Cellulose fibrils with widths in the nanometer range are nature-based materials with unique and potentially useful features. Most importantly, these novel nanocelluloses open up the strongly expanding fields of sustainable materials and nanocomposites, as well as medical and life-science devices, to the natural polymer cellulose. The nanodimensions of the structural elements result in a high surface area and hence the powerful interaction of these celluloses with surrounding species, such as water, organic and polymeric compounds, nanoparticles, and living cells. This Review assembles the current knowledge on the isolation of microfibrillated cellulose from wood and its application in nanocomposites; the preparation of nanocrystalline cellulose and its use as a reinforcing agent; and the biofabrication of bacterial nanocellulose, as well as its evaluation as a biomaterial for medical implants.

Nanocelluloses: A New Family of Nature-Based Materials

Due to their abundance, high strength and stiffness, low weight and biodegradability, nano-scale cellulose fiber materials (e.g., microfibrillated cellulose and bacterial cellulose) serve as promising candidates for bio-nanocomposite production. Such new high-value materials are the subject of continuing research and are commercially interesting in terms of new products from the pulp and paper industry and the agricultural sector. Cellulose nanofibers can be extracted from various plant sources and, although the mechanical separation of plant fibers into smaller elementary constituents has typically required high energy input, chemical and/or enzymatic fiber pre-treatments have been developed to overcome this problem. A challenge associated with using nanocellulose in composites is the lack of compatibility with hydrophobic polymers and various chemical modification methods have been explored in order to address this hurdle. This review summarizes progress in nanocellulose preparation with a particular focus on microfibrillated cellulose and also discusses recent developments in bio-nanocomposite fabrication based on nanocellulose.

Microfibrillated cellulose and new nanocomposite materials: a review

This paper provides an overview of recent progress made in the area of cellulose nanofibre-based nanocomposites. An introduction into the methods used to isolate cellulose nanofibres (nanowhiskers, nanofibrils) is given, with details of their structure. Following this, the article is split into sections dealing with processing and characterisation of cellulose nanocomposites and new developments in the area, with particular emphasis on applications. The types of cellulose nanofibres covered are those extracted from plants by acid hydrolysis (nanowhiskers), mechanical treatment and those that occur naturally (tunicate nanowhiskers) or under culturing conditions (bacterial cellulose nanofibrils). Research highlighted in the article are the use of cellulose nanowhiskers for shape memory nanocomposites, analysis of the interfacial properties of cellulose nanowhisker and nanofibril-based composites using Raman spectroscopy, switchable interfaces that mimic sea cucumbers, polymerisation from the surface of cellulose nanowhiskers by atom transfer radical polymerisation and ring opening polymerisation, and methods to analyse the dispersion of nanowhiskers. The applications and new advances covered in this review are the use of cellulose nanofibres to reinforce adhesives, to make optically transparent paper for electronic displays, to create DNA-hybrid materials, to generate hierarchical composites and for use in foams, aerogels and starch nanocomposites and the use of all-cellulose nanocomposites for enhanced coupling between matrix and fibre. A comprehensive coverage of the literature is given and some suggestions on where the field is likely to advance in the future are discussed.

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Review: current international research into cellulose nanofibres and nanocomposites

Renewable resources are used increasingly in the production of polymers. In particular, monomers such as carbon dioxide, terpenes, vegetable oils and carbohydrates can be used as feedstocks for the manufacture of a variety of sustainable materials and products, including elastomers, plastics, hydrogels, flexible electronics, resins, engineering polymers and composites. Efficient catalysis is required to produce monomers, to facilitate selective polymerizations and to enable recycling or upcycling of waste materials. There are opportunities to use such sustainable polymers in both high-value areas and in basic applications such as packaging. Life-cycle assessment can be used to quantify the environmental benefits of sustainable polymers.

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Sustainable polymers from renewable resources

Microfibrillated cellulose - its barrier properties and applications in cellulosic materials: a review.

Surface modification of natural fibers using bacteria:depositing bacterial cellulose onto natural fibers to create hierarchical fiber reinforced nanocomposites

underexploited. This paper describes a new approach to producing hierarchical composite structures from completely renewable resources. Bacterial cellulose was introduced as a nanoscalereinforcementbyattachingittothesurfaceofnatural fibers, in this case sisal. The natural fibers have micrometerscale diameters, and although they themselves have a hierarchical internal structure, the deliberate introduction of the nanofiller provides a new means of controlling their interaction with and the behavior of the matrix. The modified sisal fibers were incorporated into a bioderived polymer matrix, poly(L-lactic acid) (PLLA), to obtain a new class of hierarchical composite that is both derived from renewable resources and biodegradable. The attachment approach facilitates modification of the fiber surface and avoids the problems commonly associated with agglomeration and dispersion of nanofillers; the result is a rise in interfacial adhesion to the polymer matrix, and an associated improvement in the performance of the composite. The effects of modifying sisal fibers, both in their natural state (Sisal-N) and after extraction withacetone(Sisal-A),wereassessedqualitativelybySEM,and quantitatively by single-fiber tensile and pull-out (interfacial shear strength) tests. The hierarchical-composite performance was determined using compression-molded samples loaded in tension, parallel (08) and perpendicular (908) to the primary reinforcing fibers; the response to water immersion was also explored.

Creating Hierarchical Structures in Renewable Composites by Attaching Bacterial Cellulose onto Sisal Fibers

One of the main problems in fabricating natural fibre reinforced polymers is the poor adhesion between intrinsically polar plant fibres and non-polar polymer matrices. We have developed a truly green technique of modifying natural fibre (hemp and sisal) surfaces to improve the interaction between the fibres and polymers by attaching nano-scale bacterial cellulose to the fibre surfaces. These modified natural fibres were then incorporated into the renewable polymers cellulose acetate butyrate (CAB) and poly-L-lactic acid (PLLA). Unidirectional natural fibre reinforced composites were manufactured to investigate the impact of the surface modification on the fibre and interface dominated composite properties. Both the tensile strength parallel as well as perpendicular to the fibres of the composites reinforced by bacterial cellulose modified natural fibres were found to increase significantly, especially in the case of a PLLA matrix. In case of modified sisal reinforced PLLA the parallel strength increases b...

Nanocellulose enhanced interfaces in truly green unidirectional fibre reinforced composites

Effect of Atmospheric Air Pressure Plasma Treatment on the Thermal Behaviour of Natural Fibres and Dynamical Mechanical Properties of Randomly-Oriented Short Fibre Composites

The invention relates to a material comprising cellulose in association with a support selected from a polymer and/or a fibre, wherein said cellulose is produced by a micro- organism. The cellulose-reinforced material is provided for incorporation into a composite.

Julasak Juntaro

Papers

Surface modification of natural fibers using bacteria:depositing bacterial cellulose onto natural fibers to create hierarchical fiber reinforced nanocomposites

Creating Hierarchical Structures in Renewable Composites by Attaching Bacterial Cellulose onto Sisal Fibers

Nanocellulose enhanced interfaces in truly green unidirectional fibre reinforced composites

Effect of Atmospheric Air Pressure Plasma Treatment on the Thermal Behaviour of Natural Fibres and Dynamical Mechanical Properties of Randomly-Oriented Short Fibre Composites

Material comprising microbially synthesized cellulose associated with a support like a polymer and/or fibre