The structure hierarchy of lignocellulosic fibers allows the extraction of particles of nanometric size. These nanoparticles, called “nanocellulose” or “cellulose nanomaterials”, essentially include cellulose nanofibrils (CNF – Cellulose NanoFibrils)obtained by mechanical means, and cellulose nanocrystals (CNC – Cellulose NanoCrystals) obtained chemically. Cellulose is the structural element of higher plants. It is therefore logical that the main intended application for cellulosic nanoparticles consists in exploiting this property in the form of reinforcing elements of polymeric nanocomposites. Many techniques, either experimental or theoretical, have been used to determine the Young’s modulus of nanocellulose materials. . A wide range of values has been reported. However, the average modulus value is around 100 GPa for CNF and 130 GPa for CNC . These values are consistent and fully compatible with the development of high performance nanocomposite materials. The specific modulus, i.e. the modulus normalized with respect to the density of the material, is often used: taking into account the density of the crystalline cellulose (1.5-1.6 g.cm−3), we find specific modulus values of the order of 65 Jg−1 and 85 Jg−1 for CNF and CNC respectively, values significantly higher than those of steel and of the same order of magnitude as those of Kevlar .
The use of nanocellulose as a “nano-additive” in a polymer formulation makes it possible to improve not only the mechanical properties of the material, but also the properties of barrier or resistance to swelling. The introduction of cellulosic nanomaterials into nanocomposite materials has been identified as one of the four greatest discoveries since the year 2000 in the report « Nanotechnology Research Directions for Societal Needs in 2020 » and the widespread use in nanotechnology of renewable and abundant raw materials as the Holy Grail to be achieved and the hurdle to be overcome.
This article begins with the presentation of the different methods for preparing nanocomposite materials with a polymer matrix and nanocellulose reinforcement. The mechanical properties of the resulting materials are then discussed. Then are developed the influence of parameters such as the morphology of the nanoparticles, the implementation process, as well as the microstructure of the matrix and the matrix-reinforcement interactions. Finally, the swelling and barrier properties of these materials are briefly discussed.
