1、Designation: G156 09G156 17Standard Practice forSelecting and Characterizing Weathering ReferenceMaterials1This standard is issued under the fixed designation G156; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last r
2、evision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This standard describes the criteria to be used for selection of a weathering reference material (WRM) and procedures tobe u
3、sed for determining within lab and between lab tolerances of changes in measured properties of aweathering referencematerials.This standard also describes a procedure for comparing different lots of the same type of a weathering reference material.NOTE 1Examples of laboratory accelerated tests in wh
4、ich a weathering reference material could be used to monitor consistency are exposure testssuch as those described in Practices G152, G153, G154, and G155and other standards in which tests conducted according to these standards arereferenced. Examples of outdoor exposures where a weathering referenc
5、e material could be used to monitor consistency are those conducted accordingto Practices G7, G24, or G90. A reference material can also be used to monitor consistency of exposure or conditioning test that do not involve exposureto light.1.2 Weathering reference materials are most often used to (1)
6、monitor consistency of conditions in (that is, repeatability,reproducibility, or both) of exposure tests, (2) to determine the time or radiant exposure at which test materials are evaluated, (3)as a reference material for comparing to test materials exposed at the same time. Weathering reference mat
7、erials cannot be usedto classify or characterize the relative severity of any exposure test because of the large variability in material responses to theeffects of light, heat, and water.1.3 This practice does not cover control materials which, by definition are selected to be of similar composition
8、 and constructionto the test materials, and are exposed at the same time as test materials.1.4 This practice provides an outline of experiments required to determine how the measured properties of the reference materialchange as a function of exposure to specified test conditions. It includes establ
9、ishment of reproducible measurement procedures,determination of the critical spectral region in the light source causing the changes, and effects of other critical exposure stressessuch as temperature and moisture.2. Referenced Documents2.1 ASTM Standards:2E177 Practice for Use of the Terms Precisio
10、n and Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodE1169 Practice for Conducting Ruggedness TestsG7 Practice for Atmospheric Environmental Exposure Testing of Nonmetallic MaterialsG24 Practice for Conducting Exposures to Da
11、ylight Filtered Through GlassG90 Practice for Performing Accelerated Outdoor Weathering of Nonmetallic Materials Using Concentrated Natural SunlightG113 Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic MaterialsG152 Practice for Operating Open Flame Carbon Arc Light App
12、aratus for Exposure of Nonmetallic MaterialsG153 Practice for Operating Enclosed Carbon Arc Light Apparatus for Exposure of Nonmetallic MaterialsG154 Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Nonmetallic MaterialsG155 Practice for Operating Xenon Arc Light Ap
13、paratus for Exposure of Non-Metallic MaterialsG178 Practice for Determining theActivation Spectrum of a Material (Wavelength Sensitivity to an Exposure Source) Using theSharp Cut-On Filter or Spectrographic Technique1 This practice is under the jurisdiction of ASTM Committee G03 on Weathering and Du
14、rability and is the direct responsibility of Subcommittee G03.01 on JointWeathering Projects.Current edition approved June 1, 2009Feb. 1, 2017. Published July 2009February 2017. Originally approved in 1997. Last previous edition approved in 20022009 asG15602.09. DOI: 10.1520/G0156-09.10.1520/G0156-1
15、7.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only
16、to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
17、of the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 SAE Standard:SAE J1960,J2527, Accelerated Exposure of Automotive Exterior Materials using a Controlled
18、Irradiance Water-Cooled XenonArc Apparatus3SAE J1885,J2412, Accelerated Exposure of Automotive Interior Materials Using a Controlled Irradiance Water-Cooled XenonArc Apparatus33. Terminology3.1 DefinitionsThe definitions listed in Terminology G113 are applicable to this standard.4. Significance and
19、Use4.1 Weathering reference materials are used in laboratory accelerated exposure tests to verify consistency amongof tests runwithin the same instrument at different times and (repeatability) or in different laboratories, instruments or different laboratories(reproducibility), using the same exposu
20、re conditions. conditions, or both. Specifications defining consistency of exposureconditions are based on the property change of a reference material after a defined period of time. Some weathering referencematerials are used to define periods of exposure. Specifications calling forrecommending the
21、 use of these materials require thematerial to be exposed until a defined change in the weathering reference material is achieved. Specifications are usually basedon results for a single lot of the weathering reference material. When a new lot of the reference material is introduced, round-robinstud
22、ies are necessary to compare the new and old lots and to establish appropriate limits for expected performance of the new lot.NOTE 2An example of the use of a clear polystyrene reference standard for this purpose is given in SAE J1885J2412 and SAE J1960.J2527.NOTE 3Some weathering reference material
23、s (for example blue wools) are also used to define periods of exposure.Although not specifically coveredby this standard, the procedures described for characterizing a reference material used to monitor consistency of exposures are also generally applicableto characterizing reference materials used
24、to define periods of exposure.4.2 It is important to test the consistency of exposure in the laboratory accelerated device with a weathering reference materialthat responds to the test conditions similar to the way the test materials respond. Therefore, the weathering reference materialshould be sen
25、sitive to the spectral region of the light source mainly responsible for producing degradation in the test materials toprovide the most meaningful evaluation of exposure test consistency. The weathering reference material should also provideinformation on consistency of temperature and humidity cond
26、itions if the latter are important factors in degradation of the testmaterials.NOTE 4Material homogeneity can also be an important factor in selection of a weathering reference material, particularly if weathering is initiatedby the radiation absorbed by impurities as is the case in aliphatic type p
27、olymers exposed to radiation longer than 300 nm.4.3 The measurement of the characteristic property of a weathering reference material can be subject to error depending on theinstrument and the procedure used to measure the property. It is important to developuse measurement procedures that are clear
28、and which minimize chances for operator misinterpretation. It is also important to determine the level of variability caused bymeasurement of the characteristic property.4.4 When a reference material is used to monitor or specify the consistency of an exposure test, it is important that anyspecifica
29、tion limits defined by changes in the reference material be based on a sound statistical analysis of results from a properlydesigned round-robin experiment. This practice provides a procedure which can be followed to set up the round-robin, analyzeresults, and establish reasonable limits of change i
30、n the characteristic property of the reference material that can be used inspecifications.4.4.1 The results obtained according to this practice are valid only for the exposure cycle used for the round-robin and cannotbe applied to the same weathering reference material used in a different exposure c
31、ycle.cycles.4.5 The change in characteristic property of a reference material may be affected by the placement of the reference material inthe exposure device. This is often due to variations in light intensity and temperature within the allowed exposure area. Randomplacement of replicate specimens
32、of the weathering reference material through-outthroughout the allowed exposure area providesthe best an indication of the overall consistency of uniformity of conditions within the exposure test.area.NOTE 5In some cases, procedures require exposure of a weathering reference material at a specific l
33、ocation within the exposure device or chamber.Results for a reference material used in this way may not provide an accurate representation of the exposure conditions in other positions within thedevice.5. Procedure5.1 Select a weathering reference material that exhibits a significant change in a cha
34、racteristic property when exposed for anacceptable period of time, to the exposure conditions described in the applicable test procedure.5.2 Determine the an evaluation procedure used that can best measure the change in characteristic property of the referencematerial.3 Available from Society of Aut
35、omotive Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, http:/www.sae.org.G156 1725.2.1 Conduct a series of experiments to determine the effect of important factors in the measurement procedure. It isrecommended that this be done using a ruggedness test according to Guide E1169 to
36、determine which factors significantly affectresults. The results from this test can be used to tighten the test measurement procedures.5.2.2 When the results from the ruggedness testing are complete, write a set of instructions for measuring the characteristicproperty that is unambiguous and clearly
37、 understood by operators who will be making the measurement. Have two operators inone laboratory conduct the measurement on at least three replicate specimens of the reference material. Interview the operators todetermine whether the procedure provides clear and easy to understand directions. Modify
38、 the procedure to remove any ambiguityin instructions.5.3 Determine the homogeneity of the weathering reference material by measuring the property change of randomly selectedreplicate specimens that have been exposed to very tightly controlled test conditions, or by appropriate chemical analysistech
39、niques such as ultraviolet and/or infrared spectroscopy.5.4 For any new weathering reference material, determine the response of the reference material to critical exposure stresses.These results are important to determining whether the material being considered is appropriate for monitoring the spe
40、cificconditions of the exposure test being used. Tests to determine the materials response to exposure stresses should be done in a singlelaboratory or a series of laboratories agreed upon by all interested parties.5.4.1 Conduct experiments to determine the spectral region of the light source to whi
41、ch the characteristic property is mostsensitive, i.e. the activation spectrum of the weathering reference material. This can be accomplished by techniques to isolate theeffects of individual narrow bands of the actinic region of the light source. It is recommended that several determinations of thea
42、ctivation spectrum be conducted.NOTE 6Practice G178 describes two procedures for determination of activation spectra of polymers.5.4.2 Conduct experiments to determine how the rate of change of the characteristic property of the reference material isaffected by temperature. This can be done by expos
43、ing a series of reference material specimens to the light source of choice at aseries of temperatures (with irradiance and humidity held constant).5.4.3 Conduct a series of experiments to determine how the rate of change of the characteristic property of the reference materialis affected by moisture
44、. This can be done by conducting exposure tests at constant light intensity and temperature where the timeof wetness or relative humidity is varied.5.4.4 A factorially designed experiment can be used to determine the effects of moisture and humidity. Use at least two levelsof temperature and relativ
45、e humidity in the designed experiment conducted at a constant light intensity.5.5 The procedure for conducting the exposure test in which the weathering reference material is used should clearly specifythe levels of light intensity, optical filters used on with the light source, chamber or and insul
46、ated/uninsulated black paneltemperature, and moisture conditions. These conditions must be specified for each different light/dark period used in the exposurecycle chosen.5.6 Determine the stability of the measured property of the reference material after it has been removed from the exposure. Thepo
47、st exposure stability of the characteristic property can be determined by measurements made at a series of times after removalfrom the exposure. Typically, these measurements will be made at successively long time intervals. Some materials (for examplepolysulfone) show a continuing change in measure
48、d property after they are removed from the exposure. If the characteristicproperty shows a change after being removed from the exposure, the instructions for use must clearly specify the time afterexposure when the characteristic property is to be measured. It is strongly recommended that the charac
49、teristic property of thereference material be reasonably stable after removal from the exposure test.5.6.1 Property measurements must be made during the period when the weathering reference material is stable after beingexposed.NOTE 7Tests to determine wavelength sensitivity do not provide information about the effects of temperature, moisture, or variation in irradiance.Variations in these other exposure stresses may alter the results of test used to determine wavelength sensitivity.NOTE 8In general, weathering reference materials that are stable for at least 10 days af
