2.4. Heat of Wetting

Calorimetry is a thermodynamic method that provides the determination heat effect of the interaction of cellulose samples with various liquids. For this study, various types of calorimeters and microcalorimeters can be used [34]. The standard heat effect of interaction is measured at 25 °C and pressure of 1 atm. The experiments show that the interaction of dry cellulose samples with water at standard conditions is accompanied by the exothermic heat of wetting (Q). Because the interaction with water is carried out in non-crystalline domains (NCD) of cellulose, the heat of wetting is directly proportional to a fraction (Y) of NCD in the cellulose sample:

where Q_o = 168 J/g is the maximum heat of wetting for completely amorphous cellulose in a dry state and Y is the degree of amorphicity.