1、Designation: D7869 13Standard Practice forXenon Arc Exposure Test with Enhanced Light and WaterExposure for Transportation Coatings1This standard is issued under the fixed designation D7869; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, 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 This practice specifies the operating procedures for acontrolled irradiance xenon arc light and wa
3、ter apparatus. Theprocedure uses one or more lamp(s) and optical filter(s) toproduce irradiance similar to sunlight in the UV and visiblerange. It also simulates the water absorption and stress cyclesexperienced by automotive exterior coatings under naturalweathering conditions. This practice has al
4、so been foundapplicable to coatings on other transportation vehicles, such asaircraft, trucks and rail cars.1.2 This practice uses a xenon arc light source with speci-fied optical filter(s). The spectral power distribution (SPD) forthe lamp and special daylight filter(s) is as specified in AnnexA1.
5、The irradiance level used in this practice varies between0.40 and 0.80 W/(m2nm) at 340 nm. Water is sprayed on thespecimens during portions of several dark steps. The applica-tion of water is such that the coatings will absorb and desorbsubstantial amounts of water during testing. In addition, thecy
6、cling between wet/dry and warm/cool will induce mechani-cal stresses into the materials. These test conditions aredesigned to simulate the physical and chemical stresses fromenvironments in a subtropical climate, such as southernFlorida.1.3 The values stated in SI units are to be regarded asstandard
7、. No other units of measurement are included in thisstandard.1.4 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-
8、bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4517 Test Method for Low-Level Total Silica in High-Purity Water by Flameless Atomic Absorption Spectros-copyG113 Terminology Relating to Natural and Artificial Weath-ering Tests of Nonmetallic MaterialsG147 Pr
9、actice for Conditioning and 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 M
10、aterials3. Terminology3.1 Definitions applicable to this standard can be found inTerminology G113.3.2 transportation coatings, nexterior coatings used forvehicles subjected to natural weathering conditions such asautomobiles, aircraft, trucks, rail cars, etc.4. Summary of Practice4.1 Test specimens
11、are exposed to specific test conditionsdesigned to simulate the physical and chemical stresses fromenvironments in a subtropical climate, such as southernFlorida. The test conditions consist of a primary test cycle anda sub-cycle. The primary test cycle includes two long waterexposures and a single,
12、 long light exposure with precisespectral match to daylight as described in Annex A1.Itisdesigned to reproduce water penetration failures, such asadhesion, blistering and diffusion of small molecules (1).3Thesub-cycle consisting of shorter alternating water and light1This practice is under the juris
13、diction of ASTM Committee on Paint andRelated Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.27 on Accelerated Testing.Current edition approved June 1, 2013. Published June 2013. DOI: 10.1520/D7869-13.2For referenced ASTM standards, visit the ASTM website,
14、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.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.Copyright ASTM Intern
15、ational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1exposures is designed to simulate cyclic stresses such ascracking and surface erosion. These two cycles are designed toreplicate the common types of failures driven by the interactionof photo-oxidation durin
16、g daylight and hydrolysis during waterexposure that are seen in a subtropical climate such as glossloss, color change, adhesion, blistering and cracking (2).5. Significance and Use5.1 This test procedure is used to simulate the physical andenvironmental stresses that a coating for exterior transport
17、ationapplications (for example, automotive) is exposed to in asubtropical climate, such as southern Florida. It has been foundthat such a subtropical climate causes particularly severedeterioration of such coatings. The long water exposures andwet/dry cycling found in southern Florida are particular
18、lyimportant for this deterioration, in addition to the high dosageof solar radiation (3). This practice was developed to addressthe deficiencies of historical tests used for transportationcoatings, especially automotive coatings (4).NOTE 1This test procedure was developed through eight years ofcoope
19、rative testing between automotive and aerospace OEMs, materialsuppliers, and test equipment manufacturers. See References for publishedpapers on this research.6. Apparatus6.1 The xenon arc light and water apparatus shall complywith Practice G155.6.1.1 The xenon arc light and water apparatus shall ha
20、ve anuninsulated black panel thermometer as described in PracticeG151 unless otherwise agreed upon by contractual parties6.1.2 The xenon arc light and water apparatus must be ableto control irradiance at 340 nm, relative humidity, uninsulatedblack panel temperature and chamber temperature, and provi
21、dewater spray on the front of the specimens.6.2 Mass balancewith a resolution of at least 0.1 g.7. Reagents and Materials7.1 Sponge. See Annex A2 for more detailed specifications.7.2 Purified Water, as specified in Practice G155 and 8.2.8. Apparatus Setup8.1 Maintain and calibrate the apparatus acco
22、rding to manu-facturers instructions.8.2 Water SprayThe water for spray and humidificationshall be of the same quality listed in Practice G155 and shallleave no objectionable deposits or stains on the exposedspecimens. The water shall have less than 1 mg per litre (1ppm) total dissolved solids and i
23、t shall have less than 0.1 mgper litre (0.1 ppm) silica.NOTE 2Silica levels should be determined using Test Method D4517or equivalent. A combination of deionization and reverse osmosis treat-ment can effectively produce water with the desired purity. In certain casessome samples could exude material
24、s into the chamber that can promotedeleterious effects on other samples.8.3 Qualify the sponges used for the water uptake per theprocedure in Annex A2. For each xenon arc light and waterapparatus, verify the water uptake capability in accordancewith the procedure in Annex A3 before placing it into s
25、erviceand at least once per year thereafter. Follow the recommenda-tions of the manufacturer of the xenon arc light and waterapparatus for additional checks, if any.8.4 Fit the xenon arc light and water apparatus with aspecial daylight filter(s) in accordance with the requirements ofAnnex A1.NOTE 3C
26、ontact the xenon arc light and water apparatus manufacturerfor the proper optical filter(s) required. Follow the manufacturersrecommendations for optical filter maintenance.8.5 Other optical filters may be used by mutual agreementbetween the contractual parties.NOTE 4Minor differences in the resulta
27、nt spectral power distribution(especially in the short wavelength UV region) can have an impact on thetest results. Follow the manufacturers recommendations for xenon arclamp and optical filter maintenance (5).9. Test Procedure9.1 Refer to Practice G147 for specimen preparation, con-ditioning and ha
28、ndling. All test specimens must be clean andfree from fingerprints or other surface contaminants beforetesting. Prepare a specimen for exposure to fit the specimenmounting fixture being used, if any. Follow the manufacturersguidelines for specimen size and mounting.9.1.1 Seal any cut edges on the te
29、st specimens if required, asagreed between contractual parties. For example, (a) rust andcorrosion products from the cut edges of metal panels maystain the test specimens, (b) by-products from the cut edges ofplastic substrates may leach out and contaminate testspecimens, and (c) other panels may no
30、t require any edgesealing at all.NOTE 5Air-dry primers, plastic barrier tapes and silicone sealantshave often been found suitable for edge sealing.9.2 Fill all unused specimen positions in the xenon arc lightand water apparatus exposure area with inert specimens (forexample, anodized aluminum panels
31、) to maintain desiredairflow.NOTE 6Refer to the manufacturers instructions for proper operationof the apparatus.9.3 Program the xenon arc light and water apparatus to runthe exposure cycle shown in Table 1 and in accordance withmanufacturers instructions. The duration of the test in terms ofnumber o
32、f cycles, hours, or radiant dosage shall be agreed uponby contractual parties.9.4 Specimens shall be repositioned at a minimum of everytwo weeks of operation to improve uniformity of exposure. SeePractice G151, Appendix X2 for more specific guidance andfigures on repositioning of specimens in both r
33、otating rack andflat array xenon arc light and water apparatus.9.4.1 Specimens in a rotating rack apparatus shall be repo-sitioned to the position immediately above it; specimens in thetop position shall be repositioned to the bottom position.9.4.2 Specimens in a flat array apparatus shall be reposi
34、-tioned to the position immediately to the left; specimens in theleft-most position shall be repositioned to the right-mostposition, with front-back and back-front repositioning if appli-cable.D7869 132NOTE 7Specimen repositioning in 9.4.1 and 9.4.2 is required tocompensate for variations in light,
35、water, relative humidity and tempera-ture within the test chamber.9.5 The test shall be interrupted for repositioning andspecimen evaluations only during a step without water spray.10. Report10.1 The test report shall conform to Practice G151. Thereport shall also include the average of three water
36、collectionmeasurements for each position in the xenon arc light andwater apparatus, in accordance with Annex A3.11. Keywords11.1 accelerated; automotive; coatings; durability; exposuretest; irradiance; lightfastness; weathering; xenon arcANNEXESA1. DAYLIGHT FILTER IRRADIANCE LIMITS BY WAVELENGTH(Man
37、datory Information for Equipment Manufacturers)A1.1 Conformance to the spectral power distribution inTable A1.1 is a design parameter for a xenon-arc source withthe different optical filters provided. Manufacturers of equip-ment claiming conformance to this standard shall be respon-sible for determi
38、ning conformance to the spectral powerdistribution table for all lamp/filter combinations provided, andprovide information on maintenance procedures to minimizeany spectral changes that may occur during normal use.TABLE 1 Exposure CycleStep Number Step Minutes FunctionIrradiance SetPointAat 340 nmW/
39、(m2nm)Black PanelTemperatureSet PointAChamber AirTemperatureSet PointARelative HumiditySet PointA1 240 dark + spray 40C 95 %2 30 light 0.40 50C 42C 50 %3 270 light 0.80 70C 50C 50 %4 30 light 0.40 50C 42C 50 %5 150 dark + spray 40C 95 %6 30 dark + spray 40C 95 %7 20 light 0.40 50C 42C 50 %8 120 ligh
40、t 0.80 70C 50C 50 %9 10 dark 40C 50 %10 Repeat subcycle steps 6 to 9 (shown in bold) an additional 3 times (for a total or 24h=1cycle).AThe set point is the target condition for the sensor used at the operational control point and is programmed by the user. When the exposure cycle calls for a partic
41、ularset point, the user programs the apparatus to use that exact number. Operational fluctuations are deviations from the indicated set point during equilibrium operation. Themaximum allowable operational fluctuation during equilibrium conditions for the exposure cycle above is 0.02 W/(m2nm) for irr
42、adiance, 2.5C for black paneltemperature, 2C for chamber air temperature, and 10 % for relative humidity.Wavelength BandTotal Irradiance Over IndicatedWavelength Band(W/m2)(nm) Minimum Maximum 290 0.00 0.005290 # 295 0.00 0.01295 # 300 0.01 0.04300 # 305 0.10 0.20305 # 310 0.38 0.56310 # 320 2.29 3.
43、10320 # 330 4.76 5.82330 # 340 6.84 7.56340 # 350 7.69 9.40350 # 360 8.13 11.00360 # 370 8.32 12.47370 # 380 8.30 13.83380# 390 8.64 14.40390# 400 9.23 17.15Note: Irradiance in W/m2normalized to 0.80 W/(m2nm) at 340 nm.D7869 133A2. SPONGE QUALIFICATION PROCEDURE(Mandatory Information)A2.1 Cut a sect
44、ion of the homogeneous sponge material toa maximum size of 57 mm wide, 127 mm long and 19 mmthick. Both sides of the sponge shall have the same waterabsorbance capability. Do not use multi-layer sponges.A2.2 Weigh a damp sponge.A2.2.1 Thoroughly saturate the cut sponge with water bysoaking it in at
45、least 2 L of water at room temperature (23 63C) for a minimum of 1 min. or until it has reached fullsaturation. Different types of sponges will take different timesto reach full saturation.A2.2.2 Remove as much water as possible from the spongethrough wringing by hand as shown in Fig. A2.1. Weigh it
46、 tothe nearest 0.1 g on a calibrated balance capable of at least100.0 g total weight. The preferred type of sponge for this testmethod will weigh between 20.0 and 30.0 g after removingexcess water.A2.2.3 Tare the balance to zero and remove the dampsponge from the balance. Subsequent weighing of the
47、spongewill thus record only the additional water absorbed into thesponge.A2.3 Weigh a saturated sponge.A2.3.1 Saturate the sponge again in a minimum 2 L of roomtemperature water by keeping the sponge totally immersed fora minimum of 1 min.A2.3.2 After a minimum of 1 min., remove the sponge fromthe w
48、ater and lightly hold it vertically over the water containeras shown in Fig.A2.2. Continue holding it until the sponge hasat most, one water drop per 15 s coming from the bottom of thesponge.A2.3.3 Turn the sponge horizontally as shown in Fig. A2.3to prevent any more water loss and place it on the t
49、aredbalance. This will show the additional mass of water absorbedbeyond the mass of just the damp sponge. Record the mass.A2.3.4 Repeat steps A2.3.1-A2.3.3 two additional times anddetermine an average mass of water held by the sponge for thethree runs. This will define the saturation capacity of thesponge (mass of saturated sponge minus mass of dampsponge).A2.4 Acceptance criteria for the saturation capacity of thesponge is as follows:Minimum: 40.0 gramsPreferred: 50.0 gramsMaximum: no maximumA2.5
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