1、Designation: D7897 15D7897 18Standard Practice forLaboratory Soiling and Weathering of Roofing Materials toSimulate Effects of Natural Exposure on Solar Reflectanceand Thermal Emittance1This standard is issued under the fixed designation D7897; the number immediately following the designation indica
2、tes the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 Practice D7897 applies to simulation of the
3、effects of field exposure on the solar reflectance and thermal emittance of roofsurface materials including but not limited to field-applied coatings, factory-applied coatings, single-ply membranes, modifiedbitumen products, shingles, tiles, and metal products. The solar reflectance and thermal emit
4、tance of roof surfacesurfacingmaterials can be changed by exposure to the outdoor environment. These changes are caused by three factors: deposition andretention of airborne pollutants; microbiological growth; and changes in physical or chemical properties. This practice applies tosimulation of chan
5、ges in solar reflectance and thermal emittance induced by deposition and retention of airborne pollutants and,to a limited extent, changes caused by microbiological growth.1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibil
6、ityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.3 This international standard was developed in accordance with internationally recognized principles on standardiz
7、ationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2C1371 Test Method for Determination of Emittance of M
8、aterials Near Room Temperature Using Portable EmissometersC1549 Test Method for Determination of Solar Reflectance Near Ambient Temperature Using a Portable Solar ReflectometerE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodG151 Practice for Exposing
9、Nonmetallic Materials in Accelerated Test Devices that Use Laboratory Light SourcesG154 Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Nonmetallic Materials2.2 Other Standards:ANSI/CRRC S100 Standard Test Methods for Determining Radiative Properties of Materials33
10、. Terminology3.1 Definitions:3.1.1 solar energythe radiant energy originating from the sun.3.1.1.1 DiscussionApproximately 99 % of terrestrial solar radiation lies between the wavelengths of 0.3 and 2.5 m, with peak radiation near 0.5 m.This spectrum includes ultraviolet, visible, and near-infrared
11、radiation.3.1.2 solar reflectancethe fraction of incident solar flux reflected by a surface.1 This practice is under the jurisdiction of ASTM Committee D08 on Roofing and Waterproofing and is the direct responsibility of Subcommittee D08.20 on RoofingMembrane Systems.Current edition approved Jan. 1,
12、 2015March 15, 2018. Published March 2015July 2018. Originally approved in 2015. Last previous edition approved in 2015 asD7897 15. DOI: 10.1520/D7897-15.10.1520/D7897-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annu
13、al Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intended only to
14、 provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof
15、 the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.3 thermal emittanceefficiency with which a surface emits thermal radiation, measured on a scale from 0 to
16、 1, where avalue of 1 indicates perfect emission (that is, equal to that of a black body).3.1.4 thermal radiationthe radiant energy originating from a 300 K (about 27C) black body.3.1.4.1 DiscussionApproximately 99 % of thermal radiation lies between the wavelengths of 4 and 80 m, with peak radiatio
17、n near 10 m.4. Summary of Practice4.1 This practice presents a rapid laboratory method for weathering and soiling, which simulates natural changes in solarreflectance and thermal emittance of materials in the field. The practice describes a simulated field exposure protocol that consistsof spraying
18、an aqueous suspensionmixture of soot and other soluble soiling constituents, including salts and organic matter, ontoa specimen of roof surfacing materials.material. The specimen is exposed in a weathering apparatus before soiling, to provide UVconditioning; and after soiling, to simulate the cleani
19、ng effect of moisture (1).45. Significance and Use5.1 The solar reflectance of a building envelope surface affects surface temperature and near-surface ambient air temperature.Surfaces with low solar reflectance absorb a high fraction of the incoming solar energy. Sunlight absorbed by a roof or by o
20、therbuilding envelope surfaces can be conducted into the building, increasing cooling load and decreasing heating load in a conditionedbuilding, or raising indoor temperature in an unconditioned building. It can also warm the outside air by convection. Determinationof solar reflectance can help desi
21、gners and consumers choose appropriate materials for their buildings and communities.5.1.1 The solar reflectance of a new building envelope surface often changes within one to two years through deposition andretention of soot and dust; microbiological growth; exposure to sunlight, precipitation, and
22、 dew; and other processes of soiling andweathering. For example, light-colored “cool” envelope surfaces with high initial reflectance can experience substantial reflectanceloss as they are covered with dark soiling agents. Current product rating programs require roofing manufacturers to report value
23、sof solar reflectance and thermal emittance measured after three years of natural exposure (2, 3). A rapid laboratory process forsoiling and weathering that simulates the three-year-aged radiative properties of roof and other building envelope surface materialsexpedites the development, testing, and
24、 introduction to market of such products.5.2 Thermal emittance describes the efficiency with which a surface exchanges thermal radiation with its environment. Highthermal emittance enhances the ability of a surface to stay cool in the sun. The thermal emittance of a bare metal surface is initiallylo
25、w, and often increases as it is soiled or oxidized (4). The thermal emittance of a typical non-metal surface is initially high, andremains high after soiling (5).5.3 This practice allows measurement of the solar reflectance and thermal emittance of a roofing specimen after the applicationof the simu
26、lated field exposure.5.4 This practice is intended to be referenced by another standard, such as ANSI/CRRC S100, that specifies practices forspecimen selection and methods for radiative measurement.6. Standard Practice Method and Apparatus6.1 Soiling AgentsAtmospheric particles originate from windbl
27、own dust, forest and grassland fires, living vegetation, and seaspray, as well as from human activities, such as the burning of fossil and biomass fuels. Most particles either scatter or weaklyabsorb sunlight. A notable exception is black carbon soot emitted from the burning of fossil and biomass fu
28、els and from fires.Because of its strong mass absorption efficiency, small amounts of black soot appreciably contribute to the soiling of buildingsurfaces. An aqueous mixture of four soiling agents (as described below) is used for the simulated field exposure. The soilingagents and their concentrati
29、ons were chosen based on their respective contributions to changes in the solar reflectance spectra ofsoiled surfaces, as determined in the laboratory. These four soiling agents have been shown to accumulate on surfaces exposed innatural outdoor settings (6).6.1.1 SootA commercially available self-d
30、ispersible carbon black (Aqua-Black 001: Tokai Carbon Co., Ltd5), is used assurrogate for soot. 1.37 6 0.05 g of Aqua-Black 001 aqueous dispersion (19 % m/m carbon black) is diluted into 1 L of distilledwater and shaken for three to five minutes to produce a stable soot (carbon black) suspension of
31、0.26 6 0.01 g/L.6.1.1 DustA mixture of iron oxide (Fe2O3) powder (color: red-brown, particle size 5 m, purity 99 %, CAS: 1309-37-1;example: SKU 310050 Sigma Aldrich) and two natural clays (1) montmorillonite K10 powder (color: yellowish-gray, surface4 The boldface numbers in parentheses refer to a l
32、ist of references at the end of this standard.D7897 182area: 220 to 270 m2/g, CAS: 1318-93-0; example: SKU 281522 Sigma Aldrich) and (2) nanoclay, hydrophilic bentonite (particlesize 25 m, CAS: 1302-78-9; example: SKU 682659 Sigma Aldrich) is used as a surrogate for dust. (Similar chemicals can bepr
33、ocured from other vendors.)6.1.1.1 A mass of 0.3 6 0.02 g of Fe2O3 powder is mixed with 1.0 6 0.05 g of montmorillonite and 1.0 6 0.05 g of bentonite.The mixture is transferred into 1 L of distilled water and stirred for about 1 h to prepare a stable dust suspension of 2.3 6 0.1 g/L.To prevent sedim
34、entation, the suspension is stirred again before use if more than 1 h has elapsed since it was originallypreviouslystirred.6.1.2 SaltsAsolution containing a mixture of inorganic salts is prepared by dissolving 0.3 6 0.03 g of sodium chloride (NaCl,CAS: 7647-14-5), 0.3 6 0.03 g of sodium nitrate (NaN
35、O3, CAS: 7632-00-0)7631-99-4) and 0.4 6 0.03 g of calcium sulfatedihydrate (CaSO42H2H2O, CAS: 7778-18-9)10101-41-4) into 1 L of distilled water. The solution is stirred to ensure that all saltsare dissolved. The total salt concentration of the solution is 1.0 6 0.1 g/L.6.1.3 Particulate Organic Matt
36、er (POM)1.4 6 0.05 g of humic acid (CAS: 1415-93-6) is dissolved in 1 L of distilled waterto produce a solution of 1.4 6 0.05 g/L.6.1.4 SootA commercially available self-dispersible carbon black (Aqua-Black 001: Tokai Carbon Co., Ltd5), is used assurrogate for soot. 1.37 6 0.05 g (equivalent volume:
37、 1.25 6 0.05 mL) of Aqua-Black 001 aqueous dispersion (19 % m/m carbonblack) is diluted into 1 L of distilled water and shaken for three to five minutes to produce a stable soot (carbon black) suspensionof 0.26 6 0.01 g/L.6.1.5 Composition of Soiling MixtureA separate solution or suspension is prepa
38、red for each soiling agent. Once prepared, thefour soiling solutions/suspensions described above are combined in various ratios depending upon the climate to be simulated.Each soiling mixture below has the same total mass concentration of soiling agents.6.1.5.1 Composition of soiling mixture for ave
39、rage U.S. conditions (average of three exposure sites: Phoenix, Arizona; Miami,Florida; andYoungstown, Ohio)Soiling agent mass is 47 % dust, 20 % salts, 28 % POM, and 5 % soot. This yields 0.58 g/Ldust,0.25 g/L salts, 0.35 g/L POM, and 0.065 g/L soot in the soiling mixture. Note that this soiling mi
40、xture is prepared by combiningequal volumes of the dust suspension, salt solution, POM solution, and soot suspension defined in 6.1.1 through 6.1.4.6.1.5.2 Composition of soiling mixture for hot and dry climates (Phoenix, Arizona)Soiling agent mass is 79 % dust, 20 %salts, 0 % POM, and 1 % soot. Thi
41、s yields 0.98 g/L dust, 0.25 g/L salts, 0 g/L POM, and 0.012 g/L soot in the soiling mixture.6.1.5.3 Composition of soiling mixture for hot and humid climates (Miami, Florida)Soiling agent mass is 16 % dust, 7 %salts, 69 % POM, and 8 % soot. This yields 0.20 g/L dust, 0.087 g/L salts, 0.85 g/L POM,
42、and 0.10 g/L soot in the soiling mixture.6.1.5.4 Composition of soiling mixture for moderate summer and cold winter climates (Youngstown, Ohio)Soiling agentmass is 61 % dust, 31 % salts, 0 % POM, and 8 % soot. This yields 0.75 g/L dust, 0.38 g/L salts, 0 g/L POM, and 0.10 g/L sootin the soiling mixt
43、ure.6.2 Soiling ApparatusThe soiling mixture is placed in an air-pressurized spraying tank, equipped with an air pressure gauge.The tank is connected with tubing to a brass spraying nozzle that includes a strainer to minimize clogging. The nozzle (example:UniJet Fogger Nozzle Assembly, model 1/4TT+S
44、F-2, Spraying Systems Co.) produces a wide-angle (approximately 100 to 110),hollow-cone fine spray with a delivery rate of 3.5 litres per hour at 138 kPa 20 psi gauge pressure. The nozzle is orientedvertically to spray downward.6.3 Weathering ApparatusAlaboratory accelerated weathering device is use
45、d to simulate outdoor weathering. The weatheringdevice exposes materials to alternating cycles of ultraviolet (UV) light and moisture at controlled, elevated temperatures. It usesfluorescent UVA-340 lamps to simulate the high energy photons in sunlight. Moisture is introduced with condensing humidit
46、y orwater spray, or both (Practices G151 and G154).7. Test Specimens7.1 The standard practice described here applies to roofing specimens that are flat (planar).8. Calibration of Soiling8.1 Calibration of the soiling procedure consists of verifying the wet soiling mass retained by a reference roofin
47、g productspecimen and the uniformity of the soiling pattern on the specimens surface. The reference specimen should have a light-colored,non-porous, non-fluorinated polymeric surface to facilitate inspection and validation of the soiling pattern, and to minimizevariations in retention of wet soiling
48、 mass. Recommended reference specimens include white single-ply membranes and whitefield-applied elastomeric coatings. The soiling apparatus shall be calibrated immediately prior to use, and re-calibrated every twohours while in use.8.2 The soiling mixture is agitated for 1 to 2 minutes to re-suspen
49、d any settled particles, then placed into the spraying vessel.8.2.1 The soiling mixture shall be re-agitated hourly every 30 minutes if the calibration process takes more than 1 hour. Tore-agitate, remove the soiling mixture from the spraying vessel, then repeat 30 minutes.8.2.5 The sole source of supply of the material known to the committee at this time is Tokai Carbon Co., Ltd. If you are aware of alternative suppliers, please provide thisinformation to ASTM International Headquarters. Your comments will receive careful consideration at a me
