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Designation G151 − 19Standard Practice forExposing Nonmetallic Materials in Accelerated Test Devicesthat Use Laboratory Light Sources1This standard is issued under the fixed designation G151; 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.1. Scope1.1 This practice covers general procedures to be used whenexposing nonmetallic materials in accelerated test devices thatuse laboratory light sources. Detailed information regardingprocedures to be used for specific devices are found instandards describing the particular device being used. Forexample, detailed information covering exposures in devicesthat use open flame carbon arc, enclosed carbon arc, xenon arc,and fluorescent UV light source are found in Practices G152,G153, G154, and G155 respectively.NOTE 1Carbon-arc, xenon arc, and fluorescent UV exposures werealso described in Practices G23, G26, and G53 which referred to veryspecific equipment designs. Practices G152, G153, and G154, and G155are performance based standards that replace Practices G23, G26, andG53.1.2 This practice also describes general performance re-quirements for devices used for exposing nonmetallic materialsto laboratory light sources. This information is intendedprimarily for producers of laboratory accelerated exposuredevices.1.3 This practice provides information on the use andinterpretation of data from accelerated exposure tests. Specificinformation about methods for determining the property of anonmetallic material before and after exposure are found instandards describing the method used to measure each prop-erty. Information regarding the reporting of results fromexposure testing of plastic materials is described in PracticeD5870.NOTE 2Guide G141 provides information for addressing variability inexposure testing of nonmetallic materials. Guide G169 provides informa-tion for application of statistics to exposure test results.NOTE 3This standard is technically equivalent to ISO 4892, Part 1.1.4 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, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade TBT Committee.2. Referenced Documents2.1 ASTM Standards2D618 Practice for Conditioning Plastics for TestingD3924 Specification for Standard Environment for Condi-tioning and Testing Paint, Varnish, Lacquer, and RelatedMaterials Withdrawn 20163D5870 Practice for Calculating Property Retention Index ofPlasticsE41 Terminology Relating to Conditioning Withdrawn20193E171 Practice for Conditioning and Testing Flexible BarrierPackagingE644 Test Methods for Testing Industrial Resistance Ther-mometersE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE772 Terminology of Solar Energy ConversionE839 Test Methods for Sheathed Thermocouples andSheathed Thermocouple CableG23 Practice for Operating Light-Exposure ApparatusCarbon-Arc Type With and Without Water for Exposureof Nonmetallic Materials Withdrawn 20003G26 Practice for Operating Light-Exposure ApparatusXenon-Arc Type With and Without Water for Exposureof Nonmetallic Materials Discontinued 2001 With-drawn 200031This practice is under the jurisdiction of ASTM Committee G03 on Weatheringand Durability and is the direct responsibility of Subcommittee G03.03 onSimulated and Controlled Exposure Tests.Current edition approved Jan. 1, 2019. Published February 2019. Originallyapproved in 1997. Last previous edition approved in 2010 as G151 – 10. DOI10.1520/G0151-19.2For 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 standard’s Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade TBT Committee.1G53 Practice for Operating Light-and Water-Exposure Ap-paratus Fluorescent UV-Condensation Type for Expo-sure of Nonmetallic Materials Withdrawn 20003G113 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 SpectroradiometerG141 Guide for Addressing Variability in Exposure Testingof Nonmetallic MaterialsG147 Practice for Conditioning and Handling of Nonmetal-lic Materials for Natural and Artificial Weathering TestsG152 Practice for Operating Open Flame Carbon Arc LightApparatus for Exposure of Nonmetallic MaterialsG153 Practice for Operating Enclosed Carbon Arc LightApparatus for Exposure of Nonmetallic MaterialsG154 Practice for Operating Fluorescent Ultraviolet UVLamp Apparatus for Exposure of Nonmetallic MaterialsG155 Practice for Operating Xenon Arc Light Apparatus forExposure of Non-Metallic MaterialsG156 Practice for Selecting and Characterizing WeatheringReference MaterialsG169 Guide for Application of Basic Statistical Methods toWeathering TestsG177 Tables for Reference Solar Ultraviolet Spectral Distri-butions Hemispherical on 37° Tilted Surface2.2 ISO Standards4ISO 4892, Part 1 Plastics Exposure to laboratory LightSourcesGeneral GuidanceISO 9370 Plastics Instrumental Determination of RadiantExposure in Weathering TestsGeneral Guidance andBasic Test Method2.3 CIE Document5CIE Publication Number 85 1989 Technical ReportSolarSpectral Irradiance2.4 Other DocumentsIES LM-58-13 Spectroradiometric Measurement Methodsfor Light Sources 2013 or Later6NIST SP250-89 Spectral Irradiance Calibrations72.5 ASTM Adjuncts8SMARTS2, Simple Model forAtmospheric Transmission ofSunshine3. Terminology3.1 DefinitionsThe definitions given in TerminologiesE41, E772, and G113 are applicable to this practice.4. Significance and Use4.1 Significance4.1.1 When conducting exposures in devices that use labo-ratory light sources, it is important to consider how well theaccelerated test conditions will reproduce property changes andfailure modes associated with end-use environments for thematerials being tested. In addition, it is essential to consider theeffects of variability in both the accelerated test and outdoorexposures when setting up exposure experiments and wheninterpreting the results from accelerated exposure tests.4.1.2 No laboratory exposure test can be specified as a totalsimulation of actual use conditions in outdoor environments.Results obtained from these laboratory accelerated exposurescan be considered as representative of actual use exposuresonly when the degree of rank correlation has been establishedfor the specific materials being tested and when the type ofdegradation is the same. The relative durability of materials inactual use conditions can be very different in different locationsbecause of differences in UV radiation, time of wetness,relative humidity, temperature, pollutants, and other factors.Therefore, even if results from a specific exposure test con-ducted according to this practice are found to be useful forcomparing the relative durability of materials exposed in aparticular exterior environment, it cannot be assumed that theywill be useful for determining relative durability of the samematerials for a different environment.4.1.3 Even though it is very tempting, calculation of anacceleration factor relating x h or megajoules of radiantexposure in a laboratory accelerated test to y months or yearsof exterior exposure is not recommended. These accelerationfactors are not valid for several reasons.4.1.3.1 Acceleration factors are material dependent and canbe significantly different for each material and for differentformulations of the same material.4.1.3.2 Variability in the rate of degradation in both actualuse and laboratory accelerated exposure test can have asignificant effect on the calculated acceleration factor.4.1.3.3 Acceleration factors calculated based on the ratio ofirradiance between a laboratory light source and solarradiation, even when identical bandpasses are used, do not takeinto consideration the effects on a material of irradiance,temperature, moisture, and differences in spectral power dis-tribution between the laboratory light source and solar radia-tion.NOTE 4If use of an acceleration factor is desired in spite of thewarnings given in this practice, such acceleration factors for a particularmaterial are only valid if they are based on data from a sufficient numberof separate exterior and laboratory accelerated exposures so that resultsused to relate times to failure in each exposure can be analyzed usingstatistical methods. An example of a statistical analysis using multiplelaboratory and exterior exposures to calculate an acceleration factor isdescribed by J. A. Simms 1.94.1.4 There are a number of factors that may decrease thedegree of correlation between accelerated tests using labora-tory light sources and exterior exposures. More specific infor-mation on how each factor may alter stability ranking ofmaterials is given in Appendix X1.4Available from American National Standards Institute ANSI, 25 W. 43rd St.,4th Floor, New York, NY 10036, http//www.ansi.org.5Available from the Commission Internationale de L’Eclairage, CIE, CentralBureau, Kegelgasse 27, A-1030 Vienna, Austria or the U.S. National Committee forCIE, National Institute for Science and Technology, Gaithersburg, MD.6Available from Illuminating Engineering Society of North America IESNA,120 Wall Street, New York, NY 10005, https//www.ies.org/.7Available from National Institute of Standards and Technology NIST, 100Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http//www.nist.gov.8Available from ASTM International Headquarters. Order Adjunct No.ADJG173CD. Original adjunct produced in 2005.9The boldface numbers in parentheses refer to the list of references at the end ofthis standard.G151 − 1924.1.4.1 Differences in the spectral distribution between thelaboratory light source and solar radiation.4.1.4.2 Light intensities higher than those experienced inactual use conditions.4.1.4.3 Test conditions where specimens are exposed con-tinuously to light when actual use conditions provide alternateperiods of light and dark.4.1.4.4 Specimen temperatures higher than those in actualconditions.4.1.4.5 Exposure conditions that produce unrealistic tem-perature differences between light and dark colored specimens.4.1.4.6 Exposure conditions that do not have any tempera-ture cycling or that produce temperature cycling, or thermalshock, or both, that is not representative of use conditions.4.1.4.7 Unrealistically high or low levels of moisture.4.1.4.8 Absence of biological agents or pollutants.4.2 Use of Accelerated Tests with Laboratory Light Sources4.2.1 Results from accelerated exposure tests conductedaccording to this standard are best used to compare the relativeperformance of materials. A common application is conductinga test to establish that the level of quality of different batchesdoes not vary from a control material with known performance.Comparisons between materials are best made when they aretested at the same time in the same exposure device. Resultscan be expressed by comparing the exposure time or radiantexposure necessary to change a characteristic property to somespecified level.4.2.1.1 Reproducibility of test results between laboratorieshas been shown to be good when the stability of materials isevaluated in terms of performance ranking compared to othermaterials or to a control 2, 3; therefore, exposure of a similarmaterial of known performance a control at the same time asthe test materials is strongly recommended.4.2.2 In some applications, weathering reference materialsare used to establish consistency of the operating conditions inan exposure test.4.2.3 Reference materials, for example, blue wool testfabric, also may be used for the purpose of timing exposures.In some cases, a reference material is exposed at the same timeas a test material and the exposure is conducted until there is adefined change in property of the reference material. The testmaterial then is evaluated. In some cases, the results for the testmaterial are compared to those for the reference material.These are inappropriate uses of reference materials when theyare not sensitive to exposure stresses that produce failure in thetest material or when the reference material is very sensitive toan exposure stress that has very little effect on the test material.NOTE 5Definitions for control and reference material that are appro-priate to weathering tests are found in Terminology G113.NOTE 6Practice G156 describes procedures for selecting and charac-terizing weathering reference materials used to establish consistency ofoperating conditions in a laboratory accelerated test.NOTE 7Results from accelerated exposure tests should only be used toestablish a pass/fail approval of materials after a specific time of exposureto a prescribed set of conditions when the variability in the exposure andproperty measurement procedure has been quantified so that statisticallysignificant pass/fail judgments can be made.5. Requirements for Laboratory Exposure Devices5.1 Light Source5.1.1 The exposure device shall provide for placement ofspecimens and any designated sensing devices in positionswhich provide uniform irradiance by the light source.NOTE 8In some devices, several individual light sources are usedsimultaneously. In these devices, the term light source refers to thecombination of individual light sources being used.5.1.2 Manufacturers of exposure devices shall assure thatthe irradiance at any location in the area used for specimenexposures is at least 70 of the maximum irradiance mea-sured in this area. Procedures for measuring irradiance unifor-mity are found in Annex A1.NOTE 9During use, the irradiance uniformity in exposure devices canbe affected by several factors, such as deposits, which can develop on theoptical s
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