Cellulose nanocrystals are rod-like and highly crystalline nanoparticles obtained after acid hydrolysis of cellulose fibre. In addition to their low density, high aspect ratio, high specific surface, and chemically reactive surface, this material is well known for its high stiffness and Young’s modulus. Thanks to these particular properties, cellulose nanocrystals can be used as very good reinforcing agent in nanocomposites within a wide variety of applications. Coating is one of the promising applications for nanocellulose composites mainly for barrier applications but also for rigid layer deposition.<br/>Precise methods exist for determination of film mechanical properties. Among them, we count tensile test, dynamic mechanical thermal analysis or three points bending flexural tests. However, these methods are only feasable with thick free-standing films. It has been proved that coating processes modifies CNC organization in nanocomposites. To perfectly understand the effect of cellulose nanocrystals embedded in a polyvinyl alcohol matrix as a coating layer, a strain-Induced elastic buckling instability method has been studied and adapted. The principle of this method is to measure how a rigid material (the tested film) surface wrinkles when it is compressed on a soft substrate (PDMS). This recent method implemented by Stafford (Stafford et al. 2004) has been tried with thin film of nanocellulose composites or (Cranston et al. 2011) in the case of layer by layer method with ultra-thin films corresponding to thicknesses of 35 to 75 nm. However, the adaptation of this method to bar coating systems with micrometrics layers is new and uncertain. In this study it is question to understand the buckling model limits and adaptation for simulate the mechanical properties of a paper coating layer. The second objectives are to study the influence of coating process, paper drying and amount of cellulose nanocrystals on these mechanical properties. First results are promising and clear influence of process parameters can be seen with using this new methodology.

Buckling-based metrology for measuring the Young’s modulus of polyvinyl alcohol – cellulose nanocrystals thin biocomposites layers

255th National Meeting (2018)

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