Cellulose nanocrystals mechanical properties

Yang J, Han CR, Zhang XM, Xu F, Sun RG (2014) Cellulose nanocrystals mechanical reinforcement in composite hydrogels with multiple cross-links correlations between dissipation properties and deformation mechanisms. Macromolecules 47 4077-4086... 

Ling, S., Huang, J., Chang, P. R., Wey, S., Xu, Y., Zhang, Q. (2013). Structure and mechanical properties of new biomass-based nanocomposite Castor oil-based pol3uirethane reinforced with acetylated cellulose nanocrystal, Carbol dnPo, 95, 91-99. 

The glass transition temperature (Tg) of cellulose reinforced composites is an important parameter which influences different properties of the resulting composite such as mechanical behavior, matrix chains dynamics and swelling behavior. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) are used to evaluate the Tg value of cellulose nanocomposites. In some cases, the addition of cellulose nanocrystals into polymer matrices does not seem to affect the... 

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. 

As previously mentioned, natural fibres present a multi-level organization and consist of several cells formed out of semi-crystalline oriented cellulose micro fibrils. Each microfibril can be considered as a string of cellulose crystallites, linked along the chain axis by amorphous domains (Fig. 19.10) and having a modulus close to the theoretical limit for cellulose. They are biosynthesized by enzymes and deposited in a continuous fashion. A similar structure is reported for chitin, as discussed in Chapter 25. Nanoscale dimensions and impressive mechanical properties make polysaccharide nanocrystals, particularly when occurring as high aspect ratio rod-like nanoparticles, ideal candidates to improve the mechanical properties of the host material. These properties are profitably exploited by Mother Nature. 

Table 14.1 Mechanical properties of NR films reinforced with cellulose nanocrystals and microfibrils (MF) cellulose extracted from the date palm tree obtained from the tensile tests Young s modulus ( ), strain at break ( R) and strength.

Zimmermann T, Pdhler E, Schwaller P (2005) Mechanical and morphological properties of cellulose fibril reinforced nanocomposites. Adv Eng Mater 7 1156-1161 Zoppe JO, Peresin MS, Habibi Y et al (2009) Reinforcing poly(8-caprolactone) nanofibers with cellulose nanocrystals. ACS Appl Mater Interfaces 1 1996-2004... 

Li Q, Zhou J, Zhang L (2009) Stmcture and properties of the nanocomposite films of chitosan reinforced with cellulose whiskers. J Polym Sci Part B Polym Phys 47 1069-1077 Lin N, Chen G, Huang J et al (2009) Effects of polymer-grafted natural nanocrystals on the stmcture and mechanical properties of poly(lactic acid) a case of cellulose whisker-graft-polycaprolactone. J Appl Polym Sci 113 3417-3425 Ljungberg N, Bonini C, Bortolussi F et al (2005) New nanocomposite materials reinforced with cellulose whiskers in atactic polypropylene effect of surface and dispersion characteristics. Biomacromolecules 6 2732-2739... 

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. ... 

As a result of their diverse architecture, different descriptors such as whiskers, nanowhiskers, cellulose nanocrystals, nano-crystalline cellulose, monocrystals or microcrystallites are used in literature to describe crystalline rod-like nanoparticles (Eichhom et al, 2010 Frone et al, 2011 Khalil et al, 2012), while terms such as microfibrils, microfibrillated cellulose or nanofibrillated cellulose are used to describe cellulosic nanoparticles that are obtained as a result of mechanical shearing disintegration process (Siqueira et al, 2010 Siqueira et al, 2011). In this paper, sources, isolation, property and applications of natural cellulose fibers are reviewed. 

EFFECTS OF SURFACE-MODIFIED CELLULOSE NANOCRYSTALS ON STRUCTURE AND MECHANICAL PROPERTIES OF NANOCOMPOSITES... 

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. 

Lin N, Chen GJ, Huang J, Dufresne A, Chang PR. Effects of polymer-grafted natural nanocrystals on the structure and mechanical properties of poly(lactic acid) a case of cellulose whisker-graft-polycaprolactone. J Appl Polym Sci 2009 113 3417-3425. 

Extrusion and impregnation, electrospinning, and multilayer films are other processes applicable for reinforced nanocomposites. Thus, preparation of cellulose whiskers reinforced with polylactic acid nanocomposites (by melt extrusion carried out by pumping the suspension of nanocrystals into the polymer melt during the extrusion process), using polyvinyl alcohol as a compatibilizer for the dispersion of cellulose whiskers within the polylactic acid matrix, was reported (de Menezes et al. 2009) bacterial cellulose whiskers incorporated into poly(oxyethylene) nanofibers by electrospinn to enhance the mechanical properties of electrospun fibers (Peresin et al. 2010) or the use of the layer-by-layer assembly technique, which maximizes the interaction between cellulose whiskers and a polar polymeric matrix (Bruno et al. 2009 Aulin et al. 2010), are some examples of nanocomposites reinforced by the last three methods. 

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. 

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