As the most important skeletal component in plants, the polysaccharide cellulose is an almost inexhaustible polymeric raw material with fascinating structure and properties. Formed by the repeated connection of D-glucose building blocks, the highly functionalized, linear stiff-chain homopolymer is characterized by its hydrophilicity, chirality, biodegradability, broad chemical modifying capacity, and its formation of versatile semicrystalline fiber morphologies. In view of the considerable increase in interdisciplinary cellulose research and product development over the past decade worldwide, this paper assembles the current knowledge in the structure and chemistry of cellulose, and in the development of innovative cellulose esters and ethers for coatings, films, membranes, building materials, drilling techniques, pharmaceuticals, and foodstuffs. New frontiers, including environmentally friendly cellulose fiber technologies, bacterial cellulose biomaterials, and in-vitro syntheses of cellulose are highlighted together with future aims, strategies, and perspectives of cellulose research and its applications.

Cellulose: Fascinating Biopolymer and Sustainable Raw Material

This critical review provides a processing-structure-property perspective on recent advances in cellulose nanoparticles and composites produced from them. It summarizes cellulose nanoparticles in terms of particle morphology, crystal structure, and properties. Also described are the self-assembly and rheological properties of cellulose nanoparticle suspensions. The methodology of composite processing and resulting properties are fully covered, with an emphasis on neat and high fraction cellulose composites. Additionally, advances in predictive modeling from molecular dynamic simulations of crystalline cellulose to the continuum modeling of composites made with such particles are reviewed (392 references).

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Cellulose nanomaterials review: structure, properties and nanocomposites

Recently, there has been a rapid growth in research and innovation in the natural fibre composite (NFC) area. Interest is warranted due to the advantages of these materials compared to others, such as synthetic fibre composites, including low environmental impact and low cost and support their potential across a wide range of applications. Much effort has gone into increasing their mechanical performance to extend the capabilities and applications of this group of materials. This review aims to provide an overview of the factors that affect the mechanical performance of NFCs and details achievements made with them.

A review of recent developments in natural fibre composites and their mechanical performance

https://pubs.rsc.org/en/Content/ArticlePDF/2013/GC/C2GC36364J

Deconstruction of lignocellulosic biomass with ionic liquids

Sustainability, industrial ecology, eco-efficiency, and green chemistry are directing the development of the next generation of materials, products, and processes. Biodegradable plastics and biocompatible composites generated from renewable biomass feedstock are regarded as promising materials that could replace synthetic polymers and reduce global dependence on fossil fuel sources.1 It is estimated that the world is currently consuming petroleum at a rate 100 000 times faster than nature can replace it.2 The growing global environmental awareness and societal concern, high rate of depletion of petroleum resources, concepts of sustainability, and new environmental regulations have triggered the search for new products and processes that are more compatible with the environment. The most abundant natural polymer in our environment is cellulose. It has an estimated annual biosphere production of 90 × 109 metric tons and, consequently, represents the most obvious renewable resource for producing biocomposites.3 Its highly ordered structure is responsible for its desirable mechanical properties but makes it a challenge to find suitable solvents for its dissolution.4 The first attempts to dissolve cellulose date back to the early 1920s.5 Several aqueous and nonaqueous cellulose solvents have been discovered since then, but all of these solvents suffer either from high environmental toxicity or from insufficient solvation power.6 In general, the traditional cellulose dissolution processes require relatively harsh conditions and the use of expensive and uncommon solvents, which usually cannot be recovered after the process.6-10 However, a new class of solvents was opened to the cellulose research community, when in 2002 Swatloski et al. reported the use of an ionic liquid as solvent for cellulose both for the regeneration of cellulose and for the chemical modification of the polysaccharide.7 In 1934, Graenacher had discovered a solvent system with the ability to dissolve cellulose, but this was thought to be of little practical value at the time.11,12 Ionic liquids are a group of salts that exist as liquids at relatively low temperatures (<100 °C). They have many attractive properties, including chemical and thermal stability, nonflammability, and immeasurably low vapor pressure.12 First discovered in 1914 by Walden, their huge potential in industry and research was only realized within the last few decades.13,14 This review aims to provide a summary of our current state of knowledge on the structural features of wood * To whom correspondence should be addressed. E-mail: ken.marsh@ canterbury.ac.nz. Tel.: +64 3364 2140. Fax: +64 3364 2063. † Department of Chemical and Process Engineering. ‡ Department of Mechanical Engineering. Andre Pinkert was born in Schwabach, Germany, in 1981. He studied Chemistry at the University of Erlangen-Nurnberg, Germany, and received his prediploma and diploma degrees in 2004 and 2008, respectively. During 2005, he joined the Marine Natural Products Group, lead by Murray H. Munro and John W. Blunt, at the University of Canterbury (UoC), New Zealand, working on the isolation and characterization of bioactive metabolites. In early 2006, he returned to Germany and resumed his studies at the University of Erlangen-Nurnberg, finishing his degree under the supervision of Rudi van Eldik. Associated with his studies, during 2007, he worked for AREVA NP on radio-nuclear chemistry and computer modeling. Since 2008, he is studying towards a Ph.D. degree at UoC under the supervision of Shusheng Pang, Ken Marsh, and Mark Staiger. His research focuses on biocomposites from natural fibers, processed via ionic liquids. Chem. Rev. 2009, 109, 6712–6728 6712

Ionic Liquids and Their Interaction with Cellulose

Structure formation of regenerated cellulose materials from NMMO-solutions

Spun cellulose fibres from the viscose, lyocell and carbamate processes have been used to reinforce thermoplastic commodity polymers, such as polypropylene (PP), polyethylene (PE) and (high impact) polystyrene (HIPS) as well as poly(lactic acid) (PLA) and a thermoplastic elastomer (TPE) for injection moulding applications. A specially developed double pultrusion technique has been employed for compounding. Fibres were analysed in single fibre tensile tests. Strength, stiffness, impact strength, and heat distortion temperature (HDT) were determined for injection-moulded standard test specimen and structural features were revealed by scanning electron microscopy. A strong reinforcing effect was observed in all cases. In particular, high tenacity tyre cord rayon gives excellent composite strength and impact strength, often doubling or tripling the pristine matrix values. In the case of PP, Lyocell type fibres provide enhanced stiffness and HDT, and thus the combination of both fibre types leads to a balanced composite property profile. The PE case is very similar to PP. For HIPS mainly strength and stiffness is increased, while for TPE the property profile is changed completely. With PLA, a biogenic and biodegradable composite with excellent mechanical properties is presented.

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Novel cellulose fibre reinforced thermoplastic materials

High-tenacity man-made cellulose filament yarn (rayon tyre cord yarn) has been used to reinforce polypropylene (PP), polyethylene, high impact polystyrene (HIPS), and poly (lactic acid) (PLA) for injection moulding applications. Highly homogeneous composites are obtained with the pultrusion compounding method developed. For PP the influence of coupling agent, fibre weight fraction, fibre cut length and PP type on basic mechanical properties of the composites have been studied. For a fibre load of 30 wt%, typical values for tensile strength, modulus, Charpy unnotched and notched impact strength are 80 MPa, 3.5 GPa, 85 kJ/m2, and 12 kJ/m2, respectively. A high impact resistance level is maintained also at low temperatures where the matrix material becomes brittle. For the other matrix materials, similar reinforcing effects are observed, except for the impact behaviour of HIPS, where the reinforcing fibres interfere with the impact modification of the matrix polymer. In contrast, the impact characteristics of PLA are drastically improved increasing the unnotched and notched Charpy strengths by 380% and 200%, respectively. With the property level obtained, cellulose man-made fibre reinforced composites prove to be an alternative to short glass fibre reinforced plastics.

High-tenacity man-made cellulose fibre reinforced thermoplastics – Injection moulding compounds with polypropylene and alternative matrices

A number of hybrid composites was made with jute, mercerised jute, and high tenacity man-made cellulose tyre cord yarn Cordenka of dissimilar ratios by a pultrusion process and subsequent injection moulding. Composites of jute, mercerised jute, and Cordenka were also made in order to compare the properties. The matrix material was a polypropylene/ethylene block copolymer (PP), and a maleic acid anhydride grafted PP (MAPP) was used as a coupling agent. The overall fiber contain was 25%. Mechanical properties such as tensile and bending strength, tensile and bending modulus, Charpy impact strength, and heat distortion temperature (HDT) were determined. High strength (>70 MPa) and excellent impact properties (>80 kJ/m 2 ) were achieved with pure Cordenka reinforcement. Partial substitution of jute instead of Cordenka leads to enhance stiffness properties of the composite as well as increased heat distortion temperature (HDT) values above 105 °C for all the tested compositions (25%, 50%, 75%, and 100% jute) and for an overall fiber load of 25%. On the other hand, impact strength decreases with increasing jute fraction down to 22 kJ/m 2 for pure jute. A good property balance is achieved for a composite with 25 wt.% jute and 75 wt.% Cordenka, maintaining impact strength of 79 kJ/m 2 . Mercerisation of the jute fibers gave moderate improvements in the composite properties. Very good fiber (both jute and Cordenka) matrix adhesion was observed by SEM.

Hybrid composites of jute and man-made cellulose fibers with polypropylene by injection moulding

Samples of ball milled cellulose were prepared by ball milling pulps from eucalyptus and softwood (spruce/pine). Water sorption isotherms were obtained by both dynamic vapor sorption and equilibration over saturated salt solutions, in the water content range of 5–42% db (db = dry basis; water as a % age of total solids). Dynamic mechanical analysis using a pocket technique showed a water content dependent thermal transition occurring at the same temperature for the two pulp samples, which was interpreted as a glass transition. Fitting the data to a Couchman–Karasz relationship predicted a value for T
 g of the dry cellulose of approximately 478 K, which was similar to values previously reported for other dry polysaccharides. No clear glass transition could be observed calorimetrically, although an endotherm at approximately 333 K was measured, which in polymers is normally attributed to enthalpic relaxation, however the lack of dependence of this endotherm on water content suggests that the melting of some weak associations, such as residual hydrogen bonds, could be a more credible explanation. An exotherm was also observed on heating, which was dependent on water content and which was attributed to partial crystallization of the cellulose. This was confirmed by Wide angle X-ray diffraction and cross polarization magic angle spinning 13C NMR (CPMAS NMR). The recrystallisation was predominantly to form I of cellulose. This was thought to be caused by a small amount of residual form I (probably less than 5%) acting as a template for the crystallizing material. Differential scanning calorimetry reheat curves showed the appearance of freezable water for water contents higher than 20%, as a result of a transfer of water to the amorphous phase following crystallization. The increase in cellulose rigidity following crystallization was also confirmed by CPMAS NMR relaxation. Low resolution proton NMR T
 2 relaxation suggested the presence of proton water/cellulose exchange, which was active at water contents of 20% and above.

Johannes Ganster

Papers

Structure formation of regenerated cellulose materials from NMMO-solutions

Novel cellulose fibre reinforced thermoplastic materials

High-tenacity man-made cellulose fibre reinforced thermoplastics – Injection moulding compounds with polypropylene and alternative matrices

Hybrid composites of jute and man-made cellulose fibers with polypropylene by injection moulding

The glass transition and crystallization of ball milled cellulose