All-cellulose nanocomposites, in which reinforcement nanofiber and matrix are both composed of cellulose, were fabricated using various processes and various resources such as kenaf bast fiber, canola fiber, filter paper and bacterial cellulose. The structure and mainly mechanical properties of these novel composites were reviewed. By grinding, plant microfiber (fiber diameter of ca. 30μm) could be down sized to nanofiber (fiber diameter of ca. 30 nm) without destroying the crystallites of cellulose I. By immersing these nanofibers into solvent, their surface was selectively dissolved. Then, by compression and drying, all-cellulose nanocomposite was obtained. The nanocomposites reveal superior mechanical properties (tensile strength up to 411 MPa) and optical transparency. Direct fabrication method starting from microfiber into nanocomposite was also proposed through nanowelding using ionic liquid as solvent. Cellulose nanopaper from cellulose nanofiber was also mentioned as a high tough material. These high mechanical performance of these novel nanomaterials are originated form three factors, that is, high mechanical performance of cellulose itself, strong hydrogen bonds between nanofibers, and high entangled state of nanofibers.
Many investigations have been paid to an application of cellulose nanofiber (CNF) because of its diverse fascinating characteristics such as outstanding mechanical, thermal properties, renewable resources, and others. In this article, three developments of nanocomposites between CNF and thermoplastics were described. First, the CNF and a polyamide 11 (PA11) derived from caster bean oil were compounded by making use of polymer processing techniques, and its static/dynamic mechanical properties were investigated. The static mechanical and thermal properties of the bio-nanocomposites were equal to an engineering plastic material as the result of a cationized surface treatment onto the CNF. Secondly, the foams of the hydrophobic modified CNF/HDPE nanocomposites were investigated. The modified CNF made the bubble radius decrease because of the increase in the storage modulus of the composites. By nanofiber reinforcement and microcellular foaming, the modified CNF/HDPE foams showed the higher mechanical properties and lower density than neat HDPE. Thirdly, the general dyeing techniques for cotton fiber and fabrics were applied to the CNF in order to gain an outstanding colorability and high mechanical properties for plastic materials. The obtained color tones of the CNF were good, and its nanocomposites material compounded with the colored CNF and a polyolefin created a novel ambience which previous pigment materials can not possibly make it. Coloring and reinforcement for plastic materials are attained at the same time by making use of the developed colored CNF.
In wood plastic composites which are produced wood flour and plastic, the dispersion of wood and the compatibility of wood/plastic are important factors. These factors are the same as cellulose nanofiber composites. In this review, it is introduced outline of wood plastic composites and cellulose nanofiber composites used wood plastic composites process.
This paper summarizes our research activities to produce nanoscopic fibrillated product from lignocellulosic biomass using mechano-chemical treatment. Hydrothermal and ozone pretreatment were effective to loosen the cell wall structure, resulting in the improvement of mechanical fibrillation. Characterization of thus-obtained products was conducted, showing sub-micron and/or nanoscopic fibrous morphology, high surface area and high enzymatic digestibility. The effect of chemical composition of the fibrillated product on the adsorption and degradation behavior of various cellulase was investigated by Quartz Crystal Microbalance(QCM). The relationship between the aspect ratio and intrinsic viscosity for the fibrillated product with high aspect ratio was also investigated. The fibrillated product was applied as the reinforcement for nanocomposites and various surfactants were attempted to improve the distribution of the fibrillated product in polymer matrix.
We succeeded in developing the highly porous Cellulose Nanofiber nonwoven fabrics sheet, CNF sheet, composed of cellulose nanofibers (average fiber diameter: ranging of 30- 400 nm). CNF sheet has multilayered structure constituted of network plane of nanofibers over at least 50 layer. Therefore, with increasing in weight of CNF sheet, the pore size becomes to decrease and have the narrower pore size distribution. CNF sheet is corresponding to a heat resistant material (usable up to 200 °C, showing no glass transition temperature, low coefficient of thermal expansion (CTE): below 10 ppm/K as the CTE value between room temperature and 200 °C), and has very small pore size (maximum pore size: ranging of 0.06-2 micro meters), furthermore, has very large surface area (specific surface area by B.E.T. method: 7-100 m2/g). These unique features of CNF sheet would lead to the applications in wide industrial field, such as functional filter, substrate material for a low CTE hybrid film and for a medical use.