This standard is issued under the fixed designation G 151; the 1 This practice is under the jurisdiction of ASTM Committee G-3 on Weathering. G151-19 Standard Practice for Exposing Nonmetallic Materials in Accelerated Test Devices that Standard + Redline PDF Bundle ASTM License Agreement . G151 - 00 Standard Practice for Exposing Nonmetallic Materials in Accelerated Test Devices that Use Format, Pages, Price. PDF ASTM License Agreement.
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Standards PDF Cover Page Document preview. Historical. ASTM G151-00 ASTM Committee G3 is developing a standard guide for application of statistics to . ASTM G 151 - Designation: G 151 – 09 Standard Practice for Exposing Nonmetallic Materials in Ac. ASTM G151. UV EXPOSURE (GENERAL). This practice provides general procedures to be used when exposing nonmetallic materials in accelerated test.
With proper selection of? However, with many? Fluorescent UV lamps can be selected to have a spectral output corresponding to a particular ultraviolet region of solar radiation. The xenon arc, when appropriately?
If it is not positioned within the specimen plane, it shall be calibrated for irradiance at the specimen distance. Calibration of narrow or broad-band ultraviolet radiometers using a spectroradiometer shall be conducted according to Method G 130. The radiometer shall be calibrated using a light source with the same spectral 3 G 151 — 09 power distribution as the one that the radiometer will be used to measure.
In addition, the radiometer shall also be calibrated using the same test chamber geometry that is, lamp to specimen plane distance and orientation for which it will be used. More frequent calibrations are recommended. Some apparatus provide for measuring irradiance in a speci? Since it is not practical to monitor the surface temperature of individual test specimens, a speci? It is strongly recommended that the black panel temperature sensor be mounted on a support within the specimen exposure area so that it receives the same radiation and cooling conditions as a?
The black panel also may be located at a?
This is not recommended, however, because black panels mounted at a? Requirements for each type are found in Annex A2.
Uninsulated black-panel temperatures generally correspond to those for dark coatings on metal panels. Insulated black panel thermometer temperatures generally correspond to those for the exposed surface of dark samples with poor thermal conductivity.
The response time for temperature changes is slightly slower for insulated black panel thermometers compared to uninsulated black panel thermometers. When light sources that emit very little infrared radiation are used, there 4 generally will be very small difference in temperatures indicated by the two types of black panels or between light and dark colored specimens.
NOTE 12—There can be differences in temperature indicated by a single type of black panel thermometer, depending on the speci? In some cases, temperature of either the uninsulated or insulated white panel thermometer may be used to specify exposure conditions. The uninsulated or insulated white panel shall be constructed in the same way as the corresponding uninsulated or insulated black panel thermometer, except for use of a white coating with a good resistance to aging.
The re? If either type of black or white panel thermometer is not positioned in the specimen exposure area, the exact position used shall be described in the test report. If no instructions are provided by the device manufacture, sheathed thermocouples shall be calibrated according to Method E 839, and resistance thermometers used as the sensing element for black or white panel thermometers shall be calibrated according to Method E 644.
Unless otherwise speci? Wherever possible, calibrations should be traceable to a nationally recognized standards agency. Any apparatus operated according to this standard, which attempts to simulate the effects of moisture, G 151 — 09 shall have means for providing moisture to specimens using one or more of the following methods: humidi?
The type and rate of material degradation can be affected signi? Without proper treatment to remove cations, anions, organics, and particularly silica, exposed specimens will develop spots or stains that do not occur in exterior exposures. If the water used for specimen wetting is above 1 ppm solids, the solids and silica levels must be reported.
Recirculation of water used for specimen wetting is not recommended and if done the recirculated water shall meet the speci? NOTE 13—Distillation, or a combination of deionization and reverse osmosis can effectively produce water with the desired purity.
On some occasions, exposed specimens can be contaminated by deposits from bacteria than can grow in the puri? If bacterial contamination is detected, the entire system used for specimen wetting shall be?
If plastic materials are used, they shall not leach low molecular weight UV absorbing components into the water. NOTE 14—There is currently no generally accepted method for characterizing the uniformity or consistency of specimen wetting. It is preferable to use cycle timers that are accurate and reproducible as possible. Optionally, means to provide a record of the length of light and dark cycles may be provided. Test Specimens 6. When the behavior of a speci?
The exact shape and dimensions of the specimens to be exposed will be determined by the speci? The procedures used to machine or cut individual test specimens from a larger sheet or part may affect the results of the property measurement and the apparent durability.
Therefore, the method used for specimen preparation shall be agreed upon by the interested parties and should be related closely to the method normally used to process the material in typical application. The effects any cutting or machining operation may have on the properties of individual test specimens usually are much larger when the test specimens are cut from a large piece after exposure. This is especially true for materials that embrittle on exposure.
In no circumstances shall any material from the exposed face be removed during the test specimen preparation. The time of each light and dark cycle shall be controlled to G 151 — 09 6. When destructive tests are used, the total number of test specimens required will be determined by the number of exposure periods used and whether unexposed? It is recommended that control materials known to have relatively poor and good durability be used.
Control materials are used for the purpose of comparing the performance of the test materials to the controls.
Before laboratory to laboratory comparisons are made it is necessary to establish agreed upon control materials. The number of specimens of the control material should be the same as that used for test materials. In some circumstances, it may be necessary to precondition the sheets prior to cutting or machining to facilitate specimen preparation. The properties of some materials are very sensitive to moisture content and the duration of conditioning may need to be longer than those speci?
General Procedure 7.
For open? Typically, these parameters are measured and controlled at a single position within the chamber. During normal operation, there is an allowable departure of the measured value from the set point.
Annex A3 provides detailed information about the maximum allowable departure of the measured value from the set point. It does not mean two tests 6 run in similar cabinets will produce the same results. Cabinets that control temperature by the black panel will not produce the same test as cabinets that control by air temperature. After each exposure increment, measure the same property that is measured initially on the specimens.
Take care to make the property measurement in the same position used for the initial measurement. NOTE 15—To monitor the response of the instrument used to measure the desired property, one can measure a calibration standard each time the instrument is used.
Compare the value of the property after exposure to the property measured on an unexposed set of specimens measured prior to beginning the exposure. Alternatively, the property can be measured on a separate set of unexposed? The results for the unexposed? NOTE 16—Procedures and formulas for calculating the change in material property of test materials and reference materials after exposure can be found in Practice D 5870.
It is essential that color measurement or visual comparisons be carried out as soon as possible after exposure once the exposed surface has dried. Periods of Exposure and Evaluation of Test Results 8.
This method is preferred over evaluating materials after an arbitrary exposure time or radiant exposure. When a single exposure period is used, select a time or radiant exposure that will produce the largest performance differences between the test materials or between the test material and the control material.
An G 151 — 09 exposure time that produces a signi? Do not use arbitrary acceleration factors relating time in an exposure conducted according to this practice and time in an outdoor environment because they can give erroneous information. The acceleration factor is material dependent and is only valid if it is based on data from a sufficient number of separate exterior and laboratory accelerated exposures so that results used to relate times to failure in each exposure can be analyzed using statistical methods.
NOTE 17—An example of a statistical analysis using multiple laboratory and exterior exposures to calculate an acceleration factor is described by J.
NOTE 18—Fischer illustrates use of rank comparison between test and control materials in speci? Test Report 9. NOTE 20—If exposure tests are conducted by a contracting agency, specimens usually are identi? In such cases, it is the responsibility of the originating laboratory to provide the complete specimen description when reporting results of the exposure test. Conduct these round-robins according to Practice E 691 , and include a statistically representative sample of all laboratories or organizations who would normally conduct the exposure and property measurement.
All specimens shall be exposed simultaneously in the same device. All concerned parties must agree on the speci? Expose replicates of the test specimen and the control specimen so that statistically signi?
Precision and Bias 10. Keywords 11. The location of the maximum irradiance may vary from the position X shown. The positions for Y that de? For more precise de? The change in characteristic property of the reference material shall be a known function, preferably linear, of radiant exposure. Do not use reference materials, that show an induction time with little change in property as a function of radiant exposure.
The preferred reference material shows a completely linear response throughout the exposure period.
Materials that show a linear response followed by a period where response is not linear must only be used during the exposure period exhibiting linear response. Prior to using a reference material to determine uniformity of irradiance, repeatability of the property change for specimens of the reference material exposed at the same position must be determined.
When reference materials are used, all specimens shall be from the same lot. Expose reference material specimens throughout the proposed exposure area. Conduct exposures until there is a measurable change in the characteristic property being monitored. The allowed exposure area is de?
NOTE A1. The surface of this plate that faces the light source shall be coated with a black layer which has good resistance to aging. A thermal sensitive element shall be?
The backside of the metal panel shall be open to the atmosphere within the exposure chamber. The minimum dimensions for the stainless steel plate are 70 mm by 40 mm 2. These acceleration factors are not valid for several reasons. An example of a statistical analysis using multiple laboratory and exterior exposures to calculate an acceleration factor is described by J.
Simms 1. More specific information on how each factor may alter stability ranking of materials is given in Appendix X1. A common application is conducting a test to establish that the level of quality of different batches does not vary from a control material with known performance. Comparisons between materials are best made when they are tested at the same time in the same exposure device.
Results can be expressed by comparing the exposure time or radiant exposure necessary to change a characteristic property to some specified level. In some cases, a reference material is exposed at the same time as a test material and the exposure is conducted until there is a defined change in property of the reference material.
The test material then is evaluated. In some cases, the results for the test material are compared to those for the reference material. These are inappropriate uses of reference materials when they are not sensitive to exposure stresses that produce failure in the test material or when the reference material is very sensitive to an exposure stress that has very little effect on the test material.