Renewable materials chitin

In the area of renewable materials, bulk oxypropylation of chitin and chitosan has been performed. Chitin and chitosan are abundant natural polymers obtained from shellfish, such as crab shell or shrimp shell. This solvent free reaction yields viscous polyols. Unfortunately, propylene oxide homopolymer is formed as a by-product but is easily separated. It should be noted that care was taken to minimize the risk involved in the use of toxic, flammable propylene oxide (the reagent in this process). 

It is worth pointing out that, besides o-sorbitol 19 and D-mannitol 36, other low-molecular weight building blocks have been already obtained on the ton-scale from low cost or waste polymeric carbohydrates (starch, cellulose, hemicellulose, chitin) [80, 81]. Most of these compounds are densely functionalized enantiopure molecules that can be easily converted into high-value added products, including chiral ionic liquids. Therefore, further studies are required to develop other synthetic approaches to environmentally sustainable ionic liquids based on renewable raw materials. 

The book distills recent research conducted by the scientific community. It is arranged in four parts. Part I, Polysaccharides, covers hyaluronic acid, chitin and chitosan, starch and other natural polysaccharides. Polysaccharides have received more attention due to their numerous advantages such as their renew-ability, non-toxicity, biodegradability and ready availability. This interest has resulted in a great revolution leading to polysaccharides becoming on par with, and even superior to, synthetic materials. That is why a plethora of research studies have been undertaken to understand the potential of these natural polymers. 

The book is organized in several chapters and deals with the most important biopolymer classes like the different polysaccharides (starch, cellulose, chitin), lignin, proteins and (polyhydroxy alkanoates) as raw materials for bio-based plastics, as well as with materials derived from bio-based monomers like lipids, poly(lactic acid), polyesters, polyamides and polyolefines. Additional chapters on general topics - the market and availability of renewable raw materials, the importance of bio-based content and the aspect of biodegradability - provide important information related to all bio-based polymer classes. 

This chapter gives a general introduction to the book and describes briefly the context for which the editors established its contents and explains why certain topics were excluded from it. It covers the main raw materials based on vegetable resources, namely (i) wood and its main components cellulose, lignin, hemicelluloses, tannins, rosins and terpenes, as well as species-speciflc constituents, like natural rubber and suberin and (ii) annual plants as sources of starch, vegetable oils, hemicelluloses, mono and disaccharides and algae. Then, the main animal biomass constituents are briefly described, with particular emphasis on chitin, chitosan, proteins and cellulose whiskers from molluscs. Finally, bacterial polymers such as poly(hydroxyalkanoates) and bacterial cellulose are evoked. For each relevant renewable source, this survey alerts the reader to the corresponding chapter in the book. 

Environmental requirements are assuming great importance, since there is an increased interest in the industrial use of renewable resources such as starch and chitin. Considerable efforts are now being made in the research and development of polysaccharide derivatives as the basic materials for new applications. In particular, the increasing cost of conventional adsorbents undoubtedly makes chitin and chitosan-based materials one of the most attractive biosorbent for wastewater treatment. Chitin and chitosan biopolymers have demonstrated outstanding removal capabilities for certain pollutants such as dyes and metal ions as compared to other low-cost sorbents and commercial-activated carbons. Biopolymer adsorbents are efficient and can be used for the decontamination of effluents (removal of pollutants) and for separation processes (recovery of valuable metals). 

Hudson, S.M. and Smith, C. 1998. Polysaccharide Chitin and chitosan Chemistry and technology of then-use as structural materials. In Kaplan, D.L. (ed.). Biopolymers from Renewable Resources. Springer -Verlag, New York, pp. 96-118. 

Gandini A, Belgacem MN (2008) Furan derivatives and furan chemistry at the service of macromolecular materials. In Belgacem MN, Gandini A (eds) Monomers, polymers and composites from renewable resources. Elsevier, Amsterdam Goodrich JD, Winter WT (2007) a-Chitin nanocrystals prepared from shrimp shells and their... 

Hudson SM, Smith C (1998) Polysaccharide chitin and chitosan chemistry and technology of their use as structural materials. In Kaplan DL (ed) Biopol)oners from renewable resources. Springer, New York, pp 96-118... 

Recently, the composite materials made of organic and inorganic phases have attracted much attention polymer-based composite materials have been widely used in the biomedical field [173], and natural polymers, such as cellulose, chitin, corn protein, starch and soy protein isolate (SPI) [174] have become important due to the increasing requirements for materials with characteristics of renewability, biocompatibility, biodegradability, and non-toxicity. 

The interest on natural-based materials for reinforcement of polymer matrices has been increased in recent years. In this section, we focus the attention on the reinforcement effect of cellulose, starch or chitin fillers on the thermal properties of PU-based materials. These nanofillers can be obtained from natural and renewable sources and can be processed in several ways presenting different morphologies, such as nanowhiskers, nanofibers, or nanoparticles. In particular, cellulose can be processed by hydrolysis reaction of different cellulose sources in order to obtain cellulose nanocrystals (CNC) [72]. In Figure 7.3, the CNC structure is shown. The CNC present a diameter of about 19 nm. [72]. 

Nature offers a complete renewable and sustainable source of a wide range of raw materials of different sttucture, polarity and size. Cellulose, chitin, starch, fruits, lignin, waste proteins, fats and oils are important bio-based raw materials for sugars, peptides. 

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