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Polylactic Acid: Synthesis, Properties and Applications
L. Avérous

ABSTRACT Polylactic acid (PLA) is at present one of the most promising biodegradable polymers (biopolymers) and has been the subject of abundant literature over the last decade. PLA can be processed with a large number of techniques and is commercially available (large-scale production) in a wide range of grades. It isrelatively cheap and has some remarkable properties, which make it suitable for different applications. This chapter deals with the different syntheses to produce this biopolymer, its diverse properties and various applications. Its biodegradability is adapted to short-term packaging, and its biocompatibility in contact with living tissues is exploited for biomedical applications (implants,sutures, drug encapsulation …). Keywords Polylactic acid, Biopolymer, Biodegradable, Properties, Synthesis, Process, Application, Packaging, Biomedical 21.1 INTRODUCTION

Tailoring new materials within a perspective of eco-design or sustainable development is a philosophy that is applied to more and more materials. It is the reason why material components such as biodegradable polymers can beconsidered as ‘interesting’ – environmentally safe – alternatives. Besides, ecological concerns have resulted in a resumed interest in renewable resources-based products. Figure 21.1 shows an attempt to classify the biodegradable polymers into two groups and four different families. The main groups are (i) the agro-polymers (polysaccharides, proteins, etc.) and (ii) the biopolyesters (biodegradablepolyesters) such as polylactic acid (PLA), polyhydroxyalkanoate (PHA), aromatic and aliphatic copolyesters [1]. Biodegradable polymers show a large range of properties and can now compete with non-biodegradable thermoplastics in different fields (packaging, textile, biomedical, etc.). Among these biopolyesters, PLA is at present one of the most promising biopolymer. PLA has been the subject of an abundantliterature with several reviews and book chapters [2–8], mainly during the last decade. PLA can be processed with a large number of techniques. PLA is commercially and largely available (large-scale production) in a wide range of grades. It has a reasonable price and some remarkable properties to fulfil different applications. For instance, the PLA production capacity of Cargill (USA) in 2006 was140 kT per year at 2–5 Euros per kg [9]. Other companies, such as Mitsui Chemical (LaceaJapan), Treofan (Netherland), Galactic (Belgium), Shimadzu Corporation (Japan), produce smaller quantities. Some of them are only focused on the biomedical market like Boeringher Ingelheim (Germany), Purac (Netherland) or Phusis (France), because the constraints of this market are very specific. However,according to different sources, PLA consumption in 2006 was only about 60 000 tons per year and, at present, only 30 per cent of lactic acid is used for PLA production. Thus, this biopolymer presents a high potential for development.
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Polylactic Acid: Synthesis, Properties and Applications, L. Avérous
Biodegradable polymers From biotechnology(conventional synthesis from bio-derived monomers) From petrochemical products (conventional synthesis from synthetic monomers) Polycaprolactones (PCL) Polyesteramides

Biomass products From agro-resources → Agro-polymers

From micro-organisms (obtained by extraction)

Polysaccharides

Proteins, Lipids

PolyHydroxy-Alkanoates (PHA)

Polylactides

Starches: Wheat Potatoes Maize, ...Ligno-cellulosic products: Wood Straws, ... Others: Pectins Chitosan/Chitin Gums, ...

Animals: Casein Whey Colagen/Gelatin Plant: Zein Soya Gluten

Poly(hydroxybutyrate) (PHB) Poly(hydroxybutyrate co-hydroxyvalerate) (PHBV), …

Polylactic acid (PLA)

Aliphatic co-polyesters

Aromatic co-polyesters

Agro-polymers

Biopolyesters

Figure 21.1

Classification of the biodegradable...