Natural biodegradable polymers classification

There are several types of biodegradable polymers. A common classification is based on the distinction between natural and synthetic biodegradable polymers. Natural biodegradable polymers are typically produced directly by living organisms, and they are extracted from them a posteriori. The most common biodegradable natural polymers are collagen, elastin, fibrin, and several polysaccharide derivatives, such as... 

Biodegradable polymers and plastics are readily divided into three broad classifications (/) natural, (2) synthetic, and (J) modified natural. These classes may be further subdivided for ease of discussion, as follows (/) natural polymers (2) synthetic polymers may have carbon chain backbones or heteroatom chain backbones and (J) modified natural may be blends and grafts or involve chemical modifications, oxidation, esterification, etc. 

The most fundamental classification of polymers is whether they are naturally occurring or synthetic. Common natural polymers (often referred to as biopolymers) include macromolecules such as polysaccharides e.g., starches, sugars, cellulose, gums, etc.), proteins e.g., enzymes), fibers e.g., wool, silk, cotton), polyisoprenes e.g., natural rubber), and nucleic acids e.g., RNA, DNA). The synthesis of biodegradable polymers from natural biopolymer sources is an area of increasing interest, due to dwindling world petroleum supplies and disposal concerns. 

It is difficult to make a distinct classification of biodegradable polymers. Many authors have classified them according to their origin as natural or synthetic polymers. Both of these are subdivided into different classes based on the main linkages present in their structure. Thus completely biodegradable natural polymer subclasses include polysaccharides, polypeptides, polyesters, lipids, natural rubber and natural composites (wood). Partially biodegradable synthetic polymer subclasses include polyesters, polyur eas, polyurethanes, polyamides, poly( vinyl alcohol) and poly (ethylene glycol). 

Proteins are natural, renewable, and biodegradable polymers which have attracted considerable attention in recent years in terms of advances in genetic engineering, eco-friendly materials, and novel composite materials based on renewable sources. This chapter reviews the protein structures, their physicochemical properties, their modification and their application, with particular emphasis on soy protein, zein, wheat protein, and casein. Firstly, it presents an overview of the structure, classification, hydration-dehydration, solubility, denaturation, and new concepts on proteins. Secondly, it concentrates on the physical and chemical properties of the four important kinds of proteins. Thirdly, the potential applications of proteins, including films and sheets, adhesives, plastics, blends, and composites, etc. are discussed. 

For ease of discussion, this section is divided into three broad classifications — natural, synthetic, and modified natural based biodegradable polymers and plastics. Natural polymers indicate no modification of isolated polymer, synthetic poisoners include carbon chain and heteroatom chain polymers, and modified natural polymers encompass grafts and blends, and chemical modifications such as oxidations and esterifications. 

Like polymers, biodegradable polymers have been classified using distinct methods, including methods based on polymer origin (synthesis), renewability content, and biodegradability level. The most prominent and well-established method is the classification based on synthetic procedmes. In broad terms, these polymers are classified into two main categories (i) agropolymers (obtained from biomass) and (ii) biopolyesters (natural or synthetic biopolymers). Biopolyesters is itself a broad term that includes three subclasses (a) microbially produced polymers (b) polymers synthesized... 

Currently, some biodegradable polyesters are synthesized and/or formed in nature by organism growth. Different classifications of these biodegradable polymers have already been proposed in the literature (Averous, 2004 Bordes, 2009) depending on the synthesis process. For ovn purposes, the main families of polyesters are extracted and highlighted in Figure 1. 

Biodegradable natural polymers classification is represented in Fig. 2.1 and chemical structures of natural polymers represented in Fig. 2.2. 

Classification of biodegradable polymers 21 Table 1.2 Properties of natural fibres (Drzal et al., 2003)... 

Chapters 10 to 29 consisted of reviews of plastics materials available according to a chemical classification, whilst Chapter 30 rather more loosely looked at plastics derived from natural sources. It will have been obvious to the reader that for a given application plastics materials from quite different chemical classes may be in competition and attempts have been made to show this in the text. There have, however, been developments in three, quite unrelated, areas where the author has considered it more useful to review the different polymers together, namely thermoplastic elastomers, biodegradable plastics and electrically conductive polymers. 

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