Time-triggered calcium ion bridging in preparation of films of oxidized microfibrillated cellulose and pulp

Pegah Khanjani; Matti Ristolainen; Harri Kosonen; Pasi Virtanen; Sara Ceccherini; Thaddeus Maloney; Tapani Vuorinen

doi:10.1016/j.carbpol.2019.04.060

Time-triggered calcium ion bridging in preparation of films of oxidized microfibrillated cellulose and pulp

Carbohydr Polym. 2019 Aug 15:218:63-67. doi: 10.1016/j.carbpol.2019.04.060. Epub 2019 Apr 18.

Authors

Pegah Khanjani¹, Matti Ristolainen², Harri Kosonen³, Pasi Virtanen⁴, Sara Ceccherini⁵, Thaddeus Maloney⁶, Tapani Vuorinen⁷

Affiliations

¹ Aalto University, School of Chemical Engineering, Department of Bioproducts and Biosystems, P.O. Box 16300, Aalto, 00076, Finland. Electronic address: pegah.khanjani@aalto.fi.
² UPM Research Center, FIN-53200, Lappeenranta, Finland. Electronic address: matti.ristolainen@upm.com.
³ UPM Research Center, FIN-53200, Lappeenranta, Finland. Electronic address: harri.kosonen@upm.com.
⁴ UPM Research Center, FIN-53200, Lappeenranta, Finland. Electronic address: pasi.virtanen@upm.com.
⁵ Aalto University, School of Chemical Engineering, Department of Bioproducts and Biosystems, P.O. Box 16300, Aalto, 00076, Finland. Electronic address: sara.ceccherini@aalto.fi.
⁶ Aalto University, School of Chemical Engineering, Department of Bioproducts and Biosystems, P.O. Box 16300, Aalto, 00076, Finland. Electronic address: thaddeus.maloney@aalto.fi.
⁷ Aalto University, School of Chemical Engineering, Department of Bioproducts and Biosystems, P.O. Box 16300, Aalto, 00076, Finland. Electronic address: tapani.vuorinen@aalto.fi.

PMID: 31221344
DOI: 10.1016/j.carbpol.2019.04.060

Abstract

One of the main trends in developing bio-based materials is to improve their mechanical and physical properties using MFC derived from sustainable natural sources and compatible low-cost chemicals. The strength of anionic MFC based materials can be increased with addition of multivalent cations. However, direct mixing of solutions of multivalent cations with oxidized MFC may result in immediate, uncontrollable fibril aggregation and flock formation. The aim of this study was to design a method where Ca²⁺ ions liberate from solid CaCO₃ particles on bleached hardwood (birch) kraft pulp, which was mixed with oxidized MFC and crosslink it to tailor the mechanical properties of the dried structure. In few minutes after adding acetic anhydride, pH of the wet film dropped from 7.3-4.8 through liberation of acetic acid and CaCO₃ particles solubilized releasing Ca²⁺. The novel method could be applied on industrial scale for improving the performance of packaging materials.

Keywords: Acetic anhydride; Bleached hardwood kraft pulp; Cellulose film; Oxidized microfibrillated cellulose; Precipitated calcium carbonate; Tensile testing.