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Article

Lignin Inter-Diffusion Underlying Improved Mechanical Performance of Hot-Pressed Paper Webs

1
Department of Chemical Engineering, Mid Sweden University, SE-85170 Sundsvall, Sweden
2
MoRe Research Örnsköldsvik AB, Box 70, SE-89122 Örnsköldsvik, Sweden
3
Department of Physics, University of Jyvaskyla, P.O. Box 35, FI-40014 Jyvaskyla, Finland
4
VTT Technical Research Centre of Finland Ltd., P.O. Box 1000, FI-02044 Espoo, Finland
*
Author to whom correspondence should be addressed.
Academic Editors: Domenico Acierno and Antonella Patti
Polymers 2021, 13(15), 2485; https://doi.org/10.3390/polym13152485
Received: 3 July 2021 / Revised: 21 July 2021 / Accepted: 23 July 2021 / Published: 28 July 2021
(This article belongs to the Special Issue Mechanical Performance of Sustainable Bio-Based Compounds)
Broader use of bio-based fibres in packaging becomes possible when the mechanical properties of fibre materials exceed those of conventional paperboard. Hot-pressing provides an efficient method to improve both the wet and dry strength of lignin-containing paper webs. Here we study varied pressing conditions for webs formed with thermomechanical pulp (TMP). The results are compared against similar data for a wide range of other fibre types. In addition to standard strength and structural measurements, we characterise the induced structural changes with X-ray microtomography and scanning electron microscopy. The wet strength generally increases monotonously up to a very high pressing temperature of 270 °C. The stronger bonding of wet fibres can be explained by the inter-diffusion of lignin macromolecules with an activation energy around 26 kJ mol−1 after lignin softening. The associated exponential acceleration of diffusion with temperature dominates over other factors such as process dynamics or final material density in setting wet strength. The optimum pressing temperature for dry strength is generally lower, around 200 °C, beyond which hemicellulose degradation begins. By varying the solids content prior to hot-pressing for the TMP sheets, the highest wet strength is achieved for the completely dry web, while no strong correlation was observed for the dry strength. View Full-Text
Keywords: hot-pressing; paper web; fibre; lignin; diffusion; activation energy hot-pressing; paper web; fibre; lignin; diffusion; activation energy
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MDPI and ACS Style

Mattsson, A.; Joelsson, T.; Miettinen, A.; Ketoja, J.A.; Pettersson, G.; Engstrand, P. Lignin Inter-Diffusion Underlying Improved Mechanical Performance of Hot-Pressed Paper Webs. Polymers 2021, 13, 2485. https://doi.org/10.3390/polym13152485

AMA Style

Mattsson A, Joelsson T, Miettinen A, Ketoja JA, Pettersson G, Engstrand P. Lignin Inter-Diffusion Underlying Improved Mechanical Performance of Hot-Pressed Paper Webs. Polymers. 2021; 13(15):2485. https://doi.org/10.3390/polym13152485

Chicago/Turabian Style

Mattsson, Amanda, Tove Joelsson, Arttu Miettinen, Jukka A. Ketoja, Gunilla Pettersson, and Per Engstrand. 2021. "Lignin Inter-Diffusion Underlying Improved Mechanical Performance of Hot-Pressed Paper Webs" Polymers 13, no. 15: 2485. https://doi.org/10.3390/polym13152485

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