Cellulose nanomaterials (CNMs), building blocks of the plant cell walls, are a catalyst for sustainable materials engineering. Their unique combination of characteristics – renewable, biodegradable/recyclable, and high performance across a broad range of properties, position them well as the next alternatives to non-degradable plastics. CNMs are produced globally at industrial scale, yet they remain absent from the US market. End-users remain hesitant in using these nanomaterials, probably due to their high costs (esp. for large volume, low cost commodities), not (yet) approved environmental, health and safety policies, and/or lack of end-user guidelines. They may also be confused by the different grades of CNMs that result from a multitude of production routes and diversed (ligno)cellulosic sources. To contribute towards this "end-users" challenge, and start drafting the guidelines of good practices of CNM utilization and application, one may focus on understanding the structure-processing-properties relationships of CNMs, at a deeper level. In this research, we investigated the structure-processing-properties relationships of cellulose nanofibrils (CNFs) produced by aqueous counter collision (ACC). This high-shear mechanical treatment can nanofibrillate (ligno)cellulosic fiber suspensions at high pressure and velocity, through two geometries: a 100-micrometer nozzle, followed by collision of the fiber jet with a ceramic ball. Aqueous suspensions of CNFs of 15-20 nm in widths can thus be obtained. Using a design of experiment (DOE) and surface response methodology, we optimized the ACC processing conditions in order to produce CNF films with the highest mechanical strength and the lowest water vapor permeability for their end-use as barrier packaging substrates. The overall goal is to optimize the processing step so as to produce a starting CNF material that shows the highest feasible performance - i.e., feasible by mechanical route solely - for barrier packaging application. In this presentation, we will present the methodology and the experimental vs predicted results from the DOE. Interestingly, the surface responses for tensile strength and water vapor permeability differed significantly. This result will be analyzed and discussed with respect to the processing conditions, CNF properties and films' structure. The next steps for producing and identifying so-called "high-quality" grade CNFs for barrier packaging applications will finally be proposed.

Deciphering the structure-processing-properties relationships of cellulose nanofibrils produced by aqueous counter collision

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