I want to measure the Specific Surface Area, Pore Volume and Pore Diameter of a piece of paper and I wonder what the proper method is for doing that.
I previously used BET N2 adsorption/desorption for powdered samples but I'm not sure if that's going to work well with the sheet-like samples as well.
I appreciate any possible insights on this matter.
Quite hard, since the paper is not porous. Usually non-porous samples result in very low accuracy unless the surface area is high.
The main issues are the following ones:
-Low textural properties (porous volumes etc.) => not really suitable or LN2 adsorption
-Paper(s) is(are) mainly macroporous (i.e. > 50 nm) => gas sorption is not very adapted for such pore sizes ranges
-Cellulose (cristalline and amorphous) and hemicelluloses can possibly aBsorb and not only aDsorb LN2 at 77K=> specific area can be overestimated
-The porous network can be flexible=> texture changes due capillary forces/constraints during adsorption measurement
Thus, BET estimation on paper and paper like materials, through LN2 adsorption measurement, can gives informations that are, at most, "semi-quantitatives".
Ellipsometry, microscopy, microtomography and Hg promosimetry (still some problems of porous network flexibility for the latter one) could be other options.
Measuring the specific surface area, pore volume, and pore diameter of a piece of paper can be challenging, especially if you are dealing with a sheet-like sample. However, there are several methods that can be used to determine these properties.
One common method for measuring the specific surface area of a material is the BET (Brunauer-Emmett-Teller) method, which you have used before for powdered samples. This method involves measuring the amount of gas adsorbed onto the surface of the sample at different pressures, and then using this data to calculate the specific surface area. While the BET method can be used for sheet-like samples, it may require modifications to the experimental setup to accommodate the sample geometry.
Another method that can be used to measure the specific surface area of a sheet-like sample is the Gurley method, which involves measuring the time required for air to pass through the sample under a specific pressure differential. The specific surface area can then be calculated from the air permeability data.
To measure the pore volume and pore diameter of a paper sample, you may want to consider using mercury intrusion porosimetry (MIP). This method involves applying a pressure differential to the sample while it is submerged in mercury, which allows the mercury to intrude into the pores and pores of the sample. By measuring the pressure required for mercury to intrude into the pores and the amount of mercury intruded, the pore volume and pore size distribution can be calculated.
Another method for determining the pore size distribution of a paper sample is capillary flow porometry (CFP). This method uses a wetting liquid to fill the pores and pores of the sample, and then measures the pressure required for the liquid to flow through the sample. The pore size distribution can be calculated from the pressure-flow data.
Overall, the method you choose will depend on the specific properties of your sample and the equipment you have available. It is recommended to consult with an expert in the field or to perform a literature search to determine the most appropriate method for your specific application.
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