Two exposure methods of ultraviolet aging test chamber
When using the ultraviolet aging test box for aging test, the surface temperature of the sample is an important exposure parameter. Generally, high temperature will accelerate the degradation process of the polymer. The allowable test temperature should be determined according to the test material and aging performance evaluation index. Fluorescent ultraviolet lamps emit less infrared rays than xenon lamps and carbon arc lamps. The heating effect of the sample surface is basically formed by convection of hot air. Therefore, the temperature difference between the blackboard thermometer, the black standard thermometer, the surface of the sample and the air in the exposed chamber is very small.
The following two exposure methods: exposure methods 1 and 2 correspond to the equipment described in â‘ and â‘¡, respectively. Customers can also use other methods, but the exposure conditions should be stated in the test conditions.
Exposure method 1
After the sample is exposed to light for a period of time, it is followed by a non-irradiation period (temperature change and condensation on the sample). The test period is in accordance with the relevant standards. If there is no specified cycle condition, the following cycle is recommended:
Irradiation exposure at a black standard temperature of 60 ° C ± 3 ° C for 4h or 8h, and then exposure at a black standard temperature of 50 ° C ± 3 ° C without radiation condensation for 4h.
Note: The degradation of some polymers (such as PVC) is very sensitive to temperature. In this case, it is recommended to use a radiation exposure temperature of less than 60 ° C (such as 50 ° C) to simulate a colder climate.
When the procedure of irradiation exposure followed by condensation exposure is selected, the minimum allowable irradiation or condensation exposure period is 2h to ensure that the conditions of each exposure period reach equilibrium.
Exposure method 2
The sample is continuously subjected to a radiation exposure and a periodic test with water spray. Relevant standards during the test period. If not specified, the following test conditions are recommended:
Irradiation exposure at black standard temperature 50 ℃ ± 3 ℃, air relative humidity (10 ± 5) ﹪ for 5h, then continue irradiation exposure and spray water for 1h at black standard temperature 20 ℃ ± 3 ℃.
Note: â‘ : Use the moisture condensing machine to wet the exposed surface of the sample. Moisture is generated by heating water in the container below the sample rack.
â‘¡: When the equipment does not comply with the exposure method 1, the method of providing relative humidity control in the exposed room or the method of spraying the sample with pure water or an aqueous solution simulating acid rain may be adopted. Refer to GB / T 9344-88 for water usage.
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