Adhesives and Finishes for Wood

Preface xix Author Biography xxi 1 Introduction to Polymers, Wood Adhesives, and Wood Finishes 1 1.1 Good Wood Adhesives Must Be Optimum Polymers with Optimum Secondary Forces 1 1.2 Polymeric Materials 2 1.3 Synthetic Polymer Preparation Methods 2 1.4 Typical Synthetic Polymer Materials 3 1.5 Typical Natural Polymers 8 1.6 Summary 10 References 11 2 Principles of Polymer Chemistry for Wood Adhesives and Finishes 12 2.1 Degree of Polymerization and Molecular Weight 12 2.2 Properties of Polymer Solutions or Suspensions 13 2.3 Polymer Solids Level and Specific Gravity of Polymer Solutions 18 2.4 pH of Polymer Solutions and Buffers 18 2.5 Solid Properties of Polymer Materials 20 References 22 3 Thermosetting and Thermoplastic Wood Adhesives and Practices 23 3.1 Selection Criteria of Wood Adhesives 23 3.2 High Temperature-Curing Thermosetting Adhesives and Curing Conditions 24 3.3 Room Temperature-curing Thermosetting Wood Adhesives and Processes 25 3.4 Room Temperature-curing Thermoplastic Wood Adhesives 25 3.5 Adhesive Application Methods and Loading Rates and Costs 26 3.6 Adhesive Curing by Hot Presses and Other Heating Methods 26 3.7 Evaluation of Adhesive Bonds 28 3.8 Summary 28 References 28 4 Principles of the Curing of Thermosetting and Thermoplastic Wood Adhesives 29 4.1 Principles of Curing of Thermosetting Adhesive Resins at Elevated Temperatures 29 4.2 Relationship of Temperature and Moisture Content in Hot-Pressing of Wood Composite Mats 33 4.3 Curing of Thermosetting Adhesives at Room Temperature 35 4.4 Curing of Thermoplastic Emulsion Adhesives 36 4.5 Volume Contractions of Adhesive Layers upon Curing 37 4.6 Thermal and Moisture Expansion/Contraction of Adhesive Layers 38 4.7 Summary 38 References 39 5 UF and MUF Wood Adhesive Resins (Manufacturing and Resin Chemistry) 40 5.1 Raw Materials of UF Resins 40 5.2 Urea-Formaldehyde (UF) Resins 42 5.3 Chemistry Occurring in UF Resin Synthesis 46 5.4 Polymer Chain Branching in UF Resins 50 5.5 Other Reactions Occurring in UF Resin Synthesis 52 5.6 F/U1 Mole Ratio Effects in the Polymerization Step 53 5.7 Final F/U Mole Ratios and Formaldehyde Emission Problem 54 5.8 Physical and Chemical Tests and Properties of Industrial UF Resins 55 5.9 Resin Changes Occurring After Manufacture of UF Resins 58 5.10 Bond Performances and Durability Tests of UF Resins in Industry 60 5.11 UF Resins vs. Various Operating Parameters in PB, MDF, and Hardwood Plywood Industry 61 5.12 Other UF Resin Synthesis Procedures 62 5.13 Polymeric Chemical Structures of UF Resins 63 5.14 Melamine-Urea-Formaldehyde (MUF) Resins 63 5.15 Urea-Melamine-Formaldehyde (UMF) Resins 66 5.16 Summary 69 References 69 6 Urea-Formaldehyde and MUF/UMF Wood Adhesive Resins (Curing) 72 6.1 Typical Latent/External Catalysts Based on Ammonium Salts for UF Resins 72 6.2 Organic Tertiary Amine Salts of Strong Acids and Other Catalysts 73 6.3 Catalyzation of UF Resins by Wood Acids 74 6.4 Buffering of Acidic Catalysts 77 6.5 Thermosetting Curing Reactions, Cured Resin Structures, and Formaldehyde Emission Problem 78 6.6 Control of the Curing Speeds of UF Resins 81 6.7 Side-Reactions Occurring in the Curing of UF Resins 81 6.8 Phenomenological Changes of UF Resins in Curing 82 6.9 Chemical Curing Mechanisms, F/U Mole Ratio, and Cured Resin Structure 84 6.10 Composition of Cured UF Resins 85 6.11 Uses of UF Resins 86 6.12 Properties of UF Resin-Bonded Wood Composite Boards 86 6.13 Formaldehyde Emission Mechanisms, Mole Ratios, and Board Strength Properties 87 6.14 Various Methods Proposed/Practiced for Reducing the Formaldehyde Emissions of Boards 88 6.15 Curing of Melamine-Urea-Formaldehyde (MUF) Resins 89 6.16 Curing of Urea-Melamine-Formaldehyde (UMF) Resins 90 6.17 Cost Increases Estimated for Boards with Very Low Formaldehyde Emission Values 91 6.18 Summary 92 References 92 7 Particleboard, MDF, and Hardwood Plywood Bonding with UF Resin Binders 94 7.1 Particleboard 94 7.2 Medium Density Fiberboard (MDF) Bonded with UF Resins 102 7.3 Hardwood Plywood Bonding with UF Resin Adhesives 109 7.4 Paraffin Wax and Uses in Wood Composites 112 7.5 Effects of UF Resins’ Curing Catalysts on Tool Wear in Machining of Boards – An Example of Laboratory PB Manufacturing and Testing 115 7.6 Summary 120 References 120 8 PF Novolac Wood Adhesive Resins (Manufacturing and Chemistry) 122 8.1 Raw Materials of PF Resins 122 8.2 Reaction Chemistry of Phenol 123 8.3 Synthesis and Chemistry of Novolac Phenol-Formaldehyde (PF) Resins 124 8.4 Compounding and Curing of Novolac PF Resins 129 8.5 Curing Speed and Testing Methods of Molding Compounds of PF Novolac Resins 130 8.6 Wood Adhesive Uses of Novolac PF Resins 132 8.7 Summary 133 References 134 9 PF Resole Wood Adhesive Resins (Manufacturing and Chemistry) 136 9.1 Alkaline PF Resole Wood Adhesive Resins 136 9.2 Synthesis Chemistry and Manufacturing Practices of Alkaline PF Resole Resins 136 9.3 Typical Synthesis Procedures of Alkaline PF Resole Resins for Various Uses 140 9.4 Properties and Polymer Structures of Alkaline PF Resole Resins and Measurements 143 9.5 Resin Characteristics and Uses of Various PF Resole Resins 147 9.6 Molecular Weights (Sizes) of Alkaline PF Resole Resins and Wood Cell Wall Penetration 148 9.7 Powder PF Resole Resin Manufacturing by Spray-drying 149 9.8 Curing of Alkaline PF Resole Resins 150 9.9 Good Wood Adhesion and Exterior Durability of PF Resin Adhesives 158 9.10 Formaldehyde Emission Problem of PF Resin-bonded Products 159 9.11 Various Binder Uses of PF Resins in the US Wood Products Industry 159 9.12 Acid-curing PF and PMF Resole Resin and Dispersion Wood Adhesives 162 9.13 Summary 163 References 163 10 PRF Novolac Wood Adhesive Resins and Lumber Lamination 166 10.1 Manufacturing and Chemistry of PRF Resins 167 10.2 PRF and RF Resin Adhesives Currently Available in Industry 172 10.3 Hardeners for PRF Resin Adhesives 174 10.4 Mixing of a PRF Resin and Hardener, Pot-Lives, Working Life, and Assembly Time 175 10.5 Applying and Curing of PRF Adhesives in Wood Lamination 176 10.6 Curing Chemistry of PRF Resin Adhesives and Industry Practices 179 10.7 Wood Lamination Industry 179 10.8 Recent Developments in PRF Resin Adhesives 182 10.9 Laminating Wood Adhesives Based on Other Resorcinolic Materials 184 10.10 Advanced Reading Materials on Resorcinol–Formaldehyde (RF) Resins 185 10.11 Summary 191 References 191 11 Softwood Plywood Adhesives and Manufacturing Technology 194 11.1 Softwood Plywood Manufacturing Technology 194 11.2 PF Resole Resins for Bonding of Softwood Plywood 195 11.3 Veneer, Veneer Drying, and Adhesion Problems 196 11.4 Bond Performance Characteristics of Softwood Plywood Adhesives 197 11.5 Softwood Plywood Adhesive Mixing Procedure 197 11.6 Softwood Plywood Adhesive Formulation and Characteristics 198 11.7 Open and Closed Assembly Times 204 11.8 Pre-pressing of Softwood Veneer Assembly 204 11.9 Hot-Pressing Parameters of Softwood Plywood 204 11.10 Laminated Veneer Lumber (LVL) 207 11.11 Parallel (Veneer) Strand Lumber (PSL) 207 11.12 New Developments in the Softwood Plywood Adhesive Technology 208 11.13 Phenolic Components Present in PF Resin-Bonded Softwood Plywood 209 11.14 Softwood Plywood Manufacturing Industry 209 11.15 Plywood Adhesive Fillers Made from Hydrolysis Residues of Municipal Newsprint Wastes 210 11.16 Conclusion 214 11.17 Summary 214 References 214 12 Isocyanate Wood Adhesive Resins 217 12.1 Chemical Compositions of Isocyanate Wood Adhesive Resins 217 12.2 Reactivity, Polymerization, and Curing Reactions of Isocyanate Resins 218 12.3 Mat Moisture Levels in Using pMDI Resins for OSB Bonding 223 12.4 Bond Properties and Uses of pMDI Resins as OSB Binders 224 12.5 pMDI Resins Used in Bonding of Other Wood Composite Products 226 12.6 Summary 227 References 227 13 OSB Manufacturing with PF and Isocyanate Wood Adhesive Resins 229 13.1 Oriented Strand Board (OSB) Manufacturing Processes 229 13.2 OSB Bonded with PF Resins with Various Levels of Urea Added at the End of Resin Synthesis 240 13.3 Summary 246 References 247 14 Polyvinyl Acetate (PVAc) Emulsion Wood Adhesives 249 14.1 Polyvinyl Acetate (PVAc) Emulsion Wood Adhesive Resins 249 14.2 Summary 253 References 254 15 Troubleshooting in Wood Bonding with PVAc Resin Adhesives 255 15.1 Effects of Moisture Content of Wood 255 15.2 Troubleshooting Methods in Various Gluing Operations 259 Reference 262 16 Hot-melt and Other Specialty Wood Adhesives 263 16.1 Introduction to Hot-melt Adhesives 263 16.2 Requirements For Hot-melt Adhesives 263 16.3 Materials Used for Hot-melt Wood Adhesive Formulations 265 16.4 Advantages and Disadvantages of Hot-melt Adhesives 266 16.5 Thermosetting Hot-melt Adhesives – Recent Development 267 16.6 Key Variables in Hot-melt Edge-banding Operation 268 16.7 Other Specialty Wood Adhesives 269 References 273 17 Casein, Soybean Flour, Animal Blood, and Lignin Wood Adhesives 275 17.1 Casein Wood Adhesives 275 17.2 Animal Protein-Based Wood Adhesive 276 17.3 Soybean Meal and Soybean Protein Wood Adhesives 276 17.4 Animal Blood-based Wood Adhesives 278 17.5 Various Lignins and Uses in Wood Adhesives 278 References 281 18 Theory and Practices of Adhesive Bonding for Wood 283 18.1 Formation of Interphase in Wood Adhesive Bonds and Failure Modes 283 18.2 Wettability of Solid Surface, Contact Angle, and Surface/Interface Tensions 287 18.3 Work of Adhesion 291 References 291 19 Physical and Chemical Mechanisms of Adhesive Bonding for Wood 292 19.1 Adsorption (Secondary Bond Forces) Theory of Adhesion 292 19.2 Mechanical Interlocking Theory of Adhesion 296 19.3 Diffusion Theory of Adhesion 297 19.4 Primary Chemical Bond (Covalent Bond) Theory 298 19.5 Summary of Adhesion Mechanisms 299 19.6 Glueline Layer Thickness and Bond Strengths 299 19.7 Summary 301 References 301 20 Evaluation of Wood Adhesive Bonds, Quality Control, and Bond Durability 302 20.1 Mechanical Testing Modes and Methods for Measuring the Adhesive Bond Strength 302 20.2 Quality Control, Certification Tests, and Adhesive Bond Durability 309 20.3 Comparison of Various Wood Adhesive Bonds by Accelerated Aging or Exterior Exposure Tests 313 20.4 Nondestructive Testing of Wood and Wood Adhesive Bonds 315 20.5 In-situ Adhesion Testing 315 References 316 21 Introduction to Coatings Technology for Wood 317 21.1 Three Components of Coatings 317 21.2 Pigment Volume Concentration (PVC) 317 21.3 Various Kinds of Vehicle Polymers 319 References 328 22 Introduction to Coatings Technology for Wood. II 329 22.1 Pigments and Fillers 329 22.2 Manufacturing and Kinds of Pigments and Fillers 329 22.3 Color Control Methods 329 22.4 Color Scales – Hunter L, a, b, and CIE 1976 L*a*b* (CIELAB) Color Scales 331 22.5 Carriers of Coatings 332 22.6 Additives to Coatings 332 22.7 Manufacturing Procedures of Coatings 332 22.8 Film Formation Mechanisms 333 22.9 Water-Borne Coatings and Coatings for Less VOC Emissions 334 22.10 Exterior Coatings for Wood 336 22.11 Summary 337 References 338 23 Industrial Coating Application Processes 339 23.1 Application Methods of Coatings 339 23.2 Sanding Processes 342 23.3 Sanding Abrasives, Construction, and Flexing 344 23.4 Typical Furniture Finishing Procedures and Materials 344 23.5 Flat Line Finishing Procedures of Wood Composite Boards for Furniture Production 346 23.6 Kitchen Cabinet Finishing Procedures 347 23.7 Hardwood Plywood Panel Prefinishing 348 23.8 Hardboard Panel Finishing Procedures 349 23.9 Summary 350 References 350 24 Advanced Reading Materials on UF Wood Adhesive Resins 351 24.1 Introduction to the 13C NMR Spectroscopic Analysis Method 351 24.2 Introduction to 13C NMR Analysis Methods of UF and UMF Wood Adhesive Resins 356 24.3 13C NMR Analysis Results of Reaction Intermediates Taken in UF Resin Syntheses 360 24.4 13C NMR Analysis Results of Reaction Intermediates Taken in UF Resin Syntheses with a Higher Power Instrument 366 24.5 Chemical Changes Occurring in UF Resins on heat/stirring and Room-temperature Storage Treatments by 13C NMR and Formaldehyde Emission Tests of Particleboard 374 24.6 Effects of Mild Heating/Stirring Treatments on UF Resins Synthesized with Different F/U1 Mole Ratios by 13C NMR 382 24.7 Effects of Room-temperature Storage Treatments on UF Resins Synthesized with Various F/U1 Mole Ratios by 13C NMR and Formaldehyde Emission Tests of Particleboard 388 24.8 Effects of Mild Heat/Stirring and Room-temperature Storage Treatments of UF Resins Synthesized with Various F/U1 Mole Ratios by 13C NMR and Formaldehyde Emission Tests 397 References 418 25 Advanced Reading Materials on UMF Resins Modified with 6–12% Melamine 420 25.1 Introduction and Synthesis and Analysis Results of UF and UMF Resins 420 25.2 DMA Curing Properties of UF and UMF Resins 432 25.3 Bond Performance of UMF Resins as Particleboard Binders 443 References 445 26 Advanced Reading Materials on UMF Resins Modified with 2.5% and 5.0% Melamine 447 26.1 UMF Resins Synthesized with 2.5% and 5.0% Melamine Levels 447 26.2 UMF Resins Synthesized by Adding Melamine at Different Points 456 References 467 27 Advanced Reading Materials on Diethylene Tricarbamide-Formaldehyde Resins 468 27.1 Introduction 468 27.2 A Higher Functionality Urea Analogue – Diethylene Tricarbamide 469 27.3 Chemical and Physical Properties of Diethylene Tricarbamide 469 27.4 An Efficient Synthesis Method of Diethylene Tricarbamide 470 27.5 Synthesis Chemistry and Procedure and Properties of D-formaldehyde (DF) and Copolymer Resins 470 27.6 Synthesis Formulations of DF Resins vs. UF Resins 471 27.7 Room Temperature Storage Properties of DF and Copolymer Resins 472 27.8 Pot-lives and Curing Characteristics of DF and Copolymer Resins 472 27.9 Preparation of Laboratory Particleboards and Testing 473 27.10 Test Results of Prepared Laboratory Particleboards 473 27.11 Summary 475 References 475 28 Advanced Reading Materials on PF Resole Wood Adhesive Resins 476 28.1 Chemical Structures of PF Resole and Novolac Resins by 13C NMR Spectroscopy 476 28.2 Reaction Rates and Structures of a PF Resole Resin Synthesized at 70∘C 482 28.3 Polymer Structures of a PF Resole Resin Synthesized at 102∘C vs. a Commercial Resin 490 28.4 Polymer Structures of High Molecular Weight Fractions of a PF Resole Resin 500 28.5 Polymer Structures of Cured PF Resole Resins by Solid-state 13C NMR 508 References 518 Index 521