Preface xvii Part 1: Fundamental Aspects 1 1 Introduction to Naturally-Based (Bio-) Adhesives 3 Manfred Dunky 1.1 Introduction 3 1.2 Overview and Challenges For Adhesives Based on Natural Resources 6 1.2.1 Combined Use of Synthetic and Naturally-Based Adhesives 8 1.2.2 Overview on Adhesives Based on Natural Resources 9 1.2.3 Requirements, Limitations, and Opportunities for Wood Adhesives Based on Natural Resources 11 1.3 Biorefinery and Platform Chemicals 11 1.4 Lignin as Raw Material for Platform Chemicals 20 1.5 5-Hydroxymethylfurfural (5-HMF) as Platform Chemical 23 1.6 Mimicking Nature 27 1.7 Special Topics and Latest Developments 29 1.8 Prospects 30 1.9 Summary 30 General Literature on Biobased Adhesives 30 List of Abbreviations 34 References 35 2 Adhesion Theories in Naturally-Based Bonding: Adhesion and Surface Issues with Naturally-Based Adhesives 45 Douglas J. Gardner, Geeta Pokhrel and Alexander Collins 2.1 Introduction 45 2.2 Adhesion Theories 46 2.2.1 Mechanical Interlocking 47 2.2.2 Electrostatic Mechanism 48 2.2.3 Adsorption (Thermodynamic) or Wetting Mechanism 49 2.2.4 Diffusion Mechanism 50 2.2.5 Chemical (Covalent) Bonding Mechanism 50 2.2.5.1 Hydrogen Bonding 51 2.2.6 Acid-Base Theory 51 2.2.7 Weak Boundary Layers 52 2.2.8 Stickiness or Tackiness 53 2.3 Protein Adhesives 54 2.3.1 Animal-Sourced Proteins 55 2.3.2 Plant Proteins 57 2.4 Carbohydrate-Based Adhesives 59 2.5 Plant or Wood-Based Extractives 60 2.5.1 Rubber 60 2.5.2 Resins 61 2.5.2.1 Rosin 62 2.5.2.2 Terpene Resins 63 2.5.2.3 Tannins 64 2.5.2.4 Gums 65 2.6 Fats or Oils 66 2.6.1 Tung Oil 67 2.6.2 Linseed Oil 68 2.6.3 Soybean Oil 69 2.6.4 Castor Oil 70 2.6.5 Miscellaneous Oils 71 2.7 Summary 72 Acknowledgements 72 List of Abbreviations 72 References 74 3 The Chemistry of Bioadhesives 85 A. Pizzi 3.1 Introduction 85 3.2 Carbohydrate Bioadhesives 86 3.3 Protein Bioadhesives 91 3.4 Lignin-Based Bioadhesives 93 3.5 Tannin-Based Bioadhesives 95 3.5.1 Hydrolysable Tannins 96 3.5.1.1 Gallo-Tannins 96 3.5.1.2 Ellagi-Tannins 96 3.5.2 Condensed Polyflavonoid Tannins 96 3.5.3 Reactions of Condensed Flavonoid Tannins 99 3.6 Other Bio-Adhesives for Wood Composites 106 3.7 Summary 108 List of Abbreviations 109 References 110 4 Biorefinery Products as Naturally-Based Key Raw Materials for Adhesives 119 Johannes Karl Fink 4.1 Biorefinery Systems 119 4.1.1 History of Biomaterials 119 4.1.2 Classification of Biorefinery Systems 120 4.1.3 Biorefinery Processes 123 4.1.3.1 Hydrothermal Processes 123 4.1.3.2 Thermochemical Processes 123 4.1.3.3 Chemical Processes 124 4.1.3.4 Biochemical Processes 124 4.1.3.5 Bacterial Processes 124 4.1.4 Renewable Materials for Biorefinery 126 4.1.4.1 Carbohydrates 126 4.1.4.2 Lignin 126 4.1.4.3 Triglycerides 127 4.1.4.4 Mixed Organic Residues 127 4.2 Biobased Materials 128 4.2.1 Biobased Monomers 128 4.2.2 Synthesis Methods 129 4.2.2.1 L-3,4-Dihydroxyphenylalanine 135 4.2.2.2 2-Pyrone-4,6-dicarboxylic acid 136 4.3 Biobased Materials Suitable for Adhesives 137 4.3.1 Additives 137 4.3.2 Wood Adhesives 138 4.3.3 Lignin-Based Adhesives 139 4.3.4 Biorefinery Process of Kash 139 4.3.5 Lignin-Phenol Adhesives 140 4.3.5.1 Enzymatic Hydrolysis of Lignin 141 4.3.5.2 Biorefinery Residues 142 4.3.5.3 Phenol Replacement by Lignins 142 4.3.6 Lignin-Epoxy Adhesives 143 4.3.7 Lignosulfonates 145 4.3.8 Tannins 145 4.3.9 Protein-Based Adhesives 146 4.4 Synthesis Methods for Biobased Adhesives 147 4.4.1 Methylolated Wood-Derived Bio-Oil 147 4.4.2 Biosynthesis of Lignin 148 4.4.3 Soy-Based Adhesives 149 4.4.4 Bisphenol A-Glycidyl Methacrylate Replacement 149 4.5 Modification of Lignin for Better Performance 150 4.5.1 Functionalization with Aromatic Compounds 152 4.5.1.1 Functionalization of Lignin 153 4.5.1.2 Phenolation of Lignin 154 4.5.2 Organosolv Lignin-Based Materials 155 4.6 Pressure-Sensitive Adhesives 155 4.6.1 Lignin as Filler 156 4.6.2 Biobased Acrylic Compounds 156 4.6.3 UV-Tunable Pressure-Sensitive Adhesives 157 4.7 Summary 158 References 158 5 Natural Aldehyde-Based Thermosetting Resins 167 Manfred Dunky 5.1 Introduction 167 5.2 Aliphatic Aldehydes 168 5.2.1 Acetaldehyde 168 5.2.2 Glyoxal 169 5.2.2.1 Glyoxalation of Lignin 171 5.2.2.2 Glyoxylic Acid and Glyoxal 176 5.2.2.3 Glyoxal and Glutaraldehyde 176 5.2.2.4 Glyoxal and 5-Hydroxymethylfurfural (5-HMF) 177 5.2.3 Dimethoxy-Ethanal (Dimethoxy-Acetaldehyde, DME) 177 5.2.4 Propanal (Propionaldehyde) 178 5.2.5 Butyraldehyde 178 5.2.6 Isobutyraldehyde (Isobutanal) 179 5.2.7 Succinaldehyde (Butandial) 179 5.2.8 Glutar(di)aldehyde (GA) (Pentandial) 180 5.3 Aldehydes Based on Cyclic Structures 180 5.3.1 Furfural (Furfurylaldehyde) 180 5.3.2 Furfuryl Alcohol (FA) 184 5.3.3 5-Hydroxymethylfurfural (5-HMF) (see also Chapters 1 and 17) 185 5.3.4 2,5-Diformylfuran (2,5-Furan-Dicarbaldehyde) 192 5.3.5 Aromatic Aldehyde Precursors 193 5.3.6 Polymers with Pendent Aldehyde Groups 194 5.4 Summary 195 List of Abbreviations 195 References 198 6 Natural Crosslinkers for Naturally-Based Adhesives 207 Manfred Dunky 6.1 Introduction 207 6.2 Crosslinking Reactions 208 6.2.1 Proteins 208 6.2.2 Tannins 211 6.2.3 Carbohydrates 214 6.2.4 Lignins 217 6.3 Aliphatic Aldehydes as Crosslinkers 219 6.3.1 Formaldehyde 219 6.3.2 Higher Aldehydes 221 6.3.3 Glyoxal 221 6.3.4 Glutaraldehyde 223 6.3.5 Higher Aliphatic Aldehydes 226 6.4 Cyclic and Aromatic Aldehydes as Crosslinkers 226 6.4.1 Furfural 226 6.4.2 5-Hydroxymethylfurfural (5-HMF) 228 6.4.3 Non-Volatile Aldehydes from Carbohydrates 230 6.5 Crosslinkers Prepared from Biomass 231 6.5.1 Furfuryl Alcohol 231 6.5.2 Extracts as Crosslinkers 234 6.5.3 Glycerol Diglycidyl Ether (GDE), Glycerol Polyglycidyl Ether (GPE), and Ethylene Glycol Diglycidyl Ether (EGDE) 234 6.5.4 Triglycidylamine (TGA) 236 6.5.5 Diethylene-Triamine (DETA) 237 6.5.6 Citric Acid 237 6.6 Synthetic Crosslinkers 240 6.6.1 Polyamidoamine–Epichlorohydrin (PAE) Resins 240 6.6.2 Epoxy Resins 241 6.6.3 Polyethylenimine (PEI) 242 6.6.4 Polyamidoamine (PADA) 243 List of Abbreviations 243 References 245 7 Curing and Adhesive Bond Strength Development in Naturally-Based Adhesives 255 Milan Šernek and Jure Žigon 7.1 Introduction 255 7.2 Curing Monitoring Techniques 256 7.2.1 Gel Time Test 256 7.2.2 Differential Scanning Calorimetry (DSC) 257 7.2.3 Thermogravimetric Analysis (TGA) 258 7.2.4 Dielectric Analysis (DEA) 259 7.3 Bond Strength Development Monitoring Techniques 260 7.3.1 Dynamic Mechanical Analysis (DMA) 260 7.3.2 Thermomechanical Analysis (TMA) 261 7.3.3 Automated Bonding Evaluation System (ABES) 262 7.3.4 Tensile-Shear Strength 263 7.4 Curing Mechanisms in Naturally-Based Adhesives 263 7.4.1 Tannin-Based Adhesives 263 7.4.2 Lignin-Based Adhesives 265 7.4.3 Soy-Based Adhesives 267 7.4.4 Sucrose-Based Adhesives 269 7.4.5 Starch-Based Adhesives 270 7.4.6 Liquefied Wood (LW)-Based Adhesives 271 7.5 Summary 272 Acknowledgements 273 List of Abbreviations 273 References 274 8 Mimicking Nature: Bio-Inspired Adhesives 279 Manfred Dunky 8.1 Introduction 279 8.2 Improvement of Adhesive Performance 282 8.3 Underwater Adhesives (Wet Application Adhesives) 286 8.4 Detechable Bonding and Self-Healing Polymers 289 8.5 Medical Applications 292 8.6 Summary 294 List of Abbreviations 294 References 295 Part 2: Classes of Biobased Adhesives 305 9 Protein Adhesives – Composition, Structure and Performance 307 Charles R. Frihart 9.1 Introduction 307 9.2 Composition of Proteins 308 9.3 Types, Sources, Processing, and Properties of Proteins 309 9.3.1 Collagen (Animal) 309 9.3.2 Globular (Plant) 311 9.3.3 Globular (Milk) 315 9.3.4 Globular (Egg) 316 9.3.5 Globular (Blood) 317 9.3.6 Other Protein Sources 317 9.4 Conclusion (Future of Protein Adhesives) and Summary 317 List of Abbreviations 318 References 319 10 Carbohydrates (Polysaccharides) as Adhesives 325 Lee Seng Hua and Lum Wei Chen 10.1 Introduction 325 10.2 Cellulose Derivatives 326 10.3 Starch-Based Adhesives 330 10.4 Dextrin 331 10.5 Natural Gums 333 10.6 Chitosan 335 10.7 Summary and Prospects 339 Acknowledgements 340 List of Abbreviations 340 References 341 11 Natural Polymer-Based Adhesives 345 A.A. Shybi, Siby Varghese, Hanna J. Maria and Sabu Thomas 11.1 Introduction 345 11.2 Natural Rubber (NR)-Based Adhesives 346 11.2.1 Introduction to NR-Based Adhesives 346 11.2.2 NR-Based Wood Adhesives 350 11.2.3 NR-Based Pressure-Sensitive Adhesives 352 11.2.4 NR-Based Adhesives in Leather, Rubber, Textile and Metal Bonding Applications 353 11.3 Poly(lactic acid) (PLA)-Based Wood Adhesives 354 11.3.1 Introduction to PLA-Based Adhesives 354 11.3.2 PLA-Based Wood Adhesives 355 11.3.3 PLA-Based Hot-Melt Adhesives 356 11.3.4 PLA-Based Adhesives for Metal Bonding 357 11.4 Chitosan-Based Adhesives 357 11.4.1 Introduction to Chitosan-Based Adhesives 357 11.4.2 Chitosan-Based Wood Adhesives 358 11.5 Summary 359 List of Abbreviations 360 References 361 12 Epoxy Adhesives from Natural Materials 367 Charles R. Frihart 12.1 Introduction and Morphology 367 12.2 Basic Properties of Epoxies 369 12.3 Epoxy Synthesis 370 12.4 Epoxy Curing 373 12.4.1 One-Component Epoxies 375 12.4.2 Two-Component Epoxies 376 12.5 Aromatic Epoxies 376 12.5.1 Aromatic Bis-Phenol Epoxies 376 12.5.2 Aromatic Novolac Epoxies 377 12.5.3 Biobased Aromatic Epoxies from Polyphenols, Tannins, Cardanol, and Lignin 378 12.5.4 Aromatic Epoxies from Lignin and Woody Biomass 378 12.6 Aliphatic Epoxies 379 12.6.1 Aliphatic Epoxies from Vegetable Oils 380 12.6.2 Aliphatic Epoxies from Sugars 381 12.6.3 Aliphatic Epoxies from Terpenoids 382 12.6.4 Other Aliphatic Epoxies 382 12.7 Hardeners 383 12.7.1 Amines 383 12.7.1.1 Aliphatic Amines 383 12.7.1.2 Biobased Aliphatic Amines 384 12.7.1.3 Aromatic Amines 385 12.7.2 Anhydrides of Organic Acids 386 12.8 Other Curing Mechanisms 386 12.9 Other Additives 386 12.9.1 Tougheners 386 12.9.2 Modifiers 387 12.10 Status of Biobased Epoxy Adhesives 387 12.11 Summary 388 List of Abbreviations 389 References 389 13 Naturally-Based Polyurethane Bioadhesives 395 A. Pizzi 13.1 Introduction 395 13.2 Biopolyols-Isocyanate Polyurethanes 396 13.3 Non-Isocyanate Polyurethanes (NIPUs) 399 13.4 NIPUs as Adhesives 402 13.5 Summary 408 References 408 14 Nanocellulose-Modified Wood Adhesives 415 Stefan Veigel, Stefan Pinkl and Wolfgang Gindl-Altmutter 14.1 Introduction 415 14.2 Nanocellulose as Additive for Conventional and Biobased Wood Adhesives 416 14.3 Nanocellulose-Derived Wood Adhesives 420 14.4 Prospects 421 14.5 Summary 421 Note 422 List of Abbreviations 422 References 423 15 Debondable, Recyclable and/or Biodegradable Naturally-Based Adhesives 427 Natanel Jarach and Hanna Dodiuk 15.1 Introduction 427 15.2 Debondable Adhesives 428 15.2.1 Types of Debonding Adhesives 428 15.2.2 Reversible Covalent Bonds Containing Adhesives 429 15.3 Biobased Debondable and Recyclable Adhesives 431 15.3.1 Biodegradable Adhesives 431 15.3.2 Biobased Reversible Covalent Bonds Containing Adhesives 438 15.4 Summary 453 List of Abbreviations 453 References 454 16 Fungal Mycelia as Bioadhesives 463 Wenjing Sun, Mehdi Tajvidi and Christopher G. Hunt 16.1 Introduction 463 16.2 Basics of Fungal Mycelia 464 16.2.1 Fungal Species 464 16.2.2 Fungal Cell Wall 464 16.2.3 Effects of Fungal Mycelia on Lignocellulosic Substrates 465 16.3 Production Procedure 465 16.4 Adhesive Performance 467 16.4.1 As-Grown Foams 467 16.4.2 Hot-Pressed Panels 470 16.4.3 Engineered Living Materials 470 16.5 Improvement Strategies 470 16.5.1 Incorporating Natural Fibers 471 16.5.2 Infusing Bio-Resin 471 16.5.3 Incorporating Natural Reinforcement Particles 471 16.6 Prospects 471 16.7 Summary 471 Acknowledgements 472 List of Abbreviations 472 References 472 17 5-Hydroxymethylfurfural-Based Adhesives: Challenges and Opportunities 477 Wilfried Sailer-Kronlachner, Catherine Rosenfeld, Johannes Konnerth and Hendrikus van Herwijnen 17.1 Introduction 477 17.2 5-Hydroxymethylfurfural as Biobased Platform Chemical 479 17.2.1 Potential as Chemical Building Block 479 17.2.2 Challenges in the Implementation of an Industrial 5-HMF Production 480 17.3 5-HMF-Based Adhesive Systems 483 17.3.1 Wood Adhesives 484 17.3.2 Non-Wood Applications of 5-HMF-Based Adhesives 487 17.3.3 Examples of Adhesives Produced from 5-HMF Derivatives 488 17.4 Prospects 490 17.5 Summary 491 Acknowledgements 491 List of Abbreviations 492 References 492 18 Adhesive Precursors from Tree-Derived Naval Stores 499 Charles R. Frihart 18.1 Introduction 499 18.2 Sources and Structures 500 18.2.1 Rosins 500 18.2.2 Fatty Acids 502 18.2.3 Terpenes 503 18.3 Pressure-Sensitive Adhesives 503 18.4 Chemistry and Products 505 18.4.1 Rosins 505 18.4.2 Modification of the Carboxylic Acid 506 18.4.3 Modification of the Olefinic Portion 508 18.4.4 Ink Pigment Binders 509 18.4.5 Tall Oil Fatty Acids 510 18.4.6 Terpenes 512 18.5 Summary 513 List of Abbreviations 513 References 513 Part 3: Applications of Biobased Adhesives 517 19 Naturally-Based Adhesives for Wood and Wood-Based Panels 519 Manfred Dunky 19.1 Introduction 519 19.2 Protein-Based Wood Adhesives 521 19.2.1 Wood Bonding with Proteins 522 19.2.2 Plant-Based Proteins (for Soy Proteins see Section 19.2.3) 524 19.2.3 Soy Proteins 525 19.2.4 Animal-Based Proteins 528 19.2.5 Denaturation and Modification of Proteins 531 19.2.6 Crosslinking of Proteins 534 19.3 Wood Adhesives Based on Carbohydrates 535 19.3.1 Types and Sources of Carbohydrates for Use as Wood Adhesives 535 19.3.2 Modification of Starch for Possible Use as Wood Adhesive 537 19.3.3 Combination and Crosslinking of Carbohydrates with Natural and Synthetic Components 539 19.3.4 Degradation and Repolymerization of Carbohydrates 539 19.4 Tannin-Based Wood Adhesives 539 19.4.1 Types and Chemistry of Condensed Tannins 540 19.4.2 Hardening and Crosslinking of Tannins 542 19.4.3 Combination of Tannins with Other Components 546 19.5 Wood Adhesives Based on Lignin 547 19.5.1 Chemistry and Structure of Lignin 547 19.5.2 Modification of Lignin 548 19.5.3 Lignin as Adhesive 552 19.5.4 Lignin as Sole Adhesive 554 19.5.5 Reactions of Lignin with Various Aldehydes and Other Naturally-Based Components 557 19.6 Summary 558 List of Abbreviations 558 References 559 20 Activation of Wood Surfaces and “Binderless” Wood Composites 579 Manfred Dunky 20.1 Introduction 579 20.2 Self-Adhesion and “Binderless” Boards 584 20.2.1 Wood and Non-Wood Components for “Binderless” Boards 586 20.2.2 Thermal and Physical Pretreatments of Wood Material and the Wood Surface 589 20.2.3 Chemical Treatments of the Wood Surface 591 20.2.4 Enzymatic Pretreatment of the Wood Surface 595 20.2.5 Degradation and Re-Polymerization of Carbohydrates 598 20.2.6 Citric Acid 601 20.2.6.1 Sugars and Starch in Combination with Citric Acid 601 20.2.6.2 Wood in Combination with Citric Acid 602 20.2.7 Hardboards (Wet Fiber Process) 605 20.2.8 Wood Welding 607 20.3 Summary 611 List of Abbreviations 611 References 612 21 Bonding of Solid Wood-Based Materials for Timber Construction 621 Peter Niemz and Manfred Dunky 21.1 Introduction 621 21.2 Brief Overview of Solid Wood-Based Materials 622 21.3 Adhesives Used for Materials in Structural Timber Engineering 625 21.3.1 Adhesives for the Production of Glued-Laminated Timber (Surface Bonding) 625 21.3.2 Casein Adhesives 628 21.4 Factors Influencing the Quality of Adhesively-Bonded Wood 631 21.4.1 Short Overview 631 21.4.2 Influence of the Wood Substrate (Structure and Wood Species) 631 21.4.3 Influence of Adhesives 636 21.4.4 Influence of Wood Machining 643 21.4.5 Quality Control of Bonded Wood Joints 644 21.4.6 Influence of Service Conditions 644 21.4.7 Aging of Bonded Wood 646 21.5 Trends in the Use of Biobased Adhesives 649 21.6 Summary 650 List of Abbreviations 651 References 652 22 Applications and Industrial Implementations of Naturally-Based Adhesives 659 Manfred Dunky 22.1 Introduction 659 22.2 Wood-Based Panels 660 22.3 Shoe Fabrication (Footwear Industry) 664 22.4 Bonding of Metals 666 22.5 Composites in Automotive, Aircraft, and Aeronautical Industries 667 22.6 Natural Composites with Matrices Based on Natural Resources 673 22.7 Mineral Wool 679 22.8 Packaging and Other Applications 679 22.9 Biomedical Applications 680 22.10 Biodegradability and Recycling 681 22.11 Life Cycle Analysis (LCA) 683 22.12 Summary 686 List of Abbreviations 686 References 688 23 Bioadhesives for the Advancement of Controlled Drug Delivery and Wearable Bioelectronics 705 Monalisha Ghosh Dastidar, Sharmili Roy and Sudarsan Neogi 23.1 Introduction 705 23.1.1 History of Bioadhesives and their Evolution 706 23.1.2 Classification of Bioadhesives 706 23.1.2.1 Natural Bioadhesives 707 23.1.2.2 Biological and Biocompatible Bioadhesives 707 23.1.2.3 Biomimetic and Bioinspired Bioadhesives 707 23.1.3 Mechanism of Bioadhesives 708 23.2 Bioadhesives in Controlled Drug Delivery 708 23.3 Bioadhesives in Bioelectronics 710 23.4 Limitations of Bioadhesives for Biomedical Applications 717 23.5 Summary and Future Prospects 718 List of Abbreviations 719 References 720 Index 727

Unique and comprehensive book edited by acknowledged leaders on biobased adhesives that will replace petroleum-based adhesives. This book contains 23 chapters covering the various ramifications of biobased adhesives. The chapters are written by world-class scientists and technologists actively involved in the arena of biobased adhesives. The book is divided into three parts: Part 1: Fundamental Aspects; Part 2: Classes of Biobased Adhesives; and Part 3: Applications of Biobased Adhesives. Topics covered include: an introduction to biobased adhesives; adhesion theories and adhesion and surface issues with biobased adhesives; chemistry of adhesives; biorefinery products as biobased raw materials for adhesives; naturally aldehyde-based thermosetting resins; natural crosslinkers; curing and adhesive bond strength development in biobased adhesives; mimicking nature; bio-inspired adhesives; protein adhesives; carbohydrates as adhesives; natural polymer-based adhesives; epoxy adhesives from natural materials; biobased polyurethane adhesives; nanocellulose-modified adhesives; debondable, recyclable, and biodegradable biobased adhesives; 5-Hydroxymethylfurfural-based adhesives; adhesive precursors from tree-derived naval stores; and applications in various diverse arenas such as wood bonding, controlled drug delivery, and wearable bioelectronics. Audience This book will interest materials scientists, adhesionists, polymer chemists, marine biologists, food and agriculture scientists, and environmentalists. R&D personnel in a slew of wide-ranging industries such as aviation, shipbuilding, railway, automotive, packaging, construction, wood bonding, and composites should find this book a repository of current and much-needed information.