1、Designation: D3045 92 (Reapproved 2010)Standard 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
2、 number in parentheses 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 Department of Defense.1. Scope1.1 This practice is intended to define the exposure cond
3、i-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 selection o
4、fthe 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 single
5、 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-istics
6、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 pra
7、ctices 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:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD1870 Practice f
8、or Elevated Temperature Aging Using aTubular Oven3D1898 Practice for Sampling of Plastics3E145 Specification for Gravity-Convection and Forced-Ventilation OvensE456 Terminology Relating to Quality and Statistics2.2 ISO Standard:ISO 2578 (1974) Determination of Time-Temperature Lim-its After Exposure
9、 to Prolonged Action of Heat43. Terminology3.1 The terminology given in Terminology D883 and Ter-minology E456 is applicable to this practice.4. Significance and Use4.1 The use of this practice presupposes that the failurecriteria selected to evaluate materials (that is, the property orproperties be
10、ing 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 changes. The severity ofthe exposures in both time and temperature determ
11、ines 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 temperatures willgenerally cause some degradation, with progressive ch
12、ange 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 in color of the plastic or coloringagent, or both. Normally, additi
13、onal 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 Plastics.Current edition approved March 15, 2010. Published June 2010
14、. Originallyapproved in 1974. Last previous edition approved in 2003 as D3045 92 (2003).DOI: 10.1520/D3045-92R10.2For 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
15、 standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM Internatio
16、nal, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, 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 plasticiz
17、er or due to breakdown of thepolymer.4.5 The degree of change 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 materi
18、al. 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 sensitive to degradation thanbulk properties such as modulus, in most cases.4.6 Effects of exposure may be quite var
19、iable, especiallywhen specimens 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. Certa
20、in materials aresusceptible to degradation due to the influence 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
21、 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 the influence of stress orenvironment that is involved in most real life applications,must be used caut
22、iously by the designer, who must inevitablymake material choices 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
23、any applica-tion of the temperature index to be valid, the thermal 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
24、use of the materialin that product.4.9 There can be very large 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 chang
25、e or “failure” at the lowertemperature is often called the “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 contro
26、lled horizontal or vertical air flow oven,employing forced-draft circulation with substantial constantfresh air intake is recommended. When it is necessary to avoidcontamination among specimens or materials, a tubular ovenmethod such as Practice D1870 may be desirable. Ovenapparatus shall be in acco
27、rdance with Specifications E145,Type IIB for temperature up 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.
28、3 Test Equipment to determine the selected property orproperties, 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 ate
29、ach time and temperature selected.6.2 Sampling should also be in accordance with the perti-nent considerations outlined in Practice D1898.7. 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; thi
30、s requirement should be met ateach time and temperature selected. 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 mi
31、nimum thickness of the intended applica-tion.7.3 The method 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 D618, and with specimensconditioned in accordance with th
32、e requirements of the ASTMtest method for determining the 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 Practice D618.8.3 If possible, avoid s
33、imultaneous aging of mixed groupsof different compounds 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
34、 that results of tests used to characterize thematerial 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
35、 four exposure tempera-tures. The following procedures are recommended for selectingexposure temperatures:9.2.1 The lowest temperature should produce the desiredlevel of property change or product failure in approximatelynine to twelve months. The next higher temperature shouldD3045 92 (2010)2produc
36、e the same level of property change or product failure 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 temperat
37、ures 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)may be used.9.2.4 The purpose of Table 1 showing time schedules atspecific temperatures is to show a ty
38、pical 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
39、 as a basis for selecting the remainder of theheat aging 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 th
40、e appropriate test method, including provi-sions for conditioning.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 wit
41、hout heat isanticipated, likewise condition and test a 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 measuredprope
42、rty data for each material at each exposure time. Use 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
43、 When materials are being compared using a range ofdifferent 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 for
44、general ranking of materials for temperature stability 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
45、 abscissa is alogarithmic time scale and the value of 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 prede
46、termined level of propertychange. An acceptable regression 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 th
47、e exposure time neces-sary to produce the predetermined 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 t
48、emperature (1/T in K) of each exposure used.A typical plot of this type (known as an Arrhenius plot) isshown in Fig. 2. Use regression analysis to determine theequation defining the log time/reciprocal temperature relation-ship. An acceptable regression equation must meet the require-ments described
49、 in 10.2.2.10.2.4 Use the equation for the log of the time to producethe defined property change as a function of the reciprocalabsolute temperature to determine the time to produce thisproperty change at a preselected temperature agreed upon byall interested parties.TABLE 1 Suggested Temperatures and Exposure Times for the Determination of Heat Aging of PlasticsSuggestedExposureTemperaturest,CReciprocalTemperature inDegrees Absolute 1/T3 103Estimated Limiting 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
