1、Designation: D3045 18Standard Practice forHeat Aging of Plastics Without Load1This standard is issued under the fixed designation D3045; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parenth
2、eses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope*1.1 This practice is intended to define the exposure condi-tions for
3、evaluating the thermal endurance of plastics whenexposed solely to hot air for extended periods of time. Only theprocedure for heat exposure is specified. The effect of elevatedtemperature on any particular property is determined byselection of the appropriate test method and test specimens forthat
4、property.1.2 This practice can be used as a guide to compare thermalaging characteristics of materials as measured by the change insome property of interest. The property of interest is measuredat room temperature.1.3 This practice recommends procedures for comparing thethermal aging characteristics
5、 of materials at a single tempera-ture. Recommended procedures for determining the thermalaging characteristics of a material using a series of elevatedtemperatures for the purpose of estimating endurance time to adefined property change at a lower temperature are alsodescribed; the applicability of
6、 the Arrhenius relation formaking predictions to other temperatures, is assumed in thiscase.1.4 This practice does not predict thermal aging character-istics where interactions between stress, environment,temperature, and time control failure occur.1.5 This standard does not purport to address all o
7、f thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.NOTE 1This standard and ISO-2578 address the same
8、subject matterbut differ in technical content.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the
9、 World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD5374 Test Methods for Forced-Convection Laboratory Ov-ens for Evaluation of Electrical InsulationD5
10、423 Specification for Forced-Convection Laboratory Ov-ens for Evaluation of Electrical InsulationE145 Specification for Gravity-Convection and Forced-Ventilation OvensE456 Terminology Relating to Quality and Statistics2.2 ISO Standards:3ISO 2578 (1993) Determination of Time-Temperature Lim-its After
11、 Exposure to Prolonged Action of HeatISO 9080 (2012) Plastic Piping and Ducting SystemsDetermination of the Long-Term Hydrostatic Strength ofThermoplastic Materials in Pipe Form by Extrapolation3. Terminology3.1 GeneralThe terminology given in Terminology D883and Terminology E456 is applicable to th
12、is practice. Terminol-ogy not in place is defined in 3.2.3.2 Definitions:3.2.1 continuous use temperature (CUT)the temperaturein degrees Celsius corresponding to a given thermal endurancetime for a given failure criterion (typically 50 % reduction inproperty), derived from the Arrhenius relation of
13、endurancetime and temperature, determined by heat aging at severalelevated temperatures. Several CUT values can exist, one foreach property, endurance time and endurance criterion.3.2.1.1 DiscussionIn practice, the continuous use tem-perature for a plastic, involves other environmental consider-atio
14、ns as discussed elsewhere in this standard, than thermal1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.50 on Durability of Plastics.Current edition approved Aug. 1, 2018. Published August 2018. Originallyapproved in 1974.
15、 Last previous edition approved in 2010 as D3045 92 (2010).DOI: 10.1520/D3045-18.2For referenced 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
16、 onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA
17、19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Te
18、chnical Barriers to Trade (TBT) Committee.1endurance alone. The term, CUT, used here, is intended as anindex for thermal endurance alone. The use of this term isfound in automotive applications of plastics. The endurancetime used for the CUT value reported should be specified asCUT (endurance time).
19、3.2.2 temperature index (TI), also referred to as thermalindex (TI)the temperature in degrees Celsius correspondingto an endurance time of 20,000 hours for a given failurecriterion (typically 50% reduction in property), derived fromthe Arrhenius relation of endurance time and temperature,usually det
20、ermined by heat aging at several elevated tempera-tures.3.2.2.1 DiscussionThe TI can thus be seen as a specialcase of CUTwhere the endurance time is fixed at 20,000 hours.Agiven plastic material and property and its retention criterionmay be characterized by several CUT times, for example, CUT(1000
21、hours), CUT (5000 hours), etc. as needed per require-ments of different applications. Further, several TI values canexist, one for each property and endurance criterion.4. Significance and Use4.1 The use of this practice presupposes that the failurecriteria selected to evaluate materials (that is, t
22、he property orproperties being measured as a function of exposure time) andthe duration of the exposure can be shown to relate to theintended use of the materials.4.2 Plastic materials exposed to heat are subject to manytypes of physical and chemical changes. The severity of theexposures in both tim
23、e and temperature determines the extentand type of change that takes place. A plastic material is notnecessarily degraded by exposure to elevated temperatures.However, extended periods of exposure of plastics to elevatedtemperatures will generally cause some degradation, withprogressive changes in p
24、hysical properties. Specific propertiesand failure (or lifetime) criteria for these properties aretypically chosen for the evaluation of thermal endurance.4.3 Generally, short exposures at elevated temperaturesdrive out volatiles such as moisture, solvents, or plasticizers,relieve molding stresses,
25、advance the cure of thermosets, andmay cause some change in color of the plastic or coloringagent, or both. Normally, additional shrinkage should beexpected with loss of volatiles or advance in polymerization.4.4 Some plastic materials become brittle due to loss ofplasticizers after exposure at elev
26、ated temperatures. Othertypes of plastics become soft and sticky, either due to sorptionof volatilized plasticizer or due to breakdown of the polymer.4.5 The degree of change observed will depend on theproperty measured. Different properties, mechanical orelectrical, may not change at the same rate.
27、 For instance, thearc resistance of thermosetting compounds improves up to thecarbonization point of the material. Mechanical properties,such as flexural properties, are sensitive to heat degradationand may change at a more rapid rate. Ultimate properties suchas strength or elongation are more sensi
28、tive to degradation thanbulk properties such as modulus, in most cases.4.6 The material studied can change inherent behavior withchange in temperature as for example when crossing , , and transitions. These transitions should be avoided both in therange of aging temperatures used, as well as in extr
29、apolation ofthe lifeline. Arrhenius principles may only be used to acceler-ate a chemical mechanism if there are no fundamental changesin the material properties. With semi-crystalline and highlycrystalline polymers, elevated temperatures may cause signifi-cant changes to the morphology of the mater
30、ial, invalidating orcompromising that assumption.NOTE 2Caution should be exercised in using the Arrhenius relationand knowledge of physical changes in the material at elevated tempera-tures is important. Guidance given in ISO 9080 for characterizing lifetimeof plastic materials in pipe form by extra
31、polation suggests that the highestoven aging temperature should be at least 15C lower than the Vicatsoftening temperature for glassy amorphous polymers, and at least 15Clower than the melting point for semi-crystalline polymers.4.7 Effects of exposure can be quite variable, especiallywhen specimens
32、are exposed for long intervals of time. Factorsthat affect the reproducibility of data are the degree oftemperature control of the enclosure, humidity of the oven, airvelocity over the specimen, and period of exposure. Errors inexposure are cumulative with time. Certain materials aresusceptible to t
33、he influence of humidity.4.8 It is not to be inferred that comparative material rankingis undesirable or unworkable. On the contrary, this practice isdesigned to provide data which can be used for such compara-tive purposes. However, the data obtained from this practice,since it does not account for
34、 the influence of stress orenvironment that is involved in most real life applications,must be used cautiously by the designer, who must inevitablymake material choices using additional data such as creep andcreep rupture that are consistent with the requirements of thespecific application.4.9 It is
35、 possible for many CUT and TI values to exist.Therefore, for any application of the CUT or the TI (tempera-ture index) to be valid, either the thermal aging program mustduplicate the intended thermal exposure conditions of the endproduct, or the Arrhenius relation must apply.4.10 There can be very l
36、arge errors whenArrhenius plots orequations based on data from experiments at a series oftemperatures are used to estimate time to produce a definedproperty change at some lower temperature. This estimate oftime to produce the property change or “failure” at the lowertemperature is often called the
37、“service life;” however, usingthis term should be avoided as this implies the tester hasinformation on specific failure criteria in end-use, whilenumerous factors are not under the scope of this test. It ispreferable to use terms such as “end point,” “thermal endur-ance time,” and such. Because of t
38、he errors associated withthese calculations, this endurance time should be considered as“maximum expected” rather than “typical.”5. Apparatus5.1 Provisions for conditioning at specified standard condi-tions.5.2 OvenA controlled horizontal or vertical air flow oven,employing forced-draft circulation
39、with substantial constantfresh air intake is recommended. To harmonize with ISO 2578D3045 182and IEC standards, it is preferable to use ovens that complywith the set temperature, temperature variation and air changerequirements of Specification D5423 as evaluated by the testmethods of Test Methods D
40、5374. Alternatively, SpecificationE145 may be used, with Specification E145, Type IIB ovensfor aging temperatures up to 70C, and Specification E145,Type IIA ovens for higher temperatures. Indicate the specificoven standard used in the test report.5.3 Test Equipment to determine the selected property
41、 orproperties, in accordance with appropriate ASTM procedures.6. Sampling6.1 Use the number and type of test specimens required bythe applicable test method each time the specific property isdetermined.7. Test Specimens7.1 Use the number and type of test specimens required bythe applicable test meth
42、od each time the specific property isdetermined.7.2 The specimen thickness should be comparable to but nogreater than the minimum thickness of the intended applica-tion.7.3 If possible, fabricate test specimens by the same methodas used in the intended application.8. Conditioning8.1 Conduct all test
43、s in the standard laboratory atmosphereas specified in Practice D618, Method A, and with specimensconditioned in accordance with the requirements of the testmethod for determining the specific property or propertiesrequired.8.2 Condition specimens following exposure at elevatedtemperature in the sta
44、ndard laboratory atmosphere as describedin 8.1 prior to testing.8.3 If possible, avoid simultaneous aging of mixed groupsof different compounds which might cause cross contaminationfrom off-gassing during heat aging.9. Procedure9.1 If possible, for each specific test and temperature, allmaterials mu
45、st be exposed for the same time in the same oven(caution: see 8.3). In case of a single temperature study, usesufficient number of replicates of each material for eachexposure time so that results of tests used to characterize thematerial property can be compared by analysis of variance orsimilar st
46、atistical data analysis procedure.9.2 When testing at a series of temperatures in order todetermine the relationship between a defined property changeand temperature, use a minimum of four exposuretemperatures, covering a range adequate for extrapolation ofthe time-temperature relation. The followin
47、g procedures arerecommended for selecting four exposure temperatures:9.2.1 The lowest temperature should produce the desiredlevel of property change or product failure after at least 5000hours of exposure.9.2.2 The highest temperature should produce the desiredlevel of property change or product fai
48、lure after at least 500hours of exposure.9.2.3 When possible, select the exposure temperatures fromTable 1 (taken from the list of standard temperatures in PracticeD618). If the suggested heat aging times in 9.2.1 and 9.2.2 arefollowed, then the exposure times (Schedules A, B, C, and D)are recommend
49、ed to be used.9.2.4 The purpose of Table 1 showing time schedules atspecific temperatures is to show a typical heat aging schedulefor a particular property of some material. In practice it is oftendifficult to estimate the effect of heat aging before obtainingtest data. Therefore, it is usually necessary to start only theshort-term heat aging at one or two temperatures until data areobtained to be used as a basis for selecting the remainder of theTABLE 1 Suggested Temperatures and Exposure Times for the Determination of Heat Aging of PlasticsSuggestedExposureTemperat
