Principles ofWood Science and Technology

11

Wood Based Materials

Franz F. P. Kollmann EJ ward W. Kuenzi

Alfred J. Stamm

Springer-Verlag Berlin Heidelberg NewYork 1975

Franz F. P. Kollmann

o. ö. Professor (em.) an der Universität München

Institut für Holzforschung und Holztechnik

Edward W. Kuenzi

Professor at the U.S. Forest Products Laboratory

Madison, Wis.

Alfred J. Stamm

Professor (ern.) at the North Carolina State University

School of Forest Resources

Departrnent of Wood and Paper

Science, Raleigh, N.C.

ISBN 978-3-642-87933-3 ISBN 978-3-642-87931-9 (eBook) DOI 10.1007/978-3-642-87931-9

Tbi. work i. subjec< to copyright. All rights are rcsetved, whether thc whole or part of the material i. concerned, specifically

those of translation, rcprinting, re-use of illustrations, broadcasting, teproduction by photocopying machine or similar means~ and storage in data banks. Under § 54 of thc German Copyright Law where copies are made fot other than private usc, 11 fee is

payable to the publisher, the amount of the fee to be determined by agreement with the publisher. ® by Springer-Verlag, BerlinjHeidelberg 1975.

Softcover reprint of the hardcover Ist edition 1975 Library of Congte.s Catalog Card Number; 67-29614

Tbc use of registered names, trademarks, ete. in tbis publication does not imply, even in thc absence of a specific statement, that such names are exempt from thc relevant protective Iaws and regulations and therefore {ree fot general use.

PREFACE

The principal author published the first edition of a book entitled in German "Technologie des Holzes" (Springer-Verlag) in the year 1936. This book was available only in photostat copy form in the United States during World War n. A translation into the English language was later made in Australia. Due to many hampering factors caused by World War n it was not unti11951 that the second edition of the first volume of thir:; book with the enlarged title (translated) "Technology of 'Vood and W ood Based Materials" was published. The se co nd volume followed in 1955.

The enormOllS expansion of wood seience and technology within less than two deeade,: is evident from a comparison of the number of pages of these two editions. The first edition eomprises 764 pages, the two volumes of the second edition 2231 pages.

More recently, it becamc evident that an English version in a condensed up-to-date form was needed. Therefore, the principal author decided to publish a book on "Principles of W ood Science and Technology" in English. The first volume dealt with solid wood, this second volume deals with wood based materials. U sing the ward "Principles" in the title of the condensed book this led directly to abandoning ft11 detailed historie al reviews, explanations, ftnd discussions of mftchines and processes.

The prineipal author asked for direct and indirect assistance by outstanding experts in eompiling both volumes. He was happy that Prof. W. A. Gote, Jr. wrote chapters on structure, fine structure, chemistry, and pathology of solid wood for the first volume. In this second volume he obtained valuable contributions of complete chapters b.v Prof. A . .J. Stamm on "Solid Modified Wood" and Mr. Edward W. Kllenzi, P. E .. on "Sandwich Composites". In writing foul' chapters of this secoml volurne, the principal author is extremely grateful that co 1-leagucs abroad reviewed and corrected, as far as necessary, his original drafts. He wishes to express his sincere gratitude to

Prof. A. P. Schniewind (Chapters "Adhesion and Adhesives" and "Fiberboard"), Mr. F. C. Lynam (Chapters "Veneer, Plywood, and Laminates" and "Particle-board"\, Prof. Raymond A. Moore (Ohapter "Veneer, Plywood, and Laminates"), Prof. Alan A. ~/I;[arra (Chapter "Particleboard"), and Prof. A. J. Stamm (Chftpter "Fiberboard").

MI'. A. Kaila kindly gave permission to make use of the content of the chapter "Boardindustrien" (p. 821 to 1109), contributed by him to "Träindustriell Hand-bok" (Ed.: O. Ileikinheimo; Stockholm, 1968: AB Svenks Trävarutidning). MI'. 8. Ake Lundgren also kindly gave permission to use his article "Wood-based sheet as a struetural material", published by the Swedish Wallboard Manufacturers' Association in the booklet "Swedish Fibreboard Information", Stockholm 1969.

The author is fnrthermore indebted to colleagues in Germany: Dr. Dietger Gro88fI Dr.-Inf!'. Max Kulner, Prof. Dr. Erich Plath, Dr. Eberhard Schmidt, and

1*

IV Preface

Dr. Reinwald Teichgräber. He also received printed material and letter communi-cations from the industry concerned either with production of wood based materials or with manufacture of machinery and equipment for these industries.

Miss R. Preissler wrote the numerous letters necessary in conjunction with the whole work and wrote the drafts and final manuscripts of the chapters. Drafts of pictures and diagrams were made with skill and care by lng. H. Sanzi and the many necessary mimeographed copies of sketches and diagrams and glossy prints by Mrs. H. Bauer. The authors of this book are sincerely indebted to Springer-Verlag publishers of the volumes in the high standard of printing and illustrat-ing admired throughout the world.

München, Germany Madison, Wis., U.S.A. Raleigh, N.C., U.S.A., 1974

Franz F. P. Kollmann Edward W. Kuenzi Alfred J. Stamm

CONTENTS

1. Adhesion and Adhesives for Wood. By Franz F. P. Kollmann 1

1.0 General Considerations about Gluing 1

1.1 Physical-Chemical Princ'iples of Gluing . 2 1.1.1 Cohesion and Adhesion. . . . . 2 1.1.2 Intermolecular Forces, Polarity . 5 1.1.3 Influence of Temperature, Concentration and Amount of Polymerization 9 1.1.4 Influence of pH Value on the Hardening of Glue Joints. 9 1.1.5 Colloidal State of Wood Glues, Sols and Gels 10 1.1.6 Rheology of Glues . . . . . . . . . . . . . . . . . 11 1.1.7 Phenomena of Hardening. . . . . . . . . . . . . . 13 1.1.8 Fortifying (Upgrading), Filling, Extending of Glues for Wood 15

1.2 Strength Improvement and Stresses in Glue Joints 17

1.3 Testing of Glue Joints. . . . . . . . . . . . . 18

1.4 Summarized Results of Tests for Various Glues. . 21

1.5 Effect of Wood Species and Moisture Content on the Strength of Glue Joints 22

1.6 Pretreatment of Wood Prior to Gluing . 24

1.7 Glue Spreading. . . . . . . . . . . 25

1.8 Pressing of Glued Parts and of Laminated Wood 27

1.9 Difficulties and Defects in Gluing. . . . . . 28

1.10 Natural Glues . . . . . . . . . . . . . . 34 1.10.1 Starches, Dextrins and Natural Gums 34 1.10.2 Protein Glues . . . . . . . . . . . 38

1.10.2.1 Animal Glues, Manufactured from Hide, Sinews, Bones 38 1.10.2.2 Casein Glues. . . . . . . . . . . . . . . . . . . 42 1. 10.2.3 Blood Albumin Glues. . . . . . . . . . . . . . . 47 1.10.2.4 Soyabean (or Soybean) Glues and Peanut-Meal Glues . 49

1.10.3 Shellac . . . . . . . . . . . . . . . . 50 1.10.4 Asphalt (Bitumen) and Mastic. . . . . . 50 1.10.5 Natural and Synthetic Rubber (Neoprene) 51 1.10.6 Glues on Cellulose Basis 54

1.10.6.1 Cellulose Acetates 54 1.10.6.2 Cellulose Esters 54

1.10.7 Silieate of Soda . . 54

1.11 Synthetic Glues . . . . . . . 56 1.11.0 General Considerations . 56 1.11.1 Phenol-Formaldehyde Resin Glue 57

1.11.1.1 History of Phenolic Resin Glues 57 1.11.1.2 Manufacture and Chemistry of Phenol-Formaldehyde Resins . 57 1.11.1.3 Application of Phenolic Resin Glues . . 61 1.11.1.4 Properties of Phenolic Resin Glue Joints 65

1.11.2 Rpsorcinol-Formaldehyde Adhesives . 66 1.11.3 L'rea-Formnldehyde Resin Adhesives . 68

1.11.3.1 History of Urea Resin Glues . 68

VI Contents

1.11.3.2 Manufacture and Chemistry of Urea-Formaldehyde Glues 69 1.11.3.3 Hardening of Urea-Formaldehyde Resins . . . . . . . 70

1.11.4 Melamine-Formaldehyde Resin Adhesives. . . . . . . . . . . 74 1.11.4.1 History, Chemistry, and Manufacture of Melamine-Formaldehyde

Adhesives. . . . . . . . . . . . . . . . . . 74 1.11.4.2 Application of Melamine-Formaldehyde Adhesives . . . 76 1.11.4.3 Hardening of Melamine Adhesives . . . . . . . . . . 79 1.11.4.4 Properties of Melamine-Formaldehyde Resin Glue Joints 79 1.11.4.5 Fortüying or Upgrading of Urea Adhesives 79 1.11.4.6 Surface Coating of Wood Based Materials 80

1.11.5 Thermoplastic Resin Adhesives . . . . . . 81 1.11.5.1 General Properties and Manufacture 81 1.11.5.2 Cellulose Adhesives. . . . 82 1.11.5.3 Polyvinyl Acetates (PV A) . 82

1.11.6 Other Synthetic Organic Adhesives . 86 1.11.6.1 Epoxy Glues. . . . . . 86 1.11.6.2 Polyurethane Adhesives . 86

Literature Cited. . . . . . . . . . . . . . . 88

2. Solid Modified Woods. By Al/red J. Stamm 94

2.0 Introduction . . . . . . . . . . . 94 2.1 Fundamentals of Impregnation . . . 94

2.1.1 Flow through True Capillaries . 96 2.1.2 Flow through Softwoods . . . 96

2.1.2.1 Structure Involved . . 96 2.1.2.2 Permeability to Liquids and Gases 97 2.1.2.3 Longitudinal versus Transverse Flow 98 2.1.2.4 Mean Pit Membrane Pore Numbers and Radii 99 2.1.2.5 Effect of Gas-Liquid Interphases 100

2.1.3 Düfusion in Wood 103 2.2 Treating Methods. . . . . . . . . . . . 105

2.2.1 Sap Displacement . . . . . . . . . 106 2.2.2 Capillary Absorption andJor Diffusion 106 2.2.3 Pressure Methods . . . . . . . . . 107

2.3 Wood Preservation against Attack by Organisms 107 2.3.1 General. . . . . . . . . . . . . . 107 2.3.2 New and Modüied Treating Methods . 108

2.3.2.1 Double Diffusion . . . . . 109 2.3.2.2 Modified Boucherie Process 110 2.3.2.3 Predrying Methods 111 2.3.2.4 Cellon Process . . 111

2.4 Wood Preservation against Fire 112 2.4.1 Fire Hazards . . . . . . 112 2.4.2 Fire Retardant Treatment 113

2.5 Dimensional Stabilization 116 2.5.1 Cross-Laminating 116 2.5.2 External Coatings . 116 2.5.3 Internal Coatings . 117 2.5.4 Reduction in Hygroscopicity 118

2.5.4.1 Heat Stabilization . 118 2.5.5 Cross-Linking . . . . . 120 2.5.6 Bulking Treatments . . 123

2.5.6.1 Salt Treatments 123 2.5.6.2 Sugar Treatment 124 2.5.6.3 Polyethylene Glycol Treatment 125

Contents

2.5.6.4 Wax Treatment ..... . 2.5.6.5 Phenolic Resin Treatment (Impreg)

2.5.6.5.1 Treating Processes . . 2.5.6.5.2 Properties of Impreg. 2.5.6.5.3 Uses for Impreg

2.5.6.6 Vinyl Resin Treatment. . . 2.5.6.6.1 Strength Properties

2.5.6.7 Acetylated Wood . 2.5.6.8 Other Treatments.

2.6 Densified Wood ....... . 2.6.1 Densifying by Impregnation

2.6.1.1 Metalized Wood .. 2.6.2 Densifying by Compression .

2.6.2.1 Plasticizing Wood .. 2.6.2.1.1 Bending Wood

2.6.2.2 Resin-Treated Compressed Wood (Compreg) 2.6.2.2.1 Making Compreg ....... . 2.6.2.2.2 Properties and Uses of Compreg

2.6.2.3 Stable Untreated Compressed Wood (Staypak)

Literature Cited. . . . . . . . . . . . . . . . . . . . . .

3. Veneer, Plywood and Laminates. By Franz F. P. Kollmann.

3.1 Introduction . . . . . . . . . . . . . . . . . . . . 3.1.1 History, Status and Trends in Germany and North America . 3.1.2 World Production and Analysis of Consumption

3.2 Veneer .................... . 3.2.1 Wood Species .............. . 3.2.2 Pretreatment of Logs Prior to Slicing and Peeling

3.2.2.1 Protection of Logs against Decay and Checking . 3.2.2.2 Steaming and Boiling (Cooking) of Round Logs. 3.2.2.3 Debarking or Cleaning .

3.2.3 Veneer Sawing. . . . . . . . . 3.2.3.1 Introduction . . . . . . 3.2.3.2 Circular Sawing of Veneer 3.2.3.3 Band Sawing of Veneer . 3.2.3.4 Horizontal Gang Saws for Veneer Manufacturing

3.2.4 Veneer Slicing. . . . . . . . . . 3.2.4.1 Introduction . . . . . . . 3.2.4.2 Horizontal Slicing of Veneer 3.2.4.3 Vertical Slicing of Veneer ..

3.2.5 Veneer Rotary-Peeling ..... . 3.2.6 Veneer Handling from the Slicer or Lathe . 3.2.7 Trimming and Clipping . 3.2.8 Veneer Peeling Lines . 3.2.9 Veneer Drying

3.2.9.1 Introduction . . 3.2.9.2 Types of Veneer Dryers, Conventional Drying Times 3.2.9.3 Physics of Veneer Drying.

3.3 Plywood. . . . . . . . . . . 3.3.0 General Considerations . . 3.3.1 Principles of Manufacture .

3.3.1.1 Veneer Jointing and Repairing 3.3.1.2 Applying the Adhesive . 3.3.1.3 Pressing . . . . . . . . . .

VII

128 129 129 130 132 132 134 135 138

139 139 140 141 141 143 143 143 144 145

149

154

154 154 159

163 163 168 168 170 176 178 178 178 180 180 181 181 181 185 186 197 199 201 203 203 203 217

223 223 226 226 227 227

VIII Contents

3.3.1.4 Conditioning . . . . . . . . . 230 3.3.1.5 Panel Finishing (Sizing and Thicknessing) 230

3.3.1.5.1 Sizing or Trimming . . . . . . 230 3.3.1.5.2 Thicknessing (Sanding or Scraping) 233

3.4 Properties of Plywood. . . . . . . 237 3.4.0 Preamble. . . . . . . . . . . . . . . 237 3.4.1 Density, Weight per Unit Area . . . . . 237 3.4.2 Moisture Content, Absorption and Swelling 239 3.4.3 Thermal Conductivity, Acoustical Properties. 245 3.4.4 Mechanical Properties . . . . 246

3.4.4.1 Elasticity and Rigidity. . . . . 246 3.4.4.2 Strength Properties . . . . . . 257

3.4.4.2.0 General Considerations. 257 3.4.4.2.1 Tensile Strength . . 257 3.4.4.2.2 Compressive Strength 258 3.4.4.2.3 Bending Strength . 260 3.4.4.2.4 Shear Strength 262 3.4.4.2.5 Hardness 271

3.4.5 Technological Properties . . . 271 3.4.6 Resistance against Destruction 276

Literature Cited. . . . . . . . . . . . . 279

4. Sandwich Composites. By Edward W. Kuenzi 284

4.0 Introduction . . . . . . . . . . 284

4.1 Basic Design Principles . . . . . 284 4.1.1 Sandwich Bending Stiffness . 286 4.1.2 Sandwich Extensional Stiffness 286 4.1.3 Sandwich Shear Stiffness 287 4.1.4 Facing Stresses . . . . . . . 287 4.1.5 Core Stresses . . . . . . . . 287 4.1.6 Minimum Weight Sandwich Composites . 288 4.1.7 Local Failure Modes 288

4.2 Materials and Fabrication 290 4.2.1 Facings. . 290 4.2.2 Cores. . . . . . . 291 4.2.3 Adhesives. . . . . 293 4.2.4 Sandwich Assembly 294 4.2.5 Inspection. . 296 4.2.6 Test Methods 296 4.2.7 Repair . . . 298

4.3 Structural Components. 299 4.3.1 Beams . 299 4.3.2 Columns . . . . 300 4.3.3 Plates . . . . . 300

4.3.3.1 Plates under Normal Load 300 4.3.3.2 Plates under Edge Loads. 301

4.3.3.2.1 Flat Panels under Edgewise Compression or Bending 302 4.3.3.2.2 Flat Panels under Edgewise Shear. 304

4.3.3.3 Combined Loads. . . . . . . . . . . . . . . . 305 4.3.4 Cylindrical Shells. . . . . . . . . . . . . . . . . . . 305

4.3.4.1 Cylindrical Shells under External Radial Pressure . 305 4.3.4.2 Cylindrical Shells under Torsion. . . . . . . . . 307

Contents IX

4.3.4.3 Cylindrical Shells under Axial Compression or Bending . 4.3.4.4 Cylinders of Sandwich under Combined Loads

309 309 310 311

4..! Dimensional Stability 4.5 Durability

Literature Cited. . . . . . 311

a. Particleboard. By Franz F. P. Kollmann 5.0 History of Production, Consumption and Use of ParticIeboard

312

312

5.1 Raw Materials . . . . . . . . . . . . . . . 319 5.1.1 Wood and Other Ligno·Cellulose Materials 319

5.1.1.0 General Considerations. . . . 319 5.1.1.1 Unprocessed Forest Products . 320 5.1.1.2 Industrial Wood Residues 321 5.1.1.3 Flax Shives . 322 5.1.1.4 Bagasse . . . . . . . . 323

5.1.2 Adhesives. . . . . . . . . . . 327 5.1.2.1 Urea- and Melamine-Formaldehyde Resins 327 5.1.2.2 Phenolic Resin Binders . . . . . 330 5.1.2.3 General Rules for Chip Resination . 331

5.1.3 Additives. . . . . . . 331 5.1.3.1 Water Repellents . . . 331 5.1.3.2 Extenders . . . . . . 335 5.1.:1.3 Fungieides, Insecticides 335 5.1.3.4 Fire Retardants . 339

5.2 General Technology. . . 339 5.2.0 Introduction. . . . . . 339 5.2.1 Particle Preparation . . 340

5.2.1.0 General Considerations . 340 5.2.1.1 Wood Yard, Conveying of Raw Wood, MetaI Detection 340 5.2.1.2 Moisture Content . . 342 5.2.1.3 Barking (Debarking) ..... 343 5.2.1.4 Reduction of Wood . . . . . . 349

5.2.1.4.1 Crosscutting, Splitting. 349 5.2.1.4.2 Primary Reduction, Knife Hogs 349 5.2.1.4.3 Secondary Reduction, Hammer-Mill Hogs, Toothed Disk-

MilIs, Impact Disk-mills . . . . . . . . . . . . . . . 349 5.2.1.4.4 Shaving or Flake Production, Disk Type Chippers, Cutter

Spindie and Cutter Cylinder (Cutter Head) Chippers . 355 5.2.1.4.5 After-Reduction. 362 5.2.1.4.6 Summary . . 366

5.2.2 Drying of Chips . . . . . . . 368 5.2.2.0 General Considerations . 368 5.2.2.1 Dryer Types . . . . . 371

5.2.3 Size Separation (Classifying) by Screening or Sifting 383 5.2.4 Conveying of Chips. . . . . . . . . . . . 387 5.2.5 Storage of Chips (Wet and Dry Bins or Silos) 388

5.2.5.0 General Considerations . 388 5.2.5.1 Horizontal Storage Bins 390 5.2.5.2 VerticaI Storage Bins . 390 5.2.5.:3 Rotating Storage Bins . :391

5.2.6 Dosing (Weighing and Volumetrie Dosing). :392 5.2.7 Chip Blending . . . . . . . . 394

5.2.7.0 General Considerations . 394 5.2.7.1 Batch Operation . . 395 5.2.7.2 Continuous Operation :396

11 Kollmann, Wood Based Materials

x Contents 5.2.8 Mat.Laying (Chip-Spreading) . . . . . . . . . . . . . . . . . .. 402

5.2.8.0 General Considerations. . . . . . . . . . . . . . . . . .. 402 5.2.8.1 Distribution of the Particles, Manually or by Auxiliary Deviees. 402 5.2.8.2 Terms, Failures, Volumetrie and Gravimetrie Dosing of the Material 403 5.2.8.3 Spreading Maehines and Spreader Heads . . . . . . . . . . . . 405 5.2.8.4 Resultant Mat . . . . . . . . . . . . . . . . . . . . . . . 408

5.2.9 Prepressing, Wetting, Flat Pressing (Presses and Assoeiated Equipment), Methods of Operation 409 5.2.9.0 General Considerations. . . . . . 409 5.2.9.1 Prepressing .......... 410 5.2.9.2 Single and Multi-Daylight Presses . 412

5.2.9.2.0 General Considerations. . 412 5.2.9.2.1 Relative Investment Costs 412 5.2.9.2.2 Teehnological Aspeets . . 414 5.2.9.2.3 Effeet of Chip Moisture Content 415 5.2.9.2.4 Effeet of Press Platen Temperature 417 5.2.9.2.5 Effeet of Curing Time on Physieal Properties of Particle-

board ....................... 417 5.2.9.2.6 Influenee of Quantity of Hardener and Proportion of Form-

aldehyde in the Urea Resin on Quality of Particleboard . 419 5.2.9.2.7 Other Teehnologieal Aspeets 420

5.2.9.3 Caulless Pressing Systems . . . . 423 5.2.9.3.0 General Considerations. . 423 5.2.9.3.1 Tray-Belt Molding System 423 5.2.9.3.2 Tablet System . . . . . 425 5.2.9.3.3 Continuous Belt System . 429 5.2.9.3.4 Calender Particleboard Proeess; System Mende-Bison 432

5.2.10 Board Finishing (Sizing and Sanding or Thieknessing) 433 5.2.10.0 General Considerations . 433 5.2.10.1 Sizing . . . . . . . . . . . . . . . . . 434 5.2.10.2 Sanding . . . . . . . . . . . . . . . . 434

5.2.11 Particleboard - Plastie Combinations, Printing on Particleboard 436 5.2.11.0 General Considerations. . . . . . . . . . . . . . . 436 5.2.11.1 Types of Laminates for Particleboard . . . . . . . . 437 5.2.11.2 Structure, Manufaeture, and Testing of Laminated Particleboard 437 5.2.11.3 Printing on Particleboard. 439

5.2.12 Extruded Particleboard . . . . 440 5.2.12.0 General Considerations . 440 5.2.12.1 Vertical Extruders 440 5.2.12.2 Horizontal Extruders . 443

5.2.13 Molded Particle Produets . . . 445 5.2.13.0 General Considerations . 445 5.2.13.1 Thermodyn Process 447 5.2.13.2 Collipress Proeess 449 5.2.13.3 Werzalit Proeess 450

5.3 Some Additional Layouts . 455

5.4 Properties of Particleboard. . . 456 5.4.0 General Considerations . . 456 5.4.1 Factors Affecting the Properties of Particleboard 463 5.4.2 Testing of Particleboard, Standards . . . 464 5.4.3 Density, Weight per Unit Area . . . . . 466 5.4.4 Moisture Content, Absorption and Swelling 468 5.4.5 Thermal Conductivity 472 5.4.6 Acoustical Properties. . . . . 472 5.4.7 Meehanical Properties . . . . 475

5.4.7.0 General Considerations . 475

Contents XI

5.4.7.1 Theoretical Approach to Particleboard ~Iechanics 479 5.4.7.2 Elasticity and Rigidity. . . . . . . . . . . . 483 5.4.7.3 Tensile Strength . . . . . . . . . . . . . . 486

5.4.7.3.1 Tensile Strength, Parallel to Board Plane. 486 5.4.7.3.2 Tensile Strength Perpendicular to Board Plane, Face

Strength. . . . . . . 489 5.4.7.4 Compressive Strength . . . . . . . . . 5.4.7.5 Bending Strength, Creep, Fatigue ....

5.4.7.5.1 Bending Strength, Modulus of Rupture 5.4.7.5.2 Deflection, Modulus of Elasticity 5.4.7.5.3 Creep, Relaxation ..... . 5.4.7.5.4 Fatigue, Endurance .... .

5.4.7.6 Impact Strength, Punctural Resistance 5.4.7.7 Shear Strength . . . . . . . . .

5.4.7.7.0 General Considerations .. 5.4.7.7.1 Compression-Shear Tests. 5.4.7.7.2 Tension-Shear Tests. 5.4.7.7.3 Torsion-Shear Tests

5.4.7.8 Hardness

5.4.8 Technological Properties . . . 5.4.8.0 General Considerations . 5.4.8.1 Surface Quality. . . . 5.4.8.2 Accuracy of Dimensions, Surface Texture and Stability. 5.4.8.3 Machining Properties ........ . 5.4.8.4 Nail-Holding and Screw-Holding Ability .

5.4.8.4.1 Nails . . 5.4.8.4.2 Screws .....

5.4.9 Resistance to Destruction 5.4.9.1 Abrasion (Wear) Resistance 5.4.9.2 Resistance to Biological Attack

5.4.9.2.1 Fungi (Decay) . 5.4.9.2.2 Insects, Termites . .

5.4.9.3 Reaction to Fire. . . . . . . 5.4.9.3.0 General Considerations . 5.4.9.3.1 Aspects of Tests .... 5.4.9.3.2 Wood and 'Vood Based Panels in Fire .

Literature Cited.

6. Fiberboard. By Franz F. P. Kollmann.

6.0 Types of Fiberboard

6.1 History and Development

6.2 General Outline of Processes

6.3 Raw Materials 6.3.1 Wood ....... . 6.3.2 Bark ....... . 6.3.3 Modified Wood Raw Materials. 6.3.4 Non-Wood Fibrous Raw Materials

6.4 Storage of Raw Material

6.5 Raw Material Preparation . . . . . . 6.5.1 Debarking of Wood . . . . . .

II*

6.5.2 Chipping, Magnetic Separating, Screening . 6.5.3 Storing . 6.5.4 Wetting ............... .

491 493 493 497 498 502

504 507 507 507 508 508 510

512 512 513 515 517 523 523 528

528 528 530 530 531 532 532 534 535 538

551

551

552

559

565 565 569 572 573 574

575 575 578 579 580

XII Contents

6.6 Pulping (Wet Processes) 6.6.1 Mechanical Pulping. . . . 6.6.2 Chemical-Mechanical Pulping 6.6.3 Thermal-Mechanical Pulping.

6.6.3.1 General Considerations . 6.6.3.2 Asplund Process (Defribrator Method)

6.6.4 Explosion Process . . . .

6.7 Manufacture of Insulation Board 6.7.1 Sizing . . . . . . . . 6.7.2 Mat or Sheet Formation . 6.7.3 Drying . . . . . . . . . 6.7.4 Additional Processing Operations.

6.8 Manufacture of Hardboard. . 6.8.1 Sizing ... . . . . . 6.8.2 Mat or Sheet Formation

6.8.2.1 Wet Felting 6.8.2.2 Air Felting. . .

6.8.3 Hot Pressing . . . . . 6.8.4 Heat Treatment and Oil Tempering 6.8.5 Humidification and Conditioning. . 6.8.6 Trimming and Additional Processing . 6.8.7 Losses and Yield in Manufacture, Production Costs. 6.8.8 Special Fiberboards . . . . . . . .

6.9 Properties of Fiberboard . . . . . . . . 6.9.0 General Considerations, Tests, Uses 6.9.1 Density, Weight per Unit Area . . 6.9.2 Moisture Content, Absorption and Swelling 6.9.3 Thermal Conductivity 6.9.4 Acoustical Properties. . . . . 6.9.5 Mechanical Properties . . . .

6.9.5.0 General Considerations . 6.9.5.1 Elasticity. . . . . . . 6.9.5.2 Bending Strength, Creep, Fatigue

6.9.5.2.1 Bending Strength or Modulus of Rupture 6.9.5.2.2 Creep and Relaxation . . . . 6.9.5.2.3 Fatigue, Endurance. . . . .

6.9.5.3 Impact Strength, Puncture Resistance . 6.9.5.4 Tensile Strength . . . . . . 6.9.5.5 Compressive Strength . . . . 6.9.5.6 Shear Strength (Delamination) 6.9.5.7 Hardness ..... .

6.9.6 Technological Properties . . . 6.9.6.0 General Considerations . 6.9.6.1 Surface Quality. . . . 6.9.6.2 Accuracy of Dimensions, Surface Texture and Stability. 6.9.6.3 W orking, Machining, Moldability of Hardboard . 6.9.6.4 Nail- and Screw-Holding Ability.

6.9.7 Resistance to Deterioration . . . . . . 6.9.7.1 Abrasion (Wear) Resistance 6.9.7.2 Resistance to Biological Attacks 6.9.7.3 Behavior in Fire.

Literature Cited. . Conversion Factors Author Index Subject Index . ..

580 580 582 583 583 585 590

595 595 595 598 602

602 602 603 603 603 604 606 606 606 607 609

610 610 613 613 623 624 625 625 625 628 628 637 640 644 647 649 649 652 652 652 653 654 655 665 666 666 666 667 668 673 686 691