Advances in Fire Retardant Materials

A. Richard Horrocks, D. Price

• Publisher: Woodhead Publishing
• Year: 2008
• Print ISBN: 9781845692629
• eBook ISBN: 9781845695071
• Topic: Technology & Engineering
• Subtopic: Industrial Health & Safety
• Index: Technology & Engineering

This important book provides a comprehensive account of the advances that have occurred in fire science in relation to a broad range of materials. The manufacture of fire retardant materials is an active area of research, the understanding of which can improve safety as well as the marketability of a product.The first part of the book reviews the advances that have occurred in improving the fire retardancy of specific materials, ranging from developments in phosphorus and halogen-free flame retardants to the use of nanocomposites as novel flame retardant systems. Key environmental issues are also addressed. The second group of chapters examines fire testing issues and regulations. A final group of chapters addresses the application of fire retardant materials in such areas as composites, automotive materials, military fabrics and aviation materials.With its distinguished editors and array of international contributors, this book is an essential reference for producers, manufacturers, retailers and all those wishing to improve fire retardancy in materials. It is also suitable for researchers in industry or academia. - Reviews advances in improving the retardancy of materials - Addresses key environmental issues - Examines fire testing issues and regulations and the challenges involved

1

Introduction

A.R. Horrocks; D. Price    University of Bolton, UK

Because of the many advances in flame retardant materials made over the past few years, this new book has been assembled to update our previously successful text, Fire Retardant Materials, published in 2001 by Woodhead Publishing and CRC Press LLC. The two books complement each other.

The increasing use of flammable, polymeric materials in domestic, industrial and other situations necessitates the development of means to render them resistant to both the initiation and sustaining of fires. Driving these developments are the annual losses of life and property resulting from fires involving polymeric materials. In the 31 countries covered by CTIF statistics, fires result in the deaths of some 37 000 persons per annum with at least 10 times that number of associated injuries with a total cost of 1% GDP estimated in terms of property loss and replacement, cost of medical services, etc. These data refer to the 2.3 billion inhabitants living in these countries (www.ctif.org, www.ceficefra.org). Approximating the world’s population to over 6 billion, it can be estimated that roughly 6–24 million fires occur in the world annually. These would cause some 100 000 deaths per annum with a cost of about £500 billion. Such data presents an overwhelming case for further development of improved technologies for flame retarding inherently flammable materials. Such developments are often driven by new legislation motivated by either tragic events, e.g. the English Channel tunnel fire in 1996, domestic furniture fires, and skyscraper hotel fires, or environmental concerns, e.g. the dioxan problem. The UK provides an excellent example of this. Following a sequence of domestic fire tragedies over the Christmas period in 1988, the UK government’s introduction of legislation requiring domestic furniture to be flame retarded has resulted in about 140 fewer deaths per year compared to what was previously the case.

This book is structured into three parts. In Part I we have combined those chapters which consider the advances made in fire retardant materials during recent times, whereas in Part II the whole associated area of testing, regulation and assessing the benefits of fire retardant materials is considered. Part III focuses on the major applications of flame retardant materials where the most stringent levels of fire retardant behaviour are demanded and these are often driven by legislation, regulation and/or the specific level of fire hazard associated with the user of these materials.

However, within these three parts there are a number of cross-cutting themes of which the reader should be aware and these fall principally within the areas of the environment, the increasing impact of nanotechnology and the continual development in regulations and legislation.

The major risk regarding the use of flame retardants has been their potential environmental impact which was first raised as an issue in the late 1980s with claims of dioxin formation associated with the incineration of consumer plastic items containing brominated flame retardants. Since this time, there has been a drive to curtail the use of such flame retardants, culminating in bans on the production and usage of all brominated diphenyl species and, more specifically, of penta- and octabromo diphenyl ethers during the 2005/06 period. In parallel and especially in the USA and EU, risk analyses have been and continue to be undertaken on brominated flame retardants generally, with attention especially being given to those in very common use such as decabromodiphenyl ether (decaBDE), hexabromocyclododecane (HBCD) and tetrabromobisphenol A (TBBPA). This has had the consequence of pressure being brought to bear on the manufacturers of consumer goods to remove brominated flame retardants from their products, even if no health or environmental risk has been associated with their use and in spite of the benefits their presence confers in terms of improved fire safety. Chapter 14 by Elmsley and Stevens fully analyses the risks and benefits of using flame retardants in consumer products both qualitatively and quantitatively.

Not surprisingly, these environmental concerns over the use of halogen flame retardant systems have enhanced the need for successful alternatives. The strongest competitors are the systems based on phosphorus. Sergei Levchik and Edward Weil have a wealth of knowledge in this area. Chapter 3 is their up-to-date account of the status of phosphorus flame retardant technology. Particular applications include polycarbonate and blends; polyesters and nylons; epoxy resins; polyurethane foams and polyolefins. Chapter 4 by Wang follows on with a review of the challenges posed by replacing halogen-containing flame retardants and the recent attempts to achieve successful alternatives, which have similarly high efficiencies, without loss in mechanical properties, because of the high concentrations possibly required, as well as associated risks of matrix polymer degradation. He also discusses the important area of attempting to reduce melt-dripping while increasing flame retardancy in thermoplastic polymers.

Within certain applications, such as textiles, the proximity of the product to the consumer whether as a clothing item in intimate contact with the skin or as furnishing fabrics located in closed domestic environments, has posed considerable environmental concerns which has have received considerable attention as noted by Elmsley and Stevens (Chapter 14) and this area is addressed in detail by Wakelyn in Chapter 8.

End-of-life disposal strategies also pose environmental challenges and with the ever expanding use of polymeric materials generally, the need for suitable, environmentally friendly technologies for their recycling and disposal becomes paramount. The presence of flame retardant species both as additives and as components of polymeric chains within such a material adds further complication to this problem. Chapter 9 by Casrovinci, Lavaselli and Camino provides a full account of the problem and potential solutions. It is an excellent starting point from which to instigate an investigation of this area.

The second major cross-cutting interest of the flame retardant science community during the last ten years has been the observation that inclusion of nanoparticulate species, when introduced into most polymer matrices, can significantly improve their fire performance, often noted as a reduction in the cone calorimetrically determined values of peak heat release rate (PHRR). However, when present alone these do not confer flame retardant properties in terms of increasing ignition times and/or reducing burning rates and burning times. In the presence of conventional flame retardants, however, they may show remarkable synergies, thereby enabling overall reduced levels of flame retardant to be used in a given polymer in order to achieve a desired level of flame retardancy. Recent developments in this whole area are intensively reviewed by Wilkie in Chapter 5 in terms of the history and nature of nano-composite polymers but also with regard to the effectiveness of different nanoparticle species, especially in combination with conventional flame retardants, as novel flame retardant components. The proposed mechanisms of action are also reviewed and discussed. While commercial applications of nanocomposite-based flame retardant polymers have been few during the last 10 years, Horrocks, in Chapter 6, reviews their potential in bulk, film, fibre, composite and foam applications and signals increasing interest and an expectation that their commercial exploitation will expand in the near future. It is in this emerging nanotechnological area where benefits of the combined improvements in mechanical properties and fire performance at relatively low cost cannot be ignored.

Thirdly, public concern over fire safety has resulted in legislation to control the flammability specification/requirements for polymeric materials for domestic and industrial use. This in turn has necessitated Standard Fire Tests to ascertain the suitability for use of the many polymeric materials in the market place. Part II contains four chapters which deal with subject matter in great detail. Janssens provides a tester’s viewpoint. Type I and II flammability tests are described in detail whilst the challenges in assessing material flammability are discussed in detail as are the uses and limitations of fire testing. This is complemented by Chapter 11 where Hull gives an alternative but complementary view with an analysis of reaction to fire tests and the assessment of fire toxicity. He completes his review with a discussion of the prediction of fire behaviour from material properties and models of fire growth. In Chapter 12, Troitzsch discusses the status and trends in fire safety regulations and testing. Finally, Margaret Simonson in Chapter 13 provides an account of life cycle analysis, i.e. production to disposal, of flame retarded consumer products. This is illustrated with reference to case studies concerning TV sets, cables and furniture.

The above themes are continually addressed in those chapters dealing with applications. Advances at the research level in improving the flame retardancy of natural and synthetic fibres and textiles as a whole are considered in detail by Bourbigot in Chapter 2. Within this, the considerable research into the application of nanoparticulates both within fibres and fabric coating formulations as well as the development of fabric structures having the highest levels of fire performance are also detailed. While environmental challenges are introduced here, they are more fully explored in Chapter 8 by Wakelyn, as mentioned above. The particular importance of textile coatings and laminates has been addressed by Horrocks in Chapter 7, where once again the challenges posed by both environment and nanotechnology are included.

Those textiles requiring the highest levels of flame retardancy and fire performance are usually those required by the civil emergency and defence organisations. Mäkinen, in Chapter 17, considers firefighters’ protective clothing in terms of the different tasks undertaken by different systems, the requirements for fire and heat protection, the associated clothing design and materials factors and the methods used to assess performance. In a similar fashion, in Chapter 18 Nazare considers the fire hazards present and fire protection levels required in military fabrics, the clothing requirements for personnel, existing flame retardant solutions, the types of military clothing and, finally, the testing, performance standards and durability requirements.

The not-unrelated application areas of textile and fibre-reinforced composites are described by Kandola and Kandare. Here the key features required of composites having improved fire resistance, the different types of polymer, metal and ceramic matrix composites and the principal issues regarding the fire performance requirements for the different sectors of aerospace, automotive, rail and marine transport are explained. This is complemented by a discussion of the flammability of composites and their constituents in general, with a focus on both current and potential flame retardant solutions. Degradation of mechanical properties of composites during a fire is becoming of increasing importance and so receives attention here.

Within the transport sectors, regulations are often of paramount importance and also international in character. However, in the automotive sector, while there are no specific international regulations in force regarding aspects of component fire retardancy, the global nature of the industry has caused most major manufacturers to adopt various versions of the US FMVSS 302 standard, which is a rather mild horizontal burn test method for all textile components within the passenger compartment. In addition to textiles, such as seating fabrics and padding and interior décor, linings and carpets, manufacturers of modern cars and road transporters make extensive use of polymer materials, e.g. in panelling, together with the current development of suitable light but strong plastics and composites for use in engines and engine compartments. In the USA, some 350 000 or so road vehicle fires cause some 470 deaths, 1850 injuries and over $1.3 billion loss in property (see News 6-2002 on www.ceficefra.org) per annum. Development of suitable flame retarded materials is essential to improve the fire safety of automotive vehicles. Hirschler’s chapter (Chapter 16) provides an excellent account of this area dealing with the regulation requirements 2007 draft of guide NFPA 556 and possible alternative approaches.

However, the maritime and aerospace transport sectors are far more regulated with regard to fire performance requirements. For instance, the construction and fittings of naval ships and maritime vessels make extensive use of combustible materials and components. Such vessels are vulnerable to exposure to fire, particularly in a war situation. Thus there is a need for suitable flame retarded polymeric materials for use in such vessels. In Chapter 19 Sorathia gives a full account of the regulations identifying the requirements of suitable materials, methods for reducing flammability, test methods and fire performance.

In a similar manner to the maritime industry, metallic structures in aircraft are increasingly being replaced by polymeric materials and especially composites in order to lose weight and thus reduce fuel requirements. Plastics and textiles are also extensively used throughout the cabin areas. Fire safety is designed into aircraft to prevent in-flight fires and mitigate post-crash fires, which account for about 20%  of the fatalities resulting from airplane accidents. In the final chapter (Chapter 20) Richard Lyon provides a full account of this developing area of flame retardant materials as well as considering ways in which it will develop in the future.

Part I

Advances in fire retardant materials

2

Flame retardancy of textiles: new approaches

S. Bourbigot Ecole Nationale Supérieure de Chimie de Lille (ENSCL), France

Abstract

Three approaches can be considered to reduce the flammability of textiles: (i) to use inherently flame retarded textiles comprising the so-called high performance fibres; (ii) to chemically modify existing textiles; (iii) to incorporate flame retardants in synthetic fibres and/or to make specific surface treatment. Those three aspects will be considered in this chapter focusing our discussion on the new directions and concepts emerging in this field. The chapter is organized in five sections presenting the recent standards developed to assess the flame retardancy of the textiles, the flame retardant fibres (natural, synthetic and man-made fibres) and future trends.

Key words

flame retardancy

flame retardant

textile

synthetic fibres

natural fibres

2.1 Introduction

Fire i...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• Contributor contact details
• 1: Introduction
• Part I: Advances in fire retardant materials
• Part II: Testing, regulation and assessing the benefits of fire retardant materials
• Part III: Applications of fire retardant materials
• Index