UV weather aging chamber is used to measure air temperature, sample temperature, relative humidity, rainfall, wetting time and light time shall be appropriate to the method of exposure used and shall be agreed by the parties concerned.
Note: wetting time is usually determined by the use of galvanic cells or similar electrical methods.
Test specimens: shape and preparation: the size of the test specimens shall conform to the requirements of the corresponding test method or of the properties to be measured after exposure, unless it is required that samples are cut from a sheet or other exposed sample for the specified test.
If the tested material is a granular, lamellar or other extruded or molded mixture in its initial state, it shall be machined directly in a suitable manner
To sample, or to process into a sheet by an appropriate method, from which a sample is cut.The method used shall be agreed by the relevant party and shall be closely related to the material processing method adopted by the user.
The sample preparation methods are shown in GB/T9352, GB/T17037.1, GB/T17037.3, GB/T17037.4, GB/T11997, IS0294.2 and IS0294.5.
If the material to be tested is an extruder, molded piece, or sheet, the sample may be cut from the pre-exposed or post-exposed material, depending on the specific test requirements and material characteristics.
For example, materials that are significantly embrittlement after aging should be exposed in the shape tested because of the difficulty of processing after exposure;Conversely, laminates may be layered at the edges and should be exposed in sheet form and cut after exposure.
Note: samples prepared by machining are shown in IS02818.When the aging behavior of a specific product needs to be determined, the product itself should be exposed whenever possible.
The product or part of the product that is large enough for the test shall be exposed according to its own shape. The exposed surface shall not be removed in the preparation of the sample after the material is exposed and the sample is cut from it.The specimen to be cut from the exposed sheet shall be at least 20mm away from the sheet edge and the support of the fixture or non-simulated actual conditions.No part of the exposed surface of the material shall be removed during sample preparation.Only samples of the same size and roughly the same exposed area should be compared.
Number of samples: the number of samples for each test condition or exposure period shall be at least the same as specified in the relevant test methods for post-exposure performance testing.
Note: the recommended number of exposed specimens for mechanical performance testing is twice that required by the relevant national standards (it is well known that there is a large standard deviation in mechanical performance testing of aged plastics).The total number of samples will be determined by the initial value of the test and the number of required performance values after each exposure cycle.
Condition control and storage: if the sample needs to be machined and pretreated for ease of preparation, the details of the preparation should be recorded.
Before the test, the sample shall be properly adjusted according to the type of material and the test method to be used.The process of state adjustment shall be recorded in accordance with GB/T2918.
If the state adjustment period used is less than the minimum period specified in GB/T2918, the state adjustment period shall be recorded as it will seriously affect the subsequent test results (e.g., the test sample is very sensitive to humidity and/or the sample is exposed to extreme weather conditions).
The reference samples should be stored in a normal laboratory environment away from light, using one of the standard environments given in GB/T2918.
Note: some materials, especially aging materials, will change color in dark storage.