This method is used to simulate the consequences of the coating film being impacted by external stones during the service period in a short enough time. The level of stone impact resistance is jointly expressed by the stone impact point level and the stone impact point diameter level on the 5cmx5cm test board. Note: The minimum percentage allowed for the minimum rocking points is about 10%, and the grades of rocking points are shown in Table 21-20.
Test Instruments and Materials
①Stone striking machine as shown in Figure 21-39;
②A static condensation box that can maintain a temperature of (5.5±0.5)°C;
③ Pebbles (paving stones washed by water), with a diameter of 9.5~16.5mm;
④ Polyethylene plastic tape;
⑤ The size of the test plate is 200mmX100mm.
Steps
Steps①After the steel test panel has been painted for at least 48 hours, and the plastic test panel has been painted for at least 5 days, put the test panel in a static condensation box at a temperature of (5.5±0.5)°C, and conduct the test after 2 hours;
② Clamp the test plate on the test plate fixture, and put 0.5L pebbles in the hopper;
③ Adjust the air pressure to (0.5±0.02) MPa first, then open the air valve, and close the air valve after all the stones have been projected;
④Take out the test panel, stick the entire surface of the stone with tape, and then quickly tear off the tape by hand.
result evaluation
The stone chip resistance grade of the coating is jointly expressed by the number grade code of the stone chip point and the diameter grade code. The grade code representing the degree of stone chip resistance can be understood and judged by the four pictures in Figure 21-40.
Example of coating stone chipping resistance grade: "7A level" means that there are 10~24 stone chipping points with a diameter of less than 1mm on the test plate of 5cmx5cm.
