ASTM G178-2003 Standard Practice for Determining the Activation Spectrum of a Material (Wavelength Sensitivity to an Exposure Source) Using the Sharp Cut-On Filter or Spectrographi.pdf

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1、Designation: G 178 03Standard Practice forDetermining the Activation Spectrum of a Material(Wavelength Sensitivity to an Exposure Source) Using theSharp Cut-On Filter or Spectrographic Technique1This standard is issued under the fixed designation G 178; the number immediately following the designati

2、on 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes the determ

3、ination of the relativeactinic effects of individual spectral bands of an exposuresource on a material. The activation spectrum is specific to thelight source to which the material is exposed to obtain theactivation spectrum. A light source with a different spectralpower distribution will produce a

4、different activation spectrum.1.2 This practice describes two procedures for determiningan activation spectrum. One uses sharp cut-on UV/visibletransmitting filters and the other uses a spectrograph todetermine the relative degradation caused by individual spec-tral regions.NOTE 1Other techniques ca

5、n be used to isolate the effects ofindividual spectral bands of a light source, for example, interferencefilters.1.3 The techniques are applicable to determination of thespectral effects of solar radiation and laboratory acceleratedtest devices on a material. They are described for the UVregion, but

6、 can be extended into the visible region usingdifferent cut-on filters and appropriate spectrographs.1.4 The techniques are applicable to a variety of materials,both transparent and opaque, including plastics, paints, inks,textiles and others.1.5 The optical and/or physical property changes in amate

7、rial can be determined by various appropriate methods.The methods of evaluation are beyond the scope of thispractice.1.6 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-priat

8、e safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 2There is no ISO standard that is equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:D 256 Test Method for Determining the Izod PendulumImpact Resistance of Notched Specimens

9、 of Plastics2D 638 Test Method for Tensile Properties of Plastics2D 822 Practice for Filtered Open-Flame Carbon Arc Expo-sures of Paint and Related Coatings3D 1435 Practice for Outdoor Weathering of Plastics2D 1499 Practice for Operating Light- and Water-ExposureApparatus (Carbon Arc Type) for Expos

10、ure of Plastics2D 2244 Test Method for Calculation of Color Differencesfrom Instrumentally Measured Color Coordinates3D 2565 Practice for Operating Xenon Arc Type Light Ex-posure Apparatus With and Without Water for Exposure ofPlastics4D 4141 Practice for Conducting Accelerated Outdoor Expo-sure Tes

11、ts of Coatings3D 4329 Practice for Operating Light- and Water-ExposureApparatus (Fluorescent UV Condensation Type) for Expo-sure of Plastics5D 4364 Practice for Performing Accelerated OutdoorWeathering of Plastics Using Concentrated Natural Sun-light5D 4459 Practice for Operating an Accelerated Ligh

12、tfastnessXenon Arc Type Light Exposure Apparatus for the Expo-sure of Plastics for Indoor Applications5D 4508 Test Method for Chip Impact Strength of Plastics5D 4587 Practice for Fluorescent UV-Condensation Expo-sures of Paint and Related Coatings3D 5031 Practice for Enclosed Carbon Arc Exposure Tes

13、ts ofPaint and Related Coatings3D 6360 Practice for Enclosed Carbon-Arc Exposures ofPlastics4D 6695 Practice for Xenon-Arc Exposures of Paint andRelated Coatings3E 275 Practice for Describing and Measuring Performanceof Ultraviolet, Visible and Near Infrared Spectrophotom-eters61This practice is und

14、er the jurisdiction of ASTM Committee G03 on Weatheringand Durability and is the direct responsibility of Subcommittee G03.01 on JointWeathering Projects.Current edition approved July 10, 2003. Published September 2003.2Annual Book of ASTM Standards, Vol 08.01.3Annual Book of ASTM Standards, Vol 06.

15、01.4Annual Book of ASTM Standards, Vol 08.02.5Annual Book of ASTM Standards, Vol 08.03.6Annual Book of ASTM Standards, Vol 03.06.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.E 313 Test Method for Indexes of Whiteness and Yellow-ne

16、ss of Near-White Opaque Materials3E 925 Practice for Periodic Calibration for Narrow Band-Pass Spectrophotometers6G 7 Practice for Atmospheric Environmental ExposureTesting of Nonmetallic Materials7G 24 Practice for Conducting Exposures to Daylight Fil-tered Through Glass7G 90 Practice for Performin

17、g Accelerated Outdoor Weath-ering of Nonmetallic Materials Using Concentrated Natu-ral Sunlight7G 113 Terminology Relating to Natural and ArtificialWeathering Tests of Nonmetallic Materials7G 147 Practice for Conditioning and Handling of Nonme-tallic Materials for Natural and Artificial Weathering T

18、ests7G 152 Practice for Operating Open Flame Carbon Arc LightApparatus for Exposure of Nonmetallic Materials7G 153 Practice for Operating Enclosed Carbon Arc LightApparatus for Exposure of Nonmetallic Materials7G 154 Practice for Operating Fluorescent Light Apparatusfor UV Exposure of Nonmetallic Ma

19、terials7G 155 Practice for Operating Xenon Arc Light Apparatusfor Exposure of Nonmetallic Materials73. Terminology3.1 Definitions given in Terminology G 113 are applicableto this practice.3.2 Definitions of Terms Specific to This Standard:3.2.1 incremental degradation, n the increase in degrada-tion

20、 in the specimen exposed behind the shorter wavelengthcut-on filter of the pair due to the addition of short UVwavelengths transmitted by the filter.3.2.2 incremental ultraviolet, nthe additional short wave-length ultraviolet transmitted by the shorter wavelength cut-onfilter of the pair of sharp cu

21、t-on UV/VIS transmitting glassfilters. It is represented by the spectral band (see 3.2.4).3.2.3 sharp cut-on UV/VIS transmitting glass filters,nfilters that screen out the short wavelengths and transmitradiation longer than the cut-on wavelength. The transmittanceincreases sharply from 5 %, the cut-

22、on wavelength, to 72 %within a spectral range of about 20 nm. They are also referredto as longpass filters.3.2.4 spectral band, nthe spectral region defined by thedifference in transmittance of a pair of the sharp cut-onUV/VIS transmitting glass filters. It is also referred to as theincremental ultr

23、aviolet.3.2.5 spectral band pass, nthe spectral range of thespectral band at the delta 20 % transmittance level. It is thespectral range of the incremental ultraviolet mainly responsiblefor the incremental degradation.3.2.5.1 DiscussionThe definition of this term differs fromthat commonly applied to

24、 the spectral bandpass, also referredto as the spectral bandwidth, of a narrow band filter or theradiant energy leaving the exit slit of a monochromator. Theseterms are defined as the full width at half-maximum, FWHM,that is, the wavelength range at one half the peak height of thespectral band.3.2.6

25、 cumulative spectral sensitivity curve, na plot of thecumulative effect on the optical or physical properties of amaterial of addition of progressively shorter wavelengths of thesource to the longer wavelength exposure with progressivedecrease in wavelength of the sharp cut-on UV/visible trans-mitti

26、ng filter.4. Significance and Use4.1 The activation spectrum identifies the spectral region(s)of the specific exposure source used that may be primarilyresponsible for changes in appearance and/or physical proper-ties of the material.4.2 The spectrographic technique uses a prism or gratingspectrogra

27、ph to determine the effect on the material of isolatednarrow spectral bands of the light source, each in the absenceof other wavelengths.4.3 The sharp cut-on filter technique uses a specially de-signed set of sharp cut-on UV/visible transmitting glass filtersto determine the relative actinic effects

28、 of individual spectralbands of the light source during simultaneous exposure towavelengths longer than the spectral band of interest.4.4 Both the spectrographic and filter techniques provideactivation spectra, but they differ in several respects:4.4.1 The spectrographic technique generally provides

29、 bet-ter resolution since it determines the effects of narrowerspectral portions of the light source than the filter technique.4.4.2 The filter technique is more representative of thepolychromatic radiation to which samples are normally ex-posed with different, and sometimes antagonistic, photochemi

30、-cal processes often occurring simultaneously. However, sincethe filters only transmit wavelengths longer than the cut-onwavelength of each filter, antagonistic processes by wave-lengths shorter than the cut-on are eliminated.4.4.3 In the filter technique, separate specimens are used todetermine the

31、 effect of the spectral bands and the specimens aresufficiently large for measurement of both mechanical andoptical changes. In the spectrographic technique, except in thecase of spectrographs as large as the Okazaki type (1),8a singlesmall specimen is used to determine the relative effects of allth

32、e spectral bands. Thus, property changes are limited to thosethat can be measured on very small sections of the specimen.4.5 The information provided by activation spectra on thespectral region of the light source responsible for the degrada-tion in theory has application to stabilization as well as

33、 tostability testing of polymeric materials (2).4.5.1 Activation spectra based on exposure of the unstabi-lized material to solar radiation identify the light screeningrequirements and thus the type of ultraviolet absorber to use foroptimum screening protection. The closer the match of theabsorption

34、 spectrum of a UV absorber to the activationspectrum of the material, the more effective the screening . Theactivation spectrum must be determined using a light source7Annual Book of ASTM Standards, Vol 14.02.8The boldface numbers in parentheses refer to the list of references at the end ofthis stan

35、dard.G178032that simulates the spectral power distribution of the one towhich the material will be exposed under use conditions.However, a good match of the UV absorption spectrum of theUV absorber to the activation spectrum does not necessarilyassure adequate protection since it is not the only cri

36、teria forselecting an effective UV absorber. Factors such as dispersion,compatibility, migration and others can have a significantinfluence on the effectiveness of a UV absorber (see Note 3).NOTE 3In a study by ASTM G03.01, the activation spectrum of acopolyester based on exposure to borosilicate gl

37、ass-filtered xenon arcradiation predicted that UV absorber A would be superior to UV absorberB in outdoor use because of stronger absorption of the harmful wave-lengths of solar simulated radiation. However, both additives protected thecopolyester to the same extent when exposed either to xenon arc

38、radiationor outdoors. A research report on the study and interpretation of test resultsis being written.4.5.2 Comparison of the activation spectrum of the stabi-lized with that of the unstabilized material provides informa-tion on the completeness of screening and identifies anyspectral regions that

39、 are not adequately screened.4.5.3 Comparison of the activation spectrum of a materialbased on solar radiation with those based on exposure to othertypes of light sources provides information useful in selectionof the appropriate artificial test source. An adequate match ofthe harmful wavelengths of

40、 solar radiation by the latter isrequired to simulate the effects of outdoor exposure. Differ-ences between the natural and artificial source in the wave-lengths that cause degradation can result in different mecha-nisms and type of degradation.4.5.4 Published data have shown that better correlation

41、s canbe obtained between natural weathering tests under differentseasonal conditions when exposures are timed in terms of solarUV radiant exposure only rather than total solar radiantexposure. Timing exposures based on only the portion of theUV identified by the activation spectrum to be harmful to

42、thematerial can further improve correlations. However, while it isan improvement over the way exposures are currently timed, itdoes not take into consideration the effect of moisture andtemperature.4.6 Over a long test period, the activation spectrum willregister the effect of the different spectral

43、 power distributionscaused by lamp or filter aging or daily or seasonal variation insolar radiation.4.7 In theory, activation spectra may vary with differencesin sample temperature. However, similar activation spectrahave been obtained at ambient temperature (by the spectro-graphic technique) and at

44、 about 65C (by the filter technique)using the same type of radiation source.5. Activation Spectrum Procedure Using Sharp Cut-OnFilter Technique5.1 Spectral Bands of Irradiation:5.1.1 Select glass types for the sharp cut-on UV/visibletransmitting glass filters which provide a spectral shift ofapproxi

45、mately 10 nm at 40 % transmittance between filter pairswhen ground to appropriate thicknesses. It may be necessary touse filters from more than one source. The exact thickness towhich each filter is ground is governed by the incrementalultraviolet transmitted by the shorter wavelength filter of thep

46、air. Adjust the thicknesses so that the incremental ultravioletis within 10 % of the average of the incremental ultraviolet ofall filter pairs. The method for determining the incrementalultraviolet is described in 5.1.3.NOTE 4Typically, 12 or 13 filters with cut-on wavelengths rangingfrom 265 to 375

47、 nm are used to determine the effects of 10 spectral bands,each approximately 20 nm wide, in the solar UV region. A larger set offilters can be used to reduce the width of each spectral band, but it wouldextend the time required to produce degradation by each of the spectralregions. The filter size

48、is normally 2 by 2 in., but other sizes up to 6 by 6in. can be used.NOTE 5The spectral transmittance curves of a typical set of filters areshown in Figs. X1.1 and X1.2 in the Appendix.NOTE 6Due to variations in the melt of each glass type, the filter typesand thicknesses used for one filter set may

49、not be applicable to other sets.5.1.2 Spectral Transmittance Data:5.1.2.1 Use a UV/visible spectrophotometer that produceseither digital data or an analog curve to measure the spectraltransmittance of each filter from the spectral region of com-plete blocking at the short wavelength end to maximumtransmittance at the long wavelength end.5.1.2.2 Determine the wavelength calibration and linearityof the spectrophotometer as described in either Practice E 275or E 925. Check the 0 % and 100 % baselines and adjust, ifnecessary, according to manufacturers recommendations. Ifthe 10