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Scrivener Publishing
100 Cummings Center, Suite 541J
Beverly, MA 01915-6106

Publishers at Scrivener
Martin Scrivener (
Phillip Carmical (

Advanced Green Composites






Edited by

Anil Netravali

Department of Fiber Science & Apparel Design, Cornell University, Ithaca, NY, U.S.A.







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Polymer composites are made of two distinct components: matrix or resin (continuous phase) and filler or reinforcement (discontinuous phase) and have properties that cannot be achieved by a single component alone. Conventionally, advanced composites have been defined as those that have excellent tensile properties. Three factors contribute to their high tensile properties: (1) high strength fibers such as carbon, aramid, or glass used as reinforcement, (2) good resins such as epoxies, and (3) excellent bonding between the fiber and the resin. Specific tensile properties of advanced composites are significantly higher than most metals because of their low density. As a result, advanced composites have replaced metals in many applications from aerospace to sports gears and from automobiles to wind turbines. It is being envisioned that future civil structures such as bridges and buildings will use advanced composites in place of steel, which will require significantly larger volumes. As we know, every material has a life span, and advanced composites are no exception. Unfortunately, we have not found an environmentally friendly way to dispose these composites at the end of their useful life nor have we found any sustainable raw material source to make them. Composites, at present, use unsustainable petroleum as the raw material to synthesize fibers and resins and end up in landfills at the end of their life, making that land useless for any other use for several decades or even centuries. Fortunately, this is slowly beginning to change with the advent of green polymers that are derived from fully sustainable plant based sources. Green composites are also being fabricated using these polymers with plant based fibers as reinforcement. At the end of their life, they can be easily composted, rather than being dumped into landfills. Thus, they can not only save the petroleum but also the land used for landfills.

Significant research is going on around the world to develop green composites that use both fibers and resins that are derived from plants. However, composites using common fibers such as jute, kenaf, sisal, ramie, hemp, banana, and many others have only moderate tensile properties, comparable to wood and wood-based products such as particle board and medium density fiber (MDF) boards. They are not suitable for structural applications where much higher strength and stiffness are required. Their durability, fire performance, and other functionalities are also not par with conventional composites. As a result, their applications have been very limited.

In the last decade or so, however, many new developments in the area of green composites have come about that are changing the landscape drastically. For example, high strength cellulose fibers have been developed using liquid crystalline cellulose solutions and air-gap wet spinning technique used for spinning Kevlar® fibers. Being 100% cellulose, they are fully degradable. Although this technology is still not mature, fibers with strength in the range of 1.5–1.7 GPa have been obtained. Furthermore, researchers have found ways to improve their properties further to around 2.0 GPa using chemical and heat treatments under tension. There is great promise that once the technology matures, these fibers could have tensile properties close to Kevlar®. Advanced green composites with high strength and stiffness have already been fabricated using these fibers and soy protein and maize starch based resins that would be suitable for structural applications.

Other than high strength and stiffness, composites are also being developed with a wide range of functional properties for a variety of applications. This has changed the conventional definition of Advanced Composites based on mechanical properties and now includes all composites that have special functional properties such as high transparency, fire resistance, ultra-light weight, autonomously repairing, and resin-less composites. Researchers have been able to obtain many of these properties in green composites as well, making them Advanced Green Composites.

This book provides the current state of advanced green composites that have been developed or are at the research stage of being developed with a variety of functional properties. Chapter 1 presents a broad introduction to green composites and their development to date. In Chapter 2, Rahman and Netravali discuss green resins that have been derived from plant-based sources and seem to be promising to fabricate structural composites. The chapter also discusses some of the most promising bio-based and inorganic nano-fillers that are considered as potential candidates for enhancing the properties of these green resins. Improving resin tensile properties should automatically reflect on composite properties made using them. The third chapter by Huang and Chen discusses the development of high strength cellulosic fibers, the primary load-bearing component in current green composites. Viscose rayon process used for spinning cellulose fibers is more than a century old and is incapable of producing high strength cellulose fibers. This chapter provides an overview of high strength cellulosic fibers that can be obtained from liquid crystalline solutions of cellulose derivatives and nonderivatized cellulose as well as new methods to reinforce the liquid crystalline solutions of cellulose. It is to be noted that all high strength advanced green composites, until today, have been made using liquid crystalline cellulose (LCC) fibers. In the fourth chapter, Hsieh highlights top-down and bottom-up approaches to generate ultra-fine cellulose fibers of nano-scale dimensions, micro- and meso-porous and sheath-core hybrid structures as well as surface-functionalized fibrous materials. Micro- and nano-fibrillated cellulose (MFC/NFC) and other forms of nanocelluloses have high strength as well as aspect ratio and can be efficiently extracted from a variety of waste products such as apple, carrot, and orange pulps that remain after extracting juice, grape, and tomato skins, various straws, etc. They have been used as reinforcement in resins among many other applications. Chapter 5 discusses up to date efforts in developing high strength composites that use LCC fibers and are termed as advanced green composites. There are other opportunities for obtaining high strength composites as well. For example, researchers are trying to develop high strength fibers from spider-silk like protein. Once such fibers are commercially produced, they can be used to make green composites. Bacterial nanocellulose is another fiber with high strength. If these fibers can be oriented, they would be excellent as reinforcement as well. Chapter 6, by Fujisawa and colleagues, summarizes the latest in a new class of composites that do not require resin at all. These composites are made using only one component, cellulose, which acts as the reinforcing fibers as well as the resin that bonds the fibers. These all cellulose composites (ACC) are considered a green alternative to glass- and carbon-fiber-reinforced polymer composites. The authors also provide a future perspective on ACC development for applications in various fields, including optical devices, food, and medicine. Chapter 7 presents composites that have the ability to autonomously self-heal the damages such as microcracks, punctures, cuts, and scratches that result from the constant stress and strain they are subjected to during use. The damages continue to accumulate, ultimately failing the composites. Self-healing is designed to heal the damages as they occur and, hence, can increase the service life of the composites significantly. The chapter discusses different ways developed by researchers to achieve self-healing in conventional composites and how some methods have been extended to self-heal green resins and green composites. Self-healing green resins and composites, with increased service life, should be more acceptable in mainstream applications in the future. In Chapter 8, Nakagaito and colleagues discuss optically transparent composites that have been developed of late for use in place of glass as substrates in electronic devices. Flexible electronics represents a common technology employed in gadgets that are ever-present in our daily lives. Among them, electronic displays are about to become flexible and foldable in the near future. Nanofibers that are invisible to our eyes can not only strengthen amorphous polymers but retain their transparency and also reduce their coefficient of thermal expansion, a critical requirement for electronic displays. Making transparent green composites is an active area of research at present and this chapter presents a thorough review of the current efforts. One of the deficiencies of the thermoset green resins such as plant-based proteins and starches as well as poly(lactic acid) is their brittle nature. That also translates into brittle composites. This is the topic of Chapter 9 in which Goda discusses ways of toughening composites with an emphasis on their impact properties. Chemical treatments of natural cellulosic fibers can make them stronger or tougher. Another key strategy to obtaining higher toughness is to control fiber/resin interfacial shear strength.

Chapter 10 by Obradovic and colleagues introduces the science, technologies, and applications of ultralight porous green composites in the form of biofoams. The chapter presents a thorough review of the biofoam compositions, process methods, properties as well as their performance and applications. In Chapter 11, Xia and colleagues discuss fire retardants developed from renewable resources. Most fibers and composites used in construction, transportation, electronics, and protective textile applications must have fire retardant functionality. Commercially available halogenated flame retardants tend to be toxic and persist in the environment for a long time. The authors, based on the current state of research, conclude that exploring the use of renewable materials as feedstock for FR alternatives is quite promising. In addition to sustainability aspects, the research has unlocked exciting new possibilities in fundamental understanding of fire retardants and their mechanisms of action. Chapter 12 by Gupta et al. discusses the recent technological advancements and innovations in the development of novel biodegradable polymers and nanofillers derived from renewable feedstock with a strategy to convert “waste into wealth” with special focus on green composite films for stringent food packaging that require excellent barrier properties. Finally, in Chapter 13, Osorio and colleagues discuss nanocellulose-based composites in biomedical applications. Although cotton has been used in gauzes for treatment of wounds since ancient times, nanocellulose-based composites have become of great interest in biomedical applications, given their inherent biocompatibility. Nanocellulose from microorganism assembly is similar to that of collagen, the major component of extracellular matrices, and its applications are diverse, ranging from scaffolds for tissue engineering, implants for cell regeneration or biosensors. Although the chapter discusses some relevant biomedical applications of nanocellulose based composites, authors predict that in medium to long term, nanocellulose-based composites will play an important role for developing in vitro tissues and organs, accelerating healing processes and improving life quality of mankind without impacting the environment.

The book covering a broad range of green technologies should be of interest to researchers in academia, in government research labs, and R&D personnel in a host of industries (e.g., aerospace, automotive, biomedical, composites, fibers, medical, microelectronics, packaging, plastics, textiles, and others) who are interested in designing with green fibers, polymers, and composites or advancing the sustainable materials technology. Industries such as aerospace and automotive that are increasingly turning to composites for lightweighting each component but use conventional composites should be able to find greener alternatives in their applications. Anyone working in sustainable plastics/polymers and composites industries should find this book of great interest and very useful as well.

It is my great pleasure to thank all those who made this book possible. First and foremost, I would like to profusely thank the outstanding authors who spent enormous amount of their valuable time in writing the chapters. Sharing their deep knowledge in the field and cutting edge research they are involved in, with the interested community, is greatly appreciated. This book would have been impossible to complete without their hard work, sustained interest, great enthusiasm, and cooperation. Thanks are also due to Martin Scrivener (Scrivener Publishing) for his unwavering support, interest, and encouragement, as well as patience in getting this book completed.

Anil N. Netravali
Cornell University
Ithaca, NY
August 2018