Sustainable Barrier SBS Paperboard Coatings Using Co-Polymerized Shape Engineered Pigments" (2006)

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Dissertations Graduate College

12-2006

Sustainable Barrier SBS Paperboard Coatings Using Co- Polymerized Shape Engineered Pigments

Lokendra Pal Western Michigan University

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Recommended Citation Pal, Lokendra, "Sustainable Barrier SBS Paperboard Coatings Using Co-Polymerized Shape Engineered Pigments" (2006). Dissertations. 975. https://scholarworks.wmich.edu/dissertations/975

This Dissertation-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Dissertations by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. SUSTAINABLE BARRIER SBS PAPERBOARD COATINGS USING CO-POLYMERIZED SHAPE ENGINEERED PIGMENTS

Lokendra Pal

A Dissertation Submitted to the Faculty of The Graduate College in partial fulfillment of the requirements for the Degree of Doctor of Philosophy Department of Paper Engineering, Chemical Engineering and Imaging Dr. Margaret K. Joyce, Advisor

Western Michigan University Kalamazoo, Michigan December 2006

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 3243163

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Copyright by Lokendra Pal 2006

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGMENTS

I would like to express my gratitude to my graduate advisor, Dr. Margaret K.

Joyce, for her worthy assistance, advice, and guidance throughout the dissertation and

beyond that. I would also like to thank my committee members Dr. Paul D. Fleming,

and Dr David E. Knox, for their advice.

The collaboration between the Department of Paper Engineering, Chemical

Engineering and Imaging and MeadWestvaco Corporation made this work possible.

The financial support from MeadWestvaco during the course of this study is

gratefully acknowledged. In addition to this, the company was generous enough to

provide access to facilities at Charleston SC and Chillicothe OH.

Special thanks to Mr. Charles Ruffner, for his assistance and advice during the

course of this study. Special thanks also to Mr. Matthew Stoops, for his support

during the coating trials. Many thanks to my friends, colleagues and others who

contributed in many different ways.

Finally, my deepest gratitude and appreciation to my parents, for their love,

support, sacrifice and encouragement needed to bring this dissertation to completion.

An expression much greater than “special recognition” goes to my wife, Sapana, and

my son, Siddhant, for their endurance and constant encouragement.

Lokendra Pal

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS

ACKNOWLEDGMENTS...... ii

LIST OF TABLES...... viii

LIST OF FIGURES...... x

CHAPTER

I. INTRODUCTION...... 1

References ...... 7

H. LITERATURE REVIEW...... 13

Liquid Transport Mechani sms ...... 17

Permeability ...... 18

Diffusion ...... 19

Capillary Transport ...... 21

Surface Energy ...... 23

Nano-Composite/Structured Coatings ...... 26

Conventional and Barrier Coatings ...... 29

The Packing of Particles ...... 33

The Structure of Paper Coatings ...... 35

MacroPac Simulation Software ...... 37

References ...... 38

m. STATEMENT OF THE PROBLEM AND OBJECTIVES...... 47

IV. EXPERIMENTAL DESIGN...... 49

Materials...... 51

iii

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Coating Preparations and Application Methods ...... 53

Phase I: Conventional Pigment Polymer (CPP) Coatings 53

Phase II: Co-Polymerized (COP) Coatings ...... 57

Calendering and Conditioning of Samples ...... 60

Testing and Instruments ...... 60

Appendix ...... 64

Particle Size Analysis of Co-Polymerized (COP) Coatings ...... 64

V. SHAPE ENGINEERED PIGMENTS BASED BARRIER COATINGS FOR SBS PAPERBOARD...... 65

Abstract ...... 65

Introduction ...... 66

The Structure of Clay Minerals...... 68

Effect of Relative Humidity and Temperature on Paperboard Properties ...... 70

Experimental Design ...... 71

Materials...... 71

Coating Formulations and Application Methods ...... 73

Calendering and Conditioning of Samples ...... 74

Testing ...... 74

Results and Discussion ...... 76

Coatings ...... 76

Pigments ...... 76

Application Methods ...... 77

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Conclusions ...... 82

References ...... 83

Appendix ...... 87

Microphotograph Using Scanning Electron Microscopy (SEM)...... 87

VI. HIGH BARRIER SUSTAINABLE CO-POLYMERIZED COATINGS...... 89

Abstract ...... 89

Introduction ...... 90

Experimental Design ...... 95

Materials...... 95

Coating Formulations and Application Methods ...... 97

Calendering and Conditioning of Samples ...... 98

Testing ...... 98

Results and Discussion ...... 100

Wet and Dry Coating Properties ...... 100

Barrier Properties ...... 101

Surface and Optical Properties ...... 103

Conclusions ...... 115

References ...... 116

Appendices ...... 118

A. 3D Topography of COP Coatings Using WYKO White Light Interferometry ...... 118

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B. WVTR Results of COP Coated Samples at Different Environmental Conditions ...... 122

C. PPS Porosity & Permeability Results of COP Coated Samples ...... 124

D. Surface and Optical Properties Measurement Results of COP Coated Samples ...... 126

E. Statistical Analysis of WVTR Results ...... 129

F. COP Screening Data ...... 142

VE. FLEXURAL STIFFNESS (3 -POINT BENDING) OF THE SBS PAPERBOARD COATED WITH HIGH BARRIER SUSTAINABLE COP COATINGS...... 143

Abstract ...... 143

Introduction ...... 144

Experimental Design ...... 146

Materials...... 147

Coating Formulations and Application Methods ...... 148

Calendering and Conditioning of Samples ...... 149

3 Point Bending Test Procedure ...... 149

Results and Discussion ...... 153

Conclusions ...... 161

References ...... 162

Appendices ...... 164

A. Analysis of Variance (ANOVA) of COP Coated Samples Using Design-Expert ...... 164

B. 3-Point Bending Test Results of COP Coated Samples 166

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C. Statistical Analysis of 3-Point Bending Load Results ...... 174

Vm. A SIMPLE METHOD FOR CALCULATION OF THE PERMEABILITY COEFFICIENT OF POROUS MEDIA ...... 187

Abstract ...... 187

Introduction ...... 188

Difference Between Permeability and Porosity ...... 188

Darcy’s Law ...... 189

Experimental Design ...... 191

Materials...... 191

Testing ...... 193

Procedure ...... 193

Coatings for SBS Paperboard ...... 196

Coatings for Unbleached Kraft Paper ...... 197

Results and Discussion ...... 199

Results for SBS ...... 199

Results for Unbleached Kraft ...... 201

Conclusions ...... 203

References ...... 204

IX. CONCLUSIONS...... 207

Appendix ...... 211

Additional CLC Study ...... 211

vii

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES

4.1 The Physical Properties of Shape Engineered Pigments ...... 51

4.2 The Characteristics of the Binders ...... 52

4.3 The Characteristics of the Uncalendered Baseboard Substrates (Stdev. in Parenthesis) ...... 52

4.4 Experimental Design for CPP Coatings for the Size Press Application Using M initab ...... 55

4.5 Experimental Design for CPP Coatings for the Rod Application Using M initab ...... 56

4.6 Experimental Design for CPP Coatings for the Blade Application Using Minitab ...... 56

4.7 Experimental Design for COP Coatings for the Rod Application Using M initab ...... 58

4.8 The Characteristics of the COP Coatings for Rod Application ...... 59

4.9 Experimental Design for COP Coatings for the Blade Application Using M initab ...... 59

4.10 The Characteristics of the COP Coatings for Blade Application ...... 60

4.11 Operating Conditions of CLC Coater ...... 60

4.12 Description of Different Tests Used for Coating Characterization ...... 61

5.1 The Characteristics of the Mineral Pigments ...... 72

5.2 The Characteristics of the Binders ...... 72

5.3 The Characteristics of the Base Substrates (Stdev. in Parenthesis) 72

5.4 Sample IDs for Different Formulations and Applications ...... 75

5.5 Comparison of Barrier and Mechanical Properties of Selected Samples for Different Coating Methods...... 78

6.1 The Characteristics of the Control Binder ...... 95

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6.2 The Characteristics of the Mineral Pigments ...... 96

6.3 The Characteristics of the Base Substrates (Stdev. in Parenthesis) 96

6.4 The Characteristics of the COP Coatings ...... 97

6.5 Operating Conditions of CLC Coater ...... 98

6.6 Sample IDs for Different Formulations and Substrates ...... 100

7.1 The Characteristics of the Uncalendered Baseboards (Stdev. in Parenthesis) ...... 147

7.2 The Characteristics of the Control Binder Used for COP Coatings 148

7.3 The Characteristics of the Mineral Pigments Used for COP Coatings 148

7.4 The Wet Coating Characteristics of the COP Coatings ...... 149

7.5 Sample IDs for Different COP Coatings and Substrates ...... 153

7.6 Design Summary and Analysis of Variance (ANOVA) of COP Coated Samples Using Design-Expert ...... 156

8.1 The Characteristics of the Binder ...... 192

8.2 The Characteristics of the Mineral Pigments ...... 192

8.3 The Characteristics of the Base Substrates ...... 192

8.4 Impregnator Coater and Size Press Pickups and Application Conditions...... 193

8.5 Permeability Coefficient of Model Papers ...... 195

8.6 Influence of Pigments Aspect Ratio on PPS Porosity and Permeability Coefficient ...... 200

8.7 Impregnator Influence of Saturation Treatment on PPS Porosity and Permeability Coefficient of Different Samples ...... 202

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES

2.1 SBS Baseboard Microphotograph at Different Magnifications Using Scanning Electron Microscopy (SEM) ...... 14

2.2 Cell Wall Structure of the Wood Fiber ...... 15

2.3 Effect of Moisture Content on Glass Transition Temperature (Tg) of Cellulose, Hemicellulose and Lignin ...... 17

2.4 Components of Interfacial Tension and Contact Angle ...... 26

2.5 Shape Engineered Pigments SEM Microphotographs ...... 27

2.6 Barrier Properties-Tortuous Path for a Particle to Migrate Through a Layer of Clay Platelets ...... 29

2.7 Clay Mineral Structure ...... 32

2.8 Calculating Disc Diameter from ESD and Shape Factor Measurements ...... 32

2.9 Example of TEM Shadowing Techniques to Measure Shape Factor 33

2.10 (a) Face Centered Cubic (fee) & (b) Hexagonal Close Packing (hep) 34

2.11 (a) & (b) Tetrahedral Site and (c) & (d) Octahedral Site ...... 34

2.12 Particle Packing Using MacroPac (3D Visual) ...... 38

5.1 Tortuous Path for Water Molecules to Migrate Through a Layer of Clay Platelets ...... 68

5.2 Clay Mineral Structure ...... 69

5.3 Effect of Moisture Content on Glass Transition Temperature (Tg) of Cellulose, Hemicellulose and Lignin ...... 71

5.4 Influence of Pigments Shape Factor on PPS Porosity of Selected Coated Samples...... 79

5.5 Influence of Pigments Shape Factor on Permeability of Selected Coated Samples ...... 79

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5.6 Influence of Pigments Shape Factor on WVTR at 81 %RH & 100°F of Selected Coated Samples ...... 80

5.7 Influence of Pigments Shape Factor on Elastic Modulus at 75%RH & 73°F of Selected Samples s ...... 80

5.8 Comparison of Elastic Modulus at 50 and 75%RH and 73°F of Selected Rod Coated Samples ...... 81

5.9 Influence of Shape Factor (SF) and Plate Thickness (T) (Coat Wt. -32 gsm) on Barrier Properties for Pigments Only (No Binder) ...... 81

5.10 Influence of Application Method (Size Press vs. Rod Coating and Double Coat) on Barrier Properties ...... 82

6.2 HSFE Clay Platelets Scanning Electron Microphotographs ...... 93

6.3 Comparison of Conventional Pigment Polymer (CPP) Coatings: Phase Separated Microcomposites and In-situ Polymerized (COP) Coatings: Intercalated and Exfoliated Nanocomposites ...... 93

6.4 Comparison of Coating Coverage of COP Coated Samples ...... 104

6.5 Comparison of Roughness Parameters (Ra, Rq & Rt) Using WYKO White light Interferometry ...... 105

6.6 Comparison of WVTR at 81 % RH& 100°F of COP Coated Uncalendered Samples Using Pre-coated Baseboard ...... 105

6.7 Comparison of WVTR at 81% RH&100°F of COP Coated Calendered (600 PLI) Samples Using Pre-coated Baseboard ...... 106

6.8 Comparison of WVTR at 81% RH&100°F of COP Coated Calendered (1600 PLI) Samples Using Pre-coated Baseboard ...... 106

6.9 Comparison of WVTR at 75% RH&73°F of COP Coated Uncalendered Samples Using Pre-coated Baseboard ...... 107

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. List of Figures—continued

6.10 Comparison of WVTR at 75% RH&73°F of COP Coated Calendered (600 PLI) Samples Using Pre-coated Baseboard ...... 107

6.11 Comparison of WVTR at 75% RH&73°F of COP Coated Calendered (1600 PLI) Samples Using Pre-coated Baseboard...... 108

6.12 Comparison of WVTR at 81% RH&100°F of COP Coated Uncalendered Samples with Non Pre-coated Baseboard ...... 108

6.13 Comparison of WVTR at 81% RH&100°F of COP Coated Calendered (600 PLI) Samples with Non Pre-coated Baseboard ...... 109

6.14 Comparison of WVTR at 81% RH&100°F of COP Coated Calendered (1600 PLI) Samples with Non Pre-coated Baseboard 109

6.15 Comparison of WVTR at 75% RH&73°F of COP Coated Uncalendered Samples with Non Pre-coated Baseboard ...... 110

6.16 Comparison of WVTR at 75% RH & 73°F of COP Coated Calendered (600 PLI) Samples with Non Pre-coated Baseboard ...... 110

6.17 Comparison of WVTR at 75% RH & 73°F of COP Coated Calendered (1600 PLI) Samples with Non Pre-coated Baseboard ...... I l l

6.18 Comparison of Permeability Coefficient of COP Coated Samples at Different Calendering Using Pre-coated Baseboard ...... I l l

6.19 Comparison of Permeability Coefficient of COP Coated Samples at Different Calendering Using Non Pre-coated Baseboard ...... 112

6.20 Comparison of PPS Roughness of COP Coated Samples at Different Calendering Using Pre-coated Baseboard ...... 112

6.21 Comparison of PPS Roughness of COP Coated Samples at Different Calendering Using Non Pre-coated Baseboard ...... 113

6.22 Comparison of Brightness of COP Coated Samples at Different Calendering Using Pre-coated Baseboard ...... 113

6.23 Comparison of Brightness of COP Coated Samples at Different Calendering Using Non Pre-coated Baseboard ...... 114

xii

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6.24 Comparison of 75° Gloss of COP Coated Samples at Different Calendering Using Pre-coated Baseboard ...... 114

6.25 Comparison of 75° Gloss of COP Coated Samples at Different Calendering Using Non Pre-coated Baseboard ...... 115

7.1 Effect of Moisture Content on Glass Transition Temperature (Tg) of Cellulose, Hemicellulose and Lignin ...... 145

7.2 Three Point Bending Test Setup ...... 150

7.3 Comparison of Loss in Bending Load of Different Samples at 50 and 81% Humidity ...... 155

7.4 Comparison of Flexural Modulus at 50% RH& 73°F of COP Coated Uncalendered Samples Using Pre-coated Baseboard ...... 157

7.5 Comparison of Flexural Modulus at 81% RH & 100°F of COP Coated Uncalendered Samples Using Pre-coated Baseboard ...... 157

7.6 Comparison of Flexural Modulus at 50% RH & 73°F of COP Coated Uncalendered Samples Using Non Pre-coated Baseboard ...... 158

7.7 Comparison of Flexural Modulus at 81% RH & 100°F of COP Coated Uncalendered Samples Using Non Pre-coated Baseboard ...... 158

7.8 Comparison of Flexural Modulus at 50% RH & 73°F of COP Coated Calendered Samples Using Pre-coated Baseboard ...... 159

7.9 Comparison of Flexural Modulus at 81% RH & 100°F of COP Coated Calendered Samples Using Pre-coated Baseboard ...... 159

7.10 Comparison of Flexural Modulus at 50% RH & 73°F of COP Coated Calendered Samples Using Non Pre-coated Baseboard ...... 160

7.11 Comparison of Flexural Modulus at 81% RH & 100°F of COP Coated Calendered Samples with Non Pre-coated Baseboard ...... 160

8.1 Comparison of Permeability Coefficients and PPS Porosities of Model Papers ...... 196

8.2 Influence of Impregnator Pond Pressure on Coating Pickups...... 199

xiii

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8.3 Influence of Pigments Aspect Ratio on PPS Porosity and Permeability Coefficient ...... 201

8.4 Influence of Pigment Loading (14% Pickup (dry/dry)) on PPS Porosity and Permeability Coefficient of Size Press and Impregnator Treated Papers ...... 203

xiv

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 CHAPTER I

INTRODUCTION

This work has merit in developing sustainable barrier SBS paperboard

coatings using shape engineered pigments and a co-polymerization process. Barrier

coatings are used for food packaging, quick-service wares (paper cups and plates) and

numerous other applications where a product must be protected from the ambient

environment, or vice versa [1-4]. The barrier package system depends on the nature of

the contents or products, preservation methods, and the availability of barrier

packaging materials [1-5]. Barrier packaging materials can be classified as rigid or

flexible. Ceramics and metals are used for rigid packaging. Petroleum based

unsustainable products [6-10] such as low-density polyethylene (LDPE), high-density

polyethylene (HDPE), polypropylene and polyethylene terephthalate (PET), and wood

fiber based sustainable materials such as paper and paperboard [4,11] are used for

flexible packaging.

The barrier package is a composite system of several layers of different

substrates and coatings. The barrier package includes not only the obvious materials

and coatings necessary for barrier properties, but also those needed for the printing

inks and coatings to facilitate them. This is because most packages contain decorative,

informative, or label printing [11] such as barcodes and RFID [11-16] tags for

consumer appeal, logistic and operational convenience. In addition, the package

contents may be solid, liquid, or gases or mixtures of these components.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Barrier coated packaging is an extremely large and important area of interest

to industry [1,2,17,18], government [19], and consumers [1,2]. It is expected to grow

rapidly as industry expands its offerings of ethnic and specialty foods, nutraceuticals

and functional foods, extended shelf life products [20-22], and convenience foods and

products and serving wares [3,23] such as cups and plates. Consumers are demanding

longer shelf life [20-22], safety [19], and added value packaged products [24]. To

package these products, there is a need for sustainable barrier systems [25].

The need to reduce the amount of non-recyclable barrier materials is growing

[1,2]. Solid bleached sulfate (SBS) paperboards manufactured from cellulosic wood

fibers fulfill many of the requirements of primary recycling since cellulose is

biodegradable. The fibers are a key constituent of any board-based packaging and

provide desired structural rigidity to the package. In wood, fibers are composed of

semi-crystalline cellulose microfibrils, surrounding amorphous hemicellulose, and a

lignin matrix. In packaging board, fibers form a layered network structure along with

fillers and other additives [4]. SBS is a premium paperboard grade that is produced

from fully bleached virgin kraft pulp (sulfate process) fiber. The major markets for

SBS are folding cartons such as milk and juice cartons and recyclable food serving

products such as paper cups, plates, and food containers [3,4].

Packaging made from SBS paperboards has therefore been extensively used to

contain perishable products. Unfortunately, due to the high gas permeability and

hydrophilicity of cellulosic fibers, perishable and liquid products cannot be contained

in simple paperboard containers. To overcome these difficulties, paperboard packages

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. are commonly extrusion coated off-line with unsustainable petroleum based products

[5,7-10] to improve barriers against water, water vapor, and gasses [26-31]. Above

all, the recycling of petroleum based products coated on SBS paperboard is extremely

difficult. Due to the above concerns and desires, dispersion coatings with inorganic

and organic materials are gaining a widespread interest to improve barriers against

permeation of water, water vapor and gases [5,32-36].

The barrier properties achieved depends on pigments types, shape factor,

particle size and distribution and orientation of particles, binder types, hydrophobic

and hydrophilic character of binders, application methods, drying conditions and any

finishing operations such as calendering [37-50]. The mechanical properties depends

on baseboard, pigment and binder types, coating thickness, and calendering

operations [4,11,51,52].

One area that encompasses many of these factors is the development,

application, characterization and optimization of sustainable barrier coatings for SBS

paperboard, particularly with respect to the water, water vapor and gas permeation.

This point is the subject of the current study. The broader objective of this study is to

gain knowledge of the coating materials, preparation and application methods to

develop sustainable barrier package system. The shape engineered pigments [53,54]

were used to develop co-polymerized coatings for sustainable SBS barrier package.

Relationship between coating structure and barrier and mechanical properties were

determined. A new method for the calculation of permeability coefficient of porous

media was also developed.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. This research includes the following papers as journal articles referred to as

Paper I-IV in the text: (I) Shape Engineered Pigments Based Barrier Coatings for SBS

Paperboard, (II) High Barrier Sustainable Co-Polymerized Coatings, (El) Flexural

Stiffness (3-Point Bending) of the SBS Paperboard Coated with High Barrier

Sustainable COP Coatings, and (IV) A Simple Method for Calculation of the

Permeability Coefficient of Porous Media.

Phase one deals, first with screening of different shape engineered pigments

and binders using a laboratory size press, rod drawdowns and particle packing

simulation using MacroPac [55,56] software and then with optimization of selected

barrier coatings. The effect of pigment type, shape factor, platelet thickness, particle

packing, particle size and distribution and binder particle size, glass transition

temperature (Tg) and hydrophilic and hydrophobic character on barrier and

mechanical properties were studied. The pigment shape factor appears to have a

systematic effect on barrier properties although it is relatively small in some cases.

The shape factor significantly impacted the saturation coat weight (where complete

coverage occurs).

The medium shape factor pigment (SF -50-60) with thinner platelet provided

the highest barrier properties for the 14 pt SBS board tested. The 100 % acrylic based

hydrophobic binder gave better barrier properties compared to styrene butadiene

based binder. The double-coated treatment method (size press/rod) produced the best

results. The effect of application method on barrier properties was found to have a

more significant impact on the barrier properties than the SF of the pigment. There

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. was only a slight impact of pigment shape factor and application method on stiffness.

Further, shear rate effect on selected pigment particles orientation were studied using

a cylindrical laboratory coater (CLC) at different speeds.

Phase two deals, first with the development of co-polymerized coatings using

shape engineered pigments then with the application, characterization and

optimization using laboratory rod drawdowns and CLC blade coating. Acrylic co

monomers, were polymerized with addition of three different, finely dispersed

modified shape engineered clays, to create nanostructured co-polymerized coatings.

The nanostructured coatings were obtained through intercalation of the polymer at

three different pigment loadings (5, 30, and 55 %). The particle size analysis showed

a nanocomposite structure. The co-polymerized nanostructured coatings pose

interesting opportunities for exploiting property enhancements, due not only to the

large pigment-polymer contact surface area, but also from geometric confining factors

that induce a preferred orientation of the pigment particle platelets. Such orientation

effects generated unique property enhancements, such as gas/vapor barrier properties.

The coatings were studied to elucidate the relationship between their structure

and barrier properties. The effects of pigment shape, baseboard, coat weight,

calendering and relative humidity and temperature on barrier properties were studied

through full factorial design of experiment (DOE). All of the studied factors showed a

significant impact on barrier properties. Additionally, surface and optical properties of

the coatings were studied. In today’s age of point of purchase (POP) retailing to

attract consumers, a package’s appearance is used to sell the product [57]. Thus, it is

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. important that the final packaged product looks good. In virtually all cases,

paperboard used to produce a commercial package represents an image. To account

for this need, the optical and surface properties of the developed coatings were also

quantified and compared.

Phase three deals, with the characterization of mechanical [58-60] behavior of

co-polymerized nanostructured coatings under high humidity and temperature. The

bending load and stiffness of SBS paperboard, blade coated with these coatings was

determined using the three point bending test. This study was carried out to determine

the environmental (RH and temperature) impact on bending force, flexural stiffness

and bending deflection of various SBS coated paperboards, coated with barrier

coatings. The mechanical properties of coated samples were studied through a full

factorial design of experiment (DOE) and the relationship between these coatings,

baseboards, fiber orientations, pigment shape factor, calendering and the mechanical

properties at different humidities and temperatures were investigated. The flexural

stiffness of a coated SBS board is mainly dependent on the baseboard. The ability of

the barrier coating to protect the baseboard against water and water vapor permeation

is the key in retaining the mechanical properties of a package, especially at high

humidity and temperature.

Phase four deals, with the development of a new method for the calculation of

the permeability coefficient of porous media. A simple method for calculation of the

permeability coefficient of porous media is described. The permeability coefficient

may be calculated by Darcy’s equation [61] using the Parker Print Surf porosity

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (which is primarily sensitive to air permeability) [62-65]. The permeability coefficient

may be used for ranking porous media in fluid absorption and spreading rate and for

estimation of pore size. Likewise, the coating thickness required for given barrier and

printing performance may be estimated.

References

1. Charles P. Klass, “Emerging Barrier Coating Market Trends ”, Barrier Coating Symposium, Western Michigan University Kalamazoo, MI, Oct. 8-9, 2002, Kalamazoo, MI.

2. Charles P. Klass, “Market Trends”, Barrier Coating Symposium, Oct. 12-13, 2004, Kalamazoo, MI.

3. Shanton, Kenneth J., “Plate Stock”, US Patent 5776619, July 1998

4. J. Kline, “ Paper and Paperboard”, 2nd Ed., Miller Freeman Publishing, San Francisco, 1991.

5. Jurkka Kuusipalo, “Characterization and Converting of Dispersion and Extrusion CoatedHD-Papers”, TAPPI, 2003 PFFC

6. Halle, R. W., and Simpson, D. M., “A New Enhanced Polyethylene for Extrusion Coating and Laminating”, TAPPI 2003 PFFC

7. Davey, C.R., and Kurzbuch, W., “LLDPE for Extrusion Coating”, TAPPI 1998 P,L&C Conference Proceedings”, August 1988

8. Potts, M.W., and Pope, T. J., “Extrusion Coatings vs. Lamination: How Affinity* Poly olefin Plastomers Will Offer More”, TAPPI 1997 P,L&C Conference Proceedings, August 1997

9. Schwarz, P., Mahlke, M., “Polyamide Nanocomposites for Extrusion Coating Applications ”, From the conference proceedings of 2003 TAPPI Eur. PLACE Conf. 2, pp. 1451-1480(2003).

10. Krook, M., Gallstedt, M., Hedenqvist, M.S., “A Study on Montmorillonite/ Polyethylene Nanocomposite Extrusion-Coated Paperboard \ Packaging Technol. Sci. 18(1), pp. 11-20(2005).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 11. D. Twede and S. E. M. Selke, Cartons, Crates and Corrugated Board: Handbook of Paper and Wood Packaging Technology, DEStech, Lancaster, PA, 2005.

12. Clarke, R., 2003, “Practical Issues for Implementing RFID in Grocery Supply Chains," Intelligent & Smart Packaging, PIRA International, Leatherhead, Surrey, England.

13. Clarke, R., 2002, “Radio Frequency Identification on One-Way Packages”, Dimensions.02 Proceedings, The International Conference on Transport Packaging, International Safe Transit Association and Institute of Packaging Professionals, pp. 311-321.

14. Clarke, R., 2002, “Radio Frequency Identification: Will it Work in Your Supply Chain?” WorldPak 2002: Improving the Quality of Life Through Packaging Innovation, CRC Press, Baca Raton FL, Book 2, pp. 654-662.

15. Vorst, Keith, “ Development of a Material Testing Protocol for Evaluation of Radio Frequency Transponder Effect on Bloom Time of Beef Loin Muscle”, Masters Thesis, Michigan State University, 2002.

16. Clarke, R. 2001, “Radio Frequency Identification: Smart or Intelligent Packaging?" The Journal of Packaging Science and Technology, Japan, Vol. 10, No. 5, pp. 233-247. Invited paper and presentation.

17. J. McCracken and V. Bell, “ Worldwide Environmental Packaging Mandates”, Barrier Coating Symposium, Western Michigan University Kalamazoo, ML Oct. 8-9, 2002.

18. J. McCracken, “Worldwide Environmental Packaging Mandates”, International Association of Packaging Research Institutes (IAPRI)-WORLDPAK Conference. East Lansing, Michigan, June 23-28,2002.

19. USFDA, “Unavoidable Contaminants In Food For Human Consumption And Food-Packaging Material”, Code of Federal Regulations, Title 21, Volume 2, Chapter 1, Part 109, 2002.

20. R. Alves and S. Jaime, “Stability of ‘Reqeijao Cremoso’ in Difference Packages at Dark Storage”, International Association of Packaging Research Institutes (IAPRI)-WORLDPAK Conference. East Lansing, Michigan, June 23-28, 2002.

21. G. Mortwnsen and J. Sorensen, “Reduction of Photo-oxidative Quality Changes in Cheeses by Proper Packaging”, International Association of Packaging Research Institutes (IAPRI)-WORLDPAK Conference. East Lansing, Michigan, June 23-28, 2002.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9 22. A. Begin and Sean Bouchard, “ Control of the Effect of Ethylene on Maturation of Tomatoes Packed in Modified Atmosphere. Initiation of Oxygen, Carbon Dioxide and Ethylene and Mathemetical Model Development”, International Association of Packaging Research Institutes (IAPRI)-WORLDPAK Conference. East Lansing, Michigan, June 23-28, 2002.

23. Schulz, R., "In-plant tray forming", 1992 Polymers, Laminations & Coatings Conference Proceedings

24. P. Joshi, “Active Plastics Packaging”, International Association of Packaging Research Institutes (IAPRI)-WORLDPAK Conference. East Lansing, Michigan, June 23-28, 2002.

25. Kurt Boyd, “Sourcing Strategy for Sustainable Packaging and Coatings”, SAM’S CLUB, 2006 WMU Barrier Coating Symposium, Kalamazoo, MI, USA

26. Lucas R., “Uber das Zeitgesetz des Kapillaren Aufstiegs von Flussigkeiten”, Kolloid - Z., 23:15(1918).

27. Washburn E. W.: “ The Dynamics of Capillary Flow ”, Phys. Rev., 17: 273 (1921).

28. Dullien, F. et al., “ Porous Media, Fluid Transport and Pore Structure”, Academic Press Inc., Second Edition, San Diego, 1992.

29. Gane et al., “Fluid Transport into Porous Coating Structures: Some Novel Findings”, Tappi J. 83 (5): 77 - 78 (2000)

30. M. Joyce and T. Joyce, “Practicalities of Using Impregnation (Controlled Penetration Sizing Method) for Improving the Barrier and Strength Properties of Linerboard”, Invited Speaker, Internal and Surface Sizing PIRA Conference, Graz, Austria, 2003.

31. M. Joyce and T. Joyce, “ Nanoparticle Barrier-Coated Substrate and Method for Making the Same”, US Patent 6,942,897 Sept. 13, 2005.

32. Schuman, T. et al., “Characteristics of Pigment-filled Polymer Coatings on Paperboard”, Progress in Organic Coatings 54 (2005) 360-371

33. Vaha-Nissi, M., Lahti, J., Savolainen, A., Rissa, K., and Lepisto, T., “New water- based barrier coatings for paper and paperboard”, Appita Journal, 54(2): 106(2001).

34. Vaha-Nissi, M., Savolainen, A., Talja, M., and Moro, R., “Dispersion Barrier Coating of High Density Base Papers”, 1998 TAPPI Coating Conference Proceedings.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 35. Rissa, K., Vaha-Nissi, M., Lepisto, T., and Savolainen, A., “ Talc-filled water- based barrier coatings”, Paper and Timber, 84(7):467(2002).

36. Kan, C. S., Kim, L. H., Lee, D. I., and van Gilder, R. L., “Viscoelastic Properties of Paper Coatings: Structure/Property Relationship to End Use Performance ”, TAPPI Coating Conference Proceedings, pp. 49-60.

37. T. C. Bissot, “Performance of High-Barrier Resins with Platelet-Type Fillers; Effect of Platelet Orientation ”, in Barrier Polymers and Structures, American Chemical Society, 1990.

38. Risio, S. D., and Yan, N., “ Effect of Pigment Properties on Coating Structure as Measured by AFM ”, 2005 TAPPI Coating and Graphic Arts Conference, Toronto, Canada

39. Hostetler et al., “ Drying for Optimum Binding Strength in SBS Paperboard”, 2005 TAPPI Coating & Graphic Arts Conference, Toronto, Canada

40. Kawamukai, T., Ishii, E., Yagi, H., “Moisture Permeation Mechanism of Latex Films Filled with Platelike Fillers”, 2001 TAPPI JOURNAL, Vol. 84(3), March 2001.

41. Bernard et al., “ Polyamide Nanocomposites with Oxygen Scavenging Capability ”, US Patent 6777479, Aug 2004

42. Adur et al., “Clay-Filled Polymer Barrier Materials for Food Packaging Applications”, US Patent 6358576, March 2002

43. Turner et al., “ High Barrier Amorphous Polyamide-Clay Nanocomposite and a Process For Preparing Same”, United States Patent 6417262, July 2002

44. Gilmer et al., “Polymer/Clay Nanocomposite Having Improved Gas Barrier Comprising a Clay Material With a Mixture of Two or More Organic Cations and a Process for Preparing Same”, United States Patent 6486253, November 2002

45. Cavagna, Giancarlo A.; Claytor, Robinson C., “ Barrier Coating to Reduce Migration of Contaminants From Paperboard, United States Patent 5153061, October 1992.

46. Ruf, W.; Bachler, J., “ Method for Reducing the Water Vapor Permeability of Paper”, US Patent 5358790, Oct 1994

47. http://www.nanocor.com/nanoclays.asp

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 48. Nilsson, L., Wilhelmsson, B., and Strenstrom, S., “ Drying Technology", 11(6): 1205 (1993)

49. Z. R. Zang, R. W. Wygant, A. V. Lyons and F. A. Adamsky, “How Coating Structure Relates to Performance in Coated SBS Board: A Fundamental Approach ”, 1999 Coating Conference, TAPPI Proceedings.

50. Peel, D. P., Paper Science and Paper Manufacture, 1999 Vancouver: Angus Wilde Publication.

51. Kim-Habermehl et al., “Coated Paper Stiffness: A Practical Perspective” , 2000 International Printing & Graphic Arts Conference Proceedings

52. Okomori, K. and Enomae, T., “Evaluation and Control of Coated Paper Stiffness”, 1999 Coating Fundamentals Symposium Proceedings

53. Iyer, R., “Advances in Pigment Technology”, 2005 TAPPI Coating and Graphic Arts Conference, Toronto, Canada

54. Meizanis, P., “Obtaining Liquid and Gas Barriers With Engineered Pigments”, 2006 WMU Barrier Coating Proceedings, Kalamazoo, MI, USA

55. OxMat, “MacroPac Version 5,” 2004 Intelligensys Ltd.

56. Lyons, A.V. and Iyer, R.R., “Use of Particle Packing Modeling with Lognormal Particle Size Distributions to Develop a Strategy to Improve Blade Coating Runnability”, TAPPI Coating and Graphic Arts Conference, May 16-19, 2004 , Baltimore, Maryland, USA

57. W. Soroka, "Package printing and decoration", Fundamentals of Packaging Technology; Institute of Packaging Professionals, Herndon VA, pp85-110, 1995.

58. Mark, E. R. et al., “Handbook of Physical Testing of Paper”, Marcel Dekker, Inc., 2nd Ed. Vol. 1, 2002, New York, USA

59. Kaarlo Niskanen, “Papermaking Science and Technology”, Paper Physics, 1998 Helsinki, Finland.

60. Kim-Habermehl et al., “Coated Paper Stiffness: A Practical Perspective”, 2000 International Printing & Graphic Arts Conference Proceedings

61. Darcy, H., “Les Fontaines Publiques de la Ville de Dijon”, Dalmont, Paris, (1856).

62. Parker, J. R., Paper Technology, 6 (2): T32 - T36 (1965).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 63. Parker, J. R., TAPPI, 54 (6): 943 - 949 (1971).

64. Parker, J. R., Paper Technology, 12 (3): T109 -T 1 13(1971).

65. Parker, J.R., Printing Technology, 18 (3): 7 - 11 (1974).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13 CHAPTER II

LITERATURE REVIEW

Paper and paperboard packages made from sustainable [1-3] wood fibers are

increasingly being modified and improved for better performance. The mechanical

and barrier characteristics are the important properties for package performance [4-

15]. Wood fibrous substrates, however, has a poor resistance to penetration by water,

water vapor, gasses, oils and greases [4,7,9,10,16]. Adsorption and absorption of

water and water vapor have repercussions with respect to the barrier and mechanical

properties of the paperboard system [4-15]. To improve the water and water vapor

barrier resistance and to maintain structural integrity of the package, fibrous substrates

such as solid bleached sulfate (SBS) baseboard have been coated with variety of

materials [17-22]. Unfortunately, the most common materials such as petroleum

based products (polyethylene, polypropylene and polyethylene terephthalate, etc.)

used for extrusion coatings off-line on to the SBS board are unsustainable. [17-22].

Above all, the recycling and repulpability of these extrusion coated paperboard

package is extremely difficult.

Thus, a great desire by package manufacturers, retailers and consumers to

reduce/ limit the use of petroleum based products has created a large and expanded

need for research and development of environmentally friendly barrier coatings [1-4,

23,24], However, most of the developed coatings were targeted for low to medium

humidity and temperature applications [25-32], The current research explored the use

of shape engineered pigments [33] and the co-polymerization process to develop cost

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. effective nanostructured coating that can provide a barrier to the SBS board under

high humidity and temperature applications.

SBS baseboard manufactured from cellulosic fibers fulfills many of the

requirements of primary recycling since cellulose is biodegradable. SBS baseboard is

a complex material and is mainly composed of wood fibers (cellulose and

hemicellulose), [4-8] fillers (clays, carbonates, etc.), [4-6] and various additives

(sizing agents, retention aids, etc.) [4,5]. Scanning electron microphotograph of SBS

baseboard at different magnifications is shown in Figure 2.1.

Figure 2.1. SBS Baseboard Microphotograph at Different Magnifications Using Scanning Electron Microscopy (SEM)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SBS baseboard properties depend on the fiber types and extent of fiber-fiber

bonding, as well as, on the network structure [4-8]. The cellulosic fibers are a key

constituent of any board-based packaging and provide desired structural rigidity to the

package. In wood, fibers are composed of semi-crystalline cellulose fibrils,

surrounded by amorphous hemicellulose in a lignin matrix [4-8,34-36]. A cell wall

structure of wood fiber showing primary and secondary walls with different fibril

angles (angle between the fibril direction in the S2 layer and the longitudinal axis of

the wood fiber, which typically ranges between 15° and 30°) is shown in Figure 2.2.

Figure 2.2. Cell Wall Structure of the Wood Fiber [5]

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Crystalline cellulose chains possess a regular chemical structure with highly

ordered arrangement of their segments. Polymers with high crystallinity usually are

less permeable because their ordered structure has fewer holes through which liquid

and gases including water vapor may pass [34,35]. These semi-crystalline polymers

possess their solid state until they reach their melting temperature (Tm). Amorphous

polymers such as hemicellulose do not possess ordered structure. The molecular

segments in amorphous hemicellulose or the amorphous domains of semi-crystalline

cellulose are arranged randomly and are intertwined. Therefore, amorphous polymers

do not exhibit a distinctive Tm or X-ray patterns [34,35]. Amorphous polymers, below

their glass transition temperature (Tg), are stiff and glassy. As temperatures increase

close to Tg„ the polymers soften due to coordinated molecular motions of segments of

polymer chains. Above Tg, the mobility of molecular segments of chains is sufficient

that the polymers can flow as highly viscous liquids. The glass transition temperature

is a type of second order transition.

Wood polymers have a very high glass transition or softening temperature in

the dry state. Adsorbed water and water vapor reduces the glass transition temperature

(Tg) due to the plasticization effect as shown in Figure 2.3 [36]. The fibers swell or

expand anisotropically in the transverse (perpendicular) direction to the cellulosic

fiber axis, which tends to increase the fibril angle. This in-tum affects the mechanical

properties such as elastic modulus and the stiffness of wood fibers [11,36-38].

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 17

250 i

Disordered U 200

00 Hemicelluloses Lignin

0 10 20 30 40 50 60 Moisture Content (%)

Figure 2.3. Effect of Moisture Content on Glass Transition Temperature (Tg) of Cellulose, Hemicellulose and Lignin [36]

Liquid Transport Mechanisms

Liquid transport phenomena in porous media can be separated in to (1)

saturated viscous flow, (2) diffusion, and (3) capillary (liquid) flow. A porous

medium such as paper and paperboard is macroscopically heterogeneous. Paper media

contain small open spaces and voids in between the fibers distributed throughout a

solid fiber matrix [4,6,16,39]. Although most solids have small interstitial spaces of

the size of the molecules, which can be penetrated by diffusion, pores in paper media

have a larger size. Generally, a close relationship exists between the pore structure of

a paper media and many of its macro and microscopic properties. Microscopic

properties describe the shape, size and connectivity of the pores [39,40]. Macroscopic

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. properties of porous media are the porosity, the specific surface area and the

permeability. The permeability describes the conductivity of a porous medium with

respect to fluid flow [16,39]. Permeability is the most important physical property of a

porous medium, while the porosity is its most important geometrical property. The

permeability describes the conductivity of a porous medium with respect to fluid

flow, whereas porosity is a measure of the fluid storage capacity of a porous material.

Permeability describes how easily a fluid is able to move through the porous material.

Thus, it is related to the connectedness of the void spaces and to the pore size of the

paper.

Permeability

Current equations describing fluid transport in porous media are based on

semi-empirical equations derived in the 19th century by Darcy [40] for single- phase

flow and in the 20th century for multi-phase flow. These equations describe the

average behavior of a mixture of a porous medium and one or more fluids. Most

simple fluids obey Newton’s law of viscosity i.e. their flow behavior can be

characterized by a constant viscosity r\. The relationship between the pressure drop

AP and the flow rate Q for isothermal, steady state, creeping flow of a Newtonian

fluid through a porous medium (permeability k) was established empirically by H.

Darcy in 1856 [40]. Its most simple form, for unidirectional and horizontal flow, is:

tA - T)- £AL

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. where:

Q = flow rate, (m /s) K = permeability coefficient, (m2) AP = pressure drop or difference, (Pa) AL = flow length or thickness of test sample, (m) A = area of cross-sectional area to flow, (m2) = fluid viscosity, (Pa-s)

As the understanding of porous media flow is important in different fields

such as chemical, petroleum and paper engineering, the prediction of the permeability

of a porous medium is an important property. Many theoretical and experimental

studies have used packed beds of particles like spheres or fibers as models for porous

media [41-43] to determine the permeability. Experiments on these media have

resulted in semi-empirical relations, which provide a reasonable estimation of the

permeability of packed beds [40].

Diffusion

Diffusion at isothermal conditions is driven by a difference in vapor pressure,

and can be described by Fick’s Law [34,44,45]. Diffusion is the net transport of

matter in a system by means of random molecular motion, which acts to remove

chemical potential differences and will eventually produce an equilibrium state of

concentration (Coo). The motion of a molecule dissolved in a polymer can be thought

of as a series of random walks between absorption sites [46]. Fick’s first law of

diffusion, expresses the steady state flux of diffusant per unit area (J) through a

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 20 membrane as a function of the concentration gradient, where c is the concentration of

diffusing molecules.

(H.2) KClX;

The proportionality constant D is known as the diffusion coefficient. The

diffusion coefficient may depend on the concentration of diffusant. However, for

some systems, e.g. gases above their critical temperature (fixed gases), the diffusion

coefficient often does not depend on concentration, in which case Fick’s second law

can be used to determine the time dependence (unsteady state) of the concentration, c,

of the diffusant in the sample [34,45].

(D.3)

Diffusion following the Fick’s first and second laws is termed Fickian

diffusion [44]. The diffusion coefficient is temperature dependent and for ideal

systems follows an Arrhenius relationship, with an energy barrier to diffusion Ed -

(D.4)

For example, diffusion rates can increase significantly when the temperature is

increased above the glass transition temperature Tg. Diffusion of water through

polymers can follow Fickian or non-Fickian kinetics [47,48]. Fickian transport often

occurs in rubbery polymers that possess sufficient chain mobility to allow water

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. penetration [49]. A curve of the mass uptake, M, versus t1/2 is linear. A case is usually

referred to as non-Fickian when anomalous plots are obtained.

Capillary Transport

Capillary transport [50], driven by gradients in suction stress, is another

possible mechanism for transporting liquid moisture, although capillarity transport

can only redistribute moisture, not remove it, from the media. The microstructure of a

coated layer, including the size distribution of its micropores, is one of the most

important factors influencing the physical properties of paperboard [51], including its

barrier characteristics. Therefore, it is necessary to understand the porous structure of

coated paperboard. The penetration of the liquid phase of the coating color into paper

is believed to be more important for coating color transfer than the bulk flow into the

paperboard structure [52]. All models assume that the void structure is a bundle of

cylindrical capillaries. Liquid penetration takes place through capillary flow into the

capillaries. The Lucas-Washbum equation [50, 53] can to some degree be used to

analyze liquid penetration into paper and paperboard.

Capillary transport controls liquid uptake through surface chemical properties

[50, 53]. The driving potential for the liquid movement is the sum of the external

pressure and the capillary pressure. The surface energy and pore size control the

capillary pressure driving force where the surface roughness determines the initial

water uptake [52]. The relationship between capillarity and geometrical properties of

the substrate can be demonstrated by the Young and Laplace equation [54,55]:

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 22 2 .r .c o s 0 A P = — ------(DL5) r

For porous media, the process of liquid penetration into the pore can be described by

Lucas and Washburn equation [50,53]:

dL _ y»r»cos 0 (H.6) dt 4 . L . //

After integrating in the range from Lo= 0 to Li= 1 and from to= 0 to to = t, the

resulting equation is

1 y-r.t* cos# L = — •------(n.7) 2 r \

Thus, the Lucas-Washbum equation, based on the liquid transport model can be

written as:

|2.y.r.cos0 + P.r L=\--- ;------.{ (H.8) 4 . 7 7

where:

AP pressure difference (capillary pressure), (Pa)

7 = surface tension of liquid, (N/m) e contact angle, between liquid and solid phase, (deg.) r = pore radius, (pm) L length or depth of capillary penetration, (pm) P external pressure, (Pa) T1 fluid viscosity, (Pa-s) t = penetration time, (sec)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The surface chemical properties of the coating layer are critical to achieving a

high barrier against water and water vapor. As the size of coating materials such as

shape engineered pigments is reduced, particularly in the nanometer range, the effects

of surface characteristics become even more pronounced. The extremely thin shape

engineered pigment platelets provide a highly active surface area, which leads to

improved barrier properties.

Surface Energy

The surface of any material is different from the bulk material [55]. On atomic

scale, the difference between the surface and the bulk properties is due to fact that the

surface atoms have a smaller number of neighboring atoms. The surface (free) energy

across an interface is a measure of the work required to form a unit area of new

surface. Surface energy can be determined by the contact angle measurement method

[55]. In addition to the surface energy, the polar and non-polar characteristics of the

surface can be determined. The term surface tension is used for liquids, and surface

energy for describing solids. Surface energy and surface tension have the same

numerical and dimensional values.

The spreading of a liquid over a solid surface is governed by the surface

energies of the solid-vapor interface, the liquid-vapor interface, and the solid-liquid

interface. The liquid transfer is influenced strongly by whether the liquid phase wets

the solid phase (substrate) or not. At the liquid-solid surface interface, if the cohesive

forces between molecules of the liquid are greater than the adhesive forces between

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. molecules of the liquid and solid surface, the liquid beads-up and does not wet the

surface. On the other hand, if the adhesive forces between the molecules of the liquid

and solid surface are greater than the cohesive forces between the molecules of liquid,

the liquid will wet the solid surface. When two surfaces make contact, the force acting

at their interface is called the interfacial tension. The work of adhesion between a

solid and liquid phase, is illustrated by the following equation [54]:

WSL= Ysv + Ylv - Ysl (H.9)

So for a liquid to spread over the surface, the surface energy of the solid-vapor

interface must be greater than the combined surface energies of the liquid-vapor and

the solid-liquid interfaces. The spreading coefficient has the significance of predicting

the liquid-substrate interaction. The spreading coefficient of a liquid on a solid

surface, is illustrated by the equation:

Sus = Ysv - Ylv - Ysl (11.10)

If the spreading coefficient has a positive value or is zero, spreading will occur

spontaneously; no spreading occurs if the value is negative [54-56]. Wettability

depends on four properties (a) the surface energy of substrate, (b) the surface tension

of the liquid, (c) their interfacial tension, and (d) the equilibrium contact angle

between the liquid and substrate, which is directly dependent on the other three

factors (Figure 2.4). This relationship between surface tension and contact angle is

given by the Young and Dupre equation [57].

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 25

— ysL Ysv = Ysl + TLv cos 0 or cos 0 = ~ (II. 11)

The critical surface tension is defined as the value of Ylv (surface tension of a liquid

in equilibrium with the saturated vapor), where the cosine of 6 is one. By combining

work of adhesion and spreading coefficient:

Sl/s = W sl-W ll (II. 12)

where:

Ysv = surface energy of a solid in equilibrium with the saturated vapor YLv = surface tension of a liquid in equilibrium with the saturated vapor

Ysl = interfacial tension between the solid and the liquid Sus = Spreading coefficient of a liquid on a solid surface

W s l = Work of solid-liquid adhesion

Wsl = Work of liquid-liquid cohesion

It’s not only the surface tension but also the nature (polar vs. non-polar) of the

liquid that influence wetting. The contact angle measures the physical angle derived

from a drop of liquid placed on a perfectly smooth solid surface. A low contact angle

results from a high degree of solid-liquid interaction and a high contact angle is an

indication of a low degree of interaction [57]. Contact angles of 0° to 90° are taken to

represent degrees of wetting, whereas from 90° to 180° represent non-wetting. The

barrier properties of the paper and paperboard against water and water vapor can be

improved by designing a barrier coating that will impart low surface energy.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 2.4. Components of Interfacial Tension and Contact Angle

Nano-Composite/Structured Coatings

Nanocomposites [58-60] are a new class of materials that are particle filled

polymers for which at least one dimension of the dispersed particles is in the

nanometer range. We can distinguish three types of nanocomposites, depending upon

how many dimensions of the dispersed particles are in the nanometer range. The first

type is isodimensional nanoparticles, such as spherical silica nanoparticles which are

in the order of the nanometers in all the dimensions [59]. The second type, whiskers

or nanotubes such as cellulose whiskers [61] or carbon nanotubes [62], have two

dimensions in the nanometer range and the third is larger forming an elongated

structure. The third type, sheet like fillers or pigments such as shape engineered

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. pigments [33], has only one dimension in thickness in nanometer range as shown

SEM microphotograph in Figure 2.5. Mostly, these types of nanostructured materials

are used in this study. The nanostructured coatings were obtained through

incorporation of engineered pigments to a polymer.

Low Shape Factor Clay High Shape Factor Clay

Figure 2.5. Shape Engineered Pigments SEM Microphotographs

The fluid transport properties of polymeric materials can be significantly

altered by incorporating shape engineered pigment particles. The effects of the

particle shape factor, particle size and distribution and volume fraction on the

effective permeability of the coated board have been studied. Akkapeddi et al. [63]

suggested that the increased tortuosity provided by the nanoclay particles essentially

slows transmission of oxygen through the composite and drives molecules to the

active scavenging species resulting in near zero oxygen transmission. Similarly, nano

modified polymers have been shown to enhance mechanical properties such as

strength and stiffness.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. When polymers encounter water, the most prevalent substance on earth, their

properties and functions are affected. The kinetics and rate of water diffusion depends

on the polymer’s physical structure and surface properties as well as on environmental

elements such as humidity and temperature. Therefore, understanding the diffusion

process is critical to developing reliable polymer products. Thus, an ability to

minimize the extent to which water molecules are absorbed can be a major advantage

for durability of packaging. Several researchers reported that nanoclay incorporation

can significantly reduce the extent of water absorption in polymeric packaging due to

increased tortuosity [64,65].

In addition, the nanoclay shape factor significantly affects the water diffusion

characteristics through the nanocomposites [64-68]. Specifically, increasing the shape

factor was found to diminish substantially the amount of water absorbed, thus

indicating the beneficial effects likely from nanoparticle incorporation in comparison

to conventional microparticle loading. Hydrophobic enhancement would clearly

promote both improved nanocomposite properties and diminish the extent to which

water would be transmitted through to an underlying substrate. Thus, applications in

which contact with water or moist environments is likely, could clearly benefit from

materials incorporating nanoclay particles. Clay platelets provide high tortuosity;

hence the mean free path of the water vapor or gas molecules (or atom) is

significantly greater than the pore diameter (Figure2.6). Increased tortuosity slows

transmission of water, water vapor and gasses [33,64-68].

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 29 Effective Flow Length (Le) Actual Flow Length (L)

Figure 2.6. Barrier Properties-Tortuous Path for a Particle to Migrate Through a Layer of Clay Platelets

Conventional and Barrier Coatings

Conventional paper coatings are designed above the critical pigment volume

concentration (CPVC) to achieve higher light scattering [69-72]. The CPVC is

defined as the point in a pigment-binder system at which just enough binder is present

to completely fill the void left between the pigment particles. Over 90% (by weight)

of a conventional coating formulation can be of pigments. This results in increased

light scattering due to the voids between the pigment particles. The permeability of

the coating film to water, water vapor and gasses increases greatly in the presence of

voids. The strength of the coating film also decreases at high pigment volume

concentration [69]. The barrier coatings are designed below the CPVC to attain low

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. permeability and high strength coated films. In pigment-binder system, below the

CPVC, the binder controls the coating structure. The coating voids and stiffness is

influenced by the type and the amount of the binder [73]. The coating structure can be

studied using scanning electron microscopy (SEM) [74,75], white light

interferometery (WYKO) and atomic force microscopy (AFM) [76,77]. WYKO

White Light Interferometry [74,75], a non contact and non destructive technique was

used to study the dry coating 3D topography.

The pigment type, particle shape and aspect ratio, particle size and

distribution, surface area, [33,78-87], and various colloidal forces [54,55],

interactions with other components in the coating formulations affect the particle

packing and that in-tum affects the coating film permeability to liquids and gasses.

The pigment particles packing also affect the wet coating properties such as viscosity,

water retention, rheology and runnability [69]. The study of the dry coating structure

is essential to understand the spatial arrangement of pigment particles and binder; the

factors that affect it; and its relationship to barrier performance.

Paper and board coating pigments are either platy, like kaolin [33, 68, 88, 89]

or talc [25,90], or close to spherical like ground calcium carbonate [91,92] (GCC),

silica [71,72], polystyrene, and some grades of precipitated calcium carbonate (PCC)

[93]. Most clay minerals are part of a large family of silicate minerals called

phyllosilicates [63,68], These layered structures are built up from two dimensional

sheets of tetrahedrally coordinated silica linked to parallel sheets of octahedrally

coordinated aluminum or magnesium oxide, In (1:1) phyllosilicates, such as kaolin

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 31 (china clay), each tetrahedral layer is linked to one octahedral layer. In (2:1)

phyllosilicates such as montmorillonites (bentonites) and laponite each octahedral

layer is sandwiched between two tetrahedral layers as shown in Figure 2.7. The choice

of clay, polymer and preparation method determine the final material form whether

it’s a micro or nanocomposite with full intercalation or exfoliation.

The aspect ratio or shape factor (the ratio of platelet diameter to thickness, see

Figure 2.8) varies with the source of crude clay, particle size, and whether or not it

has been mechanically delaminated during processing. Thus, a higher aspect ratio

means a platier particle. The determination of aspect ratio is tedious and time

consuming. It is determined using Transmission Electron Microscopy (TEM), a

shadowing technique [88,94,95]. Example of TEM image is shown in Figure 2.9. For

a given shadow angle, particle thickness (T) is proportional to shadow length or

diameter (D). Since all commercial clays have a broad distribution of sizes, a large

number of particles must be measured.

Measurement of equivalent spherical diameter (e.s.d) does not differentiate

between delamination and transverse fracture as opposed to shape factor [94,95]. The

shape factor, which is mass-based, can be a valuable tool for comparison purposes,

with regard to the rheological properties of the coating color and the final barrier,

mechanical and optical properties of the coating layer.

0.5 2.356 Shape Factor (SF) = — and - S'^ [94] (H.13) T D SF

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 32

Tetrahedral Structure

Figure 2.7. Clay Mineral Structure

Figure 2.8. Calculating Disc Diameter from ESD and Shape Factor Measurements

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Particle Shadow

Figure 2.9. Example of TEM Shadowing Techniques to Measure Shape Factor

The Packing of Particles

The packing of spheres of uniform size can be theoretically arranged in five

different ways [78,80]; (1) cubical, (2) single-staggered (cubical tetrahedral), (3)

double-staggered, (4) pyramidal (face-centered cubic), and (5) tetrahedral (hexagonal

close-packed) arrangements having the theoretical solidity of 52.36, 60.45, 69.80,

74.05 and 74.05% respectively (see Figure 2.10 & 2.11). The latter two systems are

the closest possible packing with the same number and size of voids, but the inherent

structure is different and this has an impact on permeability [80]. Monodisperse cubes

may give a solidity of 100% and rods and discs of fixed size with high aspect ratio

may pack to a solidity of 90.7% [81].

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 34

Layer A

Figure 2.10. (a) Face Centered Cubic (fee) & (b) Hexagonal Close Packing (hep)

Figure 2.11. (a) & (b) Tetrahedral Site and (c) & (d) Octahedral Site

In addition to uniform packing, there is a frequently occurring random

arrangement lying between two well defined limits which are called loose and dense

random packing. The maximum packing value for loose and dense randomly packed

equally sized spheres was found to be approximately 58.9% and 63.9% respectively,

[78] in the absence of any particle-particle interactions, air-film effect, and external

forces except gravitational force and mechanical shaking.

An increase in solidity could be achieved only if spheres of different sizes are

used. In this case smaller spheres must fit into the voids between the already packed

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. larger spheres. The particle shape and size distribution greatly affects the packing

volume [81]. The packing of suspended particles depends on the interaction potential

energies between particles as well as on the stability of suspensions [78]. The

suspension viscosity depends on the packing volume fraction as well as on the

volume fraction and decrease with increasing packing volume fraction.

Computer simulation techniques have been predominantly used to study

particle packing. The different size distributions such as normal, log-normal, Rosin-

Rambler have been studied [82-85]. Most attempts at computer simulation assume a

spherical shape, although some simulations of non-spherical particles have been

reported [86,87]. The two-dimensional packing of spheroids with various types of

size distributions and standard deviations, but of fixed aspect ratio has also been

studied [87]. The spheroids packing fraction was found to be higher than spheres for

all types of size distribution studied.

The Structure of Paper Coatings

Paper coatings are applied as an aqueous suspension of a pigment and binder

in soluble or particulate form. The aqueous phase is then dried using hot-air and IR-

dryers and structure is formed. The first (gloss) critical concentration is reached when

the pigment particles are brought into contact with one another, and a matrix is

formed [69,73]. The fluid phase is however still mobile, and the structure may shrink

until the second (opacity) critical concentration is reached, after which the binder has

sometimes formed a film and then no longer exists as separate particles [73].

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The porous nature of the coating has a very strong influence on its optical,

mechanical and fluid absorption properties [51,52,69,71-73,91] and is related to the

packing ability of the particles [78-87]. The development of coating structures

depends on the colloidal interactions in the coating formulation, pigment shape and

size distribution, binder properties, the substrate absorbency, the application method,

and the drying conditions [71-73,92,96,97]. Vidal, et al., [98,99] showed that coating

structure development can be predicted using a computer model based on a Monte

Carlo deposition method. It is very important to optimize the coating structure for

barrier and other performances [100-101]. The pore structure of a coating layer can be

evaluated by different methods, such as image analysis (89) and mercury intrusion

porosimetry (MIP) [102,103]

Climpson and Taylor [89] produced images of porous networks using

specially-prepared cross-sections which were then submitted to computerized image

analysis by considering the voids as oriented oblate spheroids. MIP [102,103], based

on the principle that the applied intrusion pressure is inversely proportional to an

equivalent diameter of the voids. However, the major drawback of this method is that

the measured pressure is related to the narrowest part of the pore (the “neck” or the

“throat”). The Pore-Cor model [102] is considered to be an improvement on

traditional mercury porosimetry. Pore-Cor is fitted to the experimental data obtained

by MIP, and the computation is basedon the assumption that the realvoid structure

can be replaced by a bundle of capillaries (throats) and cubes (voids) of different sizes

[102,104].

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 37 MacroPac Simulation Software

MacroPac simulation software from OxMat Intelligensys Ltd. [105,106] was

used to study the particle packing for monodisperse and polydisperse particle systems.

The choice of particle size, shape and size distribution can significantly affect the

packing density of a system, as can the size and boundaries of the container holding

the particles. MacroPac offers the options of using different packing algorithms such

as random placement, static, gravity, or shake packing. During packing each object is

selected according to defined shape and size distribution criteria, and then is placed in

the simulation container. MacroPac checks for the overlap with neighboring particles.

If an overlap is detected, an attempt is made to place the particle in a new position. It

simulates real particle packing, taking account of the following:

• different particle shapes: plate, rods, spheres and cubes- or all of them together

• different size distributions: uniform, normal and log normal

• different boundary conditions to simulate real physical situation

MacroPac randomly places particles in a box. It can then shuffle them about, or move

them in a specific direction to simulate the effect of gravity. While the simulation is

running, volume fractions are reported. In addition, particle orientation can be

calculated. MacroPac also allows the user to choose the packing box size, boundary

walls, in 2 and 3 D (Figure 2.12). The following boundary options are available for

use:

• hard boundaries - for modeling the effect of a wall

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 38 • soft boundaries- for modeling the system interface with air

• periodic boundaries - for modeling infinite bulk systems with a single

simulation box

Figure 2.12. Particle Packing Using MacroPac (3D Visual)

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82. Abreu, C.R.A., Tavares, F.W., and Castier, M., “Influence of Particle Shape on the Packing and on Segregation of spherocylinders via Monte Carlo Simulations”, Powder Technol., 134 (2003), 167-180.

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86. Sherwood, J.D., “Packing of Spheroids in 3-Dimensional Space by Random Sequential Addition”, J. Phy.A., 30 (1997), L839-L843.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 45 87. Hwang, K.J., Wu, Y.S., and Lu, W.M., “Effect of the Size Distribution of Spheroidal Particles on the Surface Structure of a Filter Cake ”, 1997 Powder Technology 91, 105.

88. Morris, P.P., Sennett, P., and Drexel, R.J., “Delaminated Clays - Physical Properties and Paper Coating Properties”, 1965 TAPPI 48(12), 92A.

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92. Knappich, R., “Wet and Dry Coating Structure of Calcium Carbonate Pigments With Narrow Particle Size Distribution”, 1999 TAPPI Coating Conference, p. 373-385

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 46 100. T. C. Bissot, “Performance of High-Barrier Resins with Platelet-Type Fillers; Effect of Platelet Orientation”, in Barrier Polymers and Structures, American Chemical Society, 1990.

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104. Matthews, G. P., Ridgway, C. J., and Spearing, M. C. “Void Space Modeling o f Mercury Intrusion Hysteresis in Sandstone, Paper Coating, and Other Porous Media”, 1995, J. Colloid Interf. Sci. 171, 8.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 47 CHAPTER m

STATEMENT OF THE PROBLEM AND OBJECTIVES

Barrier coated packaging is an extremely large and important area of interest

to manufacturers, retailers, and consumers. It is expected to grow rapidly as industry

expands its offerings of ethnic and specialty foods, nutraceuticals and functional

foods, extended shelf life products, and convenience foods and products and serving

ware such as paper cups and plates. Consumers are demanding longer shelf life,

safety, and added value packaged products. To package these products, there is a need

for sustainable barrier systems. The need to reduce the amount of non-recyclable and

unsustainable barrier materials such as petroleum based products is growing.

This work was initiated in an effort to develop sustainable barrier SBS

paperboard coatings using shape engineered pigments and co-polymerization process.

Further, these coatings were optimized for barrier and mechanical performance. The

factors studied were pigment types, shape factor, particle size and distribution and

orientation of particles, binder types, hydrophobic and hydrophilic character of

binders, application methods, and calendering. A new method for the calculation of

the permeability coefficient of porous media was developed. The permeability

coefficient was used to predict the pore size and fluid absorption and spreading rate.

In virtually all cases, paperboard used to produce a commercial package

represents an image. To account for this need, the optical and surface properties of the

developed coatings were also quantified and compared.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 48 The research outlined in this dissertation is based on the following objectives:

1. To develop sustainable barrier SBS paperboard coatings using shape

engineered pigments and co-polymerization process.

2. To study the influence of shape-engineered pigments on the barrier,

mechanical, surface and optical properties of the barrier coatings.

3. To develop permeability coefficient measurement method to characterize the

barrier coatings.

4. To determine if the barrier characteristics of SBS paperboard can be improved

by incorporating shape-engineered pigments.

5. To determine the dependence of barrier properties on permeability, pore size

and coating structure.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 49 CHAPTER IV

EXPERIMENTAL DESIGN

The experimental program is divided into four phases:

Phase I: Conventional Pigment Polymer (CPP) Coatings

♦ to formulate barrier coatings using shape engineered pigments with different

binders

♦ to apply barrier coatings onto SBS baseboard using a lab padder (size press),

Mayer rod (wire wound), and blade (cylindrical laboratory coater (CLC) at

different speed)

♦ to characterize the coated sample’s barrier and mechanical properties by

measuring gas, water and water vapor permeabilities, and stiffness properties

Phase II and HI: Co-Polymerized (COP) Coatings

♦ to develop COP coatings by polymerizing acrylic co-monomers with HSFE

clays

♦ to apply COP coatings onto pre-coated, as well as on non-pre-coated baseboard

using a Mayer rod and blade (CLC) at different coat weights

♦ to characterize the COP coated sample’s barrier properties by measuring gas,

water and water vapor permeabilities, and optical and surface properties by

measuring brightness, gloss and roughness

♦ to characterize the COP coated sample’s mechanical properties by measuring

flexural modulus and stiffness

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 50 Phase IV: Permeability Coefficient

♦ to develop a method for calculation of a permeability coefficient, and

♦ to study the effect of pigment type, coating application methods, coating

pickups and coat weight on measured permeability coefficients;

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 51 Materials

Selected well characterized shape engineered pigments were obtained from

Imerys, Roswell, GA. The physical properties of the shape engineered pigments

investigated during this study are shown in Table 4.1. Two binders used in this study

were Lipacryl MB 3640 (Rohm & Hass Company) and PB6850 NA (Dow Chemical

Company). Lipacryl-MB3640 is a 100% acrylic whereas PB 6850 NA is a styrene

butadiene based binder. The solid content, pH, Brookfield viscosity, glass transition

temperature (Tg) and average particle size of the binders according to manufacturer,

are given in Table 4.2. Two commercial baseboard; pre-coated and non-pre-coated

were used as the substrate for the coatings application. The base substrates

characteristics are given in Table 4.3.

Table 4.1. The Physical Properties of Shape Engineered Pigments

Plate BET Surface Pigments Trade Name D50 (nm) SF Thickness Area (m2/g) (nm)

XP6117 150-200 10-20 40 20-22

AstraPlate 450-550 25-35 70 16-18 Clays XP8000 450-550 50-60 40 18-20

XP6200 950-1050 80-90 70 12-14

Carbonate XP8100 200-240 29-31

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 52 Table 4.2. The Characteristics of the Binders

Brookfield Avg. Glass Solids Binders pH Viscosity Particle Transition (%) (cps) Size (nm) Temp, Tg (°C)

MB-3640 54 .5-55.5 6.5-7.5 400 250-325 -5.0

PB-6850 48.5-50.0 7.0-8.0 250 150-200 9.0

Control 50.0-52.0 6.5-7.5 400 80-100 -15.0 (8604-65)

Table 4.3. The Characteristics of the Uncalendered Baseboard Substrates (Stdev. in Parenthesis)

Solid Bleached Sulfate Precoated Bleached Substrate Properties (SBS) Baseboard Baseboard

Precoating No Yes

Grammage, g/m2 270 (2.8) 284 (2.7)

PPS Porosity, ml/min 249.1 (8.5) 13.9 (0.5)

Thickness, mils 14.20 (0.45) 15.66 (0.21)

Permeability, pm2 4.33xl0'3 (1.48x1 O'4) 2.70 xlO’4 (l.lxlO '5)

Roughness, pm 5.90 (0.28) 5.71(0.09)

75° Gloss, % 22.17 (0.79) 16.22 (0.42)

Brightness, % 85.33 (0.30) 85.11 (0.11)

WVTR (g/m2day) 1149(89) 1008 (57)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 53 Coating Preparations and Application Methods

Phase I: Conventional Pigment Polymer (CPP) Coatings

CPP coatings were prepared using different shape engineered pigments and

binders for size press, rod drawdowns and blade (CLC) applications. The shape

engineered pigments of different aspect ratio and particle size were used as shown in

Table 4.1. The XP8000 and XP8100 were received at 62.8% and 64.6% solids

whereas XP6117 & XP6200 were pre-dispersed at 60% solids using a high shear

Cowles disperser. Two different binders, MB3640 and PB 6850 were used as shown

in Table 4.2. Conventional methods were used to prepare the coatings for this phase.

The solids in the coatings were measured using a Labwave solids analyzer and the

Brookfield viscosities were measured at 100 rpm using #3 spindle with an LVT

digital viscometer. Coatings were applied on to a 14 point SBS baseboard as shown in

Table 4.3.

The experimental design for the size press coatings are shown in Table 4.4.

Coatings for size press were prepared using three pigments, each at two levels with

two different binders. The slurried pigments were blended into the appropriate

amount of binders under low shear mixing to yield the desired size press

formulations. The size press coatings varied in the amount of dry pigment added on

dry weight of binders (6 & 100 %). All coatings were applied at approximately 30%

solids at room temperature. The size press speed was adjusted to get the required pick

ups. The viscosities of the coatings were all below 150 cps.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The experimental design for the rod drawdowns coatings are shown in Table

4.5. Coatings for rod drawdowns were prepared using three pigments, with two

different binders. The binders were blended into the appropriate amount of slurried

pigments under low shear mixing to yield the desired rod coating formulations. The

formulation contains 10 parts of binder per 100 parts of dry pigment by weight. All

coatings were formulated at approximately 58% solids and further diluted to get the

desired coat weights. The viscosities of the coatings were all below 600 cps.

The experimental design for the CLC coatings is shown in Table 4.6. Coatings

for blade (CLC) were prepared using four pigments with one binder (MB3640). The

formulation contains 10 parts of binder per 100 parts of dry pigment. The viscosities

of the coatings were all below 400 cps. All coatings were formulated and applied at

approximately 55% solids at room temperature at different coat weights to obtain a

coat weight curve.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 55 Table 4.4. Experimental Design for CPP Coatings for the Size Press Application Using Minitab

Factors Responses Run Run I.D. Run Run Order Barrier Optical Surface Binders %Wt of Pigments Pigments Properties Properties Properties Properties Mechanical

S 1 10 XP8000 MB3640 6

S 4 7 XP8000 MB3640 100

S 5 1 XP6117 MB3640 6

S 8 9 XP6117 MB3640 100

S 9 3 XP6200 MB3640 6

S 12 6 XP6200 MB3640 100

S 13 4 XP8000 PB6850 6

S 16 11 XP8000 PB6850 100

S 17 5 XP6117 PB6850 6

S 20 12 XP6117 PB6850 100

S 21 8 XP6200 PB6850 6

S 24 2 XP6200 PB6850 100

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 56 Table 4.5. Experimental Design for CPP Coatings for the Rod Application Using Minitab

Factors Response 1 Run Run I.D. Run Run Order Barrier Optical Binders Surface Formula Pigments Properties Properties Properties Properties Mechanical 1 1 Cl 6 XP8000 MB3640 C2 2 XP8000 PB6850 C3 3 XP6117 MB3640 C4 5 XP6117 PB6850 Parts Parts Binder C5 4 XP6200 MB3640

C6 1 XP6200 PB6850 Parts 100 Pigment +10

Table 4.6. Experimental Design for CPP Coatings for the Blade Application Using Minitab

Factors Responses Run Run I.D. Run Run Order Barrier Surface Formula Pigments Properties Properties CLC CLC Speed t-i 1 11 XP6117 3000

3 12 XP6117 500 to 4 5 Astra Plate 3000 § O h 5 7 Astra Plate 1500 o 6 1 Astra Plate 500 + c 7 4 XP8000 3000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Phase II: Co-Polvmerized (COP) Coatings

COP coatings were prepared using different shape engineered pigments and

control binder at different pigment loadings for rod drawdowns and blade (CLC)

applications. The shape engineered pigments of different aspect ratio and particle size

were used as shown in Table 4.1. An acrylic control binder was used for emulsion co

polymerization as shown in Table 4.2. The solids in the coatings were measured using

a Labwave solids analyzer and the Brookfield viscosities were measured at 100 rpm

using #3 spindle with an LVT digital viscometer at room temperature. The particle

size and distribution was measured using a Microtrac UPA 150 Particle Size Analyzer

as shown in the Appendix.

The experimental design for the rod drawdowns coatings are shown in Table

4.7. The COP coatings for rod drawdowns were prepared using three pigments

(XP6117, XP8000, & ContourXtreme) and a control binder (8604-65) as shown in

Table 4.1 and 4.2. The characteristics of the COP coatings are shown in Table 4.8.

Coatings were applied on to a 14 point SBS baseboard as shown in Table 4.3.

The experimental design for the CLC coatings is shown in Table 4.9. Coatings

to be blade (CLC) coated were prepared using three pigments (XP6117, Astra Plate,

& XP8000) in a control binder (8604-65) as shown in Table 4.1 and 4.2. All COP

coatings were loaded with 30% pigments on dry weight of binder. The characteristics

of the COP coatings are shown in Table 4.10. The Hercules high shear viscosity was

also measured at 4800 RPM using an E-bob, ramp time of 20 second. The coatings

water retention values were measured using AAGR as per TAPPI standard (T-701).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 58 Coatings were applied on two commercial baseboards; pre-coated and non pre-coated

at different coat weights. The operating conditions of CLC coater are shown in Table

4.11.

Table 4.7. Experimental Design for COP Coatings for the Rod Application Using Minitab

Factors Responses Run Run I.D. (%) Run Run Order Barrier Surface Loading Pigments Properties Properties

8618-2 4 XP8000 5 8618-3 1 XP8000 30 8604-63 7 XP8000 55 8618-4 6 XP6117 5 8604-64 9 XP6117 30 8604-62 8 XP6117 55 8604-57 3 ContourXtreme 5 8604-56 2 ContourXtreme 30 8604-58 5 ContourXtreme 55 8604-65 10 None 0

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 59 Table 4.8. The Characteristics of the COP Coatings for Rod Application

Pigment Sample ID Pigments Solids (%) Loading (%)

8618-2 XP8000 5 48.4 8618-3 XP8000 30 46.9 8604-63 XP8000 55 50.0 8618-4 XP6117 5 48.1 8604-64 XP6117 30 47.2 8604-62 XP6117 55 49.1 8604-57 ContourXtreme 5 49.1 8604-56 ContourXtreme 30 47.0 8604-58 ContourXtreme 55 47.1 8604-65 None 0 47.0

Table 4.9. Experimental Design for COP Coatings for the Blade Application Using Minitab Barrier Optical Surface Coatings Properties Properties Properties Properties Sample Sample ID Run Order Baseboard Mechanical

1 5 XP8000 Pre 2 1 XP8000 Non 3 7 XP6117 Pre 4 6 XP6117 Non 5 4 Control Pre 6 3 Control Non 7 8 Astra Plate Pre 8 2 Astra Plate Non

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 60 Table 4.10. The Characteristics of the COP Coatings for Blade Application

Pigment WRV Viscosity (cps) Coatings Solids (%) Loading (%) (g/m2) Brookfield HHSV Control 0 51.0 174.4 365 41.3 XP8000 30 44.1 71.6 216 12.9 Astra 30 45.7 79.1 116 15.1

XP6117 30 44.8 92.6 412 20.1

Table 4.11. Operating Conditions of CLC Coater

Coating Backing Spacer Speed, Blade (CB) Blade (BB) Ext. (SX) Drying ft/min Inch Inch Inch Min. Dryer Delay 1500 0.015 0.018 0.50 10 sec-15 % pre-drying 40 sec-100% post-drying

Calendering and Conditioning of Samples

CPP coated samples were calendered at 1600 PLI, 2-nip smooth side. Co

polymerized coated samples were calendered at 600 and 1600 PLI, 2-nip smooth side.

All the coated paperboard samples were conditioned for 24 h at 50% RH and 23°C

(73.4 °F) before any measurements were made.

Testing and Instruments

The uncalendered and calendered samples were then tested for barrier, surface,

optical and mechanical properties. The dry coating surface and structure were also

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 61 studied using scanning electron microscopy (SEM), burnout, and WYKO white light

interferometer. The tests performed are shown in Table 4.12.

Table 4.12. Description of Different Tests Used for Coating Characterization

Properties Tests Descriptions WVTR Water vapor transmission rate Barrier PPS Porosity Gas permeability Permeability Gas permeability Coefficient PPS Roughness Air leakage roughness test SEM Scanning electron microphotograph Bum out Coating coverage Surface White light interferometer, non contact, 3 D WYKO topography, roughness parameters Atomic force microscopy, 3 D topography, AFM roughness Brightness Reflectance of light at 457 nm wavelength Optical Hunter Gloss Specular reflection of light 2-Point Stiffness Taber stiffness and elastic modulus Mechanical Instron tester, flexural load, stiffness, 3-Point Stiffness modulus

The water vapor transmission rate (WVTR), PPS porosity, permeability

coefficient, caliper, PPS roughness, gloss, brightness, 2 and 3 point stiffness and

surface characteristics were determined. The WVTR of each test sample was

determined by the gravimetric dry-cup method with the coated side towards the humid

air. Measurements were carried out at 75% RH and 73°F as well as at 81% RH and

100°F, each of which is the average of three and four tests respectively. Water vapor

molecules that permeated the samples were measured and WVTR were calculated.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The PPS porosity was measured using a Parker Print Surf (PPS) tester (T 555)

at 1000 kPa. Thicknesses of the coated samples were measured using a Micrometer (T

411). The permeability coefficient, K was calculated from the PPS porosity (air

permeability) and caliper data using the following relationship:

K (pm2) = 0.048838*Q (ml/min)* L (m) (IV. 1)

The brightness, 75° gloss, and roughness were measured as per TAPPI

standards. The brightness of the samples was measured using a Technidyne

Brightness meter, TAPP procedure T 452. Gloss was measured using a Hunter 75°

gloss meter according to TAPPI procedure T480. The surface roughness of the

samples were measured using a Parker Print Surf (PP) tester (T 555).

Images using scanning electron microscopy (SEM) were obtained for visual

comparison. Bum out images was also obtained for visual comparison, using

ImageXpert software. The coated paperboard samples were immersed in a bumout

test solution (2.5% ammonium chloride, 50% isopropyl alcohol aqueous solution) for

2 minutes, allowed to air dry, then heated for 20 minutes in a blow dryer at 200 °C.

The bumout samples were than evaluated for variations in the amount of coating

coverage using an ImageXpert. WYKO White Light Interferometry, a non contact and

non destructive technique was used to study the dry coating 3D topography. The

roughness values, Ra (arithmetical mean deviation), Rq (root mean square) and Rt

(sum of height of the largest profile peak height and the largest profile valley depth

within the evaluation length) were also reported. The mechanical properties were

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. measured using Taber stiffness (2 point bending) and Instron (3-point bending) tester

at different relative humidity and temperature conditions.

The influence of pigments’ shape factor, platelet thickness, and particle size

and distribution; binder types and chemistry; coating preparation and application

methods; shear rate and finishing operations on barrier, surface, optical and

mechanical properties were studied.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 64 Appendix

Particle Size Analysis of Co-Polymerized (COP) Coatings

Loading Pigment %Z- Dia. 1 Dia. 2 I.D. Pigments %, %, 2 (%) Location 6300 (pm) 1 (pm)

8604-65 None 0.087 100 - -

8618-4 XP6117 5 PE 2% 0.064 89 0.41 11

8604-64 XP6117 30 PE 2% 0.106 87 1.42 13

8604-62 XP6117 55 Mixed 2% 1.16 78 0.39 22

8618-2 XP8000 5 PE 1% 0.062 98 - -

8618-3 XP8000 30 PE 1% 0.097 59 1.32 41

8604-63 XP8000 55 Mixed 1% -- 1.53 100

8604-80 AstraPlate 5 PE 1% 0.067 100 --

8604-78 AstraPlate 30 PE 1% 0.112 77 2.22 23

8604-77 AstraPlate 55 Mixed 1% -- 1.89 100

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 65 CHAPTER V

SHAPE ENGINEERED PIGMENTS BASED BARRIER COATINGS FOR SBS PAPERBOARD

Lokendra Pal, Margaret K. Joyce, Paul D. Fleming, and David E. Knox* Department of Paper Engineering, Chemical Engineering and Imaging, Western Michigan University, Kalamazoo, MI, USA *MeadWestvaco Corp. Charleston, SC, USA Proceedings of the WMU Barrier Coating Symposium, October, 9-10, 2006

Abstract

Paper and paperboard are complex materials and are mainly composed of

wood fibers, fillers and various additives. Extrusion coating with unsustainable

petroleum based products, such as polyethylene, polypropylene and polyethylene

terephthalate, etc., is a widely used method to improve barriers against water, water

vapor, and gases. Pressure on consumers to use environmentally friendly packaging

materials has created a large and expanded need for renewable, recyclable and/or

biodegradable materials. Paper manufacturers therefore, desire to produce paperboard

for barrier applications on-machine in a single run, and consumer pressure to reduce

the amount of non-recyclable materials has created a need for new research in

dispersion coatings.

This study concentrates on the formulation, application, characterization and

optimization of shape engineered pigmented coatings for barrier applications. In

contrast to off-line extrusion coating with unsustainable petroleum based products,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. high shape factor engineered clay dispersion coatings were used to provide packaging

board with water, water vapor and gas barrier and other property enhancements.

The pigment shape factor, SF, appears to have a systematic effect on barrier

properties although it’s relatively small in some cases. The shape factor significantly

impacted the saturation coat weight (where complete coverage occurs). The medium

shape factor pigment (SF ~ 50-60) provided the highest barrier properties for the SBS

board tested, but the results might be different for boards of different roughness and

porosity. The 100 % acrylic based hydrophobic binder gave better barrier properties

compared to styrene butadiene based binder. The double-coated treatment method

(size press/rod) produced the best results. The effect of application method on barrier

properties was found to have a more significant impact on the barrier properties than

the shape factor of the pigment. There was only a slight impact of pigment shape

factor and application method on stiffness.

Introduction

The need to reduce the amount of non-recyclable materials is receiving much

attention [1,2]. Solid bleached sulfate (SBS) paperboards manufactured from

cellulosic wood fibers fulfill many of the requirements of primary recycling since

cellulose is biodegradable. SBS is a premium paperboard grade that is produced from

fully bleached virgin Kraft pulp (sulfate process) fiber. The major markets for SBS

are folding cartons such as milk and juice cartons and recyclable foodservice products

such as paper cups, plates, and food containers [3,4].

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Packaging made from SBS paperboards has therefore been extensively used to

contain perishable products. Unfortunately, due to the high gas permeability and

hydrophilicity of cellulosic fibers, perishable and liquid products cannot be contained

in simple paperboard containers. To overcome these difficulties, paperboard packages

are commonly extrusion coated off-line with unsustainable petroleum based products

[5-9] such as polyethylene, polypropylene and polyethylene terephthalate, etc. to

improve barriers against water, water vapor, and gasses [10-15]. Above all, the

recycling of petroleum based products coated on SBS paperboard is extremely

difficult. In addition, the mechanical properties of baseboard are affected during the

extrusion process as temperature can reach in excess of 300°C [16], above the glass

transition temperature (Tg) [17] of cellulose, hemicellulose and lignin.

Thus, the paper manufacturer’s desire to produce paperboard for barrier

applications on machine in a single run, and consumer pressure to reduce the amount

of non-recyclable petroleum based products has created a need for research in

dispersion coatings. Due to the above concerns and desires, dispersion coatings with

inorganic and organic materials are gaining a widespread interest to improve barriers

against permeation of water, water vapor and gases [5,18-22].

The barrier properties achieved depend on shape factor, particle size, particle

size and distribution and orientation of pigments, hydrophobic and hydrophilic

character of binders, application methods, drying conditions and any finishing

operations such as calendering [23-35]. The mechanical properties depend on pigment

and binder types, coating thickness, and calendering operations [36,37]. Shape

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 68 engineered pigments [38] can contribute exceptional barrier performances to

paperboard, due to the increased tortuosity of the diffusion path [38-42] as shown in

Figure 5.1.

One area that encompasses many of these requirements is SBS paperboard

composite packaging, particularly with respect to the water, water vapor and air

permeabilities. This grade is the subject of the current study.

Effective Flow Length (Le) Actual Flow Length (L)

Figure 5.1. Tortuous Path for Water Molecules to Migrate Through a Layer of Clay Platelets

The Structure of Clay Minerals

Most clay minerals are part of a large family of silicate minerals called

phyllosilicates [41-43]. These layered structures are built up from two dimensional

sheets of tetrahedrally coordinated silica linked to parallel sheets of octahedrally

coordinated aluminum or magnesium oxide. In (1:1) phyllosilicates, such as kaolin

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 69 (china clay), each tetrahedral layer is linked to one octahedral layer. In (2:1)

phyllosilicates such as montmorillonites (bentonites) and laponite each octahedral

layer is sandwiched between two tetrahedral layers (Figure 5.2) [43-45].

Tetrahedral Structure

Figure 5.2. Clay Mineral Structure

Clay platelets provide high tortuosity; hence the mean free path of the water

vapor or gas molecules (or atom) is significantly greater than the pore diameter

(Figure 5.1). Increased tortuosity slows transmission of water, water vapor and gasses

[38-42], The choice of clay, polymer and preparation method determine the final

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. material form whether it’s a micro or nanocomposite with full intercalation or

exfoliation.

Effect of Relative Humidity and Temperature on Paperboard Properties

Most of the properties and functions of the paperboard are significantly

influenced by the relative humidity (RH) and temperature conditions [4,12,17]. The

amorphous regions in the fiber are considered to be sites of moisture sorption rather

than crystalline cellulose [4,17,46]. Water in liquid or vapor form is absorbed into the

paperboard; water molecules fill the voids that are formed between cellulosic polymer

chains and then induce relaxation, or swelling. Because of the small size of water

molecules, their ease of condensation and ability to hydrogen bond, water affects

paperboard products in ways that are unique in comparison to any other substance.

Adsorbed water and water vapor affect the thermo-mechanical properties of

wood polymers as shown in Figure 5.3 [17]. Water reduces the glass transition

temperature (Tg), the modulus, and the strength due to the plasticization effect,

especially at high temperature [4,17]. The fibers swell or expand anisotropically in the

transverse (perpendicular) direction to the cellulosic fiber axis, which tends to

increase the fibril angle (angle between the fibril direction in the S2 layer and the

longitudinal axis of the wood fiber, which typically ranges between 15° and 30°). This

in-tum affects the mechanical properties such as elastic modulus and the stiffness of

wood fibers [47,48].

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 71

250

/■— s U Disordered CeMose O 200

HemkeMoses Lienin a 150 H § 100

t-H

0 10 20 30 40 50 60 Moisture Content (%)

Figure 5.3. Effect of Moisture Content on Glass Transition Temperature (Tg) of Cellulose, Hemicellulose and Lignin [17]

Experimental Design

This work is divided into four phases: (1) to formulate barrier coatings using

shape engineered pigments with different binders, (2) to apply barrier coatings onto

SBS baseboard using a lab padder (size press) and Mayer rod (wire wound), (3) to

characterize the coated sample’s barrier and mechanical properties by measuring gas,

water and water vapor permeabilities, and stiffness properties, and (4) to optimize the

barrier coatings.

Materials

The shape engineered pigments investigated during this study are shown in

Table 5.1. Three different, finely dispersed shape engineered pigments were used.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 72 Two binders, an acrylic and SBR based were used during the first phase of screening.

The solid content, pH, Brookfield viscosity and average particle size of the binders,

according to manufacturer, are given in Table 5.2. Commercial Solid Bleached

Sulfate (SBS) baseboard was used as the substrate for barrier coatings applications.

The base substrate characteristics are given in Table 5.3.

Table 5.1. The Characteristics of the Mineral Pigments

Avg. Particle BET Surface Mineral Pigment Aspect Ratio Size, nm Area, m2/g XP6117 10-20 150-200 20-22 XP8000 50-60 450-550 18-20 XP6200 80-90 950-1050 12-14

Table 5.2. The Characteristics of the Binders

Brookfield Avg. Particle Binder Type Solids, % pH Viscosity., cps Size, nm MB3640 Acrylic 54.5-55.5 6.5-7.5 400 250-325 PB6850 SBR 48.5-50.0 7.0-8.0 250 150-200

Table 5.3. The Characteristics of the Base Substrates (Stdev. in Parenthesis)

Solid Bleached Sulfate (SBS) Cup Stock, 270 g/m2 Substrate Properties Uncalendered (0 PLI) Calendered (1600 PLI) Thickness, mils 14.20 (0.45) 12.2 (0.39) PPS Porosity, ml/min 249.1 (8.5) 84.4 (5.0) Permeability, pm 4.3 3x10'3 (1.48x1 O'4) 1.28x10'3 (0.76x1 O'4) Roughness, pm 5.90 (0.28) 4.32 (0.19) Brightness, % 85.33 (0.30) 84.96 (0.21) WVTR (g/m2day) 1149 (89) 1115(81)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Coating Formulations and Application Methods

Coatings for size press and rod drawdowns were prepared using three shape

engineered clays, each at two levels with two different binders. The three shape

engineered clays of different aspect ratio and particle size were used as shown in

Table 5.1. XP8000 was received at 62.8% solids whereas XP6117 and XP6200 were

pre-dispersed at 60% solids using a high shear Cowles disperser. Two different

binders, acrylic and SBR based were used as shown in Table 5.2. Sample IDs

corresponding to a particular formulation are shown in Table 5.4.

The pigments were then blended into the appropriate amount of binder to yield the

desired sizing solution. The size press coatings varied in the amount of dry pigment

added on dry weight of binder (6 & 100 %). The coating solids and viscosity were

measured. All coatings were applied at approximately 30% solids. The viscosities of

the coatings were all below 150 cps. Coatings were applied on SBS baseboard using a

lab padder (size press).

The rod coating formulation contained 10 parts of binder per 100 parts of dry

pigments by weight. The coating solids and viscosity were measured. All coatings

were formulated at approximately 58% solids and further diluted to get the desired

coat weights. The viscosities of the coatings were all below 600 cps. Coatings were

applied on SBS baseboard using various Mayer rods.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Calendering and Conditioning of Samples

The coated samples were calendered at 1600 PLI, 2-nip smooth side. All the

coated paperboard samples were conditioned for 24 hrs at 50% RH and 23°C before

any measurements were made.

Testing

The samples were then tested for water vapor transmission rate (WVTR), PPS

porosity, caliper and stiffness. WVTR of each test sample was determined by the

gravimetric cup method according to TAPPI standards with the coated side towards

the humid air. Measurements were carried out at 75% RH and 73°F as well as at 81%

RH and 100°F. Water vapor molecules that permeated the samples were measured

and WVTR values were calculated.

The porosity was measured using a Parker Print Surf (PPS) tester at 1000 kPa.

Thickness of the coated samples was measured using a Micrometer. The permeability

coefficient, K was calculated from the PPS porosity (air permeability) and caliper data

using the following relationship (49):

K (pm2) = 0.048838*Q (ml/min)* L (m) (V. 1)

Stiffness was tested using a Taber stiffness tester at 50 and 75% RH and 73°F

temperature conditions at 15 degree. Images were also obtained for visual

comparison, using scanning electron microscopy (SEM) of selected samples.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 75 Table 5.4. Sample IDs for Different Formulations and Applications

Formulations Sample ID Pigments Binders Pigment Loading SI XP8000 MB3640 6% S4 XP8000 MB3640 100% S5 XP6117 MB3640 6% C/3 t/5 S8 XP6117 MB3640 100% 8 £ S9 XP6200 MB3640 6% C2S8 XP6117 MB3640 > + O C3S12 XP6200 MB3640 C/3 C4S16 XP8000 PB6850 £ Q it N C5S20 XP6117 PB6850 GO C/3 C6S24 XP6200 PB6850

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 76 Results and Discussion

Coatings

Table 5.5 and Figures 5.4 and 5.5 show the effect of pigment shape factors on

PPS porosity and permeability for selected size press and rod coated samples. The

result shows that shape factor has an effect on the air permeability of the paperboard

samples. The medium shape factor pigments gave the best results.

Table 5.5 and Figure 5.6 shows the WVTR results for selected size press and

rod coated samples at 81% RH & 100°F. Differences in transmission rates between

untreated samples and the shape-engineered pigments are seen. This indicates that

platy pigments can serve as an efficient barrier coating, owing to their increased

tortuosity, and particle orientation. Samples treated with XP8000 were significantly

different from those treated with XP6117 and XP6200.

Table 5.5 and Figures 5.7 and 5.8 show the elastic modulus results for selected

size press and rod coated samples at 50 and 75% RH and room temperature. There is

no distinguishable difference of elastic modulus among different shape-engineered

clay coatings. The results shows slight decrease in elastic modulus as humidity

increases. This indicates that platy pigments can serve in retaining the mechanical

strength of baseboard under high relative humidity and temperature.

Pigments

Figure 5.9 compares the barrier properties of three different shape engineered

clays at a coat weight of -32 gsm. XP8000 with a SF of 50-60 and a 40 nm plate

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 77 thickness gave the best results. The medium shape factor with thinner platelets

provided the lower permeability. The theoretical calculation for the permeability (K)

can be done using the following formula:

rrt 2 K = a ------(V.2) (1 + 0.5 -SF)

Where T is the platelet thickness, SF is the shape factor, a is a dimensionless

proportionality coefficient and the denominator term is the tortuosity factor. The

permeability, therefore varies with the square of the plate thickness and approximately

inversely with the shape factor. The experimental results are consistent with this

formula when we recall that the formula applies to the coating only, while what we

have measured the permeability of the composite (coating plus baseboard).

Application Methods

Figures 5.4, 5.5 and 5.10 compare the porosity and permeability coefficient for

the different coating methods. The size press plus rod coated samples were the least

permeable, followed by the rod coated samples. Figure 5.6 compares the WVTR of

size press plus rod coated samples, at 81% RH, 100°F. The WVTR was lowest for the

double coated samples. Figures 5.7 and 5.8 compare the effect of application method

on elastic modulus at 50 and 75% relative humidities. There was only a slight impact

of pigment shape factor and application method on stiffness. Figures 5.11 and 5.12 in

the Appendix show images of selected pigments and coatings on baseboard, obtained

using SEM. Visual comparison clearly indicates that XP8000 gave a more uniform

coating and supports air permeability and WVTR results.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 78 Table 5.5. Comparison of Barrier and Mechanical Properties of Selected Samples for Different Coating Methods

PPS Permeability Elastic Modulus WVTR Porosity Coefficient (GPa), (from (g/m2*d) Sample (ml/min) (pm2) Taber Stiffness) ID 81%RH 50%RH 75%RH 50% RH & 73°F &100°F & 73°F &73°F SI 20.6 3.1xl0'4 840 6.0 5.6 S4 29.0 4.4x1 O'4 884 6.3 5.8 S5 28.6 4.2x1 O'4 913 5.9 5.7 Cfl C3 17.75 3.0x10'4 984 5.0 4.9 o T3 C4 6.99 1.2x10'4 1020 5.4 5.3 C5 12.02 2.1xl0'4 1079 5.0 4.8 I G C6 6.23 l.lxlO ’4 995 5.0 4.9 73o C1S4 2.32 3.9x1 O'5 754 4.0 4.0 Pi + C2S8 4.94 8.3xl0‘5 923 5.0 4.9

CO C3S12 3.44 5.9xl0"5 788 5.3 5.3 CO C4S16 3.14 5.1xl0'5 769 5.0 4.9 £Mh u C5S20 6.66 l.lxlO'4 986 6.3 6.0 N iJ3 C6S24 3.34 5.6x10'5 790 5.6 5.6

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 79

48.0

40.0

32.0 — e — 5 24.0 o oI* P- 16.0 8 o S S 12 S S W3 4 S CN CL CN vo 00 Tf CL CO w-l (N C/3 c/3 O CO 8.0 CO CO - - ^ U 0.0 aft IE Q i l l XP8000 XP6117 XP6200 XP8000 XP6117 XP6200 (SF 50-60) (SF 10-20) (SF 80-90) (SF 50-60) (SF 10-20) (SF 80-90) Pigments

Figure 5.4. Influence of Pigments Shape Factor on PPS Porosity of Selected Coated Samples

8.E-4 7.E-4 6.E-4 6 a. 5.E-4 4.E-4 •8 3.E-4 CNo 00

Figure 5.5. Influence of Pigments Shape Factor on Permeability of Selected Coated Samples

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 80

1200 1100 1000 [fi 900 * i 800 ■o X 700 "nn •n 600 <59 u g 500 400 300 200 100 0 f XP8000 XP6117 XP6200 XP8000 XP6117 XP6200 (SF 50-60) (SF 10-20) (SF 80-90) (SF 50-60) (SF 10-20) (SF 80-90) Pigments

Figure 5. 6. Influence of Pigments Shape Factor on WVTR at 81%RH & 100°F of Selected Coated Samples

7.0 6.0 -I * * * 5.0 * 4.0

3.0 U W 2.0

1.0

0.0 T* "'!■ f XP8000 XP6117 XP6200 XP8000 XP6117 XP6200 (SF 50-60) (SF 10-20) (SF 80-90) (SF 50-60) (SF 10-20) (SF 80-90) Pigments

Figure 5. 7. Influence of Pigments Shape Factor on Elastic Modulus at 75%RH & 73°F of Selected Samples

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 81

6.0

5.0 F F * 4.0 — aCL.

3.0 m* o i> o in£ o o in in r- in r^- 2.0 in in cn m 5 U in 3

1.0 -

0.0 XP8000 XP6117 XP6200 XP8000 XP6117 XP6200 (SF 50-60) (SF 10-20) (SF 80-90) (SF 50-60) (SF 10-20) (SF 80-90) Pigments

Figure 5. 8. Comparison of Elastic Modulus at 50 and 75%RH and 73°F of Selected Rod Coated Samples

20.0

15.0 -

10.0 o

0.0 -I 0.0 XP8000 XP6117 XP6200 XP8000 XP6117 XP6200 (SF 50-60) (SF 10-20) (SF 80-90) (SF 50-60) (SF 10-20) (SF 80-90) Pigments Pigments

Figure 5. 9. Influence of Shape Factor (SF) and Plate Thickness (T) (CoatWt. -3 2 gsm) on Barrier Properties for Pigments Only (No Binder)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 82

■ S4 OS8 ♦ S12 ♦ S16 ♦ S20 OS24 XC1 □ C2 ♦ C3

+ C4 ♦ C5 OC6 XC1S4 -C2S8 OC3S12 AC4S16 OC5S20 -C6S24 8.0 SP+Rod * Kod ^ ^ Size Press ■ ' w in' 7.0 ▼ V ■<<—i x 6.0 ♦ t4 a 5.0 .32 o ■ O £ 4.0 (U o U 3.0 2.0 ▲ J3C3 Oi 1.0 - % & ** Cu 0.0 11 1...... 1 1 ...... 1 ■ 1 0.0 6.0 12.0 18.0 24.0 30.0 36.0 42.0 48.C PPS Porosity (ml/min)

Figure 5.10. Influence of Application Method (Size Press vs. Rod Coating and Double Coat) on Barrier Properties

Conclusions

The pigment shape facto appears to have a systematic effect on barrier

properties although it is relatively small in some cases. The shape factor significantly

impacted the saturation coat weight (where complete coverage occurs). The medium

shape factor pigment (SF -50-60) provided the highest barrier properties for the 14 pt

SBS board tested, but the results might be different for boards of different roughness

and porosity. The 100 % acrylic based hydrophobic binder gave better barrier

properties compared to styrene butadiene based binder.

The double-coated treatment method (size press/rod) produced the best results.

The effect of application method on barrier properties was found to have a more

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. significant impact on the barrier properties than the SF of the pigment. As expected,

Taber stiffness decreases with increase in relative humidity. However, there was only

a slight impact of pigment shape factor and application method on stiffness.

References

1. Charles P. Klass, “Emerging Barrier Coating Market Trends”, Barrier Coating Symposium, Western Michigan University Kalamazoo, MI, Oct. 8-9, 2002, Kalamazoo, MI.

2. Charles P. Klass, “Market Trends”, Barrier Coating Symposium, Oct. 12-13, 2004, Kalamazoo, MI.

3. Shanton, Kenneth J., “Plate Stock”, US Patent 5776619, July 1998

4. J. Kline, “ Paper and Paperboard”, 2nd Ed., Miller Freeman Publishing, San Francisco, 1991.

5. Jurkka Kuusipalo, “Characterization and Converting of Dispersion and Extrusion CoatedHD-Papers”, TAPPI, 2003 PFFC

6. Davey, C.R., and Kurzbuch, W., “LLDPE for Extrusion Coating”, TAPPI 1998 P,L&C Conference Proceedings”, August 1988

7. Potts, M.W., and Pope, T. J., “Extrusion Coatings vs. Lamination: How Affinity* Polyolefin Plastomers Will Offer More”, TAPPI 1997 P,L&C Conference Proceedings, August 1997

8. Schwarz, P., Mahlke, M., “Polyamide Nanocomposites for Extrusion Coating Applications”, From the conference proceedings of 2003 TAPPI Eur. PLACE Conf. 2, pp. 1451-1480(2003).

9. Krook, M., Gallstedt, M., Hedenqvist, M.S., “A Study on Montmorillonite/ Polyethylene Nanocomposite Extrusion-Coated Paperboard ’, Packaging Technol. Sci. 18(1), pp. 11-20(2005).

10. Lucas R., “Uber das Zeitgesetz des Kapillaren Aufstiegs von Flussigkeiten”, Kolloid-Z., 23:15(1918).

11. Washburn E. W.: “The Dynamics o f Capillary Flow”, Phys. Rev., 17: 273 (1921).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 84 12. Dullien, F. et al., “ Porous Media, Fluid Transport and Pore Structure”, Academic Press Inc., Second Edition, San Diego, 1992.

13. Gane et al., “Fluid Transport into Porous Coating Structures: Some Novel Findings”, Tappi J. 83 (5): 77 - 78 (2000)

14. M. Joyce and T. Joyce, “Practicalities of Using Impregnation (Controlled Penetration Sizing Method) for Improving the Barrier and Strength Properties of Linerboard”, Invited Speaker, Internal and Surface Sizing PIRA Conference, Graz, Austria, 2003.

15. M. Joyce and T. Joyce, “ Nanoparticle Barrier-Coated Substrate and Method for Making the Same”, US Patent 6,942,897 Sept. 13, 2005.

16. Halle, R. W., and Simpson, D. M., “A New Enhanced Polyethylene for Extrusion Coating and Laminating”, TAPPI 2003 PFFC

17. Peel, D. P., Paper Science and Paper Manufacture, 1999 Vancouver: Angus Wilde Publication.

18. Schuman, T. et al., “Characteristics of Pigment-filled Polymer Coatings on Paperboard”, Progress in Organic Coatings 54 (2005) 360-371

19. Vaha-Nissi, M., Lahti, J., Savolainen, A., Rissa, K., and Lepisto, T., “New water- based barrier coatings for paper and paperboard”, Appita Journal, 54(2): 106(2001).

20. Vaha-Nissi, M., Savolainen, A., Talja, M., and Moro, R., “Dispersion Barrier Coating of High Density Base Papers”, 1998 TAPPI Coating Conference Proceedings.

21. Rissa, K., Vaha-Nissi, M., Lepisto, T., and Savolainen, A., “ Talc-filled water- based barrier coatings”, Paper and Timber, 84(7):467(2002).

22. Kan, C. S., Kim, L. H., Lee, D. I., and van Gilder, R. L., “Viscoelastic Properties of Paper Coatings: Structure/Property Relationship to End Use Performance”, TAPPI Coating Conference Proceedings, pp. 49-60.

23. T. C. Bissot, “Performance of High-Barrier Resins with Platelet-Type Fillers; Effect of Platelet Orientation”, in Barrier Polymers and Structures, American Chemical Society, 1990.

24. Risio, S. D., and Yan, N., “ Effect of Pigment Properties on Coating Structure as Measured by AFM”, 2005 TAPPI Coating and Graphic Arts Conference, Toronto, Canada

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 85 25. Hostetler et al., “Drying for Optimum Binding Strength in SBS Paperboard”, 2005 TAPPI Coating & Graphic Arts Conference, Toronto, Canada

26. Kawamukai, T., Ishii, E., Yagi, H., “Moisture Permeation Mechanism of Latex Films Filled with Platelike Fillers”, 2001 TAPPI JOURNAL, Vol. 84(3), March 2001.

27. Bernard et al., “ Polyamide Nanocomposites with Oxygen Scavenging Capability”, US Patent 6777479, Aug 2004

28. Adur et al., “ Clay-Filled Polymer Barrier Materials for Food Packaging Applications”, US Patent 6358576, March 2002

29. Turner et al., “ High Barrier Amorphous Polyamide-Clay Nanocomposite and a Process For Preparing Same”, United States Patent 6417262, July 2002

30. Gilmer et al., “Polymer/Clay Nanocomposite Having Improved Gas Barrier Comprising a Clay Material With a Mixture of Two or More Organic Cations and a Process for Preparing Same”, United States Patent 6486253, November 2002

31. Cavagna, Giancarlo A.; Claytor, Robinson C., “ Barrier Coating to Reduce Migration of Contaminants From Paperboard, United States Patent 5153061, October 1992.

32. Ruf, W.; Bachler, J., “ Method for Reducing the Water Vapor Permeability of Paper”, US Patent 5358790, Oct 1994

33. http://www.nanocor.com/nanoclays.asp

34. Nilsson, L., Wilhelmsson, B., and Strenstrom, S., “ Drying Technology”, 11(6): 1205 (1993)

35. Z. R. Zang, R. W. Wygant, A. V. Lyons and F. A. Adamsky, “How Coating Structure Relates to Performance in Coated SBS Board: A Fundamental Approach”, 1999 Coating Conference, TAPPI Proceedings.

36. Kim-Habermehl et al., “Coated Paper Stiffness: A Practical Perspective”, 2000 International Printing & Graphic Arts Conference Proceedings

37. Okomori, K. and Enomae, T., “Evaluation and Control of Coated Paper Stiffness”, 1999 Coating Fundamentals Symposium Proceedings

38. Iyer, R., “ Advances in Pigment Technology”, 2005 TAPPI Coating and Graphic Arts Conference, Toronto, Canada

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 86 39. Brody, A. L., “ Nano, Nano" Food Packaging Technology”, Food Technol. 57(12), pp. 52-54(2003).

40. Ragauskas, A. J., “Big Opportunities with Tiny Technology”, Pulp and Paper, 78(5), p. 80(2004).

41. Lopez, G. A., “ Introduction to Layered Silicate Nanocomposites”, From the 2000 conf. proc. of TAPPI-Polym. Lamin. & Coatings Conf. 3, pp. 1063-1067(2000).

42. Akkapeddi, Murali K. et al., “Oxygen Scavenging High Barrier Polyamide Compositions for Packaging Applications ” 2004, US Patent 6,740,698.

43. Deer, W. A., Howie, R. J., Zussman J: "Rock Forming Minerals" Volume 3 "Sheet Silicates": Longmans (London) 1962.

44. Barrer R. M., "Zeolites and Clay Minerals": Academic Press (London) 1978.

45. http://www.soils.umn.edu/academics/classes/soil2125/doc/s 12chap 1 .htm

46. Perry R. H., Green D. W., “ Perry’s Chemical Engineers’ Handbook”, Seventh Edition, 1997, p. 5:42-55

47. Bendtsen, B.A. and Senft, J. , “Mechanical and Anatomical Properties in Individual Growth Rings of Plantation-grown Eastern Cottonwood and Loblolly Pine“, 1986 Wood and Fiber Science, 18(l):23-38

48. Megraw, R. A., “Wood Quality Factors in Loblolly Pine: The Influence of Tree Age, Position in the Tree, and Cultural Practice on Wood Specific Gravity, Fiber Length and Fibril Angle”, 1986 TAPPI Press, pp 1-88.

49. Lokendra Pal, Margaret K. Joyce, and Paul D. Fleming HI, “A Simple Method for Calculation of the Permeability Coefficient of Porous Media”, TAPPI Journal, Vol. 5: No. 9, Sept. 2000.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 87 Appendix

Microphotograph Using Scanning Electron Microscopy (SEM)

Figure A. Images using scanning electron microscopy (SEM) of SBS Baseboard samples

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 88

a ('V. □ ' / f

A v r .

C5 (XP6117 + MB3640)

XP8000 C4 (XP8000+MB3640)

XP6200 C6 (XP6200+MB3640")

Figure B. Images using scanning electron microscopy (SEM) of selected samples (a) pigments only (b) coatings

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER VI

HIGH BARRIER SUSTAINABLE CO-POLYMERIZED COATINGS

Lokendra Pal, Margaret K. Joyce, Paul D. Fleming, Stephanie A. Crettd* and Charles Ruffner* Center for Coating Development Department of Paper Engineering, Chemical Engineering and Imaging, Western Michigan University, Kalamazoo, MI, USA *MeadWestvaco Corp. Charleston, SC, USA

Abstract

The goal of this project was to determine the most promising co-polymerized

(COP) coating for paperboard for protection against gas and water vapor

transmission. The driving force for this was to create a coating that will significantly

slow the permeation of water and water vapor through the paperboard, while retaining

its mechanical properties. This was accomplished by creating high barrier co

polymerized coatings. This study focuses on the use of modified High Shape Factor

Engineered (HSFE) clays.

The HSFE clays have been modified by the addition of silane through a wet

treatment process. In this study, acrylic co-monomers have been polymerized with

addition of three different, finely dispersed HSFE clays, to create co-polymerized

coatings. The wet coating structure was studied using Brookfield and Hercules Hi-

Shear viscometers, water retention and dispersion stability. The dry coating structure

was studied using WYKO White Light Interferometry and bum out tests. The CLC

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. coated samples were then tested for gas and water vapor permeability. Additionally,

the optical and surface properties were determined.

The CLC coated board samples showed almost zero gas permeability and a

significant reduction in water vapor transmission rate (water vapor permeability). The

water vapor permeability was reduced up to 90 % reflecting a one order of magnitude

decrease in comparison to a commercially coated sample. The XP8000 co-

polymerized coating displayed the lowest water vapor permeability and the best

optical and surface properties, thereby making it the most promising barrier coating

for SBS paperboard.

Introduction

Barrier composite coatings that provide water, water vapor and gas resistance

through the paperboard package have been widely used in food packaging [1-4].

Barrier coated packaging is now more focused towards extending shelf life,

minimizing microbial attack and ensuring food safety through control of the

environment within the package. The packaging system is composed of substrates,

coatings, barrier fluids, inks and varnishes. In addition, there are the contents of the

package system that may be solid, liquid or gaseous, or mixtures of these components.

SBS baseboard is a complex material and is mainly composed of wood fibers

(cellulose and hemicellulose), fillers (clays, carbonates, etc.), and various additives

(sizing agents, retention aids, etc.) [5]. SBS properties depend on the fiber types and

extent of fiber-fiber bonding, as well as, on the network structure. The cellulosic

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. fibers are a key constituent of any board-based packaging and provide desired

structural rigidity to the package. Unfortunately, due to the high water, water vapor

and gas permeability of cellulosic fibers, paperboards are commonly extrusion coated

off-line with unsustainable petroleum based polymer barriers such as waxes, ethylene-

covinyl alcohols and plastics (polyethylene, polypropylene and polyethylene

terephthalate, etc.) [5-11]. Above all, the recycling and repulpability of these

polymers and plastics coated paperboard are extremely difficult.

Packaging products made from cellulosic materials are increasingly being

modified and improved not only for barrier resistance but also for appearance and

printability. The following strategies can be used to improve barrier performance (1)

improve the quality of the barrier coating layer by reducing the defects and/or (2)

adopt a multilayer coating structure and decouple the defects. These strategies were

used by developing a nanostructured co-polymerized coating using HSFE (High

Shape Factor Engineered) clays that reduce permeation via a tortuous path [12] as

shown in Figure 6.1.

Nanocomposites [13, 14] are a new class of materials that are particle filled

polymers for which at least one dimension of the dispersed particles is in the

nanometer range. We can distinguish three types of nanocomposites, depending upon

how many dimensions of the dispersed particles are in the nanometer range. The first

type is isodimensional nanoparticles, such as spherical silica nanoparticles which are

in the order of the nanometers in all the dimensions [13]. The second type, whiskers

or nanotubes such as cellulose whiskers [15] or carbon nanotubes [16], have two

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 92 dimensions in the nanometer range and the third is larger forming an elongated

structure. The third type, sheet like fillers or pigments such as HSFE clays [14], has

only one dimension in thickness in nanometer range as shown in the SEM

microphotograph in Figure 6.2. This type of nanostructured materials is used in this

study. The nanostructured coatings were obtained through intercalation of the polymer

co- polymerization as shown in Figure 6.3.

♦ ///// mu

r fa) r i

Figure 6.1. (a) Microcomposites: pigments particles size: length (pm) width (pm) thickness (pm) (b) Nanacomposites: pigments particles size: length (pm) width (pm) thickness (nm)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 93

XP6117 XP8000

Figure 6.2. HSFE Clay Platelets Scanning Electron Microphotographs

Random Dispersion Uniform Dispersion

Phase Separated

(Microcomosite) m u m u 11 11 mu lllll urn mil mil ^ mt iiiii iiiii

i 2 1 ii " i i 11 i i i n i m i in i i i i i i i i i ...... Intercalated i l l l l (Nanocomposite) 3 4

Exfoliation (Nanocomposite) — — — —

5 6 Figure 6.3. Comparison of Conventional Pigment Polymer (CPP) Coatings: Phase Separated Microcomposites and Co-Polymerized (COP) Coatings: Intercalated and Exfoliated Nanocomposites

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. There are great challenges in manufacturing the co-polymerized coatings in

terms of full intercalation and colloidal stability of clay particles in the water phase. A

highly hydrophobic surface is required for complete intercalation, whereas a highly

hydrophilic surface is required for colloidal stability of the coatings. The properties of

composite materials are also greatly influenced by the degree of mechanical mixing

between the polymer and filled particles. In conventional polymer clay composites,

the clay platelets are immiscible with the polymer matrix resulting in

microcomposites with chemically distinct phases.

In today’s age of point of purchase (POP) retailing to attract consumers, a

package’s appearance is used to sell the product [17]. Thus, it is important that the

final packaged product looks good. In virtually all cases, paperboard used to produce

a commercial package represents an image. To account for this need, the optical and

surface properties of co-polymerized coatings were also quantified and compared.

In this study, first HSFE clays were modified by the addition of silane through

a wet treatment process. Next, acrylic co-monomers were polymerized in the presence

of three different, finely dispersed HSFE clays; XP6117, Astra Plate and XP8000, to

prepare the co-polymerized coatings. The chemical and mechanical mixing process of

the HSFE clays, especially the particle size and stability of the COP coatings, were

studied, and the relationship between these coatings and the barrier properties against

gas and water vapor of the coated layer was investigated. For the purpose of

comparison, commercially available pre-coated and non pre-coated baseboards were

used.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Experimental Design

This work is divided into three phases: (1) to develop COP coatings by

polymerizing acrylic co-monomers with HSFE clays, (2) to apply COP coatings onto

pre-coated, as well as on non-pre-coated baseboard using a cylindrical laboratory

coater (CLC), and (3) to characterize the COP coated sample’s barrier properties by

measuring gas, water and water vapor permeabilities, optical and surface properties.

Materials

Acrylic co-monomers were used for emulsion polymerization. The molecular

weight, Brookfield viscosity, average particle size, solid content and pH of the control

emulsion, are given in Table 6.1. The control emulsion has no HSFE clays present.

The characteristics of HSFE clays according to manufacturer (Imerys, Roswell, GA)

are given in Table 6.2. Three different, finely dispersed HSFE clays, XP6117, Astra

Plate and XP8000 were used to develop the co-polymerized coatings. Two

commercial baseboard; pre-coated and non-pre-coated were used as the substrate for

the COP coatings. The base substrate characteristics are given in Table 6.3.

Table 6.1. The Characteristics of the Control Binder

Solids Molecular Wt., Viscosity, Avg. Particle Binder pH (%) g/mol cps Size, nm

Control 50-52 200000-500000 6.5 - 7.5 400 80-100 (8604-65)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 96 Table 6.2. The Characteristics of the Mineral Pigments

Mineral D 50 Aspect Plate Thickness BET Surface Pigment (nm) Ratio (nm) Area, m2/g XP8000 450-550 50-60 40 18-20

Astra Plate 450-550 25-35 70 16-18

XP6117 150-200 10-20 40 20-22

Table 6.3. The Characteristics of the Base Substrates (Stdev. in Parenthesis)

Substrate Solid Bleached Sulfate Precoated Bleached Properties (SBS) Baseboard Baseboard

Pre-coating No Yes

Grammage, g/m2 270 (2.8) 284 (2.7)

PPS Porosity, ml/min 249.1 (8.5) 13.9 (0.5)

Thickness, mils 14.20 (0.45) 15.66 (0.21)

Permeability, pm2 4.33xl0'3 (1.48xl0"4) 2.70 xlO"4 (l.lxlO'5)

Roughness, pm 5.90 (0.28) 5.71(0.09)

75° Gloss, % 22.17(0.79) 16.22 (0.42)

Brightness, % 85.33 (0.30) 85.11 (0.11)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Coating Formulations and Application Methods

Co-polymerized coatings with three HSFE clays were obtained. All COP

coatings were loaded with 30% HSFE clays on diy weight of binder (see Table 6.4.).

The solids in the coatings were measured using a Labwave solids analyzer and the

Brookfield viscosities were measured at 100 rpm using # 3 spindle with an LVT

digital viscometer at room temperature. The Hercules high shear viscosity was also

measured at 4800 RPM using an E-bob, ramp time of 20 second. Table 6.4 shows the

viscosities and solids content of the COP coatings. The coatings water retention

values were measured using AAGWR as per TAPPI standard (T-701) as shown in

Table 6.4. The COP coatings were applied with a blade using a cylindrical laboratory

coater (CLC) at different coat weights. The operating conditions of CLC coater are

given in Table 6.5.

Table 6.4. The Characteristics of the COP Coatings

Pigment Viscosity, cps Coatings Solids, % WRV, g/m2 Loading, % Brookfield HHSV Control 0 51.0 174.4 365 41.3 XP8000 30 44.1 71.6 216 12.9

AstraPlate 30 45.7 79.1 116 15.1

XP6117 30 44.8 92.6 412 20.1

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 98 Table 6.5. Operating Conditions of CLC Coater

Coating Backing Spacer Speed, Blade (CB) Blade (BB) Ext. (SX) Drying ft/min Inch inch Inch

Min. Dryer Delay 1500 0.015 0.018 0.50 10 sec-15 % pre-drying 40 sec-100% post-drying

Calendering and Conditioning of Samples

The COP coated samples were calendered at two calendering pressures (600

and 1600 PLI, 2-nip smooth side). All the coated paperboard samples were

conditioned for 24 h at 50% RH and 23°C (73.4 °F) before any measurements were

made.

Testing

The samples were then tested for water vapor transmission rate (WVTR), PPS

porosity, Caliper, Roughness, Gloss and Brightness. The WVTR (water vapor

permeability) of each test sample was determined by the gravimetric cup method with

the coated side towards the humid air. Measurements were carried out at 75% RH and

73°F as well as at 81% RH and 100°F, each of which is the average of three and four

tests respectively. Water vapor molecules that permeated the samples were measured

and WVTR were calculated.

The PPS porosity was measured using a Parker Print Surf (PPS) tester at 1000

kPa. Thicknesses of the coated samples were measured using a Micrometer. The

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. permeability coefficient, K was calculated from the PPS porosity (air permeability)

and caliper data using the following relationship [18]:

K (pm2)=0.048838*Q (ml/min)* L (m) (VI. 1)

The roughness, 75° gloss, and brightness were also measured as per TAPPI

standards. Bum out images [21] were also obtained for image analysis with

ImageXpert software. The coated paperboard samples were immersed in a bumout

test solution (2.5% ammonium chloride, 50% isopropyl alcohol aqueous solution) for

2 minutes, allowed to air dry, then heated for 20 minutes in a blow dryer at 200 °C.

The bumout samples were then evaluated for variations in the amount of coating

coverage using an ImageXpert.

WYKO White Light Interferometry [19,20], a non contact and non destructive

technique was used to study the dry coating 3D topography. The roughness

parameters, Ra (arithmetical mean deviation), Rq (root mean square) and Rt (sum of

height of the largest profile peak height and the largest profile valley depth within the

evaluation length) were recorded.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 100 Table 6.6. Sample IDs for Different Formulations and Substrates

Precoated Baseboard (Pre) Non Precoated Baseboard (Non) Pigments ID Coat Wt. (g/m2) ID Coat Wt. (g/m2) 3 2.5 19 6.8 6 8.1 20 13.6 XP8000 7 13.1 21 21 5 19.3 13 5.0 25 12.6 9 9.4 23 18 XP6117 12 14.3 24 27.7 10 16.6 15 3.7 29 8.4 14 6.9 28 13 Control 18 11.7 27 23.7 17 13.3 31 4.2 36 5.7 Astra 30 7.4 38 7.9 Plate 32 8.9 34 15.2 33 16

Results and Discussion

Wet and Dry Coating Properties

A comparison of the COP wet coating properties is shown in Table 6.4. The

lowest shape factor pigment, XP6117 coating gave the highest Brookfield (low shear)

and Hercules Hi-Shear (high shear) viscosities and water retention values (WRV)

whereas the highest shape factor pigment, XP8000 coating gave the lowest Hercules

Hi-Shear viscosity and WRV. The low high shear viscosity and WRV will be the key

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. properties for coater runnability and high solids application. The coating viscosity

measurements over a week’s time show good stability with very little phase

separation. The pigment shape factor significantly influenced the wet coating

properties.

A comparison of the bumout images of COP dry coating structure is shown in

Figure 6.4. The XP8000 (SF-50-60) showed better coating coverage, even at low coat

weights, compared to the XP6117 (SF-10-20). Figure 6.5 compares the roughness

parameters (Ra, Rq & Rt), obtained from WYKO white light interferometer. The 3D

topographic images from WYKO are shown in the Appendix A. The XP8000 gave

lower roughness (Ra, Rq and Rt) values compared to Astra Plate and XP6117

indicating better particle orientation and coverage. Visual comparison and roughness

parameters clearly indicate that XP8000 pigment gave the most uniform coating.

Coatings with XP8000 pigment shows better pigment particle alignment thus high

tortuosity. These results are supported by the air permeability and WVTR results.

Barrier Properties

Figures 6.6 to 6.19 show the effect of pigment shape factor and loading,

baseboard, relative humidity and temperature and calendering on water vapor and gas

permeabilities. The results showed the pigment shape factor and loading to have an

effect on the WVTR and permeability coefficients of the paperboard samples. Tables

in the Appendix B summarize the water vapor transmission rate (WVTR) results at

81%RH & 100°F and 75% RH and 73°F respectively. It was found that the WVTR of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. the co-polymerized coatings were reduced up to five times compared to the untreated

baseboard. Tables in the appendix C summarize the PPS porosity and permeability

coefficient results. The data show an almost zero gas permeability. This indicates that

the platy pigments can serve as an efficient barrier coating, owing to their increased

tortuosity, and particle orientation.

The high shape factor with thinner platelets provided the best barrier against

water, water vapor and gasses. It is evident that coatings with thinner, platy pigments

provide increased tortuosity to the permeant path. The co-polymerized nanostructured

coating has a higher degree of dispersion and chemical interaction and surface area

than the conventional pigment polymer microcomposite coating, thus providing

higher barrier properties. The coating preparation method was an important factor in

intercalating or exfoliating these nanoclay platelets and in creating the polymer/ clay

nanocomposites.

Two different baseboards, pre and non-pre-coated were studied to compare

their surface structure effect on coating application and barrier properties. Differences

in transmission rates between pre-coated and non-pre-coated baseboard samples are

seen. The result shows that pre-coated baseboard with a smoother surface provided

higher barrier against water vapor and gas permeability, although it’s relatively low in

some cases.

The test environment i.e. relative humidity and temperature has significant

impact on barrier properties. Figures 6.6 and 6.9 compare the WVTR of pre-coated

uncalendered samples at 81%RH & 100°F and 75% RH and 73°F. It is obvious that

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. the water vapor transmission rate will increase with humidity and temperature due to

high water vapor pressure. There was a four fold decrease in WVTR from 81%RH &

100°F to 75% RH and 73°F. COP coated samples gave almost zero WVTR at

50%RH and 73°F. The calendering has significant effect on gas permeability but only

a slight decrease in WVTR. As expected gas and water permeability decreased with

calendering. The calendering failed to significantly improve the WVTR due to

densification of the coating layer causing a loss in tortuosity.

Surface and Optical Properties

Figures 6.20 and 6.21 compare the PPS roughness of pre-coated and non pre-

coated baseboard at different calendering pressure. The pre-coated baseboard coated

samples gave lower PPS roughness. The high shape factor pigment XP8000 provided

a smoother surface compared to other pigments. The PPS roughness decreases with

calendering for all coatings.

Figures 6.22 and 6.23 compare the brightness of pre-coated and non pre-

coated baseboard at different calendering pressure. The non pre-coated baseboard

coated samples gave higher brightness. There was only a slight impact of pigment

shape factor on brightness. As expected, the brightness decreases with calendering for

all coatings.

Figures 6.24 and 6.25 compare the 75° gloss of pre-coated and non pre-coated

baseboard at different calendering. The pre-coated baseboard coated samples gave

higher gloss. The high shape factor pigment XP8000 provided higher gloss compared

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 104 to other pigments due to higher smoothness and particle orientation. The gloss

increases with calendering for all coatings.

Figure 6.4. Comparison of Coating Coverage of COP Coated Samples

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 105

2.50 0.07

B =L 0.06 2.00 P i 0.05

a 1.50 £ 0.04 CA CA ca 3 3 o O 04 Pi 0.02 O O 0.50 U 0.01 >* £ £ 0.00 0.00 XP6117 Astra XP8000

Figure 6.5. Comparison of Roughness Parameters (Ra, R<, & Rt) Using WYKO White Light Interferometry

700 XP8000 Astra 600 XP6117 Expon. (XP8000) Expon. (Astra) Expon. (XP6117)

200 -

100

20 Coat Weight (g/m)

Figure 6.6. Comparison of WVTR at 81 % RH& 100°F of COP Coated Uncalendered Samples Using Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 106

700 ♦ XP8000 ■ Astra 600 A XP6117 — Expon. (XP8000) ^ Expon. (Astra) srt ; 500 T3 "“ Expon. (XP6117) 400 ■I rt 300 H > £ 200

100

0 10 15 20 25 Coat Weight (g/m)

Figure 6.7. Comparison of WVTR at 81% RH&100°F of COP Coated Calendered (600 PLI) Samples Using Pre-coated Baseboard

700 ♦ XP8000 ■ Astra 600 A XP6117 ““ Expon. (XP8000) 500 “ •Expon. (Astra) £ *o “ •Expon. (XP6117) 400 i 0£ 300 > £ 200

100

10 15 20 25 Coat Weight (g/m )

Figure 6.8. Comparison of WVTR at 81% RH&100°F of COP Coated Calendered (1600 PLI) Samples Using Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 107

250 ♦ XP8000 ■ Astra 200 A XP6117 — Expon. (XP8000) —“ Expon. (Astra) 150 - Expon. (XP6117)

100 -

Coat Weight (g/m)

Figure 6.9. Comparison of WVTR at 75% RH&73°F of COP Coated Uncalendered Samples Using Pre-coated Baseboard

250 XP8000 Astra 200 XP6117

150 -

100 -

Coat Weight (g/m2)

Figure 6.10. Comparison of WVTR at 75% RH&73°F of COP Coated Calendered (600 PLI) Samples Using Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 108

250 ♦ XP8000 ■ Astra A XP6117 200 - Expon. (XP8000) ^ — Expon. (Astra) Expon. (XP6117) 150 -

100

50 -

Coat Weight (g/m2)

Figure 6.11. Comparison of WVTR at 75% RH&73°F of COP Coated Calendered (1600 PLI) Samples Using Pre-coated Baseboard

900 ♦ XP8000 800 ■ Astra A XP6117 700 Expon. (XP8000) Expon. (Astra) 600 Expon. (XP6117) 500 400 300 200 100

Coat Weight (g/m2)

Figure 6.12. Comparison of WVTR at 81% RH&100°F of COP Coated Uncalendered Samples with Non Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 109

900 ♦ XP8000 ■ Astra 800 A XP6117 700 Expon. (XP8000) Expon. (Astra) 600 —“ Expon. (XP6117) 500 400 300 200 100

Coat Weight (g/m2)

Figure 6.13. Comparison of WVTR at 81% RH&100°F of COP Coated Calendered (600 PLI) Samples with Non Pre-coated Baseboard

900 ♦ XP8000 800 ■ Astra A XP6117 700 - “ “ Expon. (XP8000) Expon. (Astra) 600 - “ —Expon. (XP6117) 500 ao 400 300 200

100 -

Coat Weight (g/m2)

Figure 6.14. Comparison of WVTR at 81 % RH& 100°F of COP Coated Calendered (1600 PLI) Samples with Non Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 110

350 ♦ XP8000 ■ Astra 300 ▲ XP6117 Expon. (XP8000) 250 Expon. (Astra) Expon. (XP6117) 200 oo 150 -

100

50 -

Coat Weight (g/m2)

Figure 6.15. Comparison of WVTR at 75% RH&73°F of COP Coated Uncalendered Samples with Non Pre-coated Baseboard

350 -i ♦ XP8000 ■ Astra 300 ▲ XP6117 Expon. (XP8000) /—s £ 250 Expon. (Astra) T3 X Expon. (XP6117) 200 - E "ab « 150- H

% 100 -

0 5 10 15 20 25 30 Coat Weight (g/m2)

Figure 6.16. Comparison of WVTR at 75% RH & 73°F of COP Coated Calendered (600 PLI) Samples with Non Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I l l

350 ♦ XP8000 ■ Astra 300 - A XP6117 — Expon. (XP8000) 250 - — Expon. (Astra) — Expon. (XP6117) 200 60 150 -

100 -

Coat Weight (g/m)

Figure 6.17. Comparison of WVTR at 75% RH & 73°F of COP Coated Calendered (1600 PLI) Samples with Non Pre-coated Baseboard

7.0 ♦ XP8000 (Uncal) $ ■ Astra (Uncal) 6.0 - AXP6117 X "5T (Uncal) X XXP8000 X Astra (600 U + + PLI) + - + • XP6117 •8 4.0 (600 PLI) o.& + XP8000 (1600 PLI) 1600 PLI -Astra (1600 3.0 PLI) 8 12 16 20 -XP6117 (1600 PLI) Coat Weight (g/m)

Figure 6.18. Comparison of Permeability Coefficient of COP Coated Samples at Different Calendering Using Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 112

♦ XP8000 (Uncal) 66 - ■ Astra (Uncal)

AXP6117 (Uncal)

X XP8000 (600 PLI) X Astra (600 PU)

• XP6117 (600 PLI) + XP8000 (1600 18 - PLI)

& 12 - -Astra (1600 PLI)

* * -XP6117 (1600 PLI) 0 4 8 12 16 20 24 28 Coat Weight (g/m2)

Figure 6.19. Comparison of Permeability Coefficient of COP Coated Samples at Different Calendering Using Non Pre-coated Baseboard

5.0 ♦ XP8000 (Uncal)

4.0 - ■ Astra (Uncal) 0 PLI AXP6117 (Uncal) 3.0 - XXP8000 (600 PU)

X Astra (600 PLI) 2.0 - 600 & 1600 PLI • XP6117 (600 PLI)

+ XP8000( 1600 PLI)

Astra (1600 PLI) 0.0 XP6117(1600 PLI)

Coat Weight (g/m )

Figure 6.20. Comparison of PPS Roughness of COP Coated Samples at Different Calendering Using Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 113

6.0 ♦ XP8000 (Uncal) ■ ■ ► 5.0 ■ ▲ ■ Astra (Uncal) 0 PLI ^ i ♦ ▲ AXP6117 (Uncal) S 4.0

£ X1 • + x 1 + x XXP8000 (600

1 • PLI) 3.0 1 * X X Astra (600 PLI) o P4 « V i 600 & 1600 PLI • XP6117 (600 Cl. 2.0 Cl . PU) + XP8000 (1600 1.0 PLI) -Astra (1600 PLI)

0.0 --- 1 1 i 1 1 — XP6117 (1600 12 16 20 24 28 PLI) Coat Weight (g/m )

Figure 6.21. Comparison of PPS Roughness of COP Coated Samples at Different Calendering Using Non Pre-coated Baseboard

84 ♦ XP8000 (Uncal) ■ Astra (Uncal) 83 * • AXP6117 82 + * 1 A (Uncal) - I XXP8000 (600 * % PLI) | 81 * “ X Astra (600 ■§> •G X A PLI) CQ 80 • • XP6117 (600 PLI) + XP8000(1600 79 PLI) -Astra (1600 PLI) 78 -X P 6 1 17(1600 8 12 16 20 PLI) Coat Weight (g/m )

Figure 6.22. Comparison of Brightness of COP Coated Samples at Different Calendering Using Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 114

♦ XP8000 (Uncal) ■ Astra (Uncal)

AXP6117 (Uncal) XXP8000 (600

Figure 6.23. Comparison of Brightness of COP Coated Samples at Different Calendering Using Non Pre-coated Baseboard

♦ XP8000 (Uncal) 72 - ■ Astra (Uncal)

68 - AXP6117 (Uncal) g 64 - XXP8000 (600 | 60 - PLI) O X Astra (600 56 ' PU) 52 - • XP6117 (600 PLI) 48 - + XP8000 (1600 PLI) 44 - -Astra (1600 PLI) -XP6117 (1600 0 4 8 12 16 20 PLI) Coat Weight (g/m )

Figure 6.24. Comparison of 75° Gloss of COP Coated Samples at Different Calendering Using Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 115

♦ XP8000 (Uncal) ■ Astra (Uncal)

AXP6117 (Uncal) XXP8000 (600 PLI) X Astra (600 PLI) • XP6117 (600 PLI) + XP8000 (1600 PLI) -Astra (1600 PLI) 0 4 8 12 16 20 24 28 “ XP6117(1600 PLI) Coat Weight (g/m2)

Figure 6.25. Comparison of 75° Gloss of COP Coated Samples at Different Calendering Using Non Pre-coated Baseboard

Conclusions

New recyclable and sustainable co-polymerized coatings were developed for

barrier applications. Acrylic co-monomers were polymerized with addition of three

different, finely dispersed modified high shape factor engineered (HSFE) clays, to

create co-polymerized coatings. The wet and dry coating properties were studied and

showed promising results in-terms of runnability and dispersion stability. The CLC

coated samples were then tested for gas and water vapor permeability. Additionally,

the optical and surface properties were determined.

The effects of pigment shape, baseboard, coat weight, calendering and relative

humidity and temperature on barrier properties were studied through full factorial

design of experiment (DOE). From ANOVA results and main effects plot, all of the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. studied factors showed a significant impact on barrier properties. The high shape

factor and thinner platelet pigment, XP8000 (SF~ 50-60, T- 40 nm) gave the lowest

WVTR for non pre-coated baseboard. While the XP8000 and Astra (SF-25-32, T-70

nm) gave lowest WVTR for pre-coated baseboard. Calendering slightly improved the

barrier properties. Relative humidity and temperature had a detrimental effect on

barrier properties. Although the high shape factor improved coverage, the results were

comparable for the XP8000 and Astra.

The surface and optical properties showed promising results. The high shape

factor provided higher surface smoothness and gloss, with a slight impact on

brightness. Calendering has a significant impact on surface and optical properties. The

co-polymerized coatings provided very high gloss results.

References

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2. Tucker, Jr., et al., "Flexible microwave cooking pouch containing a raw frozen protein portion and method of making", March 2006, US Patent 7,015,442

3. Beaverson , et al., "Packaging material", February 2006, US Patent 7,001,661

4. Schulz, R., "In-plant tray forming", 1992 Polymers, Laminations & Coatings Conference Proceedings

5. J. Kline, "Paper and paperboard", 2nd Ed., Miller Freeman Publishing, San Francisco, 1991.

6. Lin Li, "Global environmental packaging requirements", Barrier Coating Symposium, Oct. 12-13, 2004, Kalamazoo, MI.

7. D. Twede and S. E. M. Selke, "Cartons, crates and corrugated board: handbook of paper and wood packaging technology", DEStech, Lancaster, PA, 2005.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 117 8. P. Lodha and A. N. Netravali, "Characterization of interfacial and mechanical properties of "green" composites with soy protein isolate and ramie fibers", J. Mater. Sci. 37:3657 (2002).

9. M. Gallstedt and M.S. Hedenqvist, S. Mikael, "Packaging related properties of coated whey protein and chitosan films", Barrier Coating Symposium, Western Michigan University Kalamazoo, MI, Oct. 8-9, 2002.

10. Salste, Matti et al., "Laminated package material, method for manufacturing the same, and a package", November 2005, US Patent 6,964,797

11. Frisk, et al., "Laminated packaging material for paper container", December 2005, US Patent 6,974,612

12. Akkapeddi, Murali K. et al., "Oxygen scavenging high barrier polyamide compositions for packaging applications", 2004, US Patent 6,740,698.

13. Michael Alexandre, Philippe Dubois, "Polymer layered silicate nanocomposites: preparation, properties and uses of a new class of materials", Material Science and Engineering, 28 (2000) 1-63

14. W. G. Beall and J. T. Pinnavaia, "Polymer-clay nanocomposites”, Wiley series in polymer science” Jan. 2001.

15. V. Favier, H. Chanzy, and J. Y. Cavaille, "Polymer nanocomposites reinforced by cellulose whiskers", Macromolecules, 28, 6365-6367, 1996

16. J. Foster, S. Singamaneni, R. Kattumenu, and V. N. Bliznyuk, "Dispersion and phase separation of carbon nanotubes in ultra thin polymer films", Journal of Colloid and Interface Science, 2005, 287, pp 167-172.

17. W. Soroka, "Package printing and decoration", Fundamentals of Packaging Technology; Institute of Packaging Professionals, Herndon VA, pp85-l 10,1995.

18. Lokendra Pal, Margaret K. Joyce, and Paul D. Fleming IH, "A simple method for calculation of the permeability coefficient of porous media ", TAPPI Journal, Vol. 5: No. 9, September 2006.

19. Chinga, G, Gregersen, 0 . and Dougherty, B., "Paper surface characterization by laser profilometry & image analysis", J. of Microscopy and Analysis, Sept., 2003.

20. Chinga, G., Helle, T., Forseth, T. (2002): "Quantification of structure details of LWCpaper coating layers”, Nordic Pulp & Paper Research J. 17 (3):313-318

21. Dobson, R. L., "Burnout, a coat weight determination test re-invented", TAPPI Coating Conference, April 21-23,1975, Chicago, IN, USA, p. 123-131.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 118 Appendix A

3D Topography of COP Coatings Using WYKO White Light Interferometry

#7 XP8000 Pre-coated

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. #33 Astra Plate Precoated

#12 XP6117 Precoated

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. #20 XP8000 Non Pre-coated

#34 Astra Plate Non Pre-coated

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 121

#25 XP6117 Non Pre-coated

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 122 Appendix B

WVTR Results of COP Coated Samples at Different Environmental Conditions

WVTR (g/m2x day) at 81% RH & 100°F Coating ID Uncalendered Calendered (600 PLI) Calendered (1600 PLI) Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 612.4 24.9 590.1 34.5 582.0 24.2 6 390.2 40.1 362.1 29.3 346.0 22.8 7 293.1 14.1 277.6 39.6 280.3 17.3 5 204.7 26.0 197.7 20.7 186.7 24.9 13 478.1 77.9 472.2 25.2 486.8 46.4 9 431.5 27.2 399.3 27.3 401.3 50.2 12 426.9 18.1 466.0 49.9 421.1 74.0 10 320.4 36.4 293.1 14.5 274.5 37.8 15 556.0 39.2 552.1 41.9 561.8 22.0 14 522.8 36.4 520.3 39.0 529.8 36.6 18 388.5 25.6 460.6 59.6 399.5 26.8 17 349.5 19.8 335.0 16.8 326.8 27.7 31 464.1 19.9 455.2 32.9 458.9 41.8 30 419.3 28.1 391.6 25.6 339.1 75.9 32 301.3 12.7 323.4 22.4 347.8 22.9 33 213.4 21.0 210.1 3.6 226.2 22.7 19 473.4 51.9 501.7 46.2 451.9 19.0 29 418.7 22.1 302.4 52.3 407.7 26.6 21 228.0 24.7 206.3 18.9 217.5 15.9 25 567.6 63.1 584.7 38.7 572.3 50.4 23 338.5 38.6 317.9 15.5 319.3 68.6 24 211.7 15.5 249.7 27.8 209.4 10.1 29 626.4 29.9 652.1 47.1 583.3 36.1 28 533.3 58.2 460.6 40.9 503.1 39.5 27 330.3 32.3 317.2 11.0 319.9 26.6 36 612.4 71.6 590.1 24.2 581.6 41.0 38 759.0 28.8 743.6 44.5 707.2 39.5 34 298.9 10.8 288.5 10.7 378.6 29.8 Pre 1008.5 57.6 994.9 79.3 986.9 58.9 Non 1149.2 89.0 1167.0 102.5 1115.5 81.2

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 123

WVTR (g/m2x day) at 75% RH & 73°F Coating Calendere d (1600 ID Uncalendered Calendered (600 PLI) PL D Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 204.7 6.2 198.5 3.6 176.8 2.3 6 96.9 9.4 98.5 7.5 99.3 4.8 7 81.4 8.4 78.3 10.5 72.9 4.8 5 60.5 4.7 60.5 2.3 58.9 15.5 13 152.8 5.9 152.8 1.3 139.6 8.4 9 134.9 10.1 130.3 9.3 129.5 6.7 12 155.1 31.7 129.5 15.1 124.8 12.8 10 98.5 10.5 87.6 6.7 89.2 4.8 15 214.0 16.8 197.7 10.1 184.6 11.7 14 200.1 6.2 181.5 4.7 163.6 11.5 18 138.0 5.4 145.4 21.4 128.7 7.5 17 96.9 19.8 121.0 9.3 113.2 2.7 31 149.7 8.8 154.3 1.3 95.4 21.3 30 135.7 6.7 145.8 11.7 107.8 39.6 32 131.8 30.0 96.9 4.8 113.2 10.5 33 72.1 14.2 69.0 11.0 67.5 6.2 19 261.3 51.0 193.9 40.1 172.1 37.4 29 146.6 14.2 129.5 46.5 108.6 29.9 21 84.5 8.8 72.9 4.8 72.9 15.8 25 214.8 20.3 197.7 36.3 207.8 6.7 23 79.1 6.2 108.6 10.5 114.8 3.6 24 72.9 3.6 106.2 47.6 65.1 6.2 29 231.1 5.9 223.3 4.7 200.1 6.2 28 179.9 8.8 175.2 6.7 157.4 19.5 27 111.7 4.7 111.7 11.6 98.5 7.1 36 235.0 18.2 215.6 13.6 200.1 14.2 38 299.3 15.0 256.7 11.7 239.6 23.3 34 105.5 20.3 104.7 6.2 109.3 4.7 Pre 378.4 1.3 359.8 2.7 338.1 29.5 Non 382.3 21.6 371.4 3.6 366.8 1.3

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 124 Appendix C

PPS Porosity & Permeability Results of COP Coated Samples

PPS Porosity (ml/min) Coating ID Uncalendered Calendered (600 PLI) Calendered (1600 PLI) Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 0.34 0.04 0.40 0.03 0.29 0.02 6 0.31 0.03 0.33 0.02 0.27 0.01 7 0.32 0.03 0.32 0.01 0.27 0.02 5 0.30 0.02 0.32 0.02 0.26 0.02 13 0.31 0.03 0.33 0.02 0.25 0.01 9 0.31 0.01 0.36 0.06 0.26 0.01 12 0.32 0.02 0.33 0.01 0.27 0.02 10 0.30 0.02 0.32 0.02 0.26 0.02 15 0.29 0.02 0.32 0.04 0.25 0.01 14 0.29 0.02 0.31 0.04 0.25 0.02 18 0.29 0.02 0.31 0.02 0.25 0.01 17 0.30 0.03 0.29 0.02 0.25 0.01 31 0.29 0.02 0.32 0.03 0.25 0.01 30 0.31 0.04 0.30 0.01 0.26 0.01 32 0.30 0.02 0.30 0.01 0.24 0.01 33 0.29 0.02 0.29 0.02 0.25 0.02 19 0.61 0.22 0.61 0.21 0.32 0.09 29 0.38 0.04 0.45 0.15 0.36 0.06 21 0.30 0.03 0.41 0.23 0.26 0.02 25 4.09 0.86 2.14 0.42 1.88 0.73 23 0.42 0.05 0.46 0.18 0.32 0.06 24 0.30 0.02 0.29 0.03 0.26 0.06 29 0.52 0.20 0.52 0.21 0.47 0.19 28 0.31 0.03 0.32 0.02 0.30 0.02 27 0.36 0.20 0.32 0.09 0.26 0.02 36 2.96 0.69 2.42 0.55 1.73 0.25 38 1.10 0.58 1.16 0.43 0.75 0.18 34 0.38 0.05 0.34 0.05 0.37 0.17 Pre 13.9 0.5 10.1 0.4 9.4 0.6 Non 249.1 8.5 150.7 5.8 84.4 5.0

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 125

Permeability Coefficient, K (nm2) at 50% RH & 73°F Coating Uncalendered Calendered (600 PLI) Calendered (1600 PU) ID Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 6.51 0.72 6.65 0.53 4.68 0.38 6 5.92 0.52 5.53 0.33 4.47 0.21 7 6.26 0.69 5.40 0.19 4.27 0.33 5 5.75 0.41 5.30 0.31 4.20 0.32 13 5.97 0.57 5.49 0.45 4.02 0.20 9 5.99 0.23 5.94 1.03 4.23 0.16 12 6.00 0.39 5.59 0.30 4.41 0.36 10 5.79 0.39 5.25 0.36 4.25 0.31 15 5.68 0.38 5.42 0.72 4.09 0.16 14 5.56 0.45 5.20 0.58 4.04 0.41 18 5.76 0.27 5.23 0.30 3.93 0.15 17 5.83 0.55 4.99 0.45 4.10 0.21 31 5.67 0.34 5.18 0.57 3.93 0.15 30 5.92 0.74 4.90 0.25 4.14 0.18 32 5.89 0.33 4.88 0.22 3.73 0.20 33 5.82 0.50 4.69 0.36 3.99 0.38 19 10.89 3.88 10.01 3.37 5.19 1.36 29 6.71 0.72 6.16 3.79 5.69 0.94 21 5.25 0.62 6.60 3.76 4.07 0.28 25 71.40 14.94 35.11 6.87 29.03 10.91 23 7.42 0.98 7.65 3.10 5.06 0.90 24 5.44 0.36 5.02 0.64 4.20 0.97 29 9.14 3.29 8.57 3.43 7.49 3.22 28 5.54 0.40 4.99 0.35 4.70 0.34 27 6.46 3.54 5.27 1.45 4.15 0.42 36 51.28 11.64 38.77 9.21 27.00 4.03 38 18.90 9.93 18.73 7.12 11.55 2.89 34 6.66 0.90 5.42 0.64 5.81 2.63 Pre 269.6 10.5 169.8 6.6 151.1 12.5 Non 4333.9 146.9 2356.0 113.4 1276.3 76.5

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 126 Appendix D

Surface and Optical Properties Results of COP Coated Samples

PPS Roughness (pm) Coating ID Uncalendered Calendered (600 PLI) Calendered (1600 PLI) Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 4.3 0.15 2.8 0.05 2.6 0.14 6 3.6 0.12 2.3 0.04 2.3 0.13 7 3.5 0.19 2.3 0.11 2.2 0.15 5 3.6 0.15 2.2 0.07 2.0 0.06 13 4.2 0.12 2.7 0.12 2.6 0.11 9 4.2 0.31 2.6 0.09 2.5 0.10 12 4.0 0.16 2.7 0.06 2.4 0.07 10 4.2 0.15 2.5 0.10 2.3 0.11 15 4.6 0.29 2.6 0.08 2.5 0.14 14 4.4 0.65 2.5 0.10 2.4 0.11 18 4.5 0.36 2.5 0.15 2.1 0.20 17 4.3 0.80 2.1 0.10 2.0 0.15 31 3.9 0.31 2.5 0.08 2.4 0.12 30 4.2 0.16 2.5 0.08 2.5 0.11 32 3.9 0.07 2.3 0.06 2.1 0.06 33 4.9 0.34 2.2 0.09 2.1 0.08 19 4.4 0.05 3.3 0.19 3.0 0.19 29 4.5 0.11 3.3 0.64 2.9 0.14 21 4.2 0.23 2.7 0.15 2.5 0.07 25 5.2 0.27 3.8 0.11 3.4 0.16 23 5.0 0.20 3.1 0.10 2.8 0.10 24 4.7 0.13 2.5 0.26 2.4 0.23 29 5.1 0.33 3.5 0.19 3.4 0.16 28 5.1 0.12 3.1 0.06 2.7 0.16 27 4.9 0.22 2.5 0.21 2.4 0.15 36 5.4 0.24 3.8 0.12 3.6 0.18 38 5.4 0.11 4.0 0.03 3.7 0.11 34 5.1 0.12 2.9 0.23 2.9 0.11 Pre 5.7 0.09 3.4 0.08 3.2 0.12 No 5.9 0.08 4.7 0.11 4.3 0.19

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 127

Brightness (%) Coating ID Uncalendered Calendered (600 PLI) Calendered (1600 PLI) Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 83.0 0.22 82.9 0.26 82.4 0.34 6 81.7 0.39 81.7 0.32 81.5 0.48 7 81.0 0.55 80.7 0.35 81.1 0.44 5 79.1 0.34 79.2 0.62 79.2 0.73 13 82.1 0.39 81.9 0.46 82.2 0.42 9 81.6 0.38 81.1 0.67 81.9 0.50 12 81.9 0.13 82.3 0.27 81.2 0.68 10 80.5 0.81 80.2 0.42 80.2 0.80 15 83.2 0.06 83.3 0.06 83.3 0.09 14 83.2 0.06 83.3 0.09 83.0 0.10 18 82.6 0.40 83.1 0.16 82.8 0.13 17 83.0 0.13 82.7 0.26 82.6 0.23 31 82.0 0.28 82.2 0.21 82.0 0.32 30 81.9 0.24 81.3 0.47 81.7 0.41 32 81.3 0.38 81.2 0.46 81.6 0.59 33 79.1 0.61 79.5 0.80 79.8 0.57 19 83.8 0.58 83.0 0.46 81.9 1.71 29 83.0 0.65 82.5 1.33 82.8 0.17 21 81.8 0.61 80.9 0.46 81.1 0.42 25 84.3 0.33 83.3 0.46 82.7 0.51 23 81.7 0.55 80.8 0.47 81.1 0.97 24 79.0 0.80 75.7 0.89 78.4 1.04 29 85.1 0.12 84.6 0.22 84.7 0.07 28 84.9 0.31 84.3 0.39 84.6 0.17 27 83.7 0.39 83.7 0.15 83.8 0.19 36 84.1 0.56 83.9 0.54 83.8 0.65 38 85.2 0.37 84.2 0.37 84.4 0.24 34 82.8 0.70 82.1 0.49 82.4 0.69 Pre 85.1 0.11 85.1 0.32 85.0 0.06 Non 85.3 0.30 85.2 0.25 85.0 0.21

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 128

Hunter Gloss 75° (%) Coating ID Uncalendered Calendered (600 PLI) Calendered (1600 PLI) Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 50.7 1.27 56.7 0.89 61.0 1.13 6 60.8 2.18 68.3 3.15 73.3 1.55 7 60.5 3.33 71.5 2.30 72.5 1.56 5 65.1 1.91 74.4 1.81 76.1 2.07 13 57.9 2.04 64.2 1.48 66.0 1.87 9 59.3 1.89 66.9 2.87 68.6 2.71 12 61.6 2.60 66.1 0.78 69.8 1.91 10 61.5 2.35 72.0 1.25 76.3 2.15 15 54.6 0.82 62.3 0.67 64.7 1.34 14 53.3 0.60 62.4 1.01 64.8 1.95 18 55.2 2.98 62.4 0.78 64.9 1.18 17 50.0 0.57 61.6 0.64 66.3 1.54 31 53.1 1.77 61.8 1.44 66.6 2.21 30 55.6 0.88 62.0 1.25 68.8 1.44 32 55.9 1.18 66.6 1.07 70.2 1.34 33 60.0 0.49 70.5 1.39 73.9 1.88 19 38.5 1.84 46.8 0.94 58.3 3.92 29 42.9 4.20 61.5 3.87 59.0 5.01 21 53.3 3.86 63.3 2.38 67.8 4.04 25 34.8 1.97 43.3 2.45 46.3 2.14 23 46.2 1.27 59.7 3.18 62.5 4.00 24 57.1 1.06 65.3 3.12 75.0 2.60 29 35.8 0.91 45.5 1.07 50.7 2.00 28 38.0 1.15 49.5 0.77 53.2 1.24 27 47.9 4.22 61.4 2.82 63.8 1.36 36 32.9 1.87 42.8 2.89 45.3 1.99 38 29.3 0.94 36.6 1.93 41.2 0.99 34 44.1 1.25 60.0 5.10 56.0 4.37 Pre 16.2 0.42 23.0 0.65 24.9 0.59 Non 22.2 0.79 28.1 0.85 29.1 0.57

Mean of MVTR 400- 300- 400- 200 200 300- Interaction Plot (data means) for MVTR for means) (data Interaction Plot - - srPae oto X61 XP8000 XP6117 Control AstraPlate 0 Statistical Analysis of WVTR Results WVTR of Analysis Statistical Main PlotEffects (data means) for MVTR Coatings a RH Cal 6075 1600 Appendix E E Appendix Non Pre 81 XFBOOO XF6U7 Control AstraPlate Coatings 129 • Design points above predicted value o ago X1 = A: Coatings X2 = C: Coat Wt

Actual Factors 4.90 B: Base = Non D: Calendering = 0 DC E RH = 75 i- >

XFB117 A: Coatings C: Coat Wt

• Design points above predicted value o

X1 = A: Coatings aro X2 = C: Coat Wt

Actual Factors B: Base = Non D: Calendering = 0 E RH = 81 ct >i-

O ortra

XP6117 A: Coatings XR0OOD C: Coat Wt

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. • Design points above predicted value o

X1 = A: Coatings 5.90 X2 = C: Coat Wt Actual Factors B: B ase = Non 4.90 D: Calendering=1600 E RH = 75

> S

Cortid

XP6117 A: Coatings XF0OCD C: Coat

• Design points above predicted value o

X1 = A: Coatings 6 7 0 X2 = C: Coat Wt

Actual Factors B: B ase = Non D: Calendering=1600 E RH = 81

> 2

XF6117 A: Coatings XF8000 C: C«

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission 132 • Design points above predicted value o X1 = A: Coatings 5 X2 = C: Coat Wt Actual Factors B: Base = Pre 4g0 D: Calendering=0 E RH = 75

> 2

Cortid

XPB117 A: Coatings C: Coat Wt

• Design points above predicted value o

X1 = A: Coatings 6.70 X2 = C: Coat Wt

Actual Factors B: Base = Re D: Calendering=0 E RH = 81 cc i- >

C ortfd

XP6117 A: Coatings C: Coat Wt

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 133 • Design points above predicted value o

X1 = A: Coatings X2 = C: Coat Wt Actual Factors B: Base = Pre D: Calende ring = 1600 E RH = 75 I-IT >

XF6117 A: Coatings XP80CD C: Coat Wt

Design points above predicted value

X1 = A: Coatings X2 = C: Coat Wt

Actual Factors 5.95 B: Base = Pre D: Calende ring=1600 E RH = 81

ITH >

Ctxtrol

XP6117 A: Coatings C: Coat Wt

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 134

X1 = A: Coatings X2 = B: Base Actual Factors 6.00 C: Coat Wt = 8.00 D: Calendering^ E RH = 75 5.50

CC I- >

AstraPlate

G ortrd

XP6117 B: Base A: Coatings Nan XP8000

X1 = A: Coatings X2 = B: Base Actual Factors 6 5 0 C: Coat Wt = 8.00 D: Calendering = 0 E RH = 81

cc h- >

AstraPlate

Cbrtrd

XP6117 B: Base A: Coatings Non XP6000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 135 X 1 = A: Coatings X2 = B: Base

Actual Factors 6.00 C: Coat Wt = 8.00 D: Calende ring=1 6 0 0 E RH = 7 5 5.50

5.00 H-cc > 2 4 5 0

4.00

XP6117 B: Base XP0COO A: Coatings

XI = A: Coatings X2 = B: Base Actual Factors C: Coat Wt = 8 .0 0 6 5 0 D: Calendering = 1600 E RH = 81 6 0 0

5 5 0

5 0 0

4.50

4 0 0

XRS117 B: Base Nan XP8000 A: Coatings

Reproducedwith permissionof the copyright owner F „ r i h « owner. E ither reproduction prohibited without permission. 136

X1 = A: Coatings X2 = B: Base Actual Factors C: Coat Wt = 10.00 D: Calendering = 0 E RH = 75

AstraPlate

CQrtrd

XF6117 B: Base A: Coatings Non X X XP0OOO

X1 = A: Coatings X2 = B: Base aso Actual Factors C: Coat Wt = 10.00 D: Calendering = 0 a oo E RH = 81

5 5 0 i-tr > 5 0 0

4.5!

AstraPlate

CQrtrd

XFB117 B: Base A: Coatings

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 137

D: Calende ring=1600

XFB117 A: Coatings XFBOOO

C tx trd

XF6117 A: Coatings XFBOOO

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. X1 = A: Coatings X2 = B: Base Actual Factors C: Coat Wt = 12.00 D: Calendering = 0 E RH = 75

Ctxtrd

XF6117 A: Coatings XP8GOO

X1 = A: Coatings X2 = B: Base Actual Factors C: Coat Wt = 12.00 D: Calendering = 0 E RH = 81

XF6117 A: Coatings XP9Q00

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. X1 = A: Coatings X2 = B: Base Actual Factors C: Coat Wt = 12.00 D: Calende ring=1600 E RH = 75

cn i- > 2 5

Q x trd

XF6117 A: Coatings XFBOOO

X1 = A: Coatings X2 = B: Base Actual Factors C: Coat Wt = 12.00 D: Calende ring=1600 E RH = 81

I-EC > 2 5

Qxtrd

XF6117 A: Coatings XFBOOO

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 140 X1 = A: Coatings X2 = B: Base Actual Factors a oo C: Coat Wt = 14.00 D: Calendering = o E RH = 75 6 5 0

aoo i-oc >

4.90

4.00

B: Base XP6117 XP0OOO A: C oatings

*1 = A: Coatings X2 = B: Base

Actual Factors 6 5 0 C: Coat Wt = 14.00 D: Calendering =0 ERH = 81 6 0 0

5.50

5.00

4.50

C brtrd

XP6117

XPBCOO A: Coatings

Reproduced with permission of the coP y m owner. Further reproductjon prohjbjted ^ 141

X1 = A: Coatings X2 = B: Base a oo Actual Factors C: Coat Wt = 14.00 D: Calende ring=1600 E RH = 75

i-cc >

4.00 AstraPlate

XF6117 B: Base A: Coatings Non XP0OOO

X1 = A: Coatings X2 = B: Base 0 5 0 Actual Factors C: Coat Wt = 14.00 D: Calende ring=1600 E RH = 81

i-cc > 5 0 0

4 0 0 AstraPlate

XF6117 B: Base A: Coatings Non XP8000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 142 Appendix F

COP Screening Data

WVTR Coat PPS Permeability Pigments Thickness (81%RH Wt. Porosity Coefficient Sample & 100°F)

Type (%) (g/m2) Ax (mil) q K (pm2) (g/m2.d) (ml/min) 8604-65 N/A 0 9.6 11.54 0.67 9.64E-06 432.7 8604-65 N/A 0 15.5 11.76 0.01 9.73E-08 348.4 8604-65 N/A 0 17.5 12.06 0.00 0.00E+00 306.0 8618-2 XP8000 5 5.5 12.06 0.74 1.10E-05 609.7 8618-2 XP8000 5 9.2 11.50 0.00 5.71E-08 379.7 8618-2 XP8000 5 16.5 11.58 0.00 0.00E+00 301.5 8618-3 XP8000 30 9.0 11.48 0.14 1.95E-06 446.7 8618-3 XP8000 30 11.5 11.78 0.01 1.83E-07 306.0 8618-3 XP8000 30 15.0 12.06 0.00 0.00E+00 196.5 8604-63 XP8000 55 2.8 11.60 17.02 2.45E-04 797.3 8604-63 XP8000 55 7.2 11.70 2.27 3.30E-05 460.1 8604-63 XP8000 55 12.5 11.54 0.69 9.82E-06 323.8 8604-63 XP8000 55 14.5 11.78 0.59 8.62E-06 209.4 8618-4 XP6117 5 5.5 11.92 0.62 9.20E-06 536.0 8618-4 XP6117 5 15.0 12.12 0.02 3.51E-07 386.4 8618-4 XP6117 5 25.6 12.54 0.00 0.00E+00 270.2 8604-57 ContorX 5 5.7 11.76 0.58 8.50E-06 475.7 8604-57 ContorX 5 10.4 11.90 0.03 4.72E-07 319.4 8604-57 ContorX 5 17.5 12.20 0.00 0.00E+00 252.4 8604-63* XP8000 55 16.27 13.24 0.02 3.94E-07 172.15 8604-63** XP8000 55 16.85 12.52 0.06 8.70E-07 209.37 8604-63+ XP8000 55 17.91 12.72 0.31 4.86E-06 107.01 8604-63++ XP8000 55 16.80 12.94 0.24 3.85E-06 167.49

*CLC-13 gsm pre-coated baseboard, **CLC 7.4 gsm pre-coated baseboard

+SP#1 formulation treated baseboard, ++SP#4 formulation treated baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 143 CHAPTER VII

FLEXURAL STIFFNESS (3-POINT BENDING) OF THE SBS PAPERBOARD COATED WITH HIGH BARRIER SUSTAINABLE COP COATINGS

Lokendra Pal, Margaret K. Joyce, Paul D. Fleming and Charles Ruffner* Center for Coating Development Department of Paper Engineering, Chemical Engineering and Imaging, Western Michigan University, Kalamazoo, MI, USA *MeadWestvaco Corp. Charleston, SC, USA

Abstract

The studies of mechanical properties of SBS paperboard together with barrier

properties are of direct interest to companies seeking to develop an improve package

and quick-service wares. It is very important for packaging made from coated solid

bleached sulfate (SBS) board to maintain flexural (bending) stiffness at high humidity

and temperature applications. Adsorbed water and water vapor affect the thermo

mechanical properties of the chemical components of wood fibers [1]. Water and

water vapor reduces the glass transition temperature (Tg), the modulus, and the

strength due to the plasticization effect, especially at high temperature [1,2].

The flexural stiffness of a coated SBS board is mainly dependent on the

baseboard. The ability of the barrier coating to protect the baseboard against water

and water vapor permeation is the key in retaining the mechanical properties of a

package, especially at high humidity and temperature. This study focuses on the

mechanical properties of a SBS board coated with high barrier sustainable co

polymerized aqueous dispersion coatings.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The flexural stiffness and modulus of SBS paperboard, blade coated with

these coatings was determined from bending load and deflection measurements using

the three point bending test. The mechanical properties of coated samples were

studied through a full factorial design of experiment (DOE) and the relationship

between these coatings, baseboards, fiber orientations, pigments shape factor,

calendering and the mechanical properties at different humidities and temperatures

were investigated.

Analysis of variance (ANOVA) and main effect plot results indicates that all

the studied factors, except pigment shape factor, showed significant impact on

bending load, stiffness and modulus. The barrier coating did not appear to affect

flexural modulus and stiffness at low humidity and temperature, even at high coat

weight. However, the barrier coating did appear to protect the baseboard at high

humidity and temperature, thus retaining higher flexural modulus and stiffness with in

13% of a LDPE extruded commercially produced SBS board. Baseboard pre-coating

doesn’t affect flexural modulus and stiffness. Calendering and relative humidity and

temperature had a detrimental effect on flexural modulus and stiffness.

Introduction

The substrate for packaging board is a complex composite material, which is

mainly composed of wood fibers, fillers and various chemical additives [2]. SBS

baseboard properties depend on the fiber types and extent of fiber-fiber bonding, as

well as, on the network structure [2-7]. The cellulosic fibers are a key constituent of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 145 any paperboard-based packaging [9,10]. In wood, fibers are composed of semi

crystalline cellulose fibrils, surrounded by amorphous hemicellulose, and a lignin

matrix [1-7]. Most of the properties of packaging board are significantly influenced

by the surrounding environment such as ambient relative humidity (RH) and

temperature conditions (Figure 7.1) and by different end uses [2,8,9].

250

Disordered O Hemicelluloses Lignin cx US E-i co

0 10 20 30 40 50 60 Moisture Content (%)

Figure 7.1. Effect of Moisture Content on Glass Transition Temperature (Tg) of Cellulose, Hemicellulose and Lignin [1]

Packaging products made from cellulosic materials are increasingly being

modified and improved for better performance. The performance properties [3] can be

subdivided into strength, stiffness, box compression strength, creasability and

foldability, flatness and dimensional stability, runnability, sealability, and barrier

characteristics. Adsorption and absorption of water and water vapor have

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. repercussions with respect to the barrier and mechanical properties of the paperboard

system [4-14]. The mechanical properties depends on baseboard, pigment and binder

types, coating thickness, and calendering operations [15,16].

In this study, first HSFE clays were modified by the addition of silane through

a wet treatment process. Next, acrylic co-monomers were polymerized in the presence

of three different, finely dispersed HSFE clays; XP6117, Astra Plate and XP8000, to

prepare the co-polymerized coatings. The mechanical properties of cylindrical

laboratory coater (CLC) blade coated SBS paperboard were studied, and the

relationship between these coatings, baseboards, fiber orientations, pigments shape

factor, calendering and the mechanical properties at different humidity and

temperature was investigated. For the purpose of comparison, a commercially

available pigment coated, low density polyethylene (LDPE) coated and non- coated

baseboards were used.

Experimental Design

This work is divided into three phases: (1) to develop COP coatings by

polymerizing acrylic co-monomers with HSFE clays, (2) to apply COP coatings onto

pre-coated, as well as on non-pre-coated baseboard using a cylindrical laboratory

coater (CLC), and (3) to characterize mechanical (flexural load, stiffness and

modulus) properties the COP coated samples

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Materials

Two commercial baseboard; pre-coated and non-pre-coated were used as the

substrate for the COP coatings. The base substrate characteristics are given in Table

7.1. The values represented are averages of ten measurements. The acrylic co

monomers were used in the emulsion polymerization reaction. The molecular weight,

Brookfield viscosity, average particle size, solid content and pH of the control

emulsion, are given in Table 7.2. The control emulsion has no HSFE clay present.

The characteristics of HSFE clays according to manufacturer (Imerys, Roswell, GA)

are given in Table 7.3. Three different, finely dispersed HSFE clays, XP6117, Astra

Plate and XP8000 were used to develop the co-polymerized coatings.

Table 7.1. The Characteristics of the Uncalendered Baseboards (Stdev. in Parenthesis)

Substrate Properties Solid Bleached Sulfate Precoated Bleached (SBS) Baseboard Baseboard

Pre-coating No Yes

Grammage, g/m2 270 (2.8) 284 (2.7)

Thickness, mils 14.20 (0.45) 15.66 (0.21)

Load, N 3.38 (0.05) 3.60 (0.06) 3-Point Bending Instron Tester Modulus, GPa 4.00(0.16) 5.36 (0.09)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 148 Table 7.2. The Characteristics of the Control Binder Used for COP Coatings

Molecular Wt. Viscosity Avg. Particle Binder Solids (%) pH (g/mol) (cps) Size (nm)

Control 50-52 200000-500000 6.5 - 7.5 400 80-100

Table 7.3. The Characteristics of the Mineral Pigments Used for COP Coatings

Shape Plate Thickness BET Surface Mineral Pigment D 50 (nm) Factor (nm) Area, m2/g XP6117 150-200 10-20 40 20-22

Astra Plate 450-550 25-32 70 16-18

XP8000 450-550 50-60 40 18-20

Coating Formulations and Application Methods

Co-polymerized coatings with three HSFE clays were obtained. All COP

coatings were loaded with 30% HSFE clays on dry weight of binder (see Table 7.4).

The solids in the coatings were measured using a Labwave solids analyzer and the

Brookfield viscosities were measured at 100 rpm using # 3 spindle with an LVT

digital viscometer at room temperature.

The Hercules high shear viscosity was also measured at 4800 RPM using an

E-bob, ramp time of 20 second. Table 7.4 shows the viscosities and solids content of

the COP coatings. The coatings’ water retention values were measured using AAGR

as per TAPPI standard (T-701) as shown in Table 7.4. The COP coatings were

applied with a blade using a cylindrical laboratory coater (CLC) at 1500 ft/min at

different coat weights.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 149 Table 7.4. The Wet Coating Characteristics of the COP Coatings

Pigment Viscosity, cps Coatings Solids, % WRV, g/m2 Loading, % Brookfield HHSV

Control 0 51.0 174.4 365 41.3

XP8000 30 44.1 71.6 216 12.9

Astra 30 45.7 79.1 116 15.1

XP6117 30 44.8 92.6 412 20.1

Calendering and Conditioning of Samples

The COP coated samples were calendered at 1600 PLI, 2-nip smooth side. All

the coated paperboard samples were conditioned for 24 h at 50% RH and 23°C (73.4

°F) before any measurements were made.

3 Point Bending Test Procedure

The samples were then tested for flexural (bending) stiffness using 3-point

bending test. Measurements were carried out at 50% RH and 73°F as well as at 81%

RH and 100°F, each of which is the average of four tests respectively. The test setup

for 3-point bending is shown in Figure 7.2. A rectangular geometry of 25.4 mm wide

and 19.0 mm span was used. The test was carried using a 19.6 N load cell. All of the

data were collected using displacement control mode. In this control mode, the

paperboard was deflected to 1.0 mm and the load was measured. It is also possible to

conduct tests using load control. That is, the applied load is maintained constant, and

the board deflects accordingly.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 7.2. Three Point Bending Test Setup

A paperboard sample bends when a momentum is generated by discrete

loading of the sample on two support points (3-point bending) [17-20]. During

bending; the fibers inside the sample with respect to its curvature are in compression

whereas the fibers outside the sample are in tension. At the neutral axis the stresses

and the deformation of the sample is equal to zero. The neutral axis lies in the center

of the homogenous sample with a symmetrical cross-section, whereas in

inhomogeneous samples, its position is where equilibrium forces are balanced i.e. the

compression and tensile forces are equal. The deformations and the stresses increase

with distance from the neutral axis. Assuming that the samples are homogenous leads

to the following relation for the calculation of the bending stiffness, BS [17-20]

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The calculated bending stiffness from experimental data is a test geometry dependent property. The deflection at the midpoint of a sample subjected to 3-point bending is given by [19-21]:

(Vn.2)

where

E= bending elastic modulus I = moment of inertia of cross-section with respect to neutral axis (l/12)*(bd3) b = width of the board d = the board thickness F= bending load L = the support span (sample length) 8 = the deflection

The material properties such as modulus can be determined by measuring

experimentally the ratio of load (F) and corresponding deflection ( 8 f ) from the bending test measurements. A stiffness measured this way is called the flexural modulus. In 3-point bending deflection, the sample experiences both flexural and shear stresses. Hence, the bending stiffness calculated from the above equation is a combination of flexural stiffness and shear stiffness of the sample. The maximum bending (a) and shear (x) stresses in the 3 point bending are determined from the following relationships respectively [22,23]:

My (vn.3) max I

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 152

(vn.4)

where

M = bending moment (F/2)*(L/2) V= shear force (F/2) y = distance form neutral axis to point of stress (d/2) A = area of cross-section (d*b)

As expected, the flexural stresses increases with test span due to their

dependence on bending moment (FL), but the shear stresses remain constant due to its

dependence on shear force only (F). At long spans the shear deflection becomes

insignificant as compared to the total deflection. At long spans, therefore, the

apparent stiffness of the sample reaches the true flexural stiffness. However, the load

measuring instrument should be sensitive enough to measure decreasing bending load

at longer test span.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 153 Table 7.5. Sample IDs for Different COP Coatings and Substrates

Precoated Baseboard Non Precoated Baseboard Pigments ID Coat Wt. (g/m2) ID Coat Wt. (g/m2) 3 2.5 19 6.8 6 8.1 20 13.6 XP8000 7 13.1 21 21 5 19.3 13 5.0 25 12.6 9 9.4 23 18 XP6117 12 14.3 24 27.7 10 16.6 15 3.7 29 8.4 14 6.9 28 13 Control 18 11.7 27 23.7 17 13.3 31 4.2 36 5.7 30 7.4 38 7.9 Astra Plate 32 8.9 34 15.2 33 16.0

Results and Discussion

Table 7.6 shows the design summary and analysis of variance (ANOVA) for

the three point bending load data. An analysis of variance revealed significant

differences among studied factors. The factors- calendering, cross-machine direction,

and testing environment (RH and temperature) showed significant impact on bending

load and stiffness whereas coatings, coat weight, and baseboard showed less of an

impact. Appendix B summarizes the bending (flexural) load and modulus results of

uncalendered and calendered samples at 50%RH & 73°F and 81% RH and 100°F.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 7.3 compares the loss in bending load of baseboard, COP coated, and

LDPE extruded samples. The barrier coating appears to protect the baseboard from

mechanical strength loss at high humidity and temperature, thus retaining a bending

load with in 13% of a LDPE extruded commercially produced SBS board. Figures 7.4

to 7.11, show the effect of barrier coatings, baseboards, relative humidities and

temperatures and calendering on flexural modulus. All the barrier coatings gave

similar flexural load and modulus results. Two different baseboards, pre and non pre-

coated were studied to compare their surface structure effect on coating application

and mechanical properties. There were no significant differences in mechanical

properties between pre-coated and non pre-coated baseboard samples.

The results showed the barrier coatings to have an effect on the flexural load

and modulus of the paperboard samples at high humidity and temperature. At high

humidity and temperature, the flexural load and modulus of co-polymerized coatings

increased up to 30% compared to untreated baseboards. This indicates that platy

pigments can serve in retaining the mechanical strength of baseboard under high

relative humidity and temperature. The barrier coating seems to protect the baseboard

at high humidity and temperature conditions owing to their increased tortuosity and

hence less permeation of water and water vapor through the coating layer.

Figures 7.4 and 7.5, compare the flexural modulus of barrier coated samples

of pre-coated baseboard at 50%RH & 73°F and 81% RH and 100°F. Figures 7.6 and

7.7, compare the flexural modulus of barrier coated samples of non pre-coated

baseboard at 50%RH & 73°F and 81% RH and 100°F. It is obvious that the flexural

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. modulus will decrease with humidity and temperature due to softening of the

chemical components of wood fibers due to plasticization effect of water and water

vapor. There was up to 50 % decrease in the flexural modulus from 50%RH & 73°F

to 81 %RH & 100°F whereas up to 70 % decrease in the flexural modulus of untreated

baseboard. Again, indicating the importance of barrier coatings.

Figures 7.4 and 7.8, compare the flexural modulus of barrier coated

calendered and uncalendered samples of pre-coated baseboard. The calendering has

significant effect on flexural load and modulus. As expected, flexural load and

modulus decreased with calendering due to reduction in paperboard thickness.

Densification of the composite (baseboard and coating layer) structure through

calendering was detrimental to flexural modulus and stiffness.

150%RH ■ 81%RH 3.8

3.0

2.3 13 1.5

0.8

0.0 -t LDPE XP8000 XP6117 Astra Base (SF 50-60) (SF 10-20) (SF 25-35)

Figure 7.3. Comparison of Loss in Bending Load of Different Samples at 50 and 81% Humidity

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 156 Table 7.6. Design Summary and Analysis of Variance (ANOVA) of COP Coated Samples Using Design-Expert

Design Summary

Load (N) versus Coating, Baseboard, Coat Weight, Calendering, CMD and RH

Factor Name Units Values Levels XP8000, XP6117, A Coating 4 AstraPlate, Control B Base Non, Pre 2 C Coat Wt g/m2 A, B, C, D 4 D Calendering PLI 0, 1600 2 E CMD MD, CD 2 F RH % 50,81 2 Response Name Units Obs Analysis Y1 Load N 896 Factorial

ANOVA Table (see Appendix for full ANOVA Table)

Sum of Mean Source df F-Value p-value Squares Square

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 157

♦ XP8000 ■ XP6117 ▲ Astra • Control 4.2

4.0

C/5

! 3.8 -a 1 , 6 P-c

3.4 0 4 8 12 16 Coat Wt. (g/m )

Figure 7.4. Comparison of Flexural Modulus at 50% RH& 73°F of COP Coated Uncalendered Samples Using Pre-coated Baseboard

♦ XP8000 IXP6117 ▲ Astra 1 Control 1.9

1.7 O

c/a *3 1.5 • ♦ O Cd 1.3 UDh OX E 1.1

0.9 8 12 16 20 Coat Wt. (g/m2)

Figure 7.5. Comparison of Flexural Modulus at 81% RH & 100°F of COP Coated Uncalendered Samples Using Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 158

♦ XP8000 ■ XP6117 A Astra • Control 5.4

5.2 (2 S 5.0 c/5

1 48 ^ 4.6 2 § 4.4 E 4.2

4.0 0 4 8 12 16 20 24 28 Coat Wt. (g/rn)

Figure 7.6. Comparison of Flexural Modulus at 50% RH & 73°F of COP Coated Uncalendered Samples Using Non Pre-coated Baseboard

♦ XP8000 HXPdlU A Astra •Control 2.8 2.6 g 2.4 i 1 2 1-8 3 Ji 1.6 E l.4

1.2 0 4 8 12 16 20 24 28 Coat Wt. (g/rn)

Figure 7.7. Comparison of Flexural Modulus at 81% RH & 100°F of COP Coated Uncalendered Samples Using Non Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 159

♦ XP8000 XP6117 A Astra • Control 4.6 4.4 Oh O 4.2 4.0 • A a " 3.8 • ♦

2 3.6 P

Figure 7.8. Comparison of Flexural Modulus at 50% RH & 73°F of COP Coated Calendered Samples Using Pre-coated Baseboard

♦ XP8000 IXP6117 A Astra • Control 2.1

1.9 O&h O C/3 1.7 J3 3 ■o o 1.5

1.3

1.1

0.9 I 4 8 12 16 20 Coat Wt. (g/m)

Figure 7.9. Comparison of Flexural Modulus at 81% RH & 100°F of COP Coated Calendered Samples Using Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 160

♦ XP8000 ■ XP6117 A Astra •Control 5.8 - 5.6 - C5 £ 5 -4 " i 5 -2 _ •3 5.0 - I 4.8 - 13 . £ 4.6 - * .2 4.4 - Uh 4.2 - 4.0 - 0 4 8 12 16 20 24 28 Coat Wt. (g/m2)

Figure 7.10. Comparison of Flexural Modulus at 50% RH & 73°F of COP Coated Calendered Samples Using Non Pre-coated Baseboard

♦ XP8000 XP6117 A Astra • Control 2.8

2.6 Oh o 2.4 •O3 o 2.2

V-3 3 2.0 X CD 1.8

1.6 I 0 12 16 2 0 24 28 Coat Wt. (g/m )

Figure 7.11. Comparison of Flexural Modulus at 81 % RH & 100°F of COP Coated Calendered Samples with Non Pre-coated Baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 161 Conclusions

The flexural stiffness and modulus of SBS paperboard, coated with different

shape engineered pigments based barrier coatings was determined from bending load

and deflection measurements using three point bending test. The mechanical

properties of coated samples were studied through a full factorial design of

experiment (DOE) and the relationship between these coatings, baseboards, fiber

orientations (MD/CD), pigments shape factor, calendering and the mechanical

properties at different humidities and temperatures were investigated.

Analysis of variance (ANOVA) and main effect plot results indicates that all

the studied factors except pigment shape factor showed significant impact on bending

load, stiffness and modulus. The barrier coating did not affect flexural modulus and

stiffness at low humidity and temperature, even at high coat weight. The barrier

coating appears to protect the baseboard from mechanical strength loss at high

humidity and temperature, thus retaining a flexural modulus and stiffness with in 13%

of a LDPE extruded commercially produced SBS board. The maintenance of bending

stiffness can be improved further with a C2S (coated both sides). Baseboard pre

coating didn’t affect flexural modulus and stiffness. Calendering and relative

humidity and temperature had a detrimental effect on flexural modulus and stiffness.

Densification of the composite (baseboard and coating layer) structure through

calendering was also detrimental to flexural modulus and stiffness.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 162 References

1. Peel, D. P., Paper Science and Paper Manufacture, 1999 Vancouver: Angus Wilde Publication.

2. J. Kline, “ Paper and Paperboard”, 2nd Ed., Miller Freeman Publishing, San Francisco, 1991.

3. W. E. Scott, “Properties of Paper: An Introduction”, TAPPI Press, 1989 Atlanta, GA.

4. D. Twede and S. E. M. Selke, Cartons, Crates and Corrugated Board: Handbook o f Paper and Wood Packaging Technology, DEStech, Lancaster, PA, 2005.

5. Caulfield D.F., Passaretti J.D., and Sobczynski, S.F, “Materials Interactions Relevant to the Pulp, Paper, and Wood Industries”, Materials Research Society Symposium Proceedings, Volume 197, April 18-20, 1990, San Francisco, California, U.S.A.

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9. Kretschmann, D.E., “Micromechanical Measurement of Wood Substructure Properties”, In: Proceedings of the 2002 SEM Annual Conference & Exposition on Experimental and Applied Mechanics, June 10-12, 2002, Milwaukee, Wisconsin. Published by the Society for Experimental Mechanics, Inc. c2002.

10. Carlson, L. Fillers, C. and De Ruvo, A., “The Mechanism of Failure in Bending of Paperboard”, Journal of Material Science (15):2636-2642 (1980)

11. Dunn, H., “Micromechanisms of Paperboard Deformation”, MS Thesis, Department of Mechanical Engineering, MIT, 2000

12. Wang, J. Z. et al., “Transient Moisture Effect in Fibers and Composite Materials”, Journal of Composite Materials, 24:994-1009, 1990.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 163 13. Fellers, C. and Panek, J., “Effect of Relative Humidity Cycling on Mechanosorptive Creep: In Moisture and Creep Effects on Paper, Board and Containers”, 5th International Symposium, Marysville, Victoria, Australia, 2001.

14. Dullien, F. et al., “Porous Media, Fluid Transport and Pore Structure”, 1992, Academic Press Inc., San Diego

15. Kim-Habermehl et al., “Coated Paper Stiffness: A Practical Perspective”, 2000 International Printing & Graphic Arts Conference Proceedings

16. Okomori, K. and Enomae, T., “Evaluation and Control of Coated Paper Stiffness”, 1999 Coating Fundamentals Symposium Proceedings

17. Lange, J., Pelletier, C., and Wyser, Y., “ Modeling and Measuring the Bending Stiffness of Flexible Packaging Materials”, the PLACE, March 2002 PFFC

18. Nieman, K., and Ostade, A.B.V., “PRO® RESINS: Optimizing Performance in Microwave-Only Packaging”, Polymers, Laminations and Coatings, A TAPPI PRESS Anthology of Published Papers, 1986-1991

19. McKee, R.C., Gander, J. W., and Wachuta, J. R., “ Flexural Stiffness of Corrugated Board”, The Institute of Paper Chemistry, Appleton, Wisconsin

20. Timoshenko, P. S., and Gere, M. J., “Mechanics of Materials” 4th Edition Boston : PWS Pub Co., cl997.

21. David Roylance, D., “Beam Displacements”, http://web.mit.edu/course/3/3.11 /www/modules/bdisp.pdf. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, Nov. 30, 2000

22. Egle, D.M., “An Approximate Theory for Transverse Shear Deformation and Rotatory Inertia Effects in Vibrating Beams”, NASA CR-1317, http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690014678 1969014678. pdf

23. Mark, R.E. et al., “Handbook of Physical Testing of Paper”, 2nd Edition, Pub. by Marcel Dekker, Inc., 2002

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix A

Analysis of Variance (ANOVA) of COP Coated Samples Using Design-Expert

Sum of Mean Source df F-Value p-value Squares Square

Model 749.76 118 6.35 317.35 <0.0001 A-Coating 0.81 3 0.27 13.45 < 0.0001 B-Base 0.48 1 0.48 24.20 < 0.0001 C-Coat Wt 0.15 3 0.05 2.49 0.0588 D-Calendering 59.95 1 59.95 2994.36 < 0.0001 E-CMD 221.92 1 221.92 11084.03 < 0.0001 F-RH 364.21 1 364.21 18190.67 < 0.0001 AB 1.08 3 0.36 17.91 <0.0001 AC 0.38 9 0.04 2.11 0.0265 AD 0.13 3 0.04 2.14 0.0942 AE 0.48 3 0.16 8.07 <0.0001 AF 0.65 3 0.22 10.88 < 0.0001 BC 0.25 2 0.13 6.26 0.0020 BD 2.64 1 2.64 132.10 < 0.0001 BE 1.70 1 1.70 85.10 < 0.0001 BF 0.30 1 0.30 15.02 0.0001 CD 0.03 3 0.01 0.51 0.6729 CE 0.01 3 0.00 0.22 0.8804 CF 0.23 3 0.08 3.75 0.0108 DE 16.33 1 16.33 815.73 <0.0001 DF 19.03 1 19.03 950.60 < 0.0001 EF 45.18 1 45.18 2256.73 < 0.0001

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 165

Sum of Mean Source df F-Value p-value Squares Square ABC 0.05 6 0.01 0.39 0.8851 ABD 0.13 3 0.04 2.23 0.0834 ABE 0.36 3 0.12 5.94 0.0005 ABF 1.12 3 0.37 18.67 < 0.0001 ACD 0.99 9 0.11 5.47 <0.0001 ACE 0.27 9 0.03 1.49 0.1484 ACF 1.05 9 0.12 5.84 < 0.0001 ADE 0.02 3 0.01 0.32 0.8077 ADF 0.09 3 0.03 1.42 0.2368 AEF 0.17 3 0.06 2.85 0.0368 BCD 0.23 2 0.11 5.72 0.0034 BCE 0.19 2 0.10 4.78 0.0086 BCF 0.22 2 0.11 5.51 0.0042 BDE 0.98 1 0.98 48.72 <0.0001 BDF 0.68 1 0.68 33.88 <0.0001 BEF 0.66 1 0.66 32.78 < 0.0001 CDE 0.06 3 0.02 1.00 0.3926 CDF 0.12 3 0.04 2.06 0.1042 CEF 0.02 3 0.01 0.38 0.7699 DEF 4.41 1 4.41 220.29 < 0.0001 Residual 15.56 777 0.02 Lack of Fit 5.70 105 0.05 3.70 <0.0001 Pure Error 9.86 672 0.01 Cor Total 765.32 895

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 166 Appendix B

3-Point Bending Test Results of COP Coated Samples

Load at Yield (N)- Uncalendered Samples Ctg 50% RH & 73°F 81% RH & 100°F ID MD CD MD CD Avg. Stdev. Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 3.28 0.10 1.64 0.02 1.29 0.27 0.69 0.12 6 3.49 0.21 1.57 0.09 1.34 0.27 0.52 0.07 7 3.49 0.06 1.79 0.08 1.42 0.18 0.57 0.03 5 3.49 0.18 1.50 0.12 1.33 0.12 1.49 0.14 13 3.42 0.12 1.78 0.07 1.51 0.23 0.84 0.08 9 3.60 0.19 1.76 0.03 1.40 0.17 0.69 0.09 12 3.60 0.21 1.76 0.08 1.42 0.27 0.68 0.11 10 3.73 0.07 1.80 0.04 1.31 0.16 0.64 0.06 15 3.41 0.03 1.65 0.06 1.19 0.08 0.46 0.03 14 3.33 0.06 1.66 0.08 1.35 0.17 0.66 0.05 18 3.59 0.04 1.69 0.05 1.23 0.27 0.52 0.11 17 3.47 0.21 1.70 0.04 1.09 0.16 0.54 0.10 31 3.75 0.09 1.75 0.06 1.21 0.21 0.60 0.06 30 3.60 0.15 1.71 0.06 1.25 0.15 0.62 0.09 32 3.49 0.10 1.79 0.06 1.20 0.18 0.61 0.03 33 3.67 0.14 1.82 0.02 1.21 0.12 0.62 0.13 19 3.50 0.17 1.62 0.04 1.50 0.18 0.63 0.14 20 3.46 0.20 1.57 0.06 1.29 0.30 0.67 0.08 21 3.68 0.13 1.48 0.06 1.43 0.19 0.65 0.07 25 3.52 0.16 1.58 0.10 1.40 0.20 0.64 0.13 23 3.51 0.23 1.49 0.13 1.16 0.21 0.70 0.12 24 3.50 0.09 1.61 0.03 1.08 0.27 0.44 0.09 29 3.38 0.07 1.41 0.05 1.05 0.29 0.59 0.19 28 3.23 0.11 1.41 0.07 1.88 0.24 0.88 0.07 27 3.27 0.13 1.42 0.06 1.90 0.19 0.90 0.01 36 3.18 0.17 1.35 0.07 1.51 0.27 0.78 0.12 38 3.21 0.13 1.40 0.04 0.92 0.12 0.53 0.16 34 3.32 0.15 1.52 0.10 0.91 0.21 0.78 0.10 Pre 3.73 0.15 1.85 0.06 1.15 0.06 0.46 0.09 Non 3.60 0.06 1.51 0.16 1.16 0.04 0.48 0.05

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 167

Load at Yield (N)- Calendered Samples 50% RH & 73°F 81% RH & 100°F CtgID MD CDMDCD Avg. Stdev. Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 2.26 0.12 1.29 0.03 0.95 0.09 0.51 0.11 6 2.11 0.05 1.20 0.08 0.83 0.10 0.59 0.06 7 1.99 0.08 1.26 0.06 0.51 0.08 0.78 0.12 5 2.05 0.10 1.28 0.04 0.77 0.08 0.54 0.10 13 2.32 0.09 1.24 0.08 0.94 0.08 0.49 0.05 9 2.24 0.06 1.27 0.09 0.95 0.12 0.51 0.06 12 1.79 0.05 1.22 0.05 0.97 0.13 0.58 0.11 10 2.01 0.14 1.34 0.14 0.84 0.07 0.49 0.07 15 1.88 0.21 1.19 0.04 0.88 0.11 0.53 0.04 14 2.13 0.11 1.18 0.08 0.81 0.07 0.51 0.05 18 1.98 0.07 1.20 0.02 0.84 0.08 0.49 0.09 17 2.00 0.11 1.23 0.09 0.88 0.08 0.54 0.07 31 1.92 0.13 1.24 0.10 0.81 0.05 0.51 0.08 30 2.12 0.12 1.26 0.04 0.79 0.04 0.43 0.07 32 2.03 0.10 1.30 0.05 0.81 0.07 0.49 0.03 33 2.09 0.05 1.29 0.03 0.84 0.04 0.57 0.08 19 2.70 0.16 1.34 0.02 1.24 0.16 0.67 0.12 20 2.38 0.14 1.06 0.05 1.21 0.14 0.67 0.23 21 2.88 0.15 1.21 0.13 1.19 0.18 0.59 0.06 25 2.51 0.12 1.21 0.05 1.04 0.05 0.49 0.10 23 2.46 0.12 1.21 0.06 0.88 0.07 0.52 0.09 24 2.72 0.16 1.43 0.10 1.08 0.15 0.60 0.09 29 2.70 0.15 1.24 0.11 1.15 0.13 0.53 0.07 28 2.09 0.08 1.00 0.11 1.33 0.22 0.62 0.15 27 2.60 0.12 1.11 0.11 1.18 0.13 0.51 0.04 36 2.20 0.20 1.01 0.08 0.81 0.19 0.53 0.10 38 2.32 0.07 1.13 0.06 0.97 0.03 0.55 0.07 34 2.44 0.12 1.17 0.06 1.07 0.13 0.64 0.10 Non 1.97 0.04 0.88 0.09 0.68 0.09 0.21 0.06

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Bending Stress (MPa) Uncalendered Samples

CtgID 50% RH & 730F 81% RH & 1000F MD CD MD CD Avg. Stdev. Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 23.80 0.70 11.89 0.14 9.38 1.92 4.99 0.85 6 24.96 1.47 11.23 0.66 9.60 1.94 3.74 0.52 7 24.86 0.46 12.76 0.53 10.13 1.31 4.05 0.19 5 24.68 1.27 10.65 0.85 9.42 0.86 10.57 0.96 13 24.90 0.85 12.93 0.52 11.01 1.70 6.13 0.58 9 26.02 1.40 12.76 0.18 10.11 1.22 5.02 0.64 12 26.67 1.52 13.06 0.56 10.54 2.02 5.06 0.84 10 26.35 0.46 12.67 0.31 9.21 1.10 4.49 0.43 15 24.23 0.22 11.74 0.43 8.46 0.55 3.26 0.22 14 23.78 0.41 11.85 0.57 9.64 1.19 4.73 0.39 18 24.28 0.24 11.47 0.36 8.33 1.82 3.49 0.72 17 23.89 1.45 11.72 0.30 7.53 1.13 3.73 0.69 31 26.72 0.66 12.47 0.40 8.64 1.50 4.25 0.45 30 25.63 1.03 12.18 0.42 8.87 1.08 4.41 0.66 32 24.65 0.67 12.62 0.45 8.45 1.27 4.30 0.20 33 24.63 0.93 12.21 0.16 8.10 0.79 4.16 0.87 19 29.67 1.47 13.76 0.34 12.69 1.53 5.29 1.19 20 29.89 1.73 13.55 0.51 11.17 2.56 5.76 0.66 21 31.32 1.14 12.55 0.54 12.20 1.64 5.49 0.58 25 30.83 1.43 13.81 0.87 12.27 1.77 5.57 1.13 23 29.85 1.97 12.66 1.06 9.90 1.76 5.92 1.04 24 28.17 0.68 12.93 0.23 8.68 2.13 3.52 0.69 29 29.43 0.63 12.25 0.44 9.13 2.49 5.16 1.68 28 27.22 0.95 11.91 0.62 15.84 2.00 7.45 0.62 27 27.18 1.08 11.82 0.46 15.78 1.58 7.50 0.07 36 28.37 1.51 12.05 0.63 13.49 2.43 6.93 1.04 38 28.69 1.15 12.49 0.32 8.21 1.09 4.73 1.47 34 28.32 1.28 12.93 0.84 7.75 1.81 6.66 0.84 Pre 26.44 1.09 13.13 0.42 8.14 0.42 3.23 0.65 No 31.77 0.54 13.30 1.40 10.24 0.34 4.24 0.42

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 169

Bending Stress (MPa) Calendered Samples 50% RH & 730F 81% RH & 1000F CtgID MD CDMD CD Avg. Stdev. Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 23.46 1.24 13.43 0.30 9.85 0.97 5.29 1.19 6 21.06 0.51 11.98 0.76 8.32 1.01 5.85 0.61 7 21.06 0.80 13.28 0.64 5.35 0.80 8.19 1.31 5 20.22 0.96 12.67 0.42 7.57 0.76 5.33 0.97 13 23.66 0.94 12.60 0.76 9.61 0.83 5.00 0.46 9 22.61 0.64 12.79 0.86 9.58 1.18 5.15 0.57 12 17.73 0.46 12.09 0.53 9.57 1.28 5.70 1.10 10 19.89 1.34 13.27 1.38 8.34 0.69 4.80 0.69 15 19.04 2.09 12.01 0.40 8.90 1.10 5.37 0.43 14 22.17 1.18 12.32 0.87 8.44 0.77 5.26 0.48 18 20.88 0.70 12.62 0.17 8.88 0.84 5.21 0.93 17 20.18 1.06 12.43 0.95 8.89 0.77 5.49 0.70 31 21.33 1.41 13.77 1.05 8.96 0.50 5.64 0.93 30 22.07 1.28 13.14 0.44 8.27 0.44 4.48 0.77 32 21.81 1.04 13.94 0.49 8.68 0.74 5.28 0.32 33 22.26 0.58 13.72 0.34 8.97 0.41 6.09 0.87 19 27.05 1.64 13.39 0.21 12.41 1.63 6.65 1.20 20 25.42 1.48 11.34 0.50 12.92 1.50 7.16 2.48 21 30.77 1.59 12.95 1.33 12.72 1.90 6.27 0.68 25 27.90 1.37 13.47 0.57 11.62 0.52 5.50 1.12 23 26.25 1.26 12.90 0.64 9.35 0.70 5.50 0.94 24 27.84 1.62 14.64 0.97 11.02 1.57 6.18 0.93 29 28.47 1.58 13.05 1.18 12.06 1.35 5.58 0.77 28 22.26 0.83 10.67 1.15 14.22 2.39 6.62 1.58 27 26.96 1.24 11.54 1.18 12.19 1.36 5.28 0.46 36 24.06 2.21 11.03 0.92 8.83 2.09 5.84 1.14 38 26.49 0.75 12.93 0.66 11.09 0.32 6.24 0.81 34 26.26 1.29 12.66 0.61 11.58 1.43 6.89 1.06 Non 23.05 0.51 10.29 1.05 7.92 1.00 2.42 0.71

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Shear Stress (MPa) Uncalendered Samples 50% RH & 730F 81% RH & 1000F CtgID MD CD MD CD Avg. Stdev. Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 0.25 0.01 0.12 0.00 0.10 0.02 0.05 0.01 6 0.26 0.02 0.12 0.01 0.10 0.02 0.04 0.01 7 0.26 0.00 0.13 0.01 0.11 0.01 0.04 0.00 5 0.26 0.01 0.11 0.01 0.10 0.01 0.11 0.01 13 0.26 0.01 0.13 0.01 0.11 0.02 0.06 0.01 9 0.27 0.01 0.13 0.00 0.10 0.01 0.05 0.01 12 0.27 0.02 0.13 0.01 0.11 0.02 0.05 0.01 10 0.28 0.00 0.13 0.00 0.10 0.01 0.05 0.00 15 0.25 0.00 0.12 0.00 0.09 0.01 0.03 0.00 14 0.25 0.00 0.12 0.01 0.10 0.01 0.05 0.00 18 0.26 0.00 0.12 0.00 0.09 0.02 0.04 0.01 17 0.25 0.02 0.12 0.00 0.08 0.01 0.04 0.01 31 0.28 0.01 0.13 0.00 0.09 0.02 0.04 0.00 30 0.27 0.01 0.13 0.00 0.09 0.01 0.05 0.01 32 0.26 0.01 0.13 0.00 0.09 0.01 0.05 0.00 33 0.27 0.01 0.13 0.00 0.09 0.01 0.04 0.01 19 0.28 0.01 0.13 0.00 0.12 0.01 0.05 0.01 20 0.28 0.02 0.13 0.00 0.11 0.02 0.05 0.01 21 0.30 0.01 0.12 0.01 0.12 0.02 0.05 0.01 25 0.29 0.01 0.13 0.01 0.12 0.02 0.05 0.01 23 0.29 0.02 0.12 0.01 0.09 0.02 0.06 0.01 24 0.28 0.01 0.13 0.00 0.09 0.02 0.03 0.01 29 0.28 0.01 0.12 0.00 0.09 0.02 0.05 0.02 28 0.26 0.01 0.11 0.01 0.15 0.02 0.07 0.01 27 0.26 0.01 0.11 0.00 0.15 0.02 0.07 0.00 36 0.26 0.01 0.11 0.01 0.13 0.02 0.06 0.01 38 0.27 0.01 0.12 0.00 0.08 0.01 0.04 0.01 34 0.27 0.01 0.12 0.01 0.07 0.02 0.06 0.01 Pre 0.28 0.01 0.14 0.00 0.09 0.00 0.03 0.01 No 0.30 0.01 0.12 0.01 0.10 0.00 0.04 0.00

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 171

Shear Stress (MPa) Calendered Samples 50% RH & 730F 81% RH & 1000F CtgID MD CD MDCD Avg. Stdev. Avg. Stdev. Avg. Stdev. Avg. Stdev. 3 0.20 0.01 0.12 0.00 0.09 0.01 0.05 0.01 6 0.19 0.00 0.11 0.01 0.07 0.01 0.05 0.01 7 0.18 0.01 0.11 0.01 0.05 0.01 0.07 0.01 5 0.18 0.01 0.11 0.00 0.07 0.01 0.05 0.01 13 0.21 0.01 0.11 0.01 0.08 0.01 0.04 0.00 9 0.20 0.01 0.11 0.01 0.08 0.01 0.05 0.00 12 0.16 0.00 0.11 0.00 0.08 0.01 0.05 0.01 10 0.18 0.01 0.12 0.01 0.07 0.01 0.04 0.01 15 0.17 0.02 0.11 0.00 0.08 0.01 0.05 0.00 14 0.19 0.01 0.11 0.01 0.07 0.01 0.05 0.00 18 0.18 0.01 0.11 0.00 0.08 0.01 0.04 0.01 17 0.18 0.01 0.11 0.01 0.08 0.01 0.05 0.01 31 0.18 0.01 0.12 0.01 0.07 0.00 0.05 0.01 30 0.19 0.01 0.11 0.00 0.07 0.00 0.04 0.01 32 0.19 0.01 0.12 0.00 0.07 0.01 0.04 0.00 33 0.19 0.00 0.12 0.00 0.08 0.00 0.05 0.01 19 0.24 0.01 0.12 0.00 0.11 0.01 0.06 0.01 20 0.22 0.01 0.10 0.00 0.11 0.01 0.06 0.02 21 0.26 0.01 0.11 0.01 0.11 0.02 0.05 0.01 25 0.23 0.01 0.11 0.00 0.10 0.00 0.05 0.01 23 0.22 0.01 0.11 0.01 0.08 0.01 0.05 0.01 24 0.24 0.01 0.13 0.01 0.10 0.01 0.05 0.01 29 0.24 0.01 0.11 0.01 0.10 0.01 0.05 0.01 28 0.19 0.01 0.09 0.01 0.12 0.02 0.06 0.01 27 0.23 0.01 0.10 0.01 0.11 0.01 0.05 0.00 36 0.20 0.02 0.09 0.01 0.07 0.02 0.05 0.01 38 0.22 0.01 0.11 0.01 0.09 0.00 0.05 0.01 34 0.22 0.01 0.11 0.01 0.10 0.01 0.06 0.01 Non 0.19 0.00 0.08 0.01 0.06 0.01 0.02 0.01

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 172

Flexural Modulus (GPa) Uncalendered Samples Ctg 50% RH & 73°F 81% RH & 100°F ID MD CD MD CD Avg. STD Avg. STD Avg. STD Avg. STD 3 3.64 0.11 1.82 0.02 1.43 0.29 0.76 0.13 6 3.79 0.22 1.70 0.10 1.46 0.29 0.57 0.08 7 3.77 0.07 1.93 0.08 1.53 0.20 0.61 0.03 5 3.73 0.19 1.61 0.13 1.42 0.13 1.60 0.15 13 3.82 0.13 1.98 0.08 1.69 0.26 0.94 0.09 9 3.98 0.21 1.95 0.03 1.55 0.19 0.77 0.10 12 4.12 0.24 2.02 0.09 1.63 0.31 0.78 0.13 10 3.98 0.07 1.91 0.05 1.39 0.17 0.68 0.06 15 3.67 0.03 1.78 0.07 1.28 0.08 0.49 0.03 14 3.61 0.06 1.80 0.09 1.46 0.18 0.72 0.06 18 3.59 0.04 1.69 0.05 1.23 0.27 0.52 0.11 17 3.56 0.22 1.75 0.05 1.12 0.17 0.56 0.10 31 4.05 0.10 1.89 0.06 1.31 0.23 0.64 0.07 30 3.89 0.16 1.85 0.06 1.34 0.16 0.67 0.10 32 3.72 0.10 1.91 0.07 1.28 0.19 0.65 0.03 33 3.62 0.14 1.80 0.02 1.19 0.12 0.61 0.13 19 4.90 0.24 2.27 0.06 2.10 0.25 0.88 0.20 20 4.99 0.29 2.26 0.09 1.87 0.43 0.96 0.11 21 5.19 0.19 2.08 0.09 2.02 0.27 0.91 0.10 25 5.18 0.24 2.32 0.15 2.06 0.30 0.94 0.19 23 4.94 0.33 2.10 0.18 1.64 0.29 0.98 0.17 24 4.54 0.11 2.08 0.04 1.40 0.34 0.57 0.11 29 4.93 0.11 2.05 0.07 1.53 0.42 0.86 0.28 28 4.49 0.16 1.97 0.10 2.61 0.33 1.23 0.10 27 4.45 0.18 1.94 0.07 2.58 0.26 1.23 0.01 36 4.81 0.26 2.04 0.11 2.29 0.41 1.18 0.18 38 4.87 0.20 2.12 0.05 1.40 0.19 0.80 0.25 34 4.70 0.21 2.14 0.14 1.28 0.30 1.10 0.14 Pre 4.00 0.16 1.99 0.06 1.23 0.06 0.49 0.10 No 5.36 0.09 2.25 0.24 1.73 0.06 0.72 0.07

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 173

Flexural Modulus (GPa) Calendered Samples 50% RH & 73°F 81% RH & 100°F CtgID MD CD MD CD Avg. STD Avg. STD Avg. STD Avg. STD 3 4.30 0.23 2.46 0.06 1.80 0.18 0.97 0.22 6 3.78 0.09 2.15 0.14 1.49 0.18 1.05 0.11 7 3.89 0.15 2.45 0.12 0.99 0.15 1.51 0.24 5 3.61 0.17 2.26 0.07 1.35 0.14 0.95 0.17 13 4.29 0.17 2.28 0.14 1.74 0.15 0.91 0.08 9 4.08 0.12 2.31 0.16 1.73 0.21 0.93 0.10 12 3.17 0.08 2.16 0.10 1.71 0.23 1.02 0.20 10 3.56 0.24 2.37 0.25 1.49 0.12 0.86 0.12 15 3.44 0.38 2.17 0.07 1.61 0.20 0.97 0.08 14 4.07 0.22 2.26 0.16 1.55 0.14 0.97 0.09 18 3.85 0.13 2.33 0.03 1.64 0.16 0.96 0.17 17 3.64 0.19 2.24 0.17 1.60 0.14 0.99 0.13 31 4.04 0.27 2.61 0.20 1.70 0.09 1.07 0.18 30 4.05 0.24 2.41 0.08 1.52 0.08 0.82 0.14 32 4.06 0.19 2.60 0.09 1.62 0.14 0.98 0.06 33 4.13 0.11 2.55 0.06 1.67 0.08 1.13 0.16 19 4.86 0.29 2.41 0.04 2.23 0.29 1.20 0.22 20 4.72 0.28 2.10 0.09 2.40 0.28 1.33 0.46 21 5.71 0.29 2.40 0.25 2.36 0.35 1.16 0.13 25 5.29 0.26 2.55 0.11 2.20 0.10 1.04 0.21 23 4.87 0.23 2.39 0.12 1.73 0.13 1.02 0.17 24 5.06 0.29 2.66 0.18 2.00 0.28 1.12 0.17 29 5.25 0.29 2.41 0.22 2.22 0.25 1.03 0.14 28 4.13 0.15 1.98 0.21 2.64 0.44 1.23 0.29 27 4.93 0.23 2.11 0.22 2.23 0.25 0.97 0.08 36 4.52 0.42 2.07 0.17 1.66 0.39 1.10 0.21 38 5.08 0.14 2.48 0.13 2.13 0.06 1.20 0.16 34 4.90 0.24 2.36 0.11 2.16 0.27 1.29 0.20 No 4.48 0.10 2.00 0.20 1.54 0.20 0.47 0.14

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 174 Appendix C

Statistical Analysis of 3-Point Bending Load Results

Main Effects Plot (fitted means) for Load (N)

Coating Calender

2 .0 -

1.5-

Astra Control XP6117 XP8000 Cal Uncal 'S CMD RH § I 2.0-

1.5-

1.0 -

CD MD 50% 81%

Interaction Plot (data means) for Load (N)

Cal Uncal 50% 3 Coating — A stra 2 — Control — XR6117 - 1 ■ * XP6000

Calender Cal 2 - Uncal 1- 3 CMD CD 2 MD CMD - 1

RH 50% 2 - 81% RH 1-

Astra Control XP6117 XP8000 CD MD

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 175 • Design points above predicted value o

X1 = C: Coat Wt X2 = A: Coating Actual Factors B: Base = Non D: SurfaceFinish=0 295 E CMD = MD F: RH = 50% 20E

1.15

Cbrtrd

XP6117 A: Coating XP9000 C: Coat Wt

Design points above predicted value

X1 = C: Coat Wt ass X2 = A: Coating Actual Factors B: Base = Non D: Surface Finish=0 E CMD = MD F: RH = 81 % 2.0S ■D CO

1.15

A: Coating C: Coat Wt XFBOCD

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Design points above predicted value

X1 = C: Coat Wt X2 = A: Coating Actual Factors B: Base = Non D: SurfaceFinish=0 2 9 5 E CMD = CD F: RH = 50% z 20S S 3

Cortrd

XF61T7 A: Coating C: Coat Wt

• Design points above predicted value o

X1 = C: Coat Wt 3 X2 = A: Coating Actual Factors B: Base = Non D: SurfaceFinish=0 : E CMD = CD F: RH = 81 % 2 0 5 "S

1.15

CDftrd

XP6117 A: Coating C: Coat Wt

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Design points above predicted value

X1 = C: Coat Wt X2 = A: Coating Actual Factors B: B ase = Non D: SurfaceFinish=1600 E CMD = MD F: RH = 50% 2 0 5

TJ (0

C o r tr d

XP6117 A: Coating XRBOGD C: Coat Wt

Design points above predicted value

X1 = C: Coat Wt X2 = A: Coating Actual Factors B: Base = Non D: Surface Finish=1600 2 9 5 E CMD = MD F: RH = 81 %

205

S 3

Oortrd

XR6117 A: Coating XP80CD C: Coat Wt

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Design points above predicted value

X2 = A: Coating Actual Factors B: Base = Non D: Surface Finish=1600 295 E CMD = CD F: RH = 50%

2.05

0.2 5 ^ C b rtrd

XP6117 A: Coating XPBOOO

Design points above predicted value

X1 = C: Coat Wt X2 = A: Coating Actual Factors B: Base = Non D: SurfaceFinish=1600 E CMD = CD F: RH = 81 %

C O rtid

XF6117 A: Coating C: Coat Wt

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. C: C: Coat Wt C: C: Coat Wt XF80G0 XP6117 XPB117 A: A: Coating Otxtid A: A: Coating Cortrd 1.16 1.15 as7 2 0 5 1c

Design points above predicted value B: B: Base = Pre SurfaceFinish=0D: E = CMD MD = 50%RH F: Actual Factors X1 X1 = C: Coat Wt X2 = A: Coating D: SurfaceD: Finish = 0 E = MD CMD % = 81 F: RH B: B: Base = Pre Actual Factors • • o X1 = C: Coat Wt X2 =A: Coating • Design o points above predicted value Reproduced with permission ofthe copyright owner. Further reproduction prohibited without permission. 180 Design points above predicted value

X1 = C: Coat Wt ass X2 = A: Coating

Actual Factors B: Base = fte D: SurfaceFinish=0 E CMD = CD F: RH = 50%

1.15

ucxtrd

XP61T7 A: Coating C: Coat Wt

• Design points above predicted value

X2 = A: Coating Actual Factors B: Base = Pre D: SurfaceFinish=0 E CMD = CD F: RH = 81 % 2.05

0 2 5 ^ Q ortrd

XP6117

A: Coating XFB000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. C: Coat Wt C: Coat Wt XFB117 XP61T7 A: Coating Cortna A: Coating COitrd 1.15 1.15 20E a 85 a 2 9 5

OS 3

Design points above predicted value Design points above predicted value F: RH =% 81 RH F: E = MD CMD D: SurfaceFinish=1600D: B: B: B ase = FVe Actual Factors B: B: B ase = FTe D: SurfaceFinish=1600D: = 50% F: RH E = MD CMD Actual Factors X2 = A: Coating X1 X1 = C: Coat Wt X1 X1 = C: Coat Wt X2 = A: Coating • o Reproduced with permission ofthe copyright owner. Further reproduction prohibited without permission. • Design points above predicted value

X1 = C: Coat Wt X2 = A: Coating Actual Factors B: Base = Pre D: SurfaceFinish=1600 a95 E CMD = CD F: FtH = 50%

XR6117

A: Coating XPBOQD

• Design points above predicted value

X2 = A: Coating Actual Factors B: Base = Pre 2gs D: SurfaceFinish=1600 E CMD = CD F: RH = 81 % „ S - 2 0 5

0.25 Cortrd

XP6117 A: Coating

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 183

X1 = A: Coating X2 = B: Base a 9l Actual Factors C: Coat Wt = 10.00 D: Surface Finish = 0 a o 1 E: CMD = MD F: RH = 50

T* 3

CDrtrd

XRB117 A: Coating B: Base Nbn XPBOOO

X1 = A: Coating X2 = B: B ase Actual Factors C: Coat Wt = 10.00 D: Surface Finish = 0 E CMD = MD F: PH = 81

CDrtrd

X F 6 1 1 7 B: Base A: Coating

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 184

X1 = A: Coating X2 = B: Base Actual Factors C: Coat Wt = 10.00 D: Surface Finish=0 E CMD = CD F: RH = 50

COftroJ

XRB117 B: Base Nbn XP8000 A: Coating

X1 = A: Coating X2 = B: Base Actual Factors C: Coat Wt = 10.00 D: Surface Finish = 0 E CMD = CD F: FIH = 81

Q x trd

X P B 117 B: Base A: Coating

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 185

X1 = A: Coating X2 = B: Base Actual Factors C: Coat Wt = 10.00 D: Surface Finish=1600 E CMD = MD F: FtH = 50

C D rtrd

XF6117

B: Base Non XPBOOO A: Coating

X1 = A: Coating X2 = B: Base Actual Factors C: Coat Wt = 10.00 D: Surface Enish=1600 E CMD = MD F: FiH = 81

as 3

C o rtrd

X P 8 1 1 7 B: Base A: Coating

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 186

X1 = A: Coating X2 = B: Base Actual Factors C: Coat Wt = 10.00 D: Surface Finish=1600 E CMD = CD F: FIH = 50

"O <8

XFB117

B: Base NXl " O ' " XP0OOO A: Coating

X1 = A: Coating X2 = B: Base Actual Factors C: Coat Wt = 10.00 D: Surface Finish=1600 E CMD = CD F: FIH = 81

CDrtrd

XPB117 B: Base A: Coating

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER VIE

A SIMPLE METHOD FOR CALCULATION OF THE PERMEABILITY COEFFICIENT OF POROUS MEDIA

Lokendra Pal, Margaret K. Joyce, and Paul D. Fleming Center for Coating Development Department of Paper Engineering, Chemical Engineering and Imaging, Western Michigan University, Kalamazoo, MI, USA TAPPI Journal, Vol. 5: No. 9, September 2006

Abstract

The fluid storage capacity of porous media, such as paper and paperboard, is

mainly determined by its porosity, whereas the absorption and spreading rate is

determined by the permeability. A simple method for calculation of the permeability

coefficient of porous media is described. The permeability coefficient may be

calculated by Darcy’s equation [1] using the Parker Print Surf porosity (which is

primarily sensitive to air permeability) [2-5]. The permeability coefficient may be

used for ranking porous media in fluid absorption and spreading rate and for

estimation of pore size. Likewise, the coating thickness required for given barrier and

printing performance may be estimated.

Application Statement: The permeability coefficient can be used as a

quantitative tool to predict the barrier performance of porous media.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 188 Introduction

Porous media, such as paper and paperboard, contain small open spaces, voids

and pores, distributed throughout solid matrices [6]. Adsorption and absorption of

liquids through these pores have repercussions with respect to the barrier properties

and to the ultimate strength of the sheet [7-9]. Moreover, the pores have an effect on

the interaction between printing inks and paper [10-12].

Paper is laminated, surface sized, or extruded with a variety of film formers

and plastics to lower its permeability to moisture, water vapor, water and other

solvents and paper is internally sized to prevent excessive spreading of inks [13-15].

In addition, in many converting operations, where liquids are forced into the sheet by

the action of a nip, the porous structure of the base sheet is important. Thus, the

characterization of the porous property, i.e. permeability, is of major importance for

predicting the barrier and printing properties of paper products.

Difference Between Permeability and Porosity

Permeability is the most important physical property of a porous medium,

while the porosity is its most important geometrical property. The permeability

describes the conductivity of a porous medium with respect to fluid flow, whereas

porosity is a measure of the fluid storage capacity of a porous material. Permeability

describes how easily a fluid is able to move through the porous material. Thus, it is

related to the connectedness of the void spaces and to the pore size of the paper. It is

calculated using a formula widely known as Darcy’s Law [1].

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. For quality control, units of measurement may be irrelevant, but for scientific

research it is essential to be able to express results in absolute units [3]. Permeability

measurements expressed in units of air flow or time cannot be compared directly with

pore dimensions. For this reason, there is a need for calculating permeability results in

appropriate units, which is area or square of length. As such, it can be interpreted in

terms of an effective capillary cross sectional area or diameter [16].

Darcy’s Law

Current equations describing fluid transport in porous media are based on

semi-empirical equations derived in the 19th century by Darcy [1] for single- phase

flow and in the 20th century for multi-phase flow. These equations describe the

average behavior of a mixture of a porous medium and one or more fluids. Darcy’s

law describes the kinetics of fluid flow through porous media in terms of the driving

force and the permeability of the medium.

K A P Darcy’s Law Q = ------(VIII. 1) T) A L

where:

Q = flow rate (m3/s) K = permeability coefficient, (m2) AP = pressure drop or difference, (Pa) L = flow length or thickness of test sample, (m) A = area of cross-sectional area to flow, (m2) T| = fluid viscosity, (Pa-s)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The permeability coefficient K depends on the combination of the fluid and

porous material used. The greater the value of K, the higher will be the rate of flow of

a fluid through a material. While Darcy's equation was formulated from experimental

data over a century ago, it was only recently proved theoretically. Mokadam [17]

showed that Darcy’s equation is a special case of a general equation that he derived

for flow through porous media using irreversible thermodynamics. Therefore, Darcy’s

equation is a theoretically and experimentally valid law in the laminar flow for all

porous media. The applicability of Darcy’s law was also confirmed experimentally to

porous media such as paper [18-21].

Ridgeway, et al. [11] used Darcy’s equation to compare the liquid

permeability coefficient with the Bendtsen air permeability coefficient. Their results

showed close agreement with a few exceptions. Generally, we expect the liquid and

gas permeabilities of a given medium to be different, but of the same order of

magnitude. The gas permeability should be close to the liquid permeability of a

perfectly wetting liquid. Differences in permeability for different wetting conditions

are suggested by the Lucas-Washburn equation [22,23].

In this paper, Parker Print Surf (PPS) porosity measurement values (ml/min)

are used to calculate the permeability coefficient of various papers, in order to predict

the barrier resistance to gasses.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Experimental Design

This work is divided into two phases: (1) to develop a method for calculation

of a permeability coefficient, and (2) to study the effect of pigment type, coating

application methods, coating pickups and coat weight on measured permeability

coefficients.

Materials

An acrylic polymer emulsion Lipacryl-MB3640 was used for size press and

blade coatings. The viscosity, average particle size, solid content and pH of the

emulsion, according to manufacturer, are given in Table 8.1. Lipacryl-MB3640 has

been used by other researchers [9]. A low molecular weight ethylated starch was also

used for size press and impregnator coatings. The characteristics of nanoclay and

kaolin clays according to manufacturer are given in Table 8.2. Nanoclay was used for

size press and impregnator treatment [24,25]. Three different aspect ratio clays were

used for size press and blade coating. Two commercial papers; unbleached kraft paper

and SBS baseboard were used as the substrate for the dispersion coating.

The base substrates characteristics are given in Table 8.3. The unbleached

kraft paper was size press and impregnator treated [24,25]. The bleached kraft board

was size press treated and blade coated. The Impregnator coater and size press

pickups and application conditions are given in Table 8.4.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 192 Table 8.1. The Characteristics of the Binder

Solids Avg. Particle Size, Binder pH Viscosity, cps content, % pm

MB-3640 54.5 - 55.5 6.5 - 7.5 400, max 250 - 325

Table 8.2. The Characteristics of the Mineral Pigments

Avg. Particle Size, BET Surface Mineral Pigments Aspect Ratio pm Area, m /g

Nanoclay 200-400 0.12-0.14

Kaolin clay # A 10-20 0.15-0.20 20-22

Kaolin clay # B 25-35 0.45-0.55 16-18

Kaolin clay # C 50-60 0.45-0.55 18-20

Table 8.3. The Characteristics of the Base Substrates

Grammage, Internal PPS Porosity, Substrates g/m2 Sizing ml/min

Unbleached kraft base 70 None 2136 paper

Solid Bleached Sulfate 266 None 284 (SBS) baseboard

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 193 Table 8.4. Impregnator Coater and Size Press Pickups and Application Conditions

Impregnator Coater Size Press Pigment Loading Shoe Pond Pressure Pickup Solids Pickup (%) Pressure (PSD (%) (%) (%) (PSD 0 5 40 10.4 22 14.1 0 10 40 13.5 14 9.5 0 15 40 14.3 6 5.6 3 5 40 7.8 22 14.6 3 10 40 10.0 14 10.3 3 15 40 12.2 6 5.9 3 20 40 14.0 9 5 40 6.3 22 14.3 9 10 40 8.0 14 9.2 9 15 40 11.1 6 6.4 9 20 40 12.9 9 25 40 15.5

Testing

A Messmer Instrument PPS Model 90 was employed to measure Parker Print

Surf (PPS) porosity [2-5]. TAPPI Standard Method T-555 was used to measure PPS

porosity. The PPS Porosity was calculated as the mean of 10 readings at different

locations.

Procedure

Cellulose nitrate model papers of different pore sizes were used for test

development. The physical properties of the cellulose nitrate papers are shown in

Table 8.4. The papers were conditioned and then tested for PPS porosity and caliper.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 194 The PPS porosity was measured at a 1000 kPa clamping pressure. The standard

parameters for the PPS tester used were as follows:

Fluid (air) viscosity (r\): 1.80075E-05 Pa.s (Ns/m2) at 23°C Standard pressure drop (AP): 6.17 kPa [26,27] Area of cross-section (A): 10 cm2 [26]

By incorporating the standard pressure drop (AP), fluid viscosity (r|) and

cross-section area (A) values into equation (1), the following relationship was

obtained:

Permeability Coefficient, K (pm2) = 0.048838*Q (ml/min)* L (m) (VIII.2)

An example calculation of the permeability coefficient for 0.20 pm pore size

model paper using equation (2) follows:

Parker Print Surf flow rate (Q) at 1000 kPa: 477 ml/min Thickness of 0.20 pm model paper (L): 124 pm Permeability coefficient, K = 0.00289 pm2

Additional examples for cellulose nitrate papers are shown in Table 8.5. Note

that the permeability coefficients reach an asymptotic value as a function of the

thickness of the paper sample, while the PPS porosity values are inversely

proportional to thickness. As a result, the PPS porosity will continuously decrease,

where as the permeability coefficient will reach an asymptotic value as a function of

the thickness of the sample. This property is evident from Figure 8.1.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 195 Table 8.5. Permeability Coefficients of Model Papers

Avg. PPS Porosity Permeability Coefficient Avg. Pore (ml/min) (pm2) Sample I.D. Thickness Size (pm) (pm) Avg. Std. Avg. Std.

124 477 5.05 0.00289 0.0000310 Cellulose Nitrate-Low 0.20 270 245 3.21 0.00323 0.0000429 Porosity 381 164 2.33 0.00304 0.0000439

124 787 7.59 0.00476 0.0000466 Cellulose Nitrate- 0.45 270 403 6.89 0.00531 0.0000921 Medium Porosity 381 273 3.68 0.00508 0.0000694

98 2614 18.40 0.01251 0.0000892 Cellulose Nitrate- 0.80 229 1382 12.25 0.01546 High 0.0001388 Porosity 321 932 9.74 0.01461 0.0001547

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 196

a PPS Porosity Permeability Coefficient 3000 0.018 0.80 |im 0.016 * f t 2500 0.45 |im 0.014 n ET w g 2000 0.012 so O 0.20 urn ■ 1 0.010 IS Ont $ iooo 0.006 tD & 0.004 O- 500

- 0.002

-H 0.000 124 270 381 124 270 381 98 229 321

Model Paper Thicknes s (|im)

Figure 8.1. Comparison of Permeability Coefficients and PPS Porosities of Model Papers

Coatings for SBS Paperboard

Six different coatings were prepared with pigments of different aspect ratios

and binders. The coatings varied in the amount of dry pigment added on dry weight of

binder. The amount and aspect ratio of pigment was varied to determine the influence

on the porosity and permeability coefficient of the paperboard in comparison to a

conventional pigmented coating. The pre-dispersed clays at 62 % solids and a

synthetic binder at 54 % solid were used for all coatings. The pigment was blended

into the appropriate amount of binder to yield the desired coating suspension. The

coating solids and viscosity were measured.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. All size press coatings were applied at 30% solids and room temperature. The

viscosities of the coatings were all below 150 mPas. All blade coatings were applied

at 58% solids and room temperature. The viscosities of the coatings were all below

400 mPas. The coatings were applied to a 266 g/m2 SBS baseboard using a laboratory

size press and cylindrical laboratory coater. The porosity and permeability coefficient

of the samples were measured. The influence of pigment aspect ratio on permeability

coefficient was studied.

Coatings for Unbleached Kraft Paper

Three different coatings were prepared with a low molecular weight ethylated

starch. The coatings varied in the amount of dry pigment added on dry weight of

starch (0, 3, 9%). The clay was added to determine its influence on the porosity and

permeability coefficient of the paper in comparison to starch alone. The clay was pre

dispersed at 15% solids using a high shear Cowles disperser. An anionic dispersant

was added at a rate of 1% on weight of pigment (dry/dry). The viscosity of the

pigment dispersion was 99 mPas (Brookfield #3 spindle, 60 rpm, 38°C).

The elevated temperature of the clay was the result of the high shear energy

used to disperse the pigment. The starch was jet cooked at 24% solids and the

viscosity measured at 27 °C. The viscosity of the starch was 55 mPas @ 60 rpm. The

pigment was then blended into the appropriate amount of starch solution to yield the

desired sizing solution. The solids in the coatings were measured using a Labwave

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. solids analyzer and the Brookfield viscosities were measured at 60 rpm with an LVT

digital viscometer.

All coatings were applied at approximately 20% solids at 32°C. The

viscosities of the coatings were all below 100 mPas. The coatings were also applied to

an unsized, 70 g/m2 unbleached Kraft basepaper using an impregnator coater [23,24].

Because the pickup on the impregnator could be controlled by increasing the reservoir

pressure, the coating solids did not have to be adjusted and remained at 20% for all

runs.

Adjusting the reservoir pressure also enabled the depth of penetration to be

controlled [23,24]. At the higher pigment loadings, more pressure was needed to

drive the coating into the sheet. The reservoir pressures were gradually increased

until evidence of the coating passing through to the backside of the sheet was seen.

Evidence of coating penetration completely through the sheet was confirmed by the

change in color of the backside of the sheet after drying. To control the pickup at the

size press, the solids of the coatings were adjusted down by adding dilution water.

The pickups obtained for each coating application are shown in Table 8.5. The pickup

at the size press increased linearly with coating solids for all pigment levels. The

influence of impregnator reservoir pressure on pickup is also shown in Table 8.5 and

Figure 8.2. For all levels of pigment applied, the pickup increased with increasing

reservoir pressure. As the level of pigment increased, more pressure was needed to

push the coating into and through the base-sheet, indicating a packing influence from

the pigments.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 199

♦ 0% Pigment Loading ■ 3% Pigment Loading A 9% Pigment Loading 18 16 14 o.3 12 Mo ffi 10 c00 rt 8 o U 6 4

2 0 10 15 20 25 30 Pond Pressure, psi

Figure 8.2. Influence of Impregnator Pond Pressure on Coating Pickups

Results and Discussion

Results for SBS

The PPS porosity and permeability coefficient values are given in Table 8.6

for the different pigments and coating conditions. The permeability coefficient was

calculated from PPS porosity results, as described above. The dependence of PPS

porosity and permeability on aspect ratio of the pigments is shown in Table 8.6 and

Figure 8.3. Size press treated samples gave lower PPS porosity and permeability than

the blade coated samples for the medium aspect ratio pigments.

The low and high aspect ratio showed little, if any, dependence on application

method, probably because both methods are in the low shear regime for the low

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 200 aspect ratio pigments and both are in the high shear regime for the high aspect ratio

pigments. Thus, there was no apparent dependence on the different shear rates for the

two methods. The high aspect ratio pigment produced the lowest PPS porosity and

permeability for the blade coated samples, but not significantly, since that case also

had the highest coat weight. PPS porosity and permeability values showed a

difference between the two application methods at all pigment-loading levels.

The aspect ratio of the pigments was found to have a more pronounced effect

on the permeability of the size press coated samples then the blade coated samples.

The low permeability of the size press coated samples resulted in a greater resistance

to moisture vapor transmission under high humidity and temperature conditions.

These results will be presented in a future publication. At this time, we have

accounted for total thickness, however work to account for the contribution of coating

thickness to the effective permeability of the coated paper are in progress.

Table 8.6. Influence of Pigments Aspect Ratio on PPS Porosity and Permeability Coefficient

Avg. PPS Porosity Permeability Pigment Formulation Coating Coat Wt. (ml/min) Coefficient (pm2) s (wt%) Method (g/m2) Avg. Stdev. Avg. Stdev.

# A 50% 8.7 13.7 1.53 2.03E-04 2.26E-05 Size # B Pigment + 8.3 8.8 0.84 1.25E-04 1.20E-05 Press 50 % Binder #C 8.2 10.0 1.18 1.45E-04 1.71E-05

# A 91% 9.3 11.3 1.18 1.64E-04 1.71E-05 CLC- # B Pigment + 8.5 12.1 0.95 1.72E-04 1.35E-05 Blade 9.0% Binder #C 10.2 10.5 1.35 1.52E-04 1.95E-05

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 201

I Blade Coating I Size Press I Blade Coating I Size Press 16 3.E-04

14 3; 2.E-04 •S' 12 S c I 10 S 2.E-04 O0> t 8 U £ 6 js l.& 0 4 00 C3 & 4 D 5.E-05 O h

0.E+00 10-20 25-35 50-60 10-20 25-35 50-60 Aspect Ratio Aspect Ratio

Figure 8.3. Influence of Pigments Aspect Ratio on PPS Porosity and Permeability Coefficient

Results for Unbleached Kraft

The PPS porosity and permeability coefficient values are given in Table 8.7

for different conditions (Base Paper- PPS Porosity = 2136 ml/min, Permeability =

0.01476 pm2). Figure 8.4 shows the influence of pigment loading (14 % pickup, dry

basis) on sheet porosity and permeability. Impregnator treated samples gave lower

porosity and permeability than size press. The significantly lower porosities of the

impregnated treated samples indicate that this method is better for reducing the

permeability of the papers or closing off the sheet. PPS porosity and permeability

values showed a significant difference between the two application methods at all

pigment-loading levels. The addition of nanoclay significantly reduced the porosity of

both the impregnated and size press treated papers.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 202 Table 8.7. Influence of Saturation Treatment on PPS Porosity and Permeability Coefficient of Different Samples

Impregnator Coater Size Press Permeability Permeability PPS Porosity PPS Porosity Coefficient Coefficient (ml/min) (ml/min) (%) (pm2) (%) (pm2) Pickup Pickup Pigment Pigment (%) Avg. Std Avg. Std Avg. Std Avg. Std 0 10.4 547.5 148.7 0.0040 0.0011 5.6 1446.6 151.3 0.0093 0.0010 0 13.5 485.6 56.4 0.0037 0.0004 9.5 1322.1 141.4 0.0088 0.0009 0 14.3 447.2 45.7 0.0035 0.0004 14.1 1270.9 168.4 0.0085 0.0011 3 7.8 468.4 56.2 0.0035 0.0004 5.9 1445.8 189.5 0.0097 0.0013 3 10.0 390.0 58.8 0.0029 0.0004 10.3 1193.3 146.7 0.0081 0.0010 3 12.2 320.7 32.1 0.0024 0.0002 14.6 1031.9 133.8 0.0070 0.0009 3 14.0 287.7 39.4 0.0023 0.0003 9 6.3 384.0 29.8 0.0028 0.0002 6.4 1249.6 130.2 0.0081 0.0008 9 8.0 239.8 37.5 0.0017 0.0003 9.2 1020.6 109.7 0.0068 0.0007 9 11.1 177.5 29.9 0.0013 0.0002 14.3 856.4 74.9 0.0057 0.0005 9 12.9 131.2 10.5 0.0010 0.0001

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 203

Impregnator ■ Size Press Impregnator ■ Size Press 1600 0.012

S 0.010 S 1200

• t 8 0 0 § 0.006 u o 600 O h .* 0.004 2 400 O h

Figure 8.4. Influence of Pigment Loading (14% Pickup (dry/dry)) on PPS Porosity and Permeability Coefficient of Size Press and Impregnator Treated Papers

Conclusions

A simple method for calculating the permeability coefficient of gasses through

porous media has been developed. The proposed permeability formula, based on

Darcy’s law, shows promise as a quantitative tool to predict the barrier performance

of porous media. Its application to porous media has been demonstrated, using

different grades of coated and uncoated paper across a wide range of PPS porosities.

The permeability coefficient, as calculated here, will reach an asymptotic value as a

function of thickness of the sample, whereas the PPS porosity will continuously

decrease.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 204 For a uniform medium, the asymptotic permeability will be observed at very

small thicknesses and corresponds to the permeability of the uniform medium. The

asymptotic permeability for a laminated porous medium (e.g. coated paper) will be

determined by the permeability of the flow rate controlling layer, (e.g. the coating).

Use of this calculational tool provides more useful information to the papermaker,

because it provides insight into the contribution of thickness and interconnectivity of

the pores of the samples in comparison to air flow measurements. It was found that

the coating application method had a significant effect on the permeability coefficient.

The permeability varied with coating pickup, pigment loading, and depth of

penetration.

References

1. Darcy, H., “Les Fontaines Publiques de la Ville de Dijon ”, Dalmont, Paris, (1856).

2. Parker, J. R., Paper Technology, 6 (2): T32 - T36 (1965).

3. Parker, J. R„ TAPPI, 54 (6): 943 - 949 (1971).

4. Parker, J. R., Paper Technology, 12 (3): T109 -T 1 13(1971).

5. Parker, J.R., Printing Technology, 18 (3): 7-11 (1974).

6. Dullien, F. et al., “ Porous Media, Fluid Transport and Pore Structure, Academic Press Inc.”, Second Edition, San Diego, 1992.

7. Kjellgren, H., and Engstrom, G., “The Relationship Between Energy Requirement and Barrier Properties in the Production of Greaseproof Paper”, TAPPI J., 4 (8): 7 - 11 (2005)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8. Nilsson, L., Wilhelmsson, B., and Strenstrom, S., “ Drying Technology ”, 11 (6): 1205 (1993)

9. Vaha-Nissi, M., Savolainen, A., Talja, M., and Moro, R., “ Dispersion Barrier Coating of High Density Base Papers”, 1998 TAPPI Coating Conference Proceedings.

10. Engstrom, G., Morin V., and Bin, S. L., “ Analysis of porosity distribution in coating layers ,” Tappi J. 80 (5): 203 - 209 (1997).

11. Ridgway, C.J., Schoelkopf, J., and Gane, P.A.C., “A New Method for Measuring the Liquid Permeability of Coated and Uncoated Papers and Boards”, Nordic Pulp Paper Res. J. 18 (4): 377 - 381(2003)

12. Gane, P.A.C., Schoelkopf, J., Spielmann, D.C., Matthews, G.P., and Ridgway, C.J., “Fluid Transport into Porous Coating Structures: Some Novel Findings”, Tappi J. 83 (5): 77 - 78 (2000)

13. Klass, C., GATFWorld, 8 (1): 15 - 17 (1996).

14. Abell, Steve, “Starch-Based Binders Offer Easy Pigment Application at Size Press”, Pulp and Paper, 69(5): 99 - 100,103 - 105 (1995).

15. Klass, C., “Surface Sizing Part II, Size Press Technology”, 1997 TAPPI Sizing Short Course, Nashville, TN, p. 31.

16. Katz, A. J., and Thompson, A. H., “Quantitative Prediction of Permeability in Porous Media", Phys. Rev. 34 8179 (1986).

17. Mokadam, R. G., J. Appl. Mech. 28:208 - 12 (1961).

18. Carson, F. T., J. Res. Natl. Bur. Standards 12:587 - 608 (1934).

19. Bublitz, W. J., Jr. “A Study of the Air Permeability of Paper at High Pressures”, Master's thesis, Appleton, Wis., The Institute of Paper Chemistry, 1947. 89 p.

20. Coupe, R. R., "Proc. Tech. Sect. British Paper & Board Makers", Assoc. 31, no. 2:383-457(1950).

21.Bliesner, W.C., "A Study of the Porous Structure of Fibrous Sheets Using Permeability Techniques", Doctor's Dissertation, Appleton, Wis., The Institute of Paper Chemistry, June 1963. p 10.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 206 22. Lucas R., “Uber das Zeitgesetz des Kapillaren Aufstiegs von Flussigkeiten”, Kolloid - Z., 23:15(1918).

23. Washburn E. W., “The Dynamics o f Capillary Flow ”, Phys. Rev., 17: 273 (1921).

24. M. Joyce and T. Joyce, “Practicalities of Using Impregnation (Controlled Penetration Sizing Method) for Improving the Barrier and Strength Properties of Linerboard”, Invited Speaker, Internal and Surface Sizing PIRA Conference, Graz, Austria, 2003.

25. M. Joyce and T. Joyce, “Nanoparticle Barrier-Coated Substrate and Method for Making the Same”, US Patent 6,942,897 Sept. 13, 2005.

26. Peel, D. P., “Paper Science and Paper Manufacture”, 1999 Vancouver: Angus Wilde Publication.

27. Operating and Maintenance Instructions for the Parker Print-Surf Roughness and Porosity Tester, H. E. Messmer Ltd., Britain

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 207 CHAPTER IX

CONCLUSIONS

Phase I: The pigment shape facto appears to have a systematic effect on barrier

properties although it is relatively small in some cases. The shape factor significantly

impacted the saturation coat weight (where complete coverage occurs). The medium

shape factor pigment (SF -50-60) provided the highest barrier properties for the 14 pt

SBS board tested, but the results might be different for boards of different roughness

and porosity. The 100 % acrylic based hydrophobic binder gave better barrier

properties compared to styrene butadiene based binder.

The double-coated treatment method (size press/rod) produced the best results.

The effect of application method on barrier properties was found to have a more

significant impact on the barrier properties than the SF of the pigment. As expected,

Taber stiffness decreases with increase in relative humidity. However, there was only

a slight impact of pigment shape factor and application method on stiffness.

Phase II & IH: New recyclable and sustainable co-polymerized coatings were

developed for barrier applications. Acrylic co-monomers were polymerized with

addition of three different, finely dispersed modified high shape factor engineered

(HSFE) clays, to create co-polymerized coatings. The wet and dry coating properties

were studied and showed promising results in-terms of runnability and dispersion

stability. The CLC coated samples were then tested for gas and water vapor

permeability. Additionally, the optical and surface properties were determined.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 208 The effects of pigment shape, baseboard, coat weight, calendering and relative

humidity and temperature on barrier properties were studied through full factorial

design of experiment (DOE). From ANOVA results and main effects plot, all of the

studied factors showed a significant impact on barrier properties. The high shape

factor and thinner platelet pigment, XP8000 (SF~ 50-60, T- 40 nm) gave the lowest

WVTR for non pre-coated baseboard. While the XP8000 and Astra (SF-25-32, T-70

nm) gave lowest WVTR for pre-coated baseboard. Calendering slightly improved the

barrier properties. Relative humidity and temperature had a detrimental effect on

barrier properties. Although the high shape factor improved coverage, the results were

comparable for the XP8000 and Astra.

The surface and optical properties showed promising results. The high shape

factor provided higher surface smoothness and gloss, with a slight impact on

brightness. Calendering has a significant impact on surface and optical properties. The

co-polymerized coatings provided very high gloss results.

The flexural stiffness and modulus of SBS paperboard, coated with these

coatings was determined from bending load and deflection measurements using three

point bending test. The mechanical properties of coated samples were studied through

a full factorial design of experiment (DOE) and the relationship between these

coatings, baseboards, fiber orientations (MD/CD), pigments shape factor, calendering

and the mechanical properties at different humidities and temperatures were

investigated.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Analysis of variance (ANOVA) and main effect plot results indicates that all