1、Designation: G24 13Standard Practice forConducting Exposures to Daylight Filtered Through Glass1This standard is issued under the fixed designation G24; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision.Anum
2、ber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice evaluates the resistance of nonmetallicmaterials to solar radiation filtered through glass in passivelyventilated and non-ven
3、ted enclosures. For exposures in underglass enclosures with forced air circulation, refer to PracticeG201.1.2 For direct exposures, refer to Practice G7.1.3 This practice is limited to the method of conducting theexposures. The preparation of test specimens and evaluation ofresults are covered in va
4、rious standards for the specificmaterials.1.4 Exposure conducted according to this practice can usetwo types of exposure cabinets.1.4.1 Type AA cabinet that allows passive ventilation ofspecimens being exposed behind glass.1.4.2 Type BEnclosed cabinet with exterior painted blackthat does not provide
5、 for ventilation of specimens exposedbehind glass. Exposures conducted using a Type B cabinet aretypically referred to as “black box under glass exposures.”1.5 TypeAexposures of this practice are technically similarto Method B of ISO 877-2.1.6 The values stated in SI units are to be regarded as thes
6、tandard. The inch-pound units given in parentheses are forinformation only.1.7 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 practices and determin
7、e the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C1036 Specification for Flat GlassD3424 Practice for Evaluating the Relative Lightfastnessand Weatherability of Printed MatterD4303 Test Methods for Lightfastness of Colorants Used inArtists Materi
8、alsD6901 Specification for Artists Colored PencilsE824 Test Method for Transfer of Calibration From Refer-ence to Field RadiometersE903 Test Method for Solar Absorptance, Reflectance, andTransmittance of Materials Using Integrating SpheresE1084 Test Method for Solar Transmittance (Terrestrial) ofShe
9、et Materials Using SunlightG7 Practice for Atmospheric Environmental Exposure Test-ing of Nonmetallic MaterialsG113 Terminology Relating to Natural and Artificial Weath-ering Tests of Nonmetallic MaterialsG173 Tables for Reference Solar Spectral Irradiances: DirectNormal and Hemispherical on 37 Tilt
10、ed SurfaceG177 Tables for Reference Solar Ultraviolet Spectral Distri-butions: Hemispherical on 37 Tilted SurfaceG201 Practice for Conducting Exposures in Outdoor Glass-Covered Exposure Apparatus with Air Circulation2.2 Other Documents:WMO Guide to Meteorological Instruments and Methods ofObservatio
11、n WMO No. 8, Seventh Edition.3ISO 105 B01 TextilesTests for Colour Fastness, Interna-tional Standards Organization, Geneva, Switzerland.4ISO 877-1 Plastics Methods of Exposure to Solar Radia-tion Part 1: General Guidance4ISO 8772 Plastics Methods of Exposure to Solar Radia-tion Part 2: Direct Weathe
12、ring and Exposure BehindWindow GlasAATCC TM 16, Option 6 Colorfastness to Light, Daylight5AATCC Test Method 16.1-2012 Colorfastness to Light:Outdoor3. Terminology3.1 Definitions:1This practice is under the jurisdiction ofASTM Committee G03 on Weatheringand Durabilityand is the direct responsibility
13、of Subcommittee G03.02 on Naturaland Environmental Exposure Tests.Current edition approved June 1, 2013. Published July 2013. Originally approvedin 1973. Last previous edition approved in 2005 as G24 05. DOI: 10.1520/G0024-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orco
14、ntact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from World Meteorological Organization (WMO), 7bis, avenue de laPaix, Case Postale No. 2300, CH-1211 Geneva 2, Switzerland,
15、http:/www.wmo.int.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.5Available from American Association of Textile Chemists and Colorists(AATCC), P.O. Box 12215, Research Triangle Park, NC 27709, http:/www.aatcc.org.*A Sum
16、mary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1 The definitions contained in Terminology G113 areapplicable to this practice.4. Significance and Use4.1 Since solar radia
17、tion, air temperature, relative humidity,and the amount and kind of atmospheric contaminants varycontinuously, results from exposures based on elapsed timemay differ. The variations in the results may be minimized bytiming the exposures in terms of:4.1.1 One or more environmental parameters such as
18、solarradiant exposure, or4.1.2 A predefined property change of a weathering refer-ence specimen with known performance.4.2 Variations in temperature, moisture and atmosphericcontaminants can have a significant effect on the degradationcaused by solar radiation. In addition, exposures conducted atdif
19、ferent times of the year can cause large differences in rate ofdegradation. Different materials may have different sensitivi-ties to heat, moisture, and atmospheric contaminants, whichmay explain differences in rankings of specimens exposed toequivalent solar radiant exposure when other environmenta
20、lconditions vary.4.3 Since the method of mounting may influence the tem-perature and other parameters during exposure of thespecimen, there should be a mutual understanding as to themethod of mounting the specimen for the particular exposuretest under consideration.4.4 There can be large differences
21、 among various singlestrength window glasses in their transmittance in the 300 to350 nm region. For example, at 320 nm, the percent transmit-tance for seven different lots of single strength window glassranged from 8.4 to 26.8 %. At 380 nm, the percent transmit-tance ranged from 84.9 % to 88.1 %.64.
22、5 Differences in UV transmittance between different lotsof glass persist after solarization. The largest differencesamong window glasses in UV transmittance are in the spectralrange of 300 to 320 nm.4.6 This practice is best used to compare the relativeperformance of materials tested at the same tim
23、e behind thesame lot of glass. Because of variability between lots of glassand between exposures conducted at different times of the year,comparing the amount of degradation in materials exposed forthe same duration or radiant exposure at separate times, or inseparate fixtures using different lots o
24、f glass is not recom-mended.4.7 It is strongly recommended that at least one controlmaterial be exposed with each test. The control material shouldbe of similar composition and construction. and be chosen sothat its failure modes are the same as that of the material beingtested. It is preferable to
25、use two control materials, one withrelatively good durability, and one with relatively poor dura-bility. If control materials are included as part of the test, theyshall be used for the purpose of comparing the performance ofthe test materials relative to the controls.6Ketola, W. D., and Robbins, J.
26、S., III, “UV Transmission of Single StrengthWindow Glass,” Accelerated and Outdoor Durability Testing of Organic Materials,ASTM STP 1202, Warren D. Ketola and Douglas Grossman, Eds.,American Societyfor Testing and Materials, Philadelphia, 1994.FIG. 1 a and 1b Typical Passively-Ventilated Under Glass
27、 Exposure Cabinet, Type AFIG. 2 Typical Non-Ventilated Enclosed Under Glass ExposureCabinet, Type B (Black Box Under Glass)G241324.8 There are other standards which describe exposures toglass filtered daylight. Six cited standards are D3424, D4303,D6901, ISO 105-B01, ISO 877-1, ISO-877-2, AATCC TM16
28、C.4.9 Because of the possibility that certain materials mayoutgas during exposure, it is recommended that only similarmaterials be exposed in the same under glass cabinet at thesame time.5. Apparatus5.1 Exposure Cabinet:5.1.1 Type AA glass-covered enclosure or cabinet of anyconvenient size, construc
29、ted to protect the specimens fromrain. It typically is constructed of metal or wood, and shall beopen on the back or sides to allow ambient air to passivelycirculate over the specimens (Fig. 1a and b).5.1.2 Type B (Black Box Under Glass)A glass-coveredenclosure or cabinet of any convenient size. It
30、shall beconstructed of corrosion resistant metal and be enclosed toprevent ambient air from circulating over specimens. Exteriornon-glass surfaces shall be painted flat black. The interior shallremain unpainted (Fig. 2).NOTE 1For some exposures (for example Method B of D4303 orMethod A of D6901), a
31、small fan is inserted into the Type B enclosure tominimize condensation. For enclosures with forced air circulation, refer toPractice G201.NOTE 2The black box under glass enclosure is often used to simulateunder glass exposures under conditions of high temperature, such as theinterior of an automobi
32、le. However, because black box under glasscabinets are enclosed, air temperatures may exceed 80C under conditionsof high outside ambient air temperature and solar irradiance. In addition,significant differences in air and specimen temperatures can be experi-enced between upper and lower portions of
33、the cabinet. Frequenttemperature measurement and specimen repositioning may be required toproperly use this enclosure.5.1.3 Unless otherwise specified the glass cover shall be apiece of non-laminated, transparent flat glass, greenhousequality Q4 or better as specified in section 4.1 of Specification
34、C1036. Thickness shall be 2.0 to 3.2 mm.5.1.3.1 In order to reduce variability due to changes in UVtransmittance of glass, all new glass shall be exposed facing theequator, at any convenient exposure tilt angle within the rangeof 5 to 45, according to Practice G7, or on an empty underglass exposure
35、cabinet, for at least three months prior toinstallation in test cabinets.5.1.3.2 After the three-month pre-exposure period, it isrecommended that the spectral transmittance of representativesamples from each lot of glass be measured. Typically, “singlestrength” glass will have a transmittance of 10
36、to 20 % at 320nm and at least 85 % at wavelengths of 380 nm or higher afterthe three month pre-aging procedure. If transmittance of theglass is measured, report the average for at least three pieces ofthe lot of glass being tested. Follow the instructions formeasurement of transmittance of solid sam
37、ples recommendedby the manufacturer of the UV-visible spectrophotometer used.If a spectrophotometer with an integrating sphere is used, themeasurements shall be performed in accordance with TestMethod E903.NOTE 3Other standards describing exposures behind glass havedifferent requirements for glass t
38、ransmittance and do not require pre-aging.NOTE 4After the initial pre-aging period, the UV transmittance ofwindow glass is suitable for at least 60 months of use. UV transmittancedifferences between lots of glass persist during this time, however.Different lots of single-strength window glass can ha
39、ve different opticalproperties even if purchased from the same manufacturer.5.1.3.3 Wash the exterior surface of the glass cover everymonth, and the interior surface of the glass cover every 3months (or more frequently, if required) to remove dustparticles and other undesirable deposits.5.1.4 The en
40、closure or cabinet shall be equipped with a rackwhich supports the specimens in a plane parallel to the glass.Whenever possible, the specimens should be supported at adistance of 75 6 25 mm (3 6 1 in.) behind the glass cover.Formed specimens with irregular dimensions may requirecustom mounting with
41、varying distances from the glass cover.In such cases, mount the test sample surface of major interestparallel to the glass cover at a distance of 75 6 25 mm (3 61 in.) behind the glass cover. The mounting frame or plate shallbe constructed of a material that is compatible with the testspecimens. In
42、order to minimize shadowing from the top andsides of the cabinet, the usable exposure area under the glassshall be limited to that of the glass cover reduced by twice thedistance from the cover to the specimens as shown in Fig. 3.The effective width of the specimen mounting area is L-4X andthe effec
43、tive height of the mounting area is W-4X, where L isthe width of the glass cover, W is the height of the glass cover,and X is the distance between the glass cover and thespecimens. For example, if the specimens are 75 mm below theFIG. 3 Mounting Frame DimensionsG24133glass, then all specimens shall
44、be at least 150 mm from the topor sides. Three types of mounting frames or backings may beused.5.1.4.1 Unbacked or Open MountingSpecimens are at-tached only at edges.5.1.4.2 Expanded Aluminum MountingSpecimens are at-tached to an expanded aluminum backing.5.1.4.3 Solid MountingSpecimens are attached
45、 to a solidbacking such as plywood.NOTE 5The method used to mount specimens shall be related to theirend-use. In evaluating the specimens, the edges of these specimens thatare used to secure the specimen to the framework should be disregarded.5.1.5 The cabinet shall be located where it will received
46、irect sunlight throughout the day and where shadows ofobjects in the vicinity will not fall upon it. When the cabinet isinstalled over grass, the distance between the bottom of thecabinet and the ground shall be sufficient to prevent contactwith plant growth, or to minimize damage that might occurdu
47、ring maintenance.5.1.6 The glass cover and the test specimens shall beoriented in a manner mutually agreed upon between interestedparties. The angle shall be reported in the results of the test.Possible exposure orientations are listed as follows:5.1.6.1 Fixed tilt angle equal to the latitude of the
48、 exposuresite with cabinet facing equator,5.1.6.2 Tilt angle of 45 facing the equator,5.1.6.3 Tilt angle of 5 facing the equator,5.1.6.4 Tracking azimuth and tilt angle in order to maintainthe exposure plane normal to the suns direct beam.5.1.6.5 Any other angle that is mutually agreed on by allinte
49、rested parties may be used. In some instances, exposuresfacing directly away from the equator or some other specificdirection may be desired. The test report shall contain the exactangle and specimen orientation.5.2 Climatological Instruments:5.2.1 Instruments suitable for determining maximum,minimum, and average daily ambient air temperature, cabinetair temperature (optional), and specimen temperature (op-tional). Ambient air temperature will be measured in ashielded, elevated location in the general vicinity of the underglass exposure cabinet.5.2.
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