Polypropylene - An a to Z Reference

Polypropylene An A-Z reference

Edited by

J. Karger-Kocsis Institute for Composite Materials Ltd. University of Kaiserslau tern Germany

and

Technical University of Budapest Hungary

KLUWER ACADEMIC PUBLISHERS DORDRECHT / BOSTON / LONDON

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ISBN 0 412 80200 7

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List of contributors

Abdellah Ajji Industrial Materials Institute, National Research Council Canada, 75 Boulevard de Mortagne, Boucherville, Qukbec, J4B 6Y4, Canada

S. Al-Malaika Polymer Processing and Performance Group, Department of Chemical Engineering and Applied Chemistry, Aston University, Aston Triangle, Birmingham B4 7ET, UK

Erik Andreassen SINTEF Materials Technology, PO Box 124 Blindern, N-0314 Oslo, Norway

Gyorgy BBnhegyi Furukawa Electric Institute of Technology, H-1158 Budapest, K6smBrk u. 24-28, Hungary

G. Bechtold Institut f i r Verbundwerkstoff e GmbH, University of Kaiserslautern, D-67663 Kaiserslautern, Germany

J. Bentham Borealis Deutschland GmbH, Morsenbroicher Weg 200, D-40474 Wsseldorf, Germany

K. Bernreiter PCD Polymere GmbH, PO Box 675, A-4021 Linz, Austria

Michael J. Bevis Wolfson Centre for Materials Processing, Department of Materials Engineering, Brunel University, Uxbridge, Middlesex UB8 3PH, UK

D. Bhattacharyya Composites Research Group, Department of Mechanical Engineering, University of Auckland, Private Bag 92019, Aukland, New Zealand

Eric Bond Materials Science and Engineering, College of Engineering, University of Tennessee, Knoxville, Tennessee 37996-2200, USA

X List of contributors

P.-E. Bourban Laboratoire de Technologie des Composites et PolymPres, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland Serge Bourbigot Laboratoire de Chimie Analytique et de Physico-Chimie des Solides, Ecole Nationale Superieure de Chimie de Lille, Universitk des Sciences et Technologies de Lille, BP 108, E59652 Villeneuve dAscq Cedex, France C. Brockmann Institut fiir Kunststoffverarbeitung, RWTH Aachen, Pontstr. 49, D-52056 Aachen, Germany W. Brockmann Werkstoff- und Oberflachentechnik, Universitat Kaiserslautern, D-67663 Kaiserslautern, Germany Witold Brostow Department of Materials Science, University of North Texas, Denton,

S. Bruckner Dipartimento di Scienze e Tecnolgie Chimiche, University degli Studi di Udine, 1-33100 Udine, Italy A. Brunswick Institut fur Kunststoffverarbeitung, RWTH Aachen, Pontstr. 49, D-52062 Aachen, Germany H. Bucka PCD Polymere GmbH, PO Box 675, A-4021 Linz, Austria A. Cervenka Manchester Materials Science Centre, University of Manchester and UMIST, Grosvenor Street, Manchester, M1 7 H S , UK Chi-Ming Chan Department of Chemical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong PR China Kwong Chan Institutes of Textiles and Clothing, Hong Kong Polytechnic University, Yuk Choi Road, Kowloon, Hong Kong PR China R. Chatten Department of Materials Engineering, Brunel University, Uxbridge, Middlesex, UB8 3PH, UK I. Chod6k Polymer Institute, Slovak Academy of Sciences, SK-842 36 Bratislava, Slovakia

TX 76203-5310, USA


G.R. Christie Composites Research Group, Department of Mechanical Engineering, University of Auckland, Private Bag 92019, Auckland, New Zealand

K.C. Cole Industrial Materials Institute, National Research Council Canada, 75 Boulevard de Mortagne, Boucherville, Quebec, J4B 6Y4, Canada

J.-L. Costa Solvay Polyolefins Europe-Belgium, Rue de Ransbeek 310, B-1120 Brussels, Belgium

xi

T. Czvikovszky Department of Polymer Engineering and Textile Technology, Faculty of Mechanical Engineering, Technical University of Budapest, H-1111 Budapest, Hungary

A. Dehn Institut fiir Verbundwerkstoffe GmbH, Universitat of Kaiserslautern, D-67663 Kaiserslautern, Germany

Rene Delobel Laboratoire de Chimie Analytique et de Physico-Chimie des Solides, Ecole Nationale Superieure de Chimie de Lille, Universitk des Sciences et Technologies de Lille, BP 108, F-59652 Villeneuve dAscq Cedex, France

R. Denzer Institut fin Verbundwerkstoffe GmbH, Universitat of Kaiserslautern, D- 67663 Kaiserslautern, Germany

B.L. Deopura Textile Technology Department, Indian Institute of Technology, New Delhi 110016, India

M.M. Dumoulin ADS Composites Group, 275 North, Monfette Street, Thetford Mines, Quebec, G6G 7H4, Canada

Gottfried W. Ehrenstein Lehrstuhl fur Kunststofftechnik, Universitat Erlangen-Nurnberg, Am Weichselgarten 9, D-91058 Erlangen-Tennenlohe, Germany

P. Eyerer Institut fiir Polymer Testing (IKP), University of Stuttgart, Pfaffelwaldring 32, D-70569 Stuttgart, Germany

J. Fiebig PCD Polymere GmbH, PO Box 675, A-4021 Linz, Austria

xii List of contributors

B. Fisa Centre de recherche appliquee sur les polymPres (CRASP), &ole Polytechnique de Montreal, PO Box 6079, Station Centre Ville, Montreal, Quebec H3C 3A7, Canada

K. Friedrich Institut fur Verbundwerkstoffe GmbH, Universitat of Kaiserslautern, D-67663 Kaiserslautern, Germany

Mitsuyoshi Fujiyama Plastics Research Laboratory, Tokuyama Company, Tokuyama City, Yamaguchi 745, Japan

M. Gahleitner PCD Polymere AG, PO Box 675, A-4021 Linz, Austria

A. Galeski Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, PL-90 363 Lodz, Poland

William J. Gauthier Research and Technology Center, Fina Oil and Chemical Company, PO Box 1200, Deer Park, Texas 77536, USA

G.P. Guidetti Monte11 Polyolefins, G. Natta Research Centre, P. le Donegani 12, 1-44100 Ferrara, Italy

Archie E. Hamielec Department of Chemical Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada

K. Hammerschmid PCD Polymere GmbH, PO Box 675, A-4021 Linz, Austria

Eddy W. Hansen SINTEF Materials Technology, PO Box 124 Blindern, N-0314 Oslo 3, Norway

E. Harkin-Jones Department of Chemical Engineering, The Queens University of Belfast, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ire 1 and

T. Harmia Institut fur Verbundwerkstoffe GmbH, Erwin-Schrodinger-Str. 58, D-67663 Kaiserslautern, Germany D.R. Hartman Owens-Corning Science and Technology Center, 2790 Columbus Road, Route 16, Granville, Ohio 43023-1200, USA

List of contributors Markku T. Heino NK Cables Ltd, PO Box 419, FIN-00101 Helsinki, Finland

xiii

Pavol Hodul Department of Fibres and Textile Chemistry, Faculty of Chemical Technology, Slovak University of Technology, Radlinskkho 9, SK-812 37 Bratislava, Slovak Republic

J.A. Horas Instituto de Matematica Aplicada San Luis, Departamento de Fisica, Facultad de Ciencias Fisico Matematicas y Naturales, Universidad Nacional de San Luis, Ejercito de 10s Andes 950, 5700 San Luis, Argentina

Martin Jambrich Department of Fibres and Textile Chemistry, Faculty of Chemical Technology, Slovak University of Technology, Radlinskkho 9, SK-812 37 Bratislava, Slovak Republic

Just Jansz Monte11 Benelux bv, Westelijke Rondwegl, 4791 RS Klundert, The Netherlands

P.K. Jarvela Tampere University of Technology, Institute of Materials Science and Plastics Technology, PO Box 589, FIN-33101 Tampere, Finland

T.P.A Jarvela Tampere University of Technology, Institute of Materials Science and Plastics Technology, PO Box 589, FIN-33101 Tampere, Finland

Gurhan Kalay Wolfson Centre for Materials Processing, Department of Materials Engineering, Brunel University, Uxbridge, Middlesex UB8 3PH, UK

I. Karacan Zorlu Holding, Korteks, Organize Sanayi Bolgesi, Sari Caddesi NO 3, Bursa, Turkey

J. Karger-Kocsis Institut fiir Verbundwerkstoffe GmbH, Universitat Kaiserslautern, PO Box 3049, D-67653 Kaiserslautern, Germany; Technical University of Budapest, Hungary

S. Kerth BASF AG, ZEW /BB-L443, D-67056 Ludwigshafen, Germany

R. J. Koopmans Dow Benelux N.V., PO Box 48, NL-4530 AA Terneuzen, The Netherlands

xiv List of contributors

J. Kressler Fachbereich Werkstoffwissenschaften, Institut fur Werkstoffwissenschaft, Martin-Luther-Universitat Halle-Wittenberg, D-06099 Halle (Saale), Germany

Toshio Kunugi 890 Kitamiyaji, Kamiyama-cho, Nirasaki-shi, 407-0042, Japan

Toshio Kurauchi Toyota Central Research and Development Laboratories Inc., Nagakute- cho, Aichi-gun, Aichi, 480-11, Japan

Francesco Paolo La Mantia Dipartimento di Ingegneria Chimica dei Processi e dei Materiali, Universita di Palermo, Viale delle Scienze, 1-90128 Palermo, Italy

Michel Le Bras Laboratoire de Genie des Procedes dInteractions Fluides Reactifs- Materiaux, Ecole Nationale Superieure de Chimie de Lille, BP 108, F- 59652 Villeneuve dAscq Cedex, France

K. Lederer Institut fiir Chemie der Kunststoffe, Montanuniversitat Leoben, A-8700 Leoben, Austria

H. Ledwinka PCD Polymere GmbH, PO Box 675, A-4021 Linz, Austria

N. Legros Industrial Materials Institute, National Research Council Canada, 75 Boulevard de Mortagne, Boucherville, Qukbec, J4B 6Y4, Canada

David J. Lohse Exxon Research and Engineering Co., Route 22 East, Annandale, New Jersey 08801, USA

Bernard Lotz Institut Charles Sadron, 6 rue Boussingault, E67083 Strasbourg Cedex, France

A. Luciani Industrial Materials Institute, National Research Council Canada, 75 Boulevard de Mortagne, Boucherville, Qukbec J4B 6Y4, Canada; &ole Polytechnique Fkdkrale de Lausanne, Laboratoires de Technologie des Composites et Polym&res, LTC-DMX-EPFL, CH-1015 Lausanne, Switzerland

A. Lutz Institut fur Verbundwerkstoffe GmbH, Erwin-Schrodinger-Str. 58, D-67663 Kaiserslautern, Germany

List of contributors xv N.J. Macauley Department of Chemical Engineering, The Queen's University of Belfast, Belfast BT7 lNN, Northern Ireland J.H. Magill Department of Materials Science and Engineering, School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA M. Maier Institut fur Verbundwerkstoffe GmbH, Universitat Kaiserslautern, D-67663 Kaiserslautern, Germany J.-A E. M" anson Laboratoire de Technologie des Composites et PolymPres, Ecole Polytechnique FPderale de Lausanne, CH-1015 Lausanne, Switzerland Anton Marcinein Department of Fibres and Textile Chemistry, Faculty of Chemical Technology, Slovak University of Technology, Radlinskeho 9, SK-812 37 Bratislava, Slovak Republic T.A. Martin Composites Research Group, Department of Mechanical Engineering, University of Auckland, Private Bag 92019, Auckland, New Zealand T. Matsuoka Polymer Processing Laboratory, Toyota Central Research and Development Laboratories Inc., Nagakute-cho, Aichi-gun, Aichi-ken 480-1192, Japan W. John G. McCulloch J&M Laboratories, 12 J&M Drive, Dawsonville, GA 30534, USA A. Meddad Centre de recherche appliquee sur les polymgres (CRASP), ho le Polytechnique de Montreal, PO Box 6079, Station Centre Ville, Montreal, Quebec H3C 3A7, Canada S.V. Meille Dipartimento di Chimica, Politecnico di Milano, Via Mancinelli 7-20131 Milano, Italy D. Meyer Hohenstaufenstr. 11, D-73349 Wiesensteig, Germany W. Michaeli Institut fiir Kunststoffverarbeitug, RWTH Aachen, Pontstr. 49, D-52062 Aachen, Germany G.H. Michler Institut fiir Werkstoffwissenschaft, Martin-Luther-Universitat Halle- Wittenberg, Geusaer Str., D-06217 Merseburg, Germany

xvi List of contributors

Klaus-Peter Mieck Thuringisches Institut fur Textil- und Kunststoff-Forschung e.V., D-07407 Rudolstadt-Schwarza, Germany Yukio Mizutani Tokuyama Corp., Fujisawa Research Laboratory, 2023-1 Endo, Fujisawa City, Kanagawa 252, Japan F. Moller Institut fur Verbundwerkstoffe GmbH, Universitat Kaiserslautern, D-67663 Kaiserslautern, Germany R. Mulhaupt Freiburger Materialforschungzentmm und Institut fur Makromolekulare Chemie der Albert-Ludwigs-Universitat Freiburg, Stefan-Meier-Str. 31, D-79104 Freiburg, Germany W.R. Murphy Department of Chemical Engineering, The Queens University of Belfast, Belfast BT7 lNN, Northern Ireland Ikuo Narisawa Materials Science and Engineering, Yamagata University, Yonezawa, Yamagata 992, Japan I. Naundorf ITT Cannon GmbH, Cannostr. D-71384 Weinstadt, Germany W. NeiiSl PCD Polymere GmbH, PO Box 675, A-4021 Linz, Austria I. Novak Polymer Institute, Slovak Academy of Sciences, SK-842 36 Bratislava, Slovakia U. Panzer PCD Polymere GmbH, PO Box 675, A-4021 Linz, Austria B. Pietsch Ciba Specialty Chemicals Inc., PO Box, CH-4002 Basel, Switzerland Bela Pukanszky Department of Plastics and Rubber Technology, Technical University of Budapest, PO Box 92, H-1521 Budapest, Hungary; Central Research Institute for Chemistry, Hungarian Academy of Sciences, PO Box 17, H-1525 Budapest, Hungary M. Ratzsch PCD Polymere GmbH, PO Box 675, A-4021 Linz, Austria Keith Redford SINTEF Materials Technology, PO Box 124 Blindern, N-0314 Oslo 3, Norway

List of contributors xvii G.L. Rigosi Monte11 Polyolefins, G. Natta Research Centre, P. le Donegani 12, 1-44100 Ferrara, Italy M.G. Rizzotto Instituto de Matematica Aplicada San Luis, Departamento de Fisica, Facultad de Ciencias Fisico Matematicas y Naturales, Universidad Nacional de San Luis, Ejercito de 10s Andes 950, 5700 San Luis, Argentina

Norio Sat0 Toyota Central Research and Development Laboratories Inc., Nagakute- cho, Aichi-gun, Aichi, 480-11, Japan K. Schafer Barmag AG, PO Box 11 02 40, D-42862 Remscheid, Germany M.J. Schneider Freiburger Materialforschungzentrum und Institut f i r Makromolekulare Chemie der Albert-Ludwigs-Universitat Freiburg, Stefan-Meier-Str. 21, D-79104 Freiburg, Germany Jukka V. Seppal Nokia Cables, PO Box 419, HN-00101 Helsinki, Finland T.J. Shields Fire SERT Centre, University of Ulster, 75 Belfast Road, Carrickfergus, Co. Antrim BT38 8PH, Northern Ireland JoBo B.P. Soares Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada J.E. Spruiell Materials Science and Engineering, College of Engineering, University of Tennessee, Knoxville, Tennessee 37996-2200, USA M. Steiner Institut fur Verbundwerkstoffe GmbH, Universitat Kaiserslautern, Erwin-Schrodinger-Str. 58, D-67663 Kaiserslautern, Germany Tomasz Sterzynski Department Polymeres-ECPM, UniversiM Louis Pasteur Strasbourg I, 4 rue Boussingault, F-6700 Strasbourg, France; Poznan University of Technology, Institute of Chemical Technology, PL-60-965 Poznan, Poland J. Suhm Freiburger Materialforschungzentrum und Institut fiir Makromolekulare Chemie der Albert-Ludwigs-Universitat Freiburg, Stefan-Meier-Str. 21, D-79104 Freiburg, Germany

xviii List of contributors

Hidero Takahashi Toyota Central Research and Development Laboratories Inc., Nagakute- cho, Aichi-gun, Aichi, 480-11, Japan

Conchita V. Tran Union Carbide (Europe) SA, 7 Rue du Pre-Bouvier, CH-1217 Meyrin, Switzerland

J.L. Thomason Owens-Corning Science and Technology Center, 2790 Columbus Road, Route 16, Granville, Ohio 43023-1200, USA

J. Ulcej Extrusion Dies Inc., 911 Kurth Road, Chippewa Falls, Wisconsin 54729-1443, USA

L.A. Utracki Industrial Materials Institute, National Research Council Canada, 75 Boulevard de Mortagne, Boucherville, Quebec J4B 6Y4, Canada

G.J. Vancso Materials Science and Technology of Polymers, Faculty of Chemical Technology, University of Twente, PO Box 217, NL-7500 AE Enschede, The Netherlands

J6zsef Varga Department of Plastics and Rubber Technology, Technical University of Budapest, PO Box 92, H-1521 Budapest, Hungary; Lehrstuhl fur Kunststofftechnik, Universitat Erlangen-Nurnberg, Am Weichselgarten 9, D-91058 Erlangen-Tennenlohe, Germany

D. Vesely Department of Materials Engineering, Brunel University, Uxbridge, Middlesex, UB8 3PH, UK

M.H. Wagner Institut fur Kunststofftechnologie der Universitat Stuttgart, Boblinger Str. 70, D-70199 Stuttgart, Germany

Michael Wehmann J&M Laboratories, Kolpingstr. 34a, D-63150 Heusenstamm, Germany

J.R. White Department of Mechanical, Materials and Manufacturing Engineering, University of Newcastle, Newcastle upon Tyne NE1 7RU, UK

Jean Claude Wittmann Institut Charles Sadron, 6 rue Boussingault, F-67083 Strasbourg Cedex, France

List of contributors xix

M. Xanthos Polymer Processing Institute at Stevens Institute of Technology, Castle Point on Hudson, Hoboken, New Jersey 07030, USA; Department of Chemical Engineering, Chemistry and Environmental Science, New Jersey Institute of Technology, University Heights, Newark, New Jersey NJ 07102, USA

J. Zhang Fire Research Centre, University of Ulster at Jordanstown, Carrickfergus, Co. Antrim BT38 8PH, Northern Ireland

Preface

My heart sank when I was approached by Dr Hastings and by Professor Briggs (Senior Editor of Materials Science and Technology and Series Editor of Polymer Science and Technology Series at Chapman & Hall, respectively) to edit a book with the provisional title Handbook of Poly- propyIene. My reluctance was due to the fact that my former book 111 along with that of Moore [21, issued in the meantime, seemed to cover the information demand on polypropylene and related systems. Encour- aged, however, by some colleagues (the new generation of scientists and engineers needs a good reference book with easy information retrieval, and the development with metallocene catalysts deserves a new update!), I started on this venture.

Having some experience with polypropylene systems and being aware of the current literature, it was easy to settle the titles for the book chapters and also to select and approach the most suitable potential contributors. Fortunately, many of my first-choice authors accepted the invitation to contribute.

Like all editors of multi-author volumes, I recognize that obtaining contributors follows an S-type curve of asymptotic saturation when the number of willing contributors is plotted as a function of time. The saturation point is, however, never reached and as a consequence, Dear Reader, you will also find some topics of some relevance which are not explicitly treated in this book (but, believe me, I have considered them). On the other hand, I am quite sure that even for those missing themes you will find valuable notes and hints in the many chapters of this book.

During my editing I have had considerable support from some colleagues, whom I want to give credit here: Professor Utracki (CNR, Boucherville, Canada), Dr NeiiJl (PCD, Linz, Austria) and Professor Mulhaupt (FMF, Freiburg, Germany). They ensured the delivery of several chapters by 'persuading' their staff and coworkers to contribute.

xxii Preface

Thanks are, however, due to all contributors for their efficient work. The outcome of all the effort is represented by this book.

The editor wishes to thank David Mackin and the staff at GreenGate Publishing Services for their work in helping to produce the book.

I strongly hope that you, Dear Reader, will be satisfied with it!

A.m.D.g J6zsef Karger-Kocsis Kaiserslautern and Budapest

October, 1997

REFERENCES

1. Karger-Kocsis, J. (ed.) (1995) Polypropylene: Structure, Blends and Composites,

2. Moore, Jr., E.P. (ed.) (1996) Polypropylene Handbook, Hanser, Munich. Vols. 1-3, Chapman & Hall, London.

Con tents


Preface

Adhesive bonding of polypropylene Amorphous or atactic polypropylene Anticorrosion coatings with polypropylene Antistatic and conducting composites of polypropylene Appliances Application of shear-controlled orientation in injection molding

Automation in injection molding Beta-modification of isotactic polypropylene Biaxially oriented polypropylene (BOPP) processes Bumper recycling technology Calendering of polypropylene Commingled yarns and their use for composites Construction principles of injection molds Controlled rheology polypropylene Copolymerization Crash performance of glass fiber reinforced polypropylene tubes Crazing and shear yielding in polypropylene Crosslinking of polypropylene Crystallization Crystallization of syndiotactic polypropylene Designing properties of polypropylene Die swell or extrudate swell Dielectric relaxation and dielectric strength of polypropylene

Dyeing of polypropylene fibers Elastomeric polypropylene homopolymers using metallocene

of isotactic polypropylene

and its composites

catalysts

ix

xxi

1 7

13 20 29

38 47 51 60 68 76 81 90 95

104 116 124 128 135 142 148 158

163 1 72

178

vi Contents

Electron microscopy 186 Elongational viscosity and its meaning for the praxis 198 Environmental stress cracking of polypropylene 206 Epitaxial crystallization of isotactic and syndiotactic polypropylene 215 Extrusion die design guidelines for polypropylene Fatigue performance of polypropylene and related composites Fiber orientation due to processing and its prediction Fillers for polypropylene Fire hazard with polypropylene Flame-retardant polypropylene compositions From quality control to quality assurance in injection molding Gamma-phase of isotactic polypropylene Gas diffusion in and through polypropylene Geotextiles and geomembranes Glass mat reinforced thermoplastic polypropylene Hard-elastic or springy polypropylene High-modulus and high-strength polypropylene fibers and films Impregnation techniques for fiber bundles or tows In-situ reinforced polypropylene blends Industrial polymerization processes Infrared and Raman spectroscopy of polypropylene Injection molding of isotactic polypropylene Injection molding: various techniques Integrated manufacturing

221 227 233 240 247 254 264 267 273 277 284 291 295 301 307 314 320 329 335 341

Interfacial morphology and its effects in polypropylene composites 348 Intumescent fire retardant polypropylene formulations Joining: methods and techniques for polypropylene composites Lamella dimension and distribution Living or plastic hinges Long term properties and lifetime prediction for polypropylene Mathematical modelling of propylene polymerization Mechanical and thermal properties of long glass fiber reinforced

Melt blowing technology Melt fracture or extrudate distortions Melt spinning of polypropylene Melt spinning: technology Metallocene catalyzed polymerization: industrial technology Metallocene catalysis and tailor-made polyolefins Microporous polypropylene films and fibers Miscibility and phase separation in polypropylene blends Modelling and analysis of composites thermoforming Modelling of the compression behavior of polypropylene foams

polypropylene

357 366 374 383 392 399

407 415 421 427 440 446 454 476 484 489 496

Contents Vii

Molecular structure: characterization and related properties of

Morphology and nanostructure of polypropylenes by atomic force

Morphology-mechanical property relationships in injection

Natural fiber/polypropylene composites Nuclear magnetic resonance spectroscopy of polypropylene

Nuclear magnetic resonance spectroscopy of polypropylene

Nucleation Optical clarity of polypropylene products Orientation characterization in polypropylene P-V-T data and their uses Particulate filled polypropylene composites Photostabilizers Pigmentation of polypropylene Polymer blends: fundamentals Polymorphism in crystalline polypropylene Polypropylene blends with commodity resins Polypropylene blends with elastomers Polypropylene blends with engineering and speciality resins Polypropylene foams Polypropylene in automotive applications Polypropylene in cable applications Polypropylene/ continuous glass fibre composite pipes: design

Processing of polypropylene blends Processing-induced morphology Properties of glass fibers for polypropylene reinforcement Pultrusion of glass fiber/ polypropylene composites Reactive compatibilization of polypropylene Recycling of polypropylene Resistance to high-energy radiation Rheology of polypropylene Roll forming of composite sheets Rolltrusion processing of polypropylene for property improvement Size exclusion chromatography Solid-state forming of polypropylene Special polypropylene fibers Spherulitic crystallization and structure Split fiber production Squeeze flow in thermoplastic composites

homo- and copolymers

microscopy

molding

copolymers

homopolymers

principles

503

511

519 527

533

540 545 554 561 569 574 581 591 601 606 615 621 627 635 643 652

658 663 668 678 686 694 701 706 715 721 728 736 744 752 759 769 776

viii Contents

Structure-property relationships in polypropylene fibers 783 Surface modification of polypropylene by additives 790

794 Surface treatment of polypropylene by corona discharge and flame 800 Textile applications of polypropylene fibers 806 Textile polypropylene fibers: fundamentals 813 Thermal antioxidants 821 Thermally stimulated currents of polypropylene and its composites 832 Thermoforming of fiber-reinforced composite sheets 841 Thermofonning of polypropylene 847 Thermoplastic dynamic vulcanizates 853 Warpage and its prediction in injection-molded parts 859 Weathering 866 Weldlines 874 Wood-polypropylene composites 882 X-ray scattering 890 Ziegler-Natta catalysis and propylene polymerization 896

Surface modification of polypropylene by plasmas

Adhesive bonding of -

polypropylene W. Brockmann

INTRODUCTION

Adhesive bonding by definition is the joining of materials with an organic adhesive as an interlayer which adheres on the substrates without macroscopical changing of the material's state.

Adhesion between different materials is created by physical or chemical bonds between the adhesive and the substrate. However, physical or chemical bonds are effective in the nanometer range. As a consequence, good adhesion can only be produced if adhesive and substrate come tight in contact or, in other words, if the adhesive wets the never absolutely flat surface of the substrate as well as possible. Sufficient wetting of a solid substance by a fluid (adhesive) is only possible if the surface energy of the liquid is equal or lower than the surface energy of the substrate [l]. Without discussing details of the theory of adhesion, it must be stated that wetting is a necessary but not sufficient condition for adhesion.

The basic problem of adhesive bonding of polypropylene (PP) is its low surface tension, in the range between 29 and 35 mN/m. An absolute value is not given here, because the surface energy and also the surface state of PP depends, like the surface tension of all materials, on the history of surface creation. Surface energies of adhesives are normally higher than 35mN/m and can go up on to the surface energy of water (72mN/m). As a consequence, normally PP in an untreated state is not wettable by adhesives and in an untreated state not bondable. The only

Polypropylene: An A-Z Reference Edited by J. Karger-Kocsis Published in 1999 by Kluwer Publishers, Dordrecht. ISBN 0 412 80200 7

2 Adhesive bonding of polypropylene

exceptions are pressure-sensitive adhesives, whose properties are dis- cussed later.

If surface energy as an average value is divided into dispersed energy and polar energy, PP shows a very low polar part. The reason for this effect is an absence of polar groups in the molecules of PP and thus a low chemical reactivity of PP surfaces. So principally, on a PP surface in an untreated state (also in the case of wetting by the adhesive), only physical bonds as interactions of very low binding energy are created and as a consequence adhesion between adhesive and substrate is very low.

SURFACE TREATMENT OF POLYPROPYLENE

Three ways exist to create improved adhesional properties of a PP surface.

The first way is a particularly developed roughening method which in the literature [2] is described as creating skeleton which can be trans- lated as whiskerizing. In this process, the PP surface is heated up into the softening area near the melting point. Into this surface, a cotton fabric is pressed and shortly after pressing peeled off from the heated surface in a similar way to the peel ply process used for fiber reinforced plastics. The peel-off process produces an extremely whiskerized PP structure which remains bondable for a very long time. It is assumed that in this type of surface, which can be also created on polyethylene (PE) and other plastic materials, the adhesive adheres by micromechanical interlocking and not by physical or chemical interactions. So far as known, this process is the only roughening technique available for improving adhesional properties of PP. All other methods, such as grit-blasting, grinding or high-pressure water spraying, do not lead to significant improvements of the adhesional properties.

The second type of surface treatment is in principle an improving of the chemical reactivity of the substrates by chemical or physical treatment methods. All the systems known lead to oxidizing effects of the nonpolar substrate and create carbonyl, carboxyl and hydroxyl groups at the surface which are polar and partly chemically reactive. The existence of these groups can be measured for example by Fourier transform infrared (FTIR) spectroscopy using the attenuated total reff exion (ATR) technique.

The oldest treatment is an etching process in highly concentrated chromic-sulfuric acid with a temperature near 80C. Highest adhesional strength between PP and, for example, a two-component epoxy (EP) adhesive is reached after etching times between 120 and 240 s. The recipe of the etching solution is 5078 parts of sulfuric acid (density 1.82g/ml), 120 parts demineralized water and 75 parts potassium dichromate.

Surface treatment of polypropylene 3 Today, such a process is not recommended because the etching solution contains chromium VI ions which are carcinogenic. Beside this fact, the etching process must be followed by very intensive rinsing and drying processes. The effectiveness of the surface treatment, on the other hand, is very good.

The simplest physical treatment of PP is the so called corona treating process (see the chapter 'Surface treatment of polypropylene by corona discharge and flame' in this book). In this case, the PP part is connected with an electrical conductive carrier. At a distance of some millimeters or centimeters over the surface, another electrode is placed and between electrode and electrical conductive carrier a high frequency field (- 6 kV) is produced. In this field, electrical discharge effects occur, the air between electrode and the PP surface is ionized and probably some ozone (0,) is also created. Under these conditions, in times between 2 and 12 s, the surface is oxidized sufficient for good adhesion. Morpho- logical changes of the surface are not observable. The disadvantage of this surface treatment is that only the surface within range of the electrode can be treated.

Another old treatment method for PP is the flaming process. As a standard gas for the burner, a mixture of propane and air with a mixture ratio of 1-20 or a bit higher air content is used. The flame should not burn or melt parts of the surface. The burner should be guided over the surface at a distance of approximately 20mm or more with a velocity of 0.12m/s. Under these conditions with the propane air mixture ratio of 1-20, the best surface properties are produced. Also in this case, the effect is an oxidizing mechanism. With this method only the parts of the surface which are in direct contact with the flame are treated.

Better effects on complicated PP parts are produced by a low-pressure plasma treatment in oxidizing gases, such as oxygen. The disadvantage of the plasma process (pressure 0.01-1 mbar, 10 Mhz, 500 W) is that the plasma chamber after the positioning of the parts must be evacuated and filled with the plasma gas. This process is discontinuous and needs approximately 1.5 min or more for a filled chamber (see also the chapter 'Surface modification of polypropylene by plasma' in this book).

Beside this plasma treatment in a chamber, some variations of plasma treatments using a plasma burner as in a welding process or using a plasma gun are known and described in [2].

Further surface treatment methods for PP such as fluorination exist and will be developed in the future.

The third way of improving the adhesional properties of polypropylene is a coating process. It is called SAC0 process. In a first stage, the surface is roughened by a grit blasting process using corundum as grit blasting material. In a second step, a grit blasting process is used with silicate coated corundum. From this silicate layer on top of the


alumina, some parts adhere to the PP surface very strongly. The binding mechanism of these silicate parts on the polypropylene surface is not well known. In a following step, this silicated PP is coated with a reactive silane as adhesion promoter and on this silanized surface a very good adhesion to adhesives can be achieved. The process is relatively complicated but very efficient. Normally, it is used to treat small parts.

In summary, it can be stated that a large number of different surface treatments exist to improve the adhesional properties of PI? It should be stated here that some manufacturers of cyanoacrylate adhesives recom- mend special chemical primers which produce adhesion on PP without other treatment. In the experience of the author, this type of primer improves the adhesion but produces bonded joints that are insufficiently durable, especially under humid environmental conditions.

ADHESIVES FOR POLYPROPYLENE

In principle, all physical and chemical curing or hardening types of adhesives, such as contact adhesives, hot melts, acrylics, epoxies, poly- urethanes, etc., can be used to join PP in a pretreated state without problems.

One exception of this statement must be noted. These are the so-called pressure-sensitive adhesives which are normally liquids of very high viscosity which do not cure and which are in some cases poorly cross- linked. They adhere on different substrates only by physical bonds and due to the high mobility of their molecules they can 'repair' destroyed bonds in time. This type of adhesion which is called 'dynamic adhesion' meaning a 'centipoid effect' is unique for this class of adhesives and can be used partly on untreated PP for nonstructural bonds. The adhesion between the pressure-sensitive adhesive and the PP surface in an untreated state is not very high but relatively unproblematic.

STRENGTH AND DURABILITY OF BONDED POLYPROPYLENE JOINTS

The strength of bonded PP joints can be measured in accordance with the well-known testing standards such as, for example, DIN 53281, 53282, 53383 or 53289. In some cases, the thickness of the adherends should be different from that used on normal metal parts because the strength of PP is lower. For example, in the case of shear tests with single overlapped joints, the thickness of the PP parts should be 4 mm or more. Also the aging conditions can be in accordance with standards such as DIN 53286 or ASDM B117 (salt spray test). Typical test methods for bonded

Strength and durability of bonded polypropylene joints 5

Table 1 Tensile shear strength of single overlapped PP joints

Adherent thickness: 4 mm Overlap length: 10 mm Glue line thickness: 0.2 mm Surface treatment: Adhesive: 2 component epoxy (Metallon PA) Initial shear strength 1.4 N/mm2 Shear strength after 1200 h 40/95: 1.2 N/mm2

Adhesive: 2 components polyurethane (scotch

Initial shear strength: 2.1 N/mm2 Shear strength after 1200 h 40/95: 2.1 N/mm2 Shear strength after 5000 h nat. c1.t: 2.2 N/mm2

40/95: artificial climate, 40C and 95% rel. hum. tnat.cl.: natural climate in North Germany

etched in chromic sulfuric acid

weld 35 32)

joints in general are described in [3]. They all can be used in a modified or nonmodified mode for testing bonded PP joints.

A general problem with bonded joints is the moderate durability, particularly in humid environments. This is less pronounced for adhesive bonded PP joints if the surfaces of the substrates are treated accordingly. Table 1 gives some strength values measured with PP joints prepared by using epoxy and polyurethane adhesives (both two- component cold curing systems) respectively. Table 1 lists the initial and the residual strength after different aging procedures. The results show that sensitivity against humidity does not exist.

Other investigations [21, with aging times of 22 and 3 years under different artificial and natural conditions, show that on the PP side of bonded joints (in that case, PP steel joints) no remarkable changes in the adhesional area occur. So it can be stated that the durability of adhesive bonding of PP is no problem when the surface of the PP is treated as mentioned earlier.

In summary, adhesive bonding of PP is not a particular problem and the design of bonded joints of this material can follow the recommendations given, for example, in [2, 31. Compared with other joining techniques, such as welding, the advantage of bonding technology is the possibility of joining PP with practically all other materials and creating large joining areas without problems (for example, in sandwich systems, which are gas and watertight and, what is of importance, are free of residual stresses or stress concentrations which can produce problems in design of parts made of thermoplastic polymers). The only problem of bonded joints is that they are difficult to separate and difficult to repair.


REFERENCES 1. Brockmann, W. (1978) Das Kleben chemisch bestandiger Kunststoffe Adkasion 22,

2. Brockmann, W., Dorn, L. and Kaufer, H. (1989) Kleben von Kunststoff mit Metall,

3. Habenicht, G. (1997) Kleben, 3rd edn, Springer-Verlag, Berlin.

3844, 80-86, 100-103.

Springer-Verlag, Berlin.

Keywords: adhesion, adhesive bonding, surface treatment, corona treatment, flame treatment, chemical etching, surface tension, plasma treatment, pressure-sensitive adhesive, adhesive bond strength, adhesive bond durability.

Amorphous or atactic polypropylene J6zsef Karger- Kocs is

INTRODUCTION

Amorphous polypropylene (aPP) is characterized by a random steric orientation of the methyl pendant groups on the tertiary carbon atoms along the molecular chain. The random sequence of these methyl sub- stituents is linked to an atactic configuration. Due to its fully amorphous nature, aPP is easy soluble (even at ambient temperatures) in a great number of aliphatic and aromatic hydrocarbons, esters and other sol- vents in contrast to the isotactic PP (iPP) of semicrystalline feature.

PRODUCTION [ 1-21

Until recently, aPP was obtained as a byproduct during polymerization of propylene for iPP. In the early slurry polymerizations processes, the amount of aPP 'coproduced was between 2 and 10 wt.% depending on the iPP grade and Ziegler-Natta catalyst type used (see also the chapter 'Industrial polymerization processes'). The removal of aPP from the kerosene or low boiling hydrocarbon diluents (e.g. hexane, heptane) via evaporation made the related processes rather costly. It should be emphasized here that the aPP obtained by this way was never fully amorphous and atactic, but a mixture of PPs with various tacticity and molecular weight (MW). The characteristics and quality of the aPP grades depend mostly on the target iPP polymerized, including also its sensitivity to some changes in the polymerization process.


8 Amorphous or atactic polypropylene

The second- and higher-generation catalysts with improved stereo- specificity resulted in much smaller aPP yield so that it should not be removed from the iPP products anymore. Due to this development, the aPP grades offered by the iPP producers at that time (e.g. Epolene@ of Eastman, USA; AFAX@ of Hercules, USA; Daplen@ APP of Chemie Linz, Austria; Vestolen@ APP of Veba, Germany; Tipplen@ APP A, B and C of Tisza Chemical Works, Hungary) disappeared from the market. In the meantime, however, work was undertaken to find useful and cost efficient uses for aPP and, for some of them, aPP became indispensable. As aPP became less available, the markets with successful aPP use created a considerable demand. So, some companies instead of closing older plants converted them to produce aPP as the main product. However, the history of aPP was not completed by aPP turning from a useless byproduct to a desired, well-selling target polymer. A new age of the aPP history is due to recent R&D activities in the field of metallocene- catalyzed polymerization. This revolutionary polymerization technique allows us to produce aPP types of high molecular weight (HMW) being in the range of several hundreds kg/mol. By contrast, the mean MW of the aPP byproducts is one order of magnitude less (few tens kg/mol; Table 1). The increase in the MW is associated with the appearance of new properties, such as rubberlike elasticity.

PROPERTIES

Commercialized byproducts

At ambient temperatures, aPPs are waxy, slightly tacky solids of white or yellowish color. They become softer and more tacky with increasing temperature. The iPP producers recognized early that the commercial success of aPP depends on whether or not their quality is consistent, i.e the properties can be guaranteed within acceptable limits. The easiest way to fulfil this requirement was to select and offer aPP fractions which were extracted from iPP grades produced in larger quantities. For example, the Tipplen APP A, B and C grades of Tisza Chemical Works using the Hercules slurry technology were byproducts of fiber and injection-moldable homopolymers and injection and extrusion moldable iPP block copolymers, respectively. Despite this product philosophy, the properties of the commercialized aPPs had a rather large scatter. The rationale behind this fact was that the quality control including the necessary feedback was tailored for the main iPP and not for the aPP coproduct. As mentioned earlier, the aPP grades are not fully amorphous. Depending on the polymerization and aPP/iPP separation techniques, the crystalIine content of the aPP may reach 15wt.%. The crystalline

00000 t - i - aPP z By-products & - T=l70 "C, f ~ 3 . 2 7 S-'

I - T

9

10000 1 1 1

1 oooo ! 10 20 30 40 50 60 M, [kg/mol]

Figure 1 Melt viscosity (rotation viscosimeter, shear rate: 3.27 s-l) in function of the weight-average molecular weight ( M J for various aPP fractions.

content is generally given by the fraction insoluble in boiling n-heptane (C7). Apart from the crystalline content, other impurities (residual sol- vent, catalyst traces) and additives (e.g. thermooxidative stabilizers) affect the physico-mechanical performance (i.e. flash temperature, softening point, thermal stability) and appearance of the aPP. Due to broad limits on the properties and lacking information on molecular characteristics and crystallinity, general trends in the structure-property relationships are not easy to discern.

Nevertheless, it can be claimed that:

The melt viscosity increases with increasing MW and in addition, strongly depends on the actual shear rate (y) (Figure 1). The softening point (measured usually by the ring and ball method) is very sensitive to the crystalline fraction of the aPP. The tensile strength (lying in the range of 0.2-0.7MPa) is less dependent, the strain (and also other ductility values), however, strongly depends on the MW and crystallinity.

Due to its tacky consistency, aPP is available mostly in block form. In order to reduce the tackiness and blocking properties, spraying by chalk or talc powders or wrapping in silicon-coated papers are widely used. Pelletized, granulated aPP grades are either of highly crystalline nature or compounded, modified grades.

10 Amorphous or atactic polypropylene

Table 1 Properties of aPP grades extracted (byproducts) and synthesized (HMW- aPP)

Property Test Method Unit Commercial Metallocene- or ASTM B yproduct synthesized standard HM W-aPP

Density Shore A hardness Intrinsic viscosity Mw Polydispersity (MJM,) MFl T.s Trn Tensile strength Elongation at break Compression set (RT)

D1505 02240 D2857 GPC GPC

D1238 DSC DSC D638 D638 D395

g ~ r n - ~

dl/g kg/mol

0

dg/min "C "C MPa % %

>0.86 >50 0.4-0.6 20-80 5-7

>500

>140 1000

References 11 The other main application field of aPP is related to its tackiness.

Papers are laminated by roll-coating with aPP-based adhesives. The aPP layer between the papers imparts not only good adhesion but also barrier properties. aPP and related materials can be used to laminate paper to other substrates such as polymer films. aPP may serve also as the basic ingredient of hot-melt adhesives (HMA), even in HMA with some pressure sensitivity.

Many applications are known for aPP in combination with rubbers. aPP has an excellent compatibility with ethylene/propylene and ethylene/ propylene/diene rubbers (EPM and EPDM, respectively). Incorporation of aPP in EPM- or EPDM-based rubber recipes is accompanied with the following advantages:

lowering the Mooney viscosity. This means that less energy is required for mixing the rubber batch; improving the extrudability (including die swell properties - see related chapter Die swell or extrudate swell) and surface appearance of the extrudates; high uptake of inert and reinforcing fillers.

A thermoplastic dynamic vulcanizate (see also the chapter Thermo- plastic dynamic vulcanizates) was also developed by using blends of aPP and EPM,EPDM rubber. The product offered earlier (Tauropren@ of Taurus Hungarian Rubber Works) was recommended for impact tough- ening of iPP [5]. In caulking compounds and sealants, aPP usually replaces butyl rubber (IIR). Other notable applications of aPP are as release agents for concretes, dispersing additives for masterbatches (for pigmentation or machinery cleaning), and viscosity modifier for lubricants, oils, inks.

Interestingly, aPP found less use in blends with thermoplastic polymers irrespective of the high number of related patents. The new generation aPP, produced by metallocene synthesis, may change this scenario (see also the chapter Elastomeric polypropylene homopolymers using metallocene catalysts). Blending of HMW-aPP with polyolefins may result in a new mechanical property profile, e.g. rubberlike resili- ence. Such products may compete with those made of flexible PVC.

The future of aPP and related products seem to depend on the expected breakthrough with the metallocene synthesis.

REFERENCES 1. Liebermann, R.B. and LeNoir, R.T. (1996) Manufacturing, in Polypropylene

Handbook, Chap. 8, (ed. E.P. Moore), Hanser, Munich, pp. 287-301. 2. Resconi, L. and Silvestri, R. (1996) Polypropyleneatactic, in Polymeric Materials

Encyclopedia, Vol. 9, (ed. J.C. Salamone), CRC Press, Boca Raton, FL, USA, pp. 6609-6615.

12 Amorphous or atactic polypropylene 3. Dorrscheidt, W., Hahmann, O., Kehr, H., Nising, W. and Potthoff, P. (1976)

Polyolefine, Kunststoffe-German Plastics, 66, 567-574. 4. von Bramer, P.T. (1975) Amorphous polypropylene. Its properties and uses,

Adhesives Age, July, 15-20. 5. Karger-Kocsis, J., Kozma, B. and Schober, M. (1985) Tauroprene - a new

versatile polyolefinic thermoplastic rubber. Kautschuk Gummi Kunststoffe 38, 614-616.

Keywords: amorphous polypropylene (aPP), atactic polypropylene (aPP), additives, hot-melt adhesive, rubber extender, bitumen modifier, metallocene synthesis, molecular weight, properties of aPP, applications of aPP, thermoplastic dynamic vulcanizate (TDV).

Anticorrosion coatings with polypropylene G.L. Rigosi and G.P. Guidetti

Polypropylene (PPI is utilized as protective coating against corrosion using mainly two technologies: application of powder and extrusion.

APPLICATION OF POWDER

A PP copolymer, modified with grafted polar groups, is used having a high melt flow rate (50-100dg/min according to ASTM D 1238 conditions L at 230"C, 2.16 kg) in order to obtain a good flow of the melted material during the application process. This PP grade is ground at low temperature using cryogenic mills, obtaining a particle size generally less than 300 pm.

The powder is sprayed on the cleaned metal surface by means of electrostatic guns and then the item is placed in an oven at a temperature of about 200C to melt the powder. With this technology, coating thickness in the range of 100-200pm can be obtained. In some cases, epoxy primers are used as a first layer to enhance the adhesion properties.

Alternatively, the metallic item can be heated up in an oven and then dipped in a fluidized bed of modified PP powder; a post-heating step may be included. With the fluidized bed process a coating of 200-600 pm can be applied. The main coating properties are reported in Table 1. As an example of this technology, PP powder is used to coat drums internally, allowing the safe transport of most chemical and foodstuff products.

Polypropylene: An A-Z Refevence Edited by J. Karger-Kocsis Published in 1999 by Kluwer Publishers, Dordrecht. ISBN 0 412 80200 7

14 Anticovvosion coatings with polypropylene

Table 1 Properties of the powder applied coating (epoxy primer and polypropylene) of 0.5 mm of total thickness

Property Method Conditions Value

Cathodic disbonding NF A 49 711 -1.5 V, 3% NaC1, 23"C, 28 220 mm2

Hot water test ASTM D 870 95"C, 1000 h, 5.8 g/1 NaCl 4 mm Penetration resistance

days

0.05 mm 10 N/mm*, 24 h, 23C 90C 0.17 mm 110C 0.4 mm

NF A 49 711

Impact resistance NF A 49 711 25.4 mm, 10 KV 8 Nm

In the near future a large number of applications are expected to use PP powder coating. This is because of the good mechanical properties, improved adhesion, good barrier effect, excellent resistance to most of the inorganic and organic chemical reagents even at high temperature and relatively low cost of PP. Such applications include external coating of gas tanks, baskets of dishwasher machines, grids of refrigerators, metal items used for appliances and furniture.

EXTRUSION

Since the 1980s, PP has been introduced in pipeline coating due to its excellent ability to protect the steel against corrosion [l, 21. The pipeline coating is called a three-layer coating because it is composed of a thin layer of epoxy resin, an intermediate layer of modified PP copolymer and a PP outer layer.

The function of the epoxy layer is to ensure a strong bond to the steel interface by interacting with its metal oxides. The epoxy has high resistance to cathodic disbondment and high thermal stability; its melt- flow behavior facilitates the creation of a thin but uniform film sufficient to fill the anchor pattern in the abraded metal surface.

The intermediate layer ensures a powerful bond between the epoxy primer and the external coating. This intermediate, adhesive layer con- sists of a thin (200-300 p,m) coating of specially formulated PP copolymer with polar groups grafted onto the polymer backbone. These polar groups establish bonds with the epoxy layer while the affinity to PP creates a strong bond with the outer layer.

The external coating provides an additional mechanical strength to the system, since the coating is applied at a thickness of 1.5-2.5 mm depending on pipe diameter and pipe wall thickness. The application process of the coating system is a continuous process.

The pipe surface is cleaned by means of an automatic shot-blasting machine to minimum SA 2% surface finish as per Swedish standard SIS

Extrusion 15 055900; the obtained surface roughness ranges from 40 to 80pm. The pipes are than heated using an induction oven up to a temperature of 200-240C and an epoxy primer is sprayed on the heated pipe in order to cover at least the steel roughness. About 300pm of adhesive PP is applied by lateral extrusion before the epoxy is fully cured; the melt temperature of the adhesive is generally in the 190-210C range. The outer coating is than laterally extruded with a number of overlapping layers such that the PP thickness meets the specification requirements. During this process, a pressure roller smooths the coating and avoids entrapping air bubbles and finally the coated pipe is cooled by spraying with water.

Different layouts can also be used to meet the best production speed according to the pipe diameter, applying, for example, the PP adhesive in powder form or using cross head type extruders instead of lateral extruders.

The three-layer PP system offers a high degree of impact resistance, peel strength especially at high temperatures, indentation resistance and flexibility. The main properties of the coating are reported in Table 2.

Using a suitable thermal stabilizer package, the PP coating can with- stand a continuous operating temperature up to 120C. In order to predict the lifetime of the thermal stabilized coating, accelerated tests are performed at 150C in an oven with forced air and the Arrhenius theoretical equation is used:

log t (x) = log t ( r ) + 5540 X (l/T(x) - 1/423)

Table 2 Properties of the three-layer polypropylene coating (-20 +12OoC)

Property Method Conditions Value

Peeling

Peeling

Impact

Indentation

Indentation

Ultraviolet ageing Thermal ageing

Cathodic disbonding

NF A 49 711 DIN 30678 NF A 49 711 DIN 30678 NF A 49 711 DIN 30678 NF A 49 711 DIN 30678 NF A 49 711 DIN 30678 NF A 49 711 NF A 49 711 DIN 30678 NF A 49 711

23C

120C

23C

23C

110C

800 h 1000 h at 150C 2400 h at 140C 28 days, 23C

>40 N/mm

8 N/mm

>15 J/mm

0.05 mm

16 Anticorrosion coatings with polypropylene

where t(x) is the coating thermal resistance time at temperature T(x) and T(x) is expressed in K, t ( r ) is the coating thermal resistance time at 150C (423K).

It is also necessary to ultraviolet stabilize the coating because the pipes are stored outside before laying; in any case, if high continuous service temperatures are expected, it is advisable to reduce the direct sun exposure time and/or to give a coat of paint or to use other kinds of ultraviolet shielding.

PP coating is not affected by environmental stress cracking and provides very low water absorption thus increasing the reliability of the coating over time, especially in the case of sealines. The three-layer PP system shows excellent resistance to cathodic disbondment, well within international standards even at high temperature. The coating system also shows a high degree of resistance to bacterial and fungal attack.

SPECIAL COATINGS

Coatings for cold climates

Where pipelines are laid in very cold climates, the risk of impact damage due to embrittlement of the coating system becomes a key issue.

The recent development of extremely flexible PP grades has enabled the application of coating systems particularly suitable for cold climate 131. The impact strength and flexibility of the components in these systems is maintained down as far as -45"C, allowing normal handling and laying operations (even reel-barge) a t these temperatures. The low- temperature characteristics of these systems are achieved without sacri- ficing the performance at the other end of the scale; the coatings are capable of withstanding operating temperatures of up to 120C.

These two special grades of adhesive and top coat can be applied using the standard technology obtaining a coating suitable to meet requirements of the cold regions of the world (Table 3) . The peeling test shows a cohesive failure indicating that the adhesion forces to the epoxy are higher than the cohesive forces between the PP matrix phase and the ethylene-propylene rubber (EPR) particles being present as dispersed phase.

Anticorrosion and insulated coatings

Where a temperature drop in the transported fluid could result in phase separation or flow difficulties, the thermal insulation characteristics of the anticorrosion pipeline coatings are also specified.

Special coatings 17 Table 3 Properties of the low-temperature resistant polypropylene coating

Property Method

Peeling

Peeling

Impact

Indentation

Indentation

Ultraviolet ageing Thermal ageing

Cathodic disbonding

NF A 49 711 DIN 30678 NF A 49 711 DIN 30678 NF A 49 711 DIN 30678 NF A 49 711 DIN 30678 NF A 49 711 DIN 30678 NF A 49 711 NF A 49 711 DIN 30678 NF A 49 711

Conditions

23C

110C

-45C

23C

110C

800 h 1000 h at 150C 2400 h at 140C 28 days, 23C

Value

15 N/mm

8 N/mm

>10 J/mm

18 Anticorrosion coatings with polypropylene

Absence of chemical interaction with the sea water and thermal

The entire coating is applied in a single, in-line extrusion process. stability provides long coating life.

Field joints, repairs, bends and fittings

Where pipelines are laid in sections welded in the field, the area around the welded joint must be protected against corrosion in the same way as the rest of the pipe sections. While coating of these areas must be carried out in the field, it is important that the protection at these sites should be comparable with that of the factory-applied coating, in order not to produce weak spots in the system.

Nowadays, field joints can be coated using a system similar to that applied in the factory [5]. After sand-blasting and heating using an induction heater, the weld area receives a coat of epoxy primer and a layer of powdered adhesive is sprayed on. The two PP layers are applied in form of a coextruded sheet. A small extruder is used to seal the seams between the edges of the joint and the main pipe coating.

Alternatively, a PP copolymer layer can be applied to the epoxy- primed, induction-heated joint by means of flame powder spray guns and thus built up to the required layer thickness. The flame powder spray gun technology is also used to coat curved sections of pipeline and fittings.

In case of damaged coating, where damage is superficial or confined to a small area, it may be repaired by welding using a hot-air gun in conjunction with PP adhesive material in stick form. For major damage, the field joint procedures should be used.

Recommendations, n o m s and specifications

In December 1988, the CEOCOR (Comite dEtude de la Corrosion et de la Protection des Canalisations) commission approved a recommendation referred to the PP based coatings, applied by extrusion, as external corrosion protection of steel pipe.

Following the indications of the CEOCOR document and the industrial experiences, national norms have been approved where the main tests to be performed on the coating have been defined. The following national norms have already been issued: DIN 30678 (October 19921, UNI 10416 - Parts 1 and 2, NF A 49-711 (November 1992) and NF A 49-712 (December 1993). At European level the Norm ECISS/TC29/SC4/ WG3N4E is under study.

Different companies have their own PP coating specification, among which are ADCO, Agip, BP, Brown & Root Braun, Chevron, Conoco, Elf

References 19 Aquitaine, Esso, Gaz de France, Gaz de Sud-Ouest, Lasmo Oil, Shell, Snam, Statoil, Total.

REFERENCES 1. Guidetti, G.P., Locatelli, R., Marzola, R. and Rigosi, G.L. (1987) Heat resistant

polypropylene coating for pipelines, in Proceedings of the 7th International Conference on the Internal and External Protection of Pipes, (ed. R. Galka), The Fluid Engineering Centre, Cranfield, pp.203-10.

2. Guidetti, G.P., Rigosi, G.L. and Marzola, R. (1996) The use of polypropylene in pipeline coatings, Prog. Organic Coatings, 27, 79-85.

3. Rigosi, G.L., Marzola, R. and Guidetti, G.P. (1995) Polypropylene coating for low temperature environments, in Proceedings of 4th International Conference on Corrosion Prevention of the European Gas Grid System, IBC Technical Services, London.

4. Rigosi, G.L., Marzola, R. and Guidetti, G.P. (1995) Polypropylene thermal insulated coating for pipelines, in Pipeline Protection, (ed. A. Wilson), Mech- anical Engineering Publications, London, pp 297-310.

5. Bond, P.M. and Goff, B.C. (1993) Novel field joint coating techniques match the latest multi-layer polymeric factory applied coatings, in Pipe Protection, (ed. A. Wilson), Mechanical Engineering Publications, London, pp 59-89.

Keywords: Coating, anticorrosion, extrusion, powder, adhesion, modified polypropylene, electrostatic spray, fluidized bed, epoxy, insulated coating, repair, field joint

Antistatic and conducting composites of polypropylene Gyorgy Banhegyi

BASIC TERMS AND DEFINITIONS

From the viewpoint of electrical behavior, materials can be divided into two groups: conductors and insulators. Sometimes a third group, that of semiconductors, is also distinguished. The specific resistance (p) of a material can be calculated as:

A p = R -

d

where R is the resistance measured between parallel electrodes having surface A at a distance of d. Its dimension is ohm m. In certain practical applications, the specific surface resistance (p) is even more important. It is calculated as:

I d

p R -

where R is the resistivity measured between two parallel linear electrodes of length I at a distance of d.

The surface resistivity range of materials is very wide, covering more than 20 orders of magnitude (Figure 1). Pure polypropylene and propylene copolymers are typical insulators with surface resistance in the order of 1015-10170hm. Materials with such a small conductivity

Polypropylene: A n A-Z Reference Edited by J. Karger-Kocsis Published in 1999 by Kluwer Publishers, Dordrecht. ISBN 0 412 80200 7

-5 -

- EM1 --7---- . RFI

Shielding 0 - -

Conductive

I 5 -

Static dissipation

10- Antistatic

I 4

15 Insula tor

21

, logy (n)

Metals

Carbon black, graphite

I

Semiconductors

Inorganic glasses

I

Plastics

Figure 1 Range of surface resistivity of materials. On the left-hand side, the levels of resistivity are indicated (definitions by various standards are not uniform), while on the right-hand side the resistivity of different groups of materials are shown.

exhibit static charge buildup. This can be an aesthetic problem because of dust collection on plastic furniture, for example, but it can also cause explosion hazard in certain environments. Dust collection can be con- siderably suppressed if the surface resistance is reduced to 109-1013 ohm. This can be achieved by adding certain chemicals known as antistatic agents or simply antistats to the PP compound [I]. For a more complete prevention of static charge buildup the composite must exhibit static dissipation, i.e. it must conduct the charge carriers to the ground. This requires a surface resistivity at least in the order of 105-109 ohm, although in sensitive applications 103-104 ohm is necessary. Such a resistivity level can be achieved only by adding electrically conductive fillers (carbon black, carbon fiber, metals or metallized fillers) to the composite. An even

22 Antistatic and conducting composites of polypropylene

more stringent condition is if EMI/RFI (electromagnetic or radio frequency interference) shielding is required. Shielding effectiveness (SE, measured in decibels) is defined as:

(3)

where E, denotes the electrical field of a source inside a box made of the shielding material and E, is the outer field. S is a sum of reflection &), absorption (A) and internal reflection (R,) terms:

(4)

Attenuation of electrical fields is mainly determined by the conductivity of the wall material, while the attenuation of the magnetic component is determined by the magnetic permeability. Systems with SE < 30 dB are poor EM1 shields, while SE > 60-70 dB indicates a very good shielding. The lower range of EM1 shielding may be achieved by carbon-filled composites, but for good shielding metals or metallized fillers are necessary. If the attenuation of the magnetic components is also required, the admixture of high-permeability fillers (ferrites) is necessary.

The electrical properties of heterogeneous mixtures can be calculated from the corresponding characteristics of the components if the shape factors of the components are known [2, 31. If there is a possibility of direct contact between the filler particles, the so-called percolation phenomenon will occur, i.e. at a critical concentration of the conductive filler, the composite conductivity plotted on a logarithmic scale exhibits a rapid change from values typical for the matrix to values characteristic of the conductive filler (Figure 2). This critical concentration is called percolation threshold. The percolation threshold depends on the shape of the filler: it is the highest for ideally spherical particles, lower for flakes (oblate spheroids) and the lowest for fibers or needles (prolate spheroids). The percolation threshold can be significantly reduced for globular particles as well if the elementary particles are agglomer- ated and can form chains of conductive particles 131. The percolation threshold is lower for semicrystalline polymers (as PI') and for phase separated block copolymer systems (as rubber toughened PP) than for homogeneous, amorphous polymers. The reason for this is that the conductive particles tend to accumulate at the phase boundaries. As the percolation transition is very sharp, the batch-to-batch reproducibility of the resistivity values especially in the semiconducting range is usually medium to poor.

The conductivity of composites containing conductive fillers is usually field, kequency and temperature dependent. Field dependence can be explained by the nonlinearities of charge transfer between particles separated by thin insulating layers (tunneling, charge injection, micro- breakdown). Frequency dependence is caused, among others, by the

SE(dB) = 20 log E , / ,

SE(dB) = R, + A + R,

10 l2 I I

0 -

6 -

6-

2-

0-

Compounds containing antistatic additives

19 (Am)

AI flake Conducting carbon black Carbon fiber

23

Volume fraction

Figure 2 Specific resistivity of various composites made of insulating matrix and conductive fillers.

presence of interfacial polarization between the conducting particles and the insulating matrix. Temperature dependence can be explained by thermal expansion, which also influences the probability of charge transfer between neighboring particles. For the same reason, thermal cycling, processing and mechanical deformation also influence the conductivity level. Thus a great deal of experimentation is necessary to find the best solution for a given application.

COMPOUNDS CONTAINING ANTISTATIC ADDITIVES [ 11

Antistats are low molecular or macromolecular compounds which are either sprayed onto the surface of the plastic (external antistats) or migrate from the bulk to the surface (internal antistats). These compounds are in several respects similar to detergents (surfactants), as they contain both nonpolar and polar groups. The latter attract water


molecules from the ambient atmosphere and this leads to a reduced surface resistance. Antistats can be cationic (mainly quaternary ammon- ium salts), anionic (mainly sodium sulphonates or phosphates) or non- ionic (as glycerol esters of fatty acids or ethoxylated tertiary amines). They are used typically in 0.1-1 wt.%, and are usually admixed in the form of masterbatches. Proper chemical composition and amount is to be selected empirically, as overdosage may cause exudation and plate-out. Polymeric antistats are growing in importance, as they are less prone to migration and loss.

COMPOSITES CONTAINING CARBON FILLER [4,5]

There are two kinds of carbon-based fillers used to produce antistatic and conducting PP composites: carbon black and carbon fiber.

Carbon black contains graphite-like microcrystals permanently fused together during the manufacturing process. The most important characteristics of carbon blacks determining their conductivity are particle size, structure, porosity and volatile content. Smaller particles allow denser packing, while high structure (more branching, extended agglomeration) results in a lower percolation threshold, but greater sensitivity to high shear rates during processing. High porosity means more particles per unit weight and smaller interparticle distance. Low volatile content (especially low oxygen content) is required for good conductivity, as chemisorption reduces the number of mobile charge carriers. Surface area is determined by gas absorption (BET surface), structure is characterized by dibutylphthalate (DBP) absorption, while the volatile content can be determined by thermal desorption coupled with weight measure- ment and gas analysis. Aggregate structure can be determined by electron microscopy. BET surface of conducting carbon blacks varies between 120 and 1500 m2/g. This technique measures the total area (including micropores), while larger molecules can penetrate into larger pores. DBP absorption characterizing the aggregate structure is typically between 150 and 300 m1/100g. Typical particle size is 15-20 nm, volatile content is 1-2 wt.%.

Carbon black filled antistatic and conducting composites usually contain 10-30 wt.% filler. (Addition of 1-2 wt.% carbon black for improving the weatherability essentially does not change the conductivity, although it somewhat increases the dielectric loss). The addition of conducting carbon black to thermoplastics increases not only the electrical conductivity, but also the modulus, tensile strength, hardness, melt viscosity and the heat distortion temperature of the compound. It reduces, however, the elongation to break and impact properties.

In certain antistatic compositions, graphite or carbon powder is used as conductive filler. In some cases, carbon black is combined with glass

Composites containing metal or metallized fillers 25 Table 1 Comparison of some properties of PP composites containing carbon- based fillers

Property Compound

Filler Density (g/cm3) MFI (230C 10.8 kg) Tensile strength (MPa) Yield strength (MPa) Elongation to break (%) Bending modulus (GPa) Notched impact strength (kJ/m2) p (ohm m) ps (ohm)

1 2

no c.b. 0.90 1.07 112 50 12 18 26 19 120 n.a. 0.97 n.a.

8 14 0.05

6

3

c.b. 1.08 n.a. 18 22 31 n.a. 5

0.15 400

4

c.b. 1.14 46 n.a. 11 35

0.55 58

0.24 50

5 6

c.b. c.p. 1.08 1.06 n.a. n.a. 29 24

n.a. n.a. 7 22

2.30 1.10 n.a. n.b. 100 10 105 io,

7

c.f. 1.06 n.a. 47

n.a. 0.5 11.4 n.a. 1

100

__

Abbreviations: no = no filler, c.b. = carbon black, c.p. = carbon powder, c.f. = carbon fiber, n.a. = not available, n.b. = no break.

fiber to improve the mechanical properties (primarily modulus and strength).

Carbon fibers are mainly manufactured from PAN fibers or from tar pitch by high-temperature pyrolysis in an inert atmosphere. Higher graphitization temperature results in higher conductivity and modulus. Surface treatment with donor or acceptor compounds can increase the conductivity of carbon fibers by orders of magnitude. Carbon fibers cause a steeper increase in modulus and strength than carbon black, but the price is higher too. In some cases, carbon fibers are combined with carbon black to achieve the required combination of properties.

Some important properties of carbon black filled and carbon fiber reinforced PP composites are compared with those of nonfilled PP grades in Table 1.

COMPOSITES CONTAINING METAL OR METALLIZED FILLERS 14, 61

Although an attenuation of 20-50 dB can be achieved by carbon black and 30-50 dB by carbon fibers, if a really good EM1 shielding is required, metals must be used. In EM1 shielding applications, the parts are usually produced by injection or by compression molding, therefore the viscosity of the compound must not be excessively high. Therefore, although metal powders or metallized glass spheres are used in some applications (mainly in conducting paints and adhesives), anisometric fillers are applied more frequently. Typical anisometric fillers are metal flakes and


metal fibers. Metallized platelets (e.g. mica) and fibers (glass or carbon fiber) are also on the market.

Metal flakes are produced by extremely rapid cooling (in the order of 106 K/s), which results in very special crystalline structure and mechanical properties. Although several metals can be processed in this way, aluminum alloys are used most frequently. The flakes are strongly anisometric (about 1 mm X 1 mm X 30 km), therefore the conductivity is significantly decreased at a volume fraction of about 0.1. About 15vol.% aluminum flake is needed for static dissipation, 20 vol.% for EM1 shielding and 25vol.% for good heat conductivity. In the case of metallized mica, about 4 vol.% is needed for antistatic and 10 vol.% for EM1 shielding applications. Due to the specific gravity differences, the weight fractions are higher. Good EM1 shielding is, for example, achieved at an aluminum flake content of about 40 wt.%. The shielding efficiency can be well calculated (within 5 dB) using semi-empirical formulae. Dominant terms are R, and A (for notation see equation (4)):

(5) R,(dB) = K,- K2 log ( p k f )

where k is the magnetic permeability, p is the specific volume resistivity, f is the frequency, and t is the layer thickness. The value of constants K,, K2 and K3 depend on the unit system used. SE values of 30-50 dB can be routinely achieved with aluminum flakes. Aluminum flake filled plastics usually exhibit much higher viscosity than the nonfilled counterparts. These composites must be processed with care; high shear rates, small diameter runners, sharp corners and sudden wall thickness variations should be avoided. In some cases, sandwich structures are molded; the EM1 shielding internal layer is covered by an aesthetically attractive nonfilled layer.

Metal fiber filled plastics have become popular, as the high aspect ratio of fibrous fillers allows the lowest loading level for a given conductivity. For example, the same level of conductivity can be achieved by adding 40 wt.% aluminum flake and 7 wt.% stainless steel fiber. There are natural limits for the increase of aspect ratio, however. If the modulus of the filler is high (stiff fibers), above a certain length the fiber breaks into pieces during melt processing or compounding. This is the case, for example, with metallized carbon or glass fibers. Composites containing such fibers have high modulus and strength. If the filler material is tough and ductile (as in the case of metals), the fibers tend to coil and become entangled. Due to the low critical volume fraction, the properties of conductive composites containing metal fillers differ less from those of the nonfilled polymers than in the case of carbon or metallized glass fiber

References 27 Table 2 Comparison of some properties of PP composites containing A1 flake and stainless steel fillers

Property Compound

1 2 3

Filler no A1 f. S.S. Density (g/cm3) 0.90 1.23 0.95 MFI (230C 10.8 kg) 112 n.a. 25 Tensile strength (MPa) 12 24 28 Yield strength (MPa) 26 n.a. n.a. Elongation to break (%) 120 3 39 Bending modulus (GPa) 0.97 2.75 1 .o

p (ohm m) >lo16 1 0.1 ps (ohm) > 10'6 100 104

Notched impact strength (kJ/m*) 8 n.a. n.a.

~~

Abbreviations: no = no filler, A1 f. = aluminium flake, S.S. = stainless steel fiber, n.a. = not available.

filled systems. Stainless steel fibers are most popular because of their good mechanical and corrosion resistance properties. Pellets with longer fibers are produced not by compounding the chopped fiber with the melt but by melt coating of infinite sized fiber rovings, followed by pelletiza- tion. In these systems, the initial fiber size is comparable to the pellet size. Attenuation levels of 3040dB can be achieved by stainless steel fibers and 50-60dB by nickel-coated carbon fibers. Higher levels of attenuation are required in applications which allow more expensive fillers. Table 2 summarizes the properties of aluminum flake and stainless steel fiber filled PP compounds.

REFERENCES 1. Connor, M. (1997) Antistatic agents, Modern Plastics Encyclopedia, C-3. 2. BBnhegyi, G. (1986) Comparison of electrical mixture rules for composites,

Colloid Polym. Sci., 264, 1030-1050. 3. McCullough, R.L. (1985) Generalized combining rules for predicting transport

properties of composite materials, Composites Sci. Technol., 22, 3-21. 4. (a) Whittaker, G. (1986) Antistatic and electrically conductive carbon black

filled thermoplastic compounds, in Fillers, Proceedings of the Joint Conference of the Plastics and Rubber Institute and the British Plastics Federation, March 1986, Elsevier, Amsterdam. (b) Simon, R. (1986) EM1 shielding with aluminum flake filled polymer composites, in Fillers, Proceedings of the Joint Conference of the Plastics and Rubber Institute and the British Plastics Federation, March 1986, Elsevier, Amsterdam.

5. Sichel, E.K. (ed) (1982) Carbon Black -Polymer Composites, Marcel Dekker, New York.

28 Antistatic and conducting composites of polypropylene 6. Bhattacharya, S.K. (ed) (1986) Metal-Filled Polymers; Properties and Applications,

Marcel Dekker, New York.

Keywords: antistatic, conductivity, insulator, electric resistance, electromagnetic shielding, EMI, radio-frequency interference shielding, RFI, percolation, carbon black, carbon fiber, fillers, BET surface, metal-coated fibers, semiconductor, antistatic compounds, conductive fillers.

Appliances J. Bentham

DEFINITION

Polypropylene (PP) has developed over recent years as the dominant polymer, in volume terms, used by the appliance industry. Before discussing the markets, consumption, applications and properties, it would be worth defining what is included in the appliance industry. The industry can be separated into two product segments.

Household appliances is a generic term used to refer to the 'smaller' appliances which can be bought as an addition to the kitchen, house or garden. Many of these items have developed over the decades as labour-saving devices and more recently as lifestyle products. Within household appliances there are four groupings, small kitchen appliances; floor care appliances; personal care appliances; and garden appliances.

White goods is the collective term for the 'large' appliances generally seen in and around the kitchen. Whereas many household appliances are perceived as optional, most white goods products are regarded as essential to modern day life, particularly in the developed markets. The term 'white goods' is derived from the white paint applied to the products. Three groupings comprise white goods: washing appliances; refrigeration equipment; and cooking appliances.

Polymers, including PP, are widely used in other consumer electrical goods, such as brown goods and the home computer market. These will not be included in this chapter and the focus will be on household appliances and white goods.


30 Appliances

MARKETS

There are three major world markets for appliances, Europe, North America and Asia, plus some smaller but fast developing areas, such as South America, Africa and the Middle East. There are similarities between the three major markets but also distinct differences in product type and growth rate which thus affects PP and its consumption. The drives which fuel the demand for appliances are numerous but there are several fundamental factors which are common to all markets:

product saturation: (the percentage of the total number of households

0 demographics and social changes; 0 gross domestic product (GDP), linked to spending power.

Europe overall is a very saturated market with only a handful of products, such as microwave ovens and dishwashers, having growth potential. The European population is growing slowly, and there is some change in household numbers linked to the rise in single-parent families and vacation home purchases. Growth in GDP is small in Europe and spending confidence remains low. In summary, Europe is a tough market for the appliance industry which interestingly has benefited PP due to the need for continuous cost reduction.

The North American market is very similar to Europe but in some key areas is more advanced in the drive for cost reduction.

If the saturated Japanese market is excluded from the Asian total, then the remainder is probably the most dynamic world area today. Many countries are still developing, so saturation levels are low. Populations are growing rapidly and social changes are increasing the number of households, creating percentage growth figures for most appliance products in double figures. Other regions, such as South America, have the potential of many Asian countries but this will depend upon economic development [ l l .

which possess the product);

POLYPROPYLENE CONSUMPTION

For simplicity, and due to the maturity level, the European market will be used to illustrate the development of PP consumption.

Household appliances

For virtually all units in this segment there is the need for a 'housing' to contain the various electrical components and, in many cases, a foodstuff. Metal was the chosen housing material for many years, but as the polymer producing and conversion industry developed so plastics pene- trated this application. The typical water boiling kettle is a classic

Polypropylene consumption 31

Household Appliances (%)

1985 1993 000

Figure 1 European usage of polymers in household appliances.

example of how this substitution process has worked. Metals were substituted during the 1970s and the 1980s by polymers such as polyoxy- methylene (POM) and ABS. Then with the development of PP, married with improved design and the drive to reduce costs, we see that today most kettles have a PP housing. Kitchen appliances, and to some extent floor care appliances, are the two groupings where this has occurred the most. The percentage consumption figures for the segment reflect this development. In the mid 1980s polypropylene was around one-quarter of the total polymer consumption. This grew significantly in the early 1990s and it is probable that by year 2000 PP will account for almost half the polymer consumed in household appliances (Figure 1) [2].

White goods

The role of polymers in this segment varies greatly according to the product grouping. Cooking appliances, not surprisingly, involve high operational temperatures and are therefore dominated still by metal. Refrigeration equipment operates at the opposite end of the temperature scale and hence has different material requirements. Polymers have made inroads for insulation material and for liner materials. PP has some limited applications in refrigeration today, but improved properties should increase consumption in the future.

Washing appliances operate in a temperature range more suited to PP (maximum 95C) and the presence of fluids creates no problems as PP is not hygroscopic. Many applications have developed for internal components replacing other polymers and metals.

32 Appliances

White Goods ("/o)

1985 1993 2000

ABS E3 PS H PVC 0 Others I I

Figure 2 European usage of polymers in white goods.

Combining the three groupings in white goods creates a very different polymer consumption profile than household appliances. The four main polymers, PP, PU, ABS and PS dominate through the years, and although in percentage terms PP continues to grow this is not at the expense of other polymers but at the expense of metals (Figure 2) [3]. In fact, polymers are predicted to account for 24% of all materials consumed in white goods by year 2000 as opposed to 17% in 1985 [41.

APPLICATIONS AND PROPERTY REQUIREMENTS

Household appliances is a very competitive global market which requires PP producers to deliver materials not only to an exacting property specification, but also taking into account design appeal, faster development cycles and cost savings, particularly weight savings [51.

As mentioned earlier, kitchen appliances are where PP is commonly used for housings (Table 1).

Table 1 Typical kitchen appliances and their material requirements

Housings for Proper ties Polypropylene types ~~~~ ~ ~

Kettles Surface finish/gloss Heat stabilized homopolymers Coffee machines Stiffness (flexural modulus) Mineral reinforced PP Toasters Heat resistance (HDT) High isotacticity PP Deep fat fryers Temperature stability Irons Processability (MFI)

Colorability

Applications and property requirements 33 By utilizing additivation technology, a good high flow PP homo-

polymer can be stabilized for a coffee machine or kettle housing and offers the most cost-effective solution. Traditionally, if increased heat resistance, heat distortion temperature (HDT) and stiffness is needed then mineral reinforced PP is used, typically 10% or 20% talc reinforced. A more recent development is high isotacticity polypropylene which can achieve the stiffness and heat performance of mineral filled grades with the density of a regular homopolymer. Over the coming years, it is probable that high isotacticity PP will replace mineral reinforced grades in many applications and with improved scratch resistance also chal- lenge ABS, (Figure 3).

Food preparation equipment, such as mixers and blenders, is an area of kitchen appliances where as yet PP has failed to penetrate. This is because the high gloss, stain and scratch resistant requirements are more exacting, although each new PP development brings it closer to the specification. Similarly personal care appliances are still using ABS.

Floor care appliances is a growing area for PP, again as a housing material but also for internal components. Vacuum cleaners dominate

Figure 3 Kettle manufactured from PP with 10% mineral addition.

34 Appliances

Table 2 Application of PP in vacuum cleaners

Application Cleaner type Properties Polypropylene type

Housing Upright Stiffness Homopolymer PP Upper housing Canister Aesthetic surface Mineral reinforced PP

High gloss High isotacticity PP Colorability

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Polypropylene - An a to Z Reference