1、DEUTSCHE NORM March 2000 ICs 83.060 Prfung von Kautschuk und Elastomeren - Knstliche Alterung Supersedes October 1993 edition In keeping with current practice in standards published by the International Organization for Standardization (ISO), a comma has been used throughout as the decimal marker. F
2、oreword This standard has been prepared by Technical Committee Prfung der physikalischen Eigenschaften von Kautschuk und Elastomeren of the Normenausschuss Materialprfung (Materials Testing Standards Com- mitt ee) . The standard is based on IS0 188, from which it differs in the following points: - i
3、t gives a different flow velocity for the oven with forced air circulation; - it recommends testing certain properties using type S 2 dumb-bell test pieces; - it recommends test temperatures and duration; - it includes formulae for calculating standard deviations, the variation coefficient and confi
4、dence interval. Amendments This standard differs from the October 1993 edition in that references have been updated and the standard has been editorially revised. Previo us edit ions DIN DVM 3508 = DIN 53508: 1939-02, 1954-12, 1960-05, 1977-07, 1993-10. 1 Scope The test methods specified in this sta
5、ndard serve to determine the resistance of rubber to deterioration by subjecting test pieces to accelerated ageing (either by heating them in air at atmospheric pressure or in oxygen at an elevated pressure). Various physical properties are measured at standard laboratory temperature before and afte
6、r testing, and the relative or absolute differences are used to estimate the relative service life of the rubber. The methods described in this standard are not suitable for assessing the effects of light or ozone on the deterioration of rubber. Continued on pages 2 to 6. Translation by DIN-Sprachen
7、dienst. In case of doubt, the German-language original should be consulted as the authoritative text. No pari of this translation may be reproduced without the prior permission of V Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany, s the exclusive right of sale f
8、or German Standards (DIN-Normen). Ref. No. DIN 53508 : 2000-0 English price group 06 Sales No. 0106 07.00 Page 2 DIN 53508 : 2000-03 2 Normative references This standard incorporates, by dated or undated reference, provisions from other publications. These norma- tive references are cited at the app
9、ropriate places in the text, and the titles of the publications are listed below. For dated references, subsequent amendments to or revisions of any of these publications apply to this standard only when incorporated in it by amendment or revision. For undated references, the latest edition of the p
10、ublication referred to applies. DIN 5001 1-2 Testing of materials, components and equipment - Ovens - Conditioning of test pieces DIN 5001 1-1 2 Artificial climates in technical applications - Air temperature as a climatological quantity in controlled-atmosphere test installations DIN 5001 4 Artific
11、ial climates in technical applications - Standard atmospheres DIN 50035-1 Concepts relating to the ageing of materials - Basic concepts DIN 50035-2 Concepts relating to the ageing of materials - Polymer materials DIN 53504 Determination of tensile stresshtrain properties of rubber DIN 53505 Shore A
12、and D hardness testing of rubber and plastics DIN 5351 9-1 Determination of indentation hardness (IRHD) of soft rubber using standard specimens DIN 53598-1 Statistical evaluation of random samples with examples from tests on elastomers and plastics DIN EN IS0 2578 Plastics - Determination of time-te
13、mperature limits after prolonged exposure to heat (IS0 2578 : 1993) IS0 5725-1 : 1994 Accuracy (trueness and precision) of measurement methods and results - Part 1 : General principles and definitions IS0 5725-2 : 1994 Accuracy (trueness and precision) of measurement methods and results - Part 2: Ba
14、sic method for the determination of repeatability and reproducibility of a standard measure- ment method Technische Regeln fr Druckbehalter (TRB) (Codes of practice for pressure vessels) Unfallverhtungsvorschrift Sauerstoff (Accident prevention regulation on the use of oxygen) (VBG 62) Druckbehalter
15、verordnung (German Pressure Vessels Regulation), BGBI. (German Federal Law Gazette) I, 1989, NO. 20, pp. 843-869 3 Concept Accelerated ageing is a test method by means of which the expected deterioration of rubber in practical applications is ascertained by subjecting test pieces to accelerated dete
16、riorating influences (e.g. elevated temperatures, or, in some cases, elevated oxygen pressures). 4 Test methods In order to effectively assess its resistance to ageing, the intended service applications of the rubber should be considered, and test methods and conditions which approximate service con
17、ditions should be selected. Only those properties relevant to application in service shall be determined; in most cases, these will be tensile strength at break, elongation at break, stresshtrain values (see DIN 53504) and hardness (see DIN 53505 or Note that test results, especially those obtained
18、from long-term testing, cannot be compared when different types of ovens (.e. with either forced or natural air circulation) are used. Two methods of accelerated ageing are described in this standard. 4.1 Ageing in air at atmospheric pressure in one of the three following oven types, of which the ov
19、en described in subclause 4.1.1 is to be given preference. 4.1.1 Air oven with forced air circulation (air recirculation system with fresh air supply) (see subclause 6.2). 4.1.2 Air oven with natural air circulation (see subclause 6.3). 4.1.3 Cell-type oven (see subclause 6.4). 4.2 DIN 53519-1). Age
20、ing in oxygen at an elevated pressure (see subclause 6.5). 5 Test pieces Accelerated ageing shall be carried out on test pieces prepared and conditioned as specified in the standards relevant to the appropriate property tests. The number of test pieces shall also be in accordance with these standard
21、s. Page 3 DIN 53508 : 2000-03 Test pieces shall be measured before testing. Only pieces of identical dimensions shall be compared with each other. It is recommended that tests be carried out on type S 2 dumb-bell test pieces which are triple-layered and (2 I0,2) mm thick, as specified in DIN 53504.
22、Marking (e.g. applying gauge lines for measuring elongation) shall be carried out after heating as inks can affect ageing. 6 Apparatus 6.1 General In addition to meeting the requirements listed below, ovens shall be designed so that test pieces do not come in contact with any parts containing copper
23、 or copper alloys, as these materials may accelerate the ageing process. It is essential that the temperature tolerances specified in subclause 7.2 be observed and that temperatures remain constant throughout the oven chamber or cell. Temperatures shall be measured in close proximity to the test pie
24、ce. NOTE: The type of oven to be used will be specified in all relevant test documents. 6.2 Air oven with forced air circulation to DIN 5001 1-12 Ovens with forced air circulation include a recirculation system with fresh air supply. The air shall be preheated to operating temperature, shall circula
25、te at not less than thirty changes per hour, and shall flow at a rate between 0,25 m/s and 3 m/s. 6.3 Air oven with natural air circulation to DIN 50011-12 For ovens with natural air circulation, thermostatic control is necessary in order to maintain a constant, evenly distributed temperature within
26、 the specified range throughout the heating period. Aluminium chamber or cell walls also help achieve temperature consistency. The temperature must nevertheless be monitored at regular intervals during the ageing period. The air shall circulate at no less than three and no more than ten changes per
27、hour, with the air velocity being scarcely measurable (e.g. less than 2 mm/s). Sliding vents shall have no more than a slight effect on this rate. 6.4 Cell-type oven Cell-type ovens shall comprise one or more unconnected cylindrical, vertical cells having a minimum height of at least 300 mm in which
28、 the temperature can be kept constant and through which the air circulates at not less than three and not more than ten changes per hour. Cells shall be surrounded by a good heat transfer medium. NOTE: The flow velocity necessary to maintain the specified air circulation rate can be estimated based
29、on the number of cells and their volume, and shall be controlled by means of a flowmeter. Air shall circulate uniformly in all cells. 6.5 Pressure chamber Pressure chambers shall consist of a vessel made of stainless steel or another suitable material, and shall be surrounded by a heat transfer medi
30、um which does not react with oxygen. The chamber shall meet all safety requirements specified in the Druckbehlterverordnung, the Technische Regeln fr Druckbehlter and the Unfallverhtungsvorschrift Sauerstoff. It shall be equipped with a bursting disc to prevent the permissible pressure from being ex
31、ceeded in the case of an extreme reaction between the test material and oxygen. 7 Procedure 7.1 General 7.1.1 Test pieces shall be conditioned and stored in DIN 5001 4 - 23/50-2 standard atmosphere. 7.1.2 Test pieces shall be tested no earlier than 16 hours and no later than four weeks after vulcani
32、zation. If this requirement cannot be met, especially when testing finished products, testing shall begin no laterthan three months after vulcanization. If this is not possible, or when material is to be tested for which the production date is unknown, testing shall begin within two months of delive
33、ry to the customer. Once the accelerated ageing process has been completed and before testing, test pieces shall be conditioned for no less than 16 hours and no more than six days in DIN 5001 4 - 23/50-2 standard atmosphere. 7.1.3 Ovens shall be brought to test temperature before test pieces are ins
34、erted, and the temperature mea- sured at the location for the test piece. Test pieces shall be free from strain, protected from light, and exposed to the air and/or oxygen on all sides. The pieces shall be suspended so they are at least 1 O mm from each other Page 4 DIN 53508 : 2000-03 and 1 O mm (f
35、or cell-type ovens and pressure chambers) or 50 mm (for air ovens) from the oven walls. Test pieces shall occupy no more than 1 O YO of the oven chamber or cell volume. Where rubber compounds contain volatile substances, only similar compounds shall be aged simultaneously in the same oven or cell. 7
36、.2 Test temperatures and duration Test temperatures and duration are to be selected based on the type of rubber under examination and the expected service conditions. 7.2.1 The following test temperatures and periods are recommended: Ageing in air as in subclause 4.1 (70 Il) “C for 7 days; (1 O0 I 1
37、) “C for 3 or 7 days. test temperatures: (85 I 1) “C, (1 25 12) “C, (1 50 12) “C, (1 75 12) “C, (200 I 2) “C, (250 13) “C; test periods: 1, 3, 7, or 1 O days, or a multiple of 7 days. In special cases, the following temperatures and periods may be used in any combination: 7.2.2 Ageing in oxygen The
38、following conditions are recommended: oxygen pressure: (21 Il) bar; test temperature: (70 I 1) “C; test duration: (24-;) hours, or a multiple thereof. 8 Expression of results Results shall be expressed in accordance with the appropriate standards for each property test. Calculate the arithmetic mean
39、 or median of all single values for each property, E, before ageing, E, and after ageing, E,. Calculate the percentage change, Z, for each property (except hardness) using equation (1): The absolute change in hardness, Z, is to be expressed as a difference calculated from equation (2): Z,=EA-E O The
40、 standard deviation for Z, sz, shall be calculated from equation (3) (see DIN 53598-1): sz = -(u;, EA A + u;, or/2 EO or, if uE, A = uE, o = u, approximated using equation (4): where are the mean values for each property before and after ageing; are the coefficients of variation, as a percentage, fo
41、r property E before and after ageing. 5 EO uE, A, uE, o The standard deviation for Z, shall be calculated from equation (5): or, if sE, A = sE, o = s, approximated using equation (6): 7 sz=sy2 (3) where s,; sE, o are the standard deviations of single values for property E (hardness) before and after
42、 ageing. Page 5 DIN 53508 : 2000-03 The standard deviation can then be used to determine the confidence interval for a confidence level of 95 YO, as well as the coefficient of variation for Z, uZ, (see DIN 53598-1). NOTE: The percentage changes for each property and the duration of the heating proce
43、ss at several tempera- tures may be used to determine either the activation energy (using an Arrhenius plot), or the time-tempera- ture limits (as described in DIN EN IS0 2578). 9 Precision Repeatability limits and reproducibility limitsforthe relative changes in selected properties (elongation at b
44、reak, tensile strength at break, stress at 1 O0 YO strain) afterageing, and the absolute change in Shore A hardness after ageing are given in table 1. Table 2 gives the characteristic relative repeatability limits and reproducibility limits (for hardness, the absolute limits) for single values after
45、 ageing. In both tables, the arithmetic means for three types of vulcanizates are also included (see clause 8). The difference between two single test results obtained by the same operator using the same equipment on identical test material within a short period of time will not normally exceed the
46、repeatability limit, r, more than once in 20 cases. The difference between two single and independent test results obtained by two operators working in different laboratories on identical test material will not normally exceed the reproducibility limit, R, more than once in 20 cases. The data relati
47、ng to precision were obtained in a national interlaboratory test which was carried out in 1989 and involved 17 rubber industry laboratories. Three types of vulcanizates were tested in ovens with forced air circulation over periods of three and seven days at two different temperatures each (NR and NB
48、R at 70 “C and 1 O0 “C, EPDM at 1 O0 “C and 125 OC). Elongation at break, tensile strength at break, stress at 1 O0 YO strain and Shore A hardness were measured before and after ageing. Hardness was measured on 36 mm diameter discs, as well as on type S 2 dumb-bell test pieces (2 mm thick, triple-la
49、yered). No significant difference between the test results for each test piece type was reported. The test was organized and evaluated as specified in IS0 5725-2. 10 Test report The test report shall refer to this standard and include the following details: a) type and designation of rubber tested; b) time between vulcanization and testing; c) type and dimensions of test pieces; d) position of test pieces in the product; e) ageing method and type of oven or pressure chamber used; f) temperature and duration of ageing process; g) values for each property before and after agein
