Analysis of sponge resilience test method (GB/T6670-2008)

The national standard GB/T6670-2008 replaced GB/T6670-1997 'Determination of Resilience Performance of Flexible Foam Plastics' to 'Determination of Resilience Performance of Flexible Foam Polymeric Materials by Falling Ball MethodMethod A and Method B. Details of the determination of the resilience performance of the flexible foam polymer material by the falling ball method: 1. Test range: 1.1 specifies two methods for determining the resilience performance of the flexible foam polymer material. 1.2 It is suitable for the determination of the rebound performance of soft foam polymer materials. 2. The following terms and definitions apply to this standard. 2.1 Open-cell soft foam material: a soft foam material with a closed cell volume of less than 25%. 2.2 Closed-cell flexible foam: a flexible foam material with a closed cell volume greater than 25%. Principle: A steel ball with a certain quality and diameter is dropped from a fixed height to the surface of the sample, the height of the steel ball is measured, and the percentage of the ratio of the height of the steel ball to the drop height is calculated. Method A, testing equipment and main parameters: Sponge ball rebound resilience tester, including a transparent tube with an inner diameter of 30mm～60mm, a steel ball with a diameter of 16mm±0.5mm, a mass of 16.8g±1.5g, and a magnet or other The device is released. There is no rotation during the fall, and it is always in the center position. The drop height is 500mm±0.5mm. The top of the ball should be 516mm from the surface of the sample. Therefore, the origin of zero rebound is the diameter distance of the steel ball above the surface of the sample. If the pipe is not vertical, it may cause measurement errors. The steel ball touches the inner wall of the pipe during the falling or rebounding process, and the measurement result is invalid. Use a level or similar device to calibrate the hard reference surface to ensure levelness, and place the transparent tube and the frame vertically. 3. Manual reading equipment: On the back of the tube, draw scale lines in an orderly manner, with a large scale every 5% (25mm) and a small scale every 1% (5mm), with an angle of 120° arc. This complete circle marking is an indispensable and important part of the instrument, and it can eliminate parallax errors. Automatic reading device: an instrument that can electronically display the rebound height of the steel ball. It has been verified that the result is the same as the manual reading. The rebound height can be calculated by the rebound speed of the steel ball or the time interval from the first time the steel ball touches the foam surface to the second time. The installed electronic equipment should show an accuracy of ±1% (5mm) of the height. The pipe of the device does not need to be graduated. Method B, testing equipment and main parameters: the same equipment as Method A, the foam falling ball resilience tester, with manual reading equipment and automatic reading equipment. The digital display of the falling ball rebound tester has a relative error of less than 1.5%. The main parameters of the steel ball diameter are the same as those of Method A, and the steel ball mass is 16.3g (0.5g lighter than the 5.1 steel ball). The important different parameters are: the drop height of the steel ball is 460mm±0.5mm. Therefore, the rebound value measured by method A and method B cannot be directly converted. Test sample (polyurethane material): 1. The sample should have parallel and flat surfaces up and down. 2. The sample area is 100mm±100mm, and the height should meet 50m. If the thickness of the sample is less than 50mm, it should be stacked to 50mm, but adhesives cannot be used. For model products, the upper skin should be removed. Note: For soft materials, if the result has a large error, a thicker sample can be used instead of the 50mm thickness limit. For ultra-low-density materials, the test results may be problematic due to the sample itself. For multilayer sheet samples, interlayer sliding is prone to occur. It is best to use a larger area sample to overcome it. Number of samples: 3 samples for each group. Three samples can be taken in the same sample block or in the same batch of different sample blocks. Condition adjustment: After the material is made, it can be tested for at least 72h. If it can be proved, the difference between the result obtained 16h or 48h after production and the result obtained 72h after production does not exceed ±10%. Allow samples to be tested 16h or 48h after production. Before the test, the sample should be adjusted in any of the following environments for more than 16 hours.
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