Pore Size and Structural Defects

A commonly used simple method for determining if there are any cracks or pinholes in microporous membranes is the so-caUed bubble point test. It has been used by many organic membrane manufacturers and users alike and is also being adopted by some inorganic membrane manufacturers. The method utilizes the Washburn equation 

This method in principle can also be used to estimate the average pore size of the membrane when there are no defects in the membrane. First, gas flows through the membrane in the dry state. Typically, the gas flow rate is a linear function of the applied pressure difference. Then the membrane is saturated with the test liquid and the gas is forced to flow through the wet 

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