twist at 23 C.Record the angle of twist and the temperature at each measurement.The relative modulus may be plotted on a graph during the test.7.3 Stiffness measurements in g
45、aseous media7.3.1 GeneralProcedures with air, carbon dioxide or nitrogen differ from those with liquid media only in that the cooling is done with the test pieces in the medium and the length of the conditioning period is different.7.3.2 MeasurementsWith the test pieces in the test chamber, adjust t
46、he temperature of the chamber to the lowest temperature desired in approximately 30 min. After this temperature has been maintained constant for 10 min, make the measurements in a similar way to those in the liquid media, ensuring that all the test pieces in the rack are tested within 2 min.4 ISO 20
47、13 All rights reservedBS ISO 1432:2013ISO 1432:2013(E)Then increase the chamber temperature by one of the two following methods:a) stepwise by 5 C intervals, each increase being made after approximately 10 min;b) continuously with a heating rate of about 1 C/min.Make the stiffness measurements in th
48、e stepwise case after conditioning the test piece for 10 min at each temperature and, in the continuous case, at intervals of 1 min maximum. Continue the tests until a temperature is reached at which the angular twist is within 5 to 10 of the twist at 23 C.Record the angle of twist and the temperatu
49、re at each measurement.The relative modulus may be plotted on a graph during the test.7.4 CrystallizationWhen it is desired to study crystallization or plasticizer effects, the time of conditioning at the desired temperature should be increased.8 Number of testsAt least three test pieces of each material shall be tested. lt is good practice to include a control rubber with known twist/temperature characteristics.9 Expression of results9.1 Torsional modulusThe torsional modulus of the t
