ASTM D2856-94(1998)

1.1 Cellular plastics are composed of the membranes or walls of polymer separating small cavities or cells. These cells may be interconnecting (open cell), non-connecting (closed cell), or any combination of these types. This test method determines numerical values for open cells. It is a porosity determination, measuring the accessible cellular volume of a material. The volume occupied by closed cells is considered to 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.

1.2 This test method consists of three procedures:

1.2.1 Procedure A , designed to correct for cells opened during sample preparation, by measuring cell diameter, calculating, and allowing for surface volume;

1.2.2 Procedure B , 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, and

1.2.3 Procedure C , which does not correct for cells opened during sample preparation and gives good accuracy on predominantly highly open-celled materials. The accuracy decreases as the closed cell content increases and as the cell size increases.

1.3 The values as stated in SI units are to be regarded as the standard. The values in parentheses are given for information only.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Notes 2, 4, and 8.

Note 1-This test method and ISO 4590-1981 use the same basic principles but are significantly different in experimental detail.