Nanocellulose films

Some authors have reported significant porosity in nanocellulose films [67-69], which seems to be in contradiction with high oxygen barrier properties, whereas Christin et al. measured a nanocellulose film density close to the density of crystalline cellulose (cellulose 16 crystal structure, 1.63 g/cm ), indicating a very dense film with a porosity close to zero. 

Changing the surface functionality of the cellulose nanoparticle can also affect the permeability of nanocellulose films. Films constituted of negatively charged cellulose nanowhiskers could effectively reduce permeation of negatively charged ions, while leaving neutral ions virtually unaffected. Positively charged ions were found to accumulate in the membrane [70]. 

Figure 1.4 Morphologies of cross-sectional surface of fractured (a) pure nanocellulose film, (b) nanocellulose/PANI composite film and (c) digital picture of bent nanoceUulose/PANI composite film.

The slight weight loss of both materials results from water evaporation below 150 °C. As seen from the curve, pure nanocellulose film appears to be decomposed at 220 °C, which corresponds to pyrolysis of cellulose (Nystrom et al., 2010). At lower temperature, the decomposition probably corresponds to the degradation of more accessible, and therefore more highly sulfated, amorphous regions. At higher temperatures above 300 °C, it is related to the breakdown of unsidfated crystal interior. 

The composite films containing 20 wt% PANI show two maximum decomposition rate peaks, one sharp, strong peak positioned at 222 °C, and the other wide and weak positioned at 237 °C, which is similar to those of pure nanocellulose (in Figure 1.9(b)). However, the peak moves to lower temperature. The two peaks of the composites synthesized at 0.1 and 0.5 wt% almost merge into one broad peak. The maximum decomposition rate decrease from 0.96%/°C for pure nanocellulose film to 0.69, 0.54, 0.44, and 0.43/°C, for the composites prepared at aqueous nanocellulose concentrations of 2.0, 1.0, 0.5, and 0.1%, respectively. 

As shown in Figure 1.10(a), pure nanocellulose film exhibits a sharp melting peak at 211 °C, indicating the crystalline stmcture of nanocellulose. However, this temperature is much lower than that of microcrystalline cellulose that is situated at 350 °C (Azubuike et al., 2012). It is probably due to smaller size, lower crystallinity, and lower polymerization degree of nanocellulose. PANI showed two main peaks during... 

Membranes and composites from cellulose and cellulose esters are important domains in the development and application of these polymer materials. The most important segment by volume in the chemical processing of cellulose contains regenerated cellulose fibers, films, and membranes, hi the case of the cellulose esters mainly cellulose nitrate and cellulose acetate as well as novel high-performance materials created therefrom are widely used as laminates, composites, optical/photographic films and membranes, or other separation media, as reviewed in [1], The previously specified nanocelluloses from bacteria and wood tie in with these important potentials and open novel fields of application. 

Taokaew, S., Seetabhawang, S., Siripong, R, and Phisalaphong, M. (2013). Biosynthesis and characterization of nanocellulose-gelatin films, atenal 6, 782-794. 

Both the TMO-derived and AH-derived nanocelluloses could homogeneously disperse in the PVA matrixes. The TMO/PVA films were better than AH/PVA films for tensile modulus and strength but were lower for elongation. The thermal behavior of the PVA nanocomposite films was more highly improved with addition of TMO-derived nanofibrils. It has been found that because of the mild reaction condition, the environmentally friendly attribute, the good quality of resulted nanofibrils and the superior properties of the final reinforced nanocomposites, the TMO technique has significant potential in the field of composite reinforcement. 

Referring to microbial cellulose applications, bacterial nanocellulose has proven to be a remarkably versatile biomaterial with use in paper products, electronics, acoustic membranes, reinforcement of composite materials, membrane filters, hydraulic fracturing fluids, edible food packaging films, and due to its unique nanostructure and properties, in numerous medical and tissue-engineered applications (tissue-engineered constructs, wound healing devices, etc). 

Aulin, C., Karabulut, E., Tran, A., Wagberg, L., Lindstrom, T. (2013). Correction to transparent nanocellulosic multilayer thin films on polylactic acid with tunable gas barrier properties. ACS (20), 10395-10396. 

Reddy, J. R, Rhim, J. W. (2014). Characterization of bionanocomposite films prepared with agar and paper-mulberry pulp nanocellulose., 480-488. 

Sun-Young, Lee, Jagan, M. D., In-Aeh, K., Ge-um-Hyun, D., Soh, Lee, Seong, Ok Han. (2009). Nanocellulose reinforced PVE composite films Effects of Acid Treatment and filler loading. Fibers and Polymers 10, 7782. 

Pereda M, Arnica G, Racz I, Marcovich NE (2011) Structure and properties of nanocomposite films based on sodium caseinate and nanocellulose fibers. J Food Eng 103 76-83... 

Kaushik A, Singh M, Verma G (2010) Green nanocomposites based on thermoplastie starch and steam exploded cellulose nanofibrils from wheat straw. Carbohydr Pol5mi 82(2) 337-345 Khan RA, Salmieri S, Dussault D, Uiibe-Calderon J, Kamal MR, Safrany A, Lacroix M (2010) Production and properties of nanocellulose-reinforced methyleellulose based biodegradable films. J Agri Food Chem 58(13) 7878-7885... 

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