1、Designation: D4798/D4798M 10Standard Practice forAccelerated Weathering Test Conditions and Procedures forBituminous Materials (Xenon-Arc Method)1This standard is issued under the fixed designation D4798/D4798M; the number immediately following the designation indicates theyear of original adoption
2、or, in the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers test conditions and procedures forxenon-arc exposures ac
3、cording to Practices G151 and G155 forbituminous 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 either SI units or inch-pound unitsare to be regarded separately as s
4、tandard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.3 This standard does not purport to address all of thesafety concerns, if any,
5、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.2. Referenced Documents2.1 ASTM Standards:2D36 Test Method for Softening Point of Bitumen (Ring-
6、and-Ball Apparatus)D1669 Practice for Preparation of Test Panels for Acceler-ated and Outdoor Weathering of Bituminous CoatingsD1670 Test Method for Failure End Point in Acceleratedand Outdoor Weathering of Bituminous MaterialsG113 Terminology Relating to Natural andArtificial Weath-ering Tests of N
7、onmetallic MaterialsG141 Guide for Addressing Variability in Exposure Testingof Nonmetallic MaterialsG147 Practice for Conditioning and Handling of Nonmetal-lic Materials for Natural and Artificial Weathering TestsG151 Practice for Exposing Nonmetallic Materials in Ac-celerated Test Devices that Use
8、 Laboratory Light SourcesG155 Practice for Operating XenonArc LightApparatus forExposure of Non-Metallic MaterialsG169 Guide for Application of Basic Statistical Methods toWeathering Tests3. Summary of Test Method3.1 Thin films of bitumen are uniformly applied to alumi-num panels. Shingles and simil
9、ar 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 Tests conducted according to this practice are used tocompare th
10、e weathering characteristics of bituminous materialsversus a control material of known outdoor durability. It is notpossible to establish a single relationship that is applicable toall materials between time in accelerated tests conductedaccording to this practice and time in natural weatheringbecau
11、se (1) there are geographical climatic variations, localweather variations, and variations in local pollutants, and (2)the relation between accelerated and natural weathering ismaterial dependent with differences in acceleration factorsbetween materials as well as for different formulations of thesa
12、me material. Guide G141 provides guidance regarding vari-ability in outdoor and accelerated weathering tests and aboutthe use of control materials.NOTE 1It is recommended that outdoor weathering be used tovalidate the laboratory accelerated test in terms of performance ranking.NOTE 2This practice ca
13、n 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 G151 and G155.5.2 FiltersDaylight filter as described in Practice G155.1This practice is under the jur
14、isdiction ofASTM Committee D08 on Roofing andWaterproofing and is the direct responsibility of Subcommittee D08.02 on SteepRoofing Products and Assemblies.Current edition approved July 1, 2010. Published January 2011. Originallyapproved in 1988. Last previous edition approved in 2009 as D4798/D4798M
15、 09.DOI: 10.1520/D4798_D4798M-10.2For 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.1Copyright ASTM Internationa
16、l, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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 G151.6. Test Sp
17、ecimens6.1 Unless otherwise agreed upon, test specimens shall beapproximately 70 by 150 mm 234 by 578 in. Bituminousmaterials with adequate flow resistance shall be applied asuniform coatings on aluminum panels in accordance withPractice D1669. Fabricated materials such as bituminousroofing, shingle
18、s, and similar products shall be cut to size andtheir weather surfaces exposed. Bituminous materials that aretoo flexible to sustain their own weight when exposed in avertical position are permitted to be mounted on aluminumpanels using stainless steel or other non-rusting clips.6.1.1 Unless otherwi
19、se specified, expose at least three rep-licate specimens of each test and control material.6.1.2 Other test specimen sizes are permitted to be used toprovide sufficient material for postexposure testing whendesired.6.1.3 Follow the procedures described in Practice G147 foridentification, conditionin
20、g, and handling of specimens of testand control materials before, during, and 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 specime
21、n is still exposed to temperatureand humidity cycles that in many cases will affect results.7. Procedure7.1 Proceed in accordance with Section 9 of Practice G155.7.2 Water Purity:7.2.1 The purity of water used for specimen spray is veryimportant. Without proper treatment to remove cations, anions,or
22、ganics, and particularly silica, exposed panels will developspots or stains that may not occur in exterior exposures.7.2.2 Follow the requirements for water purity described inPractice G151.7.2.3 When specimens are found to have deposits or stainsafter exposure in the apparatus, the water purity mus
23、t bechecked to determine if it meets the requirements of 7.2.2.Onsome occasions, exposed specimens can be contaminated bydeposits from bacteria that can grow in the purified water usedfor specimen spray. When bacterial contamination is detected,the entire system used for specimen water spray must be
24、flushed with chlorine and thoroughly rinsed before resumingexposures.7.2.4 The 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, ru
25、n referee tests in at least one otherlaboratory that can meet the water quality requirements de-scribed in 7.2.7.3 Unless otherwise specified, operate the apparatus con-tinuously with the device programmed to control irradiance at340 nm at 0.35 W/(m2nm) and operating according to theconditions descr
26、ibed in Cycle A or Cycle B. Unless otherwisespecified, place specimens in an exposure area where irradi-ance is at least 90 % of the maximum irradiance measuredwithin the exposure area. In devices with rotating specimenracks, fill any empty spaces with blank metal panels in order toproperly maintain
27、 the conditions within the exposure area.NOTE 3Information about the exposure areas that meet the 90 %irradiance uniformity requirement is available from the manufacturers ofthe exposure devices.7.3.1 During equilibrium operation, the maximum allow-able deviation from the desired irradiance at 340 n
28、m is 60.02W/(m2nm) and the maximum allowable deviation from thedesired uninsulated black panel temperature is 62.5C. Duringequilibrium conditions, when the meter or sensor indicatingirradiance or black panel temperature shows a value that isoutside the limits described above, discontinue the test an
29、dcorrect the cause of the problem before continuing.7.3.1.1 Cycle A-151-min light-only exposure with deviceprogrammed to produce an uninsulated black panel tempera-ture of 60C at equilibrium conditions. This is followed by a9-min period with the light on and with water sprayed on thefront of the spe
30、cimens.7.3.1.2 Cycle A-2The same as Cycle A-1, except thatwater is sprayed on both the front and back surfaces of thespecimens.7.3.1.3 Cycle B-160 min with light on and water sprayedon the front of the specimens, 90 min light-only exposure, 120min with light on and water sprayed on the front of thes
31、pecimens, 990 min light-only exposure, 180 min of coldexposure. Program the device to produce an uninsulated blackpanel temperature of 60C at equilibrium conditions during thelight-only periods.7.3.1.4 Cycle B-2The same as Cycle B-1, except thatwater is sprayed on both the front and back surfaces of
32、 thespecimens.NOTE 4Typically water is sprayed only on the front surface of thespecimens. Some users operate their equipment so that water is sprayed onboth the front and back surfaces. Results between exposures conductedwith these two types of water spray may differ.7.3.1.5 For the cold exposure, p
33、anels shall be placed in afreezer that is controlled at 18C 0F. During equilibriumoperation, the maximum allowable deviation from this tem-perature is 65C 69F. The time to transfer test specimensfrom the xenon-arc device to the freezer or from the freezerback to the xenon arc device (including any t
34、ime used forinspection of the test specimens) shall not exceed 15 min. Thistime shall not be included as part of the 24 h exposure cycle.7.3.2 Some users use equipment capable of controllingchamber air temperature and/or relative humidity. When cham-ber air temperature is controlled, program the dev
35、ice to controlchamber air temperature at 44C. For exposures in whichrelative humidity is controlled, it is recommended that thedevice be programmed to control at 50 % RH. When chamberair temperature and/or relative humidity are controlled, thesetting of these parameters must be included in the test
36、report.7.3.2.1 When chamber air temperature is controlled, themaximum allowable deviation from the desired temperature is62C. When the relative humidity is controlled, the maximumallowable deviation from the desired relative humidity duringD4798/D4798M 102equilibrium conditions is 610 % RH. During e
37、quilibriumconditions, when the meter or sensor indicating chamber airtemperature or relative humidity indicates a value outside thelimits described above, discontinue the test and correct thecause of the problem before continuing.NOTE 5Historically, tests run according to this practice have been run
38、without controlling humidity or chamber air temperature. Tests run withhumidity or chamber air temperature controlled at the recommended valuemay produce different results.8. Period of Exposure and Evaluation of Test Results8.1 The duration of the exposure under this practice shall beone of the foll
39、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
40、ed upon minimum acceptable changes in eitherthe test specimen or a mutually agreed upon control sample.8.2 Changes in the exposed specimens are either evaluatedvisually at the end of each 24-h cycle by comparing them withunexposed specimens, or evaluated in terms of the number ofcycles required to p
41、roduce property changes as determined byTest Method D1670.NOTE 6When changes in properties of the test and control specimensare determined, a statistical analysis on the results is recommended todetermine if there is a difference between the test and control materials.Guide G169 provides information
42、 about the use of statistical analysis forresults from weathering exposures.9. Report9.1 In addition to the items specified in Practice G151, thereport shall include the following information:9.1.1 Cycle used (refer to this practice),9.1.2 Level of irradiance at 340 nm, uninsulated black paneltemper
43、ature, and, when controlled, relative humidity andchamber air temperature,9.1.3 Coating thickness used, and9.1.4 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. Prec
44、ision and Bias10.1 PrecisionThe repeatability 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 o
45、f the exposure/property measurement 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; bitu
46、minous materials; degrada-tion; exposure; 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
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