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Introduction to cellulose nanocomposites
Abstract
This chapter will introduce the reader to the topic of nanocomposites based on cellulose and also give a short description of the content of this book. This is a relatively new research field and there is no other book available on this topic. There is a growing interest on cellulose nanocomposites in developed and developing world and, especially if the nanocomposites are based totally on renewable raw materials. The purpose of this book is to provide information about how to produce nano whiskers or fibrils from different cellulosic sources and the techniques to characterize the nano structures of cellulosic materials and their composite properties. This book will give knowledge of different processing methods for nanocomposites, provide updated information on composites properties and also deal with interesting applications especially in medical field. (c) 2006 American Chemical Society.
... Some authors even have proposed that nanotechnology will change our lives in profound ways, allowing engineers to come up with stronger, more efficient, or more technologically advanced ways of meeting human needs. Judging from recent publications, the excitement also has caught the attention of forest products technologists (Wegner 1996; Moore 2004; Ramsden 2005; Hamad 2006; Oksman and Sain 2006; Hubbe 2006b; Wegner and Jones 2006; Klemm et al. 2006; Beecher 2007; Lucia and Rojas 2007). The American Forest and Paper Association (2005) held a high-level workshop on nanotechnology in an effort to consider ways in which the forest products industry could become more involved and potentially reap benefits in this field. ...
... The word " fibril " has been used by various researchers to describe relatively long and very thin pieces of cellulosic material (Favier et al. 1995a,b; Dufresne et al. 2000; American Forest and Paper Assoc. 2005; Oksman and Sain 2006; Marcovich et al. 2006; Dalmas et al. 2006; Wu et al. 2007; Abe et al. 2007; Cheng et al. 2007). But papermakers also use the term " fibril " to denote thin cellulosic strands that remain attached on the outer surface of fibers, especially in the case of refined chemical pulp fibers (Clark 1978). ...
... Indeed, because of these properties, the venue of nanofibers has attracted a lot of research efforts in a number of disciplines and continues to be a subject of intense study for its utility in materials, sensor applications, and biomedical science. Very long and straight crystals of cellulose (cellulose nanocrystals) sometimes have been called " whiskers " (Favier et al. 1995a,b, Hajji et al. 1996 Dufresne 2000; Ruiz et al. 2000; Samir et al. 2004b Samir et al. , 2005 Schroers et al. 2004; Kvien et al. 2005; Ljungberg et al. 2005; Hamad 2006; Renneckar et al. 2006; Oksman and Sain 2006; Wang et al. 2006a; Abe et al. 2007; Marcovich et al. 2006; Petersson et al. 2007; Pu et al. 2007; van den Berg et al. 2007a,b; Ye 2007; Elazzouzi-Hafraoui et al. 2008). Indeed, electron micrographs of nanofibers obtained from tunicates show objects that resemble a cat's whiskers in terms of straightness and the length-to-width ratio. ...
Because of their wide abundance, their renewable and environmentally benign nature, and their outstanding mechanical properties, a great deal of attention has been paid recently to cellulosic nanofibrillar structures as components in nanocomposites. A first major challenge has been to find efficient ways to liberate cellulosic fibrils from different source materials, including wood, agricultural residues, or bacterial cellulose. A second major challenge has involved the lack of compatibility of cellulosic surfaces with a variety of plastic materials. The water-swellable nature of cellulose, especially in its non-crystalline regions, also can be a concern in various composite materials. This review of recent work shows that considerable progress has been achieved in addressing these issues and that there is potential to use cellulosic nano-components in a wide range of high-tech applications.
... Therefore the studies of kenaf fibers and separation to nanofibers are of interest. Nano-sized reinforcements from renewable resources have gained an increased interest during the past years (Oksman and Sain 2006; Hubbe et al 2008). The expected advantages of nanofibers as compared to micro-sized fibers include an enhancement of the mechanical properties with a decrease in fiber size due to large surface areas (Oksman and Sain 2006). ...
... Nano-sized reinforcements from renewable resources have gained an increased interest during the past years (Oksman and Sain 2006; Hubbe et al 2008). The expected advantages of nanofibers as compared to micro-sized fibers include an enhancement of the mechanical properties with a decrease in fiber size due to large surface areas (Oksman and Sain 2006). Cellulosic nanofillers from wood, wheat straw, soybean, hemp, etc., have already been employed as reinforcements in a variety of polymers to produce nanocomposites with improved mechanical properties (Chacraborty et al 2007; Wang and Sain 2007;; Seydibeyoğlu and Oksman 2008; Alemdar and Sain 2008). ...
Kenaf (Hibiscus cannabinus) nanofibers were isolated from unbleached and bleached pulp by a combination of chemical and mechanical treatments. The chemical methods were based on NaOH-AQ (anthraquinone) and three-stage bleaching (DEpD) processes, whereas the mechanical techniques involved refining, cryo-crushing, and high-pressure homogenization. The size and morphology of the obtained fibers were characterized by environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM), and the studies showed that the isolated nanofibers from unbleached and bleached pulp had diameters between 10-90 nm, while their length was in the micrometer range. Fourier transform infrared (FTIR) spectroscopy demonstrated that the content of lignin and hemicellulose decreased in the pulping process and that lignin was almost completely removed during bleaching. Moreover, thermogravimetric analysis (TGA) indicated that both pulp types as well as the nanofibers displayed a superior thermal stability as compared to the raw kenaf. Finally, X-ray analyses showed that the chemo-mechanical treatments altered the crystallinity of the pulp and the nanofibers: the bleached pulp had a higher crystallinity than its unbleached counterpart, and the bleached nanofibers presented the highest crystallinity of all the investigated materials.
... This could be attributed to dissimilarity in their geometry. The NC is a rigid platelet-like nanoparticle [7], whereas the CNF is a long flexible nanoparticle [22,25]. The possibility of entanglement of CNF was then greater when compared with NC. ...
Natural rubber (NR) nanocomposites reinforced with five parts per hundred rubber (phr) of two different nano-fillers, i.e., nanoclay (abbrev. NC) and cellulose nanofiber (abbrev. CNF), were prepared by using latex mixing approach, followed by mill-compounding and molding. The morphology, stress–strain behavior, strain-induced crystallization, and bound rubber of the NR nanocomposites were systematically compared through TEM, tensile test, WAXS, DMA, and bound rubber measurement. The aggregated CNFs were observed in the NR matrix, while the dispersed nanosized clay tactoids were detected across the NR phase. The reinforcement effects of NC and CNF were clearly distinct in the NR nanocomposites. At the same nano-filler content, the addition of NC and CNF effectively accelerated strain-induced crystallization of NR. The high tensile strength obtained in the NC-filled NR nanocomposite was attributed to strain-induced crystallization of NR accelerated by well-dispersed NC. However, the larger tensile modulus and low strain for the CNF-filled NR were related to the formation of immobilized NR at the interface between CNF aggregate and NR. The immobilization effect of NR at the CNF surface offered by a mutual entanglement of CNF aggregate and NR chain led to local stress concentration and accelerated strain-induced crystallization of CNF/NR nanocomposite. From the present study, the NR nanocomposites combined with 5 phr CNF shows high-tensile modulus and acceptable breaking tensile stress and strain, suggesting the application of CNF/NR based nanocomposite in automotive and stretchable sensors for next-generation electronic devices.
... The FTIR spectra of different treatments are shown in Figs. 5 and 6. All samples exhibited a wide band in the range of 3200 to 3500 cm -1 , which is due to stretching vibration of O-H from OH groups of cellulose molecules (Khalil et al. 2001;Xu et al. 2005;Sain et al. 2006;Viera et al. 2007;Mandal and Chakrabarty 2011;Li et al. 2012;Lu and Hsieh 2012;Hokkanen et al. 2013;Rosli et al. 2013;Maiti et al. 2013;Kumar et al. 2014;Maryana et al. 2014;Li et al. 2014;Saelee et al. 2016;Almasian et al. 2016;Wulandari et al. 2016;Lam et al. 2017). The peak at 2894 cm -1 is attributed to stretching modes of C-H in methyl and methylene functional groups, representing the main functional groups of cellulose (Mandal and Chakrabarty 2011;Lam et al. 2017). ...
The cellulose used in this study was prepared from bleached soda bagasse obtained from the Pars paper factory. To prepare nanocellulose, the sample was subjected to alkaline pretreatment and then acid hydrolysis using 54% sulfuric acid at several temperatures (35, 50, 60, and 65 °C) and different times (30, 60, 90, and 120 min). Then, they were prepared using a centrifuge, dialysis bag, ultrasound, and freezer, respectively. The produced nanocellulose was characterized by transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). According to the results, temperatures of 50 and 90 °C were selected for the preparation of nanocellulose. The crystallization index of the hydrolyzed pulp and produced nanocellulose was 53 and 61%, respectively. The produced nanocellulose had a fibrillar shape.
... [2][3][4] Among the broad variety of known nanomaterials, polysaccharide-based nanomaterials have received considerable attention, due to their biodegradability, nontoxicity and renewable and abundant sources. [5][6][7] Starch, an agricultural biopolymer found in a variety of plant seeds, is a combination of amylose and amylopectin whose content varies depending on its botanic origin as well as variation among varieties of the same species. 8 Amylose is an essential linear biopolymer with mostly ⊍-(1-4)-linked D-glucopyranosyl units and less than 0.5% of the glucoses in ⊍- (1)(2)(3)(4)(5)(6) linkages; in contrast, amylopectin is a highly branched biopolymer with ⊍-1,4 glycosidic linkages and 2-5% of glucoses in ⊍-1,6 glucosyl bonds. ...
BACKGROUND
Starch nanocrystals have received considerable attention, due to their biodegradability, nontoxicity and renewable and abundant sources. The objective of this research is to compare the morphology, physicochemical characteristics and rheological properties of native (NSNC) and waxy rice starch nanocrystals (WSNC).
RESULTS
Both NSNC and WSNC exhibited a platelet‐like shape, and they tended to show square‐like platelet morphology with increasing initial amylopectin content. Compared to native starches, three weight loss stages of NSNC and WSNC in thermogravimetric analysis curves were observed, while the thermal depolymerization of NSNC started earlier than that of WSNC. The relative crystallinity of NSNC and WSNC was 38.6% and 48.3%, respectively, which were markedly higher than that of native starches. Fourier transform infrared spectra revealed that NSNC presented the highest ratio of 1045/1014 cm⁻¹ bands among the tested samples, which was probably due to the re‐association of retrograded amylose to double‐helices structure in NSNC. Moreover, the introduction of sulfur atoms on the surface of NSNC and WSNC was confirmed from the results of X‐ray photoelectron spectroscopy. At 5% (w/v) and 10% (w/v) concentration levels, all SNC suspensions exhibited a shear‐thinning behavior as the shear rate increased from 0.1 to 100 s⁻¹.
CONCLUSIONS
Starch nanocrystals obtained from native and waxy rice starch can be potentially used as reinforcement in biodegradable nanocomposites for packaging, fat replacers, thickening agents and emulsion stabilizers. © 2020 Society of Chemical Industry
... Moreover radiata pine wood nanofiber widths have been reported as 15nm, sisal nanofiber as 30.9 ± 12.5 nm, and bleached hemp nanofiber as 54 nm (Abe et al. 2007: Moran et al. 2008). However, according to Oksman and Sain (2006), since this is a new field there are still some disadvantages concomitant to the techniques employed in extracting cellulose nanofibers that should be considered. Examples on these include the separation processing techniques, fiber isolation process, and strong hydrogen bonding. ...
Cellulose nanofibers were isolated from kenaf core fibers by employing chemo-mechanical treatments. The morphologies and sizes of the fibers were explored with environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM). The results of chemical analysis showed that the cellulose contents of the bleached pulp fibers and nanofibers increased from 46% to 92% and to 94%, respectively. Most of the produced nanofibers had diameters in the range of 20 to 25 nm, whereas kenaf nanofibers ranged in diameter diameters from 10 to 75 nm. Fourier transform infrared spectroscopy (FTIR) analysis revealed the removal of lignin and the majority of the hemicelluloses from the kenaf core fibers. The thermogravimetric analysis (TGA), which was carried out to evaluate the thermal properties of the fibers, demonstrated that the thermal stabilities of these fibers were increased by the chemomechanical treatments. The results of X-ray analysis confirmed that chemical and mechanical treatments can improve the crystallinity of fibers.
... As with natural fi bers, surface modifi cation of CNF is critical for incorporation in composite material. Several reports have dealt in detail with the development of nanocomposites [23,[65][66][67], the inclusion of nanofi bers in composites [24, 50,[68][69][70][71][72], and the resultant barrier properties of the nanocomposites [6]. Approaches as those used in the case of cellulose fi bers can also be applied for CNF. ...
Cellulose nanofibrils (CNF), also known as nanofibrillar cellulose (NFC), are an advanced biomaterial made mainly from renewable forest and agricultural resources that have demonstrated exceptional performance in composites. In addition, they have been utilized in barrier coatings,
food, transparent flexible films and other applications. Research on CNF has advanced rapidly over the last decade and several of the fundamental questions about production and characterization of CNF have been addressed. An interesting shift in focus in the recent reported literature indicates
increased efforts aimed at taking advantage of the unique properties of CNF. This includes its nanoscale dimensions, high surface area, unique morphology, low density and mechanical strength. In addition, CNF can be easily (chemically) modified and is readily available, renewable, and biodegradable.
These facts are expected to materialize in a more widespread use of CNF. However, there is no clear indication of the most promising avenues for CNF deployment in commercial products. This review attempts to illustrate some exciting opportunities for CNF, specifically, in the development of
aerogels, composites, bioactive materials and inorganic/organic hybrid materials.
... In this study, cellulose nanofi brils were selected because of their sustainability, industrial ecology, eco-effi ciency , inexpensive cost, green chemistry, and abundance in nature. Cellulose nanofi brils have a high reinforcing effect and can improve the properties of the matrix (Sain and Oksman, 2005). Epoxy was chosen as the matrix due to its good physical properties and excellent bonding strength. ...
Epoxy resins have gained attention as important adhesives because they are structurally stable, inert to most chemicals, and highly resistant to oxidation. Different particles can be added to adhesives to improve their properties. In this study, cellulose nanofibrils (CNFs), which have superior mechanical properties, were used as the reinforcing agent. Cellulose nanofibrils were added to epoxy in quantities of 1%, 2%, and 3% by weight to prepare nanocomposites. Morphological characterization of the composites was done with scanning electron microscopy (SEM). Thermal properties of the nanocomposites were investigated with Thermogravimetric Analyzer (TGA/DTG) and Differential Scanning Calorimeter (DSC). SEM images showed that the cellulose nanofibrils were dispersed partially homogenous throughout the epoxy matrix for 1% CNF. However, it was observed that the cellulose nanofibrils were aggregated (especially for 2 and 3% CNFs) in some parts of the SEM images, and the ratios of the aggregated parts increased as the loading rate of the cellulose nanofibrils increased. The TGA curve showed that DTG and decomposition temperature of pure epoxy was higher than that of the nanocomposites. The DSC curve showed that the glass transition temperature (Tg) value of pure epoxy was found to be similar with Tg of the nanocomposites.
... Whilst research on ''Papreg'' has disappeared, the material is still produced and sold to date under various trade names, for example as Phenolkraft for electrical components. The concept of ''Papreg'' has been extended recently to sheets of nanocellulose [12][13][14][15][16][17][18], more commonly known as nanopapers [19]. ...
Nanocellulose is often being regarded as the next generation renewable reinforcement for the production of high performance biocomposites. This feature article reviews the various nanocellulose reinforced polymer composites reported in literature and discusses the potential of nanocellulose as reinforcement for the production of renewable high performance polymer nanocomposites. The theoretical and experimentally determined tensile properties of nanocellulose are also reviewed. In addition to this, the reinforcing ability of BC and NFC is juxtaposed. In order to analyse the various cellulose-reinforced polymer nanocomposites reported in literature, Cox-Krenchel and rule-of-mixture models have been used to elucidate the potential of nanocellulose in composite applications. There may be potential for improvement since the tensile modulus and strength of most cellulose nanocomposites reported in literature scale linearly with the tensile modulus and strength of the cellulose nanopaper structures. Better dispersion of individual cellulose nanofibres in the polymer matrix may improve composite properties.
... Consequently, crystalline regions within the specific soy fibers obtained may be weak in comparison to the other fibers using a similar extraction process (Alemdar and Sain 2008;Sain and Oksman 2006;Wang and Sain 2007a;Wang and Sain 2007b). The chemi-mechanical process applied could be too harsh which broke down crystalline regions revealing higher concentrations of amorphous material within the samples. ...
... Although the usage of CNF would provide significant interest in terms of mechanical and thermal properties, the water sensitive nature of CNF caused by the presence of plentiful hydroxyl groups has limited its application. In order to increase the usage of CNF, the incorporation of CNF with various ther-moplastic [1][2][3][4][5] and thermosetting polymers [6][7][8][9][10] has been developed for tailoring valuable properties, such as excellent optical characteristics, high thermal conductivity as well as a low absorption of water. ...
... Bionanocomposites are usually defined as a combination of two or more materials or phases in which one of the phases has at least one dimension in the nanometer range (1– 100 nm)1234. The terminology usually refers to a matrix for the more concentrated component that enables a phase continuum, while reinforcements are components that induce an enhanced performance (e.g. ...
Abstract The selection, synthesis, modification and shaping of biomaterials are complex tasks within the biomedical field. Human and plant tissues, such as, wood, bone and cartilage are structured at the nanometer level and exhibit a hierarchical structure up to the macroscale. Their morphological similarities enable the exploitation of lignocellulosic materials in the development of nanostructured composites targeting tissue engineering and regeneration. In this review, lignocellulosic materials and their chemical constituents are highlighted as promising alternatives for the development of drug-delivery vehicles and for the engineering or regeneration of bone and cartilage. Special focus is given to the recent developments of lignocellulosic bionanocomposite supports that induce cell attachment and proliferation. Chemical modifications techniques as well as composite processing methodologies that enhance the biomaterial performance are reviewed. It is anticipated the increasing interest in nanocellulose, bacterial cellulose, hemicellulose and lignin from natural resources as added-value biomedical materials in the near future.
A rapid increase in environmental problems is noticed, which are raised due to nonbiodegradable materials and affect the human health and environment very severely. Biodegradable and biopolymer‐based materials have great importance in solving environmental issues and resulting in critical industrial and academic research efforts to develop from green resources. The nanocomposite‐based biodegradable polymer is a very efficient and cost‐effective material for water purification for high‐quality drinking water. These polymers degrade and decompose naturally and decrease the garbage volume. Biodegradable polymers replace plastic for the packaging of food also. Much work has to be done to make biodegradable polymer efficient and cost‐effective to treat the polluted industrial water and sewage water for purifying water. Many biodegradable materials are present, have strong mechanical properties, are inexpensive, and can be disposed of in the soil. This chapter begins with introduction on degradable and nonbiodegradable polymers. It then covers the characteristics of biopolymers, cellulose, nanofillers, nanocomposites, synthesis process, and various uses of biodegradable polymers. The development of biodegradable polymer nanocomposites is a new challenge, and research in this field is also essential to save the environment.
Cellulose nanofiber (CNF) has been accepted as a valid nanofiller that can improve the mechanical properties of composite materials by mechanical and chemical methods. The purpose of this work is to numerically and experimentally evaluate the mechanical behavior of CNF-reinforced polymer composites under tensile loading. Finite element analysis (FEA) was conducted using a model for the representative volume element of CNF/epoxy composites to determine the effective Young’s modulus and the stress state within the composites. The possible random orientation of the CNFs was considered in the finite element model. Tensile tests were also conducted on the CNF/epoxy composites to identify the effect of CNFs on their tensile behavior. The numerical findings were then correlated with the test results. The present randomly oriented CNF/epoxy composite model provides a means for exploring the property interactions across different length scales.
Cellulose nanofibers (CNF) have the potential to adhere glass fiber reinforced plastics (GFRP) without a decrease in their mechanical properties. In this study, we inserted two CNF layers between GFRP laminates and evaluated their flexural properties. The insert of epoxy resin with CNF of 0.1wt.% layers, increased the flexural strength of GFRP by 125 %, whereas the flexural modulus of CNF layer inserted GFRP laminates was constant (28 ± 0.67 GPa). Moreover, we evaluated the flexural properties of a single CNF layer and revealed that even an extremely slight CNF (0.04 wt.%) addition, drastically increased the flexural strength and fracture elongation of epoxy resin by 130 % and 180 %, respectively.
The development of nanocellulose and nanocellulose-based composites and materials has attracted significant interest in recent decades because they show unique and potentially useful features, including abundance, renewability, high strength and stiffness, eco-friendliness, and low weight. This review addresses critical factors in the manufacturing of nanocellulose composites, followed by introducing and comprehensively discussing various nanocellulose composite processing techniques. The review also provides advances on rubber and thermoset polymer matrices, such as unsaturated polyester resin, formaldehyde resins, and polyethylene terephthalate, used to reinforce cellulose nanocrystals (CNCs) or cellulose nanofibers (CNFs). The paper concludes with new findings and cutting-edge studies on electrospun nanocellulose composites. Different aspects, including preparation methods, morphology, mechanical behavior, thermal properties, and barrier action, as well as comparisons of CNC- and CNF-reinforced rubbers or thermoset polymers and electrospun composites, are investigated.
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