1、Designation: G 24 05Standard Practice forConducting Exposures to Daylight Filtered Through Glass1This standard is issued under the fixed designation G 24; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision. A
2、 number in parentheses indicates the year of last reapproval. A superscriptepsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice evaluates the resistance of nonmetallicmaterials to solar radiation filtered through glass.1.2 For direct exposures, re
3、fer 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 various standards for the specificmaterials.1.4 Exposure conducted according to this practice can usetwo types of exposure cabinets.1.4.
4、1 Type AA cabinet that allows passive ventilation ofspecimens being exposed behind glass.1.4.2 Type BEnclosed cabinet with exterior painted blackthat allows no ventilation of specimens exposed behind glass.Exposures conducted using a Type B cabinet are typicallyreferred to as “black box under glass
5、exposures.”1.5 Type A exposures of this practice are technically similarto Method B of ISO 877.1.6 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 pr
6、actices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 1036 Specification for Flat GlassE 824 Method for Transfer of Calibration from Reference toField PyranometersE 903 Test Method for Solar Absorptance, Reflectance, andTransmitt
7、ance of Materials Using Integrating SpheresE 1084 Test Method for Solar Transmittance (Terrestial) ofSheet Materials Using SunlightG7 Practice for Atmospheric Environmental ExposureTesting of Nonmetallic MaterialsG113 Terminology Relating to Natural and ArtificialWeathering Tests of Nonmetallic Mate
8、rialsG 173 Tables for Reference Solar Spectral Irradiances:Direct Normal and Hemispherical on 37 Titled SurfaceG 177 Tables for Reference Solar Ultraviolet Spectral Dis-tributions: Hemispherical on 37 Tilted Surface2.2 Other Documents:WMO Guide to Meteorological Instruments and Methods ofObservation
9、 WMO No. 8, Fifth Edition.3ISO 105 B01 TextilesTests for Colour Fastness, Interna-tional Standards Organization, Geneva, Switzerland.4ISO 877 PlasticsMethods of Exposure to Direct Weath-ering, to Weathering Using Glass-Filtered Daylight, and toIntensified Weathering by Daylight Using Fresnel Mirrors
10、,International Standards Organization, Geneva, Switzer-land4AATCC 16C Colorfastness to Light, Daylight53. Terminology3.1 Definitions:3.1.1 The definitions contained in Terminology G113areapplicable to this practice.4. Significance and Use4.1 Since solar irradiance, air temperature, relative humid-it
11、y, and the amount and kind of atmospheric contaminants varycontinuously, results from exposures based on time may differ.The variations in the results may be minimized by timing theexposures in terms of one or more environmental parameterssuch as solar radiant exposure, or in terms of a predetermine
12、dproperty change of a reference specimen with known perfor-mance.4.2 Variations in temperature, moisture and atmosphericcontaminants can have a significant effect on the degradationcaused by solar radiation. In addition, exposures conducted atdifferent times of the year can cause large differences i
13、n rate ofdegradation. Different materials may have different sensitivi-ties to heat, moisture, and atmospheric contaminants. This may1This practice is under the jurisdiction of ASTM Committee G03 on Durabilityof Nonmetallic Materials and is the direct responsibility of Subcommittee G03.02on Natural
14、Environmental Testing.Current edition approved Jan. 1, 2005. Published February 2005. Originallyapproved in 1973. Last previous edition approved in 1997 as G 24 97.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Boo
15、k of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from World Meteorological Organization, Geneva, Switzerland.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.5Available from Ame
16、rican Association of Textile Chemists and Colorists(AATCC), One Davis Dr., P.O. Box 12215, Research Triangle Park, NC 27709-2215.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.explain differences in rankings of specimens exposed toe
17、quivalent solar radiant exposure when other environmentalconditions vary.4.3 Since the method of mounting may influence the tem-perature and other parameters of the specimen during expo-sure, there should be a mutual understanding as to the methodof mounting the specimen for the particular exposure
18、test underconsideration.4.4 There can be large differences among various singlestrength window glasses in their transmission in the 300 to 350nm region. For example, at 320 nm, the percent transmissionfor seven different lots of single strength window glass rangedfrom 8.4 to 26.8 %. For this range o
19、f transmission, the rate ofdegradation for materials sensitive to short wavelength UVfrom 300 to 320 nm could vary by as much as 300 %.64.5 Differences in UV transmission between different lots ofglass persist after solarization. The largest differences amongwindow glasses in UV transmission are in
20、the spectral range of300 to 320 nm. Use of radiant exposure based on total solarradiation or total solar UV radiation to determine exposureperiods is not sensitive to these differences. For materials verysensitive to differences in short wavelength UV radiation,monitoring UVB radiation behind glass
21、may be the bestapproach for use when radiant energy is used to determine thelength of exposures. However, for materials sensitive to longwavelength UV or visible radiation, monitoring UVB radiationor using reference materials that are very sensitive to shortwavelength solar ultraviolet radiation to
22、determine exposureperiods may produce erroneous results.4.6 This practice is best used to compare the relativeperformance of materials tested at the same time behind thesame lot of glass. Because of variability between lots of glassand between exposures conducted at different times of the year,compa
23、ring the amount of degradation in materials exposed forthe same duration or radiant exposure at separate times, or inseparate fixtures using different lots of glass is not recom-mended.4.7 It is strongly recommended that at least one controlmaterial be exposed with each test. The control material sh
24、ouldbe 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 use two control materials, one withrelatively good durability, and one with relatively poor dura-bility. If control materials are included as p
25、art of the test, theyshall be used for the purpose of comparing the performance ofthe test materials relative to the controls.4.8 There are other standards which describe exposures toglass filtered daylight. Three cited standards are ISO 105-B01,ISO 877, and AATCC 16C.4.9 Because of the possibility
26、that certain materials mayoutgas during exposure, it is recommended that only similarmaterials be exposed in the same under glass cabinet.5. Apparatus5.1 Exposure Cabinet:5.1.1 Type AExposures shall be conducted in a glass-covered enclosure or cabinet of any convenient size. It shall beconstructed o
27、f wood, metal, or other satisfactory material, inorder to protect the specimens from rain and weather, and shallbe open on the back or sides to allow ambient air to circulateover the specimens (Fig. 1a and b).6Ketola, W. D., and Robbins, J.S., III, “UV Transmission of Single StrengthWindow Glass,” A
28、ccelerated 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 Well-Ventilated Under Glass Exposure Cabinet, Type AFIG. 2 Typical Enclosed Under Glass Expo
29、sure Cabinet, Type B(Black Box Under Glass)G240525.1.2 Type B (Black Box Under Glass)Exposures shall beconducted in a glass-covered enclosure or cabinet of anyconvenient size. It shall be constructed of corrosion resistantmetal and be enclosed to prevent ambient air from circulatingover specimens. E
30、xterior non-glass surfaces shall be paintedflat black. The interior shall remain unpainted (Fig. 2).NOTE 1The black box under glass test method is often used tosimulate under glass exposures under conditions of high temperature, suchas the interior of an automobile. However, because black box under
31、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 the cabinet. Frequenttemperature meas
32、urement and specimen repositioning may be required toproperly use this test method.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 SpecificationC 1036. Glass thickness shall be 2
33、to 3.2 mm.5.1.3.1 In order to reduce variability due to changes in UVtransmission 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 cabinet, for at least three mon
34、ths 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 to 20 % at 320nm and at least 8
35、5 % 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 samples recommendedby the manufact
36、urer of the UV-visible spectrophotometer used.If a spectrophotometer with an integrating sphere is used, themeasurements shall be performed in accordance with TestMethod E 903.NOTE 2Other standards describing exposures behind glass havedifferent requirements for glass transmittance and do not requir
37、e pre-aging.NOTE 3After the initial pre-aging period, the UV transmission ofwindow glass is suitable for at least 60 months of use. UV transmissiondifferences between lots of glass persist during this time, however.Different pieces of single-strength window glass can have different opticalproperties
38、 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 material.5.1.4 The enclosure or cabinet shall be eq
39、uipped 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.). Formed specimens withirregular dimensions may require custom mounting with vary-ing distances from the glass cover. In such cas
40、es, mount the testsample surface of major interest parallel to the glass cover at adistance of 75 6 25 mm (3 6 1 in.) from the glass cover. Themounting frame or plate shall be constructed of a material thatis compatible with the test specimens. In order to minimizeshadowing from the top and sides of
41、 the cabinet, the usableexposure area under the glass shall be limited to that of theglass cover reduced by twice the distance from the cover to thespecimens. Three types of mounting frames or backings maybe used.5.1.4.1 Unbacked or Open MountingSpecimens are at-tached only at edges.5.1.4.2 Expanded
42、 Aluminum MountingSpecimens are at-tached to an expanded aluminum backing.5.1.4.3 Solid MountingSpecimens are attached to a solidbacking such as plywood.NOTE 4The method used to mount specimens shall be related to theirend-use. In evaluating the specimens, the edges of these specimens thatare used t
43、o secure the specimen to the framework should be disregarded.5.1.5 The cabinet shall be located where it will receivedirect 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 theca
44、binet and the ground shall be sufficient to prevent contactwith plant growth, or to minimize damage that might occurduring 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
45、of the test.Possible exposure orientations are listed as follows:5.1.6.1 Fixed tilt angle equal to the latitude of the 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 m
46、aintainthe exposure plane normal to the suns direct beam.5.1.6.5 Any other angle that is mutually agreed on by allinterested 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 exacta
47、ngle and specimen orientation.5.2 Climatological Instruments:5.2.1 Instruments suitable for determining maximum, mini-mum, and average daily ambient air temperature, cabinet airtemperature (optional), and specimen temperature (optional).Ambient air temperature will be measured in a shielded,elevated
48、 location in the general vicinity of the under glassexposure cabinet.5.2.2 Instruments suitable for determining the maximum,minimum, and average daily ambient air humidity, and cabinethumidity (optional).5.2.3 Instruments for recording solar radiant exposure.5.2.3.1 Instrumental means of measuring f
49、ull-spectrum so-lar radiant exposure shall consist of a pyranometer connectedto an integrating device to indicate the total energy receivedover a given period. The pyranometer shall be sensitive to solarirradiance received at a geometry similar to that over whichsolar irradiance is received by the test specimens. The pyra-nometer shall be a World Meteorological Organization (WMO)Second Class instrument or better as defined by the WMOGuide to Meteorological Instruments. The pyranometer shallbe calibrated in accordance with Method E 824 no less oftenG24053than annua
