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Dispersion of Wood Microfibers in a Matrix of Thermoplastic Starch and Starch-Polylactic Acid Blend
Abstract
The successful dispersion of cellulose fibers of submicrometer diameter in polymers has been restricted to solution-cast films so far. In this work, the dispersion of microfibers in biopolymers was investigated by melt-mixing using conventional processing equipment. Thermoplastic starch and a blend of starch and polylactic acid (PLA) were used as matrix materials. A suspension of cellulose microfibers less than 1 μm in diameter was prepared in water. This microfiber suspension was poured into molten thermoplastic starch to obtain fiber loadings up to 2%. The composites were compression molded into thin films roughly 0.25 mm thick. there was a 10% increase in tensile strength and a 50% increase in stiffness with each percentage increase in microfiber loading in the starch polymer. Similar improvement in tensile properties was also noted for a polymer system prepared by blending starch and PLA. Laser confocal microscopy images were analyzed to quantify microfiber dispersion at different composite processing parameters. This was the first work where successful dispersion of cellulose fibers of submicrometer was achieved in a composite prepared solely by the melt-mixing process.
... In order to overcome these drawbacks thermoplastic starch (TPS) is often modified by blending with other polymers (Cerclé, Sarazin, & Favis, 2013;Landreau, Tighzert, Bliard, Berzin, & Lacoste, 2009), the addition of fillers or reinforcements (Castillo et al., 2013;Kuciel, Kúzniar, Mikula, & Liber-Knéc, 2012;Ma, Yu, & Kennedy, 2005) or the preparation of nanocomposites (Bagdi, Müller, & Pukánszky, 2006;Castillo et al., 2013;Huang, Yu, & Ma, 2004). In order to maintain one of the most important advantages of starch, i.e. biodegradability, it is modified mostly with aliphatic polyesters and natural fibers (Avérous, Fringant, & Moro, 2001;Benezet, Stanojlovic-Davidovic, Bergeret, Ferry, & Crespy, 2012;Chakraborty, Sain, Kortschot, & Cutler, 2007;Huang et al., 2004;Sreekumar, Gopalakrishnan, Leblanc, & Saiter, 2010;Torres, Arroyo, & Gomez, 2007). ...
... A considerable number of papers deal with the effect of natural fibers on the properties of thermoplastic starch. Most of them study the influence of fiber type and amount usually determining (Soykeabkaew et al., 2012;Torres et al., 2007;Wollerdorfer & Bader, 1998), sisal (Girones et al., 2012;Sreekumar, Gopalakrishnan, et al., 2010;Torres et al., 2007;Wang, Thompson, & Liu, 2012), wheat straw (Benezet et al., 2012), hemp (Benezet et al., 2012;Girones et al., 2012;Kunanopparat, Menut, Morel, & Guilbert, 2008;Ochi, 2006), cotton (Benezet et al., 2012;Moriana, Karlsson, & Ribes-Greus, 2010;Prachayawarakorn, Sangnitidej, & Boonpasith, 2010), flax (Saiah et al., 2009;Soykeabkaew et al., 2004), ramie (Lu, Weng, & Cao, 2006;Sreekala et al., 2008), etc. Somewhat less papers deal with TPS/wood composites (Abbott, Palazuela Conde, Davis, & Wise, 2012;Agnantopoulou, Tserki, Marras, Philippou, & Panayiotou, 2012;Avérous & Boquillon, 2004;Chakraborty et al., 2007;Kuciel et al., 2012;Kuciel & Liber-Knec, 2009), although wood is cheaper and simpler to handle during processing. Some of the papers cited investigates the effect of fiber characteristics on mechanical properties and conclude that stiffness and strength increase both with increasing fiber length and content. ...
... The study of existing literature indicated that considering their practical relevance relatively small number of papers have been published on TPS/wood composites (Abbott et al., 2012;Agnantopoulou et al., 2012;Avérous & Boquillon, 2004;Chakraborty et al., 2007;Kuciel et al., 2012;Kuciel & Liber-Knec, 2009). Even less report systematic experiments carried out as a function of fiber content in a wide composition range (Abbott et al., 2012;Agnantopoulou et al., 2012;Avérous & Boquillon, 2004). ...
Thermoplastic starch (TPS)/wood composites were prepared from starch plasticized with 36wt% glycerol. The components were homogenized by dry-blending, extruded and injection molded to tensile bars. Tensile properties, structure, deformation, water adsorption and shrinkage were determined as a function of wood content, which changed between 0 and 40vol% in 7 steps. The modification of TPS with wood particles improves several properties considerably. Stiffness and strength increases, and the effect is stronger for fibers with larger aspect ratio. Wood fibers reinforce TPS considerably due to poor matrix properties and strong interfacial interactions, the latter resulting in the decreased mobility of starch molecules and in the fracture of large wood particles during deformation. Strong interfacial adhesion leads to smaller water absorption than predicted from additivity, but water uptake remains relatively large even in the presence of wood particles. The shrinkage of injection molded TPS parts is very large, around 10%, and dimensional changes occur on a very long timescale of several hundred hours. Shrinkage decreases to a low level already at 15-20vol% wood content rendering the composites good dimensional stability.
... It has been found that using reinforcing materials in a starch matrix is an effective method to obtain high-performance starch-based biocomposites (Cao et al., 2008.). Various types of cellulose fillers such as jute fibers, eucalyptus pulp fibers, flax fiber, tunicin, and ramie fibers, have been prepared and used as reinforcing agents in biocomposites (John et al., 2007; Chakraborty et al., 2007). Natural cellulosic nanocrystals have been gaining considerable interest because of their unique and attractive features (i.e. ...
... 3. In this study, BF showed dimensions similar to those of other biomass (Chakraborty et al., 2007; Yang, 2006, 2007 ). The lengths of single fiber were in the range of 0.01–1 mm, which is shorter than those of multicellular plant fibers such as flax, and the width was about 10– 50 lm, as shown inFig. ...
Using a method of combined HNO(3)-KClO(3) treatment and sulfuric acid hydrolysis, bamboo cellulose crystals (BCCs) were prepared and used to reinforce glycerol plasticized starch. The structure and morphology of BCCs were investigated using X-ray diffraction, electron microscopy, and solid-state (13)C NMR. Results showed that BCCs were of typical cellulose I structure, and the morphology was dependent on its concentration in the suspension. BCC of 50-100 nm were assembled into leaf nervations at low concentration (i.e. 0.1 wt.% of solids), but congregated into a micro-sized "flower" geometry at high concentration (i.e. 10.0 wt.% of solids). Tensile strength and Young's modulus of the starch/BCC composite films (SBC) were enhanced by the incorporation of the crystals due to reinforcement of BCCs and reduction of water uptake. BCCs at the optimal 8% loading level exhibited a higher reinforcing efficiency for plasticized starch plastic than any other loading level.
... According to CLSM data, nanofibers alone were significantly aggregated; xyloglucan nanofibers had slightly smaller aggregate sizes, and poly(diallyl dimethylammonium chloride) (PDADMAC) and carboxy methyl cellulose did not affect CNF aggregate size. 73 In one case, Chakraborty et al. 74 used a twin-screw mixer to disperse cellulose microfibrils in a water solution inside a PLA matrix; CLSM showed uniform fiber distribution. The authors 49 highlighted how Raman imaging microscopy can image aggregates of CNCs larger than 10 μm 2 ; however, staining CNCs with fluorophore allows for faster acquisition and improved reproducibility, but the results lead to an overestimation of aggregates. ...
Nanocellulose is one of the materials with applications in a wide range of technical disciplines, including electronics, oil recovery, robotics, and so on. To understand cellulose material qualities and behavior for product production, cellulose must be characterized separately or as part of a product using a range of approaches. Confocal laser scanning microscopy is one of the techniques that is currently underrepresented in the literature and is suitable to the cellulose domain. Here, we have shown how this characterization tool can uniquely and vastly aid in improving cellulose-based product design. In this brief Review, we looked at the application of confocal laser scanning microscopy in the cellulose domain, with a focus on nanocellulose due to its superior properties; confocal laser scanning microscopy can provide information on intricate structures such as thin layer-by-layer assembly, emulsion, gel stability, and collapse. Additionally, it can provide insight on the extent of enzymatic degradation of cellulose due to morphological changes; furthermore, the FRAP module was introduced briefly, with some of its fundamentals. Later, FRAP applications in primarily suspension and gels (homogeneous and heterogeneous) were introduced to provide examples of possible FRAP usage in cellulose science. In compiling this Review, we have used the most recent publications in the literature.
... High hydrophilicity affects negatively the tensile mechanical properties of these kinds of materials since it diminishes the interaction between the matrix and the reinforcements (Kuciel & Liber-Knec, 2009). Chakraborty, Sain, Kortschot, and Cutler (2007) also showed the same effect on samples dried at 80°C for 24 h before the test. They pointed out that materials measured under those conditions have better mechanical properties compared to samples conditioned at 50 RH%. ...
... According to the existing literature a relatively small number of papers have been published which consider the practical relevance of TPS/wood composites [7,[41][42][43][44][45][46]. There are even fewer paper about systematic experiments carried out as a function of fiber content in a wide composition range [2,41,42], furthermore, it is very difficult to find publications on the effect of processing methods on the properties of TPS/wood composites. ...
Thermoplastic starch (TPS)/wood composites in a wide composition range were prepared in an internal mixer followed by compression molding. Three types of lignocellulose fibers were used to study the effect of particle and surface characteristics on the processability as well as the mechanical and water absorption properties of the composites. The mechanical properties of these composites were also compared with those of the composites processed by injection molding in an earlier study, and the effect of processing technology on the mechanical properties was also investigated. The processing of TPS/lignocellulose composites in the internal mixer demanded more energy with increasing amount and aspect ratio of the fibers as a result of a network formation. Only a small variation among the dispersion component of the surface tension of the wood samples was found, and almost no difference in the stiffness and strength of the composites prepared in the internal mixer was observed. The results proved that the influence of the processing method on the stiffness and strength of the composites depends strongly on the aspect ratio of the wood particles. Increasing anisotropy results in increasing difference in the mechanical properties of the composites prepared by different methods. The equilibrium water uptake of the fibers and the composites depended especially on the size and, consequently, on the specific surface area of the wood fibers.
... Reinforcement with cel- lulose nanofibrils is one of the approaches to overcome these problems. CNFs/ starch composite presents improved thermomechanical behavior (Dufresne and Vignon 1998), bending strength ( Yano and Nakahara 2004), tensile strength, and tensile modulus (Dufresne et al. 2000;Chakraborty et al. 2007a) compared with pure starch. Also, the barrier properties were significantly improved when CNFs were added in amylopectin, which is one of the two components of starch. ...
Cellulose nanofibrils (CNFs) are one type of nanostructured cellulosic materials with a width below 100 nm and a length of several micrometers. CNFs have many desirable characteristics, such as a unique rheological behavior, high mechanical and barrier properties, and lightweight. They are produced from cotton, wood, grasses, and other lignocellulosic biomass. Thus, CNFs are abundantly available and can be a cheap alternative to petroleum-based polymers. Manufacturing of CNFs consists of pretreatment process and mechanical disintegration process. The pretreatment process makes cellulose fibers more responsive to be fibrillated, and pretreated fibers are mechanically disintegrated into nano-sized fibers in the next stage. Moreover, the type of raw materials can be a principal factor that affects CNFs production and properties. In this chapter, we reviewed the production, characterization, and the current applications of nanocellulose for food industries, such as food additives, food packaging, and coating.
... Besides solution casting, the dispersion of CNFs in TPS has been also performed via melt mixing by Chakraborty et al. [149]. Microfibrillated cellulose suspension was poured into molten TPS to obtain fiber loadings up to 2 wt% and then composites were compression molded into thin films. ...
In this work, the different cellulosic materials, namely cellulose and lignin are analyzed. In addition, the starch-containing matrices (isolated starch and flour) reinforced with cellulosic materials to be used in packaging applications are described. Many efforts have been exerted to develop biopackaging based on renewable polymers, since these could reduce the environmental impact caused by petrochemical resources. Special attention has had the starch as macromolecule for forming biodegradable packaging. For these reasons, shall also be subject of this review the effect of each type of cellulosic material on the starch-containing matrix-based thermoplastic materials. In this manner, this review contains a description of films based on starch-containing matrices and biocomposites, and then has a review of cellulosic material-based fillers. In the same way, this review contains an analysis of the works carried out on starch-containing matrices reinforced with cellulose and lignin. Finally, the manufacturing processes of starch/cellulose composites are provided as well as the conclusions and the outlook for future works.
... The tensile strength and elastic modulus of the composites increased significantly comparing to that of the pure thermoplastic starch. A lot of other works were devoted to NFC/starch composites (Dufresne et al. 2000;Chakraborty et al. 2007;Mondragón et al. 2008;Takagi and Asano 2008;Savadekar and Mhaske 2012;Hietala et al. 2013). ...
One of the main challenges in the context of biocomposites development is to replace petroleum-based materials with bio-based. Because of their natural origin, relatively high strength and the ability to form transparent products, cellulose nanofibers have a large potential for application in the composite materials. This work was focused primarily on the optimization of cellulose nanofiber production methods using biochemical and mechanical treatments, secondly on their rheological and structural properties in an aqueous medium and thirdly on the production of latex-based composites. The questions of homogeneous dispersion of cellulose nanofibers in the matrix and the interactions between these components for the purpose of matrix reinforcement were particularly addressed.
... that the conditioning treatment used (60 °C for 5 h) in the present study was able to affect the function of the plasticizer, causing the starch chains to have better packing, resulting in better organization due to more intense interactions of macromolecules (amylase and amylopectin), which has been reported in previous studies (Lomelí et al. 2011). Chakraborty et al. (2007 showed the same effect by placing samples at 80 °C for 24 h and mentioned that the materials under these conditions showed better mechanical properties in relation to the composites conditioned at a relative humidity of 50%. Guimarães et al. (2010) reported values from 1.7 to 4.3 (MPa) for tensile strength, 24.6 to 484.0 (MPa) for elast ...
The present work inspects the preparation of bio-composites of cassava starch with particles of eucalyptus wood through the application of a novel method of thermal compression. Bio-composites with different amounts of wood particles (5 to 30%), with particle sizes of 4 and 8 mm, were obtained. Chemical and mechanical evaluation of these samples was carried out using optical microscopy, infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and the moisture absorption effect. The effect of the amount and size of the wood particles was tested by comparison with a thermoplastic matrix sample. Results from these evaluations demonstrated that the thermo-compression method produced bio-composites with a distribution of particles in the matrix that contributed to an increase in their tensile strength. This mechanical property is also enhanced by interfacial adhesion between the matrix and particles, as confirmed by SEM. Furthermore, the maximum amount of particles in the bio-composites (30%) showed the maximum resistance to moisture absorption. Temperature and time parameters contributed to the formation of diffraction patterns V-H and E-H as a consequence of the structural disruption of native starch. Finally, FTIR showed the chemical compatibility between the starch, glycerol, and wood particles.
... But in spite of many advantages, starch films show some disadvantages too, like poor mechanical properties, high brittleness and sensitivity to water due to their highly hydrophilic nature. In order to improve the mechanical properties and water resistance, starch can be modified by several methods such as blending with synthetic or natural polymers, being reinforced with fillers like cellulose crystallites [1][2][3][4][5][6][7][8][9], nanoclay [10][11][12], etc. and also by cross linking [13]. Synthesis and characterization of polyvinyl alcohol/cellulose nanoparticle reinforced films were prepared by Ibrahim et al. [14]. ...
Jute micro/nanofibrils (JNF) were prepared from jute by acid hydrolysis route. The jute nanofibres were characterized with the help of Transmission Electron Microscope (TEM). Starch/polyvinyl alcohol (PVA) based biocomposite films reinforced with JNF at different loading of 5, 10 and 15wt.% were prepared by solution casting method, incorporating glycerol as a plasticizer. These biocomposite films were characterized by mechanical characterization, thermal analysis, moisture uptake behaviour, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The 10wt.% JNF loaded films exhibited best combination of properties.
... Choi and Simonsen (2006) prepared cellulose nanocrystals from cotton with 65% sulfuric acid followed by neutralization and sonication. Chakraborty et al. (2007) prepared microfibers (MF) from wood,\1 lm in diameter, by combination of high shear and high impact and isolated by filtration through a mesh size of 60. Bhatnagar and Sain (2005) prepared MCC by acid hydrolysis after pretreatment of fiber with alkali. ...
Microcrystalline cellulose (MCC) particles are mostly prepared by acid hydrolysis of various agro sources. Acid hydrolysis
is usually carried out with high concentration (64wt%) of sulfuric acid. Here, an attempt has been made to optimize lower
acid concentrations which can effectively produce MCC particles. In this work, different concentrations of sulfuric acid (20,
30, 35, 40, 47 and 64wt%) have been used to prepare MCC particles, which have been characterized by XRD, particle size analysis,
scanning electron microscopy, transmission electron microscopy, nanoindentation and thermogravimetric analysis. MCC prepared
with 35 and 47% sulfuric acid (MCC 35 and MCC 47) had finest particle size and fibrils were produced in the range of 15–25nm.
MCC 20 showed wide particle size distribution, indicating low breakdown of the cellulose chains. The energy absorption behavior and mechanical properties of the MCC pellets were determined by nanoindentation test for the
first time. MCC 35 pellets exhibited lowest modulus and hardness.
... Choi et al. [5] prepared cellulose nanocrystals from cotton with 65% sulphuric acid followed by neutralization and sonication. Chakraborty et al. [6] prepared microfibres (MF) from wood, less than 1 lm in diameter, by combination of high shear and high impact and isolated by filtration through a mesh size of 60. Bhatnagar et al. [7] prepared MCC by acid hydrolysis after pretreatment of fiber with alkali. ...
The main objective of this work was to extract microcrystalline cellulose (MCC) particles from different cellulosic resources
like cotton, jute, newsprint, filter paper and investigate their suitability as green reinforcing material in biocomposites.
The MCC particles were extracted by acid hydrolysis with 64% sulphuric acid. The processing parameters like acid concentration,
temperature, time and mechanical force were kept constant. The MCC particles were studied by transmission electron microscopy
(TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size analysis, Fourier transform infrared spectroscopy
and thermogravimetric analysis. The viscoelastic properties of the MCC particles were investigated with the help of nanoindentation
technique for the first time. The acid hydrolysis changed the %crystallinity and crystallite sizes of the MCC particles compared
to their source materials. The modulus and hardness of the MCC particles varied significantly depending on their precursors.
The presence of non-cellulosic constituents controlled the deformation behaviour of the MCC particles. The thermal stability
of the MCC particles was correlated with the tangling effect of the flexible cellulose chains.
KeywordsMicrocrystalline cellulose-Viscoelastic behavior-Hardness-Modulus-Nanoindentation test
Blends were prepared from poly(lactic acid) (PLA) and thermoplastic starch (TPS) to study component interactions, structure and properties. Starch was plasticized with glycerol at two levels, at 36 and 47 wt%. The results unambiguously showed that the interaction of the two components is weak. The investigation of the possible partitioning of glycerol in the two phases indicated that most of the plasticizer is located in the TPS phase. Thermodynamic modeling predicted some dissolution of PLA in TPS which was assisted by the presence of the plasticizer, but TPS did not dissolve in PLA at all. No tangible proof was found for the formation of a glycerol rich phase in TPS, the relaxation transition assigned to this phase was rather explained with the movement of smaller structural units of starch molecules. Weak interfacial adhesion does not allow stress transfer through the interface resulting in poor strength and small deformation.
The processing of polymeric composites reinforced with nanosized rigid particles is an emergent area that is appealing both scientific and industrial interests. Over the last years, many efforts have been dedicated to the use of nanoparticles from natural resources as reinforcing elements for polymeric matrices. In this sense, cellulose microfibrils are an attractive alternative to mineral fillers in multi-component polymer systems: their low cost, low density, high stiffness, consumable property and biodegradability constitute the major incentives for their use. It is well known that from these microfibrils it is possible to obtain cellulose whiskers, which are rigid rod shaped monocrystalline cellulose particles. The main characteristics of cellulose whiskers are their large aspect ratio and Young's modulus, which provide them with a huge potential as reinforcing elements of polymeric matrices. This paper highlights the developments on preparation, characterization and dispersion of cellulose nanoparticles into polymer matrices, as well as the fields of application of these natural-based nanocomposites.
During the last decades, there has been a continuous increase in the production of commodity plastic products because of their low production cost, excellent mechanical properties, as well as chemical, weather and biodegradation resistance. The duration of use of plastic materials is relatively short compared to their life time; it ranges from several months to few years, depending on the conditions of use and environment. Now a day the scientific world is focusing is the development of starch based composites. These materials are available largely from natural resources and are 100% degradable. This chapter presents a brief description about the different biodegradable matrices as well as the different components, structures, transformations and properties of starch-based matrices and biofibers. The reinforcing effect of macro-fibers s well as like nano fibers like whiskers or nanocrystals on starch as matrix will be discussed.
Microfibrillated cellulose (MFC), also known as nanocellulose, is acquired by chemical and/or mechanical means from a pure cellulose raw material, predominately as a thixotropic hydrogel. Currently it is produced at pilot plant scale, with ongoing efforts for commercial scale production. Current world wide pilot plant investment is approximately NZ$ 50M with a combined capacity of 150 tonnes annually, with plants in Sweden, Germany, Japan and soon the US. In addition there are related cellulose whiskers and nanocrystalline cellulose pilot plants coming on-line. Nanocellulose material is potentially an important future revenue stream for pulp producers. The interest in MFC adoption is to utilize its outstanding optical, gas barrier, strength and thermal stability properties to create high value products from potentially low value raw material. The basic technology and material has been known since the beginning of the 80's, but high energy cost and lack of clear applications has until recently hampered its widespread adoption. Outstanding technical challenges include irreversible agglomeration upon dewatering and substrate/matrix compatibility. This review summarises recent progress in MFC research, specifically highlighting progress in overcoming dispersion and unintentional agglomeration issues. In addition it discusses potential applications of MFC in packaging.
Microfibrillated cellulose (MFC), also known as nanocellulose, is acquired by chemical or mechanical means from a pure cellulose raw material, predominately as a thixotropic hydrogel. Currently it is produced at pilot plant scale, with ongoing efforts for commercial scale production. Current world wide pilot plant investment is approximately NZ$ 50M with a combined capacity of 150 tonnes annually, with plants in Sweden, Finland, Germany, Japan and the US. In addition there are related cellulose whiskers and nanocrystalline cellulose pilot plants coming on-line. Nanocellulose material is potentially an important future revenue stream for pulp producers. The interest in MFC adoption is to utilize its outstanding optical, gas barrier, strength and thermal stability properties to create high value products from potentially low value raw material. The basic technology and material has been known since the beginning of the 1980's, but high energy cost and lack of clear applications has until recently hampered its widespread adoption. Outstanding technical challenges include irreversible agglomeration upon dewatering, substrate and matrix compatibility. This review summarises recent progress in MFC research, specifically highlighting progress in overcoming dispersion and unintentional agglomeration issues. In addition it discusses potential applications of MFC in packaging.
Biobased nanoscale fibres are unique with respect to their high aspect ratio, remarkable strength, renewability and biodegradability, which make them excellent candidates as reinforcements in producing nanocomposites. The present chapter reports the various techniques of isolation and surface modification of biobased nanoreinforcements, in particular cellulose nanoreinforcements. Strategies related to integration and efficient dispersion of these engineered nanoscale biofibres into common matrices have been highlighted. The chapter also reviews the properties, applications and fundamental challenges related to biobased nanocomposites and the current research efforts that are being directed towards solving these problems and in widening the potential application areas of these materials.
A series of ecofriendly glycerol plasticized starch/polyvinyl alcohol (PVA) bionanocomposite films were prepared by the solution casting method using cellulose nanofibril (CNF) particles as reinforcement fillers. CNF particles were prepared by acid hydrolysis of cotton slivers. The bionanocomposite films had 3, 6, 12, and 18 wt% of CNF loading. The nanostructure of the CNF was confirmed by transmission electron microscopy. The films were characterized by FTIR, water diffusivity property at 93% RH, and thermogravimetric analysis. Diffusivity of the films was found to be significantly dependent on the CNF content of the films and on its dispersion in the blend matrix. Diffusion coefficients of the 6 and 12 wt% CNF-reinforced films were lower than that of the blank film. Incorporation of CNF enhanced the thermal stability of the films by shifting the onset of degradation to a higher temperature and also by increasing the char residue.
This chapter highlights the impact of cellulose nanofibers (CNFs) on the thermal properties of polymers and provides insight into the composite morphologies down to the molecular scale. With a particular focus on semicrystalline biodegradable polymers, the chapter attempts to decipher the role of CNF surface attributes, shape, and loading amounts on morphological and thermal properties. Thus, the chapter reviews the theoretical framework of polymer transitions and crystallization kinetics for semicrystalline polymers. Finally, it discusses the morphology and thermal behavior (other than thermal stability) of specific cellulose/ biopolymer matrix materials.
Micro crystalline (MC) cellulose particles were prepared from cotton slivers by acid hydrolysis. Starch/Polyvinyl alcohol (PVA) based biocomposite films reinforced with microcrystalline cellulose were prepared by solution casting method, incorporating glycerol as a plasticizer. Reinforcements were done by using cellulose microcrystals with different weight percent for example 2, 5, 10 and 15. These biocomposite films were characterized by X-ray diffraction (XRD), mechanical characterization, permeability test, water uptake behavior, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties, moisture uptake and water vapor transmission rate of the biocomposite films were found to be significantly dependent on the MC cellulose content of the films. SEM investigation was undertaken to determine the size of the MC cellulose particles formed and also to investigate the dispersion of MC cellulose particles in the starch/PVA blend matrix.
Synthetic polymers are important in many branches of industry, particularly in the packaging industry. However, it has an undesirable influence on the environment and causes problems with deposition of waste and consumption. Therefore, there is a tendency to replace the polymer with biodegradable polymer that undergoes a process. This review summarizes the data on consumption, the level of biodegradation, the reliability of commercialization and production from renewable sources. Some biodegradable plastics that have been commercialized are starch based plastics, bacteria based plastics, soy based plastics, cellulose based plastics, lignin based plastics and natural fiber reinforced plastics. Production of this kind of material and its introduction to the market is important for the natural environmental.
In this work, the addition of wood particles and wood polymer components (namely, cellulose, lignin)
within biopolymer matrix was investigated by the casting method when solution-cast films were
obtained. Thermoplastic corn starch and blends of starch and wood particles/wood polymers were
used as matrix materials. Fillers including wood sawdust, cellulose and lignin were subsequently
added within thermoplastic starch matrix in order to obtain filler loading of 20 wt% based on the
amount of corn starch. Composite film samples with a thickness of around 0.25 mm were obtained.
FTIR spectroscopy analysis, X-ray diffraction method, water sorption tests, and SEM investigation
were used for characterization of resulted biocomposite films. Thermal stability was further investigated
by simultaneous thermal analysis in order to evaluate the influence of the filler upon starch
based polymer matrix properties.
Cellulose micro fibres have been gaining widespread attention for their use in potential medical applications mainly because of their unique microstructure and renewability. Several synthesis routes have been explored to produce cellulose microfibers such as mechanical refining, enzymatic treatment or bacterial synthesis. In this article, different isolation techniques and the resultant microstructure of cellulose microfibers have been discussed in detail along with their biocompatibility and applications in several biomedical sectors.
“Green”/bio-based blends of poly(lactic acid) (PLA) and cellulolytic enzyme lignin (CEL) were prepared by twin-screw extrusion blending. The mechanical and thermal properties and the morphology of the blends were investigated. It was found that the Young’s modulus of the PLA/CEL blends is significantly higher than that of the neat PLA and the Shore hardness is also somewhat improved. However, the tensile strength, the elongation at break, and the impact strength are slightly decreased. Thermogravimetric analysis (TGA) shows that the thermal stability of the PLA is not significantly affected by the incorporation of the CEL, even with 40 wt% CEL. The results of FT-IR and SEM reveal that the CEL and the PLA are miscible and there are efficient interactions at the interfaces between them. These findings show that the CEL is a kind of feasible filler for the PLA-based blends.
Tartaric acid modified starch microparticles (TA-SM) previously obtained using the dry preparation technique were introduced as filler within glycerol plasti-cized-corn starch (GCS), the composites being prepared by casting process. The effects of cellulose addition within the TA-SM-GCS matrix on the structure, surface properties and water sorption, as well as mechanical and thermal properties of starch-based composite films were investi-gated. The water resistance and thermal stability were slightly improved through addition of high content of cel-lulose due to the inter-component H-bonding between components. The evaluation of mechanical properties evi-denced a significant increase of the tensile strength of the composites with increasing the content level of cellulose.
Nanotechnology is of great importance in almost all modern day industries targeting high quality, efficiency and market potential. The large interest in the nano-scale range is due to the fact that nanomaterials can have enhanced properties, as compared to the same material with larger particle size. The modification of cellulose into different types of micro- and nano-structures has been reported in literature. In papermaking, nanotechnological advances were reported about a decade ago, though it could not be commercialized at a large scale. Nanofiber, nanofiller, nanocomposites and nanoscale chemicals to be used in pulp and paper applications are in main focus. Because of the wide abundance, renewable and environmentally benign nature, and outstanding mechanical properties of nano-based cellulosic materials, great attention has been paid to their use in pulp and paper, and other industries. There are a few challenges associated with their efficient use at a commercial scale, such as cost, lack of compatibility among materials and knowledge gap. This review of recent work discusses the manufacturing, application and properties of different nanoparticles and nano-based technological developments reported by researchers worldwide, related to cellulose and paper manufacturing.
Biodegradability, renewability and high specific strength properties of cellulose nanofibres and microfibrils have made them
very attractive in nano-biocomposite science. Treatment of natural fibers with suitable enzymes or fungus has been found to
substantially alleviate the high energy requirement associated with the isolation of cellulose nanofibers via high shear refining
and subsequent cryocrushing. This article briefly describes a novel enzymatic fiber pretreatment developed to facilitate the
isolation of cellulose nanofibres and explores the effect of pre-refining of fibers on the effectiveness of bio-treatment.
Soft wood Kraft pulp was pre-sheared to different degree and treated with a genetically modified fungus isolated from fungus
infected Dutch elm tree. Cellulose nanofibres were isolated from these treated fibers by high shear refining. The percentage
yield of nanofibres from pre-refined fibers in the less than 50nm range showed a substantial increase and at the same time
the number of revolutions required during the high shear refining to attain a comparable level of nanofibres isolation decreased.
This observation may be attributed to the better fiber internal accessibility of the enzymes due to loosening up of the fibers
and increased number of fiber ends as a result of pre-refining.
KeywordsCellulose nanofibres/microfibrils–Cellulose microfibril isolation–Enzyme pre-treatment–Hydrogen bonds–PFI refining
Abstract 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.
Polylactide (PLA) is one of the most innovative materials being actively investigated for a wide range of industrial applications. The polymer is a linear aliphatic thermoplastic polyester which is biodegradable as well as biocompatible, which makes it highly versatile and attractive to various commodities and medical applications. A large variety of nanoparticles of different nature and size can be blended with PLA, therefore, generating a new class of nanostructured biomaterials or nanocomposites with interesting physical properties and applications. PLA based nanostructured biomaterials are the focus of this review article, throwing light on their preparation techniques, physical properties, and industrial applications. Structural characteristics and morphological features of PLA based nanocomposites have been explained on the basis of X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Depending upon the nature and characteristics of the nanoparticles, the ultimate properties of the resulting nanocomposite materials can be tailored. Biocompatible materials such as carbon nanotubes, cellulose nanowhiskers, hydroxyapitite, etc. could be incorporated into the PLA matrix, which increase the potential of PLA for biomedical applications. Applications of PLA based nanostructured materials in different areas have been summarized.
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