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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.

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... 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). ...
Article
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. ...
Article
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.
... 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. ...
Article
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.
... 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. ...
Article
Full-text available
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.
... 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 ...
Article
Full-text available
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]. ...
Article
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.
... 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%. ...
... 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. ...
Article
Full-text available
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
... 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). ...
Thesis
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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.
... 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. ...
Article
Full-text available
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.
... 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. ...
Chapter
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