FoamPyc Options

Explanation of the different methods applicable to analyzing foams.

Correction Using Cell Dimensions

Measures the closed cell fraction and corrects for the cells that were damaged while cutting the sample to the necessary size and shape. This is accomplished by using either the average cell diameter or the cell chord length (as defined in ASTM method D-6226) and the measurements of the sample to determine the volume of the cut cells. This volume is deducted from the total volume of the open cells measured by the pycnometer.

Correction by Recutting Sample

Corrects for the cut cells by using two separate measurements. For the second measurement, the sample is recut to double the amount of cut surface. The observed difference in cut open cell volume is applied as a correction to the initial measured volume. This method offers the distinct advantage that no assumptions are needed about the relative amounts of open and closed cells.

No Correction

Does not correct for cut cells. It is used for materials with predominantly open cells where good accuracy can be achieved without correction. The accuracy level deteriorates as the percentage of closed cells increases.

Compressibility Test

The fill pressure is increased incrementally over the sample with each repeat of the P1, P2 cycle (where P1 is the initial pressure to which the sample is charged, and P2 the final pressure after expansion). The apparent variation of the measured sample volume with the average pressure is determined.

 

This test is an approximate indication. It is not intended to be an exact measure of volume compressibility. If you want to see whether compressibility is reversible for your sample, use sample fill direction. If not, reference fill direction is recommended.

Cell Fracture Test

A perfectly rigid foam is assumed. First, a P1, P2 cycle is performed at the lower of two specified P1 pressures, and the results stored. A second cycle is performed at a higher specified value of P1, then a third cycle identical to the first cycle is performed.

 

The difference between the volume of the sample on the first measurement and on the third measurement is reported as the volume of fractured cells. It is assumed that cells fracture by exposure to the highest pressure (second cycle) so that when the third measurement is made, the measured sample volume has decreased from the first cycle by the amount of the closed cell volume which was fractured.