1、Designation: D 4141 07Standard Practice forConducting Black Box and Solar Concentrating Exposuresof Coatings1This standard is issued under the fixed designation D 4141; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of la
2、st 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 practice covers two accelerated outdoor exposureprocedures for evaluating the exterior durability of coatingsappli
3、ed to substrates.1.2 The two procedures are as follows:1.2.1 Procedure ABlack Box Exposure.1.2.2 Procedure CFresnel Reflector Rack Exposure.NOTE 1Procedure B described a Heated Black Box procedure that isno longer in common use.1.3 This standard does not cover all the procedures that areavailable to
4、 the user for accelerating the outdoor exposure ofcoatings. Other procedures have been used in order to providea particular effect; however, the two procedures described hereare widely used.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It i
5、s theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 523 Test Method for Specular GlossD 660 Test Method for Evaluating Degree of Che
6、cking ofExterior PaintsD 661 Test Method for Evaluating Degree of Cracking ofExterior PaintsD 662 Test Method for Evaluating Degree of Erosion ofExterior PaintsD 714 Test Method for Evaluating Degree of Blistering ofPaintsD 772 Test Method for Evaluating Degree of Flaking (Scal-ing) of Exterior Pain
7、tsD 823 Practices for Producing Films of Uniform Thicknessof Paint, Varnish, and Related Products on Test PanelsD 2244 Practice for Calculation of Color Tolerances andColor Differences from Instrumentally Measured ColorCoordinatesD 4214 Test Methods for Evaluating the Degree of Chalk-ing of Exterior
8、 Paint Films3D 7091 Practice for Nondestructive Measurement of DryFilm Thickness of Nonmagnetic Coatings Applied toFerrous Metals and Nonmagnetic, Nonconductive Coat-ings Applied to Non-Ferrous MetalsG7 Practice for Atmospheric Environmental ExposureTesting of Nonmetallic MaterialsG90 Practice for P
9、erforming Accelerated Outdoor Weath-ering of Nonmetallic Materials Using Concentrated Natu-ral SunlightG113 Terminology Relating to Natural and ArtificialWeathering Tests of Nonmetallic MaterialsG 141 Guide forAddressing Variability in Exposure Testingof Nonmetallic MaterialsG 147 Practice for Condi
10、tioning and Handling of Nonme-tallic Materials for Natural and Artificial Weathering TestsG 169 Guide forApplication of Basic Statistical Methods toWeathering Tests3. Terminology3.1 The definitions given in Terminology G113are appli-cable to this practice.4. Summary of Practice4.1 Several procedures
11、 are described that provide accelera-tion of the degradation that coatings evidence during naturalweathering when exposed on an open rack at a fixed angle. Theprocedures appear in the following order:4.1.1 Procedure AExposure on a black box rack facingthe equator at 5 from the horizontal.4.1.2 Proce
12、dure CExposure on a Fresnel reflector rackthat provides a high irradiance by following the sun andconcentrating sunlight on the test specimens by means ofmirrors. The specimens are wet periodically by high puritywater spray.1This practice is under the jurisdiction of ASTM Committee D01 on Paint andR
13、elated Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.27 on Accelerated Testing.Current edition approved July 1, 2007. Published July 2007. Originally approvedin 1982. Last previous edition approved in 2001 as D 4141 01.2For referenced ASTM standards, visit
14、 the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, P
15、A 19428-2959, United States.4.2 The selection of Procedure A or C is dependent onseveral factors.4.2.1 Procedure A is designed to simulate the weatheringthat occurs on horizontal insulated surfaces. Specimens aretypically flat-coated metal panels measuring 10 by 30 cm (4 by12 in.) or 15 by 30 cm (6
16、by 12 in.).NOTE 2Procedure A is specified in standards used by the automotiveindustry.4.2.2 Procedure C is designed to simulate weathering onboth automotive and nonautomotive products. Procedure Ctypically provides faster results than Procedure A on a calendarbasis.45. Significance and Use5.1 As wit
17、h any accelerated test, the increase in rate ofweathering compared to in service exposure is material depen-dent. Therefore, no single acceleration factor can be used torelate two different types of outdoor weathering exposures. Thedurability rankings of coatings provided by these two proce-dures ma
18、y not agree when coatings differing in composition arecompared. These two procedures should not be used inter-changeably.5.2 The procedures described in this practice are designed toprovide greater degradation rates of coatings than those pro-vided by fixed angle open-rack outdoor exposure racks. Fo
19、rmany products, fixed angle exposures will produce higherdegradation rates than the normal end use of the material.5.2.1 The use of Procedure A (Black Box) instead of anopen-rack direct exposure is a more realistic test for materialswith higher temperature end use service conditions.NOTE 3Procedure
20、A (Black Box)For many coatings, this procedureprovides greater rates of degradation than those provided by 5, equator-facing, open-rack exposures because the black box produces higherspecimen temperatures during irradiation by daylight and longer time ofwetness. The black box specimen temperatures a
21、re comparable to thoseencountered on the hoods, roofs, and deck lids of automobiles parkedsunlight. The relative rates of gloss loss and color change produced insome automotive coatings by exposures in accordance with Procedure Aare given in ASTM STP 781.5NOTE 4Procedure C (Fresnel Reflector Rack)Th
22、e acceleration ofProcedure C is produced by reflecting sunlight from ten mirrors onto anair-cooled specimen area. In the ultraviolet portion of the solar spectrum,approximately 1400 MJ/m2of ultraviolet radiant exposure (295 to 385nm) is received over a typical one-year period when these devices areo
23、perated in a central Arizona climate. This compares with approximately333 MJ/m2of ultraviolet radiant exposure from a central Arizonaat-latitude exposure and 280 MJ/m2of ultraviolet radiant exposure from asouthern Florida at-latitude exposure over the same time period. However,the test described by
24、Procedure C reflects only direct beam radiation ontotest specimens. The reflected direct beam sunlight contains a lowerpercentage of short wavelength ultraviolet radiation than global daylightbecause short wavelength ultraviolet is more easily scattered by theatmosphere, and because mirrors are typi
25、cally less efficient at shorterultraviolet wavelengths. Ultraviolet radiant exposure levels should not beused to compute acceleration factors since acceleration is materialdependent.5.3 The durability of coatings in outdoor use can be verydifferent depending on the location of the exposure because o
26、fdifferences in ultraviolet (UV) radiation, time of wetness,temperature, pollutants, and other factors. Therefore, it cannotbe assumed that results from one exposure in a single locationwill be useful for determining relative durability in a differentlocation. Exposures in several locations with dif
27、ferent climatesthat represent a broad range of anticipated service conditionsare recommended.5.4 Because of year-to-year climatological variations, re-sults from a single exposure test cannot be used to predict theabsolute rate at which a material degrades.NOTE 5Several years of repeat exposures are
28、 typically needed to getan “average” test result for a given location.5.4.1 The degradation profile for many polymers is not alinear function of exposure time or radiant exposure. Whenshort exposures are used to predict the service life or asindications of durability, the results obtained may not be
29、representative of those from longer exposures.NOTE 6Guide G 141 provides information for addressing variabilityin exposure testing of nonmetallic materials. Guide G 169 providesinformation for applying statistics to exposure test results.5.5 It is recommended that at least one control material bepar
30、t of any exposure evaluation. Control materials are used forcomparing the performance of the test materials relative to thecontrols when materials are not being ranked against oneanother. The control material used should be of similarcomposition and construction to the test materials and be ofknown
31、durability. It is preferable to use two control materials,one with relatively good durability and one with poor durabil-ity.6. Test Specimens6.1 Each test specimen and control specimen shall consist ofa uniform coating applied to the surface of a rigid panel.Suitable application procedures are given
32、 in Practices D 823.6.2 Use flat specimens, because warpage, waviness, orcurvature may seriously affect the measurements of gloss andcolor and may produce a poor air seal on the black box rack.6.3 For Procedure C, specimen sizes are typically limited toa maximum of 13 cm (5 in.) in one dimension, an
33、d a maximumof 140 cm (55 in.) in the other dimension. However, specimensare typically 7.5 by 13 cm (3 by 5 in.) or 5 by 13 cm (2 by 5in.). Because air cooling is used to prevent high specimentemperatures, specimens must be flat. A thickness of less than0.6 cm (0.25 in.) is preferred. This practice m
34、ay not apply tospecimens thicker than 1.3 cm (0.5 in.) because cooling may bequestionable.6.4 Prepare controls for inclusion in each exposure series toact as comparison standards and to provide a means fordetermining the severity of the exposure conditions encoun-tered by the series. For best result
35、s, there should be at least twocontrols differing in their durability performance.6.5 Optionally, using Test Method D 7091, measure the dryfilm thickness of the coatings at several different positions onthe test specimens.4Zerlaut, G.A., Rupp, M.W., and Anderson, T.E., “Ultraviolet Radiation as aTim
36、ing Technique for Outdoor Weathering of Materials,” Paper 850378, Proceed-ings, SAE International Congress, Detroit, February 25, 1985.5Symposium on Permanence of Organic Coatings, ASTM STP 781, ASTM,1982.D41410726.6 Unless otherwise specified, expose at least two repli-cates. Larger numbers of repl
37、icates are recommended.PROCEDURE ABLACK BOX EXPOSURE7. Apparatus7.1 Black Box, constructed of materials in accordance withPractice G7, or its equivalent, and positioned so that thesurfaces of the test specimens are 5 from the horizontal, facingthe equator (Figs. 1 and 2).8. Procedure8.1 Use Practice
38、 G 147 for specimen handling and condi-tioning procedures for test specimens.8.2 If a change in gloss is to be measured, determine thespecular gloss value for each unexposed specimen using aproperly calibrated glossmeter in accordance with Test MethodD 523.8.3 If a change in color is to be measured,
39、 determine thedelta (change in) color coordinates for each unexposed speci-men using Practice D 2244. Unless otherwise agreed upon, usethe CIE Lab Color Scale. The color measuring instrument shallbe stable and properly calibrated.NOTE 7As an alternative procedure, reserve unexposed duplicatespecimen
40、 panels of each coating as file specimens to determine the colorchange of the exposed specimens. To minimize color drift, store the panelsin a dark, room-temperature environment.8.4 Mount and fasten the specimens on the exposure box.Cover all empty spaces on the black box using black panels sothat t
41、he entire surface is covered.NOTE 8The predominant color of the specimens on the black boxshould be noted.Ablack box will attain a lower temperature if all the otherspecimens are white than if the other specimens are black.8.4.1 Non-rigid specimens shall be backed to keep speci-mens from sagging and
42、 to ensure that there are no gapsbetween specimens. The backing material used can be eitherflattened-mesh expanded metal sheet or solid sheet made froma corrosion-resistant material such as aluminum or stainlesssteel. If specimens are backed, the backing material used shallbe specified in the report
43、.8.5 Expose the test and control specimens for a specifiedperiod of time on the basis of one of the following:8.5.1 Expose for a specified number of days, months, oryears with respect to an agreed upon starting date.8.5.2 Expose for a specified quantity of radiant exposureeither total, typically mea
44、sured from 300 to 3000 nm, orultraviolet, typically measured from 295 to 385 nm. Whensolar ultraviolet radiation is measured, use a total ultravioletradiometer that measures ultraviolet in the wavelength regionfrom 295 to 385 nm. Optionally, ultraviolet can be measured inthe wavelength region from 3
45、00 to 400 nm. Calibrate theradiometer and readout system in suitable radiometric units,and maintain in at least annual calibration against a standardsource of spectral irradiance.8.5.3 Expose until a specified change has occurred in thetest specimens.8.5.4 Expose until a specified change has occurre
46、d in acontrol exposed with the test specimens.8.5.5 In most cases, periodic evaluation of test and controlmaterials is necessary to determine the variation in magnitudeand direction of property change as a function of time orradiant exposure.8.6 Unless otherwise agreed upon, remove the test speci-me
47、ns from the black box and gently wash a portion of thespecimen surfaces to remove loose dirt. The same portion ofthe specimen should be washed at each interval of exposure. Asuitable procedure consists of gentle rubbing with a sponge wetwith high purity water or a dilute solution of a nonionicdeterg
48、ent, followed by a high purity water rinse. The high-purity water shall meet as a minimum the requirements forwater purity contained in Practice G90.8.7 If required, perform one or more of the following testson the washed portion of each washed specimen:8.7.1 Measure the specular gloss in accordance
49、 with TestMethod D 523.8.7.2 Calculate the color difference in accordance withPractice D 2244 based on instrumental measurements of colorbefore and after exposure.8.7.3 Evaluate checking and cracking rating in accordancewith Test Methods D 660 and D 661.8.7.4 Evaluate blistering rating in accordance with TestMethod D 714.8.7.5 Evaluate erosion rating in accordance with TestMethod D 662.8.7.6 Evaluate flaking rating in accordance with TestMethod D 772.8.7.7 Use any other agreed upon test methods for evaluatingspecimens.8.8 If required, perform a chalk rating in accord
