Coating mass detection - Artificial Accelerated Conditioning

The artificial accelerated aging test is a test under the artificial climate conditions created in the laboratory by simulating various climate factors in nature. Controlling a certain temperature, humidity, rainfall cycle and time to carry out the test, and evaluating the grade based on the degree of damage to the appearance of the model, can evaluate the weather resistance of the coating product in a relatively short period of time.

(1) Test equipment and operation

The artificial accelerated aging test was carried out in an artificial aging machine. The structure of the artificial aging machine can be roughly divided into three parts: upper, middle and lower. The upper part is mainly the control panel of the aging machine, which is equipped with various control instruments and switches, which can change the parameters of the accelerated aging test such as temperature, humidity, drop-off amount, and drop-off cycle according to different situations. The middle part is the laboratory where samples are aged. The inner wall is made of stainless steel. In order to increase the thermal insulation performance of the room, the inner wall is filled with thermal insulation materials. A light source is suspended in the middle of the laboratory. Due to the different spectral wavelength ranges and distributions of the light source (such as carbon arc lamp and xenon lamp), different light sources have different accelerations for aging tests, such as ultraviolet carbon arc lamps. The part of the spectrum with a wavelength of 300-380nm has a great spectroscopic ability, and the energy of the visible light and infrared part is very small, so the acceleration of the aging test is faster. The spectral energy distribution of the xenon lamp is closer to sunlight than that of the ultraviolet carbon arc lamp, so the simulation of the aging test is better, but its acceleration is slower than the former. There is also a drum with a certain diameter rotating at a constant speed around the light source in the laboratory, so as to ensure that the samples on the drum can receive uniform illumination. At the back or side of the laboratory, several nozzles are also installed, which can automatically spray water on the samples on the drum at regular intervals to simulate natural dehydration. The temperature in the laboratory can be adjusted by the indoor cooling nozzle and temperature commutator; the humidity can be generated by the humidification box, and the humid air is sent to the laboratory by the blower. The humidification box, blower and transmission mechanism are installed in the artificial aging machine. the lower part.

(2) Evaluation of test results

Factors affecting the results of artificial accelerated aging test In addition to the light source, temperature, relative humidity, rainfall cycle and water quality for rainfall are all important factors in the aging test process. But countries have different standards for their control. Such as temperature control, my country requires the air temperature in the laboratory to be controlled at (45±2)°C, while Japan and the United States require that the surface temperature of the sample in the laboratory be controlled by observing the blackboard thermometer. The aging test blackboard temperature stipulated in Japanese standard value is (63 ± 3) ℃, and the relevant American standard stipulates that the blackboard temperature is (63 ± 5) ℃. my country requires the relative humidity in the laboratory to be 65%~75%. The relevant standards of the United States stipulate that the relative humidity should be 50% ± 5% during the test period of the light source in the test cycle. (Related instruments: constant temperature and humidity Test Chamber )

The rainfall cycle in my country is stipulated as 12 minutes of rainfall per hour, and the relevant standards of the United States stipulate that the rainfall is 18 minutes per 12omin. The water used in the artificial accelerated aging test requires distilled water and ion exchange resin purified water, distilled water is used for cooling, and ion exchange resin purified water is used for rainfall, so as to avoid the scale caused by the high hardness of tap water from affecting the paint film, especially the white paint film. The test results also avoid the test errors caused by the different tap water quality in different places.

The changing law of paint products in the process of artificial accelerated aging test is similar to that of natural exposure test, that is, the change is more obvious in the early stage, and the change is gradually stable in the later stage, so the inspection period is shorter in the early stage, and it is required to stop the machine for inspection every 48 hours After 192 hours of the test, stop the machine every 96 hours and inspect the sample. After each inspection, the upper and lower positions of the sample in the testing machine should be exchanged. The termination index should be based on the degree of aging and damage of various paint films and Depends on specific requirements. Generally, the test can be stopped when the damage of the paint film reaches any one of the "bad grades" in the comprehensive rating of the "Paint Film Aging Test Rating Method" (GB/T1766-1995).