Totally updated version

Transcription

1 Papermaking Science and Technology a book series covering the latest technology and future trends Book 16 Paper Physics Second Edition Totally updated version Book editor Niskanen Kaarlo, Ph.D., President, KCL Publisher Finnish Paper Engineers Association/Paperi ja Puu Oy Paperi ja Puu Oy

2 Table of Contents 1 Paper structure Fibres and bonds Paper surface and thermal, electrical and friction characteristics Paper Optics In-plane tensile properties Structural mechanics of paper and board Moisture and fluid transport Rheology Dimensional stability Conversion factors Index

3 CHAPTER 1 Paper structure 1 Two-dimensional network Coverage Fibre segments Fibre network connectivity Three-dimensional network Thickness, density and porosity Pores in paper Formation Characterisation Fibre flocculation Forming mechanisms Mass distribution in thickness direction Fibre orientation Measurement and characterisation of fibre orientation Laminar shear on wire Hydrodynamic disturbances Orientation angle Z-directional structure Layered and felted sheet structures Two-sidedness of fibre orientation Wet straining of the paper web...51 References

4 CHAPTER 2 Fibres and bonds 1 Fibre properties Raw material effects Pulping effects Fines in pulp Mechanical properties of wet fibres Mechanical properties of dry fibres Internal stresses in paper sheet Bonding Basic concepts Molecular bonding Structure of inter-fibre bonds Bond strength...86 References

5 CHAPTER 3 Paper surface and thermal, electrical and friction characteristics 1 Surface roughness Definitions Measurement methods Sheet compressibility Effect of fibre properties Papermaking effects Friction General physical and chemical effects Friction of paper surfaces Thermal properties Introduction Mechanisms of heat transfer in paper Specific heat and thermal diffusivity Measurement methods Effect of furnish and paper structure Electrical Properties Theory Measurement Methods Resistivity of paper Dielectric properties Practical relevance of electrical properties References

6 CHAPTER 4 Paper optics 1 Introduction Optical theory Light, refractive index and Fresnel s equations Specular reflection from a rough surface Angle- and spatial-resolved measurements of gloss Diffuse reflectance from a fibre structure Standardised measurements of reflectance Standard illuminants ISO instruments for measuring diffuse reflectance and gloss Colour theory Spectral selective light absorption CIE XYZ colour space and CIELAB Colour differences and metamerism Colour appearance and colour management Traditional measurements in pulp and paper industry Brightness Y-value and opacity Whiteness Overview of paper optics values Kubelka-Munk theory Derivation of Kubelka-Munk theory Useful Kubelka-Munk equations ISO method for determination of s and k Equations for layered structures Shortcomings of the Kubelka-Munk theory Saunderson correction

7 Paper optics 7 Optics related to pulp and paper and prints Fibres and pulps Beating and wet pressing Fillers Fluorescent whitening agents and dyeing Coating and calendering Optical properties of prints Future paper optics Discrete ordinate radiative theory (DORT) Monte Carlo - Grace Model References

8 CHAPTER 5 In-plane tensile properties 1 Elasticity Elastic constants and their measurement Theory Papermaking effects through sheet density Drying stresses Elastic anisotropy and CD profiles Load-elongation behaviour Macroscopic observations Microscopic yielding phenomena Furnish and papermaking effects Triaxial deformations Tensile strength, fracture toughness and fracture energy Web breaks and fracture toughness Formation effects on tensile strength Microscopic strength mechanisms Measurement of fracture energy Furnish and papermaking effects on tensile strength Pulp mixtures References

9 CHAPTER 6 Structural mechanics of paper and board 1 Bending stiffness Basic relationships Multilayer products Practical problems related to bending stiffness Furnish and papermaking effects Compressive strength Definitions and measurement methods Significance of compressive strength Stress-strain curves in compression Fibre network in compression Furnish and papermaking effects Out-of-plane strength Out-of-plane stress-strain curve and elastic modulus Measurement methods Structural effects Ply-bond strength References

10 CHAPTER 7 Moisture and fluid transport 1 Moisture in paper Relative humidity and moisture content Hysteresis and dynamic phenomena Interactions of water with fibres Fluid transport phenomena Fluid transport in pores Transport of inert gases Diffusion of water vapour Lucas-Washburn equation X-ray microtomography Wetting and swelling in liquid penetration Superhydrophobation Swelling Applications to coating and printing References

11 CHAPTER 8 Rheology 1 Fundamentals of viscoelasticity Dynamic mechanical testing Strain rate effects in load-elongation behaviour Effect of moisture on stress-strain behaviour Creep and stress relaxation Master curves of creep Accelerated creep Stress relaxation Internal stress and drying stress Delayed recovery Microscopic mechanisms References

12 CHAPTER 9 Dimensional stability 1 Hygroexpansion General phenomena Hygroexpansion of the fibre network Drying stresses Furnish and papermaking effects Curl Characterisation and measurement methods Mechanism of curl Buckling curl Diagonal curl Cockling and fluting Characteristics of cockling Mechanisms of cockling and fluting Factors affecting cockling Dynamic dimensional changes Curl in moistening and drying References