1、Designation: D4798/D4798M 11 (Reapproved 2016)Standard 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
2、original adoption 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 forxeno
3、n-arc exposures according to Practices G151 and G155 forbituminous roofing and waterproofing materials. (See Termi-nology G113.)1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefo
4、re, 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, associated with its use. It is theresponsibility of the user of this standard
5、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:2D1669/D1669M Practice for Preparation of Test Panels forAccelerated and Outdoor Weathering of Bituminous Coat-ingsD1670/D1670M Test
6、 Method for Failure End Point in Ac-celerated and Outdoor Weathering of Bituminous Materi-alsG113 Terminology Relating to Natural and Artificial Weath-ering Tests of Nonmetallic MaterialsG141 Guide for Addressing Variability in Exposure Testingof Nonmetallic MaterialsG147 Practice for Conditioning a
7、nd Handling of Nonmetal-lic Materials for Natural and Artificial Weathering TestsG151 Practice for Exposing Nonmetallic Materials in Accel-erated Test Devices that Use Laboratory Light SourcesG155 Practice for Operating Xenon Arc Light Apparatus forExposure of Non-Metallic MaterialsG169 Guide for Ap
8、plication of Basic Statistical Methods toWeathering Tests3. Summary of Test Method3.1 Thin films of bitumen are uniformly applied 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 al
9、ong with options fordetermining the period of exposure and evaluating results.4. Significance and Use4.1 Tests conducted according to this practice are used tocompare the weathering characteristics of bituminous materialsversus a control material of known outdoor durability. It is notpossible to est
10、ablish a single relationship that is applicable toall materials between time in accelerated tests conductedaccording to this practice and time in natural weatheringbecause (1) there are geographical climatic variations, localweather variations, and variations in local pollutants, and (2)the relation
11、 between accelerated and natural weathering ismaterial dependent with differences in acceleration factorsbetween materials as well as for different formulations of thesame material. Guide G141 provides guidance regarding vari-ability in outdoor and accelerated weathering tests and aboutthe use of co
12、ntrol materials.NOTE 1It is recommended that outdoor weathering be used to validatethe laboratory accelerated test in terms of performance ranking.NOTE 2This practice can be used for other than bituminous materials,but the significance and use have not been evaluated.5. Apparatus5.1 The xenon-arc ap
13、paratus used shall conform to therequirements defined in Practices G151 and G155.5.2 FiltersDaylight filter as described in Practice G155.5.3 RadiometerThe use of a radiometer to monitor andcontrol the amount of radiant energy received at the specimenis required. The use of the radiometer shall comp
14、ly with therequirements in Practice G151.1This practice is under the jurisdiction 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, 2016. Published July 2016. Originally ap
15、provedin 1988. Last previous edition approved in 2011 as D4798/D4798M 11. DOI:10.1520/D4798_D4798M-11R16.2For 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 standar
16、ds Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16. Test Specimens6.1 Unless otherwise agreed upon, test specimens shall beapproximately 70 by 150 mm 234 by 578 in. Bituminousmaterials with a
17、dequate flow resistance shall be applied asuniform coatings on aluminum panels in accordance withPractice D1669/D1669M. Fabricated materials such as bitumi-nous roofing, shingles, and similar products shall be cut to sizeand their weather surfaces exposed. Bituminous materials thatare too flexible t
18、o 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 otherwise specified, expose at least three rep-licate specimens of each test and control material.6.1.2 Other test specimen sizes
19、are permitted to be used toprovide sufficient material for postexposure testing whendesired.6.1.3 Follow the procedures described in Practice G147 foridentification, conditioning, and handling of specimens of testand control materials before, during, and after exposure.6.1.4 Do not mask the face of
20、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.7. Procedure7.1 Proceed in acco
21、rdance 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,organics, and particularly silica, exposed panels will developspots or stains that may not occur in exterior exposures.7.2.2
22、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 must bechecked to determine if it meets the requirements of 7.2.2.Onsome occasions, exposed specimens can be contaminated byde
23、posits 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 beflushed with chlorine and thoroughly rinsed before resumingexposures.7.2.4 The temperature of water used for specimen spray
24、shall 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 requirements de-scribed in 7.2.7.3 Unless o
25、therwise 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 described in Cycle A or Cycle B. Unless otherwisespecified, place specimens in an exposure area where irradi-ance is at least 90
26、 % 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 the conditions within the exposure area.NOTE 3Information about the exposure areas that meet the 90 %irradiance uniformity
27、 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 nm is 60.02W/(m2nm) and the maximum allowable deviation from thedesired uninsulated black panel temperature is 62.5C. During
28、equilibrium conditions, when the meter or sensor indicatingirradiance or black panel temperature shows a value that isoutside the limits described above, discontinue the test andcorrect the cause of the problem before continuing.7.3.1.1 Cycle A-151-min light-only exposure with deviceprogrammed to pr
29、oduce 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 specimens.7.3.1.2 Cycle A-2The same as Cycle A-1, except thatwater is sprayed on both the front and back surfaces of thespecim
30、ens.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 thespecimens, 990 min light-only exposure, 180 min of coldexposure. Program the device to produce an uninsulated blackpanel tem
31、perature 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 thespecimens.NOTE 4Typically water is sprayed only on the front surface of thespecimens. Some users operate their equipmen
32、t 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, panels shall be placed in afreezer that is controlled at 18C 0F. During equilibriumoperation, the maximum allowable deviatio
33、n 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 time used forinspection of the test specimens) shall not exceed 15 min. Thistime shall not be included as part of the 24 h e
34、xposure cycle.7.3.2 Some users use equipment capable of controllingchamber air temperature or relative humidity, or both. Whenchamber air temperature is controlled, program the device tocontrol chamber air temperature at 44C. For exposures inwhich relative humidity is controlled, it is recommended t
35、hatthe device be programmed to control at 50 % RH. Whenchamber air temperature or relative humidity, or both, arecontrolled, the setting of these parameters must be included inthe test report.7.3.2.1 When chamber air temperature is controlled, themaximum allowable deviation from the desired temperat
36、ure is62C. When the relative humidity is controlled, the maximumallowable deviation from the desired relative humidity duringequilibrium conditions is 610 % RH. During equilibriumconditions, when the meter or sensor indicating chamber airD4798/D4798M 11 (2016)2temperature or relative humidity indica
37、tes 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 runwithout controlling humidity or chamber air temperature. Tests run withhumidity or chamber air temperature c
38、ontrolled 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 following:8.1.1 A mutually agreed upon number of 24-h cycles ofoperation in accordance with either Cycle A or Cy
39、cle 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 agreed upon minimum acceptable changes in eitherthe test specimen or a mutually agreed upon control sample.8.2 C
40、hanges 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 produce property changes as determined byTest Method D1670/D1670M.NOTE 6When changes in properties of the tes
41、t 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 about the use of statistical analysis forresults from weathering exposures.9. Report9.1 In addition
42、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 paneltemperature, and, when controlled, relative humidity andchamber air temperature,9.1.3 Coating thickness use
43、d, 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. Precision and Bias10.1 PrecisionThe repeatability of results obtained inexposures conducted according to
44、this practice will vary withthe materials being tested, the material property beingmeasured, and the specific test conditions and cycles that areused. It is essential to determine reproducibility of theexposure/property measurement process when using the resultsfrom exposures conducted according to
45、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; exposure; light exposure; roofing; ultraviolet; waterproof-ing; xenon-ar
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