ASTM G151-19

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: G151 − 19
Standard Practice for
Exposing Nonmetallic Materials in Accelerated Test Devices
that Use Laboratory Light Sources
This standard is issued under the fixed designation G151; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 Thispracticecoversgeneralprocedurestobeusedwhen
1.5 This international standard was developed in accor-
exposing nonmetallic materials in accelerated test devices that
dance with internationally recognized principles on standard-
use laboratory light sources. Detailed information regarding
ization established in the Decision on Principles for the
procedures to be used for specific devices are found in
Development of International Standards, Guides and Recom-
standards describing the particular device being used. For
mendations issued by the World Trade Organization Technical
example, detailed information covering exposures in devices
Barriers to Trade (TBT) Committee.
that use open flame carbon arc, enclosed carbon arc, xenon arc,
and fluorescent UV light source are found in Practices G152,
2. Referenced Documents
G153, G154, and G155 respectively.
2.1 ASTM Standards:
NOTE 1—Carbon-arc, xenon arc, and fluorescent UV exposures were
also described in Practices G23, G26, and G53 which referred to very D618 Practice for Conditioning Plastics for Testing
specific equipment designs. Practices G152, G153, and G154, and G155
D3924 Specification for Standard Environment for Condi-
are performance based standards that replace Practices G23, G26, and
tioning and Testing Paint, Varnish, Lacquer, and Related
G53.
Materials (Withdrawn 2016)
1.2 This practice also describes general performance re-
D5870 Practice for Calculating Property Retention Index of
quirementsfordevicesusedforexposingnonmetallicmaterials
Plastics
to laboratory light sources. This information is intended
E41 Terminology Relating to Conditioning (Withdrawn
primarily for producers of laboratory accelerated exposure
2019)
devices.
E171 Practice for Conditioning and Testing Flexible Barrier
1.3 This practice provides information on the use and Packaging
E644 Test Methods for Testing Industrial Resistance Ther-
interpretation of data from accelerated exposure tests. Specific
information about methods for determining the property of a mometers
E691 Practice for Conducting an Interlaboratory Study to
nonmetallic material before and after exposure are found in
standards describing the method used to measure each prop- Determine the Precision of a Test Method
E772 Terminology of Solar Energy Conversion
erty. Information regarding the reporting of results from
exposure testing of plastic materials is described in Practice E839 Test Methods for Sheathed Thermocouples and
Sheathed Thermocouple Cable
D5870.
G23 Practice for Operating Light-Exposure Apparatus
NOTE2—GuideG141providesinformationforaddressingvariabilityin
(Carbon-Arc Type) With and Without Water for Exposure
exposure testing of nonmetallic materials. Guide G169 provides informa-
(Withdrawn 2000)
of Nonmetallic Materials
tion for application of statistics to exposure test results.
NOTE 3—This standard is technically equivalent to ISO 4892, Part 1. G26 Practice for Operating Light-Exposure Apparatus
(Xenon-Arc Type) With and Without Water for Exposure
1.4 This standard does not purport to address all of the
of Nonmetallic Materials (Discontinued 2001) (With-
safety concerns, if any, associated with its use. It is the
drawn 2000)
responsibility of the user of this standard to establish appro-
1 2
This practice is under the jurisdiction ofASTM Committee G03 on Weathering For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and Durability and is the direct responsibility of Subcommittee G03.03 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Simulated and Controlled Exposure Tests. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Jan. 1, 2019. Published February 2019. Originally the ASTM website.
approved in 1997. Last previous edition approved in 2010 as G151 – 10. DOI: The last approved version of this historical standard is referenced on
10.1520/G0151-19. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G151 − 19
G53 Practice for Operating Light-and Water-Exposure Ap- 4.1.1 When conducting exposures in devices that use labo-
paratus (Fluorescent UV-Condensation Type) for Expo- ratory light sources, it is important to consider how well the
sure of Nonmetallic Materials (Withdrawn 2000) acceleratedtestconditionswillreproducepropertychangesand
G113 Terminology Relating to Natural andArtificial Weath- failure modes associated with end-use environments for the
ering Tests of Nonmetallic Materials materialsbeingtested.Inaddition,itisessentialtoconsiderthe
G130 Test Method for Calibration of Narrow- and Broad- effects of variability in both the accelerated test and outdoor
Band Ultraviolet Radiometers Using a Spectroradiometer exposures when setting up exposure experiments and when
G141 Guide for Addressing Variability in Exposure Testing interpreting the results from accelerated exposure tests.
of Nonmetallic Materials 4.1.2 No laboratory exposure test can be specified as a total
G147 Practice for Conditioning and Handling of Nonmetal- simulation of actual use conditions in outdoor environments.
lic Materials for Natural and Artificial Weathering Tests Results obtained from these laboratory accelerated exposures
G152 Practice for Operating Open Flame Carbon Arc Light can be considered as representative of actual use exposures
Apparatus for Exposure of Nonmetallic Materials only when the degree of rank correlation has been established
G153 Practice for Operating Enclosed Carbon Arc Light for the specific materials being tested and when the type of
Apparatus for Exposure of Nonmetallic Materials degradation is the same. The relative durability of materials in
G154 Practice for Operating Fluorescent Ultraviolet (UV)
actualuseconditionscanbeverydifferentindifferentlocations
Lamp Apparatus for Exposure of Nonmetallic Materials because of differences in UV radiation, time of wetness,
G155 Practice for Operating XenonArc LightApparatus for
relative humidity, temperature, pollutants, and other factors.
Exposure of Non-Metallic Materials Therefore, even if results from a specific exposure test con-
G156 Practice for Selecting and Characterizing Weathering
ducted according to this practice are found to be useful for
Reference Materials comparing the relative durability of materials exposed in a
G169 Guide for Application of Basic Statistical Methods to
particular exterior environment, it cannot be assumed that they
Weathering Tests will be useful for determining relative durability of the same
G177 Tables for Reference Solar Ultraviolet Spectral Distri-
materials for a different environment.
butions: Hemispherical on 37° Tilted Surface 4.1.3 Even though it is very tempting, calculation of an
2.2 ISO Standards: acceleration factor relating x h or megajoules of radiant
ISO 4892, Part 1 Plastics: Exposure to laboratory Light exposure in a laboratory accelerated test to y months or years
Sources—General Guidance of exterior exposure is not recommended. These acceleration
ISO 9370 Plastics: Instrumental Determination of Radiant factors are not valid for several reasons.
Exposure in Weathering Tests—General Guidance and 4.1.3.1 Acceleration factors are material dependent and can
Basic Test Method be significantly different for each material and for different
2.3 CIE Document: formulations of the same material.
CIE Publication Number 85: 1989 Technical Report—Solar 4.1.3.2 Variability in the rate of degradation in both actual
Spectral Irradiance use and laboratory accelerated exposure test can have a
significant effect on the calculated acceleration factor.
2.4 Other Documents:
4.1.3.3 Acceleration factors calculated based on the ratio of
IES LM-58-13 Spectroradiometric Measurement Methods
irradiance between a laboratory light source and solar
for Light Sources (2013 or Later)
radiation,evenwhenidenticalbandpassesareused,donottake
NIST SP250-89 Spectral Irradiance Calibrations
into consideration the effects on a material of irradiance,
2.5 ASTM Adjuncts:
temperature, moisture, and differences in spectral power dis-
SMARTS2,SimpleModelforAtmosphericTransmissionof
tribution between the laboratory light source and solar radia-
Sunshine
tion.
3. Terminology
NOTE 4—If use of an acceleration factor is desired in spite of the
3.1 Definitions—The definitions given in Terminologies
warnings given in this practice, such acceleration factors for a particular
material are only valid if they are based on data from a sufficient number
E41, E772, and G113 are applicable to this practice.
of separate exterior and laboratory accelerated exposures so that results
used to relate times to failure in each exposure can be analyzed using
4. Significance and Use
statistical methods. An example of a statistical analysis using multiple
4.1 Significance:
laboratory and exterior exposures to calculate an acceleration factor is
described by J. A. Simms (
1).
4.1.4 There are a number of factors that may decrease the
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
degree of correlation between accelerated tests using labora-
4th Floor, New York, NY 10036, http://www.ansi.org.
Available from the Commission Internationale de L’Eclairage, CIE, Central
tory light sources and exterior exposures. More specific infor-
Bureau, Kegelgasse 27,A-1030Vienna,Austria or the U.S. National Committee for
mation on how each factor may alter stability ranking of
CIE, National Institute for Science and Technology, Gaithersburg, MD.
6 materials is given in Appendix X1.
Available from Illuminating Engineering Society of North America (IESNA),
120 Wall Street, New York, NY 10005, https://www.ies.org/.
Available from National Institute of Standards and Technology (NIST), 100
Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov.
8 9
Available from ASTM International Headquarters. Order Adjunct No. The boldface numbers in parentheses refer to the list of references at the end of
ADJG173CD. Original adjunct produced in 2005. this standard.
G151 − 19
4.1.4.1 Differences in the spectral distribution between the 5.1.1 The exposure device shall provide for placement of
laboratory light source and solar radiation. specimens and any designated sensing devices in positions
4.1.4.2 Light intensities higher than those experienced in which provide uniform irradiance by the light source.
actual use conditions.
NOTE 8—In some devices, several individual light sources are used
4.1.4.3 Test conditions where specimens are exposed con-
simultaneously. In these devices, the term light source refers to the
tinuously to light when actual use conditions provide alternate
combination of individual light sources being used.
periods of light and dark.
5.1.2 Manufacturers of exposure devices shall assure that
4.1.4.4 Specimen temperatures higher than those in actual
the irradiance at any location in the area used for specimen
conditions.
exposures is at least 70 % of the maximum irradiance mea-
4.1.4.5 Exposure conditions that produce unrealistic tem-
sured in this area. Procedures for measuring irradiance unifor-
perature differences between light and dark colored specimens.
mity are found in Annex A1.
4.1.4.6 Exposure conditions that do not have any tempera-
NOTE 9—During use, the irradiance uniformity in exposure devices can
ture cycling or that produce temperature cycling, or thermal
be affected by several factors, such as deposits, which can develop on the
shock, or both, that is not representative of use conditions.
optical system and chamber walls. Irradiance uniformity also can be
4.1.4.7 Unrealistically high or low levels of moisture.
affected by the type and number of specimens being exposed. The
4.1.4.8 Absence of biological agents or pollutants.
irradiance uniformity as assured by the manufacturer is valid for new
equipment and well defined measuring conditions.
4.2 Use ofAccelerated Tests with Laboratory Light Sources:
4.2.1 Results from accelerated exposure tests conducted 5.1.3 Periodic repositioning of the specimens during expo-
according to this standard are best used to compare the relative
sure is not necessary if the irradiance at positions farthest from
performance of materials.Acommon application is conducting the point of maximum irradiance is at least 90 % of the
a test to establish that the level of quality of different batches
maximum measured irradiance.
doesnotvaryfromacontrolmaterialwithknownperformance.
5.1.4 If irradiance at any position in the area used for
Comparisons between materials are best made when they are
specimen exposure is between 70 and 90 % of the maximum
tested at the same time in the same exposure device. Results
irradiance, specimens shall be periodically repositioned to
can be expressed by comparing the exposure time or radiant
reducevariabilityinradiantexposure.Therepositioningsched-
exposure necessary to change a characteristic property to some
ule shall be agreed upon by all interested parties. Appendix X2
specified level.
describes some possible specimen placement and repositioning
4.2.1.1 Reproducibility of test results between laboratories
plans and frequencies.
has been shown to be good when the stability of materials is
NOTE 10—While not required in devices meeting the irradiance
evaluated in terms of performance ranking compared to other
uniformity requirements of 5.1.3, periodic specimen repositioning is a
materials or to a control (2, 3); therefore, exposure of a similar
good practice to reduce the variability in exposure stresses experienced
material of known performance (a control) at the same time as during the test interval.
the test materials is strongly recommended.
5.1.5 Replace lamps and filters according to the schedule
4.2.2 In some applications, weathering reference materials
recommended by the device manufacturer. Follow the appara-
are used to establish consistency of the operating conditions in
tus manufacturer’s instructions for lamp and filter replacement
an exposure test.
and for pre-aging of lamps or filters, or both.
4.2.3 Reference materials, for example, blue wool test
5.1.6 ASTM G177 describes a standard solar ultraviolet
fabric, also may be used for the purpose of timing exposures.
spectrum that can be used as a basis for comparing laboratory
In some cases, a reference material is exposed at the same time
accelerated light sources with sunlight. The atmospheric con-
as a test material and the exposure is conducted until there is a
ditions used in this standard solar spectrum were selected to
defined change in property of the reference material. The test
maximize the fraction of short wavelength solar ultraviolet
materialthenisevaluated.Insomecases,theresultsforthetest
radiation.
material are compared to those for the reference material.
NOTE 11—Previous versions of this standard used a solar spectrum
These are inappropriate uses of reference materials when they
defined in CIE Publication 85-1989, Table 4 as the benchmark for
are not sensitive to exposure stresses that produce failure in the
comparing light sources used in laboratory accelerated exposure tests to
test material or when the reference material is very sensitive to
solar radiation. Appendix X3 provides a comparison of the atmospheric
an exposure stress that has very little effect on the test material.
conditions and solar spectra of ASTM G177 and Table 4 of CIE 85.
NOTE 5—Definitions for control and reference material that are appro-
5.1.6.1 Direct radiation from xenon burners, open flame
priate to weathering tests are found in Terminology G113.
carbon arcs, and some fluorescent lamps contains considerable
NOTE 6—Practice G156 describes procedures for selecting and charac-
amountsofshortwavelengthultravioletradiationnotpresentin
terizing weathering reference materials used to establish consistency of
solar radiation. With proper selection of filters for these light
operating conditions in a laboratory accelerated test.
NOTE7—Resultsfromacceleratedexposuretestsshouldonlybeusedto sources, much of the short wavelength light can be eliminated.
establish a pass/fail approval of materials after a specific time of exposure
However, with many filters a small, but significant, amount of
to a prescribed set of conditions when the variability in the exposure and
this short wavelength (less than 300 nm) radiation is present in
property measurement procedure has been quantified so that statistically
the spectral distribution of the filtered light source. Fluorescent
significant pass/fail judgments can be made.
UVlampscanbeselectedtohaveaspectraloutputcorrespond-
5. Requirements for Laboratory Exposure Devices
ing to a particular ultraviolet region of solar radiation. The
5.1 Light Source: xenon arc, when appropriately filtered, produces radiation with
G151 − 19
a spectral power distribution that is a good simulation of surface temperature of individual test specimens, a specified
average solar radiation throughout the UV and visible region. black-panel sensor is used to measure and control temperature
5.1.7 The apparatus should have a means to monitor and within the test chamber. It is strongly recommended that the
control the specimen irradiance. black panel temperature sensor be mounted within the speci-
men exposure area so that it receives the same radiation and
NOTE 12—In apparatus that do not provide irradiance control, the
cooling conditions as a flat test panel surface. The black panel
specimen irradiance may vary over time as the source and some optical
filters used to modify its spectral distribution age. This variance may also may be located at a fixed distance position different from
contribute to differences between weathering tests conducted in different
the test specimens and calibrated for temperature in the
apparatus as well as those conducted in the same apparatus at separate
specimen exposure area. This is not recommended, however,
times.
because black panels mounted at a fixed position away from
5.1.7.1 In apparatus equipped with irradiance control, an
the specimens may not indicate temperatures representative of
irradiance set point control system comprised of an integrated
the test specimens, even if they are calibrated to record
on-boardirradiancesensorcoupledwithanelectronicfeedback
temperature at positions within the specimen exposure area,
loop shall operate to maintain the irradiance at the set point.
due to differences in light intensity and movement of air.
This control system shall be calibrated to report the irradiance
5.2.1.1 The type of mounting used for uninsulated black or
atthespecimenplanewhethertheon-boardirradiancesensoris
white panels (that is, whether the back of the panel is directly
located within the specimen plane or outside the specimen
exposed to air or if the panel is placed against a solid metal
plane.
backing) will have an effect on the conditions in the chamber.
5.1.7.2 The irradiance set point control system shall be
Describe the mounting used for the uninsulated black or white
calibratedatregularintervalsrelativetoanirradiancereference
panel in the test report.
device (that is, a radiometer or other suitable transfer calibra-
tionstandard)toassureacceptableaccuracyandreliability.The
NOTE 14—Previous versions of this standard specified an uninsulated
black panel with an open back subjected to the air within the exposure
irradiance set point control system shall be calibrated when
chamber. Tests using a different backing configuration may produce
replacing any component of the optical system (for example, at
different results. Therefore, if a user wishes to compare to historical
each lamp replacement or filter change) and each time the
exposure results, it is recommended that the user duplicate the previous
weathering method is changed. A full calibration of the
backing configuration of the uninsulated black panel.
irradiance set point control system shall be conducted at least
5.2.2 Exposure devices shall use either an uninsulated black
once per year. More frequent calibrations and intermediate
panel (commonly referred to as a black panel thermometer) or
checks are recommended.
an insulated black panel (commonly referred to as a black
5.1.7.3 Theirradiancereferencedeviceshallbecalibratedin
standard thermometer) as black panel sensor. Requirements for
accordance with ISO 9370 resulting in traceability to a
each type are found in Annex A2.
National Metrology Institute (NMI). This device shall be
5.2.3 The temperature indicated by the uninsulated black-
calibrated at regular intervals to assure acceptable measure-
panel or insulated thermometer depends on the irradiance of
ment uncertainty, traceability, and reliability. Refer to the
thelaboratorylightsourceandthetemperatureandspeedofair
manufacturer’s recommendation for guidance on calibration
moving in the test chamber. Uninsulated black-panel tempera-
interval.
tures generally correspond to those for dark coatings on metal
NOTE 13—For guidance on good laboratory practices for measurement
panels. Insulated black panel thermometer temperatures gen-
and calibration of irradiance see IES LM-58-13 and NIST SP250-89.
erally correspond to those for the exposed surface of dark
5.1.7.4 Spectrally selective radiometers within the chain of
samples with poor thermal conductivity. At conditions used in
traceability shall comply with one of the types specified in
typical exposure tests, the temperature indicated by an insu-
ISO 9370.Afull calibration of the spectrally selective radiom-
lated black panel thermometer will be 3–12 °C higher than an
eter shall be conducted in accordance with Test Method G130
uninsulated black panel thermometer. The response time for
at least once per year. More frequent calibrations are recom-
temperaturechangesisslightlyslowerforinsulatedblackpanel
mended.
thermometers compared to uninsulated black panel thermom-
5.1.7.5 The irradiance set point control system and the
eters.
irradiance reference device shall be calibrated in terms of
5.2.3.1 At low irradiance, the difference between the tem-
irradiance, E , for a defined wavelength or defined wavelength
e
perature indicated by an uninsulated black panel or insulated
interval. Common examples of irradiance control points and
black panel and the real specimen may be small. When light
spectral ranges used in commercial weathering apparatus
sources that emit very little infrared radiation are used, there
include 340 nm, 420 nm, 300-400 nm, and 300-800 nm. Other
generally will be very small difference in temperatures indi-
control points and spectral ranges may be used as agreed upon
cated by the two types of black panels or between light and
by all interested parties.
dark colored specimens.
5.2 Temperature:
NOTE 15—There can be differences in temperature indicated by a single
5.2.1 The surface temperature of exposed materials depends
type of black panel thermometer, depending on the specific design of the
on the ambient temperature, the amount of radiation absorbed,
device supplied by different manufacturers. Work is being conducted
the emissivity of the specimen, the thermal conduction within
withinSubcommittee6ISOTC/61tocharacterizethedifferencesbetween
the specimen, and the heat transmission between specimen and
the different types of temperature sensing devices and between tempera-
air or specimen holder. Since it is not practical to monitor the ture sensing devices of the same type.
G151 − 19
5.2.4 In order to evaluate the range of surface temperatures anions, organics, and particularly silica, exposed specimens
of the exposed specimens, the use of an uninsulated or will develop spots or stains that do not occur in exterior
insulated white panel thermometer is recommended, in addi- exposures.Unlessotherwisespecified,waterusedforspecimen
tion to the uninsulated black panel or insulated black panel wettingshallhaveamaximumof1ppmsolidsandamaximum
thermometer. In some cases, temperature of either the uninsu- of 0.2 ppm silica. If the water used for specimen wetting is
lated or insulated white panel thermometer may be used to above 1 ppm solids, the solids and silica levels must be
specify exposure conditions. The uninsulated or insulated reported. Recirculation of water used for specimen wetting is
white panel shall be constructed in the same way as the not recommended and if done the recirculated water shall meet
corresponding uninsulated or insulated black panel the specified purity requirements.
thermometer, except for use of a white coating with a good
NOTE 16—Distillation, or a combination of deionization and reverse
resistance to aging. The reflectance of the white coating
osmosis can effectively produce water with the desired purity.
between 450 and 800 nm shall be at least 60 % and at least
5.3.3 If specimens are found to have deposits or stains after
30 % between 800 and 1500 nm.
exposure, the water purity must be checked to determine if it
5.2.5 When requested, suppliers of insulated or uninsulated
meets the purity requirements described in 5.3.2. On some
black or white panels shall provide certification that the black
occasions,exposedspecimenscanbecontaminatedbydeposits
or white coating meets the reflectance requirements given in
from bacteria than can grow in the purified water used for
this practice.
specimen wetting. If bacterial contamination is detected, the
5.2.6 Exposure devices that control temperature of a black
entire system used for specimen wetting shall be flushed with
or white temperature sensor shall be able to maintain fluctua-
a chlorinating solution, such as sodium hypochlorite and
tions at the control point as specified in Annex A3.
thoroughly rinsed prior to resuming exposures.
5.2.7 Manufacturers of exposure devices shall assure that
5.3.4 Although it does not always correlate with silica
the temperature of a black or white panel temperature sensor
content, it is recommended that the conductivity of the water
placed anywhere within the specimen exposure area shall be
used for specimen wetting be monitored continuously and that
within 63 °C of the set point temperature for set points up to
exposures be stopped whenever the conductivity is above
70 °C and within 64 °C for set point temperatures above
5 µS⁄cm.
70 °C.
5.3.5 All components of the specimen wetting unit shall be
5.2.8 The test report shall indicate whether an insulated or
fabricated from stainless steel, plastic, or other material that
uninsulated black or white panel was used. If either type of
does not contaminate the water. If plastic materials are used,
black or white panel thermometer is not positioned in the
they shall not leach low molecular weight UV absorbing
specimen exposure area, the exact position used shall be
components into the water.
described in the test report.
5.3.6 In devices where humidity within the test chamber is
5.2.9 If chamber air temperature is measured, the tempera-
controlled, sensors used to determine humidity shall be placed
turesensingelementshallbeshieldedfromthelightsourceand
within the test chamber air flow and shielded from direct
water spray. Exposure devices, which control temperature of
radiation and water spray. When humidity is controlled, the
chamber air shall be able to maintain temperature of chamber
measured relative humidity shall be within 65 % of the set
air within 63 °C of the set point temperature.
point humidity.
5.2.10 Calibrate thermocouples according to instructions
5.3.6.1 Calibrate the sensors used to determine humidity
provided by the device manufacturer. If no instructions are
according to the device manufacturer’s instructions.
provided by the device manufacture, sheathed thermocouples
5.3.7 Any device intended to introduce wetting of
shall be calibrated according to Test Methods E839, and
specimens, for example, by spray or immersion, shall have
resistance thermometers used as the sensing element for black
means to program intervals with and without wetting.
or white panel thermometers shall be calibrated according to
Test Methods E644. Unless otherwise specified, devices used
NOTE 17—There is currently no generally accepted method for charac-
to measure temperature shall be calibrated at least annually. terizing the uniformity or consistency of specimen wetting.
Wherever possible, calibrations should be traceable to a
5.4 Other Apparatus Requirements—Although various ap-
nationally recognized standards agency.
paratus designs are used in practice, each apparatus shall
5.3 Humidity and Wetting: include the following:
5.4.1 Any device intended to provide light and dark cycles
5.3.1 The presence of moisture may have a significant effect
shall have means to program intervals with or without light.
on exposure tests. Any apparatus operated according to this
The time of each light and dark cycle shall be controlled to
standard, which attempts to simulate the effects of moisture,
within 610 % of the shortest cycle time used. It is preferable
shall have means for providing moisture to specimens using
one or more of the following methods: humidification of to use cycle timers that are accurate and reproducible as
possible. Optionally, means to provide a record of the length of
chamber air, formation of condensation, water spray, or im-
mersion. The type and rate of material degradation can be light and dark cycles may be provided.
affected significantly by the method used to provide moisture 5.4.2 To fulfill the requirements of particular test
stress. procedures, the apparatus also may need to provide means to
register or record the following operational parameters.
5.3.2 The purity of the water used for specimen wetting is
very important. Without proper treatment to remove cations, 5.4.2.1 Line voltage;
G151 − 19
5.4.2.2 Lamp voltage and where appropriate, lamp wattage; 6.2.3 When material properties are measured using destruc-
5.4.2.3 Lamp current; tive tests, a separate set of specimens is needed for each
5.4.2.4 Temperature of uninsulated or insulated black or exposure period. When destructive tests are used, the total
white panel thermometer; number of test specimens required will be determined by the
5.4.2.5 Test chamber air temperature; number of exposure periods used and whether unexposed file
5.4.2.6 Test chamber relative humidity; specimens are tested at the same time as exposed specimens.
5.4.2.7 Water spray cycles; 6.2.4 Control materials with known durability should be
5.4.2.8 Irradiance or radiant exposure, or both, over a included with each exposure test. It is recommended that
specified spectral region; and control materials known to have relatively poor and good
5.4.2.9 Duration of exposure (radiation time and total, if durability be used. Control materials are used for the purpose
different). of comparing the performance of the test materials to the
5.4.3 Follow the recommendations of the device manufac- controls.Beforelaboratorytolaboratorycomparisonsaremade
turer regarding calibration of devices used to record each it is necessary to establish agreed upon control materials. The
operational parameter. number of specimens of the control material should be the
same as that used for test materials.
6. Test Specimens
6.3 Storage and Conditioning:
6.3.1 Conditioning and handling of test, control, reference,
6.1 Form and Preparation:
and file specimens shall be according to Practice G147.
6.1.1 The dimensions of the test specimens normally are
6.3.2 If test specimens are cut or machined from larger
those specified in the appropriate test method for the property
pieces, they should be conditioned after machining according
orpropertiestobemeasuredafterexposure.Whenthebehavior
to Practice D618, Specification D3924, or Practice E171.In
of a specific type of article is to be determined, the article itself
some circumstances, it may be necessary to precondition the
should be exposed whenever possible.
sheets prior to cutting or machining to facilitate specimen
6.1.2 For some tests, specimens to be exposed may be cut
preparation. The properties of some materials are very sensi-
fromalargersheetorpartthatisformedbyextrusion,injection
tive to moisture content and the duration of conditioning may
molding, or other process. The exact shape and dimensions of
need to be longer than those specified in these standards,
the specimens to be exposed will be determined by the specific
particularly where specimens have been exposed to climatic
testprocedureusedformeasurementofthepropertyofinterest.
extremes.
The procedures used to machine or cut individual test speci-
mens from a larger sheet or part may affect the results of the
7. General Procedure
property measurement and the apparent durability. Therefore,
7.1 Mark each specimen that will be exposed with a unique
themethodusedforspecimenpreparationshallbeagreedupon
identifying number in accordance with Practice G147.
by the interested parties and should be related closely to the
7.1.1 Do not touch the surface of exposed specimens or
method normally used to process the material in typical
optical components with bare skin because oils that are
application.
deposited may act as UV absorbers or contain contaminants
6.1.3 Unless otherwise specified or required, do not cut
which accelerate degradation.
individual test specimens for property measurement from
larger specimens that have been exposed. The effects any 7.2 Specific conditions and procedures for the exposure test
cutting or machining operation may have on the properties of
depend on the type of device used and the material being
individual test specimens usually are much larger when the test tested. For open flame carbon-arc, enclosed carbon-arc, fluo-
specimens are cut from a large piece after exposure. This is
rescent UV, and xenon-arc exposures, these can be found in
especially true for materials that embrittle on exposure.
Practices G152, G153, G154, and G155 and in other standards,
6.1.3.1 When test specimens are cut from an exposed sheet
which reference these practices.
or larger part, they should be taken from an area that is at least 7.2.1 For each exposure test, specific set points for impor-
20 mm from the fixture holding the material or from the
tant parameters such as irradiance, temperature, and humidity
exposed specimen edges. In no circumstances shall any mate-
are used. Typically, these parameters are measured and con-
rialfromtheexposedfaceberemovedduringthetestspecimen
trolled at a single position within the chamber. During normal
preparation.
operation, there is an allowable departure of the measured
6.1.4 When comparing materials in an exposure test, use
value from the set point. AnnexA3 provides detailed informa-
test specimens that are similar in dimensions and exposed area.
tion about the maximum allowable departure of the measured
value from the set point.
6.2 Number of Test Specimens:
7.2.2 Asingle point measurement does not mean conditions
6.2.1 The number of test specimens for each test condition
throughout the cabinet are the same. It does not mean two tests
orexposureperiodshallbethatspecifiedintheappropriatetest
run in similar cabinets will produce the same results. Cabinets
method for the property or properties to be measured after
thatcontroltemperaturebytheblackpanelwillnotproducethe
exposure.
same test as cabinets that control by air temperature.
6.2.2 Unless otherwise specified or required, use at least
three replicate specimens where properties are measured using 7.3 Select material properties that exhibit a significant
nondestructive tests and six replicate specimens where prop- change during the exposure period in order to provide weath-
erties are measured using destructive tests. ering performance discrimination among a series of materials.
G151 − 19
7.4 Follow the procedures described in the appropriate time in an exposure conducted according to this practice and
standard for measuring the properties of test specimens before time in an outdoor environment because they can give errone-
and after exposure. ous information. The acceleration factor is material dependent
and is only valid if it is based on data from a sufficient number
7.5 If nondestructive tests are used to measure properties of
of separate exterior and laboratory accelerated exposures so
the materials being tested, measure the properties of specimens
that results used to relate times to failure in each exposure can
before beginning the exposure.After each exposure increment,
be analyzed using statistical methods.
measure the same property that is measured initially on the
specimens. Take care to make the property measurement in the
NOTE20—Anexampleofastatisticalanalysisusingmultiplelaboratory
same position used for the initial measurement. and exterior exposures to calculate an acceleration factor is described by
J. A. Simms (1).
NOTE 18—To monitor the response of the instrument used to measure
8.3 After each exposure increment, evaluate or rate changes
the desired property, one can measure a calibration standard each time the
instrument is used. in exposed test specimens according to applicable ASTM test
methods.
7.6 If destructive tests are used to measure properties of the
materials being tested, prepare a separate set of test specimens
8.4 When results from exposures conducted according to
for each exposure period. Compare the value of the property
this practice are used in specifications, one of the following
afterexposuretothepropertymeasuredonanunexposedsetof
three criteria must be met.
specimens measured prior to beginning the exposure.
8.4.1 If a standard or specification for general use requires a
Alternatively,thepropertycanbemeasuredonaseparatesetof
definite property level after a specific time or radiant exposure
unexposed file specimens at the same time as the property of
in an exposure test conducted according to this practice, base
exposed specimens is measured. The results for the unexposed
the specified property level on results from round-robin experi-
file specimens and from the exposed specimens can then be
ments run to determine the test reproducibility from the
compared.
exposureandpropertymeasurementprocedures.Conductthese
round-robins according to Practice E691, and include a statis-
NOTE 19—Procedures and formulas for calculating the change in
material property of test materials and reference materials after exposure
tically representative sample of all laboratories or organiza-
can be found in Practice D5870.
tions who would normally conduct the exposure and property
7.7 Some materials will change color during storage in the measurement.
dark, particularly after weathering. It is essential that color 8.4.2 If a standard or specification for use between two or
measurement or visual comparisons be carried out as soon as
three parties requires a definite property level after a specific
possible after exposure once the exposed surface has dried. time or radiant exposure in an exposure test conducted accord-
ing to this practice, base the specified property level on two
8. Periods of Exposure and Evaluation of Test Results independent experiments run in each laboratory to determine
the reproducibility for the exposure and property measurement
8.1 In most cases, periodic evaluation of test and control
process.The reproducibility of the exposure/property measure-
materials is necessary to determine the variation in magnitude
ment process is then used to determine the minimum level of
anddirectionofpropertychangeasafunctionofexposuretime
property after the exposure that is mutually agreeable to all
or radiant exposure.
parties.
8.2 The time or radiant exposure necessary to produce a
8.4.3 When reproducibility in results from an exposure test
defined change in a material property can be used to evaluate
conducted according to this practice has not been established
or rank the stability of materials.This method is preferred over
through round-robin testing, specify performance requirements
evaluating materials after an arbitrary exposure time or radiant
for materials in terms of comparison (ranked) to a control
exposure.
material.All specimens shall be exposed simultaneously in the
8.2.1 Exposure to an arbitrary time or radiant exposure may
same device. All concerned parties must agree on the specific
be used for the purpose of a specific test if agreed upon by the
control material used.
parties concerned or if required for conformance to a particular
8.4.3.1 Conduct analysis of variance to determine whether
specification. When a single exposure period is used, select a
anydifferencesbetweentestmaterialsandcontrolmaterialsare
time or radiant exposure that will produce the largest perfor-
statistically significant. Expose replicates of the test specimen
mance differences between the test materials or between the
and the control specimen so that statistically significant per-
test material and the control material.
formance differences can be determined.
8.2.2 The minimum exposure time used shall be that nec-
NOTE 21—Fischer and Ketola illustrate (4) use of rank comparison
essary to produce a substantial change in the property of
between test and control materials in specifications.
interest for the least stable material being evaluated. An
NOTE 22—Guide G169 includes examples showing use of analysis of
exposure time that produces a significant change in one type of
variance to compare materials.
material cannot be assumed to be applicable to other types of
materials.
9. Test Report
8.2.3 The relation between time to failure in an exposure
9.1 Report the following information:
conducted according to this practice and service life in an
9.1.1 Specimen description;
outdoor environment requires determination of a valid accel-
eration factor. Do not use arbitrary acceleration factors relating 9.1.1.1 Afull description of the specimens and their origin;
G151 − 19
9.1.1.2 Compound details, cure time, and temperature 9.1.2.11 Time of each light and dark period;
where appropriate; and 9.1.2.12 Setpointforwhitepaneltemperature,ifapplicable;
9.1.1.3 Complete description of the method used for prepa-
and
ration of test specimens. 9.1.2.13 Set point for chamber air temperature, if appli-
cable.
NOTE 23—If exposure tests are conducted by a contracting agency,
9.1.2.14 Description of method used to mount specimens in
specimens usually are identified by code number. In such cases, it is the
responsibility of the originating laboratory to provide the complete exposureframe,includingadescriptionofanymaterialusedas
specimen description when reporting results of the exposure test.
backing for test specimens.
9.1.2.15 Description for test specimen repositioning, if
9.1.2 Description of Exposure Test—Description of the
used.
exposure device and light source including:
9.1.2.1 Type of device and light source; 9.1.2.16 Description of the radiometers used for measuring
light dosage, if used.
9.1.2.2 Description of the filters used;
9.1.2.3 If required, set point for irradiance at the specimen 9.1.3 Test Results:
surface, including the bandpass in which the radiation was 9.1.3.1 Complete description of the test procedure used for
measured; and measurement of any properties reported including reference to
9.1.2.4 If required, wattage used for laboratory light source.
applicable ASTM or other standards.
9.1.2.5 Type of black or white panel thermometer, or both, 9.1.3.2 Results from property measurement on test speci-
if used. Describe how the black or white panel thermometer is
mens;
mounted in the specimen exposure area, including whether the
9.1.3.3 Results from property measurement on control
black or white panel thermometer was mounted on a solid
specimens;
surface or with
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