Corrected Gibbs-Thomson coefficient for the cellulose-cyclohexane system

Abstract

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.