Comparison of NMR Cryoporometry, Mercury Intrusion Porosimetry, and DSC Thermoporosimetry in Characterizing Pore Size Distributions of Compressed Finely Ground Calcium Carbonate Structures

Abstract

This work investigates for the first time how mercury intrusion porosimetry (MIP), NMR-based cryoporometry, and DSC-based thermoporosimetry compare in revealing the porous characteristics of ground calcium carbonate structures compacted over a range of pressures. The comparison is made using the same source samples throughout. MIP, a much-used method in the characterization of porous structures, has the drawback that the high pressure needed to intrude the mercury may either distort the skeletal porous structure of the sample, especially when compressible materials such as cellulose or binders/latex are present, or lead to a reduction in the measured number of large pores due to the shielding by smaller pores. These effects have previously been addressed using bulk modulus corrections and by modeling the structure permeability to account for the potential shielding. Cryoporometry gives detailed information about the pore size distribution of an imbibition saturated structure. Thermoporosimetry is a relatively new candidate in this field, and it yields both pore size distribution and pore volume. Currently it is somewhat limited in the pore size range detectable, but it is relevant to pigmented coatings. Its potential is identified for capturing the pores involved in the progress of imbibition before saturation is reached.

Proposed Nano-Scale Coalescence of Cellulose in Chemical Pulp Fibers During Technical Treatments

“…The different methods give approximately the same accuracy with respect to the pore sizes (Gane et al 2004). However, caution must be taken when comparing the values obtained by different methods, as the actual values differ between the methods depending on, e.g., the material analyzed (Gane et al 2004). All of the methods assume that the pores are cylindrical or spherical, which is a limitation to these measurements.…”

“…We cover here some of these methods commonly applied for cellulosic materials, e.g., thermoporosimetry conducted with differential scanning calorimetry (DSC) by the isothermal melting technique (Maloney and Paulapuro 1998;Wang et al 2003), DSC combined with a TGA (Park et al 2006b), NMR cryoporosimetry (Gane et al 2004;Östlund et al 2010), and inverse size-exclusion chromatography (ISEC) (Berthold and Salmén 1997). The different methods give approximately the same accuracy with respect to the pore sizes (Gane et al 2004). However, caution must be taken when comparing the values obtained by different methods, as the actual values differ between the methods depending on, e.g., the material analyzed (Gane et al 2004).…”

“…NMR cryoporosimetry follows the same principal as the DSC thermoporosimetry (Gane et al 2004;Petrov and Furó 2009;Östlund et al 2010). In NMR cryoporosimetry, the water-swollen samples are frozen and then melted stepwise.…”

Nuclear magnetic resonance cryoporometry

“…The NMR cryoporometry measurement indicated a significantly increased minimum pore diameter in the 6 nm silica sample due to the large non-frozen surface layer associated with the naphthalene preventing the smallest pores from being measured . Comparisons have also been made between NMR cryoporometry, MIP, and DSC thermoporosimetry in calcium carbonate structures (Gane et al, 2004).…”

Thermoporosimetry of hard (silica) and soft (cellulosic) materials by isothermal step melting

“…Thermoporosimetry has been used to measure the PSD of many kinds of mesoporous materials such as ridged inorganic materials [2,3] and soft polymer matrix materials [4][5][6][7][8][9]. Many thermoporosimetric studies are based on a continuous methodology in which a sample is heated at a constant rate over the melting transition.…”