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1、BRITISH STANDARD BS 903-A43: 1990 ISO 1431-1: 1989 Physical testing of rubber Part A43: Method for determination of resistance to ozone cracking (static strain test) Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 04:49:58 GMT+00:00 2006, Uncontrolled Copy, (c)
2、BSI BS 903-A43:1990 This British Standard, having been prepared under the direction of the Rubber Standards Policy Committee, was published under the authority of the Board of BSI and comes into effect on 30 June 1990 BSI 03-1999 First published February 1982 Second edition June 1990 The following B
3、SI references relate to the work on this standard: Committee reference RUM/36 Draft for comment 86/40471 DC ISBN 0 580 18584 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Rubber Standards Policy Committee (RUM/-) to Technical Committ
4、ee RUM/36, upon which the following bodies were represented: BP Chemicals Ltd. British Railways Board British Rubber Manufacturers Association GAMBICA (BEAMA Ltd.) Institution of Mechanical Engineers Institution of Water and Environmental Management Malaysian Rubber Producers Research Association Mi
5、nistry of Defence RAPRA Technology Ltd. SATRA Footwear Technology Centre Amendments issued since publication Amd. No.DateComments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 04:49:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 903-A43:1990 BSI 03-1999i Con
6、tents Page Committees responsibleInside front cover National forewordii 1Scope1 2Normative references1 3Definitions1 4Principle1 5Apparatus1 6Test piece3 7Conditioning4 8Test conditions4 9Test procedure5 10Expression of results6 11Test report6 Annex A Explanatory notes8 Figure 1 Schematic diagram of
7、 the apparatus2 Figure 2 Path of test piece and swept area (shaded)3 Figure 3 Dumb-bell test piece4 Figure 4 Results in graphic form7 Publications referred toInside back cover Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 04:49:58 GMT+00:00 2006, Uncontrolled
8、Copy, (c) BSI BS 903-A43:1990 ii BSI 03-1999 National foreword This British Standard has been prepared under the direction of the Rubber Standards Policy Committee. This revision of Part A43 is identical with ISO 1431-1:1989 “Rubber, vulcanized or thermoplastic Resistance to ozone cracking Part 1: S
9、tatic strain test,” published by the International Organization for Standardization (ISO). This Part of BS 903 supersedes BS 903:1982 which is withdrawn. The generic title of BS 903 has been changed to “Physical testing of rubber” as many of the methods in the BS 903-A series are suitable for testin
10、g thermoplastic as well as vulcanized rubber. The change of title also anticipates the transfer of the methods in the Part B series to a separate standard for the chemical testing of rubber and the omission of the words “Methods for” anticipates the publication of a Part 0 “Introduction” and a “Guid
11、e to the selection and use of methods of test.” Amendments are not being issued to the other Parts of BS 903, but their titles are being changed when these Parts are revised. The major changes incorporated in this revision are as follows. a) Provision has been made for conducting tests, if required,
12、 at a velocity of flow of ozonized air of 600 100 mm/s (see 5.5). b) An alternative dumb-bell test piece has been added (see 6.3). c) An ozone concentration of 100 10 parts of ozone per hundred million parts of air by volume (pphm) has been included as one of the alternative test conditions (see 8.1
13、). WARNING NOTE ON TOXICITY Attention is drawn to the warning in clause 5. The recommendation that 10 pphm be regarded as an absolute maximum concentration in the surrounding atmosphere is in accordance with the value given for long term exposure (8 h TWA, Time Weighted Average, reference period) in
14、 Guidance Note EH 40/90 “Occupational exposure limits” published by the Health and Safety Executive, i.e. 0.1 ppm. NOTEGuidance Note EH 40/90 expresses occupational exposure limits in parts of ozone per million parts of air by volume (ppm). Units of pphm are used throughout this standard since this
15、is normal practice in the rubber industry. Attention is also drawn to Guidance Note EH 38/83, “Ozone health hazards and precautionary measures.” Cross-references International standardCorresponding British Standard ISO 471:1983BS 903 Methods of testing vulcanized rubber Part A35:1985 Temperatures, h
16、umidities and times for conditioning and testing of test pieces (Identical) ISO 1431-2:1982Part A44:1983 Determination of resistance to ozone cracking (dynamic strain test) (Identical) ISO 4661-1:1986Part A36:1988 Preparation of samples and test pieces (Identical) Licensed Copy: London South Bank Un
17、iversity, London South Bank University, Fri Dec 08 04:49:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 903-A43:1990 BSI 03-1999iii It is intended that the international standard for the reference method for estimating the ozone concentration (ISO 1431-3, as referred to in clause 1 and in 5.4), at
18、 present in preparation, will be implemented as a British Standard as BS 903-A45. Until the reference method for estimating the ozone concentration is published, any suitable titrimetric or instrumental method may be used, although it will not be possible to calibrate such methods against the refere
19、nce method. It is emphasized that details of the method of estimation of ozone concentration should be included in the test report see item c) 1 of clause 11). Additional information. In UK practice, the standard temperature is 23 C (see clause 7.1), and is commonly referred to as the “standard labo
20、ratory temperature”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages Thi
21、s document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licens
22、ed Copy: London South Bank University, London South Bank University, Fri Dec 08 04:49:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 04:49:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 1431-1:1989(E) BS
23、I 03-19991 1 Scope This part of ISO 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 a definite concentration of ozone and at a definite temperature in circumstances that exclud
24、e 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 according to conditions, especially ozone concentration and temperature, in addition, tests are ca
25、rried 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. Explanatory notes on the nature of ozone cracking are given in Annex A. Methods for determining resi
26、stance to ozone cracking under dynamic strain conditions and combined dynamic and static strain conditions are specified in ISO 1431-2. A reference method for estimating the ozone concentration will form the subject of ISO 1431-3. 2 Normative references The following standards contain provisions whi
27、ch, through reference in this text, constitute provisions of this part of ISO 1431. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO 1431 are encouraged to investigate the possibility of applying
28、 the most recent editions of the standards listed below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 471:1983, Rubber Standard temperatures, humidities and times for the conditioning and testing of test pieces. ISO 1431-2:1982, Rubber, vulcanized Resista
29、nce to ozone cracking Part 2: Dynamic strain test. ISO 4661-1:1986, Rubber, vulcanized Preparation of samples and test pieces - Part 1: Physical tests. 3 Definitions For the purpose of this part of ISO 1431, the following definitions apply. 3.1 threshold strain the highest tensile strain at which a
30、rubber can be exposed at a given temperature to air containing a given concentration of ozone without ozone cracks developing on it after a given exposure period threshold strain must be distinguished from limiting threshold strain, defined in 3.2 3.2 limiting threshold strain the tensile strain bel
31、ow 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, in a closed chamber at a constant temperature, to an atmosphere containing a fixed concentration of ozone. The tes
32、t pieces are examined periodically for cracking. Three alternative evaluation procedures are described for selected values of ozone concentration and exposure temperature: A Determination of the presence or absence of cracks, and if required, an estimate of the degree of cracking, after exposure for
33、 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 exposure period. 5 Apparatus (see Figure 1) WARNING Attention is drawn to the highly toxic nature of ozone. Efforts should b
34、e 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, it is recommended that 10 parts of ozone per hundred million parts of air of the surrounding atmosphere by volume be regarded as an absolute max
35、imum concentration whilst the maximum average concentration should be appreciably lower. NOTEAn exhaust vent to remove ozone-laden air is advised. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 04:49:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 1431-1:1989
36、(E) 2 BSI 03-1999 5.1 Test chamber This shall be a closed, non-illuminated chamber, thermostatically controlled to within 2 C 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 requireme
37、nts of 5.5 are 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) an ultra-violet lamp; b) a silent discharge tube.
38、The use of oxygen is necessary when using the discharge tube in order to avoid the formation of nitrogen oxides. The ozonized oxygen or air may be diluted with air to attain the required ozone concentration. Air used for generation of ozone or dilution shall first be purified by passing it over acti
39、vated 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 C. The ozonized air shall be fed from the source into the chamber via a heat exchanger to adjust its temp
40、erature 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-violet light source is used the amount of ozone produced can be controlled by adj
41、usting 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 voltage applied to the generator, the dimensions of the electrodes, the oxygen
42、 flow rate, or the diluent air flow rate. A two-stage dilution of the ozonized air can also be used. The adjustments shall be such that they will maintain the concentration within the tolerances given in 8.1. In addition, after each occasion that the test chamber is opened for insertion or inspectio
43、n 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 concentration specified for the test. Figure 1 Schematic diagram of the apparatus Licensed Copy: London South Bank University, L
44、ondon South Bank University, Fri Dec 08 04:49:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 1431-1:1989(E) BSI 03-19993 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 cont
45、ent shall be provided. The methods for estimating the ozone concentration will form the subject of ISO 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
46、/s and preferably to a value between 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 rat
47、e is the volume throughput of ozonized 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 rubber being used, the test con
48、ditions and other details of the test. As a general guide, it is recommended that the ratio of the exposed 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
49、 experimentally and, if necessary, 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 100 mm/s. NOTEThe 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 holdi