1、Designation: D 3045 92 (Reapproved 2003)Standard Practice forHeat Aging of Plastics Without Load1This standard is issued under the fixed designation D 3045; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 A number 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 practice is intended to define the exposure c
3、ondi-tions for testing the resistance of plastics to oxidation or otherdegradation when exposed solely to hot air for extendedperiods of time. Only the procedure for heat exposure isspecified, not the test method or specimen. The effect of heaton any particular property may be determined by selectio
4、n ofthe appropriate test method and specimen.1.2 This practice should be used as a guide to comparethermal aging characteristics of materials as measured by thechange in some property of interest. This practice recommendsprocedures for comparing the thermal aging characteristics ofmaterials at a sin
5、gle temperature. Recommended proceduresfor determining the thermal aging characteristics of a materialat a series of temperatures for the purpose of estimating time toa defined property change at some lower temperature are alsodescribed.1.3 This practice does not predict thermal aging character-isti
6、cs where interactions between stress, environment, tempera-ture, and time control failure occurs.1.4 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 health
7、practices and determine the applica-bility of regulatory limitations prior to use.NOTE 1ISO-2578 is considered to be technically equivalent to thispractice.2. Referenced Documents2.1 ASTM Standards:2D 573 Test Method for RubberDeterioration in an AirOvenD 618 Practice for Conditioning Plastics for T
8、estingD 883 Terminology Relating to PlasticsD 1870 Practice for Elevated Temperature Aging Using aTubular Oven3D 1898 Practice for Sampling of Plastics3E 145 Specifications for Gravity-Convection and Forced-Ventilation OvensE 456 Terminology Relating to Quality and Statistics2.2 ISO Standard:ISO 257
9、8 (1974) Determination of Time-Temperature Lim-its After Exposure to Prolonged Action of Heat43. Terminology3.1 The terminology given in Terminology D 883 and Ter-minology E 456 is applicable to this practice.4. Significance and Use4.1 The use of this practice presupposes that the failurecriteria se
10、lected to evaluate materials (that is, the 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 may be subject tomany types of physical and chemical change
11、s. The severity ofthe exposures in both time and temperature determines theextent and type of change that takes place. A plastic material isnot necessarily degraded by exposure to elevated temperatures,but may be unchanged or improved. However, extendedperiods of exposure of plastics to elevated tem
12、peratures willgenerally cause some degradation, with progressive change inphysical properties.4.3 Generally, short exposures at elevated temperatures maydrive out volatiles such as moisture, solvents, or plasticizers,relieve molding stresses, advance the cure of thermosets, andmay cause some change
13、in color of the plastic or coloringagent, or both. Normally, additional shrinkage should beexpected with loss of volatiles or advance in polymerization.1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.50 on Durability of Pl
14、astics.Current edition approved March 10, 2003. Published April 2003. Originallyapproved in 1974. Last previous edition approved in 1997 as D 3045 92 (1997).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of AS
15、TMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
16、PA 19428-2959, United States.4.4 Some plastic materials may become brittle due to loss ofplasticizers after exposure at elevated temperatures. Othertypes of plastics may become soft and sticky, either due tosorption of volatilized plasticizer or due to breakdown of thepolymer.4.5 The degree of chang
17、e observed will depend on theproperty measured. Different properties, mechanical or electri-cal, may not change at the same rate. For instance, the arcresistance of thermosetting compounds improves up to thecarbonization point of the material. Mechanical properties,such as flexural properties, are s
18、ensitive to heat degradationand may change at a more rapid rate. Ultimate properties suchas strength or elongation are more sensitive to degradation thanbulk properties such as modulus, in most cases.4.6 Effects of exposure may be quite variable, especiallywhen specimens are exposed for long interva
19、ls 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 degradation due to the influe
20、nce of humidity inlong-term heat resistance tests. Materials susceptible to hy-drolysis may undergo degradation when subjected to long-termheat resistance tests.4.7 It is not to be inferred that comparative material rankingis undesirable or unworkable. On the contrary, this practice isdesigned to pr
21、ovide data which can be used for such compara-tive purposes. However, the data obtained from this practice,since it does not account for the influence of stress orenvironment that is involved in most real life applications,must be used cautiously by the designer, who must inevitablymake material cho
22、ices using additional data such as creep andcreep rupture that are consistent with the requirements of hisspecific application.4.8 It is possible for many temperature indexes to exist, infact, one for each failure criterion. Therefore, for any applica-tion of the temperature index to be valid, the t
23、hermal agingprogram must duplicate the intended exposure conditions ofthe end product. If the material is stressed in the end product ina manner not evaluated in the aging program, the temperatureindex thus derived is not applicable to the use of the materialin that product.4.9 There can be very lar
24、ge errors when Arrhenius 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 “
25、service life.” Because of theerrors associated with these calculations, this time should beconsidered 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-d
26、raft circulation with substantial constantfresh air intake is recommended. When it is necessary to avoidcontamination among specimens or materials, a tubular ovenmethod such as Practice D 1870 may be desirable. Ovenapparatus shall be in accordance with Specifications E 145,Type IIB for temperature u
27、p to 70C. For higher temperature,Type IIA is required. Provision should be made for suspendingspecimens without touching each other or the side of thechamber. Recording instrumentation to monitor the tempera-ture of exposure is recommended.5.3 Test Equipment to determine the selected property orprop
28、erties, in accordance with appropriate ASTM procedures.6. Sampling6.1 The number and type of test specimens required shall bein accordance with the ASTM test method for the specificproperty to be determined; this requirement should be met ateach time and temperature selected.6.2 Sampling should also
29、 be in accordance with the perti-nent considerations outlined in Practice D 1898.7. Test Specimens7.1 The number and type of test specimens required shall bein accordance with the ASTM test method for the specificproperty to be determined; this requirement should be met ateach time and temperature s
30、elected. Unless otherwise specifiedor agreed upon by all interested parties, expose a minimum ofthree replicates of each material at each time and temperatureselected.7.2 The specimen thickness should be comparable to but nogreater than the minimum thickness of the intended applica-tion.7.3 The meth
31、od of specimen fabrication should be the sameas that of the intended application.8. Conditioning8.1 Conduct initial tests in the standard laboratory atmo-sphere as specified in Practice D 618, and with specimensconditioned in accordance with the requirements of the ASTMtest method for determining th
32、e specific property or propertiesrequired.8.2 When required, conditioning of specimens followingexposure at elevated temperature and prior to testing, unlessotherwise specified, shall be in accordance with PracticeD 618.8.3 If possible, avoid simultaneous aging of mixed groupsof different compounds
33、which might cause cross contamina-tion.9. Procedure9.1 When tests at a single temperature are used, all materialsmust be exposed at the same time in the same device. Use asufficient number of replicates of each material for eachexposure time so that results of tests used to characterize thematerial
34、property can be compared by analysis of variance orsimilar statistical 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 exposure tempera-tures. The following procedures a
35、re recommended for selectingexposure temperatures:9.2.1 The lowest temperature should produce the desiredlevel of property change or product failure in approximatelyD 3045 92 (2003)2nine to twelve months. The next higher temperature shouldproduce the same level of property change or product failure
36、atapproximately six months.9.2.2 The third and fourth temperatures should produce thedesired level of property change or product failure in approxi-mately three months and one month, respectively.9.2.3 When possible, select the exposure temperatures fromTable 1 (taken from the list of standard tempe
37、ratures in PracticeD 618). 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)may 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
38、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 theheat agi
39、ng temperatures. Exercise care to avoid aging at knowntransition temperatures since aging rates of materials usuallychange significantly at their transition temperatures.9.3 Test one set of specimens for the selected property inaccordance with the appropriate test method, including provi-sions for c
40、onditioning.9.4 Expose the remaining sets of specimens for the selectedtime intervals at the prescribed temperatures. Following expo-sure, condition these specimens in accordance with establishedprocedure, and then test. If an effect of aging without heat isanticipated, likewise condition and test a
41、 parallel set or agedunexposed specimens. If necessary, establish a procedure forcooling after oven exposure.10. Calculation10.1 When materials are compared at a single temperature,use analysis of variance to compare the mean of the measuredproperty data for each material at each exposure time. Use
42、theresults from each replicate of each material being compared forthe analysis of variance. It is recommended that the F statisticfor 95 % confidence be used to determine significance for theresults from the analysis of variance calculations.10.2 When materials are being compared using a range ofdif
43、ferent temperatures, use the following procedure to analyzethe data and to estimate the exposure time necessary to producea predetermined level of property change at some temperaturelower than the test temperatures used. This time can be used forgeneral ranking of materials for temperature stability
44、 or as anestimate of the maximum expected service life at the tempera-ture selected.10.2.1 Prepare plots of the measured property as a functionof exposure time for all temperatures used. Plots should beprepared in accordance with Fig. 1 where the abscissa is alogarithmic time scale and the value of
45、the measured propertyis the ordinate.10.2.2 Use regression analysis to determine the relationshipbetween the logarithm of exposure time and measured prop-erty. Use the regression equation to determine the exposuretime necessary to produce a predetermined level of propertychange. An acceptable regres
46、sion equation must have an r2ofat least 80 %. A plot of the residuals (value of propertyretention predicted by regression equation minus actual value)versus aging time must show a random distribution. Use ofgraphical interpretation to estimate the exposure time neces-sary to produce the predetermine
47、d level of property change isnot recommended.10.2.3 Plot the logarithm of the calculated times to producethe predetermined level of property change (determined by theacceptable regression equation) as a function of the reciprocalof the absolute temperature (1/T in K) of each exposure used.A typical
48、plot of this type (known as an Arrhenius plot) isshown in Fig. 2. Use regression analysis to determine theTABLE 1 Suggested Temperatures and Exposure Times for the Determination of Heat Aging of PlasticsSuggestedExposureTemperaturest,CReciprocalTemperature inDegrees Absolute 1/T3 103Estimated Limiti
49、ng TemperaturesAtL, C40 55 70 85 100 115 135 155 180 210 24050 3.09 A70 2.91 B A90 2.75 C B A105 2.64 D C B A120 2.54 D C B A130 2.48 D C B A155 2.34 D C B A180 2.21 D C B A200 2.11 DCBA225 2.01 DCBA250 1.91 DCB A275 1.82 DC B300 1.74 DC325 1.67 DAEstimated Limiting Temperaturethe best estimate of limiting temperature available prior to the testing program. This may be based on prior knowledge of similarmaterials, and may subsequently be amended on the basis of the described short term data, as in 9.1.Suggested Exposure Times: A3, 6, 12, 24, 48 weeks; B1, 3, 6, 12, 24 weeks
