1、Designation: G 156 02Standard Practice forSelecting and Characterizing Weathering ReferenceMaterials Used to Monitor Consistency of Conditions in anExposure Test1This standard is issued under the fixed designation G 156; the number immediately following the designation indicates the year oforiginal
2、adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This standard describes the criterion to be used forselection of a
3、WRM and procedures to be used for determiningwithin lab and between lab tolerances of changes in measuredproperties of a reference material intended for use in monitor-ing operating conditions to establish the consistency of expo-sure tests.NOTE 1Examples of laboratory accelerated tests in which a w
4、eather-ing reference material could be used to monitor consistency are light andwater exposure tests such as those described in Practices G 152, G 153,and G 154 G 155and other standards in which tests conducted accordingto these standards are referenced. Examples of outdoor exposures where aweatheri
5、ng reference material could be used to monitor consistency arethose conducted according to Practices G 7, G 24, or G 90. A referencematerial can also be used to monitor consistency of exposure or condi-tioning test that do not involve exposure to light.1.2 This practice does not cover (1) control ma
6、terials usedfor comparison of stability with test materials, or (2) standardmaterials used to time exposures.1.3 This practice provides an outline of experiments re-quired to determine how the measured properties of thereference material change as a function of exposure to specifiedtest conditions.
7、It includes establishment of reproducible mea-surement procedures, determination of the critical region in thelight source causing the changes, and effects of other criticalexposure stresses such as temperature and moisture.1.4 This practice describes procedures for conductinground-robin tests with
8、the weathering reference material todetermine reproducibility of the reference material propertychange in exposures conducted in different laboratories, andthe repeatability when replicate reference material specimensare exposed in a single device and tested in one laboratory.1.5 This practice descr
9、ibes procedures for using the resultsfrom analysis of variance on results from round-robin tests todetermine the contribution of the exposure, the measurementdevice, reference material variability, and operator error to totalvariability.2. Referenced Documents2.1 ASTM Standards:D 3980 Practice for c
10、onducting an Interlaboratory Study forTess of Paints and Related Coatings2E 177 Practice for Use of the Terms Precision and Bias inASTM Test Methods3E 691 Practice for Conducting an Interlaboratory Study toDetermine Precision of a Test Method3E 1169 Guide for Conducting Ruggedness Tests3G 7 Practice
11、 for Atmospheric Environmental ExposureTesting of Nonmetallic Materials4G 24 Practice for Conducting Exposures to Daylight Fil-tered Through Glass4G 90 Practice for Performing Accelerated Outdoor Weath-ering of Nonmetallic Materials Using Concentrated Natu-ral Sunligh4tG 113 Terminology Relating to
12、Natural and ArtificialWeathering Tests of Nonmetallic Materials4G 152 Practice for Operating Open Flame Carbon Arc LightApparatus for Exposure of Nonmetallic Materials4G 153 Practice for Operating Enclosed Carbon Arc LightApparatus for Exposure of Non metallic Materials4G 154 Practice for Operating
13、Fluorescent Light Apparatusfor Exposure of Nonmetallic Materials4G 155 Practice for Operating Xenon-Arc Light Apparatusfor Exposure of Nonmetallic Materials42.2 SAE Standard:SAE J1960, Accelerated Exposure of Automotive ExteriorMaterials using a Controlled Irradiance Water-CooledXenon Arc Apparatus5
14、SAE J1885, Accelerated Exposure of Automotive InteriorMaterials Using a Controlled Irradiance Water-CooledXenon Arc Apparatus53. Terminology3.1 DefinitionsThe definitions listed in Terminology1This practice is under the jurisdiction of ASTM Committee G3 on Weatheringand Durability and is the direct
15、responsibility of Subcommittee G03.01 on JointWeathering Projects.Current edition approved Feb. 10, 2002. Published May 2002. Originallypublished as G 15697. Last previous edition G 15697.2DiscontinuedSee Annual Book of ASTM Standards, Vol 06.02.3Annual Book of ASTM Standards, Vol 14.02.4Annual Book
16、 of ASTM Standards, Vol 14.04.5Available from Society of Automotive Engineers, 400 Commonwealth Drive,Warrendale, PA 15096.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.G 113 are applicable to this standard.4. Significance and Use4
17、.1 Weathering reference materials are used in laboratoryaccelerated exposure tests to establish consistency among testsrun at different times and in different laboratories in the sametype of device. Specifications defining consistency of exposureconditions based on the property change of a reference
18、 materialare usually based on results for a single lot of the referencematerial. When a new lot of the reference material is intro-duced, round-robin studies are necessary to compare the newand old lots and to establish appropriate limits for expectedperformance of the new lot.NOTE 2An example of th
19、e use of a clear polystyrene referencestandard for this purpose is given in SAE J1885 and SAE J1960.NOTE 3Some weathering reference materials (for example bluewools) are also used to define periods of exposure. Although notspecifically covered by this standard, the procedures described forcharacteri
20、zing a reference material used to monitor consistency ofexposures are also generally applicable to characterizing reference mate-rials used to define periods of exposure.4.2 It is important to test the consistency of exposure in thelaboratory accelerated device with a weathering referencematerial th
21、at responds to the test conditions similar to the waythe test materials respond. Therefore, the weathering referencematerial should be sensitive to the spectral region of the lightsource mainly responsible for producing degradation in the testmaterials to provide the most meaningful evaluation of ex
22、po-sure test consistency. The weathering reference material shouldalso provide information on consistency of temperature andhumidity conditions if the latter are important factors indegradation of the test materials.NOTE 4Material homogeneity can also be an important factor inselection of a weatheri
23、ng reference material, particularly if weathering isinitiated by the radiation absorbed by impurities as is the case in aliphatictype polymers exposed to radiation longer than 300 nm.4.3 The measurement of the characteristic property of aweathering reference material can be subject to error depend-i
24、ng on the instrument and the procedure used to measure theproperty. It is important to develop measurement proceduresthat are clear and which minimize chances for operatormisinterpretation. It is also important to determine the level ofvariability caused by measurement of the characteristic prop-ert
25、y.4.4 When a reference material is used to monitor or specifythe consistency of an exposure test, it is important that anyspecification limits defined by changes in the reference mate-rial be based on a sound statistical analysis of results from aproperly designed round-robin experiment. This practi
26、ce pro-vides a procedure which can be followed to set up theround-robin, analyze results, and establish reasonable limits ofchange in the characteristic property of the reference materialthat can be used in specifications.4.4.1 The results obtained according to this practice arevalid only for the ex
27、posure cycle used for the round-robin andcannot be applied to the same weathering reference materialused in a different exposure cycle.4.5 The change in characteristic property of a referencematerial may be affected by the placement of the referencematerial in the exposure device. This is often due
28、to variationsin light intensity and temperature within the allowed exposurearea. Random placement of replicate specimens of the weath-ering reference material through-out the allowed exposure areaprovides the best indication of the overall consistency of theexposure test.NOTE 5In some cases, procedu
29、res require exposure of a weatheringreference material at a specific location within the exposure device orchamber. Results for a reference material used in this way may not providean accurate representation of the exposure conditions in other positionswithin the device.5. Procedure5.1 Select a refe
30、rence material which exhibits a measurablechange in a characteristic property when exposed in thespecific type of device and exposure cycle to be monitored.5.2 Determine the procedure used that can best measure thechange in characteristic property of the reference material.5.2.1 Conduct a series of
31、experiments to determine theeffect of important factors in the measurement procedure. It isrecommended that this be done using a ruggedness testaccording to Guide E 1169 to determine which factors signifi-cantly affect results. The results from this test can be used totighten the test measurement pr
32、ocedures.5.2.2 When the results from the ruggedness testing arecomplete, write a set of instructions for running the test used todetermine the level of the characteristic property that isunambiguous and clearly understood by operators who will bemaking the measurement. Have two operators in one labo
33、ra-tory conduct the measurement on at least three replicatespecimens of the reference material. Interview the operators todetermine whether the procedure provides clear and easy tounderstand directions. Modify the procedure to remove anyambiguity in instructions.5.3 Determine the homogeneity of the
34、weathering referencematerial by measuring the property change of randomlyselected replicate specimens that have been exposed to verytightly controlled test conditions, or by appropriate chemicalanalysis techniques such as ultraviolet and/or infrared spectro-scopic analysis.5.4 For any new weathering
35、 reference material, determinethe response of the reference material to critical exposurestresses. These results are important to determining whetherthe material being considered is appropriate for monitoring thespecific conditions of the exposure test being used. Tests todetermine the materials res
36、ponse to exposure stresses should bedone in a single laboratory or a series of laboratories agreedupon by all interested parties.5.4.1 Conduct experiments to determine the spectral regionof the light source to which the characteristic property is mostsensitive, i.e. the activation spectrum of the we
37、athering refer-ence material. This can be accomplished by techniques toisolate the effects of individual narrow bands of the actinicregion of the light source. It is recommended that severaldeterminations of the activation spectrum be conducted.NOTE 6Techniques to obtain activation spectra are descr
38、ibed in thefollowing reference: by N. Searle, N., “Activation Spectra of Polymersand Their Application to Stabilization and Stability Testing”, Handbook ofG 1562Polymer Degradation, S. Hamid, editor, Marcel Dekker, New York.2000.65.4.2 Conduct experiments to determine how the rate ofchange of the ch
39、aracteristic property of the reference materialis affected by temperature. This can be done by exposing aseries of reference material specimens to the light source ofchoice at a series of temperatures (with irradiance and humidityheld constant).5.4.3 Conduct a series of experiments to determine how
40、therate of change of the characteristic property of the referencematerial is affected by moisture. This can be done by conduct-ing exposure tests at constant light intensity and temperaturewhere the time of wetness or relative humidity is varied.5.4.4 A factorially designed experiment can be used to
41、determine the effects of moisture and humidity. Use at least twolevels of temperature and relative humidity in the designedexperiment conducted at a constant light intensity.5.5 The procedure for conducting the exposure test in whichthe weathering reference material is used should clearly specifythe
42、 levels of light intensity, filters used on light source,chamber or black panel temperature, and moisture conditions.These conditions must be specified for each different light/darkperiod used in the exposure cycle chosen.5.6 Determine the stability of the measured property of thereference material
43、after it has been removed from the exposure.The post exposure stability of the characteristic property can bedetermined by measurements made at a series of times afterremoval from the exposure. Typically, these measurements willbe made at successively long time intervals. Some materials(for example
44、polysulfone) show a continuing change in mea-sured property after they are removed from the exposure. If thecharacteristic property shows a change after being removedfrom the exposure, the instructions for use must clearly specifythe time after exposure when the characteristic property is to bemeasu
45、red. It is strongly recommended that the characteristicproperty of the reference material be reasonably stable afterremoval from the exposure test.5.6.1 Property measurements must be made during theperiod when the weathering reference material is stable afterbeing exposed.NOTE 7Tests to determine wa
46、velength sensitivity do not provideinformation about the effects of temperature, moisture, or variation inirradiance. Variations in these other exposure stresses may alter the resultsof test used to determine wavelength sensitivity.NOTE 8In general, weathering reference materials that are stable for
47、at least 10 days after removal from exposure will be the most useful.5.7 After selecting the reference material, characteristicproperty, property measurement procedure, and the desiredexposure conditions, set up a round-robin study to determinethe level of within lab repeatability and between lab re
48、produc-ibility for the change in property of the reference material afterspecific exposure periods.5.7.1 Conduct the round-robin according to Guide E 691 orPractice D 3980. At least six laboratories should participate inthe round robin.5.7.2 Prepare a clear set of instructions for all round-robinpar
49、ticipants. The instructions should cover specimen place-ment in the exposure device, including how the referencematerial is to be mounted in specimen holder, exact exposurecycle to be used, the exact procedure for measuring character-istic property, and how data will be recorded.NOTE 9Round-robin studies that show how reproducibility and re-peatability limits can be determined for a candidate weathering referencematerial.75.7.3 At least three exposure periods should be used for theround-robin, with separate sets of the reference material to beused for each exposure period. Use
