1、Designation: D 4798 04Standard 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 D 36. (Also see TerminologyG 113.)1.2 The values stated in SI units are to be regarded as thestandard. The values given in parenthese
4、s 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 pr
5、ior to use.2. Referenced Documents2.1 ASTM Standards:2D 36 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 Outdo
6、or Weathering of Bituminous MaterialsG 113 Terminology Relating to Natural and ArtificialWeathering Tests of Nonmetallic MaterialsG 141 Guide for Addressing Variability in Exposure Testingon Nonmetallic MaterialsG 147 Practice for Conditioning and Handling of Nonme-tallic Materials for Natural and A
7、rtificial 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 Nonmetallic Materials3. Summary of Test Method3.1 Thin films of bitumen are uniformly applie
8、d to 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 e
9、stablish a precise correlationbetween accelerated and natural weathering because of geo-graphical climatic variations, local weather variation fromnormal, and local pollutants. This weathering apparatus andprocedure are used for comparing the weathering characteris-tics of bituminous materials again
10、st a reference material forwhich the outdoor weathering characteristics are known. GuideG 141 provides guidance regarding this issue.5. Apparatus5.1 The xenon-arc apparatus used shall conform to therequirements defined in Practices G 151 and G 155.5.2 FiltersDaylight filter as described in Practice
11、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 specimens shall beapproximately 70
12、 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 exposed. If theseare too flexibl
13、e 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 test and control material.6.1.2 Other test specimen sizes may be used to providesufficient material for postexposure testin
14、g when desired.1This practice is under the jurisdiction of ASTM Committee D08 on Roofing andWaterproofing and is the direct responsibility of Subcommittee D08.02 on PreparedRoofings, Shingles, and Siding Materials.Current edition approved Nov. 1, 2004. Published November 2004. Originallyapproved in
15、1988. Last previous edition approved in 2001 as D 4798 01.2For 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.1Co
16、pyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.1.3 Follow the procedures described in Practice G 147 foridentification, conditioning, and handling of specimens of test,control, and reference materials before, during, and afterexposur
17、e.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 affect results
18、.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 that may not o
19、ccur 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 someoccasions, exposed s
20、pecimens 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 The temperature
21、 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 quality requirem
22、ents 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 W/(m2nm) at 340 nm.7.3.1 Cycle A51-min light exposure, 9-min light andwater spray; uninsulated black panel temperature (60 6 3C)
23、.7.3.2 Cycle B60-min water spray, 90-min light exposure,120-min water spray, 990-min light exposure, 180-min coldexposure; uninsulated black panel temperature (60 6 3C).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 C
24、ycle B, the panelsshall be placed in the refrigerator, previously cooled to 18 65C (0 6 10F). If inspection of the panels is to be 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 inspec
25、tion of the panels is notperformed, the transfer of the panels from the exposureapparatus to the refrigerator, and following this period, 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 cyc
26、le.8. Period of Exposure and Evaluation of Test Results8.1 The duration of the exposure under this practice shall beone of the following: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 amu
27、tually agreed upon minimum amount of change in the testspecimen, or8.1.3 The number of 24-h cycles required to producemutually agreed 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
28、 the end of each 24-h cycle by comparing them withunexposed samples, or in terms of the number of cyclesrequired to produce physical 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 infor
29、mation:9.1.1 Cycle used (refer to this practice),9.1.2 Level of irradiation used,9.1.3 Coating thickness used, and9.1.4 Method of sample rotation used.10. Precision and Bias10.1 PrecisionThe repeatability of results obtained inexposures conducted according to this practice will vary withthe material
30、s 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 measurement process when using the results fromexposures conducted according to this practice in productspecification
31、s.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; exposure; light exposure; roofing; ultraviolet; waterproof-ing; xenon-arcD4798042ASTM International takes no
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35、ess 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).D4798043
