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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
Presents new and innovative bio-based monomers to replace traditional petrochemical-based building blocks Featuring contributions from top experts in the field, this book discusses new developments in the area of bio monomers and green polymeric composite materials. It covers bio monomers, green polymeric composites, composites from renewable resources, bio-sourced polymers, green composites, biodegradation, processing methods, green polymeric gels, and green polymeric membranes. Each chapter in Bio Monomers for Green Polymeric Composites Materials presents the most recent research and technological ideas in a comprehensive style. It examines bio monomers for green polymer and the processing methods for the bio nanocomposites. It covers the preparation, characterization, and applications of bio-polymeric materials based blends, as well as the applications of biopolymeric gels in medical biotechnology. The book also explores the properties and applications of gelatins, pectins, and carrageenans gels. Additionally, it offers a plethora of information on green polymeric membranes; the bio-degradation of green polymeric composites materials; applications of green polymeric composites materials; hydrogels used for biomedical applications; and the use of natural aerogels as thermal insulations. * Introduces readers to the innovative, new bio-based monomers that are taking the place of traditional petrochemical-based building blocks * Covers green polymers, green composites, bio-sourced polymers, bio nanocomposites, biodegradable polymers, green polymer gels, and membranes * Features input from leading researchers immersed in the area of study Bio Monomers for Green Polymeric Composites Materials is suitable for academics, researchers, scientists, engineers and advanced students in the field of bio monomers and green polymeric composites materials.
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Seitenzahl: 496
Veröffentlichungsjahr: 2019
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Table of Contents
Cover
List of Contributors
Preface
1 Biomonomers for Green Polymers: Introduction
1.1 Processing Methods for Bionanocomposites
1.2 Biopolymeric Material‐based Blends: Preparation, Characterization, and Applications
1.3 Applications of Biopolymeric Gels in Medical Biotechnology
1.4 Introduction to Green Polymeric Membranes
1.5 Properties and Applications of Gelatin, Pectin, and Carrageenan Gels
1.6 Biodegradation of Green Polymeric Composite Materials
1.7 Applications of Green Polymeric Composite Materials
1.8 Constituents, Fabrication, Crosslinking, and Clinical Applications of Hydrogels
1.9 Natural Aerogels as Thermal Insulation
References
2 Processing Methods for Bionanocomposites
2.1 Introduction
2.2 Classification of NBCs
2.3 General Processing Methods for NBCs
2.4 Properties of NBCs
2.5 Future and Applications of NBCs
Acknowledgments
References
3 Biopolymeric Material‐based Blends: Preparation, Characterization, and Applications
3.1 Introduction
3.2 State of the Art in Biopolymeric Blends
3.3 Preparative Methods for Blend Formation
3.4 Blend Preparation by the Melting Process
3.5 Aqueous Blending Technology
3.6 Hydrophilic or Hydrophobic Biopolymeric Blends
3.7 Opportunities and Challenges
3.8 Summary
References
4 4Applications of Biopolymeric Gels in Medical Biotechnology
4.1 Introduction
4.2 Types of Biopolymeric Gels
4.3 Applications of Biopolymeric Gel
4.4 Conclusions and Future Perspectives
References
5 Introduction to Green Polymeric Membranes
5.1 Introduction
5.2 Types of Green Polymeric Membranes
5.3 Properties of Green Polymeric Membranes
5.4 Applications of Green Polymeric Membranes
5.5 Conclusion
References
6 Properties and Applications of Gelatin, Pectin, and Carrageenan Gels
6.1 Introduction
6.2 Gelatin
6.3 Pectins
6.4 Carrageenans
6.5 Future Prospects
Acknowledgments
References
7 Biodegradation of Green Polymeric Composites Materials
7.1 Introduction
7.2 Biodegradation of Green Polymers
7.3 Biodegradation of Composite Materials
7.4 Conclusion
References
8 Applications of Green Polymeric Composite Materials
8.1 Introduction
8.2 Biotechnological and Biomedical Applications of PEG
8.3 Industrial Applications
8.4 Conclusion
References
9 Hydrogels used for Biomedical Applications
9.1 Introduction
9.2 Hydrogels
9.3 Short History of Hydrogels
9.4 Methods of Fabrication of Hydrogels
9.5 Classification of Hydrogels
9.6 Natural Polymers Used for Hydrogels
9.7 Synthetic Polymers Used for Hydrogels
9.8 Crosslinking of Hydrogels
9.9 Biomedical Applications of Hydrogels
9.10 Conclusions
References
10 Natural Aerogels as Thermal Insulators
References
Index
End User License Agreement
List of Tables
Chapter 3
Table 3.1 The various forms of biopolymers.
Chapter 4
Table 4.1 Comparison of physical and chemical crosslinking.
Table 4.2 Ideal hydrogel materials based on functional properties.
Table 4.3 Absorption framework of porosity‐related characteristics of hydrogels.
Table 4.4 Pros and cons of bio‐based and synthetic polymers.
Table 4.5 World‐wide hydrogels resources.
Chapter 5
Table 5.1 Summary of the properties and pure water flux of regenerated cellulose...
Table 5.2 Latest advancement in chitosan‐based membranes in various applications...
Table 5.3 Applications of green polymeric membranes.
Table 5.4 Adsorption capacities of modified biopolymers for heavy metals [53].
Table 5.5 Comparison of separation performance with other polymeric membranes [5...
Table 5.6 Comparison of BB41 and BR18 removal between Ch‐g‐Ea and others in the ...
Chapter 6
Table 6.1 Applications of pectins and other polymer blends.
Table 6.2 Varieties and properties of carrageenan and its applications.
Chapter 8
Table 8.1 Applications of PLA. Adapted from [28].
Table 8.2 Applications of green polymer composites.
Chapter 10
Table 10.1 The average particle sizes of 1,4‐cis‐polybutadiene–CMS aerogel nanoc...
Table 10.2 Tensile properties of 1,4‐cis‐polybutadiene–CMS silica aerogel nanoco...
Table 10.3 Storage modulus and
T
g
values of 1,4‐cis‐polybutadiene–CMS silica ae...
Table 10.4 Published examples.
Table 10.5 Prediction of silica aerogel's thermal conductivity.
List of Illustrations
Chapter 2
Figure 2.1 Schematic presentation of nanoreinforcement material and matrix...
Chapter 4
Figure 4.1 Significant characteristics of hydrogels.
Figure 4.2 Preparation methods of hydrogels.
Figure 4.3 Factors affecting modification of hydrogel characteristics.
Figure 4.4 Stimuli responsive hydrogels in biomedical applications.
Chapter 5
Figure 5.1 SEM images of the RCM: (a) and (b) surface; (c) and (d) cross‐s...
Figure 5.2 SEM images of a cellulose hollow fiber membrane [25].
Figure 5.3 SEM images of dense and porous membranes produced with chitosan...
Figure 5.4 (a) Comparison of the thermal stability of RNP pulp, treated ce...
Figure 5.5 The ATR IR spectrum of the cellulose film illustrates that the ...
Figure 5.6 (a) Dead‐end filtration and (b) crossflow filtration.
Figure 5.7 Electrostatic interaction and hydrogen bonding (H‐bonding) of a...
Figure 5.8 SEM micrographs of different membranes: (a) pure CS, (b) CS/OSR...
Figure 5.9 (a) Chitosan scaffold (left) and chitin/nanosliver composite sc...
Figure 5.10 Proton conductivity, methanol permeability, and relative selec...
Chapter 6
Figure 6.1 Representative gelatin structure.
Figure 6.2 Schematic of pectin structure with its monomers.
Chapter 7
Figure 7.1 Classification of biodegradable polymers based on their source....
Figure 7.2 General classification of green polymers based on their origin....
Figure 7.3 Example data from a biodegradation test of a biodegradable biop...
Figure 7.4 Variation of PVA concentration recorded in the presence of an a...
Figure 7.5 Schematic illustration of the biodegradation of polymers.
Figure 7.6 SEM micrographs of the polymer and composites after different d...
Figure 7.7 (a) Tensile strength and (b) elastic modulus of samples before ...
Figure 7.8 PHB and standard cellulose: (a) PHB 0 days (350X) and (b) stand...
Chapter 8
Figure 8.1 PLA production (http://dx.doi.org/10.1016/B978‐1‐4377‐4459‐0.00...
Figure 8.2 L‐lactide, D‐lactide (meso‐lactide), and D‐lactide (http://dx.d...
Figure 8.3 Green composite parts of a Mercedes Benz car.
Chapter 9
Figure 9.1 Structure of collagen.
Figure 9.2 Structure of gelatin.
Figure 9.3 Structure of HA.
Figure 9.4 Structure of alginate.
Figure 9.5 Structure of CS.
Figure 9.6 Structure of xyloglucan.
Figure 9.7 Structure of dextran.
Figure 9.8 Structure of agarose.
Figure 9.9 Structure of heparine.
Figure 9.10 Structure of PAA.
Figure 9.11 Structure of polyimide.
Figure 9.12 Structure of PEG.
Figure 9.13 Structure of PVA.
Chapter 10
Figure 10.1 The chemical structure of 1,4‐cis‐polybutadiene.
Figure 10.2 Schematic diagram of the sol‐gel polymerization of resorcinol ...
Figure 10.3 Schematic diagram of the reaction of melamine with formaldehyd...
Figure 10.4 (a) Morphology of 1,4‐cis‐polybutadiene–CMS silica aerogel nan...
Figure 10.5 Stress‐strain curves of 1,4‐cis‐polybutadiene–CMS silica aerog...
Figure 10.6 Loading dependence of the tensile strength of 1,4‐cis‐polybuta...
Figure 10.7Figure 10.7 Loading dependence of the tensile modulus of 1,4‐ci...
Figure 10.8Figure 10.8 Loading dependence of the elongation at break of 1,...
Figure 10.9 Loading dependence of the toughness of 1,4‐cis‐polybutadiene–C...
Figure 10.10 Comparison of stress‐strain curves of 1,4‐cis‐polybutadiene–C...
Figure 10.11 Temperature dependency of the storage modulus of 1,4‐cis‐poly...
Figure 10.12 TEM image of an aerogel.
Figure 10.13 Conductivities of as‐prepared CNT aerogel samples.
Figure 10.14 (a) Discrete current pulses applied across a sample. (b) A 15...
Figure 10.15 External insulation (Aspen Aerogels).
Guide
Cover
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Bio Monomers for Green Polymeric Composite Materials
Edited by
P. M. Visakh
TUSUR UniversityRussia
Oguz Bayraktar
Ege UniversityTurkey
Gopalakrishnan Menon
Tomsk State UniversityRussia
Copyright
This edition first published 2019
© 2019 John Wiley & Sons Ltd
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Library of Congress Cataloging‐in‐Publication Data
Names: P.M., Visakh, editor. | Bayraktar, Oguz, editor. | Menon,
Gopalakrishnan, 1980‐ editor.
Title: Bio monomers for green polymeric composite materials / edited by Dr.
P.M. Visakh, TUSUR University, Russia, Dr. Oguz Bayraktar, Department of
Chemical Engineering, Ege University, Bornova, Izmir, Turkey, Dr.
Gopalakrishnan Menon, Tomsk State University, Russian Federation.
Description: First edition. | Hoboken, NJ : John Wiley & Sons, Inc., [2019] |
Includes bibliographical references and index. |
Identifiers: LCCN 2018061443 (print) | LCCN 2019000950 (ebook) | ISBN
9781119301691 (Adobe PDF) | ISBN 9781119301707 (ePub) | ISBN 9781119301646
(hardcover)
Subjects: LCSH: Biomedical materials. | Polymeric composites. | Polymer
colloids. | Biofilms. | Green chemistry. | Monomers.
Classification: LCC R857.M3 (ebook) | LCC R857.M3 B45 2019 (print) | DDC
610.28/4–dc23
LC record available at https://lccn.loc.gov/2018061443
Cover Design: Wiley
Cover Image: © T.Thinnapat/Shutterstock
List of Contributors
Bilahari Aryat
International and Inter University Center for Nanoscience and Nanotechnology,
Mahatma Gandhi University,
India
Nor Asikin Awang
Faculty of Chemical and Energy Engineering, Advanced Membrane Technology Research Centre (AMTEC), School of Chemical and Energy Engineering, Faculty of Engineering,
University Teknologi Malaysia,
Malaysia
Mohamad Azuwa Mohamed
Faculty of Chemical and Energy Engineering, Advanced Membrane Technology Research Centre (AMTEC), School of Chemical and Energy Engineering, Faculty of Engineering,
University Teknologi Malaysia,
Malaysia
Dipali R. Bagal‐Kestwal
Institute of Food Science and Technology,
National Taiwan University,
section 4, Taiwan, ROC
Muhammad Taqi Zahid Butt
Faculty of Engineering and Technology, Department of Metallurgy and Materials,
University of the Punjab,
Lahore, Pakistan
Been Huang Chiang
Institute of Food Science and Technology,
National Taiwan University,
Taiwan, ROC
Deepu A. Gopakumar
International and Inter‐University Center for Nanoscience and Nanotechnology,
Mahatma Gandhi University,
India
and
School of Industrial Technology,
Universiti Sains Malaysia,
Malaysia
Nafisa Gull
Research Scholar, Department of Polymer Engineering and Technology,
University of the Punjab,
Lahore, Pakistan
Atif Islam
Research Scholar, Department of Polymer Engineering and Technology,
University of the Punjab,
Lahore, Pakistan
Ahmad Fauzi Ismail
Faculty of Chemical and Energy Engineering, Advanced Membrane Technology Research Centre (AMTEC), School of Chemical and Energy Engineering, Faculty of Engineering,
University Teknologi Malaysia,
Malaysia
Athira Johnson
International and Inter‐University Center for Nanoscience and Nanotechnology,
Mahatma Gandhi University,
India
M. Karthika
International and Inter‐University Center for Nanoscience and Nanotechnology,
Mahatma Gandhi University,
India
Shahzad Maqsood Khan
Research Scholar, Department of Polymer Engineering and Technology,
University of the Punjab,
Lahore, Pakistan
M.H. Pan
Institute of Food Science and Technology,
National Taiwan University, No.1,
Roosevelt Road, section 4, Taiwan, ROC, 106
Muhammad Abdur Rehman
Department of Geology and Department of Chemistry,
Jalan University,
Kuala Lumpur,
Malaysia
and
Quality Control Laboratory,
Commander Agro,
Multan,
Pakistan
Zia ur Rehman
University of Agriculture Faisalabad,
Toba Tek Singh, Pakistan
Amin Saboktakin
Nanostructured Laboratory, NanoBMat Company,
GmbH, Hamburg, Germany
Mohammadreza Saboktakin
Nanostructured Laboratory, NanoBMat Company GmbH,
Hamburg, Germany
Neelakandan M. Santhosh
International and Inter‐University Center for Nanoscience and Nanotechnology,
Mahatma Gandhi University,
India
Nitheesha Shaji
International and Inter‐University Center for Nanoscience and Nanotechnology,
Mahatma Gandhi University,
India
Sabu Thomas
International and Inter‐University Center for Nanoscience and Nanotechnology,
Mahatma Gandhi University,
India
Şükrü Tüzmen
Molecular Biology and Genetics Program, Department of Biological Sciences,
Eastern Mediterranean University,
North Cyprus, Famagusta, Turkey
P.M. Visakh
Department of Physical Electronics,
TUSUR University,
Tomsk, Russia
Wan Norharyati Wan Salleh
Advanced Membrane Technology Research Centre (AMTEC),
Faculty of Chemical and Energy Engineering and Faculty of Engineering,
University Teknologi Malaysia
Malaysia
V.K. YaduNath
International and Inter University Center for Nanoscience and Nanotechnology,
Mahatma Gandhi University,
India
Zulal Yalinca
Department of Chemistry,
Eastern Mediterranean University,
North Cyprus, Famagusta
Turkey
Preface
This book summarizes many of the recent research accomplishments in the area of biomonomers for green polymeric composites and their nanocomposites. It includes an introduction to biomonomers for green polymers, the current status of these compounds, new challenges, opportunities, and processing methods for bionanocomposites, biopolymeric material‐based blends, the preparation, characterization, and applications of biomonomers and their nanocomposites, applications of biopolymeric gels in medical biotechnology, an introduction to green polymeric membranes, properties and applications of gelatins, pectins, and carrageenans gels, the biodegradation of green polymeric composite materials, applications of green polymeric composites materials, hydrogels used for biomedical applications, and natural aerogels as thermal insulations.
This book is a valuable reference source for university and college faculties, professionals, post‐doctoral research fellows, senior graduate students, and researchers from R&D laboratories working in the area of biomonomers and green polymeric composites materials. The chapters are contributed by prominent researchers from industry, academia, and government/private research laboratories across the globe and present an up‐to‐date record of the major findings and observations in the field of biomonomers and green polymeric composite materials.
The first chapter discusses the state of art and new challenges of biomonomers and green polymeric composite materials.
The second chapter covers several topics, including classification of nanobiocomposites, general processing methods, and properties. The author also includes many subtopics, such as polysaccharide nanocomposites, animal protein‐based nanocomposites, plant protein‐based nanocomposites, metal nanocomposites, and inorganic nanocomposites. General processing methods such as pressure extrusion, solid‐state shear pulverization, electrospinning, solution casting, evaporation, melt intercalation, in situ polymerization, drying techniques and polymer grafting are also discussed in this chapter.
Various topics on biopolymeric material‐based blends, such as preparation, characterization, and applications, are addressed in Chapter 3. This chapter presents a comprehensive study of biopolymeric material‐based blends, including general preparative methods, aqueous blending technology, their hydrophilic or hydrophobic nature, degradation problems, thermodynamics of miscibility, and their opportunities or challenges. Biopolymeric blends have attracted academic, research, and industrial scientists' attention as their properties are desirable for various applications. The challenges due to the unique structure, preparative methods, and resultant properties of blends of natural polymeric materials are discussed, and examples are drawn from the scientific literature. The various forms of natural polymers, i.e. polysaccharides, proteins, lipids, natural rubber, chitosan, starch, and silk‐based blends, are reviewed with respect to preparative techniques, characterization methods, and various applications.
The fourth chapter of this book discusses the applications of biopolymeric gels in medical biotechnology. The primary objective of this chapter is to review the literature regarding the classification of the properties of hydrogels and their biomedical applications. The composition and structure of hydrogels, especially their use in biological fields, makes them ideal candidates for biopharmaceutical implementation. Innovations in recent manufacturing and world‐wide resources of hydrogels are also reported.
The fifth chapter introduces green polymeric membranes, covering types of green polymeric membranes, their physicochemical properties, and their potential applications. The application of these materials in various industries was facilitated by their tremendous and significant physicochemical properties. However, despite these advances, there are still some drawbacks which prevent the wider commercialization of green polymeric membranes in many applications. This chapter reviews the current trend of research involving green polymeric membranes that focuses on the fabrication method, processing, and surface and structure modification. In addition, the long‐term stability and durability of green polymeric membranes for specific applications has become a challenge to researchers all around the world. The introduction of nanostructure fillers (e.g. graphene oxide, metal oxides, carbon nanotubes, nano‐clay, etc.) and the blending with other polymers, or the making of new copolymers, has significantly improved their overall properties and performance. These improvements are generally attained at low filler content, and this nano‐reinforcement is a very attractive route to generate new functional green polymeric membranes for various applications. It should be noted that the development of green polymeric membranes with specific physicochemical properties for specific functionalities is crucial for practical applications in industry. Green polymeric membranes with various physicochemical properties have a promising contribution to make in various applications.
Chapter 6 discusses the properties and applications of gelatins, pectins, and carrageenans gels. For each of these substances the authors cover various subtopics, such as structural units, molecular structure, properties, thickening ability, gelling ability, film‐forming properties, microbiological properties, food applications, cosmetics applications, and pharmaceutical applications. In the chapter on biodegradation of green polymeric composite materials, the authors consider a wide range of review studies on this subject, including biomechanical pathways for the degradation of green polymers and green polymer composites. Several studies have been carried out to design polymers with biodegradable properties to help keep the environment safe and clean.
In Chapter 8, on applications of green polymeric composites materials, the authors discuss several different topics, including a series of interesting green polymer composites developed from thermoplastic starch and its blends, poly(lactic acids) and its modifications, cellulose, gelatin, and chitosan. The authors also describe how natural fibers have more environmentally friendly properties than synthetic fibers synthesized from agricultural sources such as jute, banana, bamboo, and coconut coir, etc. There is thus a wide range of possible applications of nanocomposites from agriculture to automobiles. However, problems of poor adhesion of matrix and fiber, difficulty with fiber orientation, achieving nanoscale sizes, and the evolution of truly green polymers that are environmentally friendly and renewable must first be solved.
In Chapter 9, constituents, fabrication, crosslinking and clinical applications of hydrogels are described. Hydrogels are extensively found in everyday products although their potential has so far not been thoroughly investigated. The authors review the fabrication and composition of hydrogels along with their different properties, and the natural and synthetic polymers used for the development of hydrogels in the presence of different crosslinking agents. The major characteristics of hydrogels related to clinical, pharmaceutical, and biomedical applications are also identified, particularly for applications of hydrogels in contact lenses, oral drug delivery, wound healing, tissue engineering matrices, and gene delivery.
The final chapter examines the use of natural aerogels as thermal insulation and in other applications. A further review of natural aerogel‐based composites and nanocomposites is also provided.
The editors would like to express their sincere gratitude to all the contributors to this book, whose excellent support led to the successful completion of this venture. We are grateful to them for the commitment and the sincerity they have shown toward their contribution to the book. Without their enthusiasm and support, the compilation of this book would have not been possible. We would like to thank all the reviewers who have given their valuable time to make critical comments on each chapter. We also thank Wiley for recognizing the demand for such a book, and for realizing the increasing importance of the area of bio monomers for green polymeric composites materials and supporting this project.
Tomsk, Russia, March 2019
Dr. P.M. Visakh
Dr. Oguz Bayraktar
Dr. Gopalakrishnan Menon
1Biomonomers for Green Polymers: Introduction
P. M. Visakh
Department of Physical Electronics, TUSUR University, Tomsk, Russia
1.1 Processing Methods for Bionanocomposites
The new generation of hybrid nanostructured materials has two crucial properties: biocompatibility and biodegradability [1,2]. Exploitation of various biopolymers such as proteins, nucleic acids, polysaccharides, etc. for preparation of nanocomposites has been done in last few decades [3]. Processing methods for matrix and filler are sometimes the same. However, some matrices are prepared using combinations of techniques to achieve the desired quality of bionanocomposites, therefore we will discuss the processing methods for bionanocomposites with suitable examples. Bionanocomposites of polysaccharide matrices are mainly prepared by solvent intercalation or melt processing and not through in situ polymerization where nature of the polysaccharide directly influences the route of preparation. Some polysaccharides with nanostructure fillers are discussed as examples. Most of the cellulose whiskers‐reinforced poly(lactic acid) (PLA) nanocomposites are prepared by melt extrusion to avoid agglomeration and aggregation during drying [4]. Porous networks and thickened cellulose ribbons in gelatin/nanocellulose composites are prepared using an enzymatically modified form of gelatin [5]. Cellulose nanocomposites based on nanoparticles, such as clay [6–14], carbon nanotubes (CNTs) [15], graphene, layered double hydroxide (LDH) [16], and silica [17] have been prepared.
Starch is another abundant, inexpensive, naturally renewable and biodegradable polysaccharide, produced by most green plants as an energy store. It is the most common carbohydrate in human diets and animal feeds. Starch nanocomposites are mixtures of starch‐based biopolymers with nanofillers (solid layered clays, synthetic polymer nanofibers, cellulose nanowhiskers, CNTs, and other metal nanostructures). Environmentally friendly starch nanocomposites exhibit significant improvements in mechanical properties, dimensional stability, transparency, improved processability, and solvent or gas resistance. Chitosan (CS)/chitin, the second most abundant natural biopolymer, also can be integrated with clay, graphene, and carbon nanostructures to prepare bionanocomposites [18–21]. Due to its high content of amino (–NH2) and hydroxyl (–OH) groups, chitosan and its derivatives are excellent adsorbents for the removal of heavy metal ions, fluoride, and organic dyes. Films of spin‐coated chitosan–alginate nanocomposite have potential uses in bioapplications. Lignin‐based nanocomposite films have been prepared using CNCs (carbon nanocomposites) and used in various applications such as medical, biological, optical and sensors, and electronic [22]. They are also used as adhesives, stabilizing agents, and precursors for many aromatic chemicals. Modified lignins, such as lignosulfates, kraft lignin, and acetylated lignin, contain CNCs or commercial derivatives or nanocellulosic polysaccharides. Polyethylene terephthalate (PET) film coated with graphene oxide (GO)/pullulan nanocomposite can be used in food/pharmaceutical applications [23]. Bionanocomposites with enriched properties based on two microbial polysaccharides, pullulan and bacterial cellulose (BC), were prepared by Trovatti et al. for possible application in organic electronics, dry food packaging and the biomedical field [24]. Pullulan composites with many materials, including chitosan [25], caseinate [26], starch nanocrystals [27], collagen [28], poly (vinyl alcohol) [29], and hydrogel with methacrylate [30], have excellent compatibility.
Their biodegradability, low cost, and surfaced modification with active functional groups for catching targeting molecules make these matrices feasible candidates for applications in the pharmaceutical industry [31]. Electrospun collagen‐chitosan nanofibers were stabilized by glutaraldehyde vapor via crosslinking, which afforded a biomimetic extracellular matrix (ECM) for cell growth [32]. Collagen is regarded as one of the most useful biomaterials, exhibiting a number of biological advantages. The outstanding performance and biomedical application of this protein biomaterial have induced researcher interests in synthetic composite material fabrication. Soy protein isolate (SPI) has been extensively studied for bioderived packaging materials. Several recent studies have investigated the improvement of mechanical and barrier properties of nanocomposite films after incorporating nanoclays such as montmorillonite (MMT) [33–41]. Further, these nanocomposite films have also been reported for decreased water vapor and oxygen permeability, and increased elastic modulus and tensile strength, which makes them suitable for packaging industry. Recent studies have also reported that the SPI‐based nanocomposite bioplastics with highly exfoliated MMT have significantly improved mechanical strength and thermal stability [42]. Thus, bio‐based polycaprolactone–SPI is not only ecofriendly but intercalated nanocomposites with enhanced tensile and dynamic mechanical properties when produced by the melt compounding method [43].
In the case of biocomposites, the properties of the composites produced are dependent on the inter‐phase interaction of the reinforced material and matrix. Filler is also a value‐added material, but wise selection of processing methodology, optimum conditions, and compatible phase components is needed. Polymer/metal nanocomposites consisting of polymer as matrix and metal nanoparticles as nanofiller commonly exhibit several attractive advantages, such as electrical, mechanical, and optical characteristics [44]. Metal nanocomposites with protein, nucleic acid, and polysaccharides have shown potential applications in drug delivery, tissue engineering, bioimaging, wound healing, biomedicine, energy production and storage, and electronic devices such as biosensors, affinity materials, etc. [45]. Bottom‐up methods are found to be promising for controlling the properties and specific orientation of nanomaterials. Thermal evaporation and sputtering techniques have been considered as facile, simple, low‐cost, and high‐yield methods for synthesis of high‐quality nanomaterials/nanostructures [46,47]. Various immobilization methods, including entrapment, adsorption, crosslinking, electro‐polymerization, and encapsulation, have been used for capturing biological moieties in the matrix. This is one of the main processes employed in the manufacturing of nanobiocomposites (NBCs) [48]. There are two main types of extrusion: reactive extrusion and extrusion cooking. Reactive extrusion uses chemical modification via crosslinking [49]. Generally, extrusion technology used in the food industry is referred to as extrusion cooking and results in different physical and chemical properties of the extrudates depending on the raw materials and extrusion conditions used [50]. Various starch nanocomposite varieties have been prepared and reported by many researchers for biodegradable packaging applications in food industry. Moigne et al. developed a continuous CO2 assisted extrusion process to prepare poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/clays NBC foams with better homogeneity and high porosity [51]. Inventor Torkelson has successfully produced a well‐dispersed graphite–polymer nanocomposite [52]. Taking advantage of near‐ambient‐temperature processing, solid‐state shear pulverization (SSSP) was recently used to produce biodegradable polymer matrix composites with starch [53], rice husk ash [54], and eggshell filler [55,56]. This technique that has proven to effectively disperse nanoscale structural entities to achieve compatibilized polymer blends and exfoliated polymer nanocomposites.
This physical method uses extrusion of the polymer solution with reinforcement of nanomaterials and biological entity for the preparation of NBCs. Polymers, molten at high temperature, can also be made into nanofibers by electrically charging a suspended droplet of polymer melt or solution [57–63]. Instead of a solution, the polymer melt is introduced into the capillary tube. The major difference is that a compound spinneret with two (or more) components can be fed through different coaxial capillary channels [64]. Wet‐dry electrospinning and wet‐wet electrospinning techniques are used for volatile and non‐volatile solvents respectively. Both techniques offer the possibility of producing nanofibers with controlled fiber diameter to make film or membrane or an oriental controlled fiber. Such fibrous scaffolds are ideal for the purpose of tissue regeneration because their dimensions are similar to the components of the extracellular matrix and mimic its fibrillar structure, providing essential signals for cellular assembly and proliferation. Core–shell structured nanofibers where collagen as the shell and poly(ɛ‐caprolactone) (PCL) as core were prepared by co‐axial electrospinning and show the advantage of controlled shell thickness and manipulative mechanical strength and degradation properties of the resulting composite nanofibers, without affecting biocompatibility [65]. Thus, such core–shell structured composite nanofibers have potential uses in drug or growth factor encapsulation and the development of highly sensitive sensors and tissue engineering applications [66].
The solution casting method is based on a solvent system in which the polymer or pre‐polymer is soluble. The polymer is usually dissolved in a suitable solvent while the nanoparticles are dispersed in the same or a different solvent before the two are mixed. For example, during the preparation of bionanocomposites based on clays, the solvent is normally used to pre‐swell the clays [67]. In case of non‐water‐soluble polymers, additional steps are required before processing. Solvent exchange, use of surfactant, freeze‐drying, and chemical modification can be used for this purpose. Melt intercalation is a mechano‐chemical process that is highly preferred in case of clay/silicate biocomposites, and this processing method is compatible with extrusion and injection molding. This method is also fast and clean, ecofriendly, and can alter the lifecycle analysis [68]. In this technique nanomaterials and/or biomaterials are mixed with the polymer in the molten state. The process involves mixing the particles with the polymer and heating the mixture above the softening point of the polymer, statically or under shear.
Like other techniques, proper dispersion of the nanoparticles is always a goal during processing. During melt processing, a number of factors are important to achieve homogenous dispersion of reinforced nanomaterial into the polymer matrix, including enthalpic interaction between the polymer matrix, biocomponent, and nanoparticle. Multi‐walled CNT‐poly methyl methacrylate (MWNT/PMMA) nanocomposite has been prepared by in situ polymerization of MMA dispersed with MWNTs with fairly good dispersion stability [69]. Grafting of long chains can also be used to transform the nanofiller into a co‐continuous material by increasing apolar character through grafting agents bearing a reactive end group and a long “compatibilizing” tail [70].
1.2 Biopolymeric Material‐based Blends: Preparation, Characterization, and Applications
Preparation of biopolymeric blends is encouraged due to their biocompatible and biodegradable properties [71,72]. The reason for the increased research in the preparation of versatile biopolymer blends is their broad application, e.g. biomedical applications [73]. The biopolymer blends in this regard have emerged as promising materials with suitable thermal, biocompatible, and mechanical properties for use in the intended applications [74,75]. The main biopolymers used in the preparation of blends for various applications include collagen, chitin, chitosan, keratin, silk, and elastin, all natural polymers derived from animals [76,77]. Property of biopolymers is useful in blends formation with the other soluble polymers. The polymers with little solvent affinity, e.g. elastin, silk, or keratin, have a problem during blend formation [78,79]. The environmentally friendly nature of the biopolymers due to their biodegradable properties is also advantageous [80]. It is also notable that polymers have dominant hydrophobic properties, degrade after use, have mechanicalproperties, and behavior toward aqueous environments [81–84]. Biopolymeric blends are non‐biodegradable in nature [85] and therefore these do not have the natural advantage of environmental friendly properties.
The melt process in making biopolymeric blends is advantageous to overcome various shortcomings associated with the basic physicochemical properties of biopolymers. The new techniques were developed to make biopolymeric blends, e.g. reaction extrusion technology to make starch–cellulose–acetate blends. In this technology, a number of materials were used during the blend formation process. The biodegradable hydrogels were prepared by biopolymeric blends formed by the combination of starch derived from corn starch and cellulose acetate. The blending reaction proceeds through free radical mechanization after reaction between methacrylate or acrylic acid monomers. The free radical reaction was initiated through a redox system consisting of 4‐dimethylaminobenzyl alcohols and benzyl peroxide at ambient temperature. The addition of hydroxyapatite content in these blends provided a biocompatible character in the blended materials along with osteoconductive or oleophilic properties. The effect of polyol on the thermal stability, mechanical strength, and water or gas permeability was monitored to establish the usability of these blends. The study findings suggest that the polyol or water contents have a positive impact on the mechanical properties or stability of the biopolymeric blends [85]. The use of acetic acid promoted the formation of sheet‐like structures in the blended materials. The characterization results of the biopolymeric blends showed improved thermal stability and degradation stability. In another study, Lazaridou and Biliaderis studied the effect of blended materials on thermal and mechanical properties [86].
Blends formed by the injection molding method show higher tensile strengths, lower water absorption/adsorption, and longer elongation values. The impacts of the chemical or physical properties of the starch on the biopolymeric blend properties were studied by Park and Im [87]. The starch was gelatinized by the addition of a mixture of water and glycerol in a twin‐screw mixer. The microstructural properties of the starch blends with PLA, polyethylene, and vernonia oil were prepared by the melt processing technique and acid hydrolysis. Surface fractures were observed during scanning electron microscopic (SEM) examination of the blends. Polyvinyl alcohols (PVOHs) were also used as compatibilizers in PLA‐starch‐based biopolymeric blends [88]. This study reported that the use of PVOHs enables preparation of blends with better compatibility and improved mechanical strengths.
1.3 Applications of Biopolymeric Gels in Medical Biotechnology
Based on natural and synthetic polymers, hydrogels can be utilized in research into cell encapsulation and in particular have facilitated the establishment of a novel field in tissue engineering. Hydrogels are a significant class of biomaterials in medical biotechnology. These biomaterials categories may include tissue engineering and regeneration, diagnostics, cellular immobilization, cellular biomolecular separation, and utilization of barrier materials for biological adhesion for regulation. Hydrogels are invaluable in their three‐dimensional network capacity to capture and release active compounds and biomolecules. Hydrogels have the sponge‐like capacity to absorb water due to their hydrophilic functional groups. The water absorbed into hydrogels permits diffusion of certain molecules while the polymer component of the hydrogel acts as a matrix for holding water molecules together. Hydrogels have the ability to imitate the physical, chemical, biological, and electrical features of many tissues. These features earn them the ability to serve as potential candidates for biomaterials. These novel approaches involve super porous hydrogels [89], comb‐like grafted hydrogels [90–92], self‐assembling hydrogels [93,94], and recombinant triblock copolymers [95–97]. To construct hydrogel systems with well defined chemical characteristics, information regarding polymer chemistry and synthesis, features of the materials to be utilized, parameters of mode of interaction, material release capability, and delivery systems need to be taken in to consideration. In order to construct hydrogel systems with well‐defined chemical characteristics, information regarding polymer chemistry and synthesis, the features of the materials to be utilized, the parameters of the mode of interaction, material release capability and delivery systems need to be taken into consideration. Crosslinking is the most versatile method to facilitate biopolymeric deficiencies [98]. Mechanical properties and the stability of biomaterials can be ameliorated by crosslinking agents. However, limitations exist due to reduced degradability and lack of functional groups and potential cytotoxicity introduced by crosslinking agents [99,100]. The chemical and physical nature of hydrogels depends on the concentration of crosslinking agents, the degree of crosslinking, the kind of crosslinker/monomer, and the method of preparation used. Hydrogels are excellent candidates for biotechnological applications, including drug delivery systems, since they possess soft, hydrophilic, high swelling ability, a viscoelastic nature, are biodegradable, and have biocompatible characteristics [101]. Hydrogels can provide protection towards small biological molecules and chemical compounds against stringent environmental conditions.
The mode of response of hydrogels may depend on the chemical composition of the polymeric networks. Hydrogels can be modified to respond to environmentally triggered stimuli, including changes to pH, ionic strength, and temperature. Novel treatments for site‐specific drug release utilize specifications such as disease‐specific enzymatic activities to prompt the release of drugs from hydrogels [102]. Hence, the use of hydrogels provides feasible drug release due to their chemical composition in response to environmental stimuli [103]. Hydrogel‐based products are potential candidates for drug‐delivery systems, providing the necessary conditions for drug release [104,105]. Hydrogels are considered to be one of the best‐qualified materials for this purpose. Successful applications of tissue engineering are facilitated by the generation of functional hydrogels [106].
1.4 Introduction to Green Polymeric Membranes
Green polymeric membranes have been extensively commercialized in the field of membrane science and technology, and involve various membrane separation processes, e.g. microfiltration, ultrafiltration, nanofiltration, reverse osmosis, gas separation, pervaporation, and renewable energy [107–116]. There is a wide range of naturally occurring polymers produced from renewable resources that are available for numerous material applications. These renewable resources include cellulose and chitosan, which are widely employed in manufacturing. Chitosan‐based membranes can be prepared by an immersion–precipitation process that applies silica particles as porogen [117]. Chitosan powder is first dissolved in 2 wt% HNO3 before being cast as a film. Chitosan‐based ceramic membrane can also be prepared via the dip coating technique [118]. Bierhalz et al. formulated chitosan from white mushroom and shrimp shells [119]. Celluloses and chitosan can form cohesive films since they are flexible and they can be cast into different sizes of films. Moreover, there is a strong interaction between cellulose chain molecules due to intramolecular and intermolecular hydrogen bonding within the cellulose molecule. Cellulose can be considered to possess moderate thermal stability. It has been reported that rapid chemical decomposition of cellulose occurs between 315 and 400 °C [120], while chitosan decomposition occurs between 175 and 400 °C. Modification of the surface chemistry of the cellulose also allows the surface groups to be tailored to specific applications. For example, the surface silylation of cellulose will increase the hydrophobicity. It has been reported that cellulose films with a high water contact angle (117–146°) can be prepared from modified cellulose by solution casting [121]. Technologies such as coagulation and ion exchange that were developed for heavy metal removal work well, but have several disadvantages, such as low efficiency and high cost for energy and materials. Besides cellulose, chitosan is another significant biopolymer that can be obtained from chitin by the deacetylation process. Chitosan is biocompatible, non‐toxic, and biodegradable in nature. It differs from cellulose in that it will dissolve in most organic solvents, whereas chitosan is soluble in water in which a small amount of acetic acid is present.
Effluent consisting of pharmaceutical compounds such as antibiotics, vasodilators, β‐blockers, organic pollutants (e.g. phenolic compounds), and anti‐epileptics has been found in most wastewater, sewage, groundwater, and drinking water [122]. Various kinds of bio‐based polymers are used for many applications nowadays since they are environmentally friendly and low in cost. Mohamed et al. had successfully prepared regenerated cellulose membrane with photocatalytic properties in an effort to produce green portable photocatalysts and photocatalytic membranes from the degradation of organic pollutants [123]. Thakuro et al. reviewed an application of water purification which involved the separation of pure water from various mixtures of tetrachloride (CCl4), chloroform (CHCl3), and dichloromethane (CH2Cl2) [124]. The fabricated composite membrane was crosslinked with tetraethyl ortosilicate (TEOS) to minimize the swelling and improve the selectivity of the membrane. Such waste discharge, containing colored substances, normally comes from the textile industries and other dyeing fields such as paper, printing, food, and plastics. The approximate volume of discharged wastewater, especially from the textile process, is between 40 and 65 l kg−1 of the product [125]. The hybrid CS/OSR (Oxidized starch)/silica membrane produced showed that there was an improvement in terms of thermal stability as well as the ability to lower the degree of swelling in the water.
The applications of biopolymers in dye removal focus on chitosan, but also involved the use of cellulose. As we know, cellulose can be abundantly modified and is a renewable biopolymer in nature. The structure of the cellulose, with the presence of a hydroxyl group, allows it to undergo chemical modification that can improve its efficiency for dye removal from water. Tsurumi et al. reported similar research on the capability of cuprammonium regenerated cellulose hollow fiber (BMM Hollow Fiber) for virus removal applications. In addition, graphene oxide‐modified chitosan/polyvinyl pyrrolidone nanocomposite membranes [126] and polycaprolactone membrane coated with chitosan‐silver nanoparticles [127] prepared by the electrospinning technique demonstrated remarkable potential applicability in wound‐healing tissue engineering applications.
1.5 Properties and Applications of Gelatin, Pectin, and Carrageenan Gels
Gels are defined as non-fluid colloidal networks or polymer networks that expanded throughout whole volume by a fluid [128]. They are liquid by weight but due to a three‐dimensional crosslinked network within the liquid they behave like solids. Crosslinking within the fluid results in a gel structure because of the contribution of hydrogen bonds, helix formation, and complexation at the network junction points. A hydrogel is a network of polymer chains that are hydrophilic, and sometimes exhibits as a colloidal gel in which water is the dispersion medium. Hydrogels are highly absorbent and they can contain over 90% water. Hydrogels also possess a degree of flexibility very similar to natural tissue due to their significant water content. The first appearance of the term “hydrogel” in the literature was in 1894 [129]. Hydrogels can be classified by various methods based on source (natural or synthetic) [130], configuration (crystalline, semi‐crystalline, or non‐crystalline), crosslinking type (chemical or physical), and polymeric composition (homopolymeric, copolymeric, or multipolymer interpenetrating polymeric hydrogel (IPN)), and they are an important and integral part of tissue engineering, cosmetics, dentistry, and the food industry. Readers can get more detailed information from review articles [131–134]. In this chapter we will focus on biopolymeric hydrogels, especially gelatin, pectin, and carrageenan, which are widely used in the food industry.
Gelatin is obtained from the acid, alkaline, or enzymatic hydrolysis of collagen, the chief protein component of the skin, bones, and connective tissue of animals, including fish and poultry [135]. Fish gelatin has similar functional characteristics to mammalian gelatin and has received considerable attention in recent years [136,137]. Molecular weight (MW) distribution and amino acid composition influence the physical and structural properties of gelatins from various sources [138–140]. Because of their similar amino acid composition and, to some extent, structure, collagen and gelatin show similarities in their properties [141–144]. However, gelatin as a polymeric product exhibits characteristic properties that are important in various industrial applications. The hydrolytic conversion of collagen to gelatin yields different mass peptide chains. Thus, gelatin is not a single chemical entity, but a mixture of fractions composed entirely of amino acids joined by peptide linkages to form polymers varying in molecular mass from 15 to 400 kD [145–152].
The rate of the formation of a helical structure of gelatin depends on numerous factors such as the presence of covalent bonds [153], gelatin molecular weight [154], the presence of imino acids, and the gelatin concentration in the solution. Gelatin is insoluble in less polar organic solvents such as benzene, acetone, primary alcohols, and dimethylformamide, but soluble in aqueous solutions of polyhydric alcohols such as glycerol, propylene glycol, etc. It is also soluble in highly polar organic solvents such as acetic acid, trifluoroethanol, and formamide, and partially soluble in benzene, acetone, primary alcohols, and dimethylformamide [155]. Gelatin is hygroscopic, meaning that it absorbs water depending on the relative humidity at which it is stored. Gelatin has positive and negative charges along with uncharged hydrophilic and hydrophobic groups, which make it a polyampholyte [156]. Together with water gelatin forms a semi‐solid colloidal gel which is thermoreversible. This is certainly its most interesting property. One part of gelatin can trap 99 parts of water. The two most important properties of gelatin are its melt‐in‐the‐mouth characteristics and its ability to form thermoreversible gels. Gelatin is also stable at a wide range of pH and remains unaffected by ionic strength. It is preferred in many applications because of its clarity and bland flavor. In most cases, except for the food industry, gelatin is used in the solid state. Gelatin is sometimes used in the baking sector. Other than as a food ingredient, gelatin is also used as a food additive and acts as a thickening agent, gelling agent, stabilizer, and emulsifier.
A study by Gomez‐Guillén et al. [140] revealed antimicrobial activity associated with gelatin. Gelatin films have commercial application as food packaging films [157,158] because of their edible, biodegradable and antibacterial, heat sealing, moisture, and oxygen barrier properties. Gelatin is used as a binder in tablet formulations and as a coating to ease swallowing or mask unpleasant tastes. Cosmetics companies are also important users. The properties of gelatin are particularly well suited to the encapsulation of bath oils, and for use in moisturizing lotions and skin creams, making it an important contributor to these products. Neutral sugars such as L‐rhamnose, xylose, galactose, and arabinose are also present in gelatin side chains. However, the total content of neutral sugars varies with the source, the extraction conditions, and subsequent treatments [159]. Gelatin also carries non‐sugar substituents, usually methanol, acetic acid, phenolic acids, and occasionally amide groups.
The junction zones resulting from polymer molecule interactions must be of limited size. As a result of large chain size, precipitation may happen instead of gel formation. Pectin use in edible films, paper substitute, foams, and plasticizers, etc. In addition to pectolytic degradation, pectins are susceptible to heat degradation during processing, and this degradation is influenced by the nature of the ions and salts present in the system [160]. Pectin is used in sulfuric in lead accumulators. Carrageenan is a mixture of water‐soluble, linear, sulfated galactans. It is an anionic linear sulfated polygalactan polymer with 15–40% ester‐sulfate content. The molecular weight of carrageenan is usually high but depends on many factors, such as type of seaweed species, age of seaweed, harvesting season, extraction method, and condition. Carrageenan recovery can be achieved by several methods. Alcohol precipitation or potassium chloride followed by steam heating is commonly used to get “refined carrageenan” (RC) [161]. An alternative process involves immersion and boiling in hot aqueous potassium hydroxide.
1.6 Biodegradation of Green Polymeric Composite Materials
The term “biodegradability” means the decomposition of materials by microorganisms into methane, carbon dioxide, inorganic compounds, water, and biomass [162]. A huge number of biopolymers (collagen, cellulose. starch, chitin, etc.) have been identified and extracted from various biological sources. Based on the source of the material, biopolymers can be classified into biomass products, microorganism‐derived products, biotechnologically obtained products, and oil products. Biopolymers like starch, cellulose, and chitin are the major examples of agro polymers and these have a wide range of applications because of their high availability and biodegradability, and low toxicity. The degradation of polymeric materials follows various stages, including biodeterioration, depolymerization, assimilation, and mineralization. One major factor is that the degradation can stop at each stage. Agro‐based polymers can be polysaccharides like cellulose that consist of glycosidic bonds and proteins obtained from amino acids. Polymers based on natural products are both biocompatible and biodegradable, but they still need to be technologically acceptable. The major advantages of biodegradable polymers are that they can be composted with organic wastes and returned to enrich the soil, their use will not only reduce environmental pollution but will also lessen the labor cost for the removal of plastic waste in the environment because they are degraded naturally, and their decomposition will help increase the longevity and stability of landfills by reducing the volume of garbage [163]. Apart from biotic environmental factors like microorganisms, abiotic factors like photodegradation, hydrolysis, and oxidation add to the biodegradation process [164–166]. Conversion of biodegradable materials or biomass to gases, water, salts, minerals, and residual biomass is called mineralization [167].The degradation process can be either aerobic or anaerobic [168]. Biodegradation of polymers includes a change in the properties, such as tensile strength, color, shape, molar mass, etc., of a polymer or polymer‐based product under the action of environmental agents like heat, light, or chemicals [169].
A polymer's complexity, structure, and composition are the most important aspects that govern its biodegradability. Another structural characteristic of polymers is the possible branching of chains or the formation of networks (crosslinked polymers). The microbes digest the starch, yielding a porous, sponge‐like structure with a high surface area and low structural strength. Once the starch element has been depleted, the compound matrix begins to be degraded by an enzymatic attack. Several other polymers are degraded by exposure to chemicals and broken to small particles, which are further degraded upon microbial degradation. It has been reported that soil microbes are able to start the depolymerization of many natural polymers such as cellulose and hemicelluloses [170]. Maria Ratajska et al. (1998) investigated the biodegradation of new polymeric materials of natural origin and their mixtures with other natural and synthetic polymers [171]. Biodegradable composites have great importance because of the problem of the solid waste generated by plastic materials after their use. By blending natural fibers with the polymers, such as PLA, starch blends, cellulose acetates, and polyhydroxyalkanoates (PHA), a fully biodegradable material can be manufactured. Materials of this kind are known to decay under defined conditions, which are usually different from the ambient conditions under which they are used. To reduce their harmful impact on the environment and allow them to be altered during organic waste recycling processes, recently various materials have been added to plastics to improve their biodegradability. Natural fiber reinforced composites are renewable, environmentally friendly, low cost, lightweight, and have high specific performance. The chemical structure and constitution of the composites determine the biodegradability of plastics. Biodegradation is brought about by biological activity predominantly by the enzymatic action of microorganisms and can be measured by standard tests for a specified period of time.
Molecular degradation in aerobic and anaerobic conditions is triggered by enzymes, leading to complete or partial removal of the residue from the environment. The rate of biodegradation of composites of natural polymers has been studied in various environments, such as soil, compost, and weather. The degradability of thermoplastic starch and PVOH blends under anaerobic conditions to simulate the most common disposal environment for household wastes. Also mostly PVOH remained at the end of the digestion and that starch was almost entirely degraded. The degradability of thermoplastic starch and PVOH blends under anaerobic conditions to simulate the most common disposal environment for house hold wastes. However, the PVOH content significantly impacted the rate of starch solubilization [172].
1.7 Applications of Green Polymeric Composite Materials
Green polymeric composite materials are formed by the combination of a biodegradable polymer as a matrix and natural fibers as reinforced materials [173]. These ecofriendly composites have good mechanical (e.g. strength and elastic modulus), thermal, electrical, and chemical properties [174]. Based on their renewability, green polymeric composites can be divided into two categories: renewable composites and partially renewable composites. Renewable composites contain both matrix and reinforced materials that are renewable, but in partially renewable composites either the matrix or the reinforced material is renewable [175]. Biodegradable polymers have huge potential for applications in clinical, packing, andagricultural industry. Thin films of biodegradable polymers are used for early cropping and interrupt early weed formation [176]. Green polymers like cellulose have an excellent barrier properties and keep materials under airtight [177]. The polyethylene glycol (PEG)‐derived detergent Triton X‐1l4 can be dispersed in a buffer, stirred with a crude protein mixture, and heated above the cloud point to form a two‐phase system and partition the proteins. A chromatographic form of partitioning can also be derived by immobilizing the dextran–water phase on a chromatographic support and eluting with the PEG–water phase.
Examples of medically useful PEG‐altered proteins include PEG–asparaginase for analysis of acute leukemias [178], PEG–adenosine deaminase for therapy of acute combined immunodeficiency disease [179], and PEG–superoxide dismutase and PEG–catalase for reducing tissue damage emanating from reactive oxygen species correlated with ischemia and associated pathological circumstances [180]. PEG displays attractive characteristics when applied as a tether or linker to couple an active molecule to a surface. In this treatment, the PEG operates to suppress non‐specific protein adsorption on the surface. Additionally, the tethered molecules have been demonstrated to be remarkably active, performing virtually as loose molecules in solution. PLA is a biodegradable polymer that has a collection of applications. It has been extensively employed in the biomedical and pharmaceutical fields for several decades due to its biocompatibility and biodegradability.
Green polymer‐based nanocomposites are ideal for making packaging materials and product casings such as cell phone covers and biodegradable bags and wraps. Their biocompatibility along with the antimicrobial properties and UV absorption properties of the fillers gives these composites an advantage over traditional packaging and casing materials. Biodegradable scaffolds can be used to support and guide the in‐growth of cells. Tissue scaffolds must be biodegradable, biocompatible, and also sterilizable. An ideal scaffold should have enough mechanical strength for withstanding physiological strains and must provide a suitable environment for cellular growth. Biocompatible composites, by solution mixing and freeze‐drying processes, can be utilized in scaffold preparation. Hydrogels can be developed from polymers and can be used in tissue engineering. Thermoresponsive polymeric nanocomposite gels can impart large elongation at break and high moduli and strength. Connective tissue membranes for wound healing can be developed using a lithium chloride/dimethylacetamide mixture through solvent casting as they possess adequate swelling and moisture transmission abilities. They also have excellent antibacterial properties [181].
Recent developments in this PCL based composites area exploring antibacterial, antioxidant properties of the biomaterials filler have been found ideal for packaging materials [182]. Three types of technology are commonly used for food packaging materials: nanoreinforcement packaging, nanocomposite active packaging, and nanocomposite smart packaging. Nanoreinforcement can enhance polymer flexibility, temperature/moisture stability, and gas barrier properties.
1.8 Constituents, Fabrication, Crosslinking, and Clinical Applications of Hydrogels
Biodegradable and biocompatible natural polymers demonstrate a renewable and versatile substitute for synthetic polymers. Physical properties such as permeation, swelling, mechanical strength, and surface characteristics can be tailored via structural modifications [183]. Moreover, hydrogels can be prepared in different physical forms, such as films, coatings, nanoparticles, microparticles, and slabs. Natural polymer‐based hydrogels are suitable for drug delivery and tissue engineering of bioactive molecules [184]. In medicine, numerous hydrogel products based on natural or synthetic polymers have had a huge impact on patient care in the modern era. Hydrogels are used in a broad range of experimental medicine and clinical practice applications, e.g. regenerative medicine and tissue engineering [185], diagnostics [186], cellular immobilization [187], as barrier materials to regulate biological adhesions, separation of biomolecules or cells, etc. [188]. Wichterle and Lim illustrated the polymerization of HEMA and a crosslinker using water and other solvents. Instead of hard and brittle, they found it to be elastic, water swollen, clear, and a soft gel. Formulations of hydrogels have progressively developed over the years [89] and they can now be fabricated by different chemical methods. Natural polymer‐based hydrogels are normally biocompatible and have nominal stimulation to the immunological or inflammatory receptiveness of the host tissues. Numerous natural polymers have been extensively explored as biomaterials for reparative medicine and tissue engineering.
Physical or chemical compositing and amendments are used to induce specific interactions (electrostatic interactions and hydrogen bonding), functionalities and/or well‐defined micro‐ or nanostructures in implants to enhance the toughness, strength, and bioactivity of the implants. Synthetic and natural polymers are combined to form a strengthened hydrogel, known as a hybrid hydrogel. Collagen strands can self‐assemble to form strong fibers [189]. Additionally, fibers and scaffolds can be formed from collagen and their mechanical strength can be improved by using different crosslinkers (i.e. carbodiimide, formaldehyde, glutaraldehyde) [190,191], by crosslinking with physical treatments (i.e. heating, freeze‐drying, ultraviolet (UV) irradiation) [192], and by blending with other natural and synthetic polymers, i.e. polyethylene oxide (PEO), chitosan (CS), poly(lactic‐co‐glycolic acid) (PLGA), poly(glycolic acid), PLA, and HA [193–195].
Protein‐based hydrogels can be prepared by a thermal gelation process and their mechanical characteristics can be improved via chemical crosslinking agents like glutaraldehyde [196]. The growth factors in matrigel impart cell migration through the activation of a G‐protein, modulation of cell attachment, and remodeling of the cytoskeleton [197,198
