1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA
2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any
3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ICS 83.060 ISBN 0-626-14407-8 SANS 11431-1:2003Edition 1ISO 1431-1:1989Edition 3SOUTH AFRICAN NATIONAL STANDARD Rubber, vulcanized or thermoplastic Resis
4、tance to ozone cracking Part 1: Static strain test Published by Standards South Africa 1 dr lategan road groenkloof ! private bag x191 pretoria 0001 tel: 012 428 7911 fax: 012 344 1568 international code + 27 12 www.stansa.co.za Standards South Africa 2003 This national standard is the identical imp
5、lementation of ISO 1431-1:1989 and is adopted with the permission of the International Organization for Standardization SANS 11431-1:2003 Edition 1 ISO 1431-1:1989 Edition 3 Table of changes Change No. Date Scope National Foreword This South African standard was approved by National Committee STANSA
6、 TC 5140.17, Rubber and rubber products, in accordance with procedures of Standards South Africa, in compliance with annex 3 of the WTO/TBT agreement. INTERNATIONAL STANDARD Is0 1431-l Third edition 1989-06-15 Rubber, vulcanized or thermoplastic - Resistance to ozone cracking - Part 1: Static strain
7、 test Caou tchouc vulcanisk ou thermoplastique - Rbsistance au craquelage par /ozone e Partie 7: Essai sous allongement statique Reference number IS0 1431-l : 1989 (E) IS0 14314 : 1989 (E) Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standar
8、ds bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 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 organi
9、zations, govern- mental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are c
10、irculated to the member bodies for approval before their acceptance as International Standards by the IS0 Council. They are approved in accordance with IS0 procedures requiring at least 75 % approval by the member bodies voting. International Standard IS0 1431-1 was prepared by Technical Committee l
11、SO/TC 45, Rubber and rubber products. This third edition cancels and replaces the second edition (IS0 1431-l : 19801, of which it constitutes a technical revision. IS0 1431 consists of the following parts, under the general title Rubber, vulcanized or thermoplastic - Resistance to ozone cracking : .
12、 - Part 7: Static strain test - Part 2: Dynamic strain test - Part 3: Reference test chambers method for determining ozone concentration in labora tory Annex A of this part of IS0 1431 is for information only. 0 IS0 1989 All rights reserved. No part of this publication may be reproduced or utilized
13、in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case postale 56 l CH-1211 Geneve 20 l Switzerland Printed in Switzerland INTERNATIONAL STANDARD IS0 1431-l : 1
14、989 (E) Rubber, vulcanized or thermoplastic - Resistance to ozone cracking - Part 1: Static strain test 1 Scope This part of IS0 1431 specifies a method for the determination of resistance of vulcanized or thermoplastic rubbers to cracking when exposed, under static tensile strain, to air containing
15、 a definite concentration of ozone and at a definite temperature in circumstances that exclude the effects of direct light. Great caution is necessary in attempting to relate standard test results to service performance since the relative ozone resistance of different rubbers can vary markedly accor
16、ding to conditions, especially ozone concentration and temperature. In addition, tests are carried out on thin test pieces deformed in tension and the significance of attack for articles in service may be quite different owing to the effects of size and the type and magnitude of deformation. Explana
17、tory notes on the nature of ozone cracking are given in annex A. Methods for determining resistance to ozone cracking under dynamic strain conditions and combined dynamic and static strain conditions are specified in IS0 1431-2. A reference method for estimating the ozone concentration will form the
18、 subject of IS0 1431-3. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of IS0 1431. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreem
19、ents based on this part of IS0 1431 are encouraged to investigate the possibility of applying the most recent editions of the standards listed below. Members of IEC and IS0 maintain registers of currently valid International Standards. IS0 471: 1983, Rubber - Standard temperatures, humidities and ti
20、mes for the conditioning and testing of test pieces. IS0 1431-2: 1982, Rubber, vulcanized - Resistance to ozone cracking - Part 2: Dynamic strain test. is0 4661-l : 1986, Rubber, vulcanized - Preparation of samples and test pieces - Part 7: Physical tests. 3 Definitions For the purpose nitions apply
21、. of this part of IS0 1431, the following defi- 3.1 threshold strain: The highest tensile strain at which a rubber can be exposed at a given temperature to air containing a given concentration of ozone without ozone cracks devel- oping on it after a given exposure period. Threshold strain must be di
22、stinguished from limiting threshold strain, defined in 3.2. 3.2 limiting threshold strain: The tensile strain below which the time required for the development of ozone cracks increases very markedly and can become virtually infinite. 4 Principle Test pieces are exposed under static tensile strain,
23、in a closed chamber at a constant temperature, to an atmosphere contain- ing a fixed concentration of ozone. The test pieces are exam- ined periodically for cracking. Three alternative evaluation procedures are described for selected values of ozone concentration and exposure temperature: A Determin
24、ation of the presence or absence of cracks, and if required, an estimate of the degree of cracking, after exposure for a fixed period of time at a given strain. B Determination of time to the first appearance of cracks at any given strain. C Determination of the threshold strain for any given ex- po
25、sure period. 1 IS0 1431-l : 1989 E) 5 Apparatus (see figure I) WARNING - Attention is drawn to the highly toxic nature of ozone. Efforts should be made to minimize the exposure of workers at all times. In the absence of more stringent or contrary national safety regulations in member body countries,
26、 it is recommended that 10 parts of ozone per hundred million parts of air of the surround- ing atmosphere by volume be regarded as an absolute maximum concentration whilst the maximum average concentration should be appreciably lower. NOTE - An exhaust vent to remove ozone-laden air is advised. 5.1
27、 Test chamber. This shall be a closed, non-illuminated chamber, ther- mostatically controlled to within + 2 OC of the test temperature, lined with, or constructed of, a material (for example, aluminium) that does not readily decompose ozone. Dimensions shall be such that the requirements of 5.5 are
28、met. The chamber may be provided with a window through which the surface of the test pieces can be observed. A light to examine test pieces may be installed. 5.2 Source of ozonized air Either of the following apparatus may be used: a) b) a silent discharge tube. an ultra-violet lamp; Regulator - Flo
29、wmeter , 1 Ozonizer Figure 1 - Schematic diagram of the apparatus r-l The use of oxygen is necessary when using the discharge tube in order to avoid the formation of nitrogen oxides. The ozon- ized oxygen or air may be diluted with air to attain the required ozone concentration. Air used for generat
30、ion of ozone or di- lution shall first be purified by passing it over activated charcoal and shall be free from any contaminants likely to affect the ozone concentration, cracking or estimation of ozone. The temperature of the source shall be kept constant to within + 2 OC. The ozonized air shall be
31、 fed from the source into the chamber via a heat exchanger to adjust its temperature to that required for the test and shall be brought to the specified relative humidity (see 8.3). 5.3 Means for adjusting the concentration of ozone This may be, but does not have to be, automatic. When an ultra-viol
32、et light source is used the amount of ozone produced can be controlled by adjusting the voltage applied to the tube or the gas flow rates, or by shielding part of the tube exposed to the gas flow. When a silent discharge tube is used, the amount of ozone produced can be controlled by adjusting the v
33、oltage applied to the generator, the dimensions of the electrodes, the oxygen flow rate, or the diluent air flow rate. A two-stage dilution of the ozonized air can also be used. The ad- justments shall be such that they will maintain the concen- tration within the tolerances given in 8.1. In additio
34、n, after each occasion that the test chamber is opened for insertion or in- spection of test pieces, the ozone concentration shall return to the test concentration within 30 min. The concentration of ozone entering the chamber shall at no time exceed the con- centration specified for the test. Purif
35、ying column r Flowmeter t Heat exchanger Temperature indicator 2 IS0 1431-l : 1989 (E) 5.4 Means of determining the ozone concentration A means of sampling the ozonized air from the vicinity of the test pieces in the chamber and means of estimating its ozone content shall be provided. The methods fo
36、r estimating the ozone concentration will form the subject of IS0 1431-3. 5.5 Means of adjusting gas flow A mechanism shall be provided which is capable of adjusting the average velocity of flow of ozonized air in the test chamber to a value of not less than 8 mm/s and preferably to a value be- twee
37、n 12 mm/s and 16 mm/s, calculated from the measured gas flow rate in the chamber divided by the effective cross- sectional area of the chamber normal to the gas flow. In tests intended to be comparable, the velocity shall not vary by more than + 10 %. The gas flow rate is the volume throughput of oz
38、onized air in unit time and this shall be sufficiently high to prevent the ozone concentration in the chamber being significantly reduced owing to ozone destruction by the test pieces. The rates of destruction will vary according to the rub- ber being used, the test conditions and other details of t
39、he test. As a general guide, it is recommended that the ratio of the ex- posed surface area of the test pieces to the gas flow rate should not exceed 12 s/m, but this may not always be low enough. In cases where there is doubt, the effects of destruction should be checked experimentally and, if nece
40、ssary, the test piece area should be decreased. A diffusing screen or equivalent device should be used to assist thorough mixing of incoming gas with that in the chamber. If high velocities are desired, a fan may be installed in the chamber to raise the velocity of flow of ozonized air to 600 mm/s +
41、 100 mm/s. NOTE - The ratio, expressed in seconds per metre, is derived from surface area in square metres and volumetric flow rate in cubic metres per second. 5.6 Test piece carrier Clamps shall be provided for holding the test pieces at the re- quired elongation with both sides in contact with the
42、 ozonized air in such a manner that the length of the test piece is substan- tially parallel to the gas flow. The clamps shall be made of a material which does not readily decompose ozone (for example aluminium). The use of a mechanically rotating carrier mounted in the test chamber and upon which t
43、he clamps or frames for holding the test pieces are mounted is recommended to equalize the effect of different ozone concentrations in the chamber. In one example of a suitable carrier, the test pieces move at a speed between 20 mm/s to 25 mm/s in a plane normal to the gas flow and each follow conse
44、cutively the same path in such a manner that the same position within the chamber is visited by the same piece every 8 min to 12 min, and the area swept by the piece (shown shaded in figure 2) is at least 40 % of the available cross-sectional area of the chamber. Figure 2 - Path of test piece and sw
45、ept area (shaded) 6 Test piece 6.1 General Standard test pieces shall be strips or dumb-bells as specified in 6.2 and 6.3. Test pieces shall be cut from freshly moulded sheet or, if re- quired, from a finished product in accordance with IS0 4661-1. Test pieces shall have an undamaged test surface; o
46、zone resistance shall not be assessed on surfaces that have been cut or buffed. Comparisons of different materials are only valid if the cracking is assessed on surfaces of similar finish produced by the same method. For each test condition, at least three test pieces shall be used. 6.2 Strip test p
47、iece The test piece shall consist of a strip of not less than 10 mm width, thickness 2,0 mm k 0,2 mm, and length not less than 40 mm between the grips before stretching. The ends of the test piece held in the grips may be protected with an ozone-resistant lacquer. Care shall be taken in selecting a
48、lacquer to ensure that the solvent used does not appreciably swell the rubber. Silicone grease shall not be used. Alterna- tively, the test piece may be provided with modified ends, for example by the use of lugs, to enable it to be extended without causing excessive stress concentration and breakag
49、e at the grips during ozone exposure. 3 IS0 1431-1 : 1989 (E) 6.3 Dumb-bell test piece Samples and test pieces shall be stored in the dark, in an essen- tially ozone-free atmosphere during the period between vulcanization and stretching; the normal storage temperature should be the standard temperature (see IS0 4711, but other, controlled, temperatures may be used if appropriate for par- ticular applications. These storage conditions should be used, as far as possible, for products. For evaluations intended to be comparable, the storage time and conditions shall be identical. The test pie
