Cellulose nanocrystals thermal properties

However, thermal stability and mechanical properties of ANP are poor. Young s modulus and tensile strength of this kind of nanocellulose are 10—20 times lower than those of cellulose nanocrystals (loelovich, 2012a,b). Therefore, ANP of cellulose cannot be suitable as a reinforcing nanofiller. 

Xu, S., Girouard, N., Schueneman, G., Shofner, M.L., Mtacdith, J.C. Mechanical and thermal properties of waterborne epoxy composites containing cellulose nanocrystals. Polym. 54, 6589-6598 (2013)... 

In order to prepare PLA nanocomposites with highly dispersed cellulose nanocrystals and porous PLA-based scaffolds with enhanced mechanical properties and thermal stability, CNCs have been incorporated into PLA fibres by electrospinning method. Fibrous biocomposite mats consisting of PLA and CNCs have been electrospun from solvent or solvent mixtures such as l,l,l,3,3,3-hexafluoro-2-propanol (HFP), DMF/chloro-form and DMF/tetrahydrofuran (THF). The electrospun PLA/CNCs bionanocomposites have demonstrated rapid in vitro biodegradability and cytocompatible properties, and could be potentially suitable in tissue engineering. ... 

Siqueira G, Bras J, FoUain N, Belbekhouche S, Marais S, Dufresne A. Thermal and mechanical properties of bio-nanocomposites reinforced by iMffa cylindrica cellulose nanocrystals. Carbohydr Polym 2013 91 711-717. 

The principal characteristics observed with the addition of cellulose nanocrystals to starch-based materials led to improvements in the mechanical properties, thermal properties (represented by an increase in the glass transition temperature, Tg), and moisture resistance. 

The reason for the nanocomposites increased thermal properties is associated to the relocation of the plasticizer(s), water inclusive, from the starch matrix to the cellulose nanocrystals surfaces, which decreases the plasticization effect on the amorphous regions (Angles and Dufresne 2000, 2001). They proposed the formation of the transcrystaUine zone, around the cellulose nanofillers in order to explain the results obtained in plasticized waxy maize starch reinforced with tunicin nanowhiskers. This effect is caused by the recrystallization of amylopectin chains assisted by the plasticizer accumulation and the nucleating effect of C-NW. 

Yamashita K, Funato T, Suzuki Y, Teramachi S, Doi Y (2003) Characteristic interactions between poly(hydroxybutyrate) depolymerase and poly [(R)-3-hydroxybutyrate] film studied by a quartz crystal microbalance. Macromol Biosci 3 694—702 Yang L, Setyowati K, Li A, Gong S, Chen J (2008) Reversible infrared actuation of carbon nanotube-liquid crystalline elastomer nanocomposites. Adv Mater 20 2271-2275 Yu C, Shi L, Yao Z, Li D, Majumdar A (2005) Thermal conductance and thermopower of an individual single-wall carbon nanotube. Nano Lett 5 1842-1846 Yu H, Qin Z, Zhou Z (2011) Cellulose nanocrystals as green fillers to improve crystallization and hydrophilic property of poly(3-hydroxybut3uate-co-3-hydroxyvalerate). Prog Nat Sci Mater Int 21 478 84... 

The possibility to combine different reinforcement phases in a polymer matrix was also recently considered in order to obtain multifunctional systems with increased mechanical and thermal properties providing also an antimicrobial response. In a recently accepted paper [160] Fortunati et al. demonstrated the high potential benefits offered by nanotechnology in the development of tailor-made nanobiocomposites with specific applications by the combination of two different synthesized nanostructures inorganic nanoparticles and cellulose nanocrystals in a biodegradable polymer matrix. 

Cellulosic materials, such as cotton and wood pulp, when subjected to acid hydrolysis yield defect-free, rod-like crystalline residues called as cellulose nanocrystals. These are often referred to as microcrystals, whiskers, nanocrystals, nanoparticles, microcrystallites, or nanofibres. Their nanoscale dimension, high surface area, high specific strength, thermal, and mechanical strength along with gas barrier properties increase its merit towards its usage in advanced applications like reinforcement in polymeric matrix to form nanocomposite materials, chemical transformations and so on. 

The interest on natural-based materials for reinforcement of polymer matrices has been increased in recent years. In this section, we focus the attention on the reinforcement effect of cellulose, starch or chitin fillers on the thermal properties of PU-based materials. These nanofillers can be obtained from natural and renewable sources and can be processed in several ways presenting different morphologies, such as nanowhiskers, nanofibers, or nanoparticles. In particular, cellulose can be processed by hydrolysis reaction of different cellulose sources in order to obtain cellulose nanocrystals (CNC) [72]. In Figure 7.3, the CNC structure is shown. The CNC present a diameter of about 19 nm. [72]. 

Lu, H.J., Gui, Y., Zheng, L.H., Liu, X., 2013. Morphological, crystalline, thermal and physicochemical properties of cellulose nanocrystals obtained fiom sweet potato residue. Food Research International 50, 121—128. 

Ten et al. [12] studied the mechanical and thermal properties of PHB-HV/cellulose whisker nanocomposites and found that the NCC reinforcement increases the mechanical properties due to the strong interactions between these two phases. Compared with the pure PHB-HV, the tensile modulus of composites reinforced with 5% cellulose whiskers increased 77%. According to authors, the Young modulus increase can be attributed to the creep resistance of the polymer chains due to the presence of nanocrystals. The tensile strength of the nanocomposites also ino-eased indicaling a large interfadal adhesion between the polymer and whiskers. 

Yu H-Y, Qin Z-Y, Liu Y-N, Chen L, Liu N, Zhou Z. Simultaneous improvement of mechanical properties and thermal stability of bacterial polyester by cellulose nanocrystals. Carbohydr Polym 2012 89 971-8. 

Arrieta MP, Fortunati E, Dominici F, Rayon E, Ldpeza J, Kenny JM. Multifunctional PLA-PHB/cellulose nanocrystal films processing, structural and thermal properties. Carbohydr Polym 2014 107 16-24. 

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