Nanocellulosic composites

Nanocellulosic fibrils can be used as a substrate for the production of precipitated calcium carbonate-nanocellulose composites. These, PCC-nanocellulose composites can contribute toward increasing the strength and optical properties of paper. We investigated formation and properties of a new composite paper composed of fibrillar fines and calcium carbonate as the base furnish in combination with cellulosic fibres as reinforcing elements. 

The conclusion to be drawn is that nanocellulose, with its characteristics— nanofibers size and distribution, mechanical properties, compatibility, and ability to regenerate—, has been considered an indispensable biomaterial in health area. Also, the nanocellulose composite scaffolds are biocompatible, appearing as a promising biomaterial, suitable for cell adhesion/attachment, which recommends them for wound-dressing or tissue engineering scaffolds (Kalia et al. 2011). 

A similar approach was also considered by Valentini et at [171] that successfully prepared homogeneous and conductive cellulose nanocrystals/graphene oxide (GO) composite films. The authors proved how the application of an electric current through the composite leads to the formation of a conductive NCC/GO film highlighting many exciting functional properties of graphene-based nanocellulose composites. 

Epoxy-based nanocellulose composites have the potential for wide application due to their high mechanical properties. Epoxy is a thermosetting copolymer, also known... 

Yu et al. [96] developed PHB/chemically modified nanocellulose composites, and the nanocomposites obtained exhibited great potential for application as medical materials. 

Kiziltas, A, Kiziltas, E. E., Boran, S., and Gardner, D. J. (2013). Micro- and nanocellulose composites for automotive applications, http //www. speautomotive.eom/SPEA CD/SPEA2013/pdf/BNF/BNF3.pdf. 

Because of the extraordinary supramolecular structure and exceptional product characteristics as high-molecular and high-crystalline cellulosics with a water content up to 99%, nanocelluloses require increasing attention. This review assembles the current knowledge in research, development, and application in the field of nanocelluloses through examples. The topics combine selected results on nanocelluloses from bacteria and wood as well as their use as technical membranes and composites with the first longtime study of cellulosics in the animal body for the development of medical devices such as artificial blood vessels, and the application of bacterial nanocellulose as animal wound dressings and cosmetic tissues. 

Keywords Nanocelluloses Membranes Composites Medical devices ... 

It should also be mentioned that the application of wood nanocellulose prepared by the described techniques - where the cell wall is further disintegrated by mechanical treatment - leads to lower-strength cellulose fiber-reinforced composites than in the corresponding BC materials [34]. 

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. 

Yano and Nakahara [15] used accessory polysaccharides to form composites with wood MFC/nanocelluloses. The disintegrated wood celluloses were mixed with starch as a binder and then hot-pressed between porous metal plates. Using a starch content of 2 wt %, the bending strength reached 310 MPa, compared to 250 MPa for unmodified fibers. Concurrently, the Young s modulus decreased from 16 to 12.5 GPa. When the starch content was 20 wt %, the bending strength decreased to 270 MPa. This indicates that added starch may act not only as a binder but also as a plasticizer. 

To improve the thermal, mechanical, and viscoelastic properties of cellulose acetate butyrate, it was reinforced with nanocellulose crystals prepared from BC by acid hydrolysis. Using this nanosized cellulose (Sect. 1) a significant improvement in the properties of the composites was demonstrated [57]. 

During the past 5-10 years a considerable increase in knowledge of the structure, chemistry, and processing of cellulose, as well as development of innovative cellulose products, has been observed. New frontiers involve sophisticated methods of structural analysis, environmentally safe cellulose-fiber technologies, as well as progressive work with bacterial nanocellulose, (bio)materials, and a broad spectrum of cellulose composites. 

The second chapter by Dieter Klemm, Dieter Schumann, Hans-Peter Schmauder, and coworkers focuses on the recent knowledge of cellulosics characterized by a property-determining supramolecular nanofiber structure. Topics in this interdisciplinary contribution are the types of nanocelluloses and their use in technical membranes and composites as well as in the development of medical devices, in veterinary medicine, and in cosmetics. 

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. 

According to Rebouillat et al. [55], cellulose nanoparticles mostly have two major thermal characteristics. The onset of thermal chemical degradation usually occurs at 300°C and 260°C for freeze-dried MCC and NCC (produced via sulfuric acid hydrolysis of the same MCC) respectively. In work by different authors it has been observed that the coefficient of thermal expansion of nanocellulose reinforced composite materials was improved in which coefficient of thermal expansion of the nanoparticle in the axial direction was at 0.1 ppm/K. The value is similar to that of quartz glass. Yano et al. [74] showed that the flexible plastic composites reinforced with this renewable resource have thermal expansion coefficients of 6 x 10 °C. ... 

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). 

Keywords Nanocellulose, nano composites, polyolefins, polypropylene, natural fibers... 

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