1、Designation: D 4364 05Standard Practice forPerforming Outdoor Accelerated Weathering Tests ofPlastics Using Concentrated Sunlight1This standard is issued under the fixed designation D 4364; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, 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. Scope*1.1 This practice covers the use of Fresnel-reflecting con-centrators that use the sun as a source of
3、 ultraviolet (UV) andlonger wavelength radiation. Such devices are used in theoutdoor accelerated exposure testing of plastics.1.2 This practice provides a procedure for performing out-door accelerated exposure testing of plastics using a Fresnel-reflector outdoor accelerated weathering test machine
4、. Theapparatus is described herein and in Practice G90 morecompletely.1.3 This practice is applicable to a range of plastic materialsincluding, but not limited to, plastic films, sheets, laminates,and extruded and molded products in a variety of shapes andsizes, as specified in 8.2 and 8.3.1.4 This
5、practice describes test conditions that attempt tosimulate plastics exposures in desert and subtropical climates.Specimen preparation, property testing procedures, and theevaluation of results are covered in existing test methods orspecifications for specific materials.1.5 This standard does not pur
6、port 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 determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given
7、 in Section 7.NOTE 1This standard and ISO 877.2-1991, Method C, are technicallyequivalent.2. Referenced Documents2.1 ASTM Standards:2D 859 Test Method for Silica in WaterD 883 Terminology Relating to PlasticsD 1435 Practice for Outdoor Weathering of PlasticsD 1600 Terminology for Abbreviated Terms R
8、elating toPlasticsD 1898 Practice for Sampling of Plastics3D 4141 Practice for ConductingAccelerated Outdoor Expo-sure Tests of CoatingsD 4517 Test Method for Low-Level Total Silica in High-Purity Water by Flameless Atomic Absorption Spectros-copyE 772 Terminology Relating to Solar Energy Conversion
9、E 824 Method for Transfer of Calibration from Reference toField PyranometersG7 Practice for Atmospheric Environmental ExposureTesting of Nonmetallic MaterialsG24 Practice for Conducting Natural Light Exposures Un-der GlassG90 Practice for Performing Accelerated Outdoor Weath-ering of Nonmetallic Mat
10、erials Using Concentrated Natu-ral SunlightG113 Terminology Relating to Natural and ArtificialWeathering Tests of Nonmetallic Materials2.2 ISO Standard:4ISO 877.2-1991, Method C, Methods of Exposure to DirectWeathering, to Weathering Using Glass-Filtered Daylight,and to Intensified Weathering Using
11、Fresnel Mirrors3. Terminology3.1 DefinitionsFor definitions of technical terms pertain-ing to plastics used in this practice, see Terminologies D 883,D 1600, E 772, and G113(for weathering terminology).4. Significance and Use4.1 This practice involves the concentration of sunlight by asystem of plan
12、e mirrors, arranged to simulate a parabolictrough focused on an air-cooled target board on which the testspecimens are mounted. Exposure cycles with and withoutwater spray that are commonly used for this method aredescribed in Table 1. Other exposure cycles not listed in Table1 can be used, upon con
13、sensual agreement between interestedparties.4.1.1 Accelerated outdoor exposure tests performed usingthis practice in an absence of a programmed moisture cycle are1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.50 on Durabi
14、lity of Plastics.Current edition approved September 15, 2005. Published October 2005. Origi-nally approved in 1984. Last previous edition approved in 2002 as D 4364 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual
15、 Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1*A Summary of Changes section appears at the end of this standard.Copyrigh
16、t ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.intended to simulate conventional exposure testing on racksfacing the equator in desert and arid regions.4.1.2 Accelerated outdoor exposure tests performed usingthis practice with a programmed m
17、oisture cycle shall possessthe feature of spraying high purity water on the specimens in aregular, periodic fashion that is intended to simulate the resultsof conventional exposure testing on fixed racks facing theequator in subtropical, semi-humid, and temperate regions.Water-spray cycles that are
18、recommended by this practice aregiven in Table 1.4.2 The effectiveness of the Fresnel-reflector acceleratedoutdoor weathering test machines depends primarily on theamount and character of the UV in the direct-beam componentof sunlight.NOTE 2Use of the apparatus in regions of moderate- to high-diffus
19、eirradiance will reduce the test machines effectiveness substantially forproviding concentrated UV in the target (specimen) area.4.3 Testing to specific levels (quantities) of solar ultravioletradiant exposure is recommended. Elapsed time exposure-leveldeterminations shall not be used for testing wi
20、th this practice.Testing to specific levels of UV irradiation, whether to total UVor within selected wavebands, is an effective method forimproving agreement between wintertime and summertimetesting on the Fresnel-reflector weathering-test machines.Other seasonal factors such as temperature and time
21、 of wetnesscan affect the weathering of test specimens significantly.4.4 The weathering machines described provide for speci-men cooling that reduces thermal problems in most materials.It is recommended that monthly temperature measurements beperformed on heat-sensitive plastics to record the typica
22、lmonthly test specimen temperatures.NOTE 3It is possible for heat-sensitive plastic materials and thickspecimens that are self-insulating to exhibit thermal-induced degradationthat is unrealistic compared to natural weathering. Clear, thin-filmphotodegradable plastics are not recommended for testing
23、 with thispractice for this reason.4.5 Since the natural environment varies with respect totime, geography, and topography, it can be expected that theeffects of natural exposure will vary accordingly. Furthermore,all materials are not affected equally by increased irradianceand temperature. The qua
24、ntitative correlation between expo-sures conducted in accordance with this practice and thoseconducted under specified natural exposure conditions willtherefore vary with the type and composition of the material.4.6 While reference materials tested in accordance with thispractice and Practices G 7 a
25、nd D 1435 are useful for providinginformation on the relationship between accelerated and real-time tests, the acceleration factor found for the referencematerial cannot be used to extrapolate results of the acceleratedtest to predict lifetimes under natural exposure except for thespecific material
26、for which the relationship has been estab-lished.5. Apparatus5.1 The testing apparatus shall be a Fresnel-reflecting de-vice possessing ten flat mirrors that focus direct sunlight ontoan air-cooled specimen area. A more complete description ofthe apparatus can be found in Practice G90. See Fig. 1.NO
27、TE 4The apparatus should be operated in dry, sunny climatesreceiving 3500 to 4000 h or more of sunshine per year and an averageannual relative humidity of approximately 30 % or less.5.2 Water Quality:5.2.1 The purity of water used for specimen spray is veryimportant. Without proper treatment to remo
28、ve cations, anions,TABLE 1 Fresnel-Reflector Test Machine Standard Spray CyclesCycleDaytime NighttimeSpray Duration Dry-Time Duration Cycles, h Spray Duration Dry-Time Duration Cycles, hWater is sprayed on the test specimens at:1 8 min 52 min 1 8 min 172 min 9:00 p.m.12:00 midnight3:00 a.m.2 no wate
29、r spray used no water sprayused3Ano water spray used 3 min 12 min 4 cycles per hour(from 7PM to 5 AM)AThis is the cycle specified in Procedure C of Practice D 4141.FIG. 1 Schematic of a Fresnel-Reflecting Concentrator-Accelerated Weathering MachineD4364052organics, and particularly silica, exposed p
30、anels will developspots or stains that do not occur in exterior exposures.5.2.2 Water used for specimen spray shall leave no objec-tionable deposits or stains on the exposed specimens. It isstrongly recommended that the water contain below 1 ppmsolids and below 0.2 ppm silica. Silica levels should b
31、edetermined in accordance with the procedures in Test MethodsD 859 or D 4517. Prepackaged analysis kits are commerciallyavailable that are capable of detecting silica levels of below200 ppb. A combination of deionization and reverse-osmosistreatment can produce water with the desired purity effectiv
32、ely.The solids and silica levels must be reported if the spray waterused is above 1 ppm solids.5.2.3 If specimens are found to have deposits or stains afterexposure in the apparatus, the water purity must be checked todetermine if it meets the requirements above. On someoccasions, exposed specimens
33、can be contaminated by depositsfrom bacteria that can grow in the purified water used forspecimen spray. If bacterial contamination is detected, theentire system used for specimen spray must be flushed withchlorine and thoroughly rinsed before resuming exposures.Although it does not always correlate
34、 with silica content, it isrecommended that resistivity of water used for specimen spraybe continuously monitored and that exposures be discontinuedwhenever the resistivity falls below 1 MV.6. Reagents and Materials6.1 Water shall conform to the specifications presented in5.2.1-5.2.3.6.2 The mirrors
35、 used on Fresnel-reflector test machinesshall be flat and have a specular UV reflectance of 65 % orgreater at 310 nm wavelength.7. Safety Precautions7.1 Suitable eye protection shall be required when workingwith Fresnel-reflector test machines to prevent UV and infrareddamage. Manipulation of the re
36、flectors for daily maintenance,or for the purpose of specimen mounting, dismounting, andinspection, can reflect the concentrated sunlight on the faceaccidentally. The use of sunglasses that absorb most of the UVradiation below 360-nm wavelength is essential; aluminizedglasses will prevent accidental
37、 burning of the retina byinfrared.7.2 Suitable clothing or sunscreen ointments having an SPFof 15 or higher, or both, should be used to cover exposed skinfor persons working with the test machines described in thispractice.7.3 The squirrel-cage blower shall be covered with a heavy-duty protective sc
38、reen to prevent accidental injury and to keeploose clothing from the fan during startup, shutdown, mainte-nance, inspection, or specimen exchange.8. Test Specimens8.1 It is strongly recommended that users of this acceleratedoutdoor exposure practice follow the statistical procedures forsampling pres
39、ented in Practice D 1898.8.2 The target dimensions presently used for most Fresnel-reflector accelerated weathering machines are 130 by 1400mm. The target dimensions shall dictate the test specimendimensions.8.3 It is strongly recommended that the maximum specimenthickness used is 13 mm. The air coo
40、ling process and mecha-nism dictates that the thickness of test specimens be limited to13 mm. The adequacy of cooling can be questionable for testspecimens thicker than 13 mm.8.4 Test specimens smaller than the maximum size shall bearranged as shown in Practice G90.9. Procedures9.1 Mounting:9.1.1 Mo
41、unt the test specimens in a suitable frame such thata minimum of the test specimen is covered by the clampingfixture used.NOTE 5Amasked area or specimen overlapping should not be used inan attempt to estimate the effects of a dark exposure at the sametemperature since a masked area or specimen overl
42、apping is not unex-posed and the temperature may actually be higher than the unmaskedareas.9.1.2 Mount the framed test specimens approximately 5 mmoff the target board. Position the specimen such that adequateclearance is maintained between the air delivery slot and theframe.Adjust the machines air
43、deflector to provide a clearancefrom 6 to 13 mm between the exposed surface of the testspecimen and the air deflector lip. Plastic test specimens withwidely disparate thicknesses shall not be mounted on the sametest machine in order to provide for uniform cooling.9.1.3 When mounting plastic specimen
44、s under glass tosimulate the types of exposures under glass covered in PracticeG24, ensure that the solar spectral transmittance (particularlyin the UV region from 295 to 385-nm wavelength) of the glassused is essentially identical to that used in natural weatheringwith which it is being compared, o
45、r that its spectral transmit-tance is that required for the application. Mount the glasscovers, or plastic transparencies (if the application calls for atransparency other than glass), such that they cover the entirespecimen with respect to the reflected light from all of themirrors. Mount the trans
46、parent covers at a distance of 25 to 32mm from the specimen surface. Common practice is to mountthe transparent cover at a distance of 25 mm from flat, plasticspecimens, and to use a greater distance for non-flat specimens(see Fig. 2). This distance is close enough to the specimen toblock all reflec
47、ted solar irradiance and still allows for adequatecooling.NOTE 6Under-glass (or under-plastic) exposure tests in accordancewith 4.1.1 require careful adjustment of the cooling vanes (etc.) to achieveadequate specimen cooling. Specimen temperature and air velocitymeasurements can be used to verify wh
48、ether the specimens have adequatecooling.9.2 Operation:9.2.1 Begin the test by moving the Fresnel device to solaracquisition. Actuate the water-spray system as required. SeeTable 1 for selection of spray schedule. Record the solarirradiance data while the device is operated.D43640539.2.2 Perform the
49、 testing in accordance with the dailyschedule described in Practice G90.9.2.3 Measure the direct beam solar radiation using a solartracking 6 pyrheliometer. This solar radiometer shall becalibrated at least annually in accordance with Test MethodE 824.9.3 Expose the specimens for a predetermined amount ofUV radiant exposure measured in joules per square metre.Determine the solar-radiant exposure of the test specimens inaccordance with the following formulae:Hs5 Mrs (i 5 1NHd(1)rs5rM(i 5 1Mcos ui(2)where:Hs= solar radiant exposure, J/m2,M = number of mirrors,rs= cosine-corre
