Methods for determining porosity

Here I provide a testing method for PAN yarns for your reference: Method for testing porosity and pore radius. The apparent physical water in the water-swollen PAN solidified yarns is removed by centrifugation, and the water remaining in the yarns can be used to characterize the pore structure and pore volume of the yarns. The pore structure and pore volume of the solidified filaments are also closely related to the fiberization conditions. The ratio of the swelling degree of the bath-drawn yarn after hot water drawing to that of the solidified yarn can also be used to evaluate the conditions of hot water drawing and to provide a rough estimate of the subsequent oiling dosage. The coagulation bath or the filaments obtained from it are subjected to a water bath, after which structural fixation is achieved using liquid nitrogen freeze-drying. Accurately weigh 0.2 g of the dried sample and place it in an expansimeter; then use a mercury injection device to create a vacuum inside the container (below 0.05 torr). After that, fill it with mercury and measure it using a porosity meter. The pore volume is measured by the amount of mercury pressed in. The maximum pressure is 3000 bar. Porosity is calculated using the following formula: Porosity = V/(V+M), where M is the volume of the sample and V is the volume of the pores. πr²p = 2πrσcosθ, with σ being the surface tension of mercury (480 dyne/cm), r being the radius of the pores (Å), θ being the contact angle (140°), and p being the pressure (0–2000 Kg/cm²). By substituting these values, the radius of the pores r is given by: r = **×10⁴/p (Å) = 75000/p (Å)

Let me mention a few methods I know: Direct method: If the density of the sample and the density of the material from which the sample is made are known, it is possible to calculate it directly. Mercury pressure method: Mercury is forced into the porous medium to replace the air in the pores; by measuring the difference in mass of the sample before and after the mercury is inserted, the volume of the pores can be calculated. Dividing this value by the external volume gives the porosity. Inhalation method: The sample is placed in a vacuum chamber, which is then evacuated; saturated water vapor is introduced into the chamber, filling the voids in the porous medium. The principle is similar to that of the mercury intrusion method.

Thank you very much. I was wondering if anyone knows the porosity values of the resin packing used in ion exchange membrane resin towers