Nanocellulose materials (NCs) have unique morphologies, functions, characteristics, and producibility from abundant, renewable, and atmospheric CO2-accumulated plant biomass resources. NCs have nanometer-sized widths originating from cellulose microfibrils photosynthesized and numerously present in plant living bodies, and are artificially prepared from plant cellulose fibers or pulp fibers by mechanical disintegration in water or soften polymers. NCs are categorized to two groups: chemically pretreated and then mechanically fibrillated NCs (C-NCs) and only mechanically fibrillated NCs (M-NCs). C-NCs are further classified to long cellulose nanofibrils or cellulose nanofibers (CNFs) with aspect ratios of >150 and long lengths of >300 nm and short cellulose nanocrystals (CNCs) with aspect ratios of <150 and lengths of <200 nm. In this paper, suitable applications for C-NCs based on their morphologies and functional groups abundantly present on their surfaces are introduced based on the ongoing researches and developments in Japanese academia and industry. NC-reinforced polymer nanocomposites are the most promising applications for CNFs because of their large surface areas and high aspect ratios. However, it is quite difficult to homogeneously distribute the highly hydrophilic CNFs in hydrophobic polymer matrices without forming large CNF agglomerates. Some in-site surface hydrophobizations of CNFs during drying of aqueous CNF dispersions and subsequent elastic kneading with polymers have been found to be efficient to prepare CNF/polymer composites with good mechanical and thermal properties.

Nanocelluloses, their fundamentals and applications