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Evaluation method of aging test results of paint film human xenon lamp

by:GESTER Instruments     2021-04-30
The principle of accelerated aging test is different for different light sources to accelerate the aging test. The ultraviolet spectrum of the carbon arc lamp has a large spectral energy in the part of wavelength 300nm -380nm (the energy of visible light and infrared light is very small), and the acceleration of the aging test is faster. The spectral energy distribution of the xenon arc lamp is closer to sunlight than that of the carbon arc lamp, and the aging test is more simulated, but the acceleration is slightly worse. Both light sources are commonly used in aging tests. The national standard G? 'T.865-2009 uses xenon arc lamps, while carbon arc lamps are also commonly used in foreign countries (such as Japan). The paint film is exposed to artificial radiation. After a certain exposure to radiation energy, the selected properties will change to a certain degree or reach a certain degree of radiation exposure required for aging. The performance of the exposed paint film is compared with that of the unexposed paint film. (Comparative sample) Performance comparison can reflect the aging condition of the paint film. Solar radiation is the main cause of paint film aging. It is particularly important to simulate this parameter with artificial radiation. Xenon arc lamps with different filter systems can change The spectral distribution of the generated radiation can respectively simulate the solar radiation and the spectral distribution of the ultraviolet and visible range of solar radiation filtered by 3mm glass. The distribution of the two spectral energy describes the filtered light radiation below the wavelength The irradiance value and the allowable deviation of the 400nm ultraviolet light range, within this range, the xenon arc lamp radiation can better simulate solar radiation. The sample sample adopts a standard test board, and its material, coating material and construction method are all It should be the same as the actual object represented. The test plate should be flat and the size should be compatible with the test box and sample rack. The number of samples should meet the needs of testing in different cycles. The samples should be permanently marked. If necessary, a reference should be prepared. Sample and comparison sample. Test step 1. Placement of the sample Place the sample on the sample holder, and ensure that the surrounding air is circulated. The sample can be arranged at a certain interval (such as the upper row and the lower row exchange ). If it is operated in a discontinuous manner, the sample holder can be rotated by 180° to make the sample turn away from the radiation source to produce periodic changes. The sample and the reference sample can be exposed together. 2. The temperature and humidity of the test and The temperature in the wetting operation test box is (38+- 3) e, and the relative humidity is 40%-60%. The wetting operation of the sample is shown in Table 2. During the wetting process, the radiation exposure cannot be interrupted. 3. The test time is as follows One of the methods is to control the test time: (1) The surface of the sample has been exposed to the specified radiation; (2) The test has met the specified aging index. In this case, the sample should be taken out for inspection at different stages during the test, and the aging process should be drawn. The curve determines the end point of the test. 4. The inspection of the test and the final test should be carried out continuously. Only when the xenon arc lamp or filter system is replaced and the sample needs to be taken out at a certain stage of the test, can it be interrupted. During the intermediate inspection, The sample cannot be washed or polished. During inspection, the area around the test plate and the hole is not counted within 5mm. The change pattern of the paint film in the artificial accelerated test is similar to that of natural climate exposure. The initial change is more obvious, and the later change is gradually gentle. Therefore, the initial stage The inspection period should be shorter, such as once every 48h, after 192h (8 days), it can be checked every 96h. After each inspection, the upper and lower positions of the sample should be interchanged. The end of the test should be based on the paint film The specific requirements for the degree of aging damage may be determined by the inspection indicators agreed upon by both parties. General situation Next, when the damage degree of any one of the properties of the paint film reaches the comprehensive rating 'Poor 0The inspection results should show the intermediate results and gradual changes of various properties of the paint film. When necessary, it can be compared with an unexposed reference sample or a reference sample exposed at the same time. If it is a multi-stage test, the results of the intermediate inspection and the final inspection should be given in the form of a table or in the form of a diagram of the radiation exposure function. The grading method of paint film aging [3] GB 'T.766 -2008 'The grading method of paint and varnish coating aging' stipulates the general rules for the grading of coating aging, the grading method of aging individual indicators, and decorative coating and protection A comprehensive rating method for the aging of sexual coatings. This standard is suitable for the evaluation of the aging performance of paint films under natural aging and artificial accelerated aging conditions. 1. General rules are rated according to the degree of damage of the paint film after aging, the number and size are divided into 0-5 levels , 'O' means no damage, '5' means serious damage (see Table 3). If necessary, the middle half level can be used to record the damage phenomenon. The uniform damage visible on the surface of the paint film is rated by the degree of damage ; Paint film discontinuity or partial irregular damage, use the number of damage to rank; when the type of damage has a large and quantitative meaning, add the rating of the damage size. 2. Individual ratings. Individual evaluations include loss of gloss, discoloration, chalking, cracking, and Assessment of blistering, rusting, peeling, mildew, spots, gold, and contamination levels. According to the general rules of rating, the damage degree, the amount of damage and the magnitude of damage are evaluated separately. The degree of damage and the amount of damage are usually considered together. However, loss of gloss, discoloration, chalking, pan-golding, and staining are not rated for damage.
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