Air Flow vs Differential Pressure

Test Description:
The air flow test provides information concerning a material’s resistance to air flow. Because air flow resistance is influenced by the material’s porosity, air flow tests are often times substituted for the more time-intensive mercury intrusion or capillary flow test.

Characterization of air flow resistance can take place at one specified air flow rate, or alternatively, air flow resistance can be specified over a range of air flow rates. Typically air flow resistance is referenced in terms of differential pressure--the difference in pressure across the porous material--at a specified air flow rate.

As air flow rates increase or as air flow resistance increases in the porous material, differential pressure increases as well. Similarly, as pore size and pore volume decrease, or as material thickness increases, air flow resistance will increase. The air flow instrument used in this test complies with the following test standards: AFNOR G 07-111, ASTM D 737, BS 5,636, DIN 53,887, EDANA 140.1, ISO 9,237, JIS L 1096-A, TAPPI T 251.

Test Method:
ASTM-D 737
Fluid: Air
Material. Sample Size: 5.89 in / 38 cm
Temperature: Ambient
Geometry: Flat Sheet