1、Designation: D 4798 08Standard Practice forAccelerated Weathering Test Conditions and Procedures forBituminous Materials (Xenon-Arc Method)1This standard is issued under the fixed designation D 4798; the number immediately following the designation indicates the year oforiginal adoption or, in the c
2、ase of revision, 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. Scope1.1 This practice covers test conditions and procedures forxenon-arc exposures according to
3、Practices G 151 and G 155for bituminous roofing and waterproofing materials that have aminimum softening point of approximately 95C (200F) asdetermined by Test Method D36. (Also see TerminologyG113.)1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses
4、are for informationonly.1.3 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 determine the applica-bility of regulatory limitations prio
5、r to use.2. Referenced Documents2.1 ASTM Standards:2D36 Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus)D 1669 Practice for Preparation of Test Panels for Acceler-ated and Outdoor Weathering of Bituminous CoatingsD 1670 Test Method for Failure End Point in Acceleratedand Outdoor
6、Weathering of Bituminous MaterialsG113 Terminology Relating to Natural and ArtificialWeathering Tests of Nonmetallic MaterialsG 141 Guide forAddressing Variability in Exposure Testingof Nonmetallic MaterialsG 147 Practice for Conditioning and Handling of Nonme-tallic Materials for Natural and Artifi
7、cial Weathering TestsG 151 Practice for Exposing Nonmetallic Materials in Ac-celerated Test Devices that Use Laboratory Light SourcesG 155 Practice for Operating Xenon Arc Light Apparatusfor Exposure of Non-Metallic Materials3. Summary of Test Method3.1 Thin films of bitumen are uniformly applied to
8、 alumi-num panels. Shingles and similar products are cut to size andexposed to specified cycles of temperature, light, and water. Achoice of two test cycles is given along with options fordetermining the period of exposure and evaluating results.4. Significance and Use4.1 It is not possible to estab
9、lish a precise correlationbetween accelerated and natural weathering because (1) thereare geographical climatic variations, local weather variations,and variations in local pollutants, and (2) the relation betweenaccelerated and natural weathering is material dependent withdifferences in acceleratio
10、n factors between materials as well asfor different formulations of the same material. This weather-ing apparatus and procedure are used for comparing theweathering characteristics of bituminous materials against acontrol material for which the outdoor weathering characteris-tics are known. Guide G
11、141 provides guidance regarding thisissue.NOTE 1This practice can be used for other than bituminous materials,but the significance and use have not been evaluated.5. Apparatus5.1 The xenon-arc apparatus used shall conform to therequirements defined in Practices G 151 and G 155.5.2 FiltersDaylight fi
12、lter as described in Practice G 155.5.3 RadiometerThe use of a radiometer to monitor andcontrol the amount of radiant energy received at the specimenis required. The use of the radiometer shall comply with therequirements in Practice G 151.6. Test Specimens6.1 Unless otherwise agreed upon, test spec
13、imens shall beapproximately 70 by 150 mm (234 by 578 in.). Bituminousmaterials shall be applied as uniform coatings on aluminumpanels in accordance with Practice D 1669. Fabricated materi-als such as bituminous roofing, shingles, and similar productsshall be cut to size and their weather surfaces ex
14、posed. If these1This practice is under the jurisdiction ofASTM Committee D08 on Roofing andWaterproofing and is the direct responsibility of Subcommittee D08.02 on PreparedRoofings, Shingles and Siding Materials.Current edition approved Feb. 1, 2008. Published March 2008. Originallyapproved in 1988.
15、 Last previous edition approved in 2004 as D 4798 04.2For referenced ASTM standards, visit 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.1Copyrig
16、ht ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.are too flexible to sustain their own weight in a verticalposition, they may be mounted on aluminum panels.6.1.1 Unless otherwise specified, expose at least three rep-licate specimens of each t
17、est and control material.6.1.2 Other test specimen sizes may be used to providesufficient material for postexposure testing when desired.6.1.3 Follow the procedures described in Practice G 147 foridentification, conditioning, and handling of specimens of testand control materials before, during, and
18、 after exposure.6.1.4 Do not mask the face of a specimen for the purpose ofshowing on one panel the effects of various exposure times.Misleading results may be obtained by this method, since themasked portion of the specimen is still exposed to temperatureand humidity cycles that in many cases will
19、affect results.7. Procedure7.1 Proceed in accordance with Section 9 of Practice G 155.7.2 Water Purity:7.2.1 The purity of water used for specimen spray is veryimportant. Without proper treatment to remove cations, anions,organics, and particularly silica, exposed panels will developspots or stains
20、that may not occur in exterior exposures.7.2.2 Follow the requirements for water purity described inPractice G 151.7.2.3 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 of 7.2.2. On someoccasi
21、ons, exposed specimens 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 water spray must be flushedwith chlorine and thoroughly rinsed before resuming expo-sures.7.2.4 T
22、he temperature of water used for specimen sprayshall be 7.2 6 3C (45 6 5F).7.2.5 When the water purity requirements above are met andthere is disagreement between parties on the extent of problemscaused by stain or deposit, run referee tests in at least one otherlaboratory that can meet the water qu
23、ality requirements de-scribed in 7.2.7.3 Unless otherwise specified, operate the apparatus con-tinuously according to one of the following schedules for 24 hat a light intensity of 0.35 6 0.02 W/(m2nm) at 340 nm.Specimens should be confined to an exposure area in which theirradiance is at least 90 %
24、 of the irradiance at the center of theexposure area. Unless it is known that irradiance uniformitymeets this requirement, use one of the procedures described inPractice G 155, Section 9.5, to ensure equal radiant exposureon all specimens or to compensate for differences within theexposure chamber.
25、If the specimens do not completely fill theracks, fill the empty spaces with blank metal panels to maintainthe test conditions within the chamber. The chamber airtemperature shall be set at 44 6 2C in equipment that allowsfor its adjustment.NOTE 2For exposures in which relative humidity is controlle
26、d, therecommended setting is 50 6 10 % during the dry period of exposure tolight.7.3.1 Cycle A51-min light only exposure, 9-min light andwater spray; uninsulated black panel temperature during thelight only period shall be 60 6 2.5C.7.3.2 Cycle B60-min light and water spray, 90-min lightonly exposur
27、e, 120-min light and water spray, 990-min lightonly exposure, 180-min cold exposure; uninsulated black paneltemperature during the light only period shall be 60 6 2.5C.NOTE 3Water is sprayed on the front surface of the exposed speci-mens and can also be sprayed on the back surface, if desired, to ma
28、ximizethermal shock on the tested specimens.NOTE 4The operational fluctuations, that is, the positive and negativedeviations from the specified set points for the irradiance, temperature,and relative humidity, are allowable deviations from the set points duringequilibrium operation of the equipment.
29、 They do not imply that the useris allowed to program a set point higher or lower than that specified.Operate the apparatus to maintain the allowable operational fluctuations.If the latter are greater than the maximum allowable after the equipmenthas stabilized, discontinue the test and correct the
30、cause of the problembefore continuing.7.3.3 The 24-h cycle requires automatic control of theperiods of light and light with spray.7.3.4 For the cold exposure period in Cycle B, the panelsshall be placed in the refrigerator, previously cooled to 18 65C (0 6 10F). If inspection of the panels is to be
31、performedat any stage in the cycle or sequence of cycles, the interruptionof the test procedure should take only sufficient time to allowfor such inspection. When inspection of the panels is notperformed, the transfer of the panels from the exposureapparatus to the refrigerator, and following this p
32、eriod, back tothe test chamber, shall not require more than 15 min.7.3.5 The time taken for inspection of the panels shall not becounted as part of the 24-h exposure cycle.8. Period of Exposure and Evaluation of Test Results8.1 The duration of the exposure under this practice shall beone of the foll
33、owing:8.1.1 A mutually agreed upon number of 24-h cycles ofoperation in accordance with either Cycle A or Cycle B,8.1.2 The number of 24-h cycles required to produce amutually agreed upon minimum amount of change in the testspecimen, or8.1.3 The number of 24-h cycles required to producemutually agre
34、ed upon minimum acceptable changes in eitherthe test specimen or a mutually agreed upon reference sample.8.2 Changes in the exposed specimens may be evaluatedvisually at the end of each 24-h cycle by comparing them withunexposed samples, or in terms of the number of cyclesrequired to produce physica
35、l or chemical changes as deter-mined by Test Method D 1670.9. Report9.1 In addition to the items specified in Practice G 151, thereport shall include the following information:9.1.1 Cycle used (refer to this practice),9.1.2 Level of irradiation used and temperature, and, ifcontrolled, relative humid
36、ity and chamber air temperature,9.1.3 Coating thickness used, andD47980829.1.4 Method of sample repositioning, if used, or othermeans of assuring equal radiant exposure on all specimens orcompensation for differences in irradiance within the exposurechamber.10. Precision and Bias10.1 PrecisionThe re
37、peatability of results obtained inexposures conducted according to this practice will vary withthe materials being tested, the material property being mea-sured, and the specific test conditions and cycles that are used.It is essential to determine reproducibility of the exposure/property measuremen
38、t process when using the results fromexposures conducted according to this practice in productspecifications.10.2 BiasBias cannot be determined because no accept-able standard weathering reference materials are available.11. Keywords11.1 accelerated weathering; bituminous materials; degrada-tion; ex
39、posure; light exposure; roofing; ultraviolet; waterproof-ing; xenon-arcASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of
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42、ived a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D4798083
