Terminology and Definitions
accelerated outdoor weathering
(terms in brackets should not be used)
→ weathering, accelerated outdoor
for the purpose of weathering, the wavelength range of electromagnetic radiation that is capable of causing a photochemical reaction
description of the spectral efficiency of radiation to produce a particular polymer response (specific property change of a specific polymer) plotted as a function of the wavelength of radiation
NOTE: data of an action spectrum are specific to the polymer but independent from the radiation source, also named spectral sensitivity
an information on the relative spectral effects (specific property change of a specific polymer) of a radiation source to which the material is exposed
NOTE: Data of an activation spectrum are specific to the polymer, the specific polymer property and to this radiation source
entirety of all irreversible chemical and physical processes occurring in a material in the course of time
the ratio of reflected to incident global solar radiation of a surface. It depends on the optical properties of the surface, in particular on the variation of spectral reflectance.
environmental conditions corresponding to the usual atmospheric conditions in laboratories with uncontrolled temperature and humidity.
NOTE: The phrase "at ambient temperature" refers to an environment the air temperature of which lies within a specified range, no consideration being given to relative humidity, atmospheric pressure or air-circulation velocity. In general, the air-temperature range extends from 18 °C to 28 °C and is stated as "at an ambient temperature of 18 °C to 28 °C".
→ weathering, artificial accelerated
→ irradiation, artificial accelerated
azimuth, azimuthal angle
angle in the horizontal plane measured clockwise from the reference direction "north" on the horizon
NOTE: Solar azimuth is the angle between "north" and the vertical projection of the direction of the sun. Specimen azimuth is the angle between "north" and the vertical projection of the surface normal.
specimens are attached to a solid backing for exposure. When this exposure is used, the backing material may be e.g. a sheet of plywood. The thickness of the backing and type of coating used shall be agreed upon by all interested parties. The backing increases the specimen temperature and decreases the relative humidity near the exposed surface
black standard thermometer,
insulated black panel thermometer
is a temperature measuring device consisting of a stainless-steel plate, having a black coating which absorbs at least 90 % of the incident radiation flux below λ = 2500 nm, that shall be attached to a 5 mm thick baseplate made of a weather resistant polymer.
NOTE: The black standard thermometer is used to determine the maximum surface temperature of polymer specimens exposed to radiation and to control the temperature in artificial weathering devices.
black panel thermometer
is a temperature measuring device consisting of a stainless-steel plate, having a black coating which absorbs at least 90 % of the incident radiation flux below λ = 2500 nm. The back of the metal panel shall be open to the atmosphere.
NOTE: The black panel thermometer is used to determine the maximum surface temperature of coated metal panels exposed to radiation and to control the temperature in artificial weathering devices.
centre wavelength (CW)
there are a number of different climates in which plastics may be used. Climates are generally divided into six basic types and into several types in each class. ISO 877-1 provides a description of a commonly used climate classification system. Significant differences in rate and/or type of degradation may be expected when plastics are exposed in the different climate types. Mostly the fastest photodegradation of plastics takes place by exposure in hot/wet and hot/dry climates with high levels of solar radiation.
one or more operations intended to bring a sample or test specimen into a state of equilibrium with regard to temperature and humidity
constant atmosphere with regard to temperature and humidity in which a sample or test specimen is kept before being subjected to a test
in weathering a material which is of similar or the same composition and construction to the test material used for comparison, exposed at the same time.
NOTE: 1 A reference material can often be used as the control.
NOTE 2: Out of date term for "file specimen"
NOTE 3: Out of date term for "masked area"
a radiation-transferring device that samples irradiance according to the cosine of the angle of incidence and that collects all radiation incident in 2π steradians (i.e. in a hemisphere) using, for example, an integrating sphere or a plane diffuser
as partly used in weathering, is a term equivalent to "global solar radiation" and refers to the full spectrum, that is, ultraviolet through infrared.
NOTE: generally, the term "light" means the visible part of a spectrum.
a photoreceptor that converts incident radiation into an electrical signal for the purpose of determining the irradiance of the radiation
diffuse radiation, diffuse solar radiation
for the purposes of weathering, it is the radiation on a horizontal surface received from the whole hemisphere (2π sr) excluding the small solid angle of direct solar radiation. For inclined surfaces, also reflected radiation has to be considered, see albedo.
Cf. radiation, global solar
direct normal solar radiation
is the direct solar radiation received on a plane being normal (perpendicular) to the solar beam.
NOTE: The direct normal solar radiation is measured with a → pyrheliometer
direct solar radiation, direct radiation, direct (beam) radiation
for the purposes of weathering, it is the solar radiation received from a solid angle with an open angle of 5° to 6° centered on the sun's disk.
Cf. radiation, global solar
out of date term for exposure of a material to outdoor climatic conditions
→ weathering, natural
in weathering, the ability of a polymer to resist the action of weathering exposure
in weathering the act of subjecting the test specimen to the action of outdoor or artificial climatic conditions
the tilt of the test specimen surface from horizontal which is equal to the zenith angle of the surface normal.
field of view
the full angle of the cone that is defined by the center of the receiver surface and the border of the limiting aperture
portion of the material to be tested which is stored under conditionse.g. at ambient temperature in the dark, in which it is probably stable; it is used for comparison between exposed and unexposed state
a device which reduces the spectral range (cut-on, bandpass, and interference filter) or radiation flux of a radiation source.
a filter that transmits wavelengths longer than the cut-on wavelength, while rejecting shorter wavelengths, and characterized by a sharp transition from minimum to maximum transmittance
a filter that transmits wavelengths shorter than the cut-off wavelength, while rejecting longer wavelengths, and characterized by a sharp transition from maximum to minimum transmittance
a lamp that contains an inert gas (krypton or argon) at low pressure and a small amount of mercury. An electric discharge between two electrodes excites the atoms of mercury, causing electrons in the mercury atoms to absorb energy and then release it in the form of UV radiation, especially at λ = 254 nm. This UV radiation excites molecules from the phosphor on the inside of the tube which "fluoresce", producing radiation with longer wavelengths. The emission spectrum depends on the type of phosphor and the transmittance of the glass tube.
fluorescent UV lamp
a fluorescent lamp with a phosphor that emits mainly UV radiation
flux of radiation
Fresnel-reflecting solar concentrator
a Fresnel type parabolic cylinder mirror with up to 10 flat mirrors arranged
such that they reflect the direct solar radiation onto one target, which has the same shape and size of one flat mirror.
global solar radiation
→ radiation, global solar
global solar irradiance Eglob
→ irradiance, global solar
ratio of the amount of water vapor actually in the air compared to the amount of water vapor required for saturation at that particular temperature and pressure. It is expressed as a percentage.
infrared, IR radiation
→ radiation, infrared
an optical filter that defines the spectral composition of the transmitted radiation by the effects of interference
NOTE: Most interference filters consist of thin layers of metals and dielectrics, resulting in high transmittance over selected spectral bands.
the radiant flux per unit area incident on a surface, measured in watts per square metre (W/m2
irradiance, global solar, Eglob
the direct and diffuse radiant flux from the sun, incident on a horizontal plane of unit area within a solid angle of 2π steradians, measured in watts per square metre (W/m2
irradiance, spectral Eeλ
per wavelength interval in nanometre, typically reported in
NOTE: The term "spectral power distribution" is a general term used to describe the relative spectral irradiance or the relative spectral emission of a source.
irradiation, artificial accelerated
exposure of a material to a laboratory radiation source meant to simulate window glass filtered solar radiation or radiation from interior lighting sources and where specimens may be subjected to relatively small changes in temperature and relative humidity in an attempt to more rapidly produce the same changes that occur when the material is used in an indoor environment.
NOTE 1: This term shall also be used in the cases where specimens are exposed to radiation with other cut-on wavelengths without any wetting.
NOTE 2: These exposures have been commonly referred to as fading or lightfastness tests.
exposure of a material to glass-filtered global solar radiation at indoor climatic conditions
→ radiation, visible
→ filter, long pass
a portion of the exposed specimen surface which is protected from exposure to radiaton by masking. (See also control.)
NOTE: The masked area is not protected from heat and moisture.
metal halide lamps
metal halide lamps are a type of mercury arc lamp in which the spectral output is modified by the addition of metal halides. Depending upon the selection of dopants, the spectrum can be enhanced in the UV or visible ranges. These lamps can have improved colour appearance, rendering properties, and luminous efficacy compared to standard mercury arc lamps.
→ irradiation, natural
→ weathering, natural
open flame carbon arc, sunshine carbon arc
a radiation source in which an arc is produced across a pair of copper coated carbon rods filled with rare earth elements intended to produce a specific spectral emission of radiation. The carbons are open to the atmosphere and may be surrounded by a glass lantern arrangement which acts to modify the spectral irradiance received by the specimens.
→ filter, optical
in a bandpass filter or in a radiometer, the wavelength interval between cut-on and cut-off of transmittance or spectral response, respectively.
centre wavelength (CW)
the wavelength located at the midpoint of the FWHM interval
the wavelength at which the transmittance has decreased to 5 % of the peak transmittance when the transition is from the peak transmittance to the long-wavelength blocking region
the wavelength at which the transmittance has increased to 5 % of peak transmittance when the transition is from the short-wavelength blocking region to the transmitting region
a relative term generally applied to radiometers that have selective filters with specific cut-on and cut-off wavelengths and that have an FWHM between 20 nm and 70 nm that typically measure in the 300 nm - 400 nm wavelength band
a relative term which applies to interference filters with an FWHM of no more than 20 nm. In narrow-band filters of the same type, the reproducibility of the centre wavelength and the FWHM should be within ±2 nm
a relative term which applies to filters for which the full width at half maximum is at least 70 nm and typically describes a filter radiometer having a wide passband of, for example, 300 nm to 800 nm
the wavelength at maximum transmittance. Not necessarily the same as the centre wavelength
photochemicaIly induced ageing
an instrument for measuring relative humidity. It consists of two thermometers:
one is an usual dry-bulb thermometer and the other includes a bulb that is kept wet to measure the wet-bulb temperature. Evaporation from the wet bulb lowers the measured temperature. The difference of the temperatures is a measure of the relative humidity.
a radiometer used to measure global solar irradiance (or, if inclined, hemispherical solar irradiance)
a radiometer used to measure the → direct normal solar irradiance on a surface
NOTE: pyrheliometers measure the component of solar radiation that is the beam between an instrument, and the sun within a solid conical angle centered on the sun's disk and having a total full opening view angle of 5° to 6º.
an instrument for measuring electromagnetic radiation, consisting of a detector and a signal-processing device
a radiometer for measuring the irradiance in the wavelength interval from about 300 nm to 400 nm
a radiometer for measuring spectral irradiance in narrow-wavelength intervals over a given spectral region as a function of wavelength.
an instrument deployed in the field or laboratory used for the routine measurement of radiation, with a calibration traceable to a recognized standard scale, through transfer of the scale by comparison, substitution, or other direct relationship with a reference radiometer
an instrument used to realize a standard measurement value with respect to a recognized radiation scale (e.g., World Radiation Reference, spectral irradiance scale), with a stated path of traceability to recognized standards, and measurement uncertainty. Used only to calibrate other radiometers by comparison, substitution, or other direct relationship
radiant exposure He
the time integral of irradiance, measured in joules per square metre (J/m2
a flux of energy in the form of electromagnetic waves or of particles (photons)
the spectral range of radiation with wavelengths from 800 nm to about 1 mm
the spectral range of radiation with wavelengths ≤ 400 nm
the spectral range of radiation with wavelengths from 400 nm to 800 nm
radiation, global solar
direct plus diffuse solar radiation (radiant flux) in a wavelength range from
295 nm to about 4000 nm, received on a horizontal plane from a solid angle
of 2π sr.
→ direct solar radiation, diffuse solar radiation
NOTE 1: Mostly, the term global solar radiation is used in terms of radiant exposure, but sometimes also in terms of irradiance.
NOTE 2: The direct amount of global solar radiation is the direct solar radiation on a horizontal plane. The diffuse amount of global solar radiation is the diffuse solar radiation on a horizontal plane.
a material with known performance.
a portion of the reference material that is to be exposed.
→ humidity, relative
small portion of a material or group of units taken from a larger quantity of material or collection of units, intended to be representative of the whole.
→ filter, short pass
→ irradiance, spectral
(spectral power distribution, SPD) a qualitative spectral characterization of a radiation source
→ irradiance, spectral
→ radiometer, spectro-
preferred constant atmosphere for which specific air temperature and humidity values, as well as limit ranges for atmospheric pressure and air-circulation velocity, are specified, the air not having any significant additional constituents and the atmosphere not being subject to any significant additional radiation influences
NOTE 1: Standard atmospheres permit a defined state to be attained and maintained for samples or specimens.
NOTE 2: Standard atmospheres correspond to the average atmospheric conditions in laboratories and can be established in conditioning (controlled atmosphere) cabinets, chambers or rooms.
standard weathering reference material (SWRM)
a Weathering Reference Material (WRM) whose weIl documented weathering degradation properties have been certified by a recognized standards agency or group and which are identical when exposed to identical test conditions.
a specific portion of the samples upon which the testing is to be performed.
entirety of all deleterious chemical and physical modifications of a plastic at elevated temperature
NOTE: It is essential to report the temperature and other environmental conditions at which the phenomenon is studied.
property of a material to resist degradation under the action of heat
NOTE: It is determined by arbitrary test methods based on change in colour, electrical or mechanical properties, or by loss of mass.
→ exposure angle
the total period of time that a surface is wet, typically reported in hours
NOTE: The time a specific surface remains wet depends on the type of polymer, the specimen thickness, the backing and on its tilt angle.
concerning transparent or translucent materials: the ratio of transmitted radiation flux to incident radiation flux under specified geometric and spectral conditions, expressed either as a percentage or a decimal fraction
the transmittance of a material as a function of wavelength of radiation
→ radiation, ultraviolet
specimens are attached to the test rack or to a frame in such a manner that there is free flow of air against the front and back of the specimen. In these exposures, specimens are subjected to the effects of weather on all sides.
→ radiation, visible
weathering, artificial accelerated
exposure of a material in a laboratory weathering device to conditions which may be cyclic and intensified over those encountered in outdoor or in-service exposure. This involves a laboratory radiation source, heat, and moisture (in the form of relative humidity, and/or water spray, condensation, or immersion) in an attempt to more rapidly produce the same changes that occur in long term outdoor exposure.
NOTE: The device may include means for control and/or monitoring the radiation source and other weathering variables. It may also include exposure to special conditions, such as acid spray to simulate the effect of industrial gases.
exposure of a material to global solar radiation at outdoor climatic conditions
(weathering behind glass
out of date terms for exposure of a material to glass-filtered global solar radiation at indoor climatic conditions
see natural irradiation
weathering, accelerated outdoor
intensified outdoor weathering
outdoor weathering using the sun as radiation source, and where the rate of photodegradation is accelerated over that of the in-service exposure position increasing one or more of the influencing parameters, e.g. the irradiance level by the use of Fresnel-reflecting concentrators or the temperature by exposing in black boxes
weathering reference material (WRM)
a reference material having well documented and repeatable degradation properties when exposed to identical test conditions.
NOTE: a WRM is used to monitor exposures in order to establish consistency among tests run under nominally the same conditions. Some WRMs are also used to define periods of exposure. A WRM is not used for performance comparison with the test material. A control material is used for the latter purpose.
a process of generating liquid water on an exposed surface by water spray, by water flood or by condensation.
White standard thermometer
It shall be constructed in the same way as the → black standard thermometer, except for use of a white coating with a good resistance to ageing. The reflectance of the white coating between 400 nm and 1000 nm shall be at least 80 %, and at least 60 % between 1000 nm and 1500 nm.
White panel thermometer
It shall be constructed in the same way as the → black panel thermometer, except for use of a white coating with a good resistance to ageing. The reflectance of the white coating between 400 nm and 1000 nm shall be at least 80 %, and at least 60 % between 1000 nm and 1500 nm.
xenon arc lamp
lamp that is based on electric discharge in a xenon gas in a quartz tube to produce radiation. When the voltage between the two electrodes is large enough, the gas becomes ionized and begins to conduct electricity. Electrons bridging the gap excite electrons in the gas atoms to higher energy states. This energy is released as radiation when the atoms return to ground state. This type of lamp emits much more evenly throughout the entire range of solar radiation than other lamps.
the angle between the local vertical and any other direction