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Evaluation of polymer film barrier coating incorporating two different nanopaticle size

Permanent Link: http://ufdc.ufl.edu/UFE0041344/00001

Material Information

Title: Evaluation of polymer film barrier coating incorporating two different nanopaticle size
Physical Description: 1 online resource (62 p.)
Language: english
Creator: Jeon, Sungwan
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

Subjects / Keywords: barrier, cloisite, laponite, nanocomposite, package, pcn
Agricultural and Biological Engineering -- Dissertations, Academic -- UF
Genre: Agricultural and Biological Engineering thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Among a variety of barrier solutions in the packaging industry, polymer clay nanocomposites (PCN) coatings are attractive due to the potential to enhance barrier properties without modifying the base polymer. PCN barrier coatings require exfoliated microstructures of impermeable anisotropic fillers that can extend the tortuous path of permeating gas molecules. The fundamental expression for gas permeation was demonstrated with a variety of models based on Neilson?s detour theory to design better barrier properties of PCN. Based on the physical detour path theory, a system using mixture of two particles with different aspect ratios was suggested to obtain higher barrier properties than with either particle alone by extending tortuous paths. The purpose of using two nanoparticle sizes was to attempt to achieve greater filler packing density and thus, greater tortuous path lengths resulting in greater barrier properties. In this study, a model of the proposed PC2N system and an equation to estimate relative permeability (Rp) of PC2N was developed. It was found that no barrier enhancement was achieved at constant volume fraction loadings. As a result it can be concluded that the final Rp of PC2N is governed by total volume fraction of filler. To estimate effects of orientation of nanoparticle platelets in PC2N system on Rp, the orientation parameter (s) and Rp equation suggested by Bharadwaj were used. It was found that as volume fraction increased, particle orientation become less important. In order to investigate effects of PC2N coating on barrier properties, PC2N solutions were prepared and applied to substrates of known oxygen transmission rate. Results confirmed that barrier properties of PC2N were governed by total effective volume of filler particles, which are well dispersed in polymer matrix. It was found that PC2N coated films with a moderate barrier properties PCN offered benefits over in terms of coating weight and greater optical clarity.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Sungwan Jeon.
Thesis: Thesis (M.S.)--University of Florida, 2009.
Local: Adviser: Welt, Bruce A.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0041344:00001

Permanent Link: http://ufdc.ufl.edu/UFE0041344/00001

Material Information

Title: Evaluation of polymer film barrier coating incorporating two different nanopaticle size
Physical Description: 1 online resource (62 p.)
Language: english
Creator: Jeon, Sungwan
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

Subjects / Keywords: barrier, cloisite, laponite, nanocomposite, package, pcn
Agricultural and Biological Engineering -- Dissertations, Academic -- UF
Genre: Agricultural and Biological Engineering thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Among a variety of barrier solutions in the packaging industry, polymer clay nanocomposites (PCN) coatings are attractive due to the potential to enhance barrier properties without modifying the base polymer. PCN barrier coatings require exfoliated microstructures of impermeable anisotropic fillers that can extend the tortuous path of permeating gas molecules. The fundamental expression for gas permeation was demonstrated with a variety of models based on Neilson?s detour theory to design better barrier properties of PCN. Based on the physical detour path theory, a system using mixture of two particles with different aspect ratios was suggested to obtain higher barrier properties than with either particle alone by extending tortuous paths. The purpose of using two nanoparticle sizes was to attempt to achieve greater filler packing density and thus, greater tortuous path lengths resulting in greater barrier properties. In this study, a model of the proposed PC2N system and an equation to estimate relative permeability (Rp) of PC2N was developed. It was found that no barrier enhancement was achieved at constant volume fraction loadings. As a result it can be concluded that the final Rp of PC2N is governed by total volume fraction of filler. To estimate effects of orientation of nanoparticle platelets in PC2N system on Rp, the orientation parameter (s) and Rp equation suggested by Bharadwaj were used. It was found that as volume fraction increased, particle orientation become less important. In order to investigate effects of PC2N coating on barrier properties, PC2N solutions were prepared and applied to substrates of known oxygen transmission rate. Results confirmed that barrier properties of PC2N were governed by total effective volume of filler particles, which are well dispersed in polymer matrix. It was found that PC2N coated films with a moderate barrier properties PCN offered benefits over in terms of coating weight and greater optical clarity.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Sungwan Jeon.
Thesis: Thesis (M.S.)--University of Florida, 2009.
Local: Adviser: Welt, Bruce A.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0041344:00001


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EVALUATION OF POLYMER FILM BARRI ER COATING INCORPORATING TWO DIFFERENT NANOPATICLE SIZE By SUNGWAN JEON A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2009 1

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2009 Sungwan Jeon 2

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To my mom, dad, and brother 3

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ACKNOWLEDGMENTS I am grateful to Dr. Bruce A. Welt, my advi sor. Without whose suppor t this project would not have been possible. I would like to thank Jinwoo Kwak, my co-worker. The times I spent with Jinwoo were very valuable. I would not have achieved my master degree without his assistance. I am also grateful to Dr. Laurie Gowe r and Dr. Allen Turner for agreeing to serve on my committee. I would like to thank Dr. JoAnn Ratto in U.S. army Natick Soldier Research, Development and Engineering Cent er (NSRDEC). This thesis is also result of enduring support, love and cooperation of my parents. Most of all I would like to thank th e faculty and staff in Department of Agricultural and Biological En gineering at the Univ ersity of Florida. 4

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TABLE OF CONTENTS page ACKNOWLEDGMENTS ............................................................................................................... 4LIST OF TABLES ...........................................................................................................................7LIST OF FIGURES .........................................................................................................................8LIST OF ABBREVIATIONS ........................................................................................................1 0NOMENCLATURE .................................................................................................................. ....11ABSTRACT ...................................................................................................................... .............13 CHAPTER 1 INTRODUCTION ................................................................................................................ ..15Barrier Properties of Nanocomposites ....................................................................................15Permeability .................................................................................................................. ...16Morphology of Polymer Nanocomposites .......................................................................17Non-intercalated .......................................................................................................17Intercalated / Exfoliated ...........................................................................................17Models .............................................................................................................................182 DESIGN OF POLYMER CLAY 2 NANOCOMPOSITE (PC2N) ........................................22Introduction .................................................................................................................. ...........22Consideration of PC2N Barrier Property ................................................................................23Volume Fraction ..............................................................................................................23Effects of relative size of th e smaller nanoparticle (clay2) ......................................23Effects of d-spacing of larger clay particle (clay 1) .................................................23Effects of arrangements of smaller (clay 2) particles ...............................................24Effects of state of aggregation on relativ e permeability (Rp) of PC2N system .......25Orientation .......................................................................................................................263 INCORPORATION OF NANOPATICLE MIXTURES TO ENHANCE BARRIER PROPERTIES OF POLYMER FILMS ..................................................................................39Introduction .................................................................................................................. ...........39Materials and Methods ...........................................................................................................41Materials ..................................................................................................................... .....41Preparation of PCN and PC2N Solutions ........................................................................41Preparation of Coated Samples .......................................................................................43OTR Measurements .........................................................................................................43Results and Discussions ....................................................................................................... ...435

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4 CONCLUSIONS ................................................................................................................. ...53 APPENDIX A Raw OTR data ................................................................................................................ ........55B PC2N Procedure .............................................................................................................. .......59REFERENCES .................................................................................................................... ..........60BIOGRAPHICAL SKETCH .........................................................................................................62 6

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LIST OF TABLES Table page 1-1 Models for predicting barrier properties of platelet filled nanocomposites (adapted from Takahashi et al., 2006) ..............................................................................................193-1 Specific information of material us ed for PCN and PC2N composite films .....................45A-1 Oxygen Transmission Rate (cc/m2/day) of Substrate Polymer Film .................................55A-2 Oxygen Transmission Rate (cc/m2/day) of Substrate and PCN Film ...............................56A-3 Oxygen Transmission Rate (cc/m2/day) of PC2N System ................................................57A-4 Oxygen Transmission Rate (cc/m2/day) of Cloisite ..........................................................58B-1 Procedure and Control Factor of PC2N Film ....................................................................59 7

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LIST OF FIGURES Figure page 1-1 Barrier to permeation imposed by nanoparticles imbedded in a polymeric matrix. ..........201-2 Permeability model for gas transfer through a polymer ....................................................201-3 Illustration of different states of dispersion of organ clays in polymers ............................212-1 A predicting schematic of PC2N system. ..........................................................................272-2 Effects of relative size of clay 2 on relative permeability of PC2N: obtained by equation (2-1) (l1=100 nm, l2=0.1 ~ 10 nm, w1=w2=1 nm, b1=10 nm, b2=l2/10, h1=1 nm, h2=0.001 nm, 1=0.1) ...................................................................................................282-3 Effects of d-spacing of clay 1 on re lative permeability of PC2N: obtained by equation (2-1) (l1=100 nm, l2=5 nm, w1=w2=1 nm, b1= l1/10, b2=l2/10, h1=1 ~ 100 nm, h2=0.001 nm, 1=0.1) ..................................................................................................292-4 Schematic diagram showing effects of changes in d-spacing ............................................302-5 Effects of increased d-spacing of clay 1 on relative permeability of PC2N obtained by equation (2-1) (l1= 100 nm, l2= 5 nm, w1=w2=1 nm, b1= l1/10, b2=l2/10, 1=0.1) .......312-6 Effects of the state of aggregation of clay 1 on relative permeability of PC2N: obtained by equation (2-1) (l1= 100 nm, l2= 5 nm, w2 = 1 nm, b1= l1/10, b2=l2/10, h1= 1 nm, h2= 0.001 nm, 1=0.1) .............................................................................................322-7 Arrangement of clay 2 particles in PC2N system: (a) Inse rtion of high volume fraction of clay 2 particles into intergalle ry regions of clay 1, (b) Dispersion of high volume fraction of clay 2 in a polymer matr ix, (c) Insertion of a low volume fraction and (d) Dispersion of a low volume fraction. ....................................................................332-8 Effects of the volume fraction of clay 1 on relative permeability of PC2N obtained by equation (2-1) (l1= 100 nm, l2= 5 nm, w1 = w2 = 1 nm, b1= l1/10, b2=l2/10, h2= 0.001 nm, 2= 0.1, 2=0.01 ~ 1) .......................................................................................342-9 Effects of particle orientation on relati ve permeability in exfoliated nanocomposites .....352-10 Effects of orientation angl e (degree) and volume fraction ( ) on relative permeability of Laponite JS ...............................................................................................362-11 Effects of orientation angl e (degree) and volume fraction ( ) on relative permeability of Cloisite Na+ ..............................................................................................372-12 Effects of orientation angl e (degree) and volume fraction ( ) on relative permeability of mixture composed of Laponite JS and Cloisite Na+ .................................388

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3-1 Oxygen Transmission Rate (OTR) instrument schematic .................................................463-2 Substrate polymer film Oxygen Transmission Rate ..........................................................473-3 OTR and (a) Relative Permeability (b) of Samples; P (8wt% of PVOH), PL (8wt% of PVOH and Laponite JS), PCL (8wt% of PV OH, 4wt%of Cloisite Na+ and Laponite JS) ........................................................................................................................... ...........483-4 Oxygen Transmission Rate versus Ratio of Cloisite Na+ to Laponite JS .........................503-5 Oxygen Transmission Rate vs. PVOH with Cloisite Na+ film according to Cloisite Na+ wt% .............................................................................................................................513-6 Dependence of clay content of loaded in PCN on OTR values .........................................52 9

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LIST OF ABBREVIATIONS APP Atmospheric Pressure Plasma BON Biaxially Oriented Nylon CEC Cation Exchange Capacity LLDPE Linear Low Density Poly Ethylene LMD Low Molecular Weight MMT Montmorilonite MW Number-average Molecular Weight OAC Organic Ammonium Chloride OPP Oriented Poly Propylene OTR Oxygen Transmission Rate PC PVOH with Cloisite Na+ PCL PVOH with Cloisite Na+ and Laponite JS PCN Polymer Clay Nanocomposite (barrier coating of one nanoparticle type) PC2N Polymer Clay 2 Nanocomposite (b arrier coating of two types of nanoparticles) PE Poly Ethylene PET Polyethylene Terephthalate PL PVOH with Laponite JS PVOH Poly Vinyl Alcohol Rp Relative Permeability 10

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NOMENCLATURE A Area of film (cm2) c1 gas concentration inside film c2 gas concentration outside film J diffusive flux of gas through film (cm3/cm2/s) L film thickness p1 partial pressure of gas inside film p2 partial pressure of gas outside film P gas permeability coefficient (ccmil/cm2/day) S Henrys Law gas solubility coefficient t time H vertical length h1 d-spacing of clay 1 h2 d-spacing of clay 2 da d-spacing of clay 1 increases L lateral length l1 length of clay 1 l2 length of clay 2 b1 lateral distance between clay 1 platelets b2 lateral distance between clay 2 platelets w1 width of clay 1 w2 width of clay 2 Veff1 effective volume of clay 1 Veff2 effective volume of clay 2 clay layers volume fraction 11

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1 clay 1 layers volume fraction 2 clay 2 layers volume fraction 12

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Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science EVALUATION OF POLYMER FILM BARRI ER COATING INCORPORATING TWO DIFFERENT NANOPATICLE SIZE By Sungwan Jeon December 2009 Chair: Bruce Welt Major: Agricultural and Biological Engineering Among a variety of barrier solutions in the packaging industry, polymer clay nanocomposites (PCN) coatings are attractive due to the potential to enhance barrier properties without modifying the base polymer. PCN barrier co atings require exfoliated microstructures of impermeable anisotropic fillers that can extend the tortuous path of permeating gas molecules. The fundamental expression for gas permeation was demonstrated with a variety of models based on Neilsons detour theo ry to design better barrier pr operties of PCN. Based on the physical detour path theory, a system using mixtur e of two particles with different aspect ratios was suggested to obtain higher barrier properties than with either part icle alone by extending tortuous paths. The purpose of us ing two nanoparticle sizes was to attempt to achieve greater filler packing density and thus, greater tortuous path lengths resulting in greater barrier properties. In this study, a model of the proposed PC2N system and an equation to estimate relative permeability (Rp) of PC2N was developed. It was found that no barrier enhancement was achieved at constant volume fraction loadings. As a re sult it can be conclude d that the final Rp of PC2N is governed by total volume fraction of filler. To estimate effects of orientation of nanoparticle platelets in PC2N system on Rp, the orientation parameter (s) and Rp equation 13

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suggested by Bharadwaj were used. It was f ound that as volume fraction increased, particle orientation become less important In order to invest igate effects of PC2N coating on barrier properties, PC2N solutions were prepared and applied to substrates of known oxygen transmission rate. Results confirmed that barr ier properties of PC2N were governed by total effective volume of filler particles, which are well dispersed in polymer matrix. It was found that PC2N coated films with a mode rate barrier properties PCN offered benefits over in terms of coating weight and greater optical clarity. 14

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CHAPTER 1 INTRODUCTION Barrier Properties of Nanocomposites Polymer Clay Nanocomposite (PCN) materials are some of the most attractive materials in the packaging industry because of its enha nced barrier property when compared to homopolymers or conventional microcomposites [1 ]. Traditionally, enhan ced barrier properties of PCNs are achieved by dispersing impermeable anisotropic fillers such as 2:1 montmorilonite (MMT), which is an expandable dioctahedral smectit e with a sufficient aspect ratio, directly into base polymers [2]. While specialized PCN polymer s are commercially available, they tend to be highly proprietary and therefore such clays ar e expensive. Therefore, packaging polymer consumers would prefer to apply a PCN barrier coating system to unmodified polymer substrates. The mechanism of gas permeation begins when gas molecules are adsorbed on the surface of a film. Subsequently, these molecules diffuse into the amorphous regi ons of polymer matrix, which have a lower packing density of polymer ch ains than crystalline regions. Higher packing densities of crystalline regions interrupt the vacancy hopping-bas ed diffusion of gas molecules [3]. In homopolymers, increasing crystallinity or po lymer thickness is the only way to enhance barrier properties. However, dispersion of impermeable nanofillers into the polymer matrix efficiently enhances the crystall inity of the polymer resulting in greater barrier properties. The mechanism of gas permeation in Polyme r Clay Nanocomposite (PCN) materials is similar to regular polymers. Thus, when gas mo lecules pass through a PCN film, clay platelets efficiently increase the diffusion path of gas molecules, as illustrated in Figure 1-1 Thus, longer detour lengths, and lower permeation values are attained by many a nd/or large platelets embedded in the polymer matrix. 15

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Permeability Permeation of a gas through a polymer film is a combination of diffusion and solubility. Gas will diffuses through a PCN film at a constant rate if a constant con centration gradient is maintained across the film. The diffusive flux, J, of a gas in a film is the amount (Q) passing through a surface of area (A) normal to the di rection of flow during time (t), i.e. At Q J (1-1) The diffusive flux of a gas through a film is directly proportional to the concentration gradient, L C across a surface of thickness ( L) and is given by Ficks first law: L C DJ (1-2) Where, J is the flux per unit area of permean t through the PCN, C is the concentration of the permeant, D is the diffusion coefficient for a particular gas diffusing through a particular film. D reflects the speed at which the permeant diffuses through the PCN. As shown in Figure 1-2 when a steady state is attained, the flux is constant and Equation (1-2) can be integrated across the tota l thickness of the f ilm length (L). )(12CCDJL (1-3) Rearranging the terms L CCD J )(21 (1-4) Equation (1-4) can be rewritten by substituting for J using Equation (1-1). L AtCCD Q )(21 (1-5) At sufficiently low concentrations, Henry s law applies and C can be expressed as 16

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SpC (1-6) Where S is the solubility coefficient, p is the partial pressure or permeant gas. By combining Equation (1-5) and Equation (1-6), L AtppDS Q )(21 (1-7) DS is the permeability coefficient and is represented by the symbol P. Which can be re-arranged to )(21ppAt QL P (1-8) Four assumptions were made in the derivation of permeability coefficient. First, diffusion is at steady state. Second, the concentration-distance relationship th rough the film is linear. Third, diffusion takes place in one dire ction only, and, fourth, both D and S are independent of concentration. Morphology of Polymer Nanocomposites Non-intercalated Morphology of PCN can be classifi ed as three typical structur es including nonintercalated, intercalated and exfoliated [5]. When polymer cannot diffuse into the intergallery region between two platelets, a microcomposite consisting of micr on sized agglomerated cl umps of particles or tactoids is be obtained. This non-intercalat ed structure does not o ffer beneficial barrier properties. In contrast, the othe r two types of composites morphol ogies, which can be called as a nanocomposite, offer benefits to barrier properties. Intercalated / Exfoliated When several polymer chains are inserted in to the intergallery space between particles resulting in fixed, but enlarged interlayer spacing, intercalat ed morphology is achieved. Fully 17

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exfoliated structures (particles fully disperse d in polymer) are the ideal morphology at small filler loadings to obtain superior barrier properties. Completely separated and dispersed fillers in the polymer matrix results in random arrangement of particles in polymer, which is called an exfoliated structure. These three typical structures are shown in Figure 1-3 However, various morphologies exist in the real PCN system and a general micros tructure of a real exfoliated PCN material can be described as a mixture of intercalated and exfoliated structure with hi gher degree of exfoliated regions. A specific desired structure of PCN ca n be tailored by controlling in several ways. Selection of materials for PCN requires some careful consideration. For instance, a natural MMT is a hydrophilic and compatible with polar polymers such as polyvinyl alcohol (PVOH). However, interlayer distances are not sufficient to allow PVOH chains to diffuse into platelet between particles, ther efore particle surface mo dification are sometimes required using organic modifiers. Their modifica tions typically involve ca tion exchange reaction. In general, grafted organic modi fiers act as an agent for increas ing interlayer space. It is necessary to matching polarity be tween polymer matrix and a modi fier to have more favorable interactions. Processing methods also have significant effects on morphology of the final PCN. Key processing parameters include shear stress, time, and temperature. These parameters must be optimized in order to achieve exfoliation. Models Various models have been proposed to predict barrier properties of platelet filled nanocomposites. These models are usually based on random, parallel platel ets perpendicular to the permeation direction. As shown in Table 1-1 these models are sorted by filler type. Through 18

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these models, relative permeability (Rp) may be predicted. A common aspect of these models is the prediction of decreasing Rp with increasing volume fraction of filler. Factors critical to modeling PCN barrier properties are (1) PCN thickness, (2) longer detour length by intercalated or /and exfoliated morphology, (3) opt imum processing control, and (4) consideration of compatibili ty between polymer and clay. Table 1-1. Models for predicting barrier properties of platelet filled nanocomposites (adapted from Ref. [6], c opyright by Elsevier) Model Filler type Particle geometry Formulas Nielsen [7] Ribbona (P0/P)(1-) = 1+/2 Cussler [8] (Regular array) Ribbona (P0/P)(1-) = 1+(/4 (Random array) Ribbona (P0/P)(1-) = (1+ /3)2 Gusev and Lusti [9] Diskb (P0/P)(1-) = exp[( /3.47)0.71] Fredrickson and Bicerano [10] Diskb (P0/P)(1) = 4(1+x+0.1245x2) /(2+x))2 where x= ln Bharadwaj [11] Diskb (P0/P)(1) = 1+0.667 (S+(1/2)) where S = orientation factor (from -1/2 to 1) a For ribbons, length is infinite, widt h, w; thickness, t; aspect ratio, = w/t. b For disks, circular shape of diam eter d and thickne ss t; aspect ratio, =d/t 19

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Figure 1-1. Barrier to permeation imposed by nanoparticles imbedded in a polymeric matrix. Figure 1-2. Permeability model for gas transfer through a polymer 20

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Figure 1-3. Illustration of di fferent states of dispersion of organ clays in polymers 21

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CHAPTER 2 DESIGN OF POLYMER CLAY 2 NANOCOMPOSITE (PC2N) Introduction Preparation of an effective PCN requires consideration of the microstructure of clay platelets. Typically, published rese arch has shown one type of nano-particle is used to create PCNs [12]. However, it believed that a mixture of two particles with di fferent sizes and aspect ratios may provide greater tortuous paths and th erefore, greater barrier properties than PCNs produced from just one particle variety. Hence, PCN produced with two particle types is referred to as PC2N. Figure 2-1 shows the concept of enhancing pa rticle packing de nsity using two types of nano-particles [21] A structure as shown in Figure 2-1 should have the same effect as increasing total volume fraction of particles, wh ich would enhance barrier properties of the PCN. A model was developed to pred ict Rp of PCN consisting of two types of clay particles having different aspect ratios. The Rp of the PC2N can be calculated using the following equation (2-1), 1 2 2 21 12 )1(2 H v LL H Reff T P (2-1) Where, H and L are vertical le ngth (h1+w1) and lateral length (l1+b1) occupied by clay 1, respectively, h1, w1, l1, b1, 2, Veff2 are d-spacing, width, lateral distan ce between two particles, volume fraction of filler and effective volume of a clay particle. Subscripts 1, 2 and t represent clay particles having la rger and smaller aspect ratio a nd both, respectively [21]. Where, effective volume can be calculated using Equation (2-2) and (2-3). )()(11 2 111whblveff (2-2) )()(22 2 222whblveff (2-3) 22

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Based on this model for PC2N systems, barrier property prediction may be made. Consideration of PC2N Barrier Property Volume Fraction When two different types of clays are disperse d in a polymer matrix, the size effect of two particles has to be known. High barrier prope rties may be achieved by designing the maximum detour length in the microstruc ture of composite materials. Effects of relative size of th e smaller nanoparticle (clay2) Figure 2-2 shows effects of relative size of clay 2 on Rp of PC2N. The relative size of clay 2 appears to offer no effect on decreasing permeability. Figure 2-2 predicts constant Rp values at each volume fraction of clay 2. Higher aspect rati o of clay 2 promises a longer tortuous path, but this requires a lower quantity of clay 2 possibly resulting in a compensation effect. Therefore, total distance, d' in the system is similar for all aspect ratio of clay 2. However, as clay 2 volume fraction increases, Rp decreases due to increased number of platelets of clay 2 in the same effective volume created by clay 1 particles. Fr om this relationship, it can be deduced that volume fraction of clay 2 is more a significant factor than size of pl atelets at fixed volume fraction of clay 1; this sh ould result in a composite with better barrier properties. Effects of d-spacing of la rger clay particle (clay 1) 23 Another critical factor in th e process of making PC2N is the choice of alkyl ammonium ions. Ion exchange of cations (Na2+ or Ca2+) in the intergallery region of natural clays by alkyl ammonium ions leads to expansion of this regi on as well as modification from hydrophilic to organophilic, thus enabling diffusion of polymer chains. The number of carbons in alkyl ammonium and the layer charge of the clay part icle will determine the arrangement of alkyl ammonium chains in the intergallery region. Diffusion of polymer chains will be determined by shear forces and molecular weight of polymer [13].

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Therefore, d-spacing between clay platelets vary depending on parameters that can be controlled during processing. In the PC2N syst em, d-spacing of clay 1 affects Rp as shown in Figure 2-3 The larger the d-spacing of clay 1 at c onstant volume fractions of two clays, the higher the Rp value. This phenomenon may be cau sed by a lower number of clay 1 platelets per unit volume as increased d-spacing of clay 1 leads to more sparse distribution of clay 1, corresponding to decreased tortuosity. There would be no increment in da contributed by clay 2 particles in fixed volume fraction of clay 2. Effe cts of increased volume fr action of clay 2 on Rp has the same tendency as the one shown in Figure 2-2 That is, detour length increased by insertion of clay 2 into the intergallery regi on has constant value when the volume fraction of clay 2 is fixed. D-spacing can be increased by cation exchange and shear processing, but it is also possible to increase d-spacing by inser tion of clay 2 between clay platelets 1. Effects of arrangements of smaller (clay 2) particles The preceding expected Rp values are based on the assumption that there are no local changes in d-spacing of clay 2 (h2) as d-spacing of clay 1 (h1) generated during the insertion process can result in a deviation from the general barrier properties. However, the case that some increment of h can occur as shown in Figure 2-4 should be considered. This increase in dspacing would occur by insertion of exfoliated clay 2 in the polymer matrix into the intergallery region with the aid of cation exchange reactions and shear processes. Thus is required to be substituted for h1 to estimate Rp of this material and can be defined as shown in Equation (24). 1h' 1h12222 12)( hhhwlh (2-4) Figure 2-5 illustrates how the arrangement of clay 2 particles affects d-spacing of clay 1 corresponding to its Rp. When a constant number of platelets of clay 2 at a fixed volume fraction 24

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are dispersed in the intergallery of clay 1, mo re layers are formed, th erefore reducing the number of clay platelets in each layer. This means that although d-spacing can be increased by creating more layers, the possibility that a diffusant en counters a platelet when passing by a layer would be lower. As a result, effects of increased tortuous path cannot exceed a critical Rp by compensation effects of da of clays as d-spacing of clay 1 in creases. The initial dramatic decrease in Rp when approaches to 0 suggest that da plays a key role by forming a densely packed arrangement in the reduction of permeability. Therefore, densification of platelets with higher volume fraction may be the ideal approach to achi eve a superior barrier material. However, when the spacing between clay platel ets including a lateral distance is not enough for a diffusant to bypass, good barrier properties cannot be obtained. In other words, the state of aggregation of particles can have significant effect on permeabili ty resulting in increas ed Rp at higher volume fraction. Therefore, an understanding of the aggregation is required for all types of nanocomposites materials since this not only affects barrier propert ies, but also other physical properties. In this work, the state of aggregation of clay 1 particles is inve stigated by varying the width of clay 1 from 0 to 1000 nm in Equation (2-1). 1hEffects of state of aggregation on relative permeability (Rp) of PC2N system As shown in Figure 2-6 a higher degree of aggregatio n results in higher Rp because aggregates of particles that are not sepa rated from the stacked agglomerate lower N1, shorten the detour length and even reduce the possibility of successful inserti on of clay 2. This figure also shows that as volume fraction of clay 2 increas es, the gap between Rp of initial point at w1 of 1 nm and one obtained at w1 of 1000 nm is decreased. Increased volume fraction of clay 2 will result in increased da due to insertion or dispersion in polymer matrices comparing to lower volume fraction as shown Figure 2-7 If the assumption that d-spacing of clay 1 is determined 25

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only by a cation exchange reaction and shear forces, Rp will depend on d-spacing of clay 1 at fixed ratio of clays. This dependence is shown in Figure 2-8 As the volume fraction of clay 1 increases, Rp of all d-spacing conditions will converge to 0 at the volum e fraction of 0.9. The dense arrangement of clay 1 results in lower Rp and therefore, there woul d be no change in the effect of da caused by clay 2 once its volume fraction is set. Orientation Previous studies on barrier properties based on tortuosity or diffusion detour theory have focused on the aspect ratio of clay platelets [14-15] and volume fraction of filler [16-18]. Existing barrier models are based on the one co mmon assumption that al l clay platelets are dispersed in an orientation that is normal to the diffusant. However, the 3-dimensional displacement of clay platelets in the actual ex foliated PC2N system will cause some deviation from theoretical permeability. Bharadwaj reported th e effect of orientati on of clay platelets on Rp of PCN [17]. Based on this wo rk, effects of orientat ion of clay platelets on Rp of PC2N can be estimated as shown in Figure 2-9 This figure shows that enhanced relative permeability (Rp) is achieved when orientation parameter (S) appr oaches 1. Low Rp can be obtained by increasing aspect ratio of clay pl atelets as described in Figure 2-9 Bharadwaj et al. (2002) predic ted a following equation, whic h considers orientation in predicting Rp [17]. 2 1 3 2 2 1 10S W L P P (2-5) Equation (2-6) was derived from e quation (2-5), for use with PC2N. 2 1 3 2 22 1 )(12 2 2 1 1 1 0S W L W L P PCL (2-6) 26

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Figures 2-10 2-11 and 2-12 are plotted by Equation (2-5) a nd (2-6). All Rp values were calculated using actual size data of Cloisite Na+, and Laponite JS. Both clays have similar tendency that Rp is increased as orientation angle of clay platelets increasing. However, Cloisite Na+ has slightly lower Rp due to its larger aspect ratio. Effects of orientation of polymer chains on barrier properties of a pol ymer were examined by Somlai et al. (2005) [19]. The relationship between orientation of polymer chains and permeability is not well reported in their work. It is well known that proce sses that oriented polymer film s tend to enhan ce strength and barrier properties. It is believed that grea ter molecular alignment causes an increase in crystallinity and therefore, barrier properties. When orientation is performed on polymer films with clay nanoparticles it is likely that the particle ali gnment is enhanced as well. Figure 2-1. A predicting sc hematic of PC2N system. 27

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Figure 2-2. Effects of relative size of clay 2 on relative permeability of PC2N: obtained by equation (2-1) (l1=100 nm, l2=0.1 ~ 10 nm, w1=w2=1 nm, b1=10 nm, b2=l2/10, h1=1 nm, h2=0.001 nm, 1=0.1) 28

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Figure 2-3. Effects of d-spacing of clay 1 on re lative permeability of PC2N: obtained by equation (2-1) (l1=100 nm, l2=5 nm, w1=w2=1 nm, b1= l1/10, b2=l2/10, h1=1 ~ 100 nm, h2=0.001 nm, 1=0.1) 29

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Figure 2-4. Schematic diagram showi ng effects of changes in d-spacing 30

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Figure 2-5. Effects of increased d-spacing of cl ay 1 on relative permeability of PC2N obtained by equation (2-1) (l1= 100 nm, l2= 5 nm, w1=w2=1 nm, b1= l1/10, b2=l2/10, 1=0.1) 31

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Figure 2-6. Effects of the stat e of aggregation of clay 1 on relative permeability of PC2N: obtained by equation (2-1) (l1= 100 nm, l2= 5 nm, w2 = 1 nm, b1= l1/10, b2=l2/10, h1= 1 nm, h2= 0.001 nm, 1=0.1) 32

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Figure 2-7. Arrangement of clay 2 particles in PC2N system: (a) In sertion of high volume fraction of clay 2 particles into intergallery regions of clay 1, (b) Dispersion of high volume fraction of clay 2 in a polymer matr ix, (c) Insertion of a low volume fraction and (d) Dispersion of a low volume fraction. 33

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Figure 2-8. Effects of the volume fraction of cl ay 1 on relative permeabili ty of PC2N obtained by equation (2-1) (l1= 100 nm, l2= 5 nm, w1 = w2 = 1 nm, b1= l1/10, b2=l2/10, h2= 0.001 nm, 2= 0.1, 2=0.01 ~ 1) 34

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S = 0 S = 1 S = -1/2 Figure 2-9. Effects of particle orientation on relative permeability in exfoliated nanocomposites 35

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Figure 2-10. Effects of orientation angle (degree) a nd volume fraction ( ) on relative permeability of Laponite JS 36

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Figure 2-11. Effects of orientation angle (degree) a nd volume fraction ( ) on relative permeability of Cloisite Na+ 37

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Figure 2-12. Effects of orientation angle (degree) a nd volume fraction ( ) on relative permeability of mixture composed of Laponite JS and Cloisite Na+ 38

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CHAPTER 3 INCORPORATION OF NANOPATICLE MIXTURES TO ENHANCE BARRIER PROPERTIES OF POLYMER FILMS Introduction Long shelf-life foods require hi gh barrier packaging. Traditional appro aches to producing high barrier materials involve multi-layer lamina te films. Each layer of a multi-layer film contributes to overall properties of the structure. Multi-layer food packaging structures used by the United States military typi cal contain an aluminum foil la yer. The foil layer provides high barrier properties. However, foils are prone to pinholes, which create quality control issues. Also, processes involving foils prevent us e of microwaves. Therefore, a high-barrier film without foil is desired. Polymer clay nanocomposites (PCN) are attracti ve in packaging applications due primarily to enhanced barrier properties [20]. Improvement s to barrier properties with low concentrations of clay nano scale particles have been reported by many research groups [16,18]. Several models have been suggested to predict gas barrier properties in polyme rs and PCN materials. According to Nielsens model (1967) [7], ba rrier properties of PCN can be changed by the microstructure of particle-polymer matrix as well as the aspect ratio of particles. Nielsen proposed that the mechanism of enhanced barrier was increased diffusion path. Other models to estimate the relative permeability (Rp) of composite materials ar e based on this detour path model. Therefore, the microstructure of clay particles is the crucial factor which determines the barrier properties of a composite material. Three particle-polymer microstructures are gene rally recognized that are related to degree of dispersion of particles in polymer. These are referred to as non-intercalated, intercalated and exfoliated and may be loosely inte rpreted as poorly dispersed with irregularly spaced aggregates, 39

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dispersed with regularly spaced aggregates, and completely dispersed particles, respectively. Exfoliated structures provide superior gas barrier properties wh en compared to the other two structures. Incorporation of inorganic pa rticles into polymers is difficult due to high temperatures, high viscosities and polarity incompatibilities between particles an d polymer. Therefore, commercial PCN materials tend to involve proprietary proce ssing technologies and command high prices. Work by Kwak et al (2009) [24] explored the possibi lity of developing an aqueous based PCN that could be applied as a coating or paint and then dried in place to achieve a high barrier coating on inexpensive, commodity base materials. Development of candidate PCN coating solu tions requires consideration of particlepolymer compatibility, particle dimensions (a spect ratio) and coati ng adhesion onto base polymers. Properties of PCN materials depend on pr operties of particles in cluding layer charge, water adsorption capacity, cation exchange capacity (CEC), aspect ratio, viscosity of the final composite system, and the arrangement of cation exchange ions in the intergallery region between negatively charged particle layers. Spacing between two cl ay platelets can be enlarged by via cation exchange. Once the intergallery region is opened, exfoliation of clay platelets in the polymer matrix usually can be achieve d with high shear processing [13]. For any coating to be effective, it must bind well to the substrate. Even if a PCN coating were used within a multi layer film structure good adhesion would be required to achieve high barrier. Adhesion is enhanced through increased surface area and increased concentrations of polar functional groups on surface s. Various techniques have b een proposed to modify the surface of polymeric materials such as corona discharge [22], plasma [23] and chemical modification. Atmospheric plasma treatmen t is becoming popular due relative treatment 40

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uniformity and the ability to modify gas mixtures to suit applications. Plasma is created by applying energy to a gas to produce excited species and ions. Polymer film surfaces are activated by plasma treatment though chemical reaction with and etching. Optimization of conditions for effective plasma treatment was done previously by Kwak et al. [24]. Therefore, the purpose of this work is to (1) develop a model to predict relative permeability, Rp, of nano-composite incorporati ng two different particles (Laponite JS and Cloisite NA+ referred to as PC2N), (2) prepare PC2N solutions and apply to substrates of known oxygen transmission rate in order to experimentally measure Rp, and (3) produce multilayer barrier films using PC2N applications that provide promise as a replacement for foil in high-barrier, multi-layer films. Materials and Methods Materials PCN and PC2N solutions were made with a synthetic layered silicate, Laponite JS and a natural montmorillonites, Cloisite Na+ (Southern Clay Products, L ouisville, KY). PVOH was supplied by Scientific Polymer Produc t, Inc. The specific informations of ma terials used for the preparation of composite films are listed in Table 3-1 Organic ammonium chloride (OAC), [2-( Acryloyloxy)ethyl]-t rimethyl ammonium chloride was used for intergallery modificatio n. A multi-layered film consisting of oriented polypropylene (OPP) and linear low-density poly ethylene (LLDPE) (Master Packaging Inc., Tampa, FL) was used as a substrate for coating. Preparation of PCN and PC2N Solutions Two PCN solutions containing La ponite JS or Cloisite Na+ respectively were prepared using the same method. At first, OAC buffer solution which amount is compare to 1 wt% of clay 41

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was added into a corresponding amount of deionized water at 40C and pH 10 were premixed for 2-3 minutes with a magnetic stirrer. Each clay powder was added each beaker gradually to prevent aggregation. Prepared clay solutions were placed at room temperature for about 1 day to allow for cation-exchange in order to increase inter-particle distances. 8 wt% polymer stock solutions were prepared by dissolving PVOH in deionized water at 80C and stirring with magnetic stirrer for 6 8 hours. Prepared PVOH st ock solution was added to clay solutions and mixed for 1 hour with a magnetic stirrer and then mixed with a high shear mixer (KadyMill-L Kady International, Scarborough, ME) for 10 minut es. Prepared PCN solutions were placed in a hood at ambient temperature for 3 hours dependi ng on viscosity in orde r to allow entrained air bubbles to dissipate. To prepare a PC2N solution, 8wt% polymer stock solution was prepared by dissolving PVOH in deionized water at 80C and stirring with magnetic stirrer. Each clay solution was prepared in the same manner described in the pr eparation of PCN solution and placed at room temperature for the cation excha nge reactions. Laponite JS solutio n was added to polymer stock solution with agitation. Vigorous agitation with a mechanical stirrer for 10 minutes was conducted to prepare an exfoliate d Laponite JS in a PVOH matrix. Prepared PCN solutions consisting of PVOH and Laponite JS are added to Cloisite Na+ clay solutions. Further, strong sh ear force with a mechanical st irrer was required for the final insertion process. This process was done by inserting PVOH mixed with relatively smaller Laponite JS particles into the intergallery region of Cloisite Na+. To investigate effects of the ratio between Cloisite Na+ and Laponite JS in the PC2N system on OTR (cc/m2/day) values, 10:0, 7:3, 5:5, 3:7, and 0:10 of ratios were used. 42

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Preparation of Coated Samples Atmospheric pressure plasma (APP) treatm ents were performed using a Dyne-A-Myte VCP (Enercon Industries Co., Menom onee Falls, WI). Air and nitrogen gas (about 50/50) were used to create plasma. The ranges of flow rate of nitrogen gas, working distance, times of treatment, and the speed of conveyer belt are 10 25 (l/min), 5 25 (mm), 2 4, and 20-30, respectively. Modified surfaces of substrate film s were coated using coating rods with PCN solution. Coated samples were dried for 24 hours at 40C in a vacuum oven to abstract micro bubbles. OTR Measurements Oxygen transmission rates of substrate, PVOH, PCN, and PC2N samples were measured at 0 RH% and 23C in accordance with the procedure described in ASTM D3985-0546 and ASTM F1927-9847 using a Model OX-TRAN 2/20MH (Mocon Corporation, Minneapolis, MN). Permeation cell area was 50 cm2. Following figure 3-1 is schematic of OTR measurement facility. Results and Discussions OTR measurements of three commercially produced multi-layered films were examined to determine which would be best suited for ob serving effects of PCN and PC2N coatings on OTR. Figure 3-2 shows results for base films which ar e three double layered film constructions including oriented poly propylen e / linear low density polyet hylene (OPP/LLDPE), polyethylene terephthalate / polyethylene (PET/PE) and biaxia lly oriented nylon / po lyethylene (BON/PE). The substrate with the greatest initial OT R (OPP/LLDPE) was chosen for this work.. 43

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Figure 3-3 shows effects of coating layers on OTR. OTR values of PVOH (P), PVOH with Laponite JS (PL), PVOH with Cloisite Na+ and Laponite JS (PCL) coated samples were measured. OTR of PVOH-coated sample a bout 10 % of OPP/LLDPE substrate film. Generally, increasing crystallinity of homopolymers tends to decrease gas diffusion rates and therefore OTR as well. Practical limits to degree of crystallinity limit this benefit. Addition of nano particles simulates additional crystal linity, thus reducing OTR beyond what is possible by the polymer alone ( Figure 3-3 ). In this work, PCL-coated sample showed the lowest OTR, with PL-coated samples showing slightly higher OTR than PCL-coated samples. These results showed that a mixture of diffe rent sized particles (PCL-coated samples) offered only a slight improvement over one type of particle (PL-coated samples). This is likely due to the fixed filler volume of 8% filler by weight used to prepare all samples. Perhaps a greater benefit could be seen if particle packing density is shown to increase with the mixture of particles. Effects of different aspect ratios in PC2N systems on OTR are identified by varying the ratio of Cloisite Na+ to Laponite JS ( Figure 3-4 ). There was no significant difference in OTR values based on weight percent (wt %). However, when the volume of Laponite is compared to that of Cloisite in terms of their densities, La ponite can occupy more space in the system than Cloisite for the same weight of clay used. This is contrary to results predicted from the model described in Chapter 2. Figure 3-5 shows that lower OTR resulted from increasing clay weight percent. This tendency was confirmed by our previous work that examined Laponite JS as shown in Figure 3-6 [24]. Figure 3-6 shows OTR as a function of clay concentr ation loaded in the final dried PL film. The lowest OTR value was shown at 50 wt% of clay in the final dried film and, in the range of 44

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20 to 40 wt% of clay concentrati on, there was no signifi cant difference in OTR values. This plot also shows a dramatic increase in OTR values starting at 50 wt% of cl ay concentration which was likely due to particle aggregation and film stability as clay concentration increased. In this study, enhanced barrier properties were shown to follow increased total effective volume of filler particles that were exfoliated in a PC2N system. Also increasing total volume fraction of filler within a practical range is a re latively simple way to im prove barrier property by about one order of magnitude for relatively high transmitting films such as OPP/LLDPE. Although PC2N system did not show significant differences in barrier properties, PC2N composite films (mixture of particles) appeared to offer better optical cl arity than Poly Vinyl Alcohol / Cloisite Na+ (PC) films with comparable OTR. Table 3-1. Specific information of material used for PCN and PC 2N composite films Polymer matrix Inorganic filler LMW1 PVOH Laponite JS Cloisite Na+ MW2 3,000 Density (g/cm3) 0.95 2.86 Viscosity (CP)3 3~4 cp Aspect ratio 25 75~150 d-spacing4 (nm) 0.001 1.17 1, Low molecular weight; 2, Number-average mo lecular weight; 3, 4% aqueous solution at 20 oC; 4, d(001) 45

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Figure 3-1. Oxygen Transmission Ra te (OTR) instrument schematic 46

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Figure 3-2. Substrate polymer film Oxygen Transmission Rate 47

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(a) Figure 3-3. OTR and (a) Relative Permeability (b) of Samples; P (8wt% of PVOH), PL (8wt% of PVOH and Laponite JS), PCL (8wt% of PV OH, 4wt%of Cloisite Na+ and Laponite JS) 48

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(b) Figure 3-3. Continued 49

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Volume of Laponite JS Volume of Cloisite Na+ Figure 3-4. Oxygen Transmission Rate versus Ratio of Cloisite Na+ to Laponite JS 50

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Figure 3-5. Oxygen Transmission Ra te vs. PVOH with Cloisite Na+ film according to Cloisite Na+ wt% 51

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Figure 3-6. Dependence of clay conten t of loaded in PCN on OTR values 52

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CHAPTER 4 CONCLUSIONS Initially, it was believed that a mixture of tw o particles with differe nt aspect ratios may provide longer tortuous paths a nd therefore, enhanced barrier properties than PCNs produced from just one particle variety. To investigate the effect of usi ng a mixture of two particle types on barrier properties quantit atively, a model was developed. Se veral expectations were suggested based on the model. First, the relative size of the smaller particle (clay 2) has no effect. Second, the larger the d-spacing of the larger particle (cla y 1) at constant volume fractions of two clays is in the system, the higher the Rp value is obtained. Third, when a constant number of platelets of the smaller particle (clay 2) at a fixed volume fr action are dispersed in in creased intergallery of clay 1, more layers are formed, therefore reduci ng the number of clay platelets in each layer. Therefore, although d-spacing can be increased by creating more la yers, the possibility that a diffusant encounters a plat elet when passing by a layer is d ecreased. As a result, effects of increased tortuous path ca nnot exceed a critical Rp. Forth, a higher degree of a ggregation results in higher Rp because the aggregates of partic les that are not separated from the stacked agglomerate tend to lower N1, shorten the detour length and even reduce the possibility of successful insertion of clay 2. Finally, the final Rp of PC2N was governed by total volume fraction rather than by the specific relative ratios between clay 1 and 2. The variance in Rp with degree of particle orientation was explored. Most models are based on the assumption that all clay platelets are dispersed in an orientation that is normal to the diffusant. The discrepancy from theoretical barrier models can have significant effect on Rp, es pecially for the PCN materials containing the filler with higher aspect ratio. To estimate the effect of the orientation of platelets on Rp, the orientation parameter (s) and related Rp equation reported by Bh aradwaj et al., (2002) 53

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were used for PC2N system and it was concluded that the higher volume fraction occupied in the system, the less important is orientation of clay platelets. Initially, the effects of different coating layers (P, PL, and PCL) on OTR showed that addition of nano particles redu ces OTR beyond what is possibl e by the homopolymer. Secondly, even though no significant difference in OTR va lues among all ratios for mixing two clays was obtained, the similar tendency that the clay having higher aspect ratio result in slightly lower OTR values was discovered. In conclusion, enhanced barrier properties were shown to follow increased total effective volume of filler particles that are exfoliated in polymer matrix and this tendency confirmed theoretical expectations for PC2N. Although PC2N system did not show significant enhancement in barrie r properties, PC2N composite films with a moderate barrier property appeared to offer greater optical clarity than comparab le PCN with just one, larger nanoparticle. 54

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APPENDIX A RAW OTR DATA Table A-1. Oxygen Transmission Rate (cc/m2/day) of Substrate Polymer Film # of Trial Type of Film OPP/LLDPE PET/PE BON/PE 1 901.5 148 41.777 2 906.4 152.913 44.426 3 887.4 126.1 40.587 4 874 145.648 43.688 Average 892.3 143.2 42.6 SD 14.6 11.8 1.8 55

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Table A-2. Oxygen Transmission Rate (cc/m2/day) of Substrate and PCN Film # of Trial Type of Film P PL PCL 1 89.3 7.2 4.7 2 95.7 7.9 4.4 3 86.3 6.7 5.0 4 90.6 7.5 4.8 Average 90.5 7.3 4.7 SD 3.9 0.5 0.2 56

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Table A-3. Oxygen Transmission Rate (cc/m2/day) of PC2N System # of Trial Ratio of Cloisite Na+ to Laponite JS 10:0 7:3 5:5 3:7 0:10 1 3.6 4.0 4.2 4.3 4.7 2 3.7 3.9 4.4 4.4 4.9 3 3.2 4.0 3.9 4.5 4.6 4 3.6 4.2 4.0 4.5 4.7 Average 3.5 4.0 4.1 4.4 4.7 SD 0.2 0.1 0.2 0.1 0.1 57

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Table A-4. Oxygen Transmission Ra te (cc/m2/day) of Cloisite # of Trial Cloisite concentration (wt%) 10 20 30 40 50 1 4 3.3 2.2 1.4 1 2 4.1 3.3 2.4 1.3 1.1 3 3.8 3.2 2 1.3 1 Average 5.5 7.5 9.2 11.0 13.3 SD 3.0 8.4 13.9 19.3 24.5 58

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APPENDIX B PC2N PROCEDURE Table B-1. Procedure and Control Factor of PC2N Film Process Factors 1 Making clay solutions Clay quantity Clay ratio 2 Letting clay solutions 1day for cation exchange Waiting time Temperature 3 Making PVOH solution wt% of PVOH for adjusting viscosity 4 Mix Clay solution and PVOH solution Mixing time Intensity of Shear force 5 Letting mixed solution 1day for remove bubbles Waiting time Temperature 6 Substrate plasma treatment The speed of conveyer belt Cycles of treatment Flow rate of Nitrogen gas Working distance 7 Coating 8 Drying Time Temperature Vacuum on/off 9 Measure thickness 10 Test OTR 59

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REFERENCES [1] Lange J, Wyser Y. Recent Innovations in Barrier Technologies for Plastic Packaging a Review. Packag Tech and Sci 2003;16: 149 [2] Van Olphen H. An introducti on to clay colloid chemistry: Interscience, New York; 1963 [3] Villaluenga J.P.G, Khayet M, Lopez-Manchado M.A, Valentin J. L, Seoane B, Mengual J.I. Gas transport properties of polypropylene/cl ay composite membranes. Eur Polym J 2007;43:1132-1143 [4] Robertson, Gordon L. Food Packaging Pr inciples and Practice. New York: Marcel Dekker,Inc. 2006. p.55-59 [5] LeBaron P.C, Wang Z, Pinnava ia T.J. Polymer-layered silicat e nanocomposites: an overview, Appl Clay Sci 1999;15:11 [6] Takahashi S, Goldberg H.A, Feeney C.A, Ka rim D.P, Farrell M, OLeary K, Paul D.R. Gas barrier properties of butyl rubber/vermiculite nanocomposite coatings. Polymer 2006;47:3083 [7] Nielsen LE. Models for the Permeability of F illed Polymer Systems. J Macromol Sci (Chem) 1967;A1:929-942 [8] Lape NK, Nuxoll EE, Cussler EL. Polydisperse flakes in barrier films. J Membr Sci 2004;236:29-37 [9] Gusev AA, Lusti HR. Rational Design of Nanocomposites for Barrier Applications. Adv Mater 2001;13:1641. [10] Fredrickson GH, Bicerano J. Barrier properties of oriented disk composites. J Chem Phys 1999;110:2181. [11] Bharadwaj K. Modeling the Barrier Properties of Polymer-Layered Silicate Nanocomposites. Macromolecules 2001;34:9189-9192 [12] Bo Xu, Q.Z, Yihu S, Yonggang S. Calc ulating barrier properties of polymer/clay nanocomposites: Effects of clay layers. Polymer 2006;47:2904-2910 [13] Powell Clois E. Process for treating smectite clays to facilitate exfoliation. Patent, 2001;US 6,271,298,B1 [14] Tie Lan and Thomas J. Pinnavaia, Clay -Reinforced Epoxy Nanocomposites. Chem. Mater. 1994;6:2216-2219 [15] Kazuhisa Y, Arimitsu U, Akane O. Synthe sis and Properties of Polyimide-Clay Hybrid Films. J Polym Sci A: Polym Chem 1997;35:2289 60

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[16] Maged A. O, Vikas M, Massimo M, Ulrich W. S. Polyurethane Adhesive Nanocomposites as Gas Permeation Barrier. J. Macromolecules 2003;36:9851-9858 [17] Bharadwaj R.K, Mehrabi A.R, Hamilton C, Tr ujillo C, Murga M, Fan R, Chavira A. A.K. Thompson, Structure-property relationships in cross-linked polyester-clay nanocomposites. J Polymer 2002;43:3699-3705 [18] Jaime C. Grunlan, Ani Grigor ian, Charles B. Hamilton, Ali R. Mehrabi. Effect of clay concentration on the oxygen permeability and op tical properties of a modified poly(vinyl alcohol). J Appl Polym Sci 2004;93:1102 [19] Somlai L.S, Liu R.Y.F, Landoll L.M, Hiltner A, Baer E. Effect of Orientation on the Free Volume and Oxygen Transport of a Polypropyl ene Copolymer. J. Polym. Sci. Part B: Polym. Phys. 2005;43:1230-1243 [20] Sudip R, Siew Y. Q, Allan E, Xiao D. C. The Potential Use of Polymer-Clay Nanocomposites in Food Packaging, Intern ational Journal of Food Engineering 2006;2:111 [21] Jinwoo K, Sungwan J, Bruce W, Charles B, Siobhan M. Barrier Pr operty Estimation of Polymeric Clay Nanocomposite System Cont aining Two Particle types. Submitted 2009 [22] Sepeur S, Kunze N, Werner B, Schmidt H, UV curable hard coatings on plastics. Thin Solid Films 1999;351:216-219 [23] Kwang Soo K, Chang Mo R, Chan Sup P, Gil Soo S, Chan Eon P. Investigation of crystallinity effects on the surface of oxygen plasma treated low density polyethylene using X-ray photoelectron spectroscopy. Polymer 2003;44:6287 [24] Jinwoo K, Bruce W, Charles B. Enhan cement of Oxygen Barrier with Polymer Clay Nanocomposite Coatings on Polypropylene Trea ted with Atmospheric Pressure Plasma. J Appl Packag Res 2009;3:39-56 61

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62 BIOGRAPHICAL SKETCH Sungwan Jeon was born in Busan, Korea, in December 1980 and moved to Seoul in 1992 where he completed elementary, middle, an d high school, and undergraduate studies. He received his bachelor of engineering degree in chemical engineering from Hanyang University, Korea. After undergraduate, he worked at Fu jifilm Korea for one year. In August 2008 he was admitted to the graduate school of the University of Florida to pursue a masters degree in the agricultural and bi ological engineer ing department.