Fire Properties of Polymer Composite Materials

Transcription

1 Fire Properties of Polymer Composite Materials

2 SOLID MECHANICS AND ITS APPLICATIONS Volume 143 Series Editor: G.M.L. GLADWELL Department of Civil Engineering University of Waterloo Waterloo, Ontario, Canada N2L 3GI Aims and Scope of the Series The fundamental questions arising in mechanics are: Why?, How?, and How much? The aim of this series is to provide lucid accounts written by authoritative researchers giving vision and insight in answering these questions on the subject of mechanics as it relates to solids. The scope of the series covers the entire spectrum of solid mechanics. Thus it includes the foundation of mechanics; variational formulations; computational mechanics; statics, kinematics and dynamics of rigid and elastic bodies: vibrations of solids and structures; dynamical systems and chaos; the theories of elasticity, plasticity and viscoelasticity; composite materials; rods, beams, shells and membranes; structural control and stability; soils, rocks and geomechanics; fracture; tribology; experimental mechanics; biomechanics and machine design. The median level of presentation is the first year graduate student. Some texts are monographs defining the current state of the field; others are accessible to final year undergraduates; but essentially the emphasis is on readability and clarity. For a list of related mechanics titles, see final pages.

3 Fire Properties of Polymer Composite Materials by A.P. MOURITZ RMIT University and CRC for Advanced Composite Structures Melbourne, Victoria, Australia and A.G. GIBSON University of Newcastle-upon-Tyne Centre for Composite Materials Engineering England, UK

4 A C.I.P. Catalogue record for this book is available from the Library of Congress. ISBN X (HB) ISBN (HB) ISBN (e-book) ISBN (e-book) Published by Springer, P.O. Box 17, 3300 AA Dordrecht, The Netherlands. Printed on acid-free paper All Rights Reserved 2006 Springer No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work.

5 Table of Contents Preface ix 1 Introduction 1.1 Background Fire reaction and fire resistance of composites Composites and fire Case studies of composites in fire Concluding remarks 17 References 18 2 Thermal Decomposition of Composites in Fire 2.1 Introduction Thermal decomposition mechanisms of organic polymers Rate processes and characterisation of decomposition Polymers and their decomposition processes Fire damage to composites Concluding remarks 55 References 56 3 Fire Reaction Properties of Composites 3.1 Introduction Time-to-ignition Heat release rate Extinction flammability index & thermal stability index Mass loss Smoke Smoke toxicity Limiting oxygen index Surface spread of flame Fire resistance 96 References 98 4 Fire Modelling of Composites 4.1 Introduction Thermal exposure Modelling material fire dynamics Structural modelling of fire response 122 References 131 v

6 vi Fire Properties of Polymer Composite Materials 5 Modelling the Thermal Response of Composites in Fire 5.1 Introduction Response of composites to fire Modelling heat conduction in composites Modelling the fire response of composites Modelling the thermal properties of composites Concluding remarks 157 References Structural Properties of Composites in Fire 6.1 Introduction Laminate properties Measurement of elastic constants Mechanical properties as a function of temperature Modelling of properties Fire resistance of laminates under load Modelling of fire resistance of laminates under load Concluding remarks 211 References Post-Fire Properties of Composites 7.1 Introduction Post-fire properties of laminates Modelling the post-fire properties of laminates Post-fire properties of sandwich composites Post-fire properties of fire protected composites Concluding remarks 235 References Flame Retardant Composites 8.1 Introduction The combustion cycle Flame retardants for composites Flame retardant fillers for composite Flame retardant organic polymers for composites Flame retardant inorganic polymers for composites Flame retardant fibres for composites Fire protective surface coatings 273 References Fire Properties of Polymer Nanocomposites 9.1 Introduction Characterization of nanocomposite formation Evaluation of fire retardancy Clay modifications 294

7 Table of Contents vii 9.5 Examples of fire retardancy of polymer nanocomposites Mechanisms of fire retardancy in nanocomposites Future trends in fire retardancy of nanocomposites 307 References Fire Safety Regulations 10.1 Introduction Fire safety regulations for rail Fire safety regulations for automobiles, buses and trucks Fire safety regulations for civil infrastructure Fire safety regulations for civilian aircraft Fire safety regulations for ships and submarines 318 References Fire Tests for Composites 11.1 Introduction Scale of fire reaction tests Cone calorimeter Atmosphere controlled cone calorimeter Intermediate-scale cone calorimeter Ohio State University calorimeter Limiting oxygen index test Flame spread tests Smoke density tests Furnace tests Burn-through & jet fire tests Single burning item test Room fire tests Structural integrity in fire tests Aircraft fire tests Concluding remarks 354 References Health Hazards of Composites in Fire 12.1 Introduction Smoke toxicity test methods Health hazards of combustion gases N-gas model for smoke toxic potency Health hazards of fibres Personal protective wear against burning composite materials Concluding remarks 380 References 381 Subject Index 385

8 Preface This book is the first to deal comprehensively with the important topic of the fire behaviour of polymer composite materials. Composites are used in a diverse range of applications, including land and marine transport, aerospace, the chemical industry, and most branches of civil engineering infrastructure. It is our belief that fire behaviour is the single most important factor limiting the wider use of composites in many of these areas. Our aim in producing this volume is therefore to stimulate the work that is needed to overcome this fundamental problem. The first step in such a journey is, of course, to summarise what is presently known, which is what we have attempted here. This book aims to be an authoritative reference source. The book covers all of the key issues on the behaviour of polymer composites in fire. This includes a description of the thermal degradation and combustion mechanisms of composites, including the thermal decomposition reactions, reaction rates, flammable volatiles and toxic gases of organic polymers and fibres. The fire reaction properties that define the flammability and fire hazard of polymer composites are described, including time-to-ignition, heat release rate, flame spread, smoke and gaseous combustion products. The fire resistive properties of composites are also described, including the key properties of burn-through rate and mechanical integrity during and after fire. General principles and quantitative models are presented for predicting the development and spread of fire together with models for calculating the decomposition and thermal response of composites to fire. Low flammability and fire resistive materials for composites are described, including flame retardant organic and inorganic polymers, protective coatings, and polymer nanocomposites. Also covered are fire safety regulations, fire test methods, and the health hazards of burning composites. The book also identifies gaps and deficiencies in our current understanding of the fire performance of composites in order to determine the main issues that require further investigation. Chapter 1 gives an introduction to the fire hazard of polymer composites. The chapter provides a general overview of fires, flames and the combustion of polymer composites. In addition, definitions to the key fire reaction and fire resistive properties that define the fire hazard of composites are given. Numerous examples and case studies of fire in ix

9 x Fire Properties of Polymer Composite Materials aircraft and ships containing composites are provided to illustrate their potential hazard, and to demonstrate the need to develop more flame resistant materials. Chapter 2 outlines the thermal degradation mechanisms that govern the fire reaction and fire resistive properties of polymer composites. The combustion process of composites is described, with special consideration given to those factors that control the process: heat flux, pyrolysis of the polymer matrix and organic fibres, evolution of flammable gases, and char formation. The pyrolysis reactions and combustion gases of organic polymers and fibres that are commonly used in composites are described, including polyesters, vinyl esters, epoxies, phenolics and several thermoplastics used for the matrix phase and organic fibres such as aramid and polyethylene for the reinforcement. The chapter also describes the microstructural damage suffered by laminates and sandwich composites in fire, such as charring, skin-from-core debonding, delamination and matrix cracking. The fire reaction and fire resistive properties of polymer composites are outlined in Chapter 3. The fire reaction properties that influence the initiation, growth and spread of fire and determine the survival of humans exposed to fire are described. These properties are ignition time, heat release rate, limiting oxygen index, flame spread rate, smoke and gas emission. Many examples are provided of the fire reaction properties of thermoset laminates, thermoplastic laminates and sandwich composite materials. The fire resistive properties of composites are also discussed, with special attention given to burn-through resistance and heat transmission because of their influence on fire containment and flame spread. Later chapters are devoted to comprehensive descriptions of other fire resistive properties, namely degradation of mechanical properties in fire and post-fire structural properties. The growth and spread of fire is described in Chapter 4 by Dr Brian Lattimer (Hughes Associates, Inc) and Ted Matthews (Materials Sciences Corporation). An overview of analytical models, finite element tools, computational fluid dynamic codes and other methods to theoretically analyse the development and spread of fire is described, with emphasis given to flame spread within enclosed spaces. Models are also presented for calculating several key fire reaction properties of polymers and polymer composites, including ignition time, heat release rate and flame spread. Included is a critique of the strengths and limitations of the various models for analysing fire behaviour. The chapter also introduces the many approaches towards modelling the structural response of composite to fire, which is a topic expanded upon in Chapter 6. Chapter 5 outlines models for predicting the thermal and physical response of composites to fire. Models are described that range in complexity from simple analysis that only consider heat transmission in a thermally-stable material to complex models that consider a number of thermo-physical processes in a decomposing laminate, including heat conduction; radiation losses; internal heat evolution/absorption due to decomposition of the organic matrix; internal pressure and flow of gaseous reaction products; thermal swelling and strains. The reliability of the models to accurately

10 Preface xi predict the fire behaviour of composites is examined, and numerous examples of the application of the models to composites are given. Chapters 6 and 7 describe the deterioration to the mechanical properties and structural performance of composites during and after fire, respectively. Models and experimental information on the degradation to the load-bearing properties of laminates and sandwich composites at elevated temperature, in fire, and after the fire has been extinguished are presented. The thermal damage responsible for the reduction to the mechanical properties is discussed as well as methods for improving the structural performance of composites in fire. An overview of methods for reducing the fire risk of composites is given in Chapter 8. The efficacy of various types of flame retardant polymer systems are described, including polymers with flame retardant fillers, halogenated polymers, char forming polymers, and polymers that are chemically and structurally modified to increase flammability resistance. The fire behaviour properties of highly flame resistant composites are discussed, such as geopolymer laminates and other inorganic matrix materials. The fire protection provided by thermal barrier materials is also described, including flame retardant polymer, thermal barrier and intumescent coatings. The fire properties of polymer nanocomposite materials are reviewed in Chapter 9 by Dr Dongyan Wang and Professor Charles Wilkie of Marquette University. The chemistry and molecular structure of nanocomposites are introduced, with emphasis given to polymers containing nano-clays. The techniques used to analyse the nanostructure of these polymers are briefly out-lined. The fire reaction properties of many varieties of thermoplastic and thermoset polymers loaded with nano-clays and other nanoparticles that impart improved fire resistance are described, and their flame retardant mechanisms are out-lined. Fire safety standards are enforced on composites in many applications because of their potential fire risk and smoke toxicity. Chapter 10 provides a general review of the fire standards and regulations for composites when used in aircraft, ships, submarines, and other applications. An assessment of the scope and shortcomings of the different fire standards is given, and the impact of the regulations on the application of composites is discussed. The experimental apparatus and test methods used to characterise the fire reaction and fire resistance properties of composites are reviewed in Chapter 11. A variety of methods that range in size from small bench-top techniques to full-scale fire tests are described. The small-scale fire tests include the cone calorimeter, Ohio State University calorimeter and limiting oxygen index test, and these are used for measuring properties such as flammability, heat release and smoke. Medium-scale and large-scale tests for assessing the fire behaviour of composite components, assemblies and structures are also reviewed. These include the intermediate-scale cone calorimeter, DTRC burn through test, furnace fire test, fire-under-load test, single burning item test, corner burn

11 xii Fire Properties of Polymer Composite Materials test, and room fire test. An assessment of the capabilities and limitations of the test methods is given, and the need for the further development of uniform, standardised fire tests is discussed. Chapter 12 gives an overview of the health hazards to humans when exposed to toxic smoke from burning composite materials. The health effects of inhaling fibres, smoke and toxic fumes are described, and safe exposure limits to the main decomposition products are given. Empirical models and experimental apparatus for determining the toxic potency of the gases released from decomposing composites are also reviewed. A brief description of protective clothing and breathing apparatus that should be used when exposed a burning composite material is given. The diverse scope, comprehensive nature and in-depth detail of this book ensures that it will be of great interest to professionals in the polymer and composites industries, fire safety engineers, researchers in the thermal and fire properties of polymeric materials, and the users of composites in the aerospace, marine, civil infrastructure, petrochemical, processing and automotive industries. This book would not have been possible without the effort of many people. The authors are grateful to Dr Pat Potter of the United States Office of Naval Research for the provision of a grant (USONR Award No. N ). AM also acknowledges the support of the Cooperative Research Centre for Advanced Composite Structures Ltd. The authors thank Dr Brian Lattimer (Hughes Associates Inc.) and Ted Campbell (Materials Sciences Corporation) for writing the chapter entitled Fire Modelling of Composites and Dr Dongyan Wang and Professor Charles A. Wilkie (Marquette University) for writing the chapter Fire Properties of Polymer Nanocomposites. Dr Craig Gardiner was a co-author to the chapter Post-fire Properties of Composite Materials. The many discussions with a large number of colleagues working on the fire properties of polymer composites have been invaluable, and special mention of those working on the ONR-funded program on the structural modelling of composites in fire led by Dr Luise Couchman: Zenka Mathys, Dr Stefanie Feih, Dr Yongshu Wu, Dr Jim Lua, Professor George A. Kardomateas, Professor John W. Holmes, Professor Victor Birman, Professor Jack Lesko, Professor Scott Case and Professor Paul DesJardin. The authors also thank the many publishers and colleagues who kindly allowed the reproduction of figures and tables used in this book. The advice and patience of Nathalie Jacombs and Anneke Pot from Springer is gratefully acknowledged, and Dr Henry Li for formatting the book is greatly appreciated. Lastly, we would like to acknowledge the support of our families; only they truly know the amount of time, effort and research given to the writing of this book. Adrian P. Mouritz Melbourne, Australia Arthur G (Geoff) Gibson Newcastle-upon-Tyne, England