Poly(lactic acid) Science and Technology Processing, Properties, Additives and Applications RSC Polymer Chemistry Series Editor-in-Chief: Ben Zhong Tang, The Hong Kong University of Science and Technology, Hong Kong, China Series Editors: Alaa S. Abd-El-Aziz, University of Prince Edward Island, Canada Stephen Craig, Duke University, USA Jianhua Dong, National Natural Science Foundation of China, China Toshio Masuda, Fukui University of Technology, Japan Christoph Weder, University of Fribourg, Switzerland Titles in the Series: 1: Renewable Resources for Functional Polymers and Biomaterials 2: Molecular Design and Applications of Photofunctional Polymers and Materials 3: Functional Polymers for Nanomedicine 4: Fundamentals of Controlled/Living Radical Polymerization 5: Healable Polymer Systems 6: Thiol-X Chemistries in Polymer and Materials Science 7: Natural Rubber Materials: Volume 1: Blends and IPNs 8: Natural Rubber Materials: Volume 2: Composites and Nanocomposites 9: Conjugated Polymers: A Practical Guide to Synthesis 10: Polymeric Materials with Antimicrobial Activity: From Synthesis to Applications 11: Phosphorus-Based Polymers: From Synthesis to Applications 12: Poly(lactic acid) Science and Technology: Processing, Properties, Additives and Applications How to obtain future titles on publication: A standing order plan is available for this series. A standing order will bring delivery of each new volume immediately on publication. For further information please contact: Book Sales Department, Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge, CB4 0WF, UK Telephone: +44 (0)1223 420066, Fax: +44 (0)1223 420247 Email: [email protected] Visit our website at www.rsc.org/books Poly(lactic acid) Science and Technology Processing, Properties, Additives and Applications Edited by Alfonso Jime´nez University of Alicante, Alicante, Spain Email: [email protected] Mercedes Peltzer University of Alicante, Alicante, Spain Email: [email protected] Roxana Ruseckaite National University of Mar del Plata, Argentina Email: [email protected] RSC Polymer Chemistry Series No. 12 Print ISBN: 978-1-84973-879-8 PDF eISBN: 978-1-78262-480-6 ISSN: 2044-0790 A catalogue record for this book is available from the British Library r The Royal Society of Chemistry 2015 All rights reserved Apart from fair dealing for the purposes of research for non-commercial purposes or for private study, criticism or review, as permitted under the Copyright, Designs and Patents Act 1988 and the Copyright and Related Rights Regulations 2003, this publication may not be reproduced, stored or transmitted, in any form or by any means, without the prior permission in writing of The Royal Society of Chemistry, or in the case of reproduction in accordance with the terms of licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of the licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to The Royal Society of Chemistry at the address printed on this page. The RSC is not responsible for individual opinions expressed in this work. Published by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 0WF, UK Registered Charity Number 207890 For further information see our web site at www.rsc.org Preface Introduction Issues related to sustainability, petroleum shortage and fluctuating oil prices together with the enormous increase in the use of polymers in areas of great demand, such as packaging, have intensified the development of new cost- effective, greener alternatives. The challenge is to adopt some fairly new design criteria to produce materials with the necessary functionalities during use, but which undergo degradation under the stimulus of an en- vironmental trigger after use. Bio-based and biodegradable polymers have emerged as renewable alternatives to depleting ones and have the distinctive ability of being entirely converted into biomass and harmless by-products through microbial activity in appropriate waste management infrastructure.1 For these reasons there is great interest in the so-called green polymer materials to offer an answer to sustainable development of economically and ecologically attractive technologies, contributing to the preservation of fossil-based raw materials, reducing the volume of garbage through com- postability in the natural cycle leading to climate protection and reduction of carbon dioxide footprint.2 Recently, the possibility of replacing petroleum-derived synthetic polymers with natural, abundant and low-cost biodegradable products has gained much interest in both academic and industrial fields.3,4 For instance, the production of plastics in Europe reached 57 million tons in 2012, mostly divided between polyethylene, polypropylene, poly(vinyl chloride), polystyrene and poly(ethylene terephthalate) production.5 These fossil-based plastics were consumed and discarded into the environment, generating 10.4 million tons of plastic waste, most of which ended up in landfills (Figure 1). Therefore the development of ‘‘environmentally friendly’’ materials will result in huge benefits to the environment and will also contribute to re- duced dependence on fossil fuels. Polymers produced from alternative RSC Polymer Chemistry Series No. 12 Poly(lactic acid) Science and Technology: Processing, Properties, Additives and Applications Edited by Alfonso Jime´nez, Mercedes Peltzer and Roxana Ruseckaite r The Royal Society of Chemistry 2015 Published by the Royal Society of Chemistry, www.rsc.org v vi Preface Figure 1 Plastics recovery in Europe for 2012.5 resources are a crucial issue, especially for short-life range applications, as they can be easily degraded by abiotic media or micro-organisms.6,7 Never- theless, the properties of these biomaterials are often behind those of common thermoplastics and some improvements are needed in order to make them fully operative for their industrial use. The most optimistic forecasts have indicated that the potential of substitution of biopolymers to conventional synthetic ones can reach 15.4 million tons in the European Union (EU) (33% of the production of plastic at present).5 The development of biopolymer matrices and their use in common applications is the subject of increasing interest by numerous research groups, since these materials are considered capable of substi- tuting to certain synthetic thermoplastics. The reasons for this increase in the number of studies on these materials reside in the improving major concern on society with regards to environmental aspects and sustainability of the consumer goods, as well as to strict governmental regulations in the use of non-degradable thermoplastics. General Issues on PLA Science and Technology There are many kinds of bio-based and biodegradable polymers, among which one of the most promising is poly(lactic acid) (PLA), a biocompatible thermoplastic aliphatic polyester.8 PLA is a linear thermoplastic polyester produced by the ring-opening polymerization of lactide. In general, com- mercial PLA grades are copolymers of poly(L-lactic acid) and poly(D,L-lactic acid), which are produced from L-lactides and D,L-lactides, respectively. The ratio of L-enantiomers to D,L-enantiomers is known to affect the properties of PLA,8,9 i.e. if the materials are semicrystalline or amorphous. Until now, most of the efforts reported in order to improve the properties of PLA have been focused on the semicrystalline material.8 Preface vii PLA is a most promising biopolymer, since it offers unique features of biodegradability as well as thermoplastic processability. PLA is used for many different applications, from packaging to agricultural products and disposable materials, as well as in medicine, surgery and pharmaceutical fields.10,11 Advanced industrial technologies of polymerization can be used in order to obtain pure PLA with high molecular weight, which is responsible for the improvement in the mechanical properties, with a better resistance to hydrolysis even under wet environment and adequate compostability.2 There are some problems relative to its application, such as difficulty in controlling the hydrolysis rate, poor hydrophilicity as well as the high rigidity and poor control of its crystallinity. These drawbacks can be solved by the addition of nanofillers and/or by blending PLA with other biodegradable polymers. The increasing research interest in PLA and PLA-based materials for multiple applications is represented by the large number of publications in scientific journals and monographs dealing with specific aspects in PLA science, technology and applications. A short survey of the recent literature reveals that the number of published articles related to PLA increased exponentially over the past decade, which is another clue to the worldwide rising interest in PLA research and innovation. Figure 2 shows some data taken from the Scopuss scientific database, where the increase in publications related to PLA research is clearly observed. The criterion for searching was the term ‘‘poly(lactic acid)’’ in the article’s title or keywords. Research in PLA involves a great amount of institutions and researchers around the world and reviews and monographs are necessary to extend knowledge in this important area in bio-based and sustainable materials. Some excellent works in reviewing the current research have been recently reported, most of them