Biodegradable Polymer Classifications

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 report starts with an overview of biodegradable polymers including an examination of the processes of biodegradation, classification of biodegradable polymers including their chemical structure, properties, and processing performance. 

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. 

Depending on the synthesis process, different groups or types of biodegradable polymers have been classified. Figure 9.3 shows a proposal for a classification [AVE 04a] including four different categories. Only the first three categories (a-c) are obtained from renewable resources ... 

Biodegradable Polymers Definition, Classification and Application as an Alternative to Plastic... 

Figure 5.2 Classification of biodegradable polymers, also on the basis of their origin (Av rous and Pollet, 2012).

Biodegradable polymers can be classified according to their chemical composition, resource, synthesis and application methods, etc. Figure 6.2 demonstrates classification of the main biodegradable polymers according to their resource. On the other hand. Fig. 6.3 shows the chemical structure of some of the most Important biodegradable polymers. 

Figure 6.2 Classification of biodegradable polymers based on their origin. Adapted from [10,18,37,132].

Even this listing style assists in rousing confusion towards the classification of biopolymers. Biodegradable polymers, even those 100% based on the traditional petrochemical production route are including in this listing. In some cases, polymers with a petrochemical feedstock, but a biotechnological intermediary step (such as fermentation or enzymatic catalysis) are... 

Key words biodegradable polymer, biodegradation, classification of biodegradable polymers, mechanism of biodegradation, testing method, application. 

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). 

Figure 21.1 Classification of the biodegradable polymers. (Adapted from Reference [1].)...

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. 

Fig. 17.1 Classification of the main biodegradable polymers. Reproduced with pmnission (Hordes et al. 2009). Copyright of Elsevier...

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. 

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... 

Table. 8.2 Classification of Biodegradable polymer following the Heller terms.

This chapter describes the historical development of polymers and the basis of their classification. Based on their origin and mode of synthesis, biodegradable polymers are categorized into various classes. The structure, chemistry, biocompatibility, and biodegradability of these biodegradable polymers are discussed and, at the end of the chapter, their applications in pharmaceutical and medical fields are summarized. The discussed content will provide readers with an insight into the basic concept of biodegradable polymers and their role in everyday life. 

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... 

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