ASTM_G_7_-_G_7M_-_13.pdf

Designation:G7/G7M13Standard Practice forAtmospheric Environmental Exposure Testing ofNonmetallic Materials1This standard is issued under the fixed designation G7/G7M;the number immediately following the designation indicates 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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This practice covers procedures to be followed for directexposure of nonmetallic materials to the environment.Whenoriginators of a weathering test have the actual exposureconducted by a separate agency,the specific conditions for theexposure of test and control specimens must be clearly definedand mutually agreed upon between all parties.1.2 For exposures behind glass,refer to Practice G24.1.3 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;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 This practice is technically equivalent to the parts ofISO 877 that describe direct exposures of specimens to theenvironment.1.5 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-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E41 Terminology Relating To ConditioningE824 Test Method for Transfer of Calibration From Refer-ence to Field RadiometersE913 Method for Calibration of Reference PyranometersWith Axis Vertical by the Shading Method(Withdrawn2005)3E941 Test Method for Calibration of Reference Pyranom-eters WithAxis Tilted by the Shading Method(Withdrawn2005)3G24 Practice for Conducting Exposures to Daylight FilteredThrough GlassG113 Terminology Relating to Natural and Artificial Weath-ering Tests of Nonmetallic MaterialsG130 Test Method for Calibration of Narrow-and Broad-Band Ultraviolet Radiometers Using a Spectroradiometer2.2 ISO Standards:ISO 877 PlasticsMethods of Exposure to Direct Weath-ering;to Weathering Using Glass-Filtered Daylight,and toIntensified Weathering by Daylight Using Fresnel Mir-rors4ISO 9370 PlasticsInstrumental Determination of RadiantExposure in Weathering TestsGeneral Guidance andBasic Test Method42.3 ASTM Adjuncts:A Test Rack53.Terminology3.1 DefinitionsThe definitions given in Terminology E41and Terminology G113 are applicable to this practice.4.Significance and Use4.1 The relative durability of materials in natural exposurescan be very different depending on the location of the exposurebecause of differences in ultraviolet(UV)radiation,time ofwetness,temperature,pollutants,and other factors.Therefore,it cannot be assumed that results from one exposure in a singlelocation will be useful for determining relative durability in adifferent location.Exposures in several locations with different1This practice is under the jurisdiction ofASTM Committee G03 on Weatheringand Durabilityand is the direct responsibility of Subcommittee G03.02 on Naturaland Environmental Exposure Tests.Current edition approved June 1,2013.Published June 2013.Originallyapproved in 1969.Last previous edition approved in 2011 as G7/G7M 11.DOI:10.1520/G0007_G0007M-13.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.5Detailed drawings for an acceptable test rack may be obtained from ASTMInternational.Request ADJG0007.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 climates which represent a broad range of anticipated serviceconditions are recommended.4.2 Because of year-to-year climatological variations,re-sults from a single exposure test cannot be used to predict theabsolute rate at which a material degrades.Several years ofrepeat exposures are needed to get an“average”test result fora given location.4.3 Solar ultraviolet radiation varies considerably as afunction of time of year.This can cause large differences in theapparent rate of degradation in many polymers.Comparingresults for materials exposed for short periods(less than oneyear)is not recommended unless materials are exposed at thesame time in the same location.4.4 Defining exposure periods in terms of total solar orsolar-ultraviolet radiant energy c