Nanocellulose films and coatings are among the front-running candidates for various applications ranging from biodegradable packaging to flexible electronics, which can be attributed to their excellent strength and barrier properties along with the functionalization ability. Until now, production of such films and coatings has been possible only by using nanocellulose suspensions at low consistencies (0.1-3%), because their viscosity and yield stress at higher concentrations lead to processing challenges. During film production, these dilute suspensions demand an enormous drying capacity, and such large drying sections are often not feasible to build in a continuous process. Hence, low line speeds are used to ensure complete drying using the existing capacity. The slow speeds of these processes cast doubt on their economic viability and potential upscalability.<br/>Usage of high consistency nanocellulose suspensions can help overcome the drying challenge provided their processability into films and coatings can be ensured. However, increasing the solids content generally gives these suspensions a paste-like character with high viscosity and yield stress, which makes it difficult to handle them using the conventional film forming processes. Moreover, the paste-like material brings new challenges related to mixing, pumping, entrapped air bubbles, etc. Therefore, it is essential to understand and modify the rheological behavior of these paste-like suspensions, so that they can be suitable for processing into films and coatings. In this work, we characterize the rheology of high consistency nanocellulose suspensions. Furthermore, we present novel ideas for tuning their rheological behavior to ease their large-scale processing into films and coatings. A combination of additives along with high shear treatment is utilized to modify the rheology and improve the film forming properties of high consistency nanocellulose suspensions. The approaches developed in this work show promise in enabling the use of nanocellulose in large-scale film/coating production.

Large-scale processing of nanocellulose into films and coatings: Challenges and prospects

2019 Spring National Meeting

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