The cracking or peeling resistance of the dry film is an important testing property of the paint and varnish coating, and different products will have different testing methods. Among them, the impact test is one of them. The elastic impact Tester is a type of paint film impact Tester. The test method includes pass/fail test (that is, test with a weight of specified mass and a drop height to see the test results. Whether it meets a specific specification standard) and classification test (that is, by gradually increasing the weight height and/or mass to determine the minimum mass and drop height when the coating cracks or peels off from the bottom layer).
This article takes the specific test method of Pushen's TCJ-II elastic impactor as an example. The structure of the instrument is composed of a conduit, a height limit ring, a handwheel, a bracket, a base, a leveling foot, a leveling bubble, a compression sleeve for compressing the test plate, and a locking handle.
Test The test generally needs to prepare a test plate with a visual lens, flatness, no deformation, and a thickness of at least 0.25 mm. Let's take a look at the detailed experimental test method.
test preparation
1. Visual lens: the magnification is 10 times, self-provided.
Requirements for test panels: Unless otherwise agreed, the substrate shall be metal and conform to the standard. It is required that the test plate should be flat, without deformation, and have a thickness of at least 0.25 mm. The size of the test plate should allow at least 5 different parts of the plate to be tested, each part is not less than 20 mm from the edge of the plate , and the distance between each part is not less than 40 mm. The treatment, coating and drying of the test panel must be carried out according to the prescribed method. The thickness of the coating must also be measured in accordance with the regulations, and the measurement should be carried out at the part to be tested or as close as possible to the test part, and only the test panel whose paint film thickness is not greater than 10% of the specified or agreed film thickness can be used .
2. Unless otherwise agreed, the experiment shall be carried out at (23±2)°C and (50±5)% relative humidity.
3. According to the required standard, select the corresponding mold base and align it with the hole on the base (5).
4. Select the corresponding weight according to the selected mold base and put the weight in from the top of the conduit (1).
5. Put the height stop ring (2) over the conduit and secure with screws.
6. Adjust the instrument level by adjusting the leveling feet (6) and leveling bubble (7).
test steps
a. Pass/fail experiment:
1. Adjust the height of the height limit ring (2) so that the indicated scale just meets the specified drop weight height. If necessary, install the depth control ring, the total thickness of the depth control ring can meet the indentation depth agreed by both parties or otherwise specified.
2. Put the test plate on the mold base, so that the painted surface is up or down, so that the indentation can be concave or convex, and turn the handwheel (3) to make the compression sleeve (8) press the test plate , loosen the weight and let it fall onto the test plate.
3. Inspect the coating with a lens to see if the coating has cracked or peeled off the substrate and if the substrate has cracked.
4. Repeat the test four more times at different positions of the test panel (total of 5 drop weight points). If at least 4 test points are not cracked or peeled off from the substrate, the coating is qualified.
b. Grading test:
1. Adjust the height of the height limit ring (2) so that the indicated scale just meets the specified drop hammer height, and no damage should be expected at this height. If necessary, install the depth control ring, the total thickness of the depth control ring can meet the indentation depth agreed by both parties or otherwise specified.
1. Put the test plate on the mold base, so that the painted surface is up or down, so that the indentation can be concave or convex, and turn the handwheel (3) to make the compression sleeve (8) press the test plate , loosen the weight and let it fall onto the test plate.
2. Remove the test plate from the device and observe the cracking of the coating in the impact area. If there is no obvious crack, operate at a higher height until cracking is observed. According to the weight used, the weight is 1kg (2 lbs) in height increments of 25mm (1 inch) or multiples of 25mm (1 inch). If no cracking is observed with the weight at the maximum height allowed by the instrument, repeat the operation with 2kg (4 lbs).
3. Once cracking is observed at a certain height, proceed as follows: drop to the test plate 5 times at this height and at a height 25 mm (1 inch) higher than this height and 25 mm (1 inch) lower than this height, that is, a total of 15 drops. The test needs to be carried out on the same test panel.
4. Use a magnifying glass to check whether the coating is cracked or peeled off from the substrate, and list and count the 15 impact results of pass and failure. A combined mass/height report of the resulting change in most of these damages is a result of impact damage.
5. If the results cannot be obtained according to the above operations, repeat steps (4), (5), and take all three heights as applicable values, and then ensure that the range of test heights is used to replace the height of impact damage.
Precautions
1. The sampling of the tested samples and the treatment of the test panels should be carried out in accordance with the standard regulations.
2. Note that the weight should be tested by selecting the corresponding mold base and the additional weight corresponding to the corresponding height mark according to the number.
3. There are four height limit rings, which must be used together. This height limit ring is applied to the ISO standard and used with punches with 20mm steel balls. When the height limit ring is not added, the depth of the 20mm punch into the mold base is 10mm. If the depth of the punch into the mold base is 7mm, two upper limit pads of 1mm and 2mm must be placed, and so on. Please note that the minimum indentation depth of the punch in the standard is 2mm, that is, the maximum pad height is 8mm, that is, one piece of 1mm, 2mm, and 5mm. This is the limit height, and all rings must not be raised to avoid damage to the instrument.
4. After all the tests are finished, remove the accessories of the instrument and put them back in place to protect the cleanliness of the instrument.
