ISO 8307:2018 pdf download – Flexible cellular polymeric materials -Determination of resilience by ball rebound
ISO 8307:2018 pdf download – Flexible cellular polymeric materials -Determination of resilience by ball rebound.
6 Test pieces
6,1 The test pieces shall have plane, parallel top and bottom surfaces.
6.2 The test pieces shall consist of the entire product sample or a suitable portion of it. except that in no case shall the thickness he less than 50 mm or the area les than 100 mm 100 mm. Test pieces less than 50 mm thick shall be plied up, without the use of cement, to a minimum of 50 mm. For moulded products, the top skin shall be removed.
Thicker test pieces can be used to avoid spurious results, which can occur with very soft materials due to the Influence of the baseplate.
NOTE The minimum test piece thickness of 50 mm cannot be sufficient for very soft materials: if spunous results are obtained, a thicker test piece can be used. Very low density materials can also cause problems due to rebound of the test piece itself With multiple-ply test pieces, slipping can occur between the plies. This problem can be overcome by using the largest possible area of the test piece.
7 Number of test pieces
Three est petes pee sample shall be tested. The three test pieces may be obtained by using separate items or different locations on a given item.
8 Test conditions and conditioning
Material shall be tested not less than 72 h after manufacture. unless, at either 16 h or 48 h after manufacture, it can be demonstrated that the mean rebound resilience values obtained do not differ by more than ±10 % from those obtained after 72 h. Testing is permitted at either 16 h or 48 h if. at the selected time, the above criterion has been satisfied.
Prior to the test, the test pieces shall be conditioned undeflected and undistorted for at least 16 h in one of the following atmospheres as given in ISO 23529:
— 23 ec ± 2 °C, (50 ± 5) % relative humidity;
— 27°C ± 2 °C, (65 ± 5) % relative humidity.
This period can form the latter part of the period following manufacture.
In the case of quality-control tests, test pieces can be taken a shorter time (down to a minimum of 12 h) after manufacture and testing carried nut after conditioning for a shorter period (down to a minimum of 6 h) in one of the atmospheres specified above.
9.2 Test method
9.2.1 Carry out the test in the atmosphere described in Clause 8 immediately after conditioning the test pieces in the same atmosphere.
9.2.2 Centre the test piece at the base of the tube (see Clause 5) and adjust the height of the tube so that zero rebound is 16 mm ± 0.5 mm above the surface of the test piece. Clamp the tube to make light contact with the test pieces without causing visible compression.
9.2.3 Mount the steel ball on the release mechanism, then drop it and note the maximum rebound height to the nearest percentage point, lithe ball strikes the tube on the drop or rebound, the value obtained is invalid. This condition Is usually due to the tube not being vertical or to Irregularities on the test piece surface. In order to minimize parallax error, the eye-level of the observer shall be such that the markings on the tube in the region where the percentage rebound value is read appear as straight lines. Trial drops might be necessary using spare samples of the same cellular material to establish the correct eye-level prior to performing final measurements.
9.2.4 At least three rebound values in succession within 1 mm shall be obtained on each of the three test pieces. To obtain best possible precision for viscoelastic (slow recovery) foams, each drop shall be performed at a new location on the test piece surface. This applies to foam of ball resilience of less than 15%.
10 Expression of results
For each test piece, determine the median of the three rebound height values, expressed as % value. If any value deviates by more than 20 % (one.fihIh) of the median value from the median, make two additional drops and determine the median for all five rebound height values. Using the median values obtained for the three test pieces, determine the overall median value as the rebound resilience value of the material.
If automated measurement is employed, the results shall also be expressed to the nearest integer.
At the present time, precision data are not available for this test method.
12 Test report
The test report shall include the following information:
a) a reference to this document (i.e. ISO 8307:2018);
b) a description of the material tested, Including whether open•cell or closedcelI as defined In Clause3
c) the temperature and humidity at which the test piece was conditioned and tested;
d) the thickness of the test piece (in mm);
e) whether or not electronic measurement was used;
f) the rebound resilience value as the median of the three test piece medians;
g) the individual rebound height values of the three (or five) tests per test piece;
h) the material lot number or date of manufacture;