Nanocellulose E-Book
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- Sprache: Englisch
NANOCELLULOSE This book provides the latest up-to-date information on the exciting applications of nanocellulose in human diseases by giving in-depth explanations of their synthesis, characterization, and real-world applications in the biomedical sectors. Nanocellulose is a promising nanomaterial with unique qualities including low cost, durability, non-toxicity, accessibility, etc. Cellulose can be classified into two types: nanocrystals and nanofibrils, depending on the way it is extracted from trees, plants, or other cellulose-containing species. Textiles, cosmetics, and food products are just a few of the commercial uses for nanocellulose. However, it also has strong potential for use in medicine. The book presents the most recent scientific research on nanocellulose as a biopolymer and its potential uses in medicine. The reader will discover: * explains the synthesis of bacterial nanocellulose from different bacterial species and their characteristics; * details processes and applications of electrospinning and the synthesis of novel nanocellulose-based nanocomposite materials; * discusses the various surface functionalization processes of cellulose and their advantages and disadvantages; * delves into the application of nanocellulose in tissue engineering and grafting, such as in wound dressing and implants; * discusses nanocellulose as a carrier for drug delivery, as well as the synthesis of antibacterial nanocomposites for treating multi-drug-resistant bacteria; * explores the role of nanocellulose in the treatment of renal failure, nanocellulose hydrogel for ophthalmic and dental applications. Audience Researchers in areas including environmental biotechnology, bioprocess engineering, renewable energy, chemical engineering, nanotechnology, biotechnology, and microbiology will be interested in this book.
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Table of Contents
Cover
Table of Contents
Series Page
Title Page
Copyright Page
Preface
1 Nanocellulose: A Cutting Edge Biopolymer - An Overview
1.1 Introduction
1.2 Nanocellulose: A Brief Overview
1.3 Extraction of Nanocellulose
1.4 Surface Modification and Functionalization for Nanocelluloses
1.5 Applications of Nanocellulose in Polymeric Composites
1.6 Summary and Prospects
References
2 Cellulose Nanofibers (CNF) and Nanocrystals (CNC): Pre-Treatment, Preparation, and Characterization
2.1 Introduction
2.2 Cellulose Nanofibers (CNF)
2.3 Cellulose Nanocrystals (CNC)
2.4 Characterization
2.5 Conclusion
References
3 Synthesis and Characterization of Bacterial Nanocellulose
3.1 Introduction
3.2 Structure and Functions of Proteins Involved in Bcs Operon
3.3 Diverse Nature of Bcs Operon
3.4 Regulation of Bacterial Nanocellulose Biosynthesis
3.5 Genetic Manipulation of BNC Producing Strains to Increase Yield
3.6 Factors for BNC Production
3.7 Characterization of Bacterial Nanocellulose
3.8 Conclusion
References
4 Process and Applications of Electrospinning
4.1 Introduction
4.2 A Brief History of Electrospinning
4.3 Setup for the Experiment
4.4 Principle of the Process
4.5 Factors Affecting the Process of Electrospinning
4.6 Electrospinning Variations
4.7 Applications of Electrospun Fibers
4.8 Summary, Conclusion and Future Prospects
References
5 Development of Nanocellulose-Based Nanocomposites and Its Properties
5.1 Introduction
5.2 Nanocellulose
5.3 Nanocellulose-Based Nanocomposites
5.4 Properties of Nanocellulose-Based Nanocomposites
5.5 Conclusion
References
6 Surface Functionalization Process: Its Advantages and Disadvantages
6.1 Chemical Approach
6.2 Enzymatic Approach
6.3 Physical Techniques
6.4 Conclusion
References
7 Applications of Nanocellulose in Tissue Engineering and Tissue Grafting
7.1 Introduction
7.2 Nanocellulose and Its Properties
7.3 Classification of Nanocellulose and Their Synthesis
7.4 Composites Based on Nanocellulose
7.5 Applications of Nanocellulose in Tissue Engineering and Tissue Grafting
7.6 Limitations of Nanocellulose
7.7 Future Prospects
7.8 Conclusion
References
8 Application of Nanocellulose for Wound Dressings
8.1 Introduction
8.2 Types of Wounds
8.3 Nanocellulose-Based Wound Dressings
8.4 Commercialized Nanocellulose-Based Wound Dressings
8.5 Future Perspective and Conclusion
Acknowledgments
References
9 Use of Nanocellulose as Drug Carriers for Drug Delivery Applications
Abbreviations
9.1 Introduction
9.2 Strategies for Drug Delivery
9.3 Application of Various Biomaterials for Drug Delivery
9.4 Different Methods Involved in Nanocellulose Synthesis
9.5 Types of Nanocellulose
9.6 Different Methods Used for Drug Loading/Encapsulation of Drug in Nanocellulose
9.7 Importance of Nanocellulose as Drug Carrier
9.8 Drug Delivery via Different Nanocelluloses
9.9 Nanocellulose-Based Drug Delivery in Pathological Disorder
9.10 Commercialized and Research-Associated Nanocellulose Products Reported in Clinical Trials
9.11 Future Perspective
9.12 Conclusion
Acknowledgments
References
10 Preparation of Antibacterial Nanocomposite Materials Using Nanocellulose
10.1 Introduction
10.2 Nanocellulose
10.3 Functionalization of Nanocellulose
10.4 Nanocellulose-Based Nanocomposite
10.5 Properties of the Nanocomposites
10.6 Nanocellulose-Based Nanocomposite Processing
10.7 Antibacterial Properties of the Nanocomposite Material
10.8 Conclusions and Future Trends
References
11 Application of Nanocellulose for Treatment of Renal Failure
11.1 Introduction
11.2 Renal Disease and Its Implications
11.3 Nanocellulose—Concept and Formulation
11.4 Kidney-Targeted Drug Delivery by Nanocellulose
11.5 Conclusion
References
12 Use of Nanocellulose Hydrogels for Ophthalmic Applications
12.1 Introduction
12.2 Nanocellulose Overview
12.3 Nanocellulose Compatibility for Ophthalmic Applications
12.4 Nanocellulose Hydrogel
12.5 Ophthalmic Application of Nanocellulose
12.6 Conclusion and Future Aspect
References
13 Application of Nanocellulose as Implant and Grafting Materials
13.1 Introduction
13.2 Chemical as Well as the Structural Makeup of Cellulose Fibers
13.3 Cellulose—Origin, Extraction, and Sources
13.4 Isolation, Chemical Transformations, and Purification of Cellulose
13.5 Application of Nanocellulose as Implant and Grafting Materials
13.6 Conclusion
References
14 Use of Nanocellulose for Dental Applications
14.1 Introduction
14.2 Application of Nanocellulose in Dental Science
14.3 Conclusion
References
15 Future Prospects of Bacterial Nanocellulose and Its Composites
Abbreviations
15.1 Introduction
15.2 Cellulose
15.3 Bacterial Nanocellulose (BNC)
15.4 Bacterial Nanocellulose-Based Hybrid Nanocomposites
15.5 Biomedical Applications of BNC
15.6 Conclusion
Acknowledgments
References
Index
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Several sources for cellulose fibre synthesis [18–20].
Table 1.2 Comparison between the different types of nanocellulose.
Table 1.3 Detection of polymer nanocomposites through microscopy techniques.
Chapter 2
Table 2.1 Comparative extraction process of CNF/CNC w.r.t. energy or chemical ...
Chapter 3
Table 3.1 Characteristic features of Bcs operon.
Table 3.2 Differences between static culture and stirred culture.
Chapter 5
Table 5.1 Various nanocellulose extraction processes.
Table 5.2 BNC production from various microorganisms, biomass and culture mode...
Chapter 6
Table 6.1 Summary of advantages and disadvantages of different surface modific...
Chapter 7
Table 7.1 Summary of Features and application of different types of nanocellul...
Chapter 9
Table 9.1 Recent updates on clinical trials conducted using nanocellulose-base...
Chapter 10
Table 10.1 A summary of development of nanocellulose-based nanocomposites foll...
Chapter 11
Table 11.1 Nanocellulose formulation and its therapeutic applications in renal...
Chapter 12
Table 12.1 A comprehensive list of plants that may be utilized to extract cell...
Chapter 13
Table 13.1 Types, common names, sources, size and formation of nanocellulose m...
List of Illustrations
Chapter 1
Figure 1.1 The hierarchical structure of cellulose, which extends from the met...
Figure 1.2 Conversion of lignocellulosic biomass into nanocellulose.
Chapter 2
Figure 2.1 FE-SEM images of sugarcane bagasse as a raw material at (a) 100 μm ...
Figure 2.2 XRD patterns of CNCs isolated from cellulose (C1) precursors. (Key:...
Figure 2.3 TGA thermograms (a), and DTG (b) curves for raw sisal fibers and sa...
Figure 2.4 FTIR spectra of CNCs (a) from various sources and CNFs (b) extracte...
Chapter 3
Figure 3.1 A simple representation of cellulose production pathway from glucos...
Figure 3.2 Diversity of bcs operon; Class I bcs operon of
Komagataeibacter xyl
...
Figure 3.3 An overview of characterization of bacterial nanocellulose.
Chapter 4
Figure 4.1 Timeline of the history of electrospinning.
Figure 4.2 Basic setup of electrospinning [22].
Figure 4.3 Metallic collectors. (a) Stationary flat plate, (b) drum collector,...
Figure 4.4 Side-by-side electrospinning setup [22].
Figure 4.5 Coaxial spinneret and coaxial electrospinning setup [22].
Figure 4.6 Tri-axial spinneret and tri-axial electrospinning setup [22].
Figure 4.7 Multichannel spinneret and multichannel electrospinning setup [22].
Figure 4.8 Different types of electrospun fibers.
Figure 4.9 Applications of electrospinning.
Figure 4.10 Experimental setup for core-shell fiber preparation via coaxial ai...
Chapter 5
Figure 5.1 Composition of nanocomposite.
Figure 5.2 Classification of nanocomposites based on the matrices and processi...
Chapter 6
Figure 6.1 Schematic diagram for surface modification of nanocellulose.
Chapter 7
Figure 7.1 Instances of applications of nanocellulose in tissue engineering an...
Chapter 8
Figure 8.1 Acute wound and chronic wound healing.
Figure 8.2 Different forms of wound dressings prepared from nanocellulose.
Figure 8.3 Nanocellulose-based sponge with Janus character.
Chapter 9
Figure 9.1 Figure depicted multiple nanocellulose manufacturing techniques usi...
Figure 9.2 Schematic representation of nanocellulose entrapped drug delivery t...
Chapter 10
Figure 10.1 Sources of cellulose.
Figure 10.2 Different classes of nanocellulose.
Chapter 11
Figure 11.1 Anatomy of the human kidney [21].
Figure 11.2 (a) Cellulose in plant and trees has a schematic structure from me...
Figure 11.3 Schematic representation of nanocellulose aerogel formulation [51]...
Chapter 12
Figure 12.1 Schematic representation of the preparation of nanocellulose throu...
Figure 12.2 Fishbone diagram of isolation and preparation procedure of nanocel...
Chapter 13
Figure 13.1 Cellulose unit [10].
Figure 13.2 Molecular makeup of cellulose [10].
Figure 13.3 Schematics of an idealized cellulose fiber in Figure 13.3 depict o...
Figure 13.4 Individual chains of glucose residues are polymerized into (a) mic...
Figure 13.5 Nanocellulose typically exists as the cellulose nanofibrils, CNC, ...
Figure 13.6 Schematic representations of cellulose nanocrystals and nanofibril...
Figure 13.7 Replacements of meniscus (the given figure shows the meniscus of p...
Figure 13.8 For vascular grafts of small diameter as a replacement material, t...
Figure 13.9 Using Nanoskin
®
, a diabetic ulcer was totally cured after 7...
Figure 13.10 BASYC tubes [74].
Figure 13.11 Seven BASYC
®
tubes were used during micronerve surgery on ...
Figure 13.12 SEM photos of the hollow tubes’ inner and outer areas shown in th...
Figure 13.13 (a) Use of a negative silicone mold that is negative, helping dir...
Chapter 15
Figure 15.1 The different types of BNC nanocomposites prepared by incorporatio...
Figure 15.2 The application of bacterial nanocellulose in different fields.
Guide
Cover Page
Table of Contents
Series Page
Title Page
Copyright Page
Preface
Begin Reading
Index
WILEY END USER LICENSE AGREEMENT
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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106
Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])
Nanocellulose
A Biopolymer for Biomedical Applications
Edited by
Mainak Mukhopadhyay
Department of Bioscience, JIS University, West Bengal, India
and
Debalina Bhattacharya
Department of Microbiology, Maulana Azad College, Kolkata, India
This edition first published 2024 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA© 2024 Scrivener Publishing LLCFor more information about Scrivener publications please visit www.scrivenerpublishing.com.
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Library of Congress Cataloging-in-Publication Data
978-1-394-17237-5
Cover image: Pixabay.ComCover design by Russell Richardson
Preface
Nanocellulose is a promising nanomaterial with unique qualities including low cost. durability, non-toxicity, accessibility, etc. Basically, cellulose can be classified into two types: nanocrystals and nanofibrils, depending on the way it is extracted from trees, plants, or other cellulose-containing species. Textiles, cosmetics, and food products are just a few of the commercial uses for nanocellulose. It also has a strong potential for use in medicine.
This book presents the most recent findings in scientific research on nanocellulose as a biopolymer and its potential uses in medicine. The most recent research on nanocellulose structure and modification is presented in this book, along with in-depth details on the material’s present and potential future uses.
Chapter 1 focuses on the basic structure of nanocellulose their different sources, nomenclatures, and types. Different types of nanocellulose (nanocrystals and nanofibrils), their production, pretreatment, and characteristics have been discussed in Chapter 2. Currently, bacterial nanocellulose has gained more attention than plant cellulose or fungal cellulose.
Chapter 3 explains the synthesis of bacterial nanocellulose from different bacterial species and their characteristics. Nanofibrillated cellulose is produced by a simple technique using a high-voltage electrode known as electrospinning. In Chapter 4, the detailed processes and applications of electrospinning have been summarised. Nanocellulose is also studied for the synthesis of novel nanocomposite materials. Chapter 5 focuses on the development of nanocellulose-based nanocomposites and their properties. Cellulose is insoluble in water, so surface modification is required to maintain the balance between its hydrophobic and hydrophilic constituents.
Chapter 6 discusses the various surface functionalization processes of cellulose and their advantages and disadvantages. Based on various surface functionalizations, nanocellulose is extensively used in several biomedical fields. Chapter 7 emphasizes the application of nanocellulose in the field of tissue engineering and grafting, their advantages, future prospects, etc. As nanocellulose-based biomaterials show excellent biocompatibility, reduced cytotoxicity, and biodegradability, one of their outstanding biomedical applications is wound dressing. Chapter 8 focuses on the application of nanocellulose in wound dressing. Based on various surface functionalizations, nanocellulose is extensively used as a carrier for drug delivery, which is discussed in Chapter 9. Another very promising application of nanocellulose is the synthesis of antibacterial nanocomposites for treating multi-drug-resistant bacteria.
Chapter 10 delves into the synthesis of antibacterial nanocomposites from nanocellulose, while Chapter 11 explores the role of nanocellulose in the treatment of renal failure. Chapter 12 emphasises nanocellulose hydrogel for ophthalmic applications. Chapter 13 focuses on the utilisation of cellulose in the biomedicine sector, mainly for grafting and implants. In Chapter 14, the role of nanocellulose in dental applications is explained. In the last chapter of the book, Chapter 15, the future prospects of bacterial nanocellulose and its composites are outlined.
This book can be used in education, research, and industrial applications. It covers both general and advanced topics, and has been designed to be pedagogical so that even beginners can learn the fundamentals of nanocellulose.
We wish to express our gratitude to everyone involved in this project for their efforts, as well as Wiley and Scrivener Publishing for their cooperation and assistance in the publication of this book.
Mainak Mukhopadhyay and Debalina BhattacharyaNovember 2023
1Nanocellulose: A Cutting Edge Biopolymer – An Overview
Bidisha Saha and Mainak Mukhopadhyay*
Department of Bioscience, JIS University, Kolkata, West Bengal, India
Abstract
As the ever-increasing need for plastics and other polymeric materials, producing them ethically is an essential part of the business. Making it a sustainable and environmentally friendly industry is therefore critical. Filler for either a synthetic matrix or a natural starch matrix, cellulose presents a great chance to lessen the impact of non-biodegradable elements. Due to their excellent mechanical properties, biodegradability, biocompatibility, high specific surface area, and rich hydroxyl groups for extensive chemical modification, nanocelluloses have recently become increasingly popular as naturally derived, bio-based nanometer-sized reinforcement in a wide variety of technological areas. However, for its intrinsic hydrophilicity and difficulties in dispersion inside a hydrophobic matrix, the extraction of nanocellulose from cellulosic biomass and its dispersion in the matrix remain major hurdles. The literature provides a summary of recent advancements in nanocellulose research, including methods of extraction, surface modification, and polymeric composite applications. This chapter demonstrates how the source of the cellulosic materials and the processing factors affect the morphologies and performances of nanocellulose. Although nanocellulose is derived from organisms or plants that initially appear to be fragile, it can be used as a reinforcement material or the primary component to create high-value, cutting-edge products like high-performance nanocomposites, multifunctional hydrogels, conductive filaments, medical dressings, and energy storage materials. The development of high-performance nanocellulose-reinforced polymer composites is presented, along with research priorities and directions.
Keywords: Nanocellulose, natural biopolymer, nanocellulose-based nanocomposites, reinforced polymer composites, polymer, functionalization
1.1 Introduction
The use of biomasses for the preparation of polymer-based composites is expanding quickly in academia as well as industry due to the overuse and exhaustion of petroleum-based feedstocks as well as significant damage to the environment. Cellulose is being used for decades as a renewable energy source since it is the biomass resource with the highest availability. It is the main carbon source for the growing renewable sector that is creating functional composites [1–3]. It can be derived from numerous different sources including plants, fungi, and marine species, and because of its sustainability, non-toxicity, and biodegradable properties, it has a broad spectrum of applications in the creation of paper, coatings, cosmetics, and pharmaceutical industries. Cellulose is composed of glucose units connected by 1,4-glycosidic linkages. Many freely reactive hydroxyl groups are also present on the exterior of cellulose at the C2, C3, and C6 locations, which results in hydrogen bonding between the linear chains [4–6]. Cellulose is a perfect bio-filler for synthetic or natural polymers due to its excellent physicochemical, mechanical, and chemical characteristics. The inherent hydrophilicity, poor solubility, and infusible process ability of cellulose limit its employment in high-value-added domains, despite the fact that it is a good bio-filler with many beneficial features [7, 8].
In recent years, it has become increasingly difficult to obtain cellulose’s nanoscale structured components for use in the production of numerous valuable bio-compatible nanocomposite and commercialized cellulose compounds. In general, there are three different varieties of this cellulose-based nanostructured material, often known as nanocellulose: cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and bacterial nanocellulose (BNC) [9, 10]. This classification is based on the raw material, production process, and fiber morphology. However, there are still some significant challenges to the use of nanocellulose. Although there are numerous physical, chemical, and biosynthetic methods for producing nanocellulose, these processes remain dependent on intensive chemical processing, specialized equipment, or unorthodox raw materials. An economically feasible, efficient, and sustainable processing technology for nanocellulose is needed to decrease manufacturing expenses and prices. Polymeric composites with excellent biocompatibility and low toxicity can benefit from using nanocellulose as nanofiller for reinforcement. Though it has a propensity to clump easily because of its hydrophilicity which frequently leads to poor dispersion in the matrix and decreased performance of composites. Additionally, the keratinization that may happen as a result of nanocellulose drying could make it difficult to obtain dry nanoparticles or result in product flaws [11].
The goal of this chapter is to summarize the recent advances in the study of nanocellulose, provide a brief overview to the processes involved in its extraction and modification, and discuss its uses in polymeric composites, hydrogels, and filaments, as well as nanocellulose’s potential uses in biomedicine.
1.2 Nanocellulose: A Brief Overview
1.2.1 Structure and Source of Cellulose
A crystalline structure of cellulose known as primary fibrils is created when the newly produced cellobiose units are connected to one another. To create macro-fibrils, or cellulosic fibres, these latter are grouped together to make micro-fibrils. The unique characteristics of cellulose, such as chirality, ease of chemical functionalization, hydrophilicity, insolubility in most aqueous solvents, and infusibility, are due to its intra- and intermolecular chemical groups. Anhydroglucose units (AGUs), which make up the majority of cellulose, are repeated in the 4C1-chain structure with each monomer unit corkscrewed at an angle of 180 degrees with respect to its neighbours [12]. Evidently, cellulose is produced from wood and cotton, with respective polymerization degrees of 10,000 AGUs and 15,000 units, respectively. The degree of polymerization and the polymeric chain size imparts significant result on cellulose’s characteristics. Structured (crystalline) and unstructured (amorphous) regions both combine to form natural cellulose fiber. The crystallinity of the material can range from 40 to 70%, depending on the selection of extraction method. Compared to the crystalline sections, the amorphous regions are less packed and more likely to have interactions with adjacent molecular groups [13–15]. Depending on the molecular orientations, van der Waals, intra- and intermolecular interactions, isolation technique, and treatment procedure, cellulose exists in a variety of polymorphs, including cellulose I, II, III (I), III (II), IV (I), and V. These polymorphs can be interconverted by thermal or chemical treatments [16, 17]. Table 1.1 lists some of the sources of cellulose, including waste paper, wood, grass, herbaceous plants, agricultural crops, animal sources, algae, and bacterial sources. Figure 1.1 illustrates the evolution of cellulose from natural sources to fundamental molecules. Natural resource availability, origin and maturity, pretreatment and processing techniques, and reaction conditions can all affect the qualities of the cellulose that is produced [21–23]. In general, to remove non-cellulosic elements from bleaching, delignification, lignocellulosic sources, and the removal of extractive components (flavonoids, free sugars, fat, resin, tendon, terpenoids, tannins, terpenes, and waxes) are necessary [24, 25]. These pre-treatments can performed by a variety of chemical, physical, biological, and combined approaches [26–29]. They enable lignocellulose’s intractability to be overcome as well as its compact structure. More than 40% of the total processing cost goes towards pretreatments [30]. These pretreatments enable access to the cellulose fraction, disrupt the links between cellulose and non-cellulosic substances (lignin and hemicellulose), and permit the separation of pure and microcrystalline cellulose. Some pretreatments may have a negative impact on the process due to the creation of potentially hazardous wastes, ineffective separation, cellulose degradation and loss, as well as the high overall costs of the procedure. Numerous studies are still being done in order to improve the processes’ efficacy and effectiveness, lower their costs, and lessen their negative effects on the environment while also better understanding the phenomena that can arise during pretreatments. In order to get pure cellulose from animal cellulose, Trache et al. (2017) [18] claim that pretreatments are frequently required. Bacterial cellulose does not include extractives, hemicellulose, or lignin, in contrast to biomass-based cellulose; hence, pretreatments are not necessary. However, the price of producing it on an industrial scale is still quite high [31].
Table 1.1 Several sources for cellulose fibre synthesis [18–20].
Source
Example
Hardwood
Eucalyptus, Aspen, Balsa, Oak, Elm, Maple, Birch
Softwood
Pine, Juniper, Spruce, Hemlock, Yew, Larch, Cedar
Annual plants/Agricultural residues
Oil palm, Hemp, Jute, Agave, Sisal, Triticale straw, Soybean straw, Alfa, Kenaf, Coconut husk, Begasse, Corn leaf, Sunflower, Bamboo Canola, Wheat, Rice, Pineapple leaf and coir, Peanut shells, Potato peel, Tomato peel, Garlic straw residues, Mulberry fiber, Mengkuang leaves
Animal
Tunicates, Chordata, Styela clava, Halocynthia roretzi Drasche
Bacteria
Gluconacetobacter, Salmonella, Acetobacter, Azotobacter, Agrobacterium, Rhizobium, Alkaligenes, Aerobacter, Sarcina, Pseudomonas, Rhodobacter
Algae
Cladophora, Cystoseria myrica, Posidonia oceanica
Figure 1.1 The hierarchical structure of cellulose, which extends from the meter to the nanometer scale, is depicted in figure (a). The reaction between cellulose and strong acid to produce nanocellulose is depicted schematically in (b). (c) shows bio nanocellulose grown from cellulose-synthesizing bacteria.
1.2.2 Nomenclature and Types of Nanocellulose
From bionanocomposites to medicine to sensor and biosensing functions, nanotechnology is establishing itself as one of the key drivers of new industrial revolutions in a number of disciplines. Although cellulose has been thoroughly studied for many years, according to three popular databases, PubMed, Web of Science, and ProQuest, nanocellulose has only recently emerged as a significant and distinctive component. Some of the advantageous properties of this nanomaterial are its high surface-to-volume ratio, excellent modulus and tensile properties, low coefficient of thermal expansion, ability to establish hydrogen bonds, biocompatibility, sustainability, homogeneity, and lack of toxicity [32]. According to the literature, a number of terminologies have been used to define nanocellulose or cellulose nanoparticles, which unfortunately leads to misunderstandings and ambiguities [18, 33]. Establishing a standard nomenclature for the family of nanocelluloses is essential because there are still irregularities in the naming of nanocelluloses. Additionally, efforts must be made to rationalise the terminology used in relation to the morphology, size, and synthetic processes of the various compounds. A few years ago, a branch of the Technical Association of the Pulp and Paper Industry (TAPPI) was constituted with the goal of standardising the nomenclature of cellulose nanoparticles [34, 35]. But over the past few years, terms like “cellulose whiskers,” “cellulose nanowhiskers,” “cellulose nanocrystals,” and “nanocrystalline cellulose” have gradually merged into the jargon [36, 37].
There are essentially three different subtypes of nanocellulose: nanofibrillated cellulose (NFCs), nanocrystalline cellulose (NCCs), and bacterial nanocellulose (BNCs). A comparison of the three main varieties of nanocellulose is presented in Table 1.2. This nanocellulose can be created either top-down or bottom-up. Typically, top-down strategies such as enzymatic, chemical, or physical techniques are used to isolate and extract NCCs and NFCs from crops, higher plants, and by-products of forestry and agriculture such as banana stems, rice straws, pineapples, oil palm, rubber, lalang, and sugar palm fibres. Contrarily, bacterial nanocellulose (BNC) is created by a particular bacterial family (Glueconoacetobacker xylinius) and is grown as microfibrils in culture media using a bottom-up method [39].
1.3 Extraction of Nanocellulose
Cellulose can be extracted using an abundance of mineral acids. With diameters ranging from 10 to 200 micrometres [40] and an average diameter of roughly 44.28 [41] micrometres, the crystalline phase is nanometer-scale. Cellulose can also be isolated in nanocellulose form. Nanocellulose fibres typically have a diameter of less than 100 nm [42] and a length of several microns. Cellulosic and non-cellulosic components like lignin, hemicellulose, pectin, waxes, and other extracts make up natural plant fibres. Non-cellulosic material must be eliminated in order to extract cellulose as micro- or nano-extracts. In order to extract nanocellulose from cellulosic materials, various methods have been devised. Diverse means of extraction produced divergent nanocellulose with distinct attributes. According to the conditions of the extraction method, the size and aspect ratio of the crystalline area of the cellulose may differ significantly. The types, sizes, and forms of fibrils (micro- or nano-sized) are frequently impacted by this. It is typically non-isometric, though. This section divides the primary extraction methods into two categories: mechanical processes and chemical processes.
1.3.1 Mechanical Extraction
Homogenization under high pressure is an example of a mechanical extraction method. For mass manufacturing of nanocellulose, a piston is utilised to force the material through an extremely thin channel or orifice at high pressures of 50–2000 MPa [40]. This technique for isolating nanocellulose is eco-friendly [43]. However, this method can mechanically disrupt the crystal structure. Grinding is another mechanical method. Nanocellulose is separated from fibre through grinding, which involves spinning grindstones at a speed of about 1500 rpm to provide shear stress to the fibre [44]. Water evaporates as a result of the heat created by friction during the fibrillation process, which facilitates better extraction [45]. Additionally, cellulose fibre is extracted through crushing. In cold environments, this technique is used to create microcellulose [46]. The manufactured cellulose has a size range of 0.1 to 1 m. Prior to high-pressure homogenization, this procedure can be employed as a pretreatment to produce nanocellulose. The cellulose is extracted using another low-energy technology called steam explosion, which uses steam to explode. It might be regarded as a pretreatment even though lignin is not entirely removed. The resulting fibre needs mechanical adjustment after using this technique.
Table 1.2 Comparison between the different types of nanocellulose.
Characteristics
Bacterial nanocellulose (BNCs)
Nano fibrillated cellulose (NFCs)
Nano crystalline cellulose (NCCs)
Ref.
Common sources
Alcohols, low molecular weight sugar, and a number of bacterial species, including gluconacetobacter, agrobacterium, pseudomonas, rhizobium, and sarcin.
Pea hull, hardwood and softwood pulp, recycled pulp, acacia pulp, cotton linter, cotton, cassava bagasse, sugarcane baggase, wheat straw, mengkuang leaves.
Wood, cotton, rice straw, wheat straw, ramie, branchbark mulberry, black spruce and eucalyptus, tunicate, valonia, kraft wood, and spruce, palm oil, pineapple leaf fibre, rice husk.
[
38
,
39
]
Formation process
Bacterial synthesis and cultivation in medium containing phosphate, glucose, and oxygen in water.
Acid hydrolysis, enzymatic hydrolysis and mechanical shearing process integration by high pressure homogenization, and TEMPO-mediated oxidation.
Prior to delamination of wood pulp by mechanical pressure, acid hydrolysis, it may be treated chemically or enzymatically.
Morphology
Ribbon like
Rope like
Needle like
Crystallite
84-80%
59-64%
54-88%
Young’s modulus
78GPa
180 GPa
150 GPa
Size
20-100nm in diameter
5-60nm in diameter
5nm in diameter
Synonyms
Biocellulose,bacterial cellulose, microbial cellulose
Microfibrillated cellulose, nanofibrils, microfibrils, cellulose, nanofibre
Crystallites, whiskers, nanowhiskers, cellulose nanocrystals
1.3.2 Chemical Extraction
Alkaline roasting, acid roasting, chemical roasting, chemically assisted natural products (CAN), or degumming are all methods used in chemical extraction operations to remove the lignin component from the fibres. Pectin, hemicellulose, and other non-cellulosic materials are among the various elements of the fibre microstructure that are impacted by these treatments [47–50]. Alkali or acid retting is one application for the chemical extraction technique. Despite being less expensive, mechanical extraction causes less fibre damage [51]. The procedure is finished by heating, cleaning, and soaking the fibre in an alkaline or acidic solution. Using this technique may help improve several fibre properties [52]. Degumming, a chemical extraction technique designed to preserve the ramie fibre’s structural integrity, works by eliminating the sticky and pectin components [53]. Another chemical technique is chemical retting. The lignin and water content of fibres are reduced using this technique. Chemical retting is more effective at removing lignin than alkali or acid retting, although it is less effective at removing moisture. A combination of mechanical and chemical extraction methods can be utilised to ensure improved lignin removal efficacy, with mechanical extraction frequently taking place following chemical processing. The mechanical and chemical methods utilised to extract nanocellulose from lignocellulosic biomass are shown in Figure 1.2 [54].
Figure 1.2 Conversion of lignocellulosic biomass into nanocellulose.
1.4 Surface Modification and Functionalization for Nanocelluloses
While there are many benefits to using nanocellulose in polymeric composites, its application is severely limited by a number of serious drawbacks. Low heat stability, moisture absorption, incompatibility with hydrophobic polymers, and poor redispersion are some of these shortcomings. Because of its large surface area, many hydroxyl groups (OH), and strong intra- and intermolecular hydrogen interactions between the hydroxy groups, nanocellulose has a hydrophilic surface and exhibits intense self-aggregation. As a consequence, like the majority of conventional non-polar polymers, it is difficult to distribute nanocellulose uniformly. It should be noted that the samples’ poor thermal and dimensional stability may be brought on by the reactive groups on the outward of the nanocellulose. From a different perspective, the many reactive groups on the exterior of nanocellulose provide a variety of potential routes for the chosen alterations, which principally aim to decrease aggregation formation and polarity variances in nanoparticles. Nanocellulose’s compatibility, dispersibility, and other qualities can be improved through surface modifications,which in turn opens up the possibilities to a wide range of high-value usage. Nanocellulose endures two main kinds of changes: structural changes that affect how it’s organised, and functional changes that affect how its hydroxyl groups operates in. Nanocellulose’s surface is often chemically modified to create a covalent link with reactive groups through procedures like silylation, esterification, oxidation, amination, carboxymethylation, sulfonation, polymer grafting, and others [55–59].
1.4.1 Esterification
The esterification reaction is the most prevalent within nanocellulose, and it is the most widely recognised and essential way to reduce the hydroxyl density of nanocellulose. The primary action of acetylation is to replace the hydroxyl groups on nanocellulose with acetyl groups. Typically, the condensation of a carboxylic acid group (COOH) with an alcohol group (OH) results in the introduction of an ester group. When using dilute sulfuric or perchloric acid as a catalyst, typical methods of production require for acid anhydrides or acyl chlorides as acyl donors. It could be done to confirm that the alcohol group of CNC reacts well with the acid anhydride by substituting it with chains of various lengths in the presence of H2SO4. By forming acetyl groups, the acetylation of nanocellulose lowers the hydroxyl density and minimises water absorption [60]. As a result, acetylated nanocellulose has less hydrolytic breakdown and better thermal stability [61]. Esterification, by which the wood-derived CNFs are modified with four different esters (acetyl, benzoyl, myristoyl, and pivaloyl), was discovered by Agustin et al. [62] to have the potential to significantly increase the nanofibers’ thermal stability. The highly esterified amorphous regions of the nanocellulose are likely to blame for this.
1.4.2 Silylation
Alkoxysilanes or polysiloxanes interact with the hydroxyl groups of nanocellulose in silylation, a technique for altering surfaces. Hexamethyldisilazane (HDMS) [63], 3-aminopropyltriethoxysilane (APTES) [64], trichloromethylsilane (TC) [65, 66], and 3-methacryloxypropyltrimethoxysilane (MPS) [67] are some of the silane derivatives that have been used to make unique silylated nanocellulose. In general, there are several significant steps involved in the silylation of nanocellulose. The unique silylated surface of nanocellulose is produced via covalent bonding, when silane is first hydrolyzed in an aqueous solution to yield silanol, which may then be adsorbed on the surface of nanocellulose. One example of an alkylation modification that can successfully increase the dispersibility of nanocellulose and improve the interfacial contact with the hydrophobic matrix is tetrahydrofuran (THF), an organic solvent with low polarity. The degree of alkylation on the surface of the nanocellulose is directly correlated with the amount of silane present in the reaction. Extensive surface substitution will damage the crystalline regions of nanofibers, decreasing the strength of the nanocellulose. The optimal approach strikes a balance between a certain amount of silylation and the maintenance of nanocellulose structure. The silylation process commonly uses a variety of silylating compounds and reaction conditions to get around this challenge. Goussé et al. [68] changed CNCs and CNFs by silylating them using a range of chlorosilanes. They found that a moderate silylation protocol that needed fewer reagents and quicker reaction times resulted in the modified CNCs and CNFs being dispersible in a variety of low-polarity organic solvents and that their morphological integrity had been effectively preserved. The silylated nanocelluloses are employed in a greater variety of biomaterials, coatings, food packaging, optical devices, and polymer reinforcement because of their improved compatibility, hydrophobicity, mechanical strength and thermal stability [58, 69].
1.4.3 Amidation
The most widely used technique for surface modification is amidation, which generates modified nanocellulose with improved surface conductivity and hydrophobicity [70, 71]. An amine and carboxylic moiety reaction can produce the amide bond. Because there are not any carboxy groups on the surface of nanocellulose in general, the carboxy groups are also added through pre-oxidized treatment, such as TEMPO-mediated oxidation [72]. It is possible to combine metal ions or alkylammonium ions to produce nanocellulose with a range of functionalities by employing these carboxylate groups as a powerful platform.
1.4.4 Sulfonation
Sulfonation-esterification can further carry an anionic surface charge Nanocellulose surface. The hydroxyl groups on the surface of the nanocellulose are spontaneously substituted with hydrogens during the hydrolysis of sulfuric acid to produce sulphate half-esters. By preventing the formation of hydrogen bonds by electrostatic repulsion, the sulphate esters on the surface of CNCs or CNFs enable the development of colloidally stable suspensions. Nanocellulose can have carboxymethyl groups added using carboxymethylation to generate an ionic surface, which often leaves the surface negatively charged [73].
1.5 Applications of Nanocellulose in Polymeric Composites
1.5.1 Nanocellulose-Reinforced Polymer Nanocomposites
With synthetic polymer that exhibits distinct chemical and physical properties, nanocellulose can be reinforced [74]. Following that, mixtures of polymer and nanocellulose begin to synthesize materials with totally unique properties yet with relatively approachable qualities from different components. This circumstance is known as a nanocomposite. Polymers have lower modulus and tensile strength as compared to metals and ceramics. PNCs can be determine by
Polymer Matrix - Rg (Polymer radius of gyration),
The Nanoparticle - 2r (Diameter of nanospheres and nanotubes or thickness of nanoplates),
The Composite Morphology - 2ξ (Mean distance between constituents) [75].
This similar (Rg ∼ r ∼ ξ) correlation illustrates a geometrical factor that influences established conceptions of polymer dynamics. In numerous industries, including food packaging, energy and safety, transportation, electromagnetic shielding, military systems, sensors, catalysis, and the information business, polymer nanocomposite generated from both natural and petrochemical resources is used. The biodegradability agents, simple processing, bioabsorbability, minimal cost convincingness, non-abrasive texture, non-toxic, low density, and flammability of nanocellulose-polymer based composites make them advantageous. As a replacement for thermosets and thermoplastics like polypropylene, polystyrene, and high density polyethylene, nanocellulose is a remarkable endeavour. For more reinforcing capability, a higher aspect ratio is necessary. To improve the characteristics of the polymer with a 6% loading volume rate, nanocellulose whiskers or microcrystals derived from tunicate are utilised to enhance styrene and butyl acrylate copolymer latex. When nanocellulose is loaded at such a low rate, it often yields a promising, satisfying outcome that the resulting nanocomposite possessed mechanical properties that were notably better than those of the pure polymer in its elastomeric mode.The bio-based polymers polylactic acid (PLA), polyhydroxy acids (PHA), polyhydroxy butyrate (PHB), polybutylene succinate (PBS), and starch biopolymer are all reinforced by nanocellulose.Direct addition of nanofillers, in situ synthesis, as well as additional methods including electrospinning, self-assembly, phase separation, and template synthesis, can all be used to start creating polymer nanocomposites. Some microscopy techniques to determine polymer nanocomposites are mentioned in Table 1.3.
1.5.1.1 Dispersion of Nanocellulose in the Matrix
(Here polypropylene (PP) and polyethylene (PE) are used as matrix)
Due to their potential to be readily ingested by soil-dwelling microbes and the composite produced by the mixing of matrices and the host component, which results in chains of fragmented polymers with a larger surface area, which can be easily disposed of because they are natural fiber fillers that ultimately decompose into carbon dioxide and water. Polymers made from petroleum, such as polypropylene (PP) and polyethylene (PE), are toxic and non-biodegradable. By increasing the concentration of these natural fillers in the matrix, biodegradability may be expedited, although heavier materials may slow down the process. At the junction of their interactions, nanofiller with a large surface area and small internal load can provide an appropriate dispersion [76]. The load of concentration and rate of dispersion can have an impact on nanocomposites. Insoluble in water polymers may prevent a composite from developing fully during processing. Water soluble polymers can be used to achieve prominent dispersion. The hydrogen bonding between nanocellulose and a water molecule through hydroxyl groups on its surface has been used to detect intercourse activity. Acrylic monomer and ethylene-acrylic oligomer emulsion can encourage the dispersion in the resultant composite, and hydrophobization can reduce the interaction between hydroxyl groups. Solvent casting, melt processing, batch processing, and other processes can be used to develop nanocomposites.However, substantial tensile strength has been subjected to a range of about 70-80%, which is in advantage of future reinforcing potential of nanocellulose composites with matrices.
1.5.1.2 Mechanical Performance of Resulting Nanocomposite [76]
The physiochemical performance can be improved with nanofillers. The stiffness and ductility of a nanocomposite have been mentioned, which ultimately help to enhance the mechanical performance of the composite. As mentioned by their loading capacity, reinforcing elements can act as a stress transfer medium, affecting the crack formation which heading towards inhibitory path by stress absorption. The presence of nanocellulose within the polymer matrix caused it to consume the stresses therein. It may occur at any intersection.
Table 1.3 Detection of polymer nanocomposites through microscopy techniques.
SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy)
Examine the internal and external features of the material
WAXED (Wide Angle X-ray Diffraction)
The most ideal and easiest tool for nanocomposite structure determination
SAXS (Small Angle X-ray Diffraction)
Used to determine the structure of polymer composite by matching the contrast or combination of two probes
SPM (Scanning Probe Microscopy)
The small tip of microscope interacts with surface leading material for an image formation
STM (Scanning Tunneling Microscope)
A small sharp tip is settled down of about 0.5nm away from the surface material which can underpass from the tip to the surface material on atomic level
AFM (Atomic Force Microscopy)
Screening of the surface material can happen along with the scanning to ultimately examine its surface features and ruggedness
DSC (Differential Scanning Calorimetry) and DMA (Dynamic Modulus Analyzer)
Both these techniques plays an important role in determination thermal properties of nanocomposites
TGA (Thermo Gravimetric Analyzer)
This tool used to investigate wide variety of polymer properties, thermal stability and polymer improvement has been reported by TGA
TMA (Thermo Mechanical Analyzer)
Measure the co-efficient of thermal expansion (CTE) of nanocomposites
FTIR (Fourier Transform Infrared Spectroscopy)
Analyse the chemical characteristics of Raman spectroscopy using nanocomposites
Some Combinations are following which shows a better reinforcing performance;
Poly(e-caprolactone) or (PCL) and cellulose nanocrystals or (CNCs) resulting nanocomposite give better performance as a reinforcing element which can be achieved through surface modification and better tensile strength.
Cellulose nanofibrils or (CNFs) and polylactic acid or (PLA) result a better reinforcing nanocomposite through esterification modification can give better tensile strength and higher hydrophobicity.
Sugar palm crystalline nanocellulose or (SPCNC) reinforced thermoplastic sugar palm starch or (TPS)/polylactic acid or (PLA) blend nanocomposite by melt blending process from solution casting indicate a better dispersed at polylactic acid phase through sonication in advance of starch gelatinization.
Polylactic acid or (PLA)/polyethylene glycol or (PEG)/lignocellulosic nanofibers or (LCNF) nanocomposites by melt processing resulted in stronger toughness. (LCNFs) used to reinforce (PEG)-plasticized (PLA).
A polymer matrix’s quality of the reinforcing element is dictated by the dispersion level. Whiskers and other additives can improve in the creation of composite materials with improved mechanical properties, but excessive bonding can reduce the strength of the nanocomposite at the point of breakdown.
1.5.2 Nanocellulose-Based Hydrogels
On the whole, hydrogels are hydrophilic gels made of crosslinked polymers that have swelled because of the presence of water. The hydrogels’ functional groups, such as -NH, -OH, -COOH, and -CONH, among others, enable the retention of a significant quantity of water without becoming dissolved in it. Due to their high-water content, hydrogels are naturally flexible. Because water fills the spaces between macromolecules in hydrogels created by the crosslinking of two or more components, they can swell and hold onto large amounts of water without losing their three-dimensional form. Hydrogels offer a wide range of applications in treatments, drug administration, and particularly in tissue engineering because of their mechanical qualities. Although cellulose-derived materials are environmentally beneficial and hydrogel production is relatively inexpensive, nature may be trusted. The biomedical industry has took note of hydrogels derived from CNCs, CNFs, BNCs due to their greater surface area, improved mechanical strength, variable surface chemistry, amazing biocompatibility, target specific cellular recognition, and biodegradability. In comparison to synthetic superabsorbent hydrogels, cellulose-based superabsorbent hydrogels perform better in terms of absorbance, strength, biodegradability, biocompatibility, and good salt resistance. Nanocellulose-based hydrogels, specific high-quality materials for electronic and sensonic applications, cellulose-based diagnostic chips for biomedical applications, and 3D printing, among others, are all employed in the manufacture of pharmaceutical items and packaging [77]. The performance of printability can be improved by the addition of biopolymers. The swelling ability of hydrogels can be improved by using smart hydrogels that respond to stimuli and are based on a nanocellulose component. In comparison to chemically treated hydrogels, nanocomposite hydrogels exhibit higher viscosity.
Numerous laboratories worldwide are developing hydrogels based on nanocellulose. However, a standardised approach is needed to assess these hydrogels. It becomes challenging to compare the various mechanical properties of hydrogels developed by different labs without a common method to define them.
1.5.3 Nanocellulose-Based Filaments
These primarily fiber-based cellulosic components are created by connecting nanocellulose to its axial direction to make a structure that is continuous and thread-like. Technical techniques can be used to create nanocellulose-based filaments, including electrospinning, wet spinning, melt spinning, dry spinning, microfluidics, and flow focusing, with the solution spinning technique being the most widely used (wet and dry spinning). Interfacial polyelectrolyte complexation, or IPTC, has recently been introduced in the field of spinning techniques. This IPTC spinning approach has been used to fabricate the self-assembled filaments that are specifically derived from nanocellulose at the interface of two oppositely charged polyelectrolytes complex (+ve/-ve). Conductive filaments, antibacterial filaments, and hydrogel threads are some of the major functionally active nanocellulose-based filaments. Nanofilaments can alter their surface electronegativity and charge density properties by altering their surface. Additionally, researchers are also producing nanocellulose fibres using a PVA or poly (vinyl alcohol) mixture. It contributes to a homogenous mixture due to its hydrophilic character. Some boundaries that maintains the resulting filaments quality is -
The optimum spinning conditions
Low solids content in dope
High shear rate in spinneret
High nanocellulose aspect ratio and
High draw ratio.
Together, these factors can help the filament become more orientated and aligned with the axis, which improves the filaments’ internal properties. Draw ratio, which affects the final filament alignments and is a key component of filament drawing, is the ratio of the spinneret’s flow velocity to filament take-up velocity. For this orientation, a draw ratio of approximately >1 is suitable.
1.5.4 Nanocellulose for Biomedical Application
In the biomedical field, nanocellulose has lately been referred to as the “eyes of biomaterial” and has many uses, such as skin substitutes for burns and wounds, drug release mechanisms, blood vessel growth, nerve, gum and dura reconstruction, tissue engineering scaffolds, stent covering and bone reconstruction.
Tissue engineering explores for novel elements and technologies that might interact well with biological tissues, either by rearranging and creating tissue that will soon be transplanted or by acting as an in vitro basis for cell proliferation. Additionally, they target new classes of biocompatible, controlled, and particular degradable biopolymers that are more likely to be used as in vitro tissue reconstruction or as cell scaffolds.
As previously mentioned, a wide range of biomaterials have lately been produced. The eventual application—tissue regeneration, tissue grafting, or scaffolding, drug holding and release—largely determines their chemical, physical, and mechanical characteristics. The success of the scaffold is heavily dependent on the growth and attachment of cells to the surface, therefore the chemical surface of the biopolymer can control biological response by obstructing cellular adhesion, proliferation, migration, and functioning.
On the other hand, three distinct foundations are used to regenerate tissues: cells, support, and growth factors. Cells create the milieu for new tissues, hold and maintain the ideal environment for growth, while growth factors stimulate and encourage cell regeneration. The material used for implants needs to be biocompatible and cannot cause inflammation or rejection in some people. It should also encourage regeneration and, if necessary, be biodegradable or absorbed over time. For implants to be successful, research on support-cell interactions is essential. The ability of the cell to distinguish between various reactions from various materials and adjust accordingly determines whether the cell will adhere to the surface or not. This is important since it will influence subsequent reactions including cell viability, migration, and proliferation [78].
A biological membrane created by Barud uses bacterial cellulose and a standardized propolis extract. Numerous biological characteristics of propolis include its ability to combat infection and reduce inflammation. The membrane has make it an effective treatment for burns and open wounds.
The use of nanocellulose-based materials for biomedical purposes has produced some intriguingly encouraging results and accomplishments, but more research on the long-term biocompatibility and toxicology should be done in addition to the implementation of the validation of these nanocellulose-based biomaterials using the standards and methodologies used by the competent authorities.
1.6 Summary and Prospects
In various domains, nanocellulose strengthened polymer composites have been researched. These studies all aim to design functional materials with high performance and high added value by utilizing the benefits of nanocellulose, including its lightweight, high strength, low cost, and renewable sources, despite the fact that their study foci, methodologies, and findings differ. Although nanocellulose have significant performance benefits, there are still challenges to their commercialization and industrialization, and some uncharted territory needs to be further investigated.
1.6.1 Advantages of Nanocellulose-Reinforced Polymer Composites
Since Hermann Staudinger developed polymer science, the modification of polymers has been explored, and the field will continue to grow as long as there is a need for high-performance materials. Due to the vast potential for commercialization, scientists have made significant advances in their study of nanocellulose reinforced polymer composites. Nanofiller-reinforced polymers have a higher competitive edge than more conventional methods of modification like blending because they can increase material strength without significantly diminishing or even improving toughness.
Nanocellulose is great nanofiller because of its small particle size, high specific surface area, high modulus, high strength, and ease of modification. Natural biomass is abundant, biodegradable, nontoxic, biocompatible, and environmentally benign; nonetheless, its utilisation depends on the efficiency with which the existing high-pollution, energy-intensive processing procedures may be improved. For these reasons, nanocellulose is a game-changing material in fields as diverse as biodegradable plastics, bioscaffolds, catalysts, and drug carriers.
1.6.2 Current Challenges
Nanocellulose reinforced polymer composites having a number of uses and development prospects. Functionalization and mass production are two issues that must be resolved in order to advance its industrial use as well as utilization.
1.6.2.1 Functionalization
The dispersion of nanocellulose and its fusion with the matrix are significantly impacted by the intrinsic compatibility issue that exists between hydrophilic nanocellulose and the preponderance of hydrophobic polymer matrices. The majority of the research advancements stated above and listed in the preceding article included altering nanocellulose, but one of the goals was really to increase interfacial compatibility. A more varied composite design and improved performance are both possible with modified nanocellulose. This presents both a chance and a difficulty. The surface characteristics of nanocellulose make for a variety of modifications. Not only the modification’s intended use must be taken into account, but also how the modification will affect nanocellulose’s crystalline structure, surface microstructure, particle morphology, and physical and chemical properties, as well as how these changes will affect the performance of the finished composite. Numerous investigations have additionally demonstrated that the synergistic interaction between nanocellulose and other nanofillers leads to more complex effects. It is necessary to build a multiphase model in order to functionalize techniques that are distinct from the two-phase system of nanocellulose and uniform matrix. This is challenging since the reinforcement processes have not yet been fully understood and require more research.
1.6.2.2 Mass Production
The production cost must be reduced in order to achieve mass production. Nanocellulose takes more to produce and has a lower production capacity than other typical nanofillers like nano montmorillonite and nano silica, which generates higher its cost. Additionally, before combining with the polymer, modification or other pretreatment is frequently required, raising the expense of producing the nanocellulose-reinforced polymer and impeding the commercialization of existing nanocellulose reinforced polymer composites. This is the primary issue impeding mass production. The largest issue facing mass production applications is optimizing the process to lower production costs and improve production capacity to accomplish batch production.
1.6.3 Conclusion and Future Developments
In conclusion, functionalization and mass production are the two development paths for nanocellulose reinforced polymer composites, and they fundamentally address the requirement for better, stronger, more affordable, and more varied materials. The tremendous potential of the sector is really reflected in many of the existing challenges. A small amount of innovation, regardless of theory, technique, or application, can propel an entire sector towards a significant milestone. Engineering plastics, functional films, bioscaffolds, catalysts, drug carriers, adsorption materials, and flexible electronic components are among the many applications being researched for nanocellulose reinforced polymer composites. Nanocellulose reinforced polymer composites are anticipated to surpass all other composite materials in value as a result of current research.
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