Cellulose nanocrystals as reinforcements in thermoplastic Composites: effect of processing route on dispersion
Résumé
Cellulose nanomaterials, such as cellulose nanocrystals (CNC), are expected to play a major role in the current environmental and societal transition towards a greater use of bioresources for materials applications. Due to their low density, high specific surface area and high Young's modulus, these nanomaterials have a great potential as sustainable, high-performance fillers for the development of materials with tunable rheological, thermo-mechanical, optical and barrier properties [1]. They are currently used mainly in paper manufacturing, packaging, membranes and bioengineering.
As with other nanoparticles, the dispersion of CNM in thermoplastic polymers remains a huge challenge for the development of high-performance polymer nanocomposites. In the literature, several processing methods have been studied to improve their dispersion and the mechanical properties of the nanocomposites, using solvent-based, melt processes and other more innovative processes such as chilled extrusion or wet compounding with various thermoplastic polymers as well as physico-chemical and processing aids [2], [3]. However, it has been shown that the different processes seem to have a similar impact on mechanical improvements, and therefore potentially on CNM dispersion, with the exception of the Kyoto process [3].
In this work, a common system to different preparation routes, based on thermoplastic polyvinyl alcohol (PVA) and CNC, is used to study the operating conditions and parameters. The different processing methods were compared on a laboratory scale: from conventional solvent and melt routes, to more recent hybrid routes. With the aim to identify the key steps in obtaining a good dispersion of CNC that best improves the mechanical properties of the final composite. The impact of the processing method on the CNC dispersion in PVA is discussed, in particular by means of rheological, mechanical and microstructural analyses of PVA/CNC composites.