Cellulose is a linear biopolymer found naturally in plant cells such as wood and cotton. It is the worlds most abundant polymer in nature and possesses properties such as good biocompatibility, low cost, low density, high strength, and good mechanical properties. By mechanical or chemical treatment, the cellulose fibers can be converted into cellulose nanofibers CNFs or cellulose nanocrystals CNCs that possess outstanding properties compared with the original cellulosic fiber but also when compared with other materials normally used as reinforcements in composite materials such as Kevlar or steel wires. This review will describe the nanocellulose materials preparation techniques and cellulose sources, chemical modification both on the crystalline surface and during hydrolysis and its many properties and its use in biocomposite materials. Nanocellulose in its different forms shows an increasing interest in application areas such as packaging, paper and paperboard, food industry, medical and hygiene products, paints, cosmetics, and optical sensors

Current interest in replacing fossil-fuel-derived polymers and materials in favor of renewable materials is high. An inherent difficulty with the use of biomass-derived polysaccharides and hemicelluloses in this context, however, is their stiffness and lack of flowability at temperatures relevant for thermal processing, which severely limits their capacity for thermal processing. Here, we present a modification that enables a heat-processable arabinoxylan (AX). The modification involves a ring-opening oxidation to a dialdehyde with subsequent reduction of the aldehydes to alcohol, to increase the number of OH groups, followed by an etherification with hydrophobic alkyl chains. The modified AX was successfully compression molded with heat into filmswhich become thermoplastic in behavior and highly flexibleand flows at temperatures above 130 °C. The films are stretchable up to 200%, and their strength and strain deformation are controlled by the degree of oxidation and substitution of the AX polymer. These findings are highly encouraging and open up the potential use of modified AX alone or as a composite in applications that include films, food packaging, and barriers via hot-melt processing techniques.

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Cellulose nanocrystals (CNCs) prepared via sulfuric acid hydrolysis are decorated with sulfate groups that yield a stable water suspension. To make the CNCs adaptable for use in composites, the hydroxyl groups on the surface are usually hydrophobized. In this article, an alternative hydrophobization method is described in which the sulfate groups are conjugated with azetidinium salts. The results of this study show that the sulfate groups can be functionalized with azetidinium salts and from thermal studies, it was discovered that the functionalization led to a 100 8C increase in thermal stability, compared with unmodified CNCs. The nanocomposites prepared by extrusion of CNC-coated low-density polyethylene powder displayed similar mechanical properties as the CNC-reference sample, but without the discoloration, due to the increased thermal stability. In conclusion, the azetidinium reagent reacts preferentially with sulfate groups, and this new type of chemical conversion of sulfate groups on polysaccharides will be beneficial in nanocomposite manufacturing.

Native hemicellulose lacks many of the properties that make fossil fuel-based polymers excellent for use in today's industrial products and processes. The mechanical and thermal properties of the hemicellulose can, however, be modified, and its processability increased. We functionalized galactoglucomannan to lower its glass transition temperature (T g ) and thereby increase its processability. The functionalization was achieved through an etherification reaction with butyl glycidyl ether used at three molar ratios. Films were produced, and their mechanical and thermal properties were evaluated. Thermogravimetric analysis showed that increased substitution increased the degradation temperature and decreased the water content in the sample, implying increased hydrophobicity upon modification. Dynamic mechanical analysis indicated that butyl glycidyl ether functionalization alters the thermal properties of the modified films both in the absolute values of T g and in the strength of the films. The etherification reaction resulted in a more ductile material than the unmodified galactoglucomannan (GGM).