ABSTRACT
Recently, scientists gained high interest in using cellulose nanowhiskers (CNWs) or cellulose nanocrystals (CNCs) as mechanical reinforcement in nanocomposites with a (bio) polymer matrix. This interest is primarily abstracted from the plentiful availability of cellulose and shortage of fossil oil-based polymer resources that elucidate the need of renewable resources. Therefore, CNWs are increasingly used as alternative additives to decrease dependency on petroleum-based products (Goetz et al. 2009). Agricultural residues, water plants, grasses, or marine organisms are sources from which cellulose can be obtained for the production of nanofibers. Different definitions for nanocellulose are often referred to (1) CNWs or CNCs are short crystalline rodlike nanoparticles, while (2) microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), or cellulose nanofiber (CNF) are long flexible fibers having crystalline and amorphous zones with micro- to nanometer fiber diameters forming a dense fiber network. The beneficial use of CNW additives in combination with biopolymers has evolved from their multifunctional properties and ability to control the self-assembly of CNW into well-defined architectures. Moreover, the high crystallinity of CNW and induced variations in crystallization kinetics within a polymer nanocomposite may influence the morphological and thermomechanical properties. However, main challenges in adding CNW to polymer matrices include a good control on the development of a percolation network and good interface compatibility. A drawback of CNW is poor dispersibility within hydrophobic or nonpolar polymer composites due to the high density of hydroxyl groups on its surfaces, which leads to aggregation and agglomeration. While the compatibility of hydrophilic CNW within hydrophobic polymer matrices is initially controlled through chemical surface modification, the suitable processing of polymer blends with CNW additives requires good understanding of the physical compounding and mixing properties.
