scope:

Cellular plastics are composed of thin membranes or walls of polymer, separating small cavities or cells. The cells may be largely interconnecting (open cell), largely nonconnecting (closed cell), or any combination. It is the purpose of this method to determine numerical values for the percentage of volume occupied by open cells. The percentage of volume occupied by closed cells will also include cell walls.

Since any conveniently sized specimen can only be obtained by some cutting operation, a fraction of the closed cells will be opened during sample preparation and' will be included as open cells. Procedure A of this method is designed to correct for cells opened during sample preparation by measuring the cell diameter, calculating, and allowing for surface volume. Procedure B is designed to correct for cells opened in sample preparation by cutting and exposing new surface area equal to the surface area of the original sample dimension (Note 2). Procedure C does not correct for cells opened during sample preparation and gives good accuracy on highly open celled materials. The accuracy decreases as the closed cell content increases and as the cell size increases.

NOTE 1-The values stated in U.S. customary units are to be regarded as the standard. The metric equivalents of U.S. customary units may be approximate.

NOTE 2-The procedure used is determined by the definition of "open cell." In Procedure A, open cell is defined as any cavity of two or more cells interconnected by broken, punctured, or missing cell walls allowing free passage of any internal gases. Procedure B defines open cells as all cells open to the surface of the test specimen and freely accessible to the atmosphere.