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Deaggregation of cellulose macrofibrils and its effect on bound water

Thaddeus Maloney, Josphat Phiri, Aleksi Zitting, Antti Paajanen, Paavo Penttilä, Sara Ceccherini




Abstract: The purpose of this study was to determine how to control and measure the hierarchical swelling in pulp fibers via electrostatic interactions and localized osmotic pressure. A eutectic solvent system was used to systematically increase phosphate groups in the cell wall. Increase in fiber charge led to an increase in swelling properties, as expected. At a charge value around 180–200 μmol/g the macrofibrils were found to deaggregate. This led to a large jump in mesoscale swelling, from 0.9 to 2.5 mL/g, and surface area, from 400 to 1000 m2/g. This deaggregation was confirmed with X-ray scattering and solute exclusion.


A novel thermoporosimetry method was used in the study. This involved splitting the nonfreezing water into two subfractions, thus allowing a more complete analysis of pore structure and surface area. The hydrated surface area for the samples was in the range 1200–1400 m2/g, which agreed well with simulations of aggregated microfibrils. Adding charge to the pulp fibers had a nonlinear effect on handsheet strength properties. This suggests that hierarchical control of fiber swelling may be a useful approach to improve important property pairs such as strength/density in packaging and other commercially important fiber products.



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