Natural Polymeric Material

Our body is shaped mainly by proteins. Silk is a protein produced by silk worm, and our hair is made of some proteins, one of which is keratin. A protein is a special kind of polymer. It is a linear polymer of 20 or so monomers called amino acids. 

We hope we have shown you that many organic building and clothing material are polymers. There are a number of organic compounds that are not polymers but are solids at ordinary temperature and insoluble in water. The compounds of this type, however, are not used for extra skeleton, shell, or clothing. Why would they not be used for such purposes Polymeric material can easily be made into libers or films because of their chemical structures, but nonpolymeric material cannot be made into these forms. 

Important natural polymers (biopolymers) include cellulose, chitin, proteins, and nucleic acids. Nucleic acids, DNA and RNA, are discussed in Chap. 4 and are not used as mechanical supports for organisms/cells/tissues. All of these materials can in principle be produced by connecting small molecules (the repeating unit called monomer) through condensation reactions. A reaction to connect a large number of monomers is called polymerization. In the case of these biopolymers, the reaction should further be characterized as condensation polymerization to contrast with another type of polymerization described later. It can generally be written as follows  

It is not a simple matter to accomplish this kind of reaction in the biological system. All of these materials require elaborate reaction systems to make. We would not talk about the processes of making them in the biological systems, and we will only look at their structures and some properties. 

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STARCH. Starches are used as components and/or processing aids in the production of resources such as aluminum, paper, copper, water, and oil. The use of this natural polymeric material is based on its... 

Generally, a distinction can be made between membrane bioreactors based on cells performing a desired conversion and processes based on enzymes. In ceU-based processes, bacteria, plant and mammalian cells are used for the production of (fine) chemicals, pharmaceuticals and food additives or for the treatment of waste streams. Enzyme-based membrane bioreactors are typically used for the degradation of natural polymeric materials Hke starch, cellulose or proteins or for the resolution of optically active components in the pharmaceutical, agrochemical, food and chemical industry [50, 51]. In general, only ultrafiltration (UF) or microfiltration (MF)-based processes have been reported and little is known on the application of reverse osmosis (RO) or nanofiltration (NF) in membrane bioreactors. Additionally, membrane contactor systems have been developed, based on micro-porous polyolefin or teflon membranes [52-55]. 

Macromolecular chemistry covers a particularly wide field which includes natural polymeric material, such as proteins, cellulose, gums and natural rubber industrial derivatives of natural polymers, such as sodium carboxymethyl cellulose, rayon and vulcanised rubber and the purely synthetic polymers, such as polythene (polyethylene), Teflon (polytetrafluoroethylene), polystyrene, Perspex (poly (methyl... 

Molecular separation along with simultaneous chemical transformation has been made possible with membrane reactors [17]. The selective removal of reaction products increases conversion of product-inhibited or thermodynamically unfavourable reactions for example, in the production of ethanol from com [31]. Enzyme-based membrane reactors were first conceived 25 years ago by UF pioneer Alan Michaels [49]. Membrane biocatalytic reactors are used for hydrolytic conversion of natural polymeric materials such as starch, cellulose, proteins and for the resolution of optically active components in the pharmaceutical, agrochemical, food and chemical industries. Membrane bioreactors for water treatment were introduced earher in this chapter and are discussed in detail in Chapters 2 and 3. 

There are various ways to classify polymers. A simple way is to distinguish polymers with respect to their origin in synthetic and natural polymers. Natural polymeric materials such as shellac, cellulose, and natural rubber have been used for centuries. Natural polymers are a class of polymers derived from renewable biomass sources, such as plants, vegetable oil, com starch, pea starch. Generally, natural polymers (or biopolymers) are used after modification reactions. Some biopolymers are designed to biodegrade. Table 2.1.1 and Fig. 2.1.1 give examples of natural polymers and modified natural polymers. 

Analytical pyrolysis has been described in books ([512,539], cfr. also Bibliography), in many reviews [430,510,517,540-545], in bibliographies [530], and sustains a dedicated journal [546]. A special issue on analytical pyrolysis of synthetic and natural polymeric materials has just appeared [547]. Wampler [514] and Moldoveanu [499] have recently reviewed pyrolysis instrumentation and analysis. Several authors [530,540,548-561] reviewed analytical pyrolysis in polymer studies. The determination of inpolymer additives by flash pyrolysis techniques was reviewed [562,563]. Blazs6 [564] has recently reviewed development in analytical and applied pyrolysis. Yearly some 400 pyrolysis-related papers appear. 

R.P. Lattimer (ed.). Special Issue on Analytical Pyrolysis of Synthetic and Natural Polymeric Materials, J. Anal. Appl. Pyrol. 64 (2) (2002). 

Due to their chemical nature, polymeric materials have the tendency to dissolve molecules of gases, vapors, and other low-molecular-weight substances to a higher degree than inorganic glasses. Dissolved penetrant molecules diffuse through the polymer via an acti-... 

Bioactive polymeric materials have existed from the creation of life itself. Many firmly believe that life could not even exist unless polymeric materials are used to form the basic building blocks. Although this assumption can not be rigorously proven, it is a fact that most, if not all, of the major biochemical pathways involve polymeric species, such as the proteins (including enzymes), polysaccharides and nucleic acids. Among the many reasons for this fact, must be the observation that the natural polymeric materials can be made into an enormous variety of different, but inter-related, species. It is now well established that a DNA chain, which only contains four different primary repeating units, can encode an enormous wealth of data permitting not only the replication processes, but protein synthesis and the entire life scheme as well. 

It is not surprising, therefore, that many of the applications of bioactive polymeric systems involve interactions with the natural polymeric materials. Likewise, the use of many natural polymers as the base materials for these bioactive systems can hardly be considered a surprise. They are not only readily available, they are also normally more biocompatible and/or biodegradable than the usual synthetic polymer. This book contains several chapters in which natural polymers are the main theme, but there are far more chapters which involve synthetic polymeric materials. There is probably a place for either type of material in the vast realms of biological and/or biomedical applications. 

Plastics are made up of polymers and other materials that are added to them to give the desired characteristics. Natural polymeric materials such as mbber, shellac and gutta percha have a long history as raw materials for man. The first thermoplastic, celluloid, was also manufactured from a natural product, from cellulose. Even today, there are still some cellulose based plastics, i.e., the cellulose acetates (CA). Cellulose is already composed of the large molecules that are characteristic of plastics (macromolecules). However, to manufacture CA plastics, they still have to be prepared with acetic acid. The first injection moulding machine was built and patented in 1872 in order to mould cellulose materials. 

In this context it is worthwhile to study and explain the properties of natural polymeric materials, because - as usual - natural evolution has often led to excellent solutions. To this end, it is again indispensable to understand the relationship between structure, on the one hand, and physical and chemical properties, on the other hand. 

REMOVAL AND RECOVERY OF HEAVY METALS USING NATURAL POLYMERIC MATERIALS... 

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