Abstract
There is an ever-increasing interest toward utilizing nanocellulose as barrier coatings and films, and recent studies have underlined the efficiency of using innovative fibrillation processes such as twin-screw extrusion with an enzymatic pretreatment for producing nanocellulose suspensions with solid contents as high as 20 wt %, which can lead to faster coating speeds and reduced drying energy costs. The current work aims at understanding the factors that influence high-throughput processability of high-solid-content nanocellulose during roll-to-roll coating. The rheological properties of 12.5, 10, and 7.5 wt % suspensions were evaluated across a wide range of shear rates and geometries (rotational, pipe, and slot). The influence of dispersants [carboxymethyl cellulose (CMC) and sodium polyacrylate (NaPA)] on the rheology and coating quality was assessed. A Casson-power-cross model is proposed to explain the rheological behavior across a wide shear rate range and is used to predict useful parameters, viz., yield stress, transition shear rate, and power-law index at high shear rates. Finally, a 12.5 wt % nanocellulose suspension with CMC or NaPA dispersant was roll-to-roll-coated on paperboard using a slot-die applicator. CMC addition had a positive influence on the yield stress, thixotropy, and water release and, therefore, resulted in a better mineral oil and grease barrier of the coated samples compared to the rest.
Original language | English |
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Pages (from-to) | 11302–11313 |
Journal | ACS Applied Nano Materials |
Volume | 5 |
Issue number | 8 |
DOIs | |
Publication status | Published - 26 Aug 2022 |
MoE publication type | A1 Journal article-refereed |
Funding
R.K. received funding from Åbo Akademi University Graduate School in Chemical Engineering, Magnus Ehrnrooth Foundation, Finnish Forest Products Engineers Association, and Walter Ahlström Foundation. G.B. performed the experiments at LGP2 (Université Grenoble Alpes), which is part of the LabEx Tec 21 (Investissements d’Avenir; Grant ANR-11-LABX-0030) and of PolyNat Carnot Institute (Investissements d’Avenir; Grant ANR-16-CARN-0025–01). The authors gratefully thank the Association Nationale Recherche Technologie and Arjowiggins France SAS for financial and material support.
Keywords
- barrier coatings
- enzymatic pretreatment
- nanocellulose
- rheology
- roll-to-roll coating