Handbook of Thermoset Resins Debdatta Ratna Handbook of Thermoset Resins Debdatta Ratna iSmithers – A Smithers Group Company Shawbury, Shrewsbury, Shropshire, SY4 4NR, United Kingdom Telephone: +44 (0)1939 250383 Fax: +44 (0)1939 251118 http://www.rapra.net First Published in 2009 by iSmithers Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK ©2009, Smithers Rapra All rights reserved. Except as permitted under current legislation no part of this publication may be photocopied, reproduced or distributed in any form or by any means or stored in a database or retrieval system, without the prior permission from the copyright holder. A catalogue record for this book is available from the British Library. Every effort has been made to contact copyright holders of any material reproduced within the text and the authors and publishers apologise if any have been overlooked. Every effort has been made to contact copyright holders of any material reproduced within the text and the authors and publishers apologise if any have been overlooked. ISBN: 978-1-84735-410-5 (hardback) 978-1-84735-411-2 (softback) Typeset by Argil Services Printed and bound by Lightning Source Inc. Preface This book is dedicated to thermoset resins, an important class of polymer materials. Unlike thermoplastics, thermoset resins are characterised by a curing reaction, which converts the low molecular weight liquid resins (easy to process) into solid three- dimensional network structures. The main advantage of a thermoset over a thermoplastic is that a wide range of properties can be achieved by simply adjusting the crosslink density of the thermoset network, without changing the chemical structure. As a student of polymer science and a researcher in the field of thermoset resins, I always felt the lack of a self-sufficient book dedicated to thermoset resins. That is why I decided to compile my fundamental understanding and long research experience in this specialised field and present it in the form of a book when I was invited to do so by Ms. Frances Gardiner (Smithers Rapra Technology, UK) after the publication of my Rapra Review Report (No. 185) on Epoxy Resins. I am thankful to her and her team for their cooperation and encouragement. The major part of this book was written when I was a visiting scientist to the Institute of Composite Materials (IVW), Technical University, Kaiserslautern, Germany. Alexander von Humboldt foundation, Germany, was the sponsor for my fellowship and Professor J. Karger-Kocsis was my host, who has advised and encouraged me during my entire research stay in Germany. Dr. Thomas Abraham, who was a post doctoral fellow from the very beginning of my tenure in IVW, had helped me a lot to prepare the large number of figures for the book. Dr. Wanjale joined as a post doctoral fellow in IVW at a later part of my tenure and also helped me to a certain extent. I would like to acknowledge all of their contributions. I wish to thank Dr. Narayana Das, Director, Naval Materials Research Laboratory (NMRL), Dr. B.C. Chakraborty, Head of polymer division, NMRL and my other colleagues of NMRL for their encouragement and supports. I have divided this book into seven chapters. It starts with a general introduction to thermosets, which includes network concept, additives and techniques/instrumentations (their principles) used to characterise a thermoset resin. The chemistry, properties and applications of individual thermoset resins are discussed in Chapters 2 and 3. Chapters 4 and 5 deal with the modification of thermoset resins for improvement in fracture toughness. The thermoset-based composites and nanocomposites are i Thermoset Resins discussed in Chapters 6 and 7, respectively. With such broad technical content covering the basic concepts and recent advances, I am sure this book will serve as a useful textbook-cum-handbook for the students, researchers, engineers, R&D scientists from academia, research laboratories and industries. It will be extremely useful for the scientists and researchers to make a knowledge-base in the subject as well as to plan their future works because I have not only presented the review of the recent advances in this book but also highlighted the future directions of research in the various areas of thermoset resins. The bounty of information garnered in this book will serve as a fountainhead for further exiting development in the field of thermoset resins in general and thermoset nanocomposites in particular. I would like to dedicate this book in the memory of my father late Lakshmikanta Ratna. The best wishes of my mother (Snehalata Ratna), in-laws, sisters, Sunilda and other well wishers have always been the driving force and heaven’s light (Almighty’s blessing) has been the guide behind this creation. I am thankful to my father-in-law Shri Nirmalendu Sathpathi for not only his moral support but for his editorial assistance. For writing this book, I had to utilise much of the quality time, which I generally give, to my family. Hence I am sincerely thankful and indebted to my wife (Sujata) and sons (Saptarshi and Debarshi) for their patience and for always being the source of inspiration, without which this book would have not been in reality. Debdatta Ratna Summer 2009 ii Contents 1 General Introduction to Thermoset Networks 1 1.1 Introduction ...........................................................................1 1.2 Network Concept ...................................................................1 1.3 Gelation ..................................................................................2 1.4 Cure Characteristics................................................................ 5 1.5 Effect of Vitrification on Polymerisation Rate .........................8 1.6 Effect of Cure Conversion on Glass Transition Temperature (Tg) ..................................................................10 1.7 Crosslinked Density (Xc) ......................................................12 1.8 Additives for Thermoset Resins ............................................ 14 1.8.1 Antioxidants ..................................................................... 14 1.8.2 Fillers ...............................................................................17 1.8.3 Blowing Agents ................................................................17 1.8.4 Coupling Agents ...............................................................18 1.8.5 Surfactants .......................................................................18 1.8.6 Colorants .........................................................................19 1.8.7 Other Additives ................................................................19 1.9 Processing of Thermoset Resins ............................................19 1.9.1 Die Casting ....................................................................... 19 1.9.2 Rotational Casting ...........................................................20 1.9.3 Compression Moulding ....................................................20 1.9.4 Reaction Injection Moulding Process (RIM) .....................21 1.10 Characterisation of Thermoset Resins ...................................22 1.10.1 Titration ...........................................................................22 1.10.2 IR Spectroscopy ................................................................ 23 1.10.3 NMR Spectroscopy ..........................................................23 1.10.4 Distribution of Molecular Weights ................................... 24 iii Thermoset Resins 1.10.4.1 Viscometry ......................................................25 1.10.4.2 End-Group Analysis ........................................26 1.10.4.3 Vapour Pressure Osmometry ........................... 26 1.10.4.4 Membrane Osmometry ...................................26 1.10.4.5 Light Scattering ...............................................27 1.10.4.6 Gel Permeation Chromatography (GPC) ......... 28 1.10.5 Morphological Characterisation .......................................28 1.10.5.1 Scanning Electron Microscopy (SEM) ............. 28 1.10.5.2 Transmission Electron Microscopy (TEM) ...... 29 1.10.5.3 Atomic Force Microscopy (AFM) ....................29 1.10.5.4 X-ray Diffraction (XRD) ................................. 31 1.10.6 Thermal Analysis .............................................................. 31 1.10.6.1 Differential scanning Calorimetry (DSC) ......... 31 1.10.6.2 Dynamic Mechanical Analysis (DMA) ............ 32 1.10.6.3 Time–Temperature Superposition (TTS) .......... 34 1.10.6.4 Thermogravimetric Analysis (TGA) .................35 1.10.7 Rheological Characterisation ............................................ 35 1.11 Testing and Evaluation of Thermoset Resins .........................38 1.11.1 Mechanical Properties ......................................................38 1.11.1.1 Tensile Test ......................................................40 1.11.1.2 Flexural Test ....................................................42 1.11.1.3 Creep Test .......................................................43 1.10.1.4 Fatigue Test .....................................................44 1.11.2 Fracture Toughness (K1c) ................................................. 45 1.11.3 Impact Test .......................................................................47 1.11.3.1 Pendulum Impact Test ..................................... 47 1.11.3.2 Falling Weight Impact Test .............................. 48 1.11.4 Heat Distortion Temperature (HDT) ...............................