© ISO 2013 Paints and varnishes — Methods of exposure to laboratory light sources — Part 1 General guidance Peintures et vernis — Méthodes d’exposition à des sources lumineuses de laboratoire — Partie[.]
General
Samples for testing are subjected to laboratory light sources in a controlled environment The outlined methods detail the necessary requirements for measuring irradiance and radiant exposure on the specimen's surface, as well as monitoring the temperatures of designated white and black sensors, the air temperature within the chamber, and the relative humidity levels.
Significance
When performing exposures with laboratory light sources, it is crucial to evaluate how effectively the accelerated-test conditions replicate the real-world environment for the paint or varnish under examination Additionally, it is vital to account for the variability present in both the accelerated tests and actual exposures when designing exposure experiments and analyzing results from artificial accelerated weathering or irradiation tests.
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No laboratory exposure test can fully replicate actual-use conditions Results from artificial accelerated weathering or irradiation can only be deemed representative of real-world exposures if a rank correlation is established for the specific materials and if the degradation mechanisms are identical The durability of materials can vary significantly across different locations due to factors such as solar radiation, wetness duration, humidity, temperature, and pollutants Consequently, while exposure test results may aid in comparing material durability in a specific environment, they should not be assumed to apply to different environments.
Assigning a universal "general acceleration factor" to all materials based on a specific duration of radiant exposure in artificial accelerated weathering is invalid This is due to several reasons: first, acceleration factors are material-dependent and can vary significantly between different materials and formulations Second, the degradation rates in both actual-use and artificial conditions can greatly influence the calculated acceleration factor Lastly, factors derived from the irradiance ratio between laboratory light sources and solar radiation fail to account for temperature, moisture, and differences in spectral power distribution.
Acceleration factors for a specific material formulation are only valid when derived from a substantial number of distinct outdoor or indoor environmental tests, as well as artificial accelerated weathering or irradiation exposures These results must be analyzed using statistical methods to effectively relate times to failure across different exposures An example of such statistical analysis, which utilizes multiple laboratory and real-world exposures to determine an acceleration factor, is provided by J.A Simms [1].
Several factors can reduce the correlation between accelerated tests using laboratory light sources and real-world exposures These include differences in spectral irradiance between laboratory light and solar radiation, higher irradiance levels than those encountered in actual use, and continuous light exposure without dark periods Additionally, specimen temperatures may exceed those in real conditions, and exposure conditions might create unrealistic temperature differences between light- and dark-colored specimens Frequent cycling between high and low temperatures or unrealistic thermal shock can also affect results Furthermore, moisture levels in accelerated tests may not reflect actual-use conditions, and the absence of biological agents, pollutants, or acidic precipitation can lead to discrepancies.
Use of accelerated tests with laboratory light sources
Results from artificial accelerated weathering or irradiation tests, conducted per this International Standard, are most effective for comparing the relative performance of materials Such comparisons are valid only when materials are tested simultaneously in the same exposure device The results can be quantified by comparing the exposure time or radiant exposure required to diminish a characteristic property to a specified level, often used to ensure that the quality of different batches aligns with a control of known performance.
It is essential to include at least one control in each test to effectively compare the performance of the test materials The control should have a similar composition and construction, ensuring that its failure modes align with those of the tested material Ideally, two controls should be utilized: one exhibiting good durability and the other demonstrating poor durability.
To ensure accurate statistical evaluation of results, it is essential to have sufficient replicates for each control and test material A minimum of three replicates should be used for all test and control materials unless stated otherwise Additionally, when conducting destructive tests to measure material properties, a distinct set of specimens must be utilized for each exposure period.
In certain specification tests, test materials are simultaneously exposed alongside a weathering reference material, such as blue wool test fabric The properties of the test material are assessed once a defined property of the reference material reaches a specific threshold However, if the reference material's composition differs from that of the test material, it may not respond to exposure stresses that cause failure in the test material, or it may react sensitively to stresses that have minimal impact on the test material Consequently, the variability in results between the reference and test materials can differ significantly, leading to potentially misleading outcomes when the reference material is utilized as a control or to establish the duration of the exposure period.
NOTE 1 Definitions of control and reference materials that are appropriate to weathering tests are given in Clause 3.
Weathering reference materials are essential for monitoring the consistency of operating conditions in exposure tests For detailed guidance on selecting and characterizing these materials, refer to ASTM G 156 Additionally, ISO/TR 19032 outlines a method that utilizes the change in the carbonyl index of a specific polyethylene weathering reference material to assess conditions during both natural and artificial accelerated weathering exposures.
In certain specification tests, the properties of test specimens are assessed following a defined exposure time or radiant exposure under specific conditions It is important to note that results from any accelerated exposure test conducted according to this International Standard should not be used to determine a "pass/fail" status for materials based solely on the level of a specific property after a given exposure time or radiant exposure, unless the reproducibility of the effects from the exposure cycle and the property measurement method has been validated.
5 Requirements for laboratory exposure devices
Laboratory exposure devices shall be equipped with facilities to provide specimens with irradiance (5.1), temperature (5.2), humidity and wetting (5.3).
Irradiance
Laboratory light sources are essential for delivering irradiance to test specimens According to ISO 16474-2, a xenon-arc lamp is utilized for this purpose, while ISO 16474-3 specifies the use of a fluorescent UV lamp, and ISO 16474-4 employs an open-flame carbon-arc lamp.
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5.1.2 The exposure device shall provide for placement of specimens and any designated sensing devices in positions that allow uniform irradiance from the light source.
The spectral irradiance generated by an artificial accelerated weathering device is crucial, as it should closely resemble solar radiation, particularly in the short-wavelength UV region Annex C offers a benchmark solar spectrum for comparing the device's spectral irradiance to that of solar radiation Additionally, later sections of this International Standard outline specific requirements for the relative spectral irradiance produced by the described devices.
Exposure devices must ensure that the irradiance at any point within the specimen exposure area is no less than 70% of the maximum irradiance recorded in that area For detailed procedures on measuring irradiance uniformity, manufacturers should refer to Annex A.
Irradiance uniformity in exposure devices is influenced by various factors, including deposits on the optical system and chamber walls Additionally, the type and quantity of specimens being exposed can impact this uniformity It's important to note that the irradiance uniformity guaranteed by the manufacturer applies only to new equipment under specific measuring conditions.
To minimize variability in exposure stresses during the specimen exposure period, it is advisable to periodically reposition the specimens based on the material's sensitivity If the irradiance at any position within the exposure area falls between 70% and 90% of the maximum irradiance, repositioning the specimens is essential to ensure consistent radiant exposure.
NOTE Random placement of replicate specimens is also good practice to reduce the effect of any variability in the conditions within the exposure area.
5.1.5 Follow the device manufacturer’s instructions for lamp and filter replacement and for pre-ageing of lamps and/or filters.
A radiometer that meets ISO 9370 standards can effectively measure irradiance (E) or spectral irradiance (E λ), as well as radiant exposure (H) or spectral radiant exposure (H λ) on the surface plane of the specimen.
The radiometer must be installed to measure the same radiation as the specimen surface If it is not aligned with the specimen plane, it should have a wide field of view and be calibrated for irradiance at the distance from the specimen.
The field radiometer must be calibrated in the emission region of the light source with a reference radiometer Calibration should utilize a light source filter combination identical to that used in testing, or an appropriate spectral mismatch factor must be considered Additionally, calibration checks must follow the manufacturer's instructions for the radiation measuring instrument.
Fluorescent UV lamps require that field radiometers be calibrated using lamps with a spectral power distribution identical to the testing lamps For definitions of field and reference radiometers, please refer to ISO 9370.
When measuring irradiance, it is essential to report the values within the agreed-upon wavelength range Certain devices are designed to measure irradiance either across specific ranges, such as 300 nm to 400 nm or 300 nm to 800 nm, or within a narrow pass-band centered on a single wavelength, like 340 nm.
Temperature
The surface temperature of materials exposed to radiation is influenced by factors such as radiation absorption, emissivity, thermal conduction, and heat transfer with the surrounding air or specimen holder Due to the impracticality of monitoring individual test specimens, a designated black surface sensor is employed to measure and regulate the temperature within the exposure chamber This sensor is strategically positioned in the specimen exposure area to ensure it receives identical radiation and cooling conditions as a flat test panel surface.
5.2.2 Two types of black surface temperature sensor may be used: a black-standard thermometer (BST) and a black-panel thermometer (BPT).
Black-standard thermometers are constructed from a flat stainless-steel plate, typically measuring 70 mm by 40 mm and having a thickness between 0.5 mm and 1.2 mm The side of the plate facing the light source is coated with a durable black layer that reflects no more than 10% of incident flux up to 2,500 nm A platinum resistance sensor, which is thermally sensitive, is securely attached to the center of the plate on the side opposite the radiation source, ensuring optimal thermal contact.
The baseplate must be 5 mm thick and made of unfilled poly(vinylidene fluoride) (PVDF), featuring a machined recess to accommodate a platinum resistance sensor positioned approximately 1 mm away The dimensions of the PVDF plate should ensure no metal-to-metal thermal contact occurs between the black-coated metal plate and its mounting holder, with metal mounts at least 4 mm from the plate edges Alternative black-standard thermometers are acceptable if they maintain a temperature reading within ± 1.0 °C of the specified design across all steady-state conditions and reach steady-state within 10% of the time required by the specified thermometer.
NOTE Black-standard thermometers are sometimes referred to as insulated black-panel thermometers.
Black-panel thermometers feature a corrosion-resistant flat metal plate, typically measuring 150 mm in length, 70 mm in width, and 1 mm in thickness The side facing the light source is coated with a durable black layer that reflects no more than 10% of incident flux up to 2,500 nm A thermally sensitive element, such as a black-coated stem-type bimetallic dial sensor, resistance-based sensor, thermistor, or thermocouple, is securely attached to the center of the exposed surface Additionally, the back of the metal panel is open to the atmosphere.
NOTE Black-panel thermometers are sometimes referred to as uninsulated black-panel thermometers.
Unless specified otherwise, temperature measurements must be taken using the thermometer designs outlined previously If alternative methods are employed to measure the temperature of black or white panels, the specific construction details of these panels must be included in the test report.
The temperature readings from black-panel and black-standard thermometers are influenced by the irradiance from the laboratory light source, as well as the temperature and airflow in the exposure chamber Typically, black-panel temperatures reflect those of dark-coated metal panels without rear thermal insulation, while black-standard thermometer readings correspond to the surface temperatures of dark samples with low thermal conductivity Under standard exposure conditions, black-standard thermometer readings are generally 3 °C to 12 °C higher than those from black-panel thermometers It is advisable to determine the specific temperature difference for each exposure scenario, as black-standard thermometers, being insulated, have a slightly slower response time to temperature changes compared to black-panel thermometers.
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At low irradiance levels, the temperature readings from black-panel or black-standard thermometers may closely align with the actual temperature of the specimen When utilizing light sources that emit minimal infrared radiation, the temperature differences between various black panels or between light and dark-colored specimens tend to be negligible.
To accurately assess the surface temperatures of exposed specimens and effectively manage the irradiance in the exposure chamber, it is advisable to utilize both a white-panel thermometer and a black-panel thermometer The white-panel thermometer should be constructed similarly to the black-panel version, but with a durable white coating This coating must exhibit a reflectance of at least 60% within the 450 nm to 800 nm range and a minimum of 30% from 800 nm to 1500 nm.
Manufacturers of exposure devices must ensure that their products comply with the requirements outlined in ISO 16474, specifically regarding the control of temperature for black or white temperature sensors at their intended operating positions These requirements are applicable under equilibrium conditions, as detailed in Table 1.
Table 1 — Requirements for set-point temperature of the black or white temperature sensor at the position where it is intended to operate
Set-point temperature Allowable deviation of the sensor temperature at the position in which sensor operates
Manufacturers of exposure devices must ensure that their products comply with the specifications outlined in ISO 16474, particularly regarding the temperature control of black or white temperature sensors within the designated exposure area These requirements are applicable under equilibrium conditions, as detailed in Table 2.
Table 2 — Requirements for set-point temperature of the black or white temperature sensor at any position within the allowed exposure area
Set-point temperature Allowable deviation of the sensor temperature when sensor placed anywhere in the exposure area
Variations in degradation rates may arise among materials in devices operating within permissible temperature limits To minimize the impact of temperature discrepancies in the exposure area, it is advisable to periodically reposition specimens or randomly arrange replicate specimens during testing.
5.2.8 The test report shall indicate whether a black-standard or black-panel thermometer was used and whether a white-standard or white panel thermometer was used.
NOTE Different temperatures may be indicated by a single type of black-standard or black-panel thermometer, depending on the specific design of the device supplied by different manufacturers.
When measuring the air temperature in an exposure chamber, it is essential to shield the temperature-sensing element from light sources and water spray, as the temperature at this location may differ from that near the exposed specimens Manufacturers must ensure that their temperature control devices maintain the chamber air temperature within ± 3 °C of the set point for temperatures up to 70 °C, and within ± 4 °C for temperatures exceeding 70 °C.
5.2.10 Calibrate the temperature sensor used to measure the chamber air temperature in accordance with the sensor manufacturer’s instructions at least annually.
Humidity and wetting
Moisture on the specimen's surface, especially during prolonged wet periods and cycles of wet and dry conditions, can greatly influence accelerated laboratory exposure tests Devices adhering to this International Standard must incorporate methods to supply moisture to specimens, which can include humidifying the chamber air, creating condensation, applying water spray, or immersing the specimens in water.
5.3.2.1 Water purity for xenon lamp and carbon arc instruments
The purity of water used for spraying specimens is crucial to prevent the development of spots or stains that can occur without proper treatment It is essential that the water contains a maximum solids content of 1 µg/g and a maximum silica content of 0.2 µg/g To achieve the desired purity, methods such as distillation or a combination of deionization and reverse osmosis are recommended If the water exceeds the specified solids content, the levels of solids and silica must be reported Additionally, recirculating water for specimen spray is not advisable unless it meets the established purity standards.
5.3.2.2 Water purity for UV fluorescent lamp instruments
The purity of water used for spraying UV fluorescent lamps is less critical than for xenon lamps Consequently, test panels should be sprayed with purified water containing less than 2.0 µg/g of dissolved solids and less than 0.5 µg/g of suspended silica.
If specimens show deposits or stains after exposure, it is essential to check the water purity to ensure it meets the specified requirements Contamination may occur from bacteria in the purified water used for spraying specimens If bacterial contamination is identified, the entire water spray system must be flushed with a chlorinating solution, like sodium hypochlorite, and thoroughly rinsed before resuming exposures.
It is advisable to continuously monitor the conductivity of the water used for specimen spray, even though conductivity does not always directly relate to silica content Exposures should be halted whenever the conductivity exceeds 5 μS/cm.
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All parts of the specimen spray unit must be made from stainless steel or a non-contaminating material that prevents the absorption of UV radiation and avoids the formation of unrealistic deposits on test specimens.
In humidity-controlled exposure chambers, sensors for measuring humidity must be positioned within the airflow and protected from direct radiation and water spray It is essential to maintain the measured relative humidity within ± 10% of the designated set point.
The humidity sensors shall be calibrated at least annually in accordance with the exposure device manufacturer’s instructions.
Any device that introduces periods of wetting of the exposed specimens by any method shall have means to programme the periods with and without wetting.
Other requirements for the exposure device
5.4.1 Although various designs of exposure device are used in practice, each device shall meet the following requirements.
5.4.1.1 Any device intended to simulate the effects of light and dark cycles shall have an electronic controller or mechanical device to programme periods with or without light.
Manufacturers must ensure that devices capable of varying exposure conditions are equipped with timers to accurately measure each period The duration of these exposure periods should be controlled within ± 10% of the shortest period utilized It is recommended to employ timers with high accuracy and repeatability Additionally, providing a method to record the length of each test period is optional.
To meet specific test procedure requirements, the device must be capable of registering or recording essential operating parameters, including the line voltage, lamp wattage, lamp current, and the spectral irradiance (or integrated spectral irradiance) within the utilized passband, along with the radiant exposure.
6 Test specimens — Preparation, replicates, storage and conditioning
Handling of test specimens
The handling of the test specimens can have a significant impact on the usability of the test result.
Form, shape, preparation
6.2.1 Form, shape and preparation of test panels have a significant impact on the durability. © ISO 2013 – All rights reserved 9
The preparation methods for test panels significantly influence their apparent durability It is essential for all interested parties to agree on the preparation method, which should ideally align with the standard processing techniques used in typical applications Additionally, a comprehensive description of the test specimen preparation method must be included in the test report.
The test panels should be prepared using substrates commonly employed in practice, such as plasterboard, wood, metal, or plastic materials Additionally, the application and drying methods for the coating must align with standard practices to achieve a typical coating thickness.
Unless otherwise agreed or specified, standard panels conforming to the requirements of ISO 1514 shall be used as substrate for the test coating.
NOTE Preferably, flat test panels of dimensions appropriate to the holders in the test chamber should be used.
Unless otherwise specified, only the front surfaces of the test panels will be coated with the material or coating system under evaluation If needed, the rear surfaces and edges of the test panels should be coated with a protective layer to prevent substrate deterioration throughout the testing period.
Stoving paints must be dried under the same conditions as their normal application For air-drying paints, coated test panels should be stored horizontally and dried at a temperature of (23 ± 2) °C and a relative humidity of (50 ± 5) %, following ISO 3270 standards The drying duration and subsequent storage must adhere to specified requirements.
6.2.6 All the test panels shall be permanently marked in a suitable way The thickness of the test coating shall be determined in accordance with ISO 2808.
Number of test specimens
In the case of testing carried out over a series of different test periods, an adequate number of test panels shall be prepared for each coating material.
If the property measurement test method does not indicate the required number of test specimens, it is advisable to prepare at least three replicate specimens of each material for every exposure stage.
For each exposure test, it is essential to include control materials with known durability, ideally those representing both poor and good durability Prior to making comparisons between laboratories, all parties involved must reach a consensus on the control materials to be utilized Additionally, the number of specimens for the control materials should match that of the test materials.
Storage and conditioning
6.4.1 If required, at least one additional test panel for each coating shall be prepared and stored at a temperature of 18 °C to 28 °C in the dark for use as a file specimen.
NOTE Such coated panels can change their properties during storage.
6.4.2 Coatings such as alkyd paints which are sensitive to storage in the dark shall be stored under conditions agreed between the interested parties.
Some materials may undergo color changes during dark storage, especially after being exposed It is crucial to conduct color measurement or visual comparison promptly after exposure, once the surface has dried.
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In certain instances, assessing the color change after a conditioning period of 24 hours can be beneficial in confirming the stability of the color once the specimens are taken out of the exposure chamber.
Set points for exposure conditions
The conditions and procedures for artificial accelerated weathering or irradiation exposure vary based on the selected method, as outlined in ISO 16474-2 or ISO 16474-3 Each exposure test utilizes specific set points for key parameters, including irradiance, temperature, and humidity, which are measured and controlled at a designated control point within the test chamber Table 3 details the maximum allowable deviation from these set points during equilibrium conditions of the exposure device.
Table 3 — Maximum allowable deviation from exposure condition set points
Set-point parameter Maximum allowable deviation of the measurement from the set point at equilibrium
Irradiance measured at a single wavelength a ±0,02 W/(m 2 ⋅ nm) Irradiance measured over a broad passband a ±5 W/m 2 Irradiance measured over a wide passband a ±75 W/m 2
Temperature of black-standard thermometer ±3 °C for set points up to 70 °C ±4 °C for set points greater than 70 °C
Temperature of black-panel thermometer ±3 °C for set points up to 70 °C ±4 °C for set points greater than 70 °C
Temperature of chamber air (when controlled) ±3 °C for set points up to 70 °C ±4 °C for set points greater than 70 °C
Full width at half maximum (FWHM), nm — a Terms see ISO 9370.
NOTE A single-point measurement does not mean conditions throughout the exposure chamber are the same
Running two tests in similar exposure devices does not guarantee identical results Exposure devices that utilize a black-standard thermometer or black-panel thermometer for temperature control will yield different outcomes compared to those that regulate air temperature.
Property measurements on test specimens
7.2.1 It shall be agreed between the interested parties which properties of the coating shall be determined prior to, during and after the exposure, using the appropriate standards.
NOTE Suitable methods include those given in ISO 2813, ISO 3668, ISO 11664-4, ISO 4628-1 to ISO 4628-8 and ISO 4628-10.
For intermediate examinations, test panels should remain unwashed and unpolished unless otherwise agreed upon by the involved parties For the final examination of the coating, it is essential for the parties to reach an agreement on whether the surface for evaluation will be unwashed, washed, or polished.
The individual property values must be clearly presented to highlight intermediate results and changes If necessary, comparisons should be made with the properties of unexposed or concurrently exposed control specimens For multi-stage tests, both intermediate and final examination results should be displayed in tables or graphs, illustrating the relationship with radiant exposure.
8 Periods of exposure and evaluation of test results
General
The consistency and reliability of results from tests performed under this International Standard depend on the materials tested, the specific properties measured, and the test conditions and cycles employed.
Sampling
Take a representative sample of the product to be tested (or of each product in the case of a multi-coat system), as described in ISO 15528.
Examine and prepare each sample for testing, as described in ISO 1513.
Determination of changes in properties after exposure
If required, these shall be determined as specified in ISO 2813 [10] , ISO 3668 [11] , ISO 4628-1 [12] , ISO 4628-2 [13] , ISO 4628-3 [14] , ISO 4628-4 [15] , ISO 4628-5 [16] , ISO 4628-6 [17] , ISO 4628-7 [18] , ISO 4628-8 [19] , ISO 4628-10 [20] , ISO 11664-4 [21]
Use of control materials
Periodic evaluation of test and control specimens is essential for assessing how material properties change over time due to exposure By determining the time or radiant exposure required to achieve a specific change in material properties, we can effectively rank the durability of different materials This approach is favored over arbitrary evaluations conducted after a set duration or exposure level.
Exposure to a specific time or radiant exposure can be utilized for testing purposes if all parties agree or if it is necessary for compliance with a specification Two key criteria must be considered when selecting the exposure: first, statistical analysis must demonstrate that the test material performs equally or better than the control material when minimum acceptable performance controls are used; second, a significant change in the property of interest must be observed in the least stable material being assessed.
NOTE An exposure time that produces a significant change in one type of material cannot be assumed to be applicable to other materials.
When comparing results from test and control materials, it is essential to employ suitable statistical analysis A distinction between the two can be established if the statistical analysis yields significant results at a minimum confidence level of 90%.
Use of results in specifications
A standard or specification for general use mandates a specific property level to be achieved after a designated time or radiant exposure during an exposure test, as outlined in the relevant sections of this International standard.
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The specified property level must be determined through an interlaboratory trial that accounts for variability from exposure and the measurement method This trial should adhere to the relevant International Standard for interlaboratory exposures and include a statistically representative sample of all laboratories or organizations typically involved in the exposure and property measurement process.
When a standard or specification mandates a specific property level after a defined time or radiant exposure in an exposure test, it must be grounded in statistical analysis from at least two independent exposures in each laboratory The experimental design for determining this specification should account for variability arising from both the exposure conditions and the testing method employed to assess the property of interest.
When reproducibility of results from an exposure test, conducted per this International Standard, is not confirmed through interlaboratory testing, performance requirements for materials must be defined by comparing them to a control material The control material and test specimens should be exposed simultaneously in the same device, with the specific control material agreed upon by all interested parties.
The test report shall contain the following information:
The specimen description must include a comprehensive overview of the specimens and their origins, along with details about the compounds used, including cure time and temperature when relevant It should outline the preparation method for the test specimens, specify the substrate material, thickness, and surface preparation, and describe the application method of the test coating Additionally, it is essential to document the drying or stoving duration and conditions, as well as the ageing process of the coating prior to testing The duration of conditioning for the test panels should be noted, especially if other tests were conducted previously The thickness of the dry coating, measured in micrometres according to ISO 2808, should be specified, indicating whether it is a single or multi-coat system Any deviations from the standard test method and specific test requirements, including the agreed limit for colour change in assessing colour fastness to light, should also be included.
When exposure tests are performed by a contracting agency, specimens are typically labeled with a code number It is the originating laboratory's duty to include a comprehensive description of the specimen when reporting the exposure test results.
9.2 Description of exposure test conducted in accordance with ISO 16474-2, ISO 16474-3 or ISO 16474-
4, including: a) a description of the exposure device and radiation (light) source, including:
1) the type of device and radiation (light) source, © ISO 2013 – All rights reserved ``,,`````,,```,,,```,````,`,-`-`,,`,,`,`,,` - 13
2) a description of the filters used,
3) if required, the irradiance at the specimen surface (including the passband in which the radiation was measured),
When conducting exposure tests, it is essential to document the number of hours the filters and radiation source were utilized before exposure began Additionally, the type and precise location of black and/or white temperature sensors must be specified, especially if they are not situated within the test specimen's exposure area For these temperature sensors, a detailed description of their mounting in the exposure area is necessary If applicable, the instrument used to measure humidity should be identified, along with the method employed to ensure uniformity during the test Lastly, a comprehensive description of the exposure cycle is required, detailing the specifics of each light and dark period.
1) the set point for the black- and/or white-panel temperature sensor used and the maximum allowable deviation from the set point if different from that in Table 3,
2) the set point for the relative humidity and the maximum allowable deviation from the set point if different from that in Table 3,
For tests involving a water spray period, it is essential to document the duration of the spray and specify whether it was applied to the exposed face, the back, or both surfaces of the specimens Additionally, if the total solids in the water used for spraying exceeded 1 μg/g, the total solids and silica content must be reported.
4) for tests where water is condensed on the specimens, report the set point for the length of the condensation period,
The article outlines key aspects of the testing process, including the duration of light and dark periods, the method for mounting specimens in the exposure frame along with the backing materials utilized, and the procedure for repositioning test specimens if applicable It also details the radiometer employed for measuring radiant exposure and notes any unusual observations or anomalies encountered during the test.
9.3 Test results a) a complete description of the test procedure used for measurement of any properties reported; b) the results shall include:
1) the results from property measurements on the test specimens,
2) the results from property measurements on control specimens,
3) the results from property measurements on unexposed file specimens, if determined,
4) the exposure period (either the time, in hours, or the radiant exposure, in J/m 2 , and the passband in which it was measured).
9.4 The date(s) of the exposure test.
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Procedure for measuring the irradiance uniformity in the specimen exposure area
This annex outlines the guidelines for utilizing ISO 16474 in laboratory light source exposure and specifies the requirements for manufacturers of devices that expose materials to these light sources.
In devices utilizing a rack to hold specimens and rotate them around a central light source, it is essential to measure the irradiance at the position closest to the light source (position A) and at two positions farthest from it (position B) Using a radiometer placed on the rotating rack provides the most accurate assessment of irradiance uniformity The relationship between the irradiance at position B and position A must be clearly defined.
E B ≥0 7, E A (A.1) a) Flat specimen rack b) Canted specimen rack
Figure A.1 — Determining irradiance uniformity in devices using a rotating specimen rack
In devices where specimens are arranged in a flat plane before a light source, it is essential to measure the irradiance at the position closest to the light source (position X) and at two opposite corners of the specimen plane (position Y) The relationship between the irradiance at position Y and position X must be established to ensure accurate testing and analysis.
``,,`````,,```,,,```,````,`,-`-`,,`,,`,`,,` - a) Flat specimen plane with fluorescent lamps b) Flat specimen plane with multiple point sources c) Flat specimen plane with multiple line sources
Figure A.2 — Determining irradiance uniformity in devices using a flat specimen plane
In cases where the device's design results in the maximum irradiance not being located at the center of the exposure area, or the minimum irradiance not being at the farthest position, the actual maximum irradiance should be utilized for E A or E X, while the actual minimum irradiance should be applied for E B or E Y in Formulae (A.1) and (A.2) Additional irradiance measurements may be conducted at various positions within the exposure area, ensuring that these measurements are at least 70% of the maximum irradiance Furthermore, unless stated otherwise, a minimum of four measurements must be taken at the periphery of the proposed exposure area, particularly near the corners of flat specimen planes when using fluorescent lamps or line sources as light sources.
For more precise definition of the allowed exposure area where E X ≥ E Y or E B ≥ E A , many more than four measurements near the periphery of the exposure area will be necessary.
To assess the uniformity of irradiance, reference materials can be utilized, provided their aging is unaffected by heat or moisture, or if the impacts of these factors are understood The reference material's characteristic property should change in a known manner, ideally linearly, without an induction time A typical plot (Figure A.3) illustrates this relationship The ideal reference material exhibits a consistent linear response throughout the exposure duration Materials with an induction period followed by rapid changes are unsuitable, and those with a linear response that later becomes nonlinear should only be used during the linear phase Reference specimens must be placed at the center and edges of the exposure area, all exposed simultaneously, until a measurable change occurs The change at the outer positions should be at least 70% of that observed at the center.
Actual irradiance measurements are favored over reference materials due to potential discrepancies in properties between specimens exposed to varying conditions These differences can be significantly influenced by temperature, moisture levels, and irradiance variations, particularly between the extremes of the exposure area and the center.
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X radiant exposure or exposure time (arbitrary units)