ASTM G178-2016 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: G178 09G178 16Standard 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 G178; the number immediately following the desi

2、gnation 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 describes the de

3、termination of the relative actinic effects of individual spectral bands of an exposure sourceon a material. The activation spectrum is specific to the light source to which the material is exposed to obtain the activationspectrum. A light source with a different spectral power distribution will pro

4、duce a different activation spectrum.1.2 This practice describes two procedures for determining an activation spectrum. One uses sharp cut-on UV/visibletransmitting filters and the other uses a spectrograph to determine the relative degradation caused by individual spectral regions.NOTE 1Other techn

5、iques can be used to isolate the effects of individual spectral bands of a light source, for example, interference filters.1.3 The techniques are applicable to determination of the spectral effects of solar radiation and laboratory accelerated testdevices on a material.They are described for the UVr

6、egion, but can be extended into the visible region using different cut-on filtersand appropriate spectrographs.1.4 The techniques are applicable to a variety of materials, both transparent and opaque, including plastics, paints, inks, textilesand others.1.5 The optical and/or physical property chang

7、es in a material can be determined by various appropriate methods. The methodsof evaluation are beyond the scope of this practice.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establi

8、sh appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.NOTE 2There is no ISO standard that is equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:2D256 Test Methods for Determining the Izod Pendulum Impact Resistance of Plas

9、ticsD638 Test Method for Tensile Properties of PlasticsD822 Practice for Filtered Open-Flame Carbon-Arc Exposures of Paint and Related CoatingsD1435 Practice for Outdoor Weathering of PlasticsD1499 Practice for Filtered Open-Flame Carbon-Arc Exposures of PlasticsD2244 Practice for Calculation of Col

10、or Tolerances and Color Differences from Instrumentally Measured Color CoordinatesD2565 Practice for Xenon-Arc Exposure of Plastics Intended for Outdoor ApplicationsD4141 Practice for Conducting Black Box and Solar Concentrating Exposures of CoatingsD4329 Practice for Fluorescent Ultraviolet (UV) La

11、mp Apparatus Exposure of PlasticsD4364 Practice for Performing Outdoor Accelerated Weathering Tests of Plastics Using Concentrated SunlightD4459 Practice for Xenon-Arc Exposure of Plastics Intended for Indoor ApplicationsD4508 Test Method for Chip Impact Strength of PlasticsD4587 Practice for Fluore

12、scent UV-Condensation Exposures of Paint and Related Coatings1 This practice is under the jurisdiction of ASTM Committee G03 on Weathering and Durability and is the direct responsibility of Subcommittee G03.01 on JointWeathering Projects.Current edition approved April 15, 2009Feb. 1, 2016. Published

13、 June 2009February 2016. Originally approved in 2003. Last previous edition approved in 20032009 asG17803. DOI: 10.1520/G0178-09. 09. DOI: 10.1520/G0178-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM

14、 Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically pos

15、sible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, W

16、est Conshohocken, PA 19428-2959. United States1D5031 Practice for Enclosed Carbon-Arc Exposure Tests of Paint and Related CoatingsD6360 Practice for Enclosed Carbon-Arc Exposures of PlasticsD6695 Practice for Xenon-Arc Exposures of Paint and Related CoatingsE275 Practice for Describing and Measuring

17、 Performance of Ultraviolet and Visible SpectrophotometersE313 Practice for Calculating Yellowness and Whiteness Indices from Instrumentally Measured Color CoordinatesE925 Practice for Monitoring the Calibration of Ultraviolet-Visible Spectrophotometers whose Spectral Bandwidth does notExceed 2 nmG7

18、 Practice for Atmospheric Environmental Exposure Testing of Nonmetallic MaterialsG24 Practice for Conducting Exposures to Daylight Filtered Through GlassG90 Practice for Performing Accelerated Outdoor Weathering of Nonmetallic Materials Using Concentrated Natural SunlightG113 Terminology Relating to

19、 Natural and Artificial Weathering Tests of Nonmetallic MaterialsG147 Practice for Conditioning and Handling of Nonmetallic Materials for Natural and Artificial Weathering TestsG152 Practice for Operating Open Flame Carbon Arc Light Apparatus for Exposure of Nonmetallic MaterialsG153 Practice for Op

20、erating Enclosed Carbon Arc Light Apparatus for Exposure of Nonmetallic MaterialsG154 Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Nonmetallic MaterialsG155 Practice for Operating Xenon Arc Light Apparatus for Exposure of Non-Metallic Materials3. Terminology3.1

21、Definitions given in Terminology G113 are applicable to this practice.3.2 Definitions of Terms Specific to This Standard:3.2.1 activation spectrum, nthe spectral sensitivity of a material specific to the spectral power distribution of the source towhich the material is exposed as a function of a spe

22、cified property measurement.3.2.1.1 DiscussionThe activation spectrum of a material exhibits peak sensitivity to the spectral region in which the combination of the radiationintensity, absorption of the radiation by the material and quantum efficiency of degradation produce the maximum damage. Thus,

23、activation spectra show that many materials exhibit greater damage by wavelengths longer than the shortest emitted by theradiation source (see Fig. X1.4 and Fig. X1.8). Since activation spectra relate to the spectral emission properties of the radiationsource, the activation spectrum varies with the

24、 type of radiation source to which the material is exposed.3.2.2 incremental degradation, nthe increase in degradation in the specimen exposed behind the shorter wavelength cut-onfilter of the pair due to the addition of short UV wavelengths transmitted by the filter.3.2.3 incremental ultraviolet, n

25、the additional short wavelength ultraviolet transmitted by the shorter wavelength cut-on filterof the pair of sharp cut-on UV/VIS transmitting glass filters. It is represented by the spectral band (see 3.2.43.2.5).3.2.4 sharp cut-on UV/VIS transmitting glass filters, nfilters that screen out the sho

26、rt wavelengths and transmit radiationlonger than the cut-on wavelength. The transmittance increases sharply from 5 %, the cut-on wavelength, to 72 % within a spectralrange of about 20 nm. They are also referred to as longpass filters.3.2.5 spectral band, nthe spectral region defined by the differenc

27、e in transmittance of a pair of the sharp cut-on UV/VIStransmitting glass filters. It is also referred to as the incremental ultraviolet.3.2.6 spectral band pass, nthe spectral range of the spectral band at the delta 20 % transmittance level. It is the spectral rangeof the incremental ultraviolet ma

28、inly responsible for the incremental degradation.3.2.6.1 DiscussionThe definition of this term differs from that commonly applied to the spectral bandpass, also referred to as the spectral bandwidth,of a narrow band filter or the radiant energy leaving the exit slit of a monochromator. These terms a

29、re defined as the full widthat half-maximum, FWHM, that is, the wavelength range at one half the peak height of the spectral band.3.2.7 cumulative spectral sensitivity curve, na plot of the cumulative effect on the optical or physical properties of a materialof addition of progressively shorter wave

30、lengths of the source to the longer wavelength exposure with progressive decrease inwavelength of the sharp cut-on UV/visible transmitting filter.4. Significance and Use4.1 The activation spectrum identifies the spectral region(s) of the specific exposure source used that may be primarilyresponsible

31、 for changes in appearance and/or physical properties of the material.4.2 The spectrographic technique uses a prism or grating spectrograph to determine the effect on the material of isolated narrowspectral bands of the light source, each in the absence of other wavelengths.G178 1624.3 The sharp cut

32、-on filter technique uses a specially designed set of sharp cut-on UV/visible transmitting glass filters todetermine the relative actinic effects of individual spectral bands of the light source during simultaneous exposure to wavelengthslonger than the spectral band of interest.4.4 Both the spectro

33、graphic and filter techniques provide activation spectra, but they differ in several respects:4.4.1 The spectrographic technique generally provides better resolution since it determines the effects of narrower spectralportions of the light source than the filter technique.4.4.2 The filter technique

34、is more representative of the polychromatic radiation to which samples are normally exposed withdifferent, and sometimes antagonistic, photochemical processes often occurring simultaneously. However, since the filters onlytransmit wavelengths longer than the cut-on wavelength of each filter, antagon

35、istic processes by wavelengths shorter than thecut-on are eliminated.4.4.3 In the filter technique, separate specimens are used to determine the effect of the spectral bands and the specimens aresufficiently large for measurement of both mechanical and optical changes. In the spectrographic techniqu

36、e, except in the case ofspectrographs as large as the Okazaki type (1),3 a single small specimen is used to determine the relative effects of all the spectralbands. Thus, property changes are limited to those that can be measured on very small sections of the specimen.4.5 The information provided by

37、 activation spectra on the spectral region of the light source responsible for the degradation intheory has application to stabilization as well as to stability testing of polymeric materials (2).4.5.1 Activation spectra based on exposure of the unstabilized material to solar radiation identify the

38、light screeningrequirements and thus the type of ultraviolet absorber to use for optimum screening protection. The closer the match of theabsorption spectrum of a UV absorber to the activation spectrum of the material, the more effective the screening. However, a goodmatch of the UVabsorption spectr

39、um of the UVabsorber to the activation spectrum does not necessarily assure adequate protectionsince it is not the only criteria for selecting an effective UV absorber. Factors such as dispersion, compatibility, migration andothers can have a significant influence on the effectiveness of a UV absorb

40、er (see Note 3). The activation spectrum must bedetermined using a light source that simulates the spectral power distribution of the one to which the material will be exposed underuse conditions.NOTE 3In a study by ASTM G03.01, the activation spectrum of a copolyester based on exposure to borosilic

41、ate glass-filtered xenon arc radiationpredicted that UV absorber A would be superior to UV absorber B in outdoor use because of stronger absorption of the harmful wavelengths of solarsimulated radiation. However, both additives protected the copolyester to the same extent when exposed either to xeno

42、n arc radiation or outdoors.4.5.2 Comparison of the activation spectrum of the stabilized with that of the unstabilized material provides information on thecompleteness of screening and identifies any spectral regions that are not adequately screened.4.5.3 Comparison of the activation spectrum of a

43、material based on solar radiation with those based on exposure to other typesof light sources provides information useful in selection of the appropriate artificial test source. An adequate match of the harmfulwavelengths of solar radiation by the latter is required to simulate the effects of outdoo

44、r exposure. Differences between the naturaland artificial source in the wavelengths that cause degradation can result in different mechanisms and type of degradation.4.5.4 Published data have shown that better correlations can be obtained between natural weathering tests under differentseasonal cond

45、itions when exposures are timed in terms of solar UV radiant exposure only rather than total solar radiant exposure.Timing exposures based on only the portion of the UV identified by the activation spectrum to be harmful to the material canfurther improve correlations. However, while it is an improv

46、ement over the way exposures are currently timed, it does not takeinto consideration the effect of moisture and temperature.4.6 Over a long test period, the activation spectrum will register the effect of the different spectral power distributions causedby lamp or filter aging or daily or seasonal v

47、ariation in solar radiation.4.7 In theory, activation spectra may vary with differences in sample temperature. However, similar activation spectra have beenobtained at ambient temperature (by the spectrographic technique) and at about 65C (by the filter technique) using the same typeof radiation sou

48、rce.5. Activation Spectrum Procedure Using Sharp Cut-On Filter Technique5.1 Spectral Bands of Irradiation:5.1.1 Select glass types for the sharp cut-on UV/visible transmitting glass filters which provide a spectral shift of approximately10 nm at 40 % transmittance between filter pairs when ground to

49、 appropriate thicknesses. It may be necessary to use filters frommore than one source. The exact thickness to which each filter is ground is governed by the incremental ultraviolet transmitted bythe shorter wavelength filter of the pair. Adjust the thicknesses so that the incremental ultraviolet is within 10 % of the averageof the incremental ultraviolet of all filter pairs. The method for determining the incremental ultraviolet is described in 5.1.3.NOTE 4Typically, 12 or 13 filters with cut-on wavelengths ranging from 265 to 375 nm are used to determine the effect