1、Designation: D 454 04Standard Test Method forRubber Deterioration by Heat and Air Pressure1This standard is issued under the fixed designation D 454; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numb
2、er in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method covers a procedure to determine theinflu
3、ence of elevated temperature and air pressure on thephysical properties of vulcanized rubber. The results of this testmay not give an exact correlation with service performancesince performance conditions vary widely. The test may,however, be used to evaluate rubber compounds on a labora-tory compar
4、ison basis. It will be most applicable to perfor-mance under conditions of increased temperature and airpressure.NOTE 1For evaluating rubber vulcanizates under less severe condi-tions that more nearly approach natural aging, the use of Test MethodsD 573 and D 865 is recommended.1.2 The values stated
5、 in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and
6、health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 15 Methods of Compound and Sample Preparation forPhysical Testing of Rubber Products3D 412 Test Methods for Vulcanized Rubber and Thermo-plastic ElastomersTensionD 57
7、2 Test Method for RubberDeterioration by Heat andOxygenD 573 Test Method for RubberDeterioration in an AirOvenD 865 Test Method for RubberDeterioration by Heatingin Air (Test Tube Enclosure)D 3182 Practice for RubberMaterials, Equipment, andProcedures for Mixing Standard Compounds and Prepar-ing Sta
8、ndard Vulcanized SheetsD 3183 Practice for RubberPreparation of Pieces for TestPurposes from ProductsD 4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustries3. Summary of Test Method3.1 Specimens of vulcanized rubber are exposed to thed
9、eteriorating influence of air at specified elevated temperatureand pressure for known periods of time, after which theirphysical properties are determined. These are compared withthe properties determined on the original specimens and thechanges noted.3.2 Unless otherwise specified, the determinatio
10、n of thephysical properties shall be carried out in accordance with TestMethods D 412.3.3 Except as may be otherwise specified in this testmethod, the requirements of Practices D 3182 and D 3183 shallbe complied with and are made part of this test method.3.4 In case of conflict between the provision
11、s of this testmethod and those of detailed specifications or test methods fora particular material, the latter shall take precedence.4. Significance and Use4.1 Rubber and rubber products must resist the deteriorationof physical properties with time caused by oxidative andthermal aging. This test met
12、hod allows these performanceproperties to be determined under the accelerated conditions ofhigh air pressure and at elevated temperatures.4.2 Refer to the Annex in Test Method D 573 for importantinformation on standard compounds used for precision testingfor accelerated test aging evaluation.1This t
13、est method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.15 on Degradation Tests.Current edition approved July 1, 2004. Published July 2004. Originally approvedin 1952. Last previous edition approved in 1999 as D 454 99.2For referenced
14、ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
15、 West Conshohocken, PA 19428-2959, United States.5. Apparatus5.1 Air-Pressure Chamber, consisting of a metal vesseldesigned to maintain an internal atmosphere of air underknown pressure, with provisions for placing rubber specimenswithin it and subjecting them to controlled uniform tempera-ture. The
16、 equipment shall conform to the following require-ments:5.1.1 The size and shape of the chamber shall be optional,but shall be such that the specimens may be suspended thereinvertically without undue crowding and without touching eachother or the sides of the chamber.5.1.2 The operating temperature
17、shall be 125 6 1C (257 61.8F) determined as described in 5.1.5. The temperature shallbe automatically controlled by means of thermostatic regula-tion.5.1.3 The source of heat is optional, but if located inside theaging chamber, shielding shall be provided so that directradiation cannot reach the spe
18、cimens. The temperature of theshield surfaces shall be within 1C of the air temperature.5.1.4 The heating medium is optional. Steam, air, or liquidmedia may be used. If air is used, the heated air shall bethoroughly circulated by means of mechanical agitation, andbaffles shall be used as required to
19、 prevent local overheatingand dead spots. Oils or other combustible organic fluids may behazardous at the elevated temperature required, but if their useis necessary, they must have a flash point not lower than 200C.For any one type of heat-transfer medium, complete immersionof the pressure vessel i
20、n the heating medium is recommendedfor referee purposes in order to assure uniformity of tempera-ture inside the vessel.5.1.5 To make certain that the operating temperature re-mains within the limits specified in 5.1.2, the temperatureshould be automatically recorded over the entire test periodusing
21、 a temperature measuring device capable of measurementwithin 1C of the specified temperature. For apparatus notequipped with automatic recording capabilities, temperatureshould be measured with sufficient frequency to ascertain thatthe temperature limits specified in 5.1.2 are adhered to. If thepres
22、sure chamber is not completely immersed, the sensingelement shall be placed in a thermometer well extending intothe pressure chamber. The thermometer well should be filledwith a nonvolatile liquid to a depth sufficient to cover thesensitive element, in order to facilitate heat transfer. In anycase,
23、it is desirable to verify the recorded temperature, and theuniformity of temperature distribution at different points withinthe pressure chamber, by checking with a temperature-indicating device having its sensitive element directly exposedto the air within the pressure chamber. If the pressure cham
24、beris completely immersed, the temperature may be taken as thatof the heating medium. The sensitive element of thetemperature-measuring device shall be close to the pressurechamber, but not touching it.5.1.6 The apparatus and method of heating shall be sodesigned that the interval required for the c
25、hamber to reach theoperating temperature at the beginning of a test shall be asshort as possible. By proper precautions, this lag may bereduced to less than 5 % of the usual minimum exposureperiods. Provision shall also be made for rapid closing andopening of the apparatus for introduction or remova
26、l ofspecimens.5.1.7 The air pressure shall be maintained at 550 6 14 kPa(80 6 2.0 psi) during the exposure periods. Automatic regula-tion is recommended.5.1.8 Suitable provision shall be made by separation, filtra-tion, or otherwise for removal of oil, dirt, and moisture fromthe air entering the pre
27、ssure chamber. Care shall also be takento avoid any other introduction of oil or grease into the pressurechamber.5.1.9 No copper or brass parts shall be exposed to theatmosphere used in the pressure chamber.5.1.10 The pressure chamber shall be equipped with areliable safety valve or rupture diaphrag
28、m set for release at apressure of not more than 1380 kPa (200 psi).NOTE 2Caution: Adequate safety provisions are important whenheating oxidizable organic materials in air under pressure, since the rate ofoxidation may become very rapid in some cases, particularly if a largesurface area is exposed. I
29、f the same equipment is used for the air-pressureheat test and the oxygen-pressure test in accordance with Test MethodD 572, combustible heating media should not be used.6. Sampling6.1 The sample size shall be sufficient to allow for thedetermination of the original properties on three specimens and
30、also on three or more specimens for each exposure period ofthe test. At least 24 h must elapse between completion of thevulcanization of the samples and the start of the aging test.6.2 When minimum requirements are specified, one test onthree dumbbells shall be considered sufficient. But if the resu
31、ltsare below the specified requirements, two additional specimensshall be prepared from the original sample and tested. Shouldthe results of either of these tests be below the specifiedrequirements, the sample shall be considered to have failed tomeet the specifications.6.2.1 The two additional spec
32、imens indicated in 6.2 mayoptionally be prepared and exposed simultaneously with thefirst three specimens exposed. They need not be tested if themedian values of the first three specimens exposed and testedmeet the minimum requirements. Testing five specimens is thenorm for referee tests in accordan
33、ce with 10.1.2.7. Test Specimens7.1 Dumbbell-shaped specimens prepared in accordancewith Test Methods D 412 shall be considered standard. Theirform shall be such that no mechanical, chemical, or heattreatment will be required after exposure in the pressurechamber. If any adjustments, that is, to thi
34、ckness are necessary,they shall be performed prior to exposure.7.2 The cross-sectional dimensions of test specimens forcalculating the physical properties shall be measured prior toexposure in the aging chamber. Gage lines used for measuringelongations shall be applied after the specimens have beena
35、ged. Only specimens of similar dimensions having approxi-mately the same exposed areas may be compared with eachother.D4540428. Tests of Original Specimens8.1 The stress-strain properties or tensile strength and ulti-mate elongation, and any other required properties of theoriginal unaged specimens
36、shall be determined within 96 h ofthe start of the aging period. Results on specimens that arefound to be imperfect shall be discarded, and retests shall bemade.8.2 When rubber compounds are to be tested for the purposeof determining compliance with specifications, it shall bepermissible to determin
37、e the original properties required in 8.1simultaneously with the determination of the values after thefirst aging period, even though the elapsed time exceeds 96 h.9. Procedure9.1 Suspend the specimens for exposure vertically in thepressure chamber after it has been preheated to the operatingtempera
38、ture. It is recommended that not more than 10 % of thevolume of the pressure chamber be occupied by an oxidizablesubstance. Avoid simultaneous exposure of a mixed group ofdifferent compounds, if possible. For instance, high-sulfurcompounds should not be exposed with low-sulfur compounds,nor those co
39、ntaining antioxidants with those that do not, sincesome migration is known to occur under the conditions of thetest.9.2 Consider the exposure period to start when the speci-mens are placed in the heated chamber, after which close thechamber immediately and apply air pressure. This entireoperation sh
40、all not take longer than 3 min. However, keep arecord of the time interval elapsing from the starting time untilthe temperature of the chamber reaches 125C (257F). If thisinterval exceeds 5 % of the total exposure time, make approxi-mate correction by adding one half of the interval to theexposure p
41、eriod. The exposure shall be continuous for thespecified time without pressure reduction or opening of thechamber for introduction or removal of specimens.9.3 Select suitable periods of exposure depending on therate of deterioration of the particular material being tested. Theperiods shall be such t
42、hat the deterioration will not be so greatas to prevent determination of the final physical properties.Intervals frequently used are 3, 5, 8, 12, 20, and 30 h. Inexperimental work, it is desirable to employ a range of periodsso as to determine the rate of deterioration, but for routine testsof known
43、 materials and for purchase acceptance purposes,fewer intervals or even a single period may suffice.9.4 At the termination of the exposure period, release the airpressure gradually, this operation requiring at least 5 min toavoid possible formation of porosity in the specimens. Removespecimens from
44、the pressure chamber immediately. Cool thespecimens to room temperature on a flat surface and allow torest not less than 16 nor more than 96 h before determinationof the physical properties. Apply gage lines used for measuringelongations to the specimens.10. Physical Tests of Exposed Specimens10.1 D
45、etermine the tensile stress at a specified elongation,or tensile strength and ultimate elongation, or both, of thespecimens exposed for different periods as the intervals termi-nate, except that it shall be permissible to accumulate speci-mens for testing together when this does not conflict with th
46、especified rest period. In determining the physical propertiesafter aging, the final values shall be the median of results fromthree specimens, except that under the following conditions,two additional specimens shall be exposed and tested and themedian of the values for the five specimens shall be
47、used:10.1.1 If one or more values do not meet the specifiedrequirements when testing the compliance with specifications.10.1.2 If referee tests are being made. After completion ofthe tests, the broken specimens shall be examined visually andmanually and their condition noted.11. Calculations11.1 Exp
48、ress the results of the air pressure heat test for eachexposure period as a percentage change in each physicalproperty (tensile strength, ultimate elongation, or tensile stress)calculated as follows:P 5A 2 OO3 100 (1)where:P = percentage change in property,O = original value, andA = value after agin
49、g or exposure.In this type of expression, negative percent values indicate areduction in the value of the property.12. Report12.1 The report shall include the following results calcu-lated in accordance with Section 10.12.1.1 All observed are recorded data on which the calcu-lations are based,12.1.2 Description of the apparatus,12.1.3 The exposure period,12.1.4 Statement of condition of exposed specimens,12.1.5 Dimensions of test specimens,12.1.6 The duration, temperature, and date of vulcanizationof the rubber, if known, and12.1.7 Dates of original and final determinat
