File Name: polylactic acid pla biopolymer technology and applications .zip
A short summary of this paper. PREFACEIn past few years, due to the increase of environmental pollution and global worming, the development of systems based on sustainable use of materials has accelerated. Particularly interesting is the effective usage of the limited carbon resources and the conservation of the energy resources.
In this framework, bio-based polymers, made from biomass, can play an important role. The reasons of the growing interest in the development of biodegradable plastics are environmental and strategic.
As a matter of fact, in order to reduce the environmental impact of plastics especially in terms of CO 2eq released in the environment some of the products obtained from agriculture starch, cellulose, wood, sugar, etc.
This way the net balance of carbon dioxide is reduced since growing bioplastic feedstocks remove carbon dioxide from the atmosphere. Furthermore, petroleum, with a constantly rising price, is replaced by renewable raw materials obtained from agriculture. Traditional plastics undergo degradation phenomena with very slow kinetics; hence, the volume occupied by these materials in landfills is virtually stable over time.
On the other hand, bioplastics show higher degradation rates in landfills and, therefore, the required volumes can be reduced. It is worth highlight that the word ''bioplastic'' is actually ambiguous, because it can refer simultaneously to two different aspects, which are not necessary connected. Furthermore, a plastic based on renewable sources biobased may not be biodegradable i. Finally, there are also bioplastics that are both biodegradable and bio-based such as polylactic acid PLA , which represents a solution for the need of environmentally-friendly packaging materials produced from renewable sources and biodegradable plastics with a low environmental impact.
Although PLA has been produced for several decades, its use was limited to biomedical application e. The breakthrough occurred in the early s when Cargill Inc. Since then, the scientific interest on the PLA has grown exponentially over the years, together with the importance that it has acquired on the market. Nowadays, thanks to its unique features in terms of versatility and reliability, PLA is the most important and most used bioplastic in the world.
This book will appeal to all the readers who not only want to have a reference book of consolidated notions on PLA, but also, and especially, to those who want to discover new potentials and new application fields of this unique biodegradable polymer. The book describes the synthesis, properties and applications of PLA through 14 original and very interesting chapters that will guide the reader through a fascinating journey into the world of the PLA, providing interesting insights for those who intend to use this polymer for innovative applications, or simply those who want learn more about this very important biodegradable and bio-based plastic.
The book starts with an overview of the different types of PLA which are now available on the market and mechanical characteristics and properties, strengths and weaknesses of PLA are reported. Then the book continues with chapter 2, where the reader can find an useful review of the different production techniques of PLA-based copolymers, at the aim of extending the already broad range of applications of this biopolymer.
Chapters 3 and 4 are intended to give a better insight of the PLA processability, through the analysis of mechanical behaviour, thermal stability and kinetics of thermal decomposition of PLA.
Some possible techniques for improving the mechanical properties and processability of PLA by adding polyesters are also presented and discussed. The creation of composite materials that can meet the most demanding users' expectations is certainly a very important field and therefore, in this book some chapters will be devoted to this subject.
Through chapters 5 and 6 the reader will know the great potentials of the PLA in the construction of composites and nanocomposites, appreciating the great versatility of this polymer. At the beginning of this preface it has been mentioned that the PLA is not only a biobased plastic: its biodegradability introduces this polymer in a world of eco-friendly and human-friendly applications in several technological fields.
Therefore, chapter 7 is dedicated to deepen the PLA degradation, delving into the hydrolysis mechanisms which are the basis of the PLA biodegradability. After chapter 7, the reader is catapulted into the fascinating world of PLA applications, ranging from environment to the biomedical fields, from pharmaceutical to food industry, to go up to the conservation of cultural heritage.
Particularly, in chapter 8 a comprehensive survey of conservation materials and the most relevant achievements related to the application of PLA in conservation of cultural heritage are reported and discussed, while chapter 9 deals with the end of life of PLA by analysing the flash co-pyrolysis of biomass with polylactic acid through a statistical and comparative analytical investigation.
Chapters from 11 to 14 are dedicated to PLA applications in the pharmaceutical and biomedical fields, introduced by a review reported in chapter 10 on interesting applications of PLA in biomedical, food packaging and structural fields. Then, chapter 11 reviews recent progress in engineering PLA-based thermal-responsive shape memory polymers and discusses their potential and limitations for biomedical applications. Chapters 12 and 13 are devoted to the investigation of the production of PLA microcapsules for drug delivery with different techniques.
The fascinating journey on the PLA world concludes with chapter 14, which describes the preparation methods to obtain PLA structures with a nanometric thickness and a large surface area. The main features of such devices and the possibilities of functionalizing them by the inclusion of nanoparticles with targeted physical properties in the polymeric matrix are presented. Finally, let me conclude this preface by thanking all the authors who have contributed to the realization of this book, without whom this project would have never been born.
I thank them for their participation and patience during the preparation of this book and I am grateful that they have entrusted me to edit their contributions. I hope the readers will find this book useful. I am looking forward to receive comments and constructive feedbacks about contents. There are high capital and operating costs as well as environmental pollution problems associated with incineration.
Used dumped polymeric materials such as plastic bottles and containers, tyres and electric switches have slow or nominal degradation in the landfill. The landfills are limited and dumped polymeric materials contain toxic materials such as lead and cadmium which were used as colorants, stabilizers and plasticizers during their production. These toxic materials may leach to the soil and impose serious environmental risk . Moreover, petrochemical resources are progressively diminishing and the oil prices are radically increasing.
All of these issues add with increasing consumer interest in sustainable green products and have sparked research and development in favor of biodegradable polymeric materials from renewable resources. Polylactic acid or polylactide PLA belongs to the family of aliphatic polyesters is one of the most widely used biodegradable materials  manufactured from lactic acid that in turn is produced from renewable resources such as corn, sugarcane and rice .
Besides being biodegradable and having produced from renewable resources, PLA provides numerous other benefits including: fixation of carbon dioxide, a greenhouse gas ; significant amount of energy savings ; improvement of farm economies  and manipulation of physico-mechanical properties using polymer architecture such as orientation, blending, branching, cross-linking, or plasticization .
Figure 1 shows the novel ecologically friendly life cycle of PLA. Although production processes for lactic acid and PLA are well known , very few processes have been commercialized  and still the cost of PLA is not very competitive with synthetic plastics [19,22]. The core of PLA production technology is the fermentative production of lactic acid and its recovery [19,22]. Many processes are reported in the literature for the recovery of lactic acid  and still offer an extensive scope for research and development.
In addition to being biodegradable, PLA has many favorable properties such as good biocompatibility and bioresorbability , barrier properties [10,18], mechanical strength [31,32] and the ability to reinforce fillers [33,34].
All of these properties make it a polymer of choice for biomedical e. This chapter deals with production sources i. Recently, there has been a renewed interest in lactic acid production because it is the monomeric precursor of PLA . The physical properties of PLA depend on this isomeric composition [38,39]. Therefore, for PLA production fermentative pathway is desirable not only as a renewable resource, but also to obtain desired physical properties.
Over the years several authors have studied a large number of carbohydrates for production of lactic acid . Their investigations were on the basis of the increase of the yield of lactic acid, optimization of the production of biomass, minimization of the formation of by product, enhancement of the rate of fermentation, reduction of any pre-treatments involved, ease of availability and reduction of costs involved .
In the USA, corn is the cheapest starch-rich and most widely available annually renewable resource from which lactic acid is produced. Conversion technologies to facilitate the use of lignocellulosic biomass feedstocks, such as corn stover stover refers to stalks, leaves and cobs that remain in corn fields after the grain harvest to revitalize the soil , grasses, wheat and rice straws, and bagasse the pulpy residue of sugarcane have also been investigated .
Lactic acid has also been produced by simultaneous saccharification and fermentation of pre-treated alpha fibre . Although for the renewable sources to be converted to lactic acid, most investigations have paid attention to the carbohydrates, the finicky nature of lactic acid bacteria is still the main hurdle to the economical feasibility of the fermentation process.
The fermentation processes to obtain lactic acid can be classified into two types namely, heterofermentative and homofermentative depending on the type of bacteria used.
In the heterofermentative method less than 1. In the homofermentative method an average of 1. Most lactic acid bacteria require a wide range of growth factors including amino acids, vitamins, fatty acids, purines, and pyrimidines for their growth and biological activity [46,47] and the more supplemented the medium, the higher the productivity of the lactic acid could be obtained.
Among the various complex nitrogen sources for lactic acid fermentation e. However, for the production of lactic acid as a source for commodity chemicals, yeast extract is not cost effective [54,55]. Therefore, efforts have been given to use other sources of growth factors from industrial byproducts to achieve a partial or total replacement of yeast extract .
Synthesis Routes of ProductionSynthesis of PLA can be obtained generally by two routes, namely i direct condensation of lactic acid [16,60] and ii ring-opening polymerization ROP of lactide a cyclic dimmer of lactic acid [39,61] as shown in Figure 2. In ROP route, either D-lactic acid, L-lactic acid, or a mixture of the two are prepolymerized to obtain an intermediate low molecular weight poly lactic acid , which is then depolymerized into a mixture of lactide stereoisomers.
Lactide is generally formed by the condensation of two lactic acid molecules as follows: L-lactide from two L-lactic acid molecules, D-lactide from two D-lactic acid molecules, and mesolactide from one L-lactic acid and one D-lactic acid molecule. Melting point, mechanical strength and crystallinity of PLA are determined by different proportions of L, D, or meso-lactide and the molecular weight are determined by the proper addition of hydroxylic compounds.
The presence of both meso-and D-lactide forms in the PLA introduces sufficient irregularity to limit crystallinity. This results in PLA polymers with a wide range of hardness and stiffness values.
Since direct condensation route is an equilibrium reaction, the achievable molecular weight using this route may become limited due to the difficulties of removing trace amounts of solvent such as water at the end of the polymerization process due to hydrolysis of ester bonds .
Thus, although direct condensation is the least expensive route , other approaches such as azeotropic dehydration to remove most of the condensation water in the direct esterification process have been assessed [18,65]. However, most work has been focused so far on the ring opening polymerization of lactide for the production of pure high molecular weight PLA [18,19].
Synthesis by Direct Condensation of Lactic AcidPLA produced by direct condensation of lactic acid is a brittle polymer and generally unusable . This polymerization technique has some other drawbacks including need for large reactor, evaporation, solvent recovery and increased racemization . The use of chain coupling agent or esterification promoting adjuvents to increase the molecular weight of PLA adds cost and complexity to the process [20,.
The advantages of esterification promoting adjuvents are that the final product is highly purified and free from residual catalysts and oligomers . To produce high molecular weight PLA without the use of chain coupling agents or adjuvents and the drawbacks associated with them, azeotropic dehydration or azeotropic condensation polymerization method is employed by Mitsui Chemicals, Japan [18,72].
This polymerization method gives considerable amount of catalyst residue which may cause degradation and hydrolysis during processing. For biomedical applications, this residual catalyst is deactivated or precipitated and filtered out .
The molecular weight of PLA is of critical importance for the type of biomedical application. Generally, the construction of screws and plates for use as orthopedic implants needs material with high Young's modulus with molecular weight in the area of several hundreds of thousand . Henton et al. For ROP of lactide, many catalyst systems have been assessed to increase the reaction productivity including metallic, organometallic, inorganic and organic complexes of aluminum, zinc, tin, and lanthanides [19,20,70,77,78].
Even strong bases such as metal alkoxides have also been used with success to some extent . Depending on the catalyst system and reaction conditions, many mechanisms such as cationic , anionic  and coordination [81,82] have been proposed to explain the kinetics, side reactions, and nature of the end groups observed in ROP of lactide [19,83]. Among the studied catalyst systems, tin compounds, especially tin II bisethylhexanoic acid stannous octoate, Sn Oct 2 which is approved by the US Food and Drug Administration , are preferred for the bulk polymerization of lactide due to their solubility in molten lactide, high catalytic activity, low toxicity and ability to give high molecular weight with low rate of racemization of the polymer [19,85].
This chapter gives an up-to-date overview of the uses of biopolymers in automotive applications. This book was released on 09 June with total pages Biopolymers are natural polymers produced by the cells of living organisms. These are abundant in nature and are either derived directly from biological systems or chemically synthesized. Materials Sciences and Applications , 5 , These polymers offered a bioactive matrix for design of more biocompatible and intelligent materials. Valizadeh , S.
Request PDF | Polylactic Acid: PLA Biopolymer Technology and Applications | Polylactic Acid (PLA) is the first viable thermoplastic that can be produced from a.
Polylactic acid PLA is one of the main components of biodegradable and biocompatible composites. Bacterial cellulose from kombucha membranes is an excellent candidate to be used as a natural filler of eco-composites because it is renewable, has low cost, low density, and acceptable specific strength properties, and is biodegradable. The study aimed to prepare composites of PLA and bacterial cellulose to produce a biodegradable and compostable material. The bacterial microcellulose was obtained from kombucha membranes and blended with PLA by extrusion. We characterized the PLA, bacterial microcellulose, and composites to ascertain their size and aspect, degree of crystallinity, distribution of the cellulose into PLA, and their mechanical properties.
Biodegradable polymers are identified as substantial materials for biomedical applications. Among widely used biodegradable polymers in biomedical applications, poly lactic acid PLA is becoming one of the most paramount polymers. However, their synthesis reactions are affected by several parameters such as polymerization time, temperature, pressure, catalysts, and the polarity of the solvent. Moreover, equilibrium reactions are controlled through utilizing a hydrophilic monomer such as ethylene glycol EG. These factors can strongly impact final properties of PLA. Thus, it is indispensable to comprehend the effect of operating parameters during the polymerization process.
It was written by the following authors: Lee Tin Sin. Other books on similar topics can be found in sections: Science , Technology , Medicine. The book was published on It has pages and is published in Hardback format and weight g. Other books you can download below. Our bisontinesbisontins.
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Polylactic Acid PLA is the first viable thermoplastic that can be produced from a plant-based feedstock such as corn or sugar cane, and yet be processed by the conventional melt processing technologies. At the same time, Polylactic Acid is produced at the largest industrial scale of all biodegradable polymers. It is being used in biomedical applications, for bottle production and in compostable food packaging. It is also being evaluated as a material for tissue engineering.
Сьюзан Флетчер вздохнула, села в кровати и потянулась к трубке. - Алло. - Сьюзан, это Дэвид. Я тебя разбудил. Она улыбнулась и поудобнее устроилась в постели.
На лицах тех застыло недоумение. - Давайте же, ребята. -сказал Джабба.
Простите… может быть, завтра… - Его явно мутило. - Мистер Клушар, очень важно, чтобы вы вспомнили это. - Внезапно Беккер понял, что говорит чересчур громко. Люди на соседних койках приподнялись и внимательно наблюдали за происходящим.
Буфет всегда был его первой остановкой. Попутно он бросил жадный взгляд на ноги Сьюзан, которые та вытянула под рабочим столом, и тяжело вздохнул. Сьюзан, не поднимая глаз, поджала ноги и продолжала следить за монитором.
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