Cellulose Nanomaterials as Green Nanoreinforcements for Polymer Nanocomposites
Professor Alain Dufresne, INP Pagora, Grenoble Institute of Technology, France
Unexpected and attractive properties can be observed when decreasing the size of a material down to the nanoscale. Cellulose is no exception to the rule. In addition, the highly reactive surface of cellulose resulting from the high density of hydroxyl groups is exacerbated at this scale. Different forms of cellulose nanomaterials, resulting from a top-down deconstructing strategy (cellulose nanocrystals, cellulose nanofibrils) or bottom-up strategy (bacterial cellulose) are potentially useful for a large number of industrial applications. These include the paper and cardboard industry, use as reinforcing filler in polymer nanocomposites, basis for low-density foams, additive in adhesives and paints, as well as a wide variety of filtration, electronic, food, hygiene, cosmetic, and medical products. However, it is as a biobased reinforcing nanofiller that they have attracted significant interest during the last 20 years. Impressive mechanical properties can be obtained for these materials. They obviously depend on the type of nanomaterial used, but the crucial point is the processing technique. As for any nanoparticle, the main issue is related to their homogeneous dispersion within the polymeric matrix. An important challenge consists in the preparation of polymer nanocomposites using industrial melt processing techniques, avoiding the liquid medium methods.
Optimizing Cellulose Nanocrystal Surface Chemistry to Enhance Colloidal and Thermal Stability
Professor Emily Cranston, Department of Chemical Engineering, McMaster University, Canada
Cellulose nanocrystals (CNCs) are rod shaped nanoparticles extracted from natural cellulose sources through a hydrolysis procedure which most commonly uses sulfuric acid. Recently, other acids have been used in the hydrolysis procedure to modify CNC properties. CNCs hydrolysed with phosphoric acid have been shown to have increased thermal stability; however, this new procedure has not been optimized. Phosphoric acid-hydrolyzed CNCs (P-CNCs) have low surface charge, causing them to aggregate in suspension and even more so after heat treatment. A design of experiments approach was completed to study the effects of hydrolysis parameters on P-CNC size, aspect ratio, crystallinity, thermal stability and colloidal stability. Additionally, hydrolyses were performed with both sulfuric and phosphoric acid to yield CNCs with a combination of charged surface groups. It was found that the hydrolysis conditions have significant effects on several CNC properties, most notably on colloidal stability and aspect ratio. This study proposes facile methods (and small tweaks to industrial production protocols) for controlling key properties which are crucial for high temperature/pressure applications of CNCs, such as oil and gas drilling and completion fluids.
Anticipated Paper Title: Design of Experiments Optimization of Cellulose Nanocrystals Produced through Phosphoric Acid Hydrolysis for Enhanced Colloidal and Thermal Stability
Watching Paper Dry: Making Photonic Structures form Cellulose Nanocrystals
Professor Mark MacLachlan, Department of Chemistry, University of British Columbia, Canada
Cellulose nanocrystals (CNCs) obtained from paper or cotton are of great interest for many applications. In water, CNCs spontaneously form a chiral nematic lyotropic liquid crystalline phase, which can be preserved in dried films. The helicoidal structural organization of the CNCs in these films resembles the Bouligand structure of chitin found in crabs and other arthropods, and leads the films to be iridescent.
In 2010, Shopsowitz, Qi, Hamad, and MacLachlan reported that this liquid crystalline phase of CNCs can be used to template mesoporous silica with chiral nematic order, and they have since been able to transfer the supramolecular organization of CNCs to diverse other materials, including titania, polymers, and hydrogels. In this talk, Prof. MacLachlan will discuss his team’s recent progress to use CNCs as a template for the construction of new materials. He will discuss the use of hydrogels as a means to study the liquid crystallinity and to form spheres with chiral nematic order.
Better together: Synergy in Nanocellulose Blends
Professor Alexander Bismarck, University of Vienna and Department of Chemical Engineering, Imperial College London, UK
Cellulose nanopapers have gained significant attention in the recent years as large-scale reinforcement for high-loading cellulose composites, substrates for printed electronics and filter nanopapers for water treatment applications. The mechanical properties of nanopapers are of fundamental importance for all these applications. Cellulose nanopapers can simply be prepared by filtration of nanocellulose. It was already demonstrated that the mechanical properties of cellulose nanopapers can be tailored by the fineness of the fibrils used or by modifying nanocellulose fibrils for instance by polymer adsorption but nanocellulose blends remain underexplored. We show that the mechanical and physical properties of nanopapers can be tuned by creating hierarchical structures in nanopapers by blending various grades of nanocellulose, i.e. bacterial cellulose, cellulose nanofibrils extracted from bagasse by mechanical and chemical pre-treatments. We found that nanopapers made from blends of two or even more nanocellulose grades show synergistic effects resulting in improved stiffness, strength, ductility and toughness and physical properties.