THICKNESS SWELLING TEST
1.1 Constant temperature test tank
2.1 1 sample per lot
2.2 Length: （50±1） mm
2.3 Width: （50±1） mm
3.1 We ensure the following environmental conditions: 18-22 ℃ and relative humidity of 60-70%. The sample’s weight before the test and after 24 hours of testing should not increase by more than 0.1%.
3.2 We measure the thickness at the center of the samples and at 4 points determined drawing a diagonal line from the centre of the sample to the 4 corners (the 4 points should be 10 mm away from the corners of the sample).
3.3 We place the samples into the test tank. The water in the test tank should be 18-22 ℃ and its PH should be 7±1. The samples should be completely surrounded by water and there should be a space between the bottom of the samples and the internal platform in the water tank. Samples should be placed apart so that they can expand freely. After 24 hours, we take the samples out of the water and dry them. Within 30 minutes, we measure the thickness at the five points.
4. ASSESSING TEST RESULTS
We calculate thickness swelling at each one of the sample's 5 points using the following formula.
T = (H2-H1)/H1 × 100%
T: Thickness swelling at one point
H1: thickness recorded at the first measurement
H2: thickness recorded at the second measurement
If average thickness swelling is ≤ 3%, the product conforms to the national standard.