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Thermoporosimetry is a calorimetric method that allows the measurement of the pore size distribution (PSD). The method measures the melting or freezing point depression of a liquid trapped in a pore. Then, this melting/freezing point depression is correlated to the pore size by the Gibbs-Thomson coefficient. Thermoporosimetry has several advantages. For example, it does not require toxic chemicals. Compared to other methods, the sample preparation is relatively simple. Moreover, samples analysis occurs in wet-state. However, the application of thermoporosimetry to cellulosic materials presents some critical limitations. Instead of using pulp fibers, the Gibbs-Thomson coefficients are calculated from materials with a different porosity, such as, silica or controlled porous glass material. This might provide misleading pore information. Thus, the primary aim of this work was to overcome this limitation. By combining cyclohexane thermoporosimetry and Hg-porosimetry, a system for determining an alternative Gibbs- Thomson coefficient was presented for a set of five types of pulps. These included bleached/unbleached, hardwood/softwood, and dried/never dried fibers. Additionally, by combining thermoporosimetry and centrifugation method, a novel platform was developed to estimate the amount of true macropores in fiber cell wall. In conclusion, a framework for calculating ‘corrected’ Gibbs-Thomson coefficient for thermoporosimetry-based PSD determination in cellulose-cyclohexane system was demonstrated in this study. Furthermore, thermoporosimetry was applied to quantify fiber cell wall macropores.

The recent expansion and diversification of cellulose-based products market has created the need for a more accurate pulp characterization, and new parameters have been developed, including cellulose and pulp reactivity. Cellulose reactivity has been often described as the ability degree of the reactive hydroxyl groups within the polysaccharide to react with chemicals, and it has been estimated by means of complex, time-consuming methods. Many studies have utilized these estimations as representative values of pulp reactivity. However, this approach is questionable, because the latter depends not only upon cellulose reactivity, but also on other parameters. Thus, the aim of this work was to develop an alternative fast user-friendly procedure to estimate pulp reactivity as such. This novel evaluation method was based on the monitoring of pulp dissolution in a bis (ethylenediamine) copper (II) hydroxide solution (CED) at constant measurement conditions using a rheometer equipped with a bob-and-vane geometry. Torque values were first measured throughout the reaction and then plotted as function of time. The resulting torque profile was found to consist of four phases: torque decrement, linear increment, non-linear increment, and the plateau. The dissolution began with the linear phase and ended with the plateau value. Based on the analysis of the profile, three parameters were identified as best representing pulp reactivity: pre-dissolution time (PDT), initial dissolution rate (IDR), and optimal dissolution time (ODT). The first estimated the accessibility of CED to the pulp, while the second and the third evaluated pulp reactivity as such. In particular, high IDRs and low ODTs were found to correspond to high pulp reactivities, though these two parameters were not directly proportional. In order to optimize the method, the experiments were organized in two parts. The first evaluated the measurement conditions affecting the results and allowed the standardization of th