Recent Advances in Hybrid CNC Reinforced Polymeric Nanocomposites.

M.J. Dunlop, B. Acharya, R. Bissessur
University of Prince Edward Island,
Canada

Keywords: cellulose nanocrystals, hybrids, tunicates, aspect ratio, polymeric nanocomposite

Summary:

As global attention is drawn to the benefits of renewable and sustainable resources, researchers have increasingly focused on incorporating these materials as either additives or replacements for nonrenewable resource in various areas. One of these areas is the use of sustainable cellulose nanocrystals (CNCs) to reinforce polymers. It is well known that these polymeric nanocomposites show improved mechanical properties when a percolating network of CNCs are incorporated within the polymer as a reinforcement. Furthermore, the magnitude of the CNC reinforcement is related to the aspect ratio of the rod like CNCs. Generally, plants are the most common CNC source material and produce CNCs with a low average aspect ratio (~20). By contrast, CNCs can also be obtained from marine animals known as tunicates. However, tunicate CNCs possess a considerably higher average aspect ratio (~100) than plant sourced CNCs. When incorporated as reinforcement the common, commercially available, lower aspect ratio CNCs percolate at a higher volume fraction than CNCs with higher aspect ratios. High aspect ratio tunicate CNCs require lower loading levels for percolation and mechanical reinforcement, but are not commercially available at this point. For this reason, many polymer based nanocomposite materials currently use high loading levels of plant derived CNC as reinforcement, rather than low loading levels of high aspect ratio tunicate derived CNCs. Herein, our recent advances in developing a scalable pilot plant process for isolating high aspect ratio CNCs from tunicates is briefly discussed. However we will primarily focus on the implications of a commercially available high aspect ratio tunicate derived CNC, in the context of our recent advances towards hybrid polymeric nanocomposites. Of particular interest is our findings which indicate that the use of high and low aspect ratio CNCs together to form hybrid polymeric nanocomposites results in mechanical reinforcement which exceeds either of the individual CNC sources at the same volume fraction. Practically, our findings imply that polymeric nanocomposites containing a high loading level of low aspect ratio CNC reinforcement could be replaced by a lower loading level of hybrid CNC reinforcement which contains both high and low aspect ratio CNCs.