CASTABLE POLYURETHANE ELASTOMERS SECOND EDITION This page intentionally left blank CASTABLE POLYURETHANE ELASTOMERS SECOND EDITION I.R. CLEMITSON Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2015 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Version Date: 20150417 International Standard Book Number-13: 978-1-4987-2639-9 (eBook - PDF) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmit- ted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright. com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com Contents Preface xiii About the Author xv Symbols and Acronyms xvii I Introduction to Polyurethanes 1 1 Introduction to Polyurethanes 3 1.1 Background . 3 1.2 History . 3 1.2.1 Timeline . 4 1.2.2 Nomenclature . 6 1.2.3 Nature of Polymer . 6 1.2.4 Applications . 6 1.2.5 \CASE" Elastomers . 8 2 Chemistry of Polyurethanes 13 2.1 Introduction . 13 2.1.1 Background . 13 2.1.2 Basic Reactions of Urethanes . 15 2.1.3 Side Reactions . 17 2.1.4 Polyureas . 17 2.1.5 Water Reactions . 18 2.2 Raw Materials . 19 2.2.1 Polyols . 19 2.2.2 Diisocyanates . 22 2.2.3 Chain Extenders . 25 2.2.4 Other Chemicals . 30 2.3 Prepolymers . 31 2.3.1 Introduction . 31 2.3.2 Prepolymer Variants . 31 2.3.3 One-Shot Systems . 33 2.4 Urea and Urethane Reactions . 34 2.4.1 Introduction . 34 2.4.2 Reaction Speed . 35 2.5 Chain Extension . 36 v vi Contents 2.5.1 Urea . 36 2.5.2 Urethane . 37 2.5.3 Hydrogen Bonding . 38 2.5.4 Three-Dimensional Cross-Linking . 41 2.5.5 Catalysts . 42 2.6 Degradation . 44 2.6.1 Prepolymers . 44 2.6.2 Polyester Elastomers . 44 References 45 II Health and Safety 47 3 Health and Safety 49 3.1 Introduction . 49 3.1.1 Rationale . 49 3.1.2 Work Environment . 50 3.1.3 Acute Exposure . 50 3.1.4 Chronic Exposure . 50 3.2 Workplace . 50 3.2.1 Information Sources . 51 3.2.2 Signage . 53 3.3 Prepolymer Preparation . 53 3.3.1 Isocyanate . 53 3.3.2 Polyols . 54 3.3.3 Prepolymers . 55 3.3.4 Curatives . 55 3.3.5 Catalysts . 56 3.3.6 Other Additives . 57 3.3.7 Solvents . 58 3.3.8 Heat . 59 3.4 Engineering . 60 3.4.1 Gasses . 60 3.4.2 Workplace . 62 3.5 Safety Data Sheet Format . 63 References 67 III Processing 69 4 Prepolymer Production 71 4.1 Prepolymers . 71 4.1.1 Ease of Production . 72 4.1.2 Isocyanate Levels . 72 4.1.3 Structure of Polyurethane . 73 4.1.4 Reduction in Final Exotherm . 73 Contents vii 4.1.5 Easier Handling of Components . 73 4.1.6 Final Properties . 74 4.2 Laboratory Preparation . 74 4.2.1 Equipment . 75 4.2.2 Reactions . 76 4.2.3 Monitoring Reaction . 77 4.2.4 Prepolymer Storage . 78 4.3 Commercial Preparation . 78 4.3.1 Safety . 79 4.3.2 Raw Material Storage . 81 4.3.3 Raw Material Preparation . 82 4.3.4 Reactor . 84 4.3.5 Nitrogen . 87 4.3.6 Heating/Cooling . 88 4.3.7 Process Control . 89 4.3.8 Vacuum . 90 4.3.9 Discharging Batch . 91 4.3.10 Quality Control and Assurance . 92 4.3.11 Typical Process . 93 4.4 One-Shot System . 94 4.5 Quasiprepolymers . 95 References 96 5 Processing Fundamentals 99 5.1 Introduction . 99 5.1.1 Process Definition . 99 5.1.2 Importance of the Process . 99 5.1.3 Changes in Material Properties Before, During, and Af- ter Curing. 100 5.1.4 Stages of Curing and Factors Affecting Cure . 101 5.2 Introduction to Molding Process . 103 5.3 Health and Safety Concerns during Casting . 107 5.4 Mold Preparation . 108 5.4.1 Molds . 108 5.4.2 Cleaning and Repair . 109 5.4.3 Mold Release . 109 5.4.4 Assembly . 110 5.5 Batch Size Adjustment . 110 5.5.1 Quantity of Polyurethane . 110 5.5.2 Weight Calculations . 110 5.6 Prepolymer . 111 5.6.1 Calculations . 114 5.7 Pigments and Additives . 116 5.8 Curatives . 117 viii Contents 5.9 Degassing . 119 5.10 Mixing and Casting . 120 5.10.1 Premixing . 120 5.10.2 Curatives . 121 5.10.3 Mixing . 121 5.10.4 Casting . 122 5.11 Curing and Post Curing . 123 6 Processing 125 6.1 Molding Methods . 125 6.1.1 Rotational Casting . 125 6.1.2 Centrifugal Casting . 126 6.1.3 Vacuum Casting . 127 6.1.4 Compression Molding . 127 6.1.5 Liquid Injection . 129 6.1.6 Complex Shapes . 129 6.2 Bonding . 130 6.2.1 Precasting Preparation . 130 6.2.2 Chemical Treatment . 131 6.2.3 Bonding Primer . 132 6.2.4 Casting and Curing of Bonded Prepolymer . 132 6.2.5 Post Casting . 133 6.2.6 General . 133 6.3 Finishing . ..