Cellulose nano reinforcement

Pandey, J. K., Chua, W. S, Kima, C. S., Leeb, C. S., and Ahn, S. H. (2009). Bio-nano reinforcement of environ mentally degradable polymer matrix by cellulose whiskers from grass,... 

The cellulose based materials that are used as nano-reinforcements are cellulose nanocrystals (i.e. whiskers and nanospheres), nanofibrillated cellulose, regenerated cellulose nanoparticles and electrospun nanofibers. A wide range of polymer matrices have been used to form cellulose nanocomposites. Synthetic polymers such as polypropylene, poly(vinyl chloride) (PVC) [102], waterborne epoxy [103], waterborne polyurethane [104], polyurethane [105], poly-(styrene-co-butyl acrylate) [106], poly(oxyethylene) [107], polysiloxanes [108], polysulfonates [109], cellulose acetate butyrate [110,111], poly(caprolactone) [112], poly(viny 1 alcohol) [113] and poly (vinyl acetate) [114]. Different biopolymers such as starch-based... 

In this chapter we have reviewed some of the most important characteristics of cellulose and cellulose based blends, composites and nanocomposites. The intrinsic properties of cellulose such as its remarkable mechanical properties have promoted its use as a reinforcement material for different composites. It has been showed that cellulose is a material with a defined hierarchy that tends to form fibrillar elements such as elementary fibrils, micro fibrils, and macro fibers. Physical and chemical processes allow us to obtain different scale cellulose reinforcements. Macro fibers, such as lignocellulosic fibers of sisal, jute, cabuya, etc. are used for the production of composites, whereas nano-sized fibers, such as whiskers or bacterial cellulose fibers are used to produce nanocomposites. Given that cellulose can be used to obtain macro- and nano-reinforcements, it can be used as raw material for the production of several composites and nanocomposites with many different applications. The understanding of the characteristics and properties of cellulose is important for the development of novel composites and nanocomposites with new applications. 

Abstract Nature is gifted with several nanomaterials which could be obtained from different animal and plant sources. Cellulose, chitin and starch are abundant, natural, renewable and biodegradable polymers. By intelligent processing techniques they could be used as classical nano reinforcing fillers in polymers i.e., composites. They are often called whiskers. 

Fibers have been widely used in polymeric composites to improve mechanical properties. Cellulose is the major substance obtained from vegetable fibers, and applications for cellulose fiber-reinforced polymers have again come to the forefront with the focus on renewable raw materials. Hydrophilic cellulose fibers are very compatible with most natural polymers. The reinforcement of starch with ceUulose fibers is a perfect example of a polymer from renewable recourses (PFRR). The reinforcement of polymers using rigid fillers is another common method in the production and processing of polymeric composites. The interest in new nanoscale fillers has rapidly grown in the last two decades, since it was discovered that a nanostructure could be built from a polymer and layered nanoclay. This new nanocomposite showed dramatic improvement in mechanical properties with low filler content. Various starch-based nano-composites have been developed. 

In the course of the recent revival of bio-based polymers [58], cellulose esters have gained attention as matrix materials both for macroscopic and nano composites. In a series of papers, Seavey, Glasser, et al. have investigated continuous cellulose fibre reinforced cellulose ester composites of which the last is dealing with commercial matrix and fibre options [59]. A sort of hand lay-up with acetone solutions was used as the manufacturing method. For various commercial CABs and Lyocell fibres moduli between 15 GPa and 21 GPa were obtained in unidirectional (UD) composites while for cross-ply (CP) architectures, the values were between 10 and 15 GPa. Strengths go up to 310 MPa for UD composites and to 210 MPa for CP materials. 

S. J. Peters, Fracture toughness investigations of micro and nano cellulose fiber reinforced ultra high performance concrete Universityof Maine. (2009). 

The interest in the use of raw materials derived from renewable sources, combined with the good properties that have been observed for these materials, have led to the perspective that composites based on bio-resins and lignocellulosic and/or cellulosic fibers will experience an impressive development in a near future. Furthermore, the coming years should see an increased number of investigations on nano-reinforced thermoset composites, including phenolic composites. 

Pandey JK, Ahn SH, Lee CS, Mohanty AK, Misra M (2010) Recent advances in the application of natural fiber based composites. Macromol Mater Eng 295 975-989 Pandey JK, Chu WS, Kim CS, Lee CS, Ahn SH (2009) Bio-nano reinforcement of environmentally degradable polymer matrix by cellulose whiskers from grass. Compos B 40 676-680... 

Y. Li, A. J. Ragauskas. Cellulose nano whiskers as a reinforcing filler in polyurethanes,... 

Cellulose is the most abundant biopolymer on earth. It can be used in different applications, namely in the form of fibers, and cellulose can be converted into numerous cellulose derivatives. Cellulose micro- and nanofibers have been the subject of intense research in the field of composites. Cellulose derivatives can show liquid crystalline chiral nematic phases, which can be used for the production of diverse composite systems. All-cellulosic composites based on liquid crystalline cellulosic matrices reinforced by cellulose micro- and nanofibers can show enhanced mechanical properties due to fiber orientation induced by the liquid crystalline matrix. Cellulose-based fibers electrospun from liquid crystalline phases can develop different structures, which are able to mimic the shape of plant tendrils on the nano- and microscale, opening new horizons for ceDulosic membrane applications. 

Cellulose Nano/Microfibers-Reinforced Polymer Composites 259... 

For a fiber-reinforced composite, the final performance depends on fiber aspect ratio, surface area and its uniform dispersion in the polymer matrix. Ihe fact that the cel-lulosic nano/microcomposites show superior performance even at very low loading makes them a desirable candidate in composite industry. However, retaining the nanodimension and uniform dispersability in polar polymer matrix, especially in nonpolar matrix, is a huge challenge. Many methods have been adopted to overcome these issues. Extensive research in this field in the last few years has given a clear idea on the techniques to be adopted to attain stable nanofibers. Pretreatment of fibers, such as different physical and chemical techniques, are found to improve fiber-matrix interaction. These methods combined with proper processing techniques can result in the development of cellulose nano/microcomposites with excellent properties. 

NPs are used in the preparation of bio-nanocompositesmainly for two reasons, to create tortuous path in order to improve the barrier properties (as filler) and to induce various desired effects (as an additive) such as immobilization of enzymes, antimicrobial activity, biosensing, and so on. Varions types of NPs, including clay and silicates, Cellulose based nano-reinforcements, CNTs, Silica, Starch nanocrystals, chitin and chitosan NPs, and metal oxides, are presently nsed to enhance the biopolymer performance. 

Recently, the utility of inorganic nanoparticles as additives to enhance the polymer performance has been established. Various nano reinforcements currently being developed are nano-clay (layered silicates),cellulose nanowhiskers, ultra fine layered titanate, and carbon nanotubes. Carbon nanotubes, however, are the most promising of the new nanomaterials. Carbon nanotube-based polymer composites are poised to exhibit exceptional mechanical, thermal and electrical properties. ... 

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