Biocomposite

The in situ precipitation route towards obtaining composites of polymer and calcium phosphate is similar to the strategy employed in naturally occurring biocomposites and well may prove a viable method for the synthesis of bone substitutes. 

This chapter describes two important and diverse roles played by polysaccharides in development of biocomposites viz. as reinforcing agents in polymers matrix and second as matrix for synthesis of green metal nanocomposites... 

Hence polysaccharides have been viewed as a potential renewable source of nanosized reinforcement. Being naturally found in a semicrystalline state, aqueous acids can be employed to hydrolyze the amorphous sections of the polymer. As a result the crystalline sections of these polysaccharides are released, resulting in individual monocrystalline nanoparticles [13]. The concept of reinforced polymer materials with polysaccharide nanofillers has known rapid advances leading to development of a new class of materials called Bionanocomposites, which successfully integrates the two concepts of biocomposites and nanometer sized materials. The first part of the chapter deals with the synthesis of polysaccharide nanoparticles and their performance as reinforcing agents in bionanocomposites. 

Biocomposites of natural rubber with polysaccharide fillers... 

Polysaccharides such as starch and cellulose have been used as reinforcing agents in natural rubber. Both solution blending and dry mixing methods have been employed for the development of biocomposites and the performance compared with the composites obtained using carbon black. Dry mixing method is more economically viable and environment friendly. 

The results of mechanical properties (presented later in this section) showed that up to 20 phr, the biofillers showed superior strength and elongation behavior than CB, cellulose being the best. After 30 phr the mechanical properties of biocomposites deteriorated because of the poor compatibility of hydrophilic biopolymers with hydrophobic natural rubber(results not shown). While increasing quantity of CB in composites leads to constant increase in the mechanical properties. Scanning electron micrographs revealed presence of polymer-filler adhesion in case of biocomposites at 20 phr. 

Thermal stability is a crucial factor when polysaccharides are used as reinforcing agents because they suffer from inferior thermal properties compared to inorganic fillers. However, thermogravimetric analysis (TGA) of biocomposites suggested that the degradation temperatures of biocomposites are in close proximity with those of carbon black composites (Table-1). 

The results of the mechanical properties can be explained on the basis of morphology. The scanning electron micrographs (SEM) of fractured samples of biocomposites at 40 phr loading are shown in figure. 3. It can be seen that all the bionanofillers are well dispersed into polymer matrix without much agglomeration. This is due to the better compatibility between the modified polysaccharides nanoparticles and the NR matrix (Fig. 4A and B). While in case of unmodified polysaccharides nanoparticles the reduction in size compensates for the hydrophilic nature (Fig. 3C and D). In case of CB composites (Fig. 3E) relatively coarse, two-phase morphology is seen. 

Centre for Biocomposites and Biomaterials Processing University of Toronto Toronto, Ontario, Canada... 

The BioComposites Centre, School of Agricultural Forest Sdences University of Wales Bangor, Gwynedd LL57 2UW, United Kingdom... 

We acknowledge the financial support for the research from LINK Collaborative Programme in Crops for Industrial Use and Dr. James Bolton, Director of The BioComposites Centre. 

Although the catalysts do not interfere with each other, the immobilization process resulted in higher yields and ees than with the raw enzyme the initial activity was over five times greater. Additionally, the biocomposite with enzyme was able to be recycled and maintained its activity, which demonstrates the utility of such an immobilization system for potential cascades with mutually interfering catalysts. 

Pope, E.J.A. (1995) Gel encapsulated microorgansims saccharomyces cerevisiae-silica gel biocomposites. Journal of Sol-Gel Science and Technology, 4, 225-229. 

Gill, I. and Ballesteros A. (2000) Bioencapsulation within synthetic polymers (Part 2) non sol-gel protein-polymer biocomposites. Trends in Biotechnology, 18, 469-479. 

FIGURE 5.6 Schematic representation of the immunosensor based on a Protein A-GEB biocomposite as a transducer, (a) Immobilization of RlgG on the surface via interaction with Protein A, (b) competitive immunoassay using anti-RIgG and biotinylated anti-RIgG, (c) enzyme labeling using HRP-streptavidin and (d) electrochemical enzyme activity determination. (Reprinted from [31] with permission from Elsevier.)... 

E. Zacco, M.I. Pividori, and S. Alegret, Electrochemical biosensing based on universal affinity biocomposite platforms. Biosens. Bioelectron. 21, 1291-1301 (2006). 

Patel, M. and Narayan, R. (2005). How sustainable are biopolymers and biobased products The hope and the reality. In Natural Fibres, Biopolymers and Their Biocomposites, ed. Mohanty, A. K., Misra, M. and Drzal, L. T. Boca Raton (USA) CRC Press, pp. 833-853. 

BP Chemicals developed a pilot-scale plant for the acetylation of wood fibres in collaboration with A-Cell acetyl cellulosics AB, Depac Engineering and the BioComposites... 

Averous, L. and Halley, P.J., Biocomposites Based on Plasticized Starch, Biofuels, Bioprod. Biorefin., 3, 329 (2009)... 

Flatakeyama, T. and Flatakeyama, FI. 2005. Thermal Properties of Green Polymers and Biocomposites. Springer, New York. 

E. Verne, M. Ferraris, C. Jana, L. Paracchini, Bioverit base glass/Ti particulate biocomposite in situ vacuum plasma spray deposition, J. Eur. Ceram. Soc. 20 (2000) 473-479. 

Llopis et al. [37] Cola beverage Glucose oxidase (GOD)/ entrapped together with the mediator in the bulk of the biocomposite material Graphite and nonconducting epoxy resin composite electrode/ +0.3 V vs. Ag/AgCl Tetrathiafulvalene-tetracyanoquino-dimethane (TTF - TCNQ)... 

X. Llopis, A. Merkogi, M. del Valle and S. Alegret, Integration of a glucose biosensor based on an epoxy-graphite-TTF TCNQ-GOD biocomposite into a FIA system, Sens. Actuators B Chem., 107(2) (2005) 742-748. 

Q. Yao, S. Yabuki and F. Mizutani, Preparation of a carbon paste/alcohol dehydrogenase electrode using polyethylene glycol-modified enzyme and oil-soluble mediator, Sens. Actuators B Chem., 65(1-3) (2000) 147-149. A. Morales, F. Cespedes, E. Martinez-Fabregas and S. Alegret, Ethanol amperometric biosensor based on an alcohol oxidase-graphite-polymer biocomposite, Electrochim. Acta, 43(23) (1998) 3575-3579. 

As a second example, a biosensor for urea could be constructed using an ammonia gas-sensing electrode [10] or a biocomposite containing soybean powder, polymer matrix and manganese dioxide as pH-sensing electrode [5]. 

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