Making a Biodegradable Plastic Using Starch

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  • Topic: Polymer, Starch, Polymer chemistry
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eXPRESS Polymer Letters Vol.3, No.6 (2009) 366–375

Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2009.46

Starch-based completely biodegradable polymer materials
D. R. Lu, C. M. Xiao*, S. J. Xu
College of Material Science and Engineering of Huaqiao University, Quanzhou, 362021, P. R. China Received 21 February 2009; accepted in revised form 30 March 2009

Abstract. Starch is a natural polymer which possesses many unique properties and some shortcoming simultaneously. Some synthetic polymers are biodegradable and can be tailor-made easily. Therefore, by combining the individual advantages of starch and synthetic polymers, starch-based completely biodegradable polymers (SCBP) are potential for applications in biomedical and environmental fields. Therefore it received great attention and was extensively investigated. In this paper, the structure and characteristics of starch and some synthetic degradable polymers are briefly introduced. Then, the recent progress about the preparation of SCBP via physical blending and chemical modification is reviewed and discussed. At last, some examples have been presented to elucidate that SCBP are promising materials for various applications and their development is a good solution for reducing the consumption of petroleum resources and environmental problem. Keyword: biodegradable polymers, starch, biopolymer, preparation, application

1. Introduction
As well known, synthetic polymer materials have been widely used in every field of human activity [1] during last decades, i.e. post-Staudinger times. These artificial macromolecular substances are usually originating from petroleum and most of the conventional ones are regarded as non-degradable. However, the petroleum resources are limited and the blooming use of non-biodegradable polymers has caused serious environmental problems. In addition, the non-biodegradable polymers are not suitable for temporary use such as sutures. Thus, the polymer materials which are degradable and/or biodegradable have being paid more and more attention since 1970s. Both synthetic polymers and natural polymers that contain hydrolytically or enzymatically labile bonds or groups are degradable. The advantages of synthetic polymers are obvious, including predictable properties, batch-to-batch uniformity and

can be tailored easily [2]. In spite of this, they are quite expensive. This reminds us to focus on natural polymers, which are inherently biodegradable [3] and can be promising candidates to meet different requirements. Among the natural polymers, starch is of interest. It is regenerated from carbon dioxide and water by photosynthesis in plants [4]. Owing to its complete biodegradability [5], low cost and renewability [6], starch is considered as a promising candidate for developing sustainable materials. In view of this, starch has been receiving growing attention since 1970s [7, 8]. Many efforts have been exerted to develop starch-based polymers for conserving the petrochemical resources, reducing environmental impact and searching more applications [9–11]. In this paper, the status of preparation and applications of starch-based completely biodegradable (SCBP) polymers is reviewed and presented.

*Corresponding author, e-mail: congmingxiao hqu.edu.cn @ © BME-PT

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Lu et al. – eXPRESS Polymer Letters Vol.3, No.6 (2009) 366–375

2. Structure and properties of starch
Starch is mainly composed of two homopolymers of D-glucose [8]: amylase, a mostly linear αD(1, 4’)-glucan and branched amylopectin, having the same backbone structure as amylose but with many α-1, 6’-linked branch points (Figure 1). There are a lot of hydroxyl groups on starch chains, two secondary hydroxyl groups at C-2 and C-3 of each glucose residue, as well as one primary hydroxyl group at C-6 when it is not linked. Evidently, starch is hydrophilic. The available hydroxyl groups on the starch chains potentially exhibit reactivity...
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