Kraft lignin as wet-strength and wet-stiffness additives for molded pulp materials

Derived from renewable resources, cellulose based materials are gaining new importance due to their recyclability and biodegradability. Still, one fundamental challenge is their high sensitivity to water. The addition of wet strength agents (WSA) is hence necessary to maintain strength and integrity...

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Main Authors: Eva Pasquier, Jost Ruwoldt
Format: Article
Language:English
Published: KeAi Communications Co., Ltd. 2025-08-01
Series:Journal of Bioresources and Bioproducts
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Online Access:http://www.sciencedirect.com/science/article/pii/S2369969825000337
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author Eva Pasquier
Jost Ruwoldt
author_facet Eva Pasquier
Jost Ruwoldt
author_sort Eva Pasquier
collection DOAJ
description Derived from renewable resources, cellulose based materials are gaining new importance due to their recyclability and biodegradability. Still, one fundamental challenge is their high sensitivity to water. The addition of wet strength agents (WSA) is hence necessary to maintain strength and integrity in humid or wet conditions. In this article, technical lignin was used as WSA in bleached kraft pulp, which was thermopressed to materials with the potential to replace plastics. Cationic starch or a cationic flocculant (PCB 20) was used as a retention aid during the filtration process. The effect of moisture during thermopressing and lignin particle size were also studied. The results showed that elevated moisture during pressing had the biggest impact both on dry and wet strength. Wet strength (tensile test), up to 9 MPa, and wet strength retention, up to 12 %, were obtained when moisture was present during pressing. However, the type of flocculant and the size of the lignin particles also had a limited effect on the strength. Wet strength improvement was most probably due to the plasticization of lignin at high temperatures, which was further aided by water. The cellulose-lignin network was strengthened by the melting of lignin, consolidating the network after cooling. The wet stiffness of the cellulose substrates was also increased from 200 to 938 MPa in the presence of lignin, while the elongation was maintained and no embrittlement was observed. The results in this article might hence pave the way for new developments in molded pulp and cellulose based plastics replacement.
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publisher KeAi Communications Co., Ltd.
record_format Article
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spelling doaj-art-5ab1bacbf1fd432cbea71d41f508bf812025-08-20T03:39:10ZengKeAi Communications Co., Ltd.Journal of Bioresources and Bioproducts2369-96982025-08-0110332533510.1016/j.jobab.2025.05.001Kraft lignin as wet-strength and wet-stiffness additives for molded pulp materialsEva Pasquier0Jost Ruwoldt1RISE PFI AS, Høgskoleringen 6B, Trondheim 7491, NorwayCorresponding author.; RISE PFI AS, Høgskoleringen 6B, Trondheim 7491, NorwayDerived from renewable resources, cellulose based materials are gaining new importance due to their recyclability and biodegradability. Still, one fundamental challenge is their high sensitivity to water. The addition of wet strength agents (WSA) is hence necessary to maintain strength and integrity in humid or wet conditions. In this article, technical lignin was used as WSA in bleached kraft pulp, which was thermopressed to materials with the potential to replace plastics. Cationic starch or a cationic flocculant (PCB 20) was used as a retention aid during the filtration process. The effect of moisture during thermopressing and lignin particle size were also studied. The results showed that elevated moisture during pressing had the biggest impact both on dry and wet strength. Wet strength (tensile test), up to 9 MPa, and wet strength retention, up to 12 %, were obtained when moisture was present during pressing. However, the type of flocculant and the size of the lignin particles also had a limited effect on the strength. Wet strength improvement was most probably due to the plasticization of lignin at high temperatures, which was further aided by water. The cellulose-lignin network was strengthened by the melting of lignin, consolidating the network after cooling. The wet stiffness of the cellulose substrates was also increased from 200 to 938 MPa in the presence of lignin, while the elongation was maintained and no embrittlement was observed. The results in this article might hence pave the way for new developments in molded pulp and cellulose based plastics replacement.http://www.sciencedirect.com/science/article/pii/S2369969825000337LigninMolded pulpWet strength agentLignin nanoparticlesPaper sizingAdded-lignin thermoformed pulps
spellingShingle Eva Pasquier
Jost Ruwoldt
Kraft lignin as wet-strength and wet-stiffness additives for molded pulp materials
Journal of Bioresources and Bioproducts
Lignin
Molded pulp
Wet strength agent
Lignin nanoparticles
Paper sizing
Added-lignin thermoformed pulps
title Kraft lignin as wet-strength and wet-stiffness additives for molded pulp materials
title_full Kraft lignin as wet-strength and wet-stiffness additives for molded pulp materials
title_fullStr Kraft lignin as wet-strength and wet-stiffness additives for molded pulp materials
title_full_unstemmed Kraft lignin as wet-strength and wet-stiffness additives for molded pulp materials
title_short Kraft lignin as wet-strength and wet-stiffness additives for molded pulp materials
title_sort kraft lignin as wet strength and wet stiffness additives for molded pulp materials
topic Lignin
Molded pulp
Wet strength agent
Lignin nanoparticles
Paper sizing
Added-lignin thermoformed pulps
url http://www.sciencedirect.com/science/article/pii/S2369969825000337
work_keys_str_mv AT evapasquier kraftligninaswetstrengthandwetstiffnessadditivesformoldedpulpmaterials
AT jostruwoldt kraftligninaswetstrengthandwetstiffnessadditivesformoldedpulpmaterials