PREFACE

The technological breakthrough at Cargill, Inc. in the early 1990s to produce high-molecular-weight PLA via commercially viable lactide ring-opening polymerization can be considered as the key milestone that paved the way to transform PLA from a specialty material to a commodity thermoplastic (Table P.1). Today, PLA has emerged as one of the mainstream biodegradable polymers that find many applications ranging from biomedical to single-use food packages.

Like the first edition, this volume is organized into five parts. In Part I, Chapters 1 and 2 cover various aspects of lactic acid/lactide monomers, including their physicochemical properties and production. Chapter 3 looks at different condensation reactions for the polymerization of PLA. To enhance the properties of PLA, modification involving copolymerization with lactic acid/lactide of different isomers is one of the strategies available today. These topics are presented in Chapter 4. This sets the stage for the discussions in Chapter 5 on fundamentals and technologies related to stereocomplex PLA produced by co-crystallization of PLLA/PDLA stereoisomers; topics discussed include stereoblock formation, copolymerization, and composite formation. Structures and phase transition behaviors of various crystals for PLA and PLLA/PDLA stereoisomer are reviewed in Chapter 6, along with comparison to related biodegradable polyesters.

Part II is dedicated to the techniques for material characterization for PLA. This part starts with Chapter 7 that focuses on spectroscopy techniques for PLA analysis, including UV-Vis, Fourier transform infrared, Raman, nuclear magnetic resonance spectroscopies. Chapters 8, 9, and 10 discuss the thermal, rheological, and mechanical properties of PLA, respectively, as affected by factors such as temperature, aging, annealing, molecular stereoregularity, copolymerization, and additive incorporation. Mass transport phenomena of gases and nonvolatile compounds in PLA have important implications on their end-use performance, especially in packaging applications. Chapters 11 and 12 discuss these topics in great depth.

Part III is made up of six chapters that are devoted to processing and conversion technologies for PLA. Chapter 13 summarizes the main conversion methodologies for PLA based on melt and solution processing (e.g., extrusion, injection molding, blow molding, thermoforming, fiber spinning). Other conversion techniques are presented in the subsequent chapters, including blending (Chapter 14), foaming (Chapter 15), composites and nanocomposites processing (Chapters 16 and 17). Chapter 18 looks at melt spinning process in greater depth, explicitly dealing with the mechanisms of fiber structure development.

Part IV covers the degradation and environmental issues of PLA. Bio- and physicochemical degradation phenomena of PLA are discussed in great length by various authors. Chapter 19 presents the mechanisms of photodegradation and radiolysis of PLA. Thermal degradation phenomena are highly relevant during the processing of PLA; Chapter 20 focuses on this topic wherein the authors address the apparent complexities of degradation kinetics through a multi-step complex reaction analysis method. Chapter 21 discusses the mechanisms of hydrolytic degradation, taking polymer (e.g., molecular structure/weight, highly ordered structures, blends) and medium (e.g., temperature, pH) factors into considerations. Complementarily, Chapter 22 reviews the literature on enzymatic degradation, focusing on PLA derived from melt-crystallized, solvent-cast, and blend films. Recent advances in enzymes that degrade PLAs and their copolymers are also presented. The next two chapters deal with environmental issues, including topics such as life cycle assessment (Chapter 23) and end-of-life scenarios (Chapter 24). Finally, in Part V, various applications for PLA are discussed, including medical items (Chapter 25), packaging and consumer goods (Chapter 26), textiles (Chapter 27), and environmental applications (Chapter 28).

TABLE P.1 Significant Events Related to PLA Production that Occurred Over the Past Few Decades

a ?Jung et al. [1].

More than 10?years have passed since the first edition of this volume was published in 2010. During this period, there have been considerable scientific advancements and technological developments of PLA. PLA continues to captivate the interests of technologists and researchers, as reflected by the sustained increase in the number of publications related to PLA (Figure P.1). The main goal for the second edition is to update the volume with new progress made on various topics of PLA. We made a minor change in the book title, adding "End of Life" to it given the expanded discussions related to this area.

FIGURE P.1 Number of publications since 1984 based on Web of Science search (accessed on 24 September 2021) using the keywords ("polylactide," "poly(lactic acid),", and "polylactic acid."

For completeness and better flow, we deliberately allowed some overlap between chapters so that they are relatively stand-alone. Chapter 1 is a reprint from the first edition. Chapter 9 is a reprint from Chapter 10 of the first edition. Since the theoretical framework of rheology for PLA remains valid, we have decided to include this chapter in the present edition. In addition, a part of Chapter 20, "Spinning of poly(lactic acid) fibers," from the first edition is now incorporated in Chapter 13 of the present edition.

We are grateful to all authors who contributed their manuscripts and thankful to them for entrusting us to edit their contributions to meet the needs of this volume. It would not have been possible to complete this project without their participation and patience during the preparation of this book. We hope that readers will find this updated edition of the book useful. We are looking forward to receiving comments and feedback regarding the content of this book.

September 2021
Rafael A. Auras
Loong-Tak Lim
Susan E. M. Selke
Hideto Tsuji

REFERENCE

1. 1. Y.K. Jung, T.Y. Kim, S.J. Park, S.Y. Lee, Biotechnol. Bioeng. 2010,...