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:1004-7204(2002)01-0009-08LABORATORYWEATHERINGDEVICESRudyLeber(ATLAS):,,:;;:V1:AAbstract:Thehistory,structureandcharacteristicoffourlightresourcesmostlyusedinlaboratoryweatheringhasbeendescribed.Atthesametimetheirlimitationarediscussed.,,,,,,:2001-07-31:RudyLeber,,ATLASDuetotheneedformorerapidevaluationsoftheresistanceofmaterialstoweatheringthancanbeobtainedbyoutdoorexposuretestsandtheneedforcontrolledconditions,testdeviceswithartificiallightsourcesaregenerallyusedtoacceleratethedegrada2tion.Thesedevicesincludecarbonarcandfilteredlongarcxenon,metalhalideandfluorescentUVlampapparatus.Theselaboratoryacceleratedweatheringdevicetestsaresometimes,andperhapsmoreappro2priately,referredtoasartificialweathering.Theaccelerationoverrealtimeweatheringoc2cursforseveralreasons.Principally,thetestscanruncontinuouslyatnaturallyoccurringorhigherirra2diancethansolarradiation,uninterruptedbythedi2urnalcycle,seasonalvariationsandweathercondi2tions.Temperatures,thermalcycles,humidityandwaterexposurecanalsobemanipulatedtomaximumbutnotunrealisticstresslevels.Specimenscanbeexposedtospectralenergiesatorbeyondthelimitsoftheirintendedserviceexposures,althoughcautionmustbeexercisedsoasnottoinduceunnaturaldegradationmechanisms.920021©1994-2006ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.(ECA),,,,;PyrexTM,,1930,CorexRWeather-OmeterR,Inadditiontotheabilitytomanipulateandac2celerateweatheringconditionsondemand,afunda2mentalbenefitofalaboratorytestistheprecisionandrepeatabilityoverwhatisessentiallyanuncontrolledandvariablephenomena,theactualweather.Plus,eachoftheweatheringfactorscanbemanipulatedin2dependently;thusresearchcanbeconductedintothespecificresponseofmaterialstovariousweatheringfactors,experimentswhichwouldbedifficultorim2possibletoconductoutdoors.Artificialweatheringdevicesareoftencatego2rizedbythetypeofartificiallightsourceused.Themostcommontypesarecarbonarc,fluorescentUV,xenon-arc,andmetalhalidelightsources.Eachhasitsowninherentbenefits(andpitfalls)ofwhichaweatheringexperimentermustbeaware.Sincetheradiantenergyreceivedbyanexposedmaterialisconsideredthemostimportant,wewillfocusourat2tentiononthequalityofthelightsource,referringtohowwelleachlightsourceresemblesnaturalsun2light.CarbonArcSourcesThecarbonarcinstrumentwasfirstusedbyGermansyntheticdyechemiststoevaluatethelight2fastnessofdyedtextiles.ThefirstAtlasColorFade-OmeterR,introducedin1919,usedanenclosedcarbonarc(ECA)lightsource.ItsdevelopmentwasaresultofaredesignofanearlierAtlasunit,theSo2larDeterminator.ThisearlierdevelopmentitselfwasanoutgrowthofAtlasSolar-Lightcarbon-arcstagelighting,AtlasmainbusinessduringthedayswhenChicagowasthemotionpicturecapitaloftheworld.Itbecameapparenttotheusersofthisstagelightingthatcertaintextilematerialsandgarmentswornbytheactorswouldfadeafterextendedlengthsoftime.Today,enclosedcarbonarcsareavailableinsingleandtwinarcversions;thearcisenclosedinaPyrexTMglobetoprovidesomeopticalfilteringandanoxygen-deficientatmosphere.Theintroductioninthe1930softheopenflamecarbonarc,intheAtlasSunshineCarbonArcWeather-OmeterRwithCorexRfilters,providesmoreUV300nmthansunlightbutgivesamuchbettermatchinthe300-340nmregionanddeviateslessthantheenclosedcar2bonarcatlongerwavelengths.Whenusedwithout0120021©1994-2006ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.(,),,,,,,,:ISO4892---:,ASTMG152,G153,filtersforfastertesting,stabilityrankingsofsomematerialsmaybedistortedwhencomparedwithout2doortesting.TheSunshinearcusesthreepairsofcoredcarbonrodsandoperatesinafreeflowofair;thearcisrotatedamongthepairstoprovideapproxi2matelyadaysoperationpersetandthearcisusual2lyfilteredbyflatCorexfiltersarrayedaroundthearc.ThespectralemissionintheUVbearslittlere2semblancetodaylight.Twostrongemissionbands,peakingat358nmand386nmareabout4and20timesdaylightrespectively.Thistypeoflightsourcecanbeexpectedtohaveaweakereffectthansolarra2diationonmaterialsthatabsorbonlyshortwavelengthUVradiation,butastrongereffectonmaterialsthatalsoabsorblongwavelengthUVandvisiblelight.Therefore,intryingtoevaluatetherelativelightsta2bilitiesofmaterials,someofwhichabsorbonlyshortwavelengthUVandothersthatalsoabsorblongwave2lengthUV,theenclosedcarbonarccoulddistorttherankingswhencomparedwithsamplesexposedtoso2larradiation.Bothcarbonarctechnologiesrequiredailyre2placementofthecarbonrodsandcleaningofthefil2tersorglobes.Filtersandglobesdegradeandmustbeperiodicallyreplaced;accumulatedcarbonsootmustalsoberemoved.Thereisavastamountofhistoricaldatausingcarbonarcs,andanumberoftestmethodsstillspecifytheiruse.Whilegoodcorrelationwithoutdoorexposureshasbeenreportedforsomemateri2alswhoseweatheringmechanismsareappropriatefortheselimitedspectrumsources,thistechnologyhaslargelybeenreplacedwithxenonarcinstruments.Theprimarydocumentsdescribingperformancechar2acteristicsofdevicesthatusethecarbonarclightsourceare:ISO4892-Plastics-MethodsOfEx2posureToLaboratoryLightSources-Part4:Open-FlameCa