Karger-Kocsis, Fakirov Nano- and Micromechanics of Polymer Blends and Composites József Karger-Kocsis Stoyko Fakirov Nano- and Micro- mechanics of Polymer Blends and Composites Hanser Publishers, Munich Hanser Publications, Cincinnati The Editors: Prof. Dr.-Ing. József Karger-Kocsis, Department of Polymer Engineering, Faculty of Mechanical Engineering, Budapest University of Technology and Economics, 1111 Budapest, Hungary Prof. Stoyko Fakirov, Ph.D., The University of Auckland, Department of Mechanical Engineering, Private bag 92019, Auckland, New Zealand Distributed in the USA and in Canada by Hanser Publications 6915 Valley Avenue, Cincinnati, Ohio 45244-3029, USA Fax: (513) 527-8801 Phone: (513) 527-8896 or 1-800-950-8977 www.hanserpublications.com Distributed in all other countries by Carl Hanser Verlag Postfach 86 04 20, 81631 München, Germany Fax: +49 (89) 98 48 09 www.hanser.de The use of general descriptive names, trademarks, etc., in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone. While the advice and information in this book are believed to be true and accurate at the date of going to press, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein. Library of Congress Cataloging-in-Publication Data Nano- and micromechanics of polymer blends and composites / edited by Jszsef Karger-Kocsis, and Stoyko Fakirov. p. cm. Includes bibliographical references. Summary: „The aim of this book is to give a state-of-art overview on aspects of micro- and nanomechanics of polymers, polymeric blends and composites“--Provided by publisher. ISBN 978-1-56990-435-0 1. Polymeric composites--Mechanical properties. 2. Micromechanics. 3. Microstructure. 4. Nanostructured materials. I. Fakirov, Stoyko. II. Karger-Kocsis, J. (Jszsef) TA455.P58N355 2009 620.1‘920423--dc22 2009010703 Bibliografische Information Der Deutschen Bibliothek Die Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über <http://dnb.d-nb.de> abrufbar. ISBN 978-3-446-41323-8 All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying or by any information storage and retrieval system, without permission in wirting from the publisher. © Carl Hanser Verlag, Munich 2009 Production Management: Steffen Jörg Coverconcept: Marc Müller-Bremer, Rebranding, München, Germany Coverdesign: Stephan Rönigk Printed and bound by Druckhaus “Thomas Müntzer” GmbH, Bad Langensalz Printed in Germany Preface The deduction of structure-property relationships is a major target of materials scientists. Unfortunately, these relationships are hardly ever universal, but mostly of specific nature. On the one hand, this is due to the fact that there is no correlation between the structural units in different materials, such as metals, ceramics and polymers. On the other hand, the materials have a very complex structural build-up, the constituents of which are strongly interrelated. This note holds especially for polymers. Depending on the size of the volume elements which contain all structural “inhomogeneities” in a way that via their combination the related material can be treated as “homogenous” (representative volume element concept), one may distinguish between macro-, micro- and nanocomposites. The size of the represen- tative volume element in macrocomposites is in the range of millimeters and above. Such polymer macrocomposites, as those with various textile architecture (woven, braided), resin infiltrated open cell metallic and ceramic foams etc., are beyond the scope of this book. The term polymer microcomposite covers very different systems, accepting the definition that at least one dimension of the constituents is in the micrometer range. So, unidirectional aligned carbon (diameter 6–7 μm) or glass (diameter 10–15 μm) fiber reinforced composites, neat polymers with injection molding-induced skin-core structure (oriented skin layer thickness is usually less then 200 μm), polymer blends and reinforced/filled polymers having microscale inclusions (at least in one dimension again!) – all belong to this category. In the case of nanocomposites, at least one dimension of the constituents should be on the nanoscale (such as clay or carbon nanotubes). As mentioned above, the structure of polymers may be very complex and multiscaled. For example, fiber-reinforced microcomposites with a nanomodified matrix or semi- crystalline polymers themselves (just consider the mean sizes of spherulites and crystalline lamellae) are on the borderline between micro- and nanocomposites. This may be the reason why polymer scientists often use the term morphology instead of micro- and nano-scale structures for neat polymers. The structural elements of one-component multiphase systems (homopolymers and copolymers) are in the same size-range as nano- and micro-sized additives and reinforcements of the multicomponent systems (blends and composites). This fact makes possible the application of the same characterization techniques and modeling approaches to these rather different, from material point of view, systems. What is more, the structural elements in the homopolymers and copoly- mers as well as the constituents of the blends and composites are distinguished by their individual mechanical characteristics and each of them makes its own contribution to the overall mechanical behavior of the whole system. At the same time, multicomponent systems, as a rule, can be considered multiphase systems as well. Only in rare cases, when a particular property obeys the additivity law, the complex system can be easily predicted with respect of this property. In the rest of the cases, empirical approaches and modeling have to be applied for the deduction of structure-properties relationships. With the appearance of polymeric nanocomposites, the structural build-up of polymeric materials, including polymeric microcomposites, has become even more complex. This has forced the researchers to check whether or not the know- ledge acquired with traditional microcomposites can be transferred to nanocom- posites, produced by different methods. As the reader will notice, this is sometimes the case for structural polymeric micro- and nanocomposites. On the other hand, polymer nanocomposites may show peculiar properties that are not present, not even in analogy, in microcomposites. To find the cause of such behavior is a very challenging task, which requires a multiscale approach. The latter covers in-depth structural investigations as well as molecular modeling using different approaches and techniques. Our aim with this book is to demonstrate that the multiscale approach is the right tool for a deeper understanding of the structure-property relationships in polymeric micro- and nanocomposites. The term “mechanics” in the title is foreseen to demonstrate that emphasis has been put on structural instead of func- tional composites. Note that the mechanical behavior of structural composites is of great practical relevance and the driving force of their development now- adays. The book contributions are grouped in 5 sections. Part I is devoted to polymers (Galeski and Regnier and Ginzburg et al.). Part II highlights selected aspects of composite production (Zhang et al., Bokobza, and Bhattacharyya and Fakirov). Part III considers interphase aspects (Kalfus and Jancar). Part IV gives an overview of characterization methods and properties, including in situ deforma- tion (Stribeck), creep and fatigue (Pegoretti), deformation and fracture properties (Tjong, Dasari et al. and Karger-Kocsis), and hardness (Fakirov). The book ends with Part V dealing with modeling of rubber and polymer nanocomposites (Mark et al. and Spencer and Sweeney). Our intention was to cover all kinds of polymeric materials, viz. thermoplas- tics, thermosets, and rubbers, including their different types and combinations. We are thankful to our contributors for their high quality chapters and their timely delivery. We strongly hope that you, the readers, will find this book useful for your work. A.m.D.g., March, 2009 József Karger-Kocsis Budapest, Kaiserslautern, Pretoria, Stoyko Fakirov Auckland Content PART I POLYMERS Chapter 1 Nano- and Micromechanics of Crystalline Polymers A. Galeski, G. Regnier 1.1. Introduction..........................................................................................3 1.2. Tensile deformation of crystalline polymers...........................................4 1.3. Cavitation in tensile deformation..........................................................4 1.4. Tensile deformation of polyethylene and polypropylene........................8 1.5. Deformation micromechanisms in crystalline polymers........................13 1.6. Molecular mechanisms at a nanometer scale.......................................16 1.7. Dislocations in crystal plasticity..........................................................23 1.8. Generation of dislocations...................................................................25 1.9. Competition between crystal plasticity and cavitation........................34 1.10. Micromechanics modeling in semicrystalline polymers.........................35 1.10.1. Microstructure and mechanical properties...................................35 1.10.2. The micromechanical models.......................................................36 1.10.3. Idealizing the microstructure of semicrystalline polymers ............38 1.10.4. Elastic behavior prediction..........................................................40 1.11. Large deformations and bottlenecks....................................................45 1.12. Phenomenological models of polymer deformation under tensile and compressive stresses ................................................45 1.13. Conclusions.........................................................................................47 References...........................................................................................48 viii Content Chapter 2 Modeling Mechanical Properties of Segmented Polyurethanes V. V. Ginzburg , J. Bicerano, C. P. Christenson, A. K. Schrock, A. Z. Patashinski 2.1. Introduction........................................................................................59 2.2. Predicting Young’s modulus of segmented polyurethanes...................63 2.2.1. Relationship between Young’s modulus and formulation – experimental observations..............................63 2.2.2. Theory ........................................................................................64 2.2.3. Young’s modulus: comparing theory with experiments................72 2.3. Modeling tensile stress-strain behavior................................................76 2.4. Linear viscoelasticity...........................................................................82 2.5. Non-equilibrium factors and their influence on mechanical properties 84 2.6. Conclusions and Outlook....................................................................84 Acknowledgment ................................................................................85 References...........................................................................................85 PART II NANOCOMPOSITES: INFLUENCE OF PREPARATION Chapter 3 Nanoparticles/Polymer Composites: Fabrication and Mechanical Properties M. Q. Zhang, M. Z. Rong, W. H. Ruan 3.1. Introduction........................................................................................93 3.2. Dispersion-oriented manufacturing of nanocomposites........................95 3.2.1. Conventional two-step manufacturing ........................................95 3.2.2. Specific two-step manufacturing ............................................... 107 3.2.3. One-step manufacturing............................................................ 118 3.3. Dispersion and filler/matrix interaction-oriented manufacturing of nanocomposites..................................................... 120 3.3.1. Two-step manufacturing in terms of in situ reactive compatibilization....................................................................... 120 3.3.2. One-step manufacturing in terms of in situ graft and crosslinking......................................................................... 124 3.4. Dispersion, filler/filler interaction and filler/matrix interaction-oriented manufacturing of nanocomposites..................... 129 3.5. Conclusions....................................................................................... 135 Acknowledgements ........................................................................... 136 References......................................................................................... 136 Content ix Chapter 4 Rubber Nanocomposites: New Developments, New Opportunities L. Bokobza 4.1. Introduction...................................................................................... 141 4.2. General considerations on elastomeric composites............................. 142 4.3. Spherical in situ generated reinforcing particles................................ 144 4.4. Carbon nanotube-filled rubber composites........................................ 153 4.5. Conclusions....................................................................................... 161 References......................................................................................... 162 Chapter 5 Organoclay, Particulate and Nanofibril Reinforced Polymer-Polymer Composites: Manufacturing, Modeling and Applications D. Bhattacharyya, S. Fakirov 5.1. Introduction...................................................................................... 167 5.2. Polypropylene/organoclay nanocomposites: experimental characterisation and modeling .......................................................... 169 5.2.1. Peculiarities of polymer/clay nanocomposites............................ 169 5.2.2. Parametric study and associated properties of PP/organoclay nanocomposites ............................................ 171 5.2.3. Evaluation of the experimental data by means of Taguchi and Pareto ANOVA methods.................................. 174 5.2.4. Materials, manufacturing and characterisation of nanocomposites..................................................................... 178 5.2.5. Analytical models for composites............................................... 179 5.2.6. Comparisons of experimental results with the calculated values 182 5.3. The dispersion problem in the case of polymer-polymer nanocomposites................................................................................. 185 5.3.1. Manufacturing of nanofibrillar polymer-polymer composites..... 187 5.3.2. Nanofibrillar vs. microfibrillar polymer-polymer composites and their peculiarities.............................................. 188 5.4. Directional, thermal and mechanical characterisation of polymer-polymer nanofibrillar composites..................................... 190 5.4.1. Directional state of NFC as revealed by wide-angle X-ray scattering ........................................................................ 190 5.4.2. Thermal characterization of NFC ............................................. 192 5.4.3. Mechanical properties of NFC................................................... 193 5.5. Potentials for application of nanofibrillar composites and the materials developed from neat nanofibrils............................ 196 x Content 5.6. Conclusions and outlook................................................................... 199 Acknowledgments............................................................................. 200 References......................................................................................... 201 PART III NANO- AND MICROCOMPOSITES: INTERPHASE Chapter 6 Viscoelasticity of Amorphous Polymer Nanocomposites with Individual Nanoparticles J. Kalfus 6.1. Introduction...................................................................................... 209 6.2. Brief physics of amorphous polymer matrices.................................... 210 6.2.1. Equilibrium structure of amorphous chains............................... 210 6.2.2. Microscopic relaxation modes and segmental mobility............... 212 6.2.3. Entropy vs. energy driven mechanical response......................... 214 6.3. Basic aspects of amorphous polymer nanocomposites ....................... 216 6.3.1. Structure of surface adsorbed chains......................................... 217 6.3.2. Segmental immobilization of chains in the presence of solid surfaces......................................................................... 219 6.4. Reinforcement of amorphous nanocomposite below and above matrix T ............................................................... 222 g 6.5. Strain induced softening of amorphous polymer nanocomposites...... 228 6.6. Relaxation of chains in the presence of nanoparticles ....................... 233 6.7. Conclusions and outlook................................................................... 235 Acknowledgements ........................................................................... 236 References......................................................................................... 236 Chapter 7 Interphase Phenomena in Polymer Micro- and Nanocomposites J. Jancar 7.1. Introduction...................................................................................... 241 7.2. Micro-scale interphase in polymer composites................................... 246 7.3. Nano-scale interphase ....................................................................... 250 7.4. Chain immobilization on the nano-scale ........................................... 252 7.5. Characteristic length-scale in polymer matrix nanocomposites.......... 255 7.6. Conclusions and outlook................................................................... 257 Acknowledgement............................................................................. 258 References......................................................................................... 258 Content xi PART IV NANO- AND MICROCOMPOSITES: CHARACTERIZATION Chapter 8 Deformation Behavior of Nanocomposites Studied by X-Ray Scattering: Instrumentation and Methodology N. Stribeck 8.1. Introduction...................................................................................... 269 8.2. Scattering theory and materials structure......................................... 272 8.2.1. Relation between a CDF and IDFs........................................... 275 8.3. Analysis options derived from scattering theory................................ 276 8.3.1. Completeness – a preliminary note............................................ 276 8.3.2. Analysis options ........................................................................ 276 8.3.3. Parameters, functions and operations ....................................... 277 8.4. The experiment................................................................................. 278 8.4.1. Principal design......................................................................... 278 8.4.2. Engineering solutions ................................................................ 279 8.4.3. Scattering data and its evaluation............................................. 284 8.5. Techniques: Dynamic vs. stretch-hold............................................... 286 8.6. Advanced goal: Identification of mechanisms.................................... 286 8.7. Observed promising effects from stretch-hold experiments................ 289 8.7.1. Orientation of nanofibrils in highly oriented polymer blends by means of USAXS......................................... 289 8.7.2. USAXS studies on undrawn and highly drawn PP/PET blends........................................................................ 291 8.8. Choosing experiments....................................................................... 293 8.8.1. Experiments with a macrobeam................................................ 293 8.8.2. Experiments with a microbeam................................................. 294 8.9. Conclusion and outlook .................................................................... 295 References......................................................................................... 296 Chapter 9 Creep and Fatigue Behavior of Polymer Nanocomposites A. Pegoretti 9.1. Introduction...................................................................................... 301 9.2. Generalities on the creep behavior of viscoelastic materials............... 302 9.3. Generalities on the fatigue resistance of polymeric materials............. 306 9.4. Creep behavior of polymer nanocomposites ...................................... 309 9.4.1. Creep response of PNCs containing one-dimensional nanofillers........................................................ 309