Characteristics and Analysis of Non-Flammable Polymers [1 ed.] 1847354661, 1847354688, 9781847354662, 9781847354686

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Characteristics and Analysis of Non-Flammable Polymers

T.R. Crompton

Characteristics and Analysis of Non-Flammable Polymers T.R. Crompton

A Smithers Group Company Shawbury, Shrewsbury, Shropshire, SY4 4NR, United Kingdom Telephone: +44 (0)1939 250383 Fax: +44 (0)1939 251118 http://www.polymer-books.com

First Published in 2013 by

Smithers Rapra Technology Ltd Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK

©2013, Smithers Rapra Technology Ltd

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ISBN: 978-1-84735-466-2 (hardback) 978-1-84735-467-9 (softback) 978-1-84735-468-6 (ebook)

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reface

In recent years there has been an increasing demand for fire retardant versions of a range of plastics. Such applications that come to mind are in the areas of fire retardancy in vehicles, aircraft, manned space vehicles, marine and industrial applications such as electronics and a wide range of applications in the building industry including roofing and interior walls. There is also a need for fire-retardancy in domestic applications such as furniture, clothes, bedding, upholstery and electrical goods. Fire retardancy in polymers can be achieved by one of three ways: Firstly there are forms of polymers, such as polytetrafluoroethylene, which are intrinsically fire retardant. The second types are rendered fire retardant by the inclusion of a suitable additive in the formulation. These include additives based on antimony, bromine, nitrogen, phosphorus and silicon. An essential requirement for fire retardant polymers used in enclosed spaces is that they do not release any toxic products upon combustion. However, antimony containing additives are going out of favour due to the release of toxic antimony volatiles upon combustion. The properties and mechanisms by which these polymers operate are discussed in Chapters 1 and 6. The third group of polymers consist of intumescent materials and these are being increasingly used as a means of imparting fire retardancy in polymers and this is discussed in Chapter 7. Methods for delivering the fire retardant properties of polymers are reviewed in Chapter 2 and Appendices 1, 2 and 3. Chapters 3, 4 and 5 are concerned with the uses of fire retardant polymers in a wide range of applications. The book will be of interest not only to those working in industry but also to design engineers and workers in the polymer fabrication industries. T Roy Crompton January 2013

iii

Characteristics and Analysis of Non-Flammable Polymers

iv

C

ontents

1

Fire Retardant Mechanisms in Polymers .................................................... 1 1.1

Mechanisms .................................................................................... 1

1.2

Interference in Combustion Process ................................................ 3

1.3

2

1.2.1

Heat Shielding ................................................................... 3

1.2.2

Dilution of Combustion Gases ........................................... 3

1.2.3

Reduction in Overall Heat Production ............................... 4

1.2.4

Dust or ‘Wall Effect’ .......................................................... 4

1.2.5

Chemical Inhibition: Free Radical Effect ............................ 5

1.2.6

Ionic Mechanism Hypothesis ............................................. 6

Types of Fire Retardant................................................................... 6 1.3.1

Halogen Type..................................................................... 6

1.3.2

Phosphorus-halogen Type .................................................. 7

1.3.3

Nitrogen Type .................................................................... 7

1.3.4

Antimony Oxide Synergist ................................................. 7

Test Methods for Fire Retardancy ............................................................ 11 2.1

Flame Propagation ........................................................................ 14

2.2

Flame Spread ................................................................................ 14

2.3

Smoke Production ......................................................................... 15

2.4

Toxic Gas Generation ................................................................... 16

2.5

Flame Testing ................................................................................ 17

2.6

Limiting Oxygen Index ................................................................. 17

2.7

Oxygen Consumption Cone Calorimetry ...................................... 20

2.8

Pyrolysis – Gas Chromatography – Mass Spectrometry ................ 28

v

Characteristics and Analysis of Non-Flammable Polymers 2.9 3

Laser Pyrolysis – Mass Spectrometry............................................. 34

Building Construction Materials, Industrial Applications and Furnishings 45 3.1

Building Applications .................................................................... 45 3.1.1

Building Wrap.................................................................. 47

3.1.2

Roofing ............................................................................ 47

3.1.3

Air Handling Ducts .......................................................... 48

3.2

Harmonisation of Fire Safety Assessments .................................... 50

3.3

Mining Applications ..................................................................... 50

3.4

Furnishing Materials ..................................................................... 53

4

Applications of Fire Retardant Polymers: Electrical Applications ............. 59

5

Applications of Fire Retardant Polymers: Transportation Applications .... 69

6

5.1

Motor Vehicles.............................................................................. 69

5.2

Railway Vehicles ........................................................................... 69

5.3

Marine Applications ..................................................................... 70

5.4

Aircraft ......................................................................................... 72

Flammability Characteristics .................................................................... 75 6.1

6.2

6.3

Carbon Hydrogen Polymers .......................................................... 75 6.1.1

Polyolefins ....................................................................... 75

6.1.2

Polystyrene ...................................................................... 76

6.1.3

Polyarylates ..................................................................... 76

Carbon – Oxygen Containing Polymers ........................................ 77 6.2.1

Epoxy Resins ................................................................... 77

6.2.2

Polyesters ......................................................................... 80

6.2.3

Polycarbonates ................................................................. 82

6.2.4

Phenolic Resins ................................................................ 86

6.2.5

Polyketones ...................................................................... 86

Chlorinated Polymers ................................................................... 87 6.3.1

vi

Chlorinated Polyethylene ................................................. 87

Contents

6.4

7

6.3.2

Chlorosulfonated Polyethylene ........................................ 87

6.3.3

Polyvinylchloride ............................................................. 87

Nitrogen Containing Polymers ...................................................... 88 6.4.1

Polyurethane .................................................................... 88

6.4.2

Polyamides ....................................................................... 90

6.4.3

Polyimidoamide Nanocomposites .................................... 91

6.5

Phosphorus and Silicon Containing Flame Retardants .................. 91

6.5

Silicon Containing Flame Retardants ............................................ 95

6.6

Review - Fire Retardancy of Polymers........................................... 96

Intumescent Polymers............................................................................. 109 7.1

Intumescent Polypropylene and Polyethylene .............................. 109 7.1.1

8

Nanoplatelet/Nanofibre Modified Polymer Matrices ...... 111

7.2

Polypropylene-Polyamide-6 ........................................................ 112

7.3

Intumescent Polystyrene and Polymethyl Methacrylate ............... 113

7.4

Intumescent Ethylene-Vinyl Acetate Copolymer .......................... 114

7.5

Intumescent Styrene-Butadiene Copolymer ................................. 115

7.6

Intumescent Polyisocyanurate Polyurethane Foams..................... 115

7.7

Intumescent Siloxone – Polyurethane Copolymers ...................... 119

7.8

Fire Retardant Additives ............................................................. 119

Effect of Reinforcing Agents, Fillers and Flame Retardants on Polymer Properties ................................................................................. 125 8.1

Flammability Characteristics ....................................................... 125

8.2

Effect on Physical Properties ....................................................... 127 8.2.1

Mechanical Properties .................................................... 127

8.2.2

Electrical Properties ....................................................... 131

8.2.3

Thermal Properties ........................................................ 131

Appendix 1 Particular Test Procedures .............................................................. 133 Appendix 2 Standard Test Procedures ............................................................... 137

vii

Characteristics and Analysis of Non-Flammable Polymers Appendix 3 Standard Fire Retardancy Specifications Listed Under Index Type and Application of Polymer under Test ......................................................... 143 Abbreviations .................................................................................................... 149 Index .............................................................................................................. 155

viii

1

Fire Retardant Mechanisms in Polymers

1.1 Mechanisms Several workers have reviewed the mechanisms by which polymers can be rendered more flame retardant chiefly by the incorporation of flame retardant additives in their formulation [1-5]. There has been considerable progress in detailed evaluation of a large number of flame-retardants in a variety of plastics. Many useful reviews of results have been published, e.g., ‘self-extinguishing polyester resins’ [6]. At the same time, the number of flame-retardant patents has grown enormously, especially in the United States [7, 8], which suggests an intensification of industrial interest in this field which must have run parallel with advances in legislation on this subject. However, most of the information, is still largely empirical. There are still not enough physico-chemical data such as the heat of combustion of specific plastics (with and without flame-retardants); the rate of evolution of this heat; the nature of the pyrolysis products; or the effect specific additives may have on the course of degradation of the polymer. These are all features, which deserve far more systematic attention if a full understanding of flame-retardant mechanisms is to be reached. Jolles and Jolles [5] outlined the requirements for starting a fire by the combustion process: • Fuel, • Oxygen (or oxidising agent), and • Ignition source. To maintain the fire without continued application of the ignition source it is necessary: • That fuel and oxygen diffuse to the combustion zone, or • That the combustion zone travels and at the same time,

1

Characteristics and Analysis of Non-Flammable Polymers • That the heat produced by the combustion is suficiently in excess of heat losses to sustain the process. The sequence of events in the combustion of a solid polymer may be described as: Heat from an external source reaches the polymer (by conduction or radiation) and low-temperature pyrolysis reactions begin to take place in which oxygen participates, giving rise to volatile, flammable products which diffuse to the surface where they mix with air. If heating is continued and the temperature reaches a critical value, ignition will take place depending on the vapour pressure of the volatile reactants and on the temperature; phenomena such as ‘cool flames’, ‘delayed ignition’ and ‘two-stage ignition’ may be observed. If pyrolysis products and oxygen continue to reach the combustion zone and if the energy liberated by combustion is sufficiently in excess of heat losses to maintain the ignition temperature, the process becomes self-perpetuating until nearly all the fuel or oxygen has been consumed. At the same time, pyrolysis within the solid polymer creates increased porosity to oxygen and to volatile products, while charring or carbonisation gives a more heatabsorbent surface. A complex sequence of chemical reactions has been postulated for the oxidation of hydrocarbon polymers. Most of the evidence supports a free-radical chain mechanism with typical steps of initiation, propagation, chain branching, termination and inhibition, parallel to the similar mechanisms postulated for volatile hydrocarbons [9-11]. The main oxidising species are O2 molecules, oxygen atoms and OH and OOH radicals. The last two are particularly important at low temperatures. Oxygen atoms become important only as di-radical species in chain branching at high temperatures, for example:

O + H → OH + H 2

(1.1)

Similar schemes of propagation or chain branching have been reviewed elsewhere [12]. In addition to the volatile pyrolysis products there remains the charred carbonaceous solid residue, which continues to burn by glowing and so continues to generate heat. 2

Fire Retardant Mechanisms in Polymers The inhibition of polymer oxidation by typical chain termination adds to the evidence for the free-radical chain mechanisms [13]. Inhibition can be considered to be a specialised termination reaction in which propagating radicals are converted to inert or less reactive products by reaction with the inhibitor. This can happen at several places in the scheme or by oxidative degradation. The probability of flame propagation may be lowered either by increasing heat losses or by affecting the combustion reaction by adding inhibitors or by varying the composition of the combustion mixture [14, 15].

1.2 Interference in Combustion Process It becomes apparent that the combustion process could be susceptible to interference in a number of ways, any one of which could have a retarding effect.

1.2.1 Heat Shielding Physically covering the polymer with a reflecting intumescent coating as a heat shield may provide an adequate barrier to heat transfer and thus, prevent the initial lowtemperature degradation of the polymer leading to ignition [16]. Phosphorus compounds are believed to act partly in this way following pyrolysis firstly to phosphoric acid and then to metaphosphoric acid, thus polymerising to a very stable form. The flame-shielding effect is, therefore, attributed to a protective layer of polymeric metaphosphoric acid. Experimentally an optimum concentration of phosphorus has been found in rigid urethane foams in the region of 1.5−2.0%; this is explained by assuming the presence of a ‘monomolecular’ protective layer whose effectiveness cannot be improved by increasing the thickness of the coating [17].

1.2.2 Dilution of Combustion Gases It has been shown that the addition of 38 mole% nitrogen to any air-methane mixture makes the mixture non-flammable. Such an inert diluent is believed to act as a heat sink; the flame temperature is reduced at a faster rate than heat is generated, resulting in cooling and eventual extinction of the flame [18]. Flame-retardant additives that degrade to give a non-combustible gas blanket (as distinct from other mechanisms) are rare. Flame-resistant polycarbonates evolve carbon dioxide, among other gases, by breakdown of the carbonate structure.

3

Characteristics and Analysis of Non-Flammable Polymers It has been suggested that materials, which decompose to give Lewis acids, fall into this category of flame-retardant mechanisms [19]. The exclusion of oxygen or of fuel gas from the combustion zone can also be considered under this heading.

1.2.3 Reduction in Overall Heat Production An overall reduction in heat production may be obtained by incorporating compounds in the polymer compounds which decompose endothermically, i.e., make a negative contribution to the overall thermal yield. It is, after all, the heat of combustion of the plastics, which sustains the propagation of the flame by bringing about further pyrolysis adjacent to the combustion zone. The use of halogenated monomers or reactive intermediates can bring about a lowering of heat of combustion. For example, heat capacity and heat of combustion have been determined for copolymers of styrene with polyesters whose thermodynamic properties were known: introduction of chlorine into the polyester molecule lowered the heat of combustion. The temperatures of self-ignition of polyesters containing 17.5% and 23.7% chlorine were 580 ºC and 650 ºC, respectively. The parallelism of heat capacity and heat of combustion with ‘combustibility’ indicates that the combustibility of polymers could be estimated from calculated theoretical values [20]. The same overall result of lowering heat production can be observed where there is a possibility of endothermic interactions between decomposition products.

1.2.4 Dust or ‘Wall Effect’ The flame-retardant action of inert dust is interesting. Heat is consumed in heating dust particles, leading to lowering of temperature and consequently to retardation of the flame, i.e., a wall effect. With a sufficient concentration of dust in the gas, the flame cannot propagate. This effect has been widely applied when extinguishing fires. It is possible that in addition to heat loss to the dust, heterogeneous chain breaking takes place by adsorption of active species on the surface of dust particles. Such an effect from heterogeneous catalysis could certainly be expected when the dust is that of metals and certain oxides with a high capacity for adsorption of free atoms and radicals [14]. At the wall of a vessel (or at the surface of a dust particle) competing interactions may take place.

4

Fire Retardant Mechanisms in Polymers As the HO2 radical is relatively unreactive compared to H, HO and O it is much more likely than these to diffuse to the ‘wall’ or surface and be deactivated there. It has been suggested that when antimony oxide is used as a synergist with organic halogen compounds, it is first converted to antimony trihalide by hydrogen halide. The antimony is then decomposed in the combustion zone giving a ine fog of antimony oxide dust, the flame-retardant effect being partly due to the dust effect [16].

1.2.5 Chemical Inhibition: Free Radical Effect These chemical inhibition - free radical effects are perhaps the most important of the flame-retardant mechanisms, not only because of the relatively small proportion of chemical flame-retardant which will give a large effect, but also because it sheds some light on the reactions which take place in flames and provides further evidence for the free-radical chain mechanism of flame propagation. In contact with inert gases, which have a perceptible effect only when they are present in proportions, which appreciably change the specific heat of the mixture, certain substances (e.g., halogens or halogen derivatives) strongly affect flame velocity in concentrations as low as fractions of 1%. As such small additions do not appreciably change the specific heat or thermal conductivity of the mixture, it seems reasonable to suppose that they have a direct effect on the course of the reaction [14]. Thus, the inhibiting effect of halogen derivatives in hydrocarbon flames is believed to consist in decreasing the concentration of active centres, mainly the H atom, which is equivalent to a chain-breaking reaction since it results in very active H atoms being replaced by the much less active R or X. In the case of –OH, the net result is to replace OH by a less active species Br or R and therefore to slow the reaction. According to Rosser [21] the inhibitory action of bromine and its compounds is thought to involve both the Br atom and the HBr, although the halogen acid is believed to be the active species. HBr is probably effective in reducing the concentration of radicals such as OH and H, which are involved in the oxidation of CO. The bromine atom served to regenerate HBr. In support of Rosser’s hypothesis are several experimental observations [21]. For example, the OH radical concentration is lower in inhibited than in uninhibited flames. The degree of inhibition produced by bromine compounds is the same as that provided by an equivalent amount of HBr. With certain lame systems such as methane-NO2, where the H, OH and O radical are not involved in chain propagation, the halogen compounds are not effective.

5

Characteristics and Analysis of Non-Flammable Polymers

1.2.6 Ionic Mechanism Hypothesis Creitz has proposed a different mechanism of lame inhibition based on an ionic mechanism [22]. He found that methyl bromide and bromotrifluoromethane were more effective inhibitors when added to the oxygen side of a hydrocarbon diffusion flame than when added to the fuel side. He stated that (unlike the mechanism proposed by Rosser which involves chain termination by halogen atoms) ‘it seems likely that the inhibition reaction takes place in some particular region of the reaction zone, which requires that the inhibitor be stable enough to reach the area where its reaction takes place, but not so stable that it cannot react after it gets there’. According to Creitz [22] an ionic mechanism is involved. In support of this hypothesis it has been shown that lames are displaced by electric ields. If ions (known to be present in flames) were not involved to a major extent, their displacement by the field should not significantly affect the position of the flame. Some halogen compounds are known to capture electrons and this property is directly related to their effectiveness in inhibiting flames. The inability of halogen compounds to inhibit methane-NO2 lames can be attributed to the fact that NO2 can compete more favourably for electrons than the halogen compound.

1.3 Types of Fire Retardant Different types of compounds have been used as flame retardant polymers. These will be in considered in detail in the next sections.

1.3.1 Halogen Type The flame-retardant properties of bromine and chlorine compounds are well known. Their effectiveness in a given situation appears to depend very much on the right choice of flame-retardant compound. Since these halogens are believed to exert their effect mainly in the form of hydrogen halide molecules, a great deal depends on the ease with which HCl or HBr is produced from the lame-retardant molecule under pyrolysis conditions. The flame-retardant compound must be stable enough to stand up to processing with the polymer, but not too stable to give up its halogen when the polymer burns. In comparing the performance of bromine and chlorine compounds, a fundamental feature influencing the comparison is the strength of the respective carbon-halogen bond. In all analogous combinations the chlorine is more irmly bound.

6

Fire Retardant Mechanisms in Polymers In some cases this works in favour of chlorine: in the aliphatic series the chlorine compounds have the right degree of stability to be commercially useful, while in aromatic combination bromine has the advantage in performance to an extent which outweighs its greater cost. It seems reasonable to expect, however, that a mixture of bromine and chlorine compounds or a compound containing both halogens in the same molecule would be most effective, giving rise to a controlled – perhaps stepwise – release of the two halogens. It is possible that the apparent synergism between chlorine and bromine is simply due to a better overall utilisation of a total available halogen.

1.3.2 Phosphorus-halogen Type The use of phosphorus and bromine in the same molecule as, for example, tris(2,3dibromopropyl)phosphate is perhaps the most useful approach, as it helps to get the best possible utilisation of the halogen when the flame-retardant molecule breaks down. At the same time there is strong evidence of synergism when mixtures of phosphorus and bromine compounds are used.

1.3.3 Nitrogen Type Horacek and Grabner [23] have reviewed the advantages of nitrogen compounds as flame-retardants. They and their gases or vapours evolved during combustion have low toxicity, are less corrosive than hydrogen chloride or hydrogen bromide and show low evolution of smoke. Nitrogen-based flame-retardants do not interfere with stabilisers, which are added to plastics. Flame retarded plastics based on nitrogen can be recycled because the nitrogen flame retardants have high decomposition temperatures and if they are disposed of in landfill sites, they act as long-term fertilisers. They are more efficient than the metallic hydroxides of the plastics.

1.3.4 Antimony Oxide Synergist Antimony oxide is unique in its activity as a synergist with halogen compounds. This may be due to the ease with which it reacts with hydrogen halides to form volatile halides, which can pass through a number of decompositions and re-combinations (some of which are endothermic) and finally decompose at higher temperatures to give the oxide and release the halogens.

7

Characteristics and Analysis of Non-Flammable Polymers Houde [24] has investigated the composition and mode of operation of flame retarding additives based on antimony, bromine, chlorine, nitrogen, and phosphorus. Hirth and co-workers [25] have discussed the environmentally safe way of disposing of plastics containing halogens and nitrogen. Incineration is not always appropriate. Thus, in the elimination of chlorine containing organic waste materials, the formation of hydrogen chloride, chlorine and dioxins must be reckoned with, whereas nitrogen oxide may also be produced on the destruction of waste materials containing nitrogen. New possible conversion processes are presented: pressure hydrolysis in subcritical and supercritical water and the supercritical water oxidation. These processes are used for the degradation of monomers, polymers and additives. When alkaline hydrolysis of halogenated polymers is carried out in the supercritical range, e.g., at 500 °C, over 98% of the organically bonded chlorine in the aqueous phase is found. In this process the principal polymer chain is also decomposed. Under supercritical water conditions it is also possible to oxidise additives from plastics such as fire retardants. Mans [26] considered the environmental aspect of fire retardant additives used in the manufacture of polymers. The gaseous phase was examined for the mechanism of action for organic halogenated derivatives. Discussion is focused on avoiding combustion in inflammable gases that are released from a material when it is subjected to a source of heat so as to release free, high-energy hydroxyl and hydrogen radicals. Also reviewed are phosphorus-derived flame-retardants along with related chemical structures. The effect of fire-retardant additives on the injection moulding of polymers has been discussed [27]. La Costa [28] has considered the use of smoke depressants and other additives to reduce smoke generated during the combustion of plastics.

References 1.

L. Costa, J-M. Catala, K.M. Gibov, A.V. Gribanov, S.V. Levchik and N.A. Khalturinskij in Fire Retardancy of Polymers, Eds., M. Le Bras, G. Camino, S. Bourbigot and R. Delobel, Royal Society of Chemistry, Cambridge, UK, 1998, p.76.

2.

E.L. Morrey, Journal of Thermal Analysis and Calorimetry, 2003, 72, 3, 943.

3.

F.J. del Portillo, Plast 21, 1996, 55, 139.

4.

F. Catalina, C. Peinado, J.L. Mateo, P. Bosch and N.S. Allen, European Polymer Journal, 1992, 28, 12, 1533.

8

Fire Retardant Mechanisms in Polymers 5.

Z.E. Jolles and G.I. Jolles, Plastics and Polymers, 1972, 40, 150, 319.

6.

R.C. Nametz, Industrial & Engineering Chemistry, 1967, 59, 5, 99.

7.

M.W. Ranney in Flame Retardant Polymers, Noyes Data Corporation, Park Ridge, NJ, USA, 1970.

8.

M.W. Ranney in Fire Retardant Textiles, Noyes Data Corporation, Park Ridge, NJ, USA, 1970.

9.

J.L. Bolland, Quarterly Reviews, 1949, 3, 1, 1.

10. C.E. Frank, Chemical Reviews, 1950, 46, 1, 155. 11. L. Bateman, Quarterly Reviews, 1954, 8, 2, 147. 12. W.L. Hawkins and F.H. Winslow in Chemical Reactions of Polymers, Ed., E.M. Fetters, Interscience Publishers, New York, NY, USA, 1964, p.1055. 13. D.K. Taylor, Transactions and Journal of the Plastics Institute, 1960, 28, 170. 14. V.N. Kondrat’ev, Chemical Kinetics of Gas Reactions, Pergamon Press, London, 1964. 15. Y.B. Zel’dovich, Theory of Combustion and Detonation of Gases, Academy of Science, Moscow, USSR, 1944. 16. W.G. Schmidt, Transactions and Journal of the Plastics Institute, 1965, 33, 247. 17. H. Piechota, Journal of Cellular Plastics, 1965, 1, 186. 18. R.F. Simmons and H.G. Wolfhard, Transactions of the Faraday Society, 1955, 51, 1211. 19. R.H. Dahms in Fire Protection Manual for Hydrocarbon Processing Plants, Ed., C.H. Vervalin, Gulf Publishing Company, USA, 1962, p.132. 20. I.M. Al ‘Shits, N.M. Grad and E.I. Elisa, Zhurnal Prikladnoi Khimii, 1961, 34, 1857. 21. W.A. Rosser, Mechanism of Flame Inhibition, Final Report of Contract No. DA-44-009-ENG 2863, Department of Agriculture, 1958.

9

Characteristics and Analysis of Non-Flammable Polymers 22. E.C. Creitz, National Bureau of Standards Report No.6588, Gaithersburg, MD, USA, 1959. 23. H. Horacek and R. Grabner, Polymer Degradation and Stability, 1996, 54, 2-3, 205. 24. P.J. Houde, Plastnytt, 1976, 11, 4. 25. T. Hirth, G. Bunte, N. Eisenreich K. Krause and R. Schweppe in Proceedings of the Conference R’95 - Recovery Recycling, Re-Integration, Volume IV: Chemical Processes, Biological Processes, Hospital Waste, Geneva, Switzerland, 1995, p.14-21. 26. V. Mans, Revista de Plasticos Modernos, 2003, 86, 569, 396. 27. J. Johnson, Injection Molding, 1999, 7, 4, 108. 28. J.M. La Costa, Revista de Plasticos Modernos, 1991, 62, 63.

10

2

Test Methods for Fire Retardancy

The progress of a fire is often divided into three phases consisting of: (a) Ignition and early development, (b) Total involvement, and (c) Fire recession and extinguishing. The temperature profile of such processes is depicted schematically in Figure 2.1.

b

c

Flash-over

Fire room-temperature (°C)

a

Burn time (min)

Figure 2.1 Temperature profile of combustion of polymer. Reproduced with permission from T.R. Crompton, Polymer Reference Book, 2006, p.496. ©2006, Smithers Rapra Technology Ltd

The fire characteristics of a material are characterised by ease of ignition, contribution to flame spread and heat contribution as well as other factors generally associated

11

Characteristics and Analysis of Non-Flammable Polymers with fires, including smoke density and toxicity and corrosiveness of the combustion by-products. Fire behaviour, however, cannot be considered a material property because it is markedly affected by both material and environmental factors. These include the distribution of material in the room, material geometry and other physical factors, temperature history, thermal conductivity, intensity and type of ignition source, exposure time to the ignition source, integration of the material and ventilation effects [1-3]. The varying nature of the fire risk situation and the influence of materials and environmental factors make it very difficult to establish tests and ratings criteria that would generally be applicable. That is, no doubt, one of the main reasons that many different tests have been developed in research and industry and by regulatory agencies. Many of these procedures, which are in part material-specific, serve well as quality control or developmental guides. The results obtained from within the regime of a test standard are, at best, of limited use in drawing conclusions concerning the performance in real fire situations [4]. However, one must ensure that the environmental conditions adequately simulate the fire risk situation of concern. The risk assessment must differentiate between the production storage and enduse applications. Different risks in production are often due to the amounts of combustible material. The end-use application, transportation, construction, furniture, or furnishings all have a major impact on determining risk. Duplication of natural ignition sources such as cigarettes, sparking contacts and overheated wiring are a first step towards proper applications and risk-oriented testing. Test methods used by various official bodies are reviewed in Table 2.1 which are detailed in Appendix 2. Portillo [6] has reviewed methods for flammability testing. Small laboratory tests, for example, oxygen index test (OIT) [6], Setchkin test or similar tests under certain circumstances provide a means for production quality control. Their results can only be applied towards the characterisation of fire risk assessment if it can be demonstrated that the test adequately simulates the actual fire situation.

12

Test Methods for Fire Retardancy

Table 2.1 Instrumentation available from ATS FAAR for testing properties of polymers Method Flammability by glow wire

Test suitable for ATS FAAR apparatus code meeting following standards number 10.05300 DIN

Rate of burning of rigid specimens exposed to 10.05000 ignition flame of 45º

ASTM D635 [5]

Oxygen index

10.04070 10.04050

DIN ASTM D2863 [6] BS CEI

Ignition properties of plastics

10.04020

ASTM

Incandescence resistance of rigid plastics in horizontal position

10.04000

DIN ASTM CEI UNI

Smoke density combustion of materials

10.05470

ASTM

Resistance to combustion of materials used inside automotive vehicles

10.05600

DIN FED Fiat ISO

Fire resistance of building materials

10.05200

ISO

Flame resistance of vertical specimens (TGA can be used to measure this property)

10.05050

DIN UNI

Fire reaction of specimens exposed to radiant heat

10.05020

ISO

Flammability test

10.05454

UL 1581 [7]

Flammability test

10.5700

UL 94 [8] UL 60950 [9]

Burning rate and flame resistance of rigid insulating materials

10.05400

ASTM D635 [5] UL 94 [8]

Response of plastics to ignition by small flame 10.05500 i.e., flash ignition

ASTM UL

Fire reaction of upholstered furnishings

CSA

10.0550

TGA: Thermogravimetric analysis Reproduced with permission from T.R. Crompton, Polymer Reference Book, Smithers Rapra Technology Ltd, Shrewsbury, UK, 2006. ©2006, Smithers Rapra Technology Ltd

13

Characteristics and Analysis of Non-Flammable Polymers The small laboratory test previously designated ASTM D1692 [10] was abandoned without replacement as a consequence of the 1978 Federal Commission action. As part of the UL 94 [8] test procedure (Table 2.1), this test was used to determine classes of fire retardants (FR). The laboratory procedure consists of exposing a test specimen to a Bunsen burner flame filled with a wing tip flame spreader. The rate and extent of burning were measured. The OIT [6] measures the oxygen/nitrogen concentration needed to support combustion of a test specimen. The specimen is positioned vertically and ignited at the top. Results from such small laboratory tests are, by definition, not suitable for drawing conclusions in a real fire situation. Enriched oxygen environments are found in the space industry. In such cases, the OIT could be used to study and draw conclusions about the ignition phase from ignition sources of low intensity.

2.1 Flame Propagation Flame propagation falls under ASTM C1166 [11]. The test is run on elastomeric materials employed in parts having surface areas of 100 cm2. This standard has been used in testing parts such as window gaskets, door housings, diaphragms, and roof mats. Flame propagation is the extent to which flame spreads along a material when exposed in heat and flame. Under ASTM C1166 [11] guidelines for both cellular and dense elastomers require testing samples that are 1.25 × 2.5 × 45 cm. The standard requires that the cellular and dense elastomers are exposed to a Bunsen burner with a specific flame for 5 and 15 minutes, respectively. In either case, the flame must not spread more than 10 cm.

2.2 Flame Spread This is an assessment of the rate at which a flame travels along the length of a horizontal rectangular specimen. The assessment is not intended to be a measure of the performance of a material in actual fire conditions. An excellent rating indicates low flame spread. A very poor rating indicates considerable flame spread. Flame spread flammability evaluates how far away from the ignition source a flame travels across a liquid or solid surface. The test is carried out in accordance with ASTM E162 [12]. Only flexible cellular foams are tested using a variant of the method ASTM D3675 [13].

14

Test Methods for Fire Retardancy The flame spread index (Is) has traditionally indicated a material’s surface flammability. The Is terminology is, however, currently in the process of being changed to the Radiant Panel Index. The Is number of classification indicates a comparative measure derived from observations made as the flame front moves across the sample surface under defined test conditions. Both ASTM E162 [12] and ASTM D3675 [13] tests use a radiant energy source. ASTM E162 requires testing four representative samples. The 27 × 45 cm strips are first pre-dried at 60 ºC for 24 hours, then conditioned to equilibrium at 23 ºC and 50% relative humidity. Each specimen is individually mounted in a holder and inclined at 30º in front of a gas fired radiant panel. The Is rating is derived from measuring both the rate at which the flame front moves down the surface of the specimen and the temperature rise indicated by an array of thermocouples located in the exhaust stack above the burning material. Specifications require flexible cellular foams to have an Is ≤25. The maximum Is requirement for other materials is 35.

2.3 Smoke Production Smoke is defined as ‘carbonaceous particles or liquid droplets that are suspended in air and measure less than 0.1 µm in size’. These particulates come from incomplete combustion of organic materials. Materials can be tested under ASTM E662 [14]. Specifications for ASTM E662 are based on the maximum specific optical density (D), for two time intervals − 1 to 1.5 minutes (smoke density, Ds is 1.5) and 4 minutes (Ds 4.0). Smoke density is determined by the attenuation of a vertical light beam located within a chamber containing the burning specimen. The test is conducted in two modes: flaming and non-flaming. In non-flaming mode samples are subjected to a specified amount of radiant heat, whereas in flaming mode the samples are subjected to radiant heat plus an open flame. A material exposed to radiant heat produces smoke before it ignites. Typically, a sample produces smoke faster when it is in flaming mode. But a sample may emit more total smoke as it smoulders in the non-flame test. If a material is going to fail, chances are it will do so during the flaming mode. Of the elastomers available, most silicones are inherently temperature resistant and consistently provide low rates of smoke generation. At the other end of the spectrum some rubber compounds do not perform well in either area.

15

Characteristics and Analysis of Non-Flammable Polymers The smoke test generates an optical density/time curve. Results are expressed in terms of Ds. For cellular foams, the Fire Research Organisation specifies a maximum (Ds 1.5) of 100 and a (Ds 4.0) of 175. With the exception of wire and cable, the Ds 4.0 value for all other materials may not exceed 200. Passenger safety and the firefighters’ ability to attack the source of the fire will suffer if the interior of a burning rail car is smoky enough to impede visibility. Various standard procedures have been published for the measurement of smoke production (Appendix 1) including ASTM E84 [15], ASTM E1354 [16], ASTM 2843-99 [17], and a Polish standard PN K-02501 [18].

2.4 Toxic Gas Generation Two concerns surround toxic gas tests. The first is over how the gases are generated. Factors such as sample size and geometry as well as test procedures can affect not only the concentration of the gases generated but possibly even the types of compounds produced. The second concern centres on how the generated gases are evaluated for toxicity. An analytical approach, for example, while convenient, ignores the existence of many compounds and their synergistic effects. Conversely, an animal testing approach is expensive and controversial. To address this issue, in the 1970s Boeing initiated a procedure called BSS 7239 [19] to help evaluate toxicity of materials used in design. With BSS 7239 the amount of gas, which is generated from a material, is measured by sampling the atmosphere in a closed chamber where the burning takes place. In 1980, BSS 7239 was replaced by the Ontario Research Organisation test, which measures carbon monoxide (CO) and carbon dioxide (CO2), hydrogen cyanide (HCN), hydrogen chloride (HCl), hydrogen fluoride, hydrogen bromide (HBr), sulfur dioxide and nitrogen oxides (NOx). The materials most likely to fail testing are polychloroprenes (Neoprenes), which have high chlorine content. During the burn test these materials commonly generate HCl levels of the order of thousands of ppm, which is well above the 500 ppm limit imposed by the standard. Various standards have been developed for the measurement of toxic gas generation accompanying the combustion of polymers (Appendix 1) including ASTM D2843

16

Test Methods for Fire Retardancy [20], BSS 7239 [19], DIN 50267-2-1 [21], DIN 50267-2-3 [22], DIN 50267-2-2 [23], DIN EN 50267-1 [24], DIN 53436-1 [25], DIN EN 60695-5-1 [26] and Polish Standard PN K-02501 [18].

2.5 Flame Testing By far the most widely accepted test for the consumer and commercial electronics industries is the Underwriters’ Laboratories Standard UL 94 [8]. The UL 94 standard encompasses six different flame tests. Depending on the test, specimens are placed either vertically or horizontally. The 20 mm Vertical Burn test (UL 94) yields ratings that progress from the least to the most stringent: V2, V1 and V0. To comply with the requirements for the V0 rating, each specimen (in a set of five) must extinguish in less than 10 seconds. After the application of a second flame, total flaming and glowing of the sample must not exceed 30 seconds. Total flaming time for a set must be less than 50 seconds in total. In addition, specimens cannot burn through their entire length, nor drip flaming particles. For a material manufactured in multiple densities, UL evaluates the minimum and maximum density. It is common practice to test a range of thicknesses because the thickness can affect the flammability. To establish a flame rating at a minimum thickness, at least two samples are tested to show the trend as a material thins and thickens. Thinner materials generally burn fast than thicker ones. Included in the horizontal tests is the horizontal burn (HB) test. This takes place on solid polymers such as plastics. Cellular elastomers are evaluated according to the horizontal foam (HF) test. Horizontal burn foam (HBF) is the minimal rating assigned in this test, followed by horizontal foam-2 (HF-2) and horizontal foam-1 (HF-1) (the most stringent). In many applications, thick foams are used for sound insulation. According to HF standards the maximum thickness that can be tested is 1.25 cm regardless of how thick the final product will eventually be.

2.6 Limiting Oxygen Index The oxygen index of a material is the percentage of atmospheric oxygen that will just support material combustion under equilibrium conditions and therefore the

17

Characteristics and Analysis of Non-Flammable Polymers higher the oxygen is, the more difficult it is for the material to burn. Typical room temperature values are usually quoted. The normal atmospheric oxygen content is 21%. As a very rough guideline: if the oxygen index of a material is less than 22% then the material will be ignited by a small flame and will continue to burn at any angle. If the oxygen index is in the range 22-28% then it will burn when held vertically but it will extinguish if the specimen is held horizontally. If the oxygen index is greater than 28% then it will generally extinguish. A rough correlation is obtained with the Underwriters Laboratory (UL) flammability ratings: < 22%

HB

22–28%

V1, V2

>28%

V0

The level of oxygen required to sustain combustion decreases with increase in temperature. Some materials are inherently flame retardant, others can be made to be so by the inclusion of chemical modifiers. The room temperature oxygen index was used to apply the ratings. An excellent rating indicates a high oxygen index. A very poor rating indicates a low oxygen index. Dabrowski and co-workers [27] investigated the fire performance of polyamide-6,6 formulations containing melamine polyphosphate, as flame retardant, using various methods, including limiting oxygen index (LOI) measurements, UL 94 tests and cone calorimetry. The effects of short, glass fibres, as filler, on fire behaviour were evaluated and the reactivity between the fibres and the flame retardant assessed using electron probe microanalysis and 27Al solid-state nuclear magnetic resonance (NMR) spectroscopy. The LOI was measured on sheets (120 × 6 × 3 mm3) [28] according to the standard OIT (ASTM D2863-12 [6]). The LOI value is measured five times for each sample to estimate the error and the check the repeatability. The values are reproducible to within ± 1 vol%. The UL 94 test is carried out on sheets (1.6 mm thick) according to the American National Standard UL 94 (ANSI/ASTM D635 [5]). For cone calorimetry the samples were exposed to a cone calorimeter according to ASTM 1356 [29] under a heat flux of 50 kW/m2. This flux is chosen because it corresponds to the evolved heat during a fire [30, 31]. The rate of heat release (RHR)

18

Test Methods for Fire Retardancy and the residual weight are obtained using a software developed by Dabrowski and co-workers [27]. The experiments are repeated three times. When measured at 50 kW/m2 flux, RHR is reproducible to within ± 10% and weight loss is reproducible to within ±15%. The curves of weight difference between the experimental and the computed curves of residual mass are computed as follows: Mpoly (T): polymer curve; Madditives (T): additives curves; Mexp (T): polymer-additives curves; Msim (T): curve computed by linear combination between the curves of the polymer and the additives; ∆m(T): curve of weight difference Mexp (T)-Msim (T). A thermocouple placed at the under side of the sample during a cone calorimeter experiment enables some thermal barrier properties of the material during its combustion to be ascertained. As shown in Table 2.2 the incorporation of 30% melamine polyphosphate FR in virgin polyamide-6,6 or in short fibre glass reinforced polyamide-6,6 produces an intumescent material giving a strongly enhanced LOI value when compared to the virgin polyamide-6,6. Also, the short fibre glass reinforced polyamide-6,6 containing 30% melamine polyphosphate shows a better efficiency as a flame retardant agent than does the unreinforced polyamide-6,6 containing 30% melamine polyphosphate. The improved fire retardancy is due to the viscosity increase of the molten polymer.

Table 2.2 LOI Values of injection moulded polyamide-6,6 formulations Material

LOI (volume%)

Polyamide-6,6

25

Polyamide – melamine polyphosphate (30%)

38

Short glass fibre reinforced polyamide-6,6

24

Short glass fibre reinforced polyamide-6,6 - melamine polyphosphate (30%)

48

Source: Author’s own files

Dabrowski and co-workers [27] further observed that RHR during LOI measurement of the formulations containing 30% melamine pyrophosphate FR is strongly reduced (by about 90%) when compared with values obtained for virgin or short glass

19

Characteristics and Analysis of Non-Flammable Polymers fibre reinforced polyamide-6,6. Moreover, the incorporation of 30% melamine pyrophosphate FR in virgin or glass fibre reinforced polyamide-6,6 stabilises the weight loss accruing with time. As a result of this and further studies by thermogravimetric analysis (TGA), solid-state NMR and electron probe microanalysis, Dabrowski and co-workers [27] conclude that melamine polyphosphate is an efficient flame retardant additive in polyamide-6,6 (glass fibre reinforced or not). The glass fibres are shown to strongly influence the fire performance of the intumescent FR material. A reactivity between the additive and the glass fibre and the formation of alumino-phosphates was demonstrated. These species might be responsible for the improvement of the FR behaviour particularly in the conditions of the LOI test. LOI measurements have been reported on a range of polymers including phenolic resin-silica nanocomposites [32], alkyl phosphate type polyols [33], unsaturated polyesters with dicyclopentadiene chain ends [34] and silicon containing epoxy resins [35], polysiloxone compounds containing organophosphorus and epoxy groups [36], phosphorus containing unsaturated polyesters [37], triacryloyloxy ethyl phosphate and diacryloyl-oxyethyl phosphate [38], phenylisocyanurate polyurethane (PU) foams, and polypropylene (PP)-melamine phosphate [39, 40]. Various standard test procedures have been described for the measurement of LOI (Appendix 1) including ASTM E1354 [16], and DIN 4102-2 [41].

2.7 Oxygen Consumption Cone Calorimetry One of the most important parameters that can be used to characterise a fire is the rate of heat release. It provides an indication of the size of the fire, the rate of fire growth and consequently the release of smoke and toxic gases, the time available for escape or suppression, the type of suppressive action that are likely to be effective and other attributes that define the fire hazard. Methods based on the oxygen consumption principle are now available to measure the rate of heat release reliably and accurately. The principle depends upon the fact that the heats of combustion of organic materials per unit of oxygen consumed are approximately the same. This is because the processes in the combustion of all these products involve the breaking of C-C and C-H bonds (which release approximately the same amount of energy) with the formation of CO2 and water. The cone calorimeter is the most generally accepted and powerful instrument in this field. Originally developed by Vytenis Babrauskas of the Centre for Fire Research at NIST, it is now available as a complete instrument embodying specific safety and

20

Test Methods for Fire Retardancy design features while retaining the design set out in the proposals. The design enables the following to be determined and calculated automatically: • RHR • RHR per unit area • Mass loss rates • Time to ignition • Effective heat of combustion This instrument has been used for the evaluation of buildings, furniture, transport, aerospace, wood and electrical materials and composites. Polymers to which this technique has been applied include PP and PP-composites [42], ethylene-vinyl acetate copolymers [43], polyamide-6,6 [27], silicate-siloxane composites [44], glass-phenolic composites [45], polyolefins [46], conveyor belt materials [47] and roofing materials [48]. The US Naval Surface Warfare Centre, Carderock Division [49] used cone calorimetry to evaluate several alternative glass reinforced brominated vinyl ester resins containing various FR including aluminium trihydrate (ATH). Cone calorimetry was carried out at three different fluxes, 25, 50 and 75 kW/m2. Smoke production and carbon monoxide yields were also determined. Bromination of vinyl-ester resin imparts fire retardancy as manifested by flame spread and lower RHR [50]. However, this fire-retardant system functions primarily in the gas phase causing incomplete combustion. As such, brominated resins produce dense smoke, and an increase in the yield of CO and HBr. Recent interest in the use of non-halogenated organic-matrix composite materials in US Navy submarines and ships has generated the requirement for significant improvement in the flammability performance of these materials including reduction in the amount of smoke, CO and corrosive combustion products. Figures 2.2 and 2.3 show the RHR data obtained from cone calorimetry of glass reinforced composites with different vinyl ester groups.

21

Characteristics and Analysis of Non-Flammable Polymers 500

HRR (kW/m2)

400

7 8 9 0

1167 1168 1169 1170

300 200 100 0

0

60

120

180 240 300 360 420 480 Time (seconds)

540

600

Figure 2.2 Cone calorimetry. Heat release rate (HRR) of virgin brominated vinyl ester resin. Reproduced with permission from U. Sorathia, J. Ness and M. Blum, Composites Part A: Applied Science and Manufacturing, 1999, 30, 707. ©1999, Elsevier [49]

350 300 0 1 5 6

HRR (kW/m2)

250

1194 1190 1191 1195 1198

200 150 100 50 0

0

60

120

180

240 300 360 Time (seconds)

420

480

Figure 2.3 Cone calorimetry. Heat release rate (HRR) of a glass fibre reinforced brominated vinyl ester containing (-) no additives (O) siloxane powder, (1) char forming chemicals, (5) layered silicate nanocomposite and (6) ATH. Reproduced with permission from U. Sorathia, J. Ness and M. Blum, Composites Part A: Applied Science and Manufacturing, 1999, 30, 707. ©1999, Elsevier [49] 22

Test Methods for Fire Retardancy Table 2.3 includes smoke data from the cone calorimeter such as specific extinction area and smoke production rate. All testing was performed in the horizontal orientation. For each panel at any given flux the average of these readings was calculated. Specific extinction area (SEA) (m2/kg) is defined as the smoke that is produced per unit mass of material being volatilised, i.e., kVs /ṁ, where, k is the extinction coefficient (m-1), Vs is the standard volume flow rate of air (m3/s), and ṁ is the mass loss rate of the sample (kg/s). SEA is usually adopted to express the extent of the contribution to the smoke generation. The smoke production is given as the product of specific extinction area and the mass loss rate.

Table 2.3 Smoke data (ASTM) for various glass/vinyl-ester composites Test

Compounds tested

Test (flaming)

1167

1168

1169

1170

Dmax, flaming

173

593

217

197

Ds (300 s), flaming

103

503

154

185

CO (ppm)

300

800

200

300

2

0.5

2

2

HCI (ppm)

ND

Trace

ND

ND

HCN (ppm)

2

2

Trace

Trace

CO2 (% vol)

1167 – non-brominated epoxy vinyl ester 1168 – brominated epoxy vinyl ester 1169 – non-brominated vinyl ester 1170 – brominated vinyl ester Dmax – Maximum smoke production rate Ds (300 s) – Smoke production rate after 300 s ND – not detected Reproduced with permission from U. Sorathia, J. Ness and M. Blum, Composites Part A: Applied Science and Manufacturing, 1999, 30, 707. ©1999, Elsevier [49]

Four types of FR additives were used in this study, namely siloxane powder, char forming additive, layered silicate nanocomposites and ATH. Heat release of these (Figure 2.3) compared with those of a virgin additive-free brominated vinyl ester resin (Figure 2.2). Table 2.4 presents the results of HRR and smoke generation.

23

Characteristics and Analysis of Non-Flammable Polymers

Table 2.4 Heat release and smoke data (ASTM E1354 [16]) for various glass/vinyl-ester composites 1167 Epoxy vinyl ester

1168 Brominated epoxy vinyl ester

Flux (kW/m2)

25

50

75

25

50

75

25

50

75

25

50

75

Time to ignition (s)

320

85

42

214

52

29

302

85

42

259

75

36

Peak HRR (kW/m2)

308

276

281

147

152

217

342

302

303

356

348

432

Average HRR (kW/m2)

106

116

128

70

60

89

136

129

138

132

128

168

Average HRR (180 s) (kW/m2)

187

203

215

105

112

158

223

226

229

236

248

300

Average HRR (g/s/m2)

180

184

190

92

86

108

211

198

203

190

179

202

Total HRR (MJ/m2)

64

59

59

29

28

33

68

62

63

58

55

61

Average HRR (g/s2)

7.94

9.15

11.2

11.99

13.02

18.2

10.9

12.15

13.1

10.4

12.76

15

Average SEA (m2/kg)

836

999

986

1341

1524

1569

796

815

872

914

1027

1050

Average SPR (m2/s)

1169 Non-brominated vinyl ester

1170 Brominated vinyl ester

0.0663 0.0914 0.1104 0.1608 0.1984 0.2856 0.0868 0.0990 0.1142 0.0950 0.1310 0.1575

Average Efficiency (HOC) (MJ/kg)

24

22

21

10

11

11

22

21

21

24

2324

Peak CO (ppm)

293

250

327

777

753

1030

410

330

407

452

350

495

0.119

0.119

0.049

0.048

0.052

0.050

0.048

0.056

Average CO yield 0.038 (kg/kg)

0.041 0.045 0.114

HOC – Heat output coefficient SPR – Smoke production rate Reproduced with permission from U. Sorathia, J. Ness and M. Blum, Composites Part A: Applied Science and Manufacturing, 1999, 30, 707. ©1999, Elsevier [49]

24

Test Methods for Fire Retardancy ATH was selected as the best overall fire-retardant additive in the application. It works by endothermically releasing water at the fire exposure temperature. Cone calorimeter evaluation of the fire-retardant study has provided data for peak and average HRR, smoke production rates and CO yields for vinyl-ester resins with and without additives. Evaluation was conducted at three different fluxes to simulate small and large fires. In the first step, brominated epoxy vinyl ester sample 1168, as shown in Table 2.4, exhibited lower HRR, but significantly higher smoke generation and CO yield when compared with non-brominated vinyl esters sample 1167, Table 2.4. It also resulted in lower time to ignition. Thus, the effect of bromination is evident which causes incomplete combustion and is also reflected in a lower effective heat of combustion. However, at the high flux of 75 kWm2, results indicate a significant increase in mass loss rate, which may be partially explained by the increase in peak HRR and total heat release but may be accompanied by an increased production of HBR. Smoke chamber data also indicated high smoke and carbon monoxide generation for brominated vinyl ester. Non-brominated epoxy vinyl ester (sample 1167) was selected for further study due to lower smoke generation and carbon monoxide yields. This was also accompanied by higher peak and average HRR. This vinyl-ester selection was also based on the evaluation of tensile, compressive and shear properties conducted concurrently with small scale fire testing. In the second step, epoxy vinyl ester sample 1167 was studied in conjunction with selected fire-retardant additives. The selection of additives was made on the basis of their potential to lower HRR. The incorporation of additives could not be accomplished using the preferred vacuum assisted resin transfer moulding process due to the particle sizes of the additives selected and their inability to flow through the glass woven roving to fully wet the reinforcement. In some cases, the additives appeared to separate out and resulted in non-homogenous composite panels. No attempt was made in this study to optimise the vacuum assisted resin transfer moulding process or the particle size of the additives. It was assumed that comparative screening of the additives could be accomplished by hand lay-up followed by consolidation of the composite panels with vacuum bagging. Results are shown in Table 2.5. All additives were effective in reducing peak HRR to some extent. Of the additives studied ATH (sample 1196) shows 20% and 25% decreases in peak HRR at radiant heat fluxes at 50 and 75 kW/m2, respectively, and 24% and 13% decreases in average HRR at 50 and 75 kW/m2, respectively. Also, average mass loss rates were decreased by 27% and 24% at 50 and 75 kW/m2.

25

26

190

62

9.08

Average HRR (300 s) (kW/m2)

Total HRR (MJ/m2)

Average mass (g/s/m2) 1086

10.89

62

202

245

190

313

94

50

1111

11.98

61

200

236

171

325

43

75

902

9.52

44

146

195

133

309

240

25

1185

10.99

43

215

161

307

74

50

1190

1231

12.36

42

215

169

311

37

75

785

8.03

71

191

194

141

317

346

25

902

8.81

69

188

182

151

279

89

50

1191

1061

10.40

66

199

199

170

293

38

75

802

7.84

79

198

210

139

332

334

25

998

8.96

64

191

198

162

283

85

50

1195

1120

10.29

69

199

192

164

283

37

75

726

6.84

59

165

172

121

303

386

25

852

7.99

56

167

167

144

249

99

50

988

9.06

60

180

177

149

245

45

75

1196 Aluminium

273

0.046

Peak CO (ppm)

Average CO yield (kg/kg)

0.047

300

23

0.051

388

22

0.049

300

23

0.048

303

23

0.049

370

22

0.047

272

24

0.047

285

22

0.043

303

21

0.049

283

24

0.044

280

24

0.048

308

23

0.036

280

23

0.037

238

23

1194 – Control, no FR additives 1190 – Siloxane powder 1191 – Char forming additive 1195 – Layered silicate nanocomposites Reproduced with permission from U. Sorathia, J. Ness and M. Blum, Composites Part A: Applied Science and Manufacturing, 1999, 30, 707. ©1999, Elsevier [49]

24

0.037

240

23

0.0746 0.1183 0.1331 0.0859 0.1302 0.1522 0.0630 0.0795 0.1103 0.0629 0.0894 0.1152 0.0497 0.0681 0.0895

Average efficiency (HOC) (MJ/kg)

Average SPR (m2/s)

Average SEA (m /kg)

822

213

Average HRR (180 s) (kW/m2)

2

139

337

Peak HRR (kW/m2)

Average HRR (kW/m )

323

Time to ignition (s)

2

25

1194 (Control)

Flux (kW/m2)

Test

Table 2.5 Heat release and smoke data (ASTM) for glass/vinyl composites with additives

Characteristics and Analysis of Non-Flammable Polymers

Test Methods for Fire Retardancy As a consequence of a very serious fire under the steel roofs in a large car plant in USA the Underwriters Laboratories Inc., developed a new UL test method, which uses oxygen consumption cone calorimetry to quantify roof covering materials. This test was used to quantify the contribution of roof covering materials to the fire under the roof by capturing effluent from beneath the roof assembly and recording the rate of heat production in kW/min. Sorathia and co-workers [51] investigated the use of smaller scale fire test methods. From these investigations, two methods, differing in concept and technique, were developed. The methods developed by the UL in the late 1950s are still in use today and are described in the Approval Standard for Class 1 Roof Covers, FM 4470 [52] and Fire Test of Roof Deck Constructions, UL 1256 [53]. Based on the observed inconsistencies between the large scale, White House Test and the UL 1256 method [53], it was concluded that a new smaller scale fire test method was needed. Therefore, UL developed a test procedure that permits the release of heat energy to the atmosphere, as has occurred in every large scale White House Test. It is not necessary to quantify the heat energy released harmlessly to the sky, as much of the smoke developed in roofing assemblies is not quantified or regulated in current building codes. It is, however, necessary to verify that a given assembly does vent. Testing has shown that different insulation thickness and cover board combinations will produce differing results with regard to venting. The new UL test method utilises a collection hood and duct system prescribed under various nationally recognised fire test procedures including the UL 1715 Standard [54]. The test structure is a masonry room measuring 2.4 m wide by 3.7 m long by 2.4 m high, with one 2.4 m wide open end. Heptane fuel burners are used to provide the internal fire source. The test method utilises oxygen consumption calorimetry to quantify the roof covering materials. The new test method now being used to test roof deck constructions, that contain polystyrene directly over steel decks, is similarly validated. To complete the understanding and acceptance of the new test, UL is documenting the White House Test and the new smaller scale fire test procedure and acceptance criteria. The methods are being reviewed under the UL standards revision process and, upon completion, will be submitted to the ANSI approvals process, to be incorporated into UL 1256 [53]. The standardisation process will facilitate adoption by regulatory authorities of the historical large-scale White House Test, and the new smaller scale test procedure. In the meantime, two of the US model code agencies have reviewed and accepted the new UL test method as a valid measure of underdeck fire spread performance and

27

Characteristics and Analysis of Non-Flammable Polymers have granted technical reports to that effect. The reports were granted under typical building code language that allows the introduction of new methods and materials when proper engineering and life safety justification is provided by the applicant. Cone calorimetry has been applied to the determination of HRR of a number of polymers including high-density polyethylene/paraffin hybrids [55], PP composite [42], magnesium hydroxide encapsulated polyethylene [56]. Ethylene-vinyl acetate [57], polyisocyanurate PU intumescent foams [39], silicate-siloxane composites, ethylene-vinyl acetate-polyamide intumescent polymer [44], ethylene-vinyl acetate [58], polyolefin zeolite systems [46], Nylon 6/MgAl layered double hydroxide [59], polyamide nanocomposites [60], polydimethylsiloxane [61], epoxy/phenyltrisilanol and polyhedral oligomers [62], polysiloxane containing organophosphorus and epoxy groups [36], and PP and carbon nanotube composites [63]. Various standard test procedures have been published for carrying out core calorimetric measurements (Appendix 1) including ASTM D4809 [64], ASTM E1354 [16], ISO 5660 [65] and US National Bureau of Standards NR SIR 82-2611 [30].

2.8 Pyrolysis – Gas Chromatography – Mass Spectrometry When polymers are burnt or smoulder in air, the combustion products are extremely complex, often consisting of several hundred compounds. Because of the toxic or unknown nature of these products, it is important to know their composition in some detail. This information is also essential for mechanistic and modelling studies of the smoke formation process, which can lead to the design of less hazardous polymers in the future. A number of analytical methods [66, 67] involving pyrolysis of polymers have been reported in the literature. Michal and co-workers [68] developed a method using direct gas chromatography (GC)-mass spectrometry (MS) for their study of the combustion of polyethylene (PE) and PP. Morikawa [69] used GC to determine polycyclic aromatic hydrocarbons in the combustion of polymers. Liao and Browner [70] also described a method for the determination of polycyclic aromatic hydrocarbons. Many other workers have studied soot and smoke formation and their mechanisms in the combustion of polymers. Generally in these studies, relatively simple and specific methods were used, which were appropriate for the intended tasks. However, these methods are not suitable for complete analysis of the very complex smoke particulates resulting from combustion of many polymers. Most methods have been developed either for volatile compounds of low molecular weight or for polycyclic aromatic hydrocarbons. Joseph and Browner [71] developed a method that can be used to

28

Test Methods for Fire Retardancy analyse all classes of compounds produced by the combustion of polymers and applied this method of rigid PU foams prepared by the polymerisation of diphenylmethane diisocyanate and glycols. The method is directed towards the particulates produced and excludes the volatile compounds of very low molecular weight. Smoke particulates from the smouldering of PU foam in air were collected on glass fibre filters and extracted with chloroform. The concentrated extract was subjected to acid and base extractions. The acid compounds were converted to methyl esters and analysed by a GC-MS data system. The basic and phenolic compounds were analysed using the same system without derivatisation. The neutral fractions were separated into different classes by high-performance liquid chromatography on a bonded amine column. Different fractions were collected and each fraction was analysed by GC-MS with data collection. Some nitrogen containing compounds were identified in the neutral fractions. There were five-membered nitrogen containing ring compounds, including indole, isoxazole, indazole, and carbazoles which do not show basic properties and consequently do not react with 1 M hydrochloric acid in the basic extraction step. A number of phthalate esters were also present in different fractions. Pyrolysis - gas chromatography - mass spectrometry (Py-GC-MS) has been applied to studies of thermal decomposition and combustion behaviour of polyhydroxyamide and its bromine, fluorine, phosphate and methoxy derivatives [72], poly(3,3´-di hydroxybiphenylisophthalimide) and its halogenated phosphinite and phosphate derivatives [73], rigid PU foams [74], and chlorinated polyethylene [75]. Sato and co-workers [76] studied the thermal degradation of a polyester-based material, flame retarded with antimony trioxide-brominated polycarbonate by means of various temperature-programmed analytical pyrolysis techniques such as temperature programmed Py-MS, temperature-programmed atomic emission detection, and temperature-programmed Py-GC. During the degradation of the flame-retardant polyester, brominated phenols were first observed to evolve at temperatures slightly lower than those for the flammable product evolution from the substrate polyester polymer, followed by the evolution of hydrogen bromide over the whole range of degradation temperatures for the substrate polymer. These degradation processes were closely related to the synergistic effects of antimony trioxide on the decomposition of brominated polycarbonate in the flame-retardant system to promote the thermal degradation of the brominated polycarbonate at lower temperatures than those for pure brominated polycarbonate. Furthermore, the evolution of the flame poisoning antimony tribromide formed through the reaction between brominated polycarbonate and antimony trioxide could also be monitored directly by temperature-programmed pyrolysis techniques.

29

Characteristics and Analysis of Non-Flammable Polymers There has been very little information published on the thermal degradation of flame retarded PE composites. Wang and co-workers [77] studied the thermal degradation of flame retardant linear low-density polyethylene (LDPE) composites containing magnesium hydroxide and red phosphorus. Data obtained by Py-GC-MS, showed that incorporation of red phosphorus into the LDPE - magnesium hydroxide composites results in a change of pyrolysis mode and this causes a great increase in the amount of high molecular weight hydrocarbons. When pyrolysis is carried out at 150 ºC the components occurring at the maximum concentration in the hydrocarbon region are located in the C23 region for virgin linear low-density polyethylene (LLLDPE), LDPE – 50% magnesium hydroxide and LLDPE – 40% magnesium hydroxide – 10% red phosphorus. Zhang and co-workers [78] studied the decomposition and flammability of fire retarded UV visible sensitive polyacrylates and their copolymers based on bisphenol A (BPA), 1,1-dichloro-2,2-bis(4-hydroxylphenyl)ethylene (BPC II) and 4,4´-dihydroxy3-ethoxy benzylidenoacetophenone polyarylate (Chalcon II). The study included investigation by Py-GC-MS, simultaneous thermal analysis and pyrolysis-combustion flow calorimetry [59]. Thermal relationships between flammability and structure/composition of these polymers was explored. It is found that BPC II-polyarylate is an extremely fire-resistant thermoplastic that can be used as an efficient flame-retardant agent to be blended with the other polymers. Chalcon II-polyarylate is of interest as a UV/visible-sensitive polymer with a relatively low HRR and a high char yield. Pyrolysis combustion flow calorimetry (PCFC) results show that the total heat of combustion of the copolymers or blends changes linearly with the composition, but the change of maximum HRR and char yield depends greatly on the chemical structure of the components. These workers point out that although the rank order of the fire performance of many virgin polymers has been assessed by some small-scale flammability tests, such as limiting oxygen index and cone calorimetry, some of these tests still require relatively large samples, and the results are determined not only by the characteristics of materials scorched in the fire but also by a multitude of conditions and factors. It would be a great improvement if a relatively low cost quantative test was available. Zhang and co-workers [78] point out that PCFC is such a test. It operates on the oxygen consumption principle, i.e., the net heat of complete combustion of organic molecules per mole of oxygen consumed is relatively constant: E = 419 ± 19 kJ/mole, O2 = 13.1 ± 0.6 kJ/g O2, which is essentially independent of the chemical consumption of the combustion polymer. In this technique the samples are pyrolysed in an inert gas stream followed by high-

30

Test Methods for Fire Retardancy temperature combustion of the volatiles in excess oxygen. The HRR, total heat of combustion of the volatiles and the char yield can be directly obtained from PCFC. The correlations between PCFC and some standard tests, such as oxygen bomb calorimeter according to ASTM D4809 [64], cone calorimeter at 50 kW/m2 incident heat flux according to ASTM E1354 [16], and UL 94 [8], are all fairly good. Therefore, PCFC is an efficient screening tool for newly synthesised fire-resistant materials. Table 2.6 shows the PCFC results as well as some TGA results, from which we can see that different bridging groups in the bisphenols also have a large influence on the flammability of polymers.

Table 2.6 Flammability and thermal decomposition of BPA, Chalcon II and BPC II homopolymers a Heat resistance Total heat Char yield Tmaxb Peak mass loss Polymer capacitya (J/gK) (kJ/g) (%) (ºC) rate (x 103/s) BPA

360

18

27

488

2.2

Chalcon II

110

10

41

425

0.9

BPC II

12

4

51

472

0.6

PE

1558

40

0

471

7.0

PC

382

19

17

514

3.3

PEEK

163

13

46

586

2.2

PI

29

9

50

602

0.5

a

PCFC results Temperature at peak mass loss rate obtained from derivative TGA curves PC - polycarbonate PEEK - polyetheretherketone PI – polyimide Reproduced with permission from H. Zhang, P.R. Westmoreland, R.J. Harris, E.B. Coughlin, A. Plichta and Z.K. Brozowski, Polymer, 2002, 43, 5463. ©2002, Elsevier [78]

b

Py-MS (Py at 930 ºC) shows that the major decomposition products of BPA and Chalcon II-polyacrylates are a series of phenols and some other flammable aromatic compounds (Figure 2.4). However, BPC II-polyacrylate gives out less flammable compounds (such as phenols), but more CO2, CO and HCl and some chlorinated aromatic compounds which have relatively low fuel values and may also confer flameretardant effects in the gas phase. Therefore, the reduced flammability of Chalcon

31

Characteristics and Analysis of Non-Flammable Polymers II-polyacrylate (compared with BPA-polyacrylate) is mainly due to the low mass loss rate and the lesser amount of fuels generated. While, in the case of BPC II-polyacrylate, release of less flammable decomposition products is another important factor for its low flammability. So, compared with some other commercial polymers, Chalcon IIand BPC II-polyacrylates are more heat and flame resistant, and BPC II-polyacrylate has an especially low flammability. Abundance 1000000

(a) OH

900000 800000

OH

700000 600000

OH

OH

500000

O

OH C2H5

400000

C=O O

300000

O

OH

200000 CO2,CO CH4

100000

2.00

4.00

6.00

8.00

10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00

Abundance 500000

(b)

450000

OH

400000 350000 300000

OH

OC2H6

250000

COOH

200000

OH

150000 100000

HO C O

C OCH2 O

CO2,CO C2H6

50000

0 2.00

32

4.00

6.00

8.00

10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00

Test Methods for Fire Retardancy Abundance 140000

(c)

130000

OH

120000 110000 100000

CO2,CO,HCl

COCl O

90000 80000 COOH

70000

HO C O

60000

C OCH2 O

50000 Cl

40000 30000 20000 10000 0 2.00

4.00

6.00

8.00

10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00

Figure 2.4 Pyrolysis - gas chromatography of (a) BPA polyacrylates; (b) Chalcon II; and (c) BPC II at pyrolysis temperature 250-930 ºC, heating rates 43 ºC/s. Reproduced with permission from H. Zhang, P.R. Westmoreland, A.J. Farris, E.B. Coughlin, A. Pichta and K. Brozowski, Polymer, 2002, 43, 5463. ©2002, Elsevier [78]

Zhang and co-workers [79] investigated flame retardency and thermal behaviour of rigid PU foams prepared with different blowing agents and FR. Char yields produced upon combustion of the polymers were evaluated by the Butler Chimney Standard test method and pyrolysis - mass spectrometry (pyrolysis at 700 ºC). A Butler chimney apparatus was fabricated following the ASTM D3014 standard flammability test [80]. The tests were conducted on six cut specimens from material of uniform density in the centre part of the foam. Each foam specimen size was 254 × 19 × 19 mm3. The cut foams were mounted on the vertical Butler chimney and ignited with a Bunsen burner for 10 seconds. The temperature of the Bunsen burner was monitored with a thermocouple and set to be 960 ± 5 ºC. The extinguishing time of the flame, after the burner was removed from the bottom of the foams, was recorded and reported as the burning time. The percentage mass retained or char yield was determined after each test run, and the char was collected for further analysis.

33

Characteristics and Analysis of Non-Flammable Polymers

2.9 Laser Pyrolysis – Mass Spectrometry There are several references to this technique pioneered by Price [81-91] and his co-workers. Two systems have been investigated to model different aspects of flameretarded polymer behaviour in a fire. One system uses a continuous laser to model radiative heat at a level similar to that from a burning item in a room fire and the other uses a pulsed laser to model conditions immediately behind the flame front. Price [84] pointed out that fire behaviour of a burning polymer, from the chemical viewpoint, could be considered to be governed by chemical reactions in the condensed phase, the gas phase and the interface between the two. Major pyrolysis occurs at the condensed phase/vapour phase interface region and plays a crucial role in determining the combustion behaviour. Results obtained from conventional pyrolysis experiments may not be directly relevant to real fire situations. However, rapid heating rates, analogous to those occurring in real fires, are readily obtained by means of focused laser light. Fire behaviour of a burning polymer, from the chemical viewpoint, can be considered to be governed by chemical reactions in three regions, namely the condensed phase, the interface between the condensed phase and the gas phase, and the gas phase flame. The chemical reactions are of two types: pyrolysis and oxidation. Pyrolysis is a comprehensive terminology implying all possible thermal reactions including degradation by breaking a few bonds, decomposition through extensive breakdown of polymer structure and further or secondary reactions between the decomposition species and/or atmospheric gases. Major pyrolysis occurs at the condensed phase/ vapour phase interface region. From here combustible volatile products escape into the gas phase where they combust in the flame. It is also the region where condensed phase flame retardants act. Thus, pyrolysis at the interface region plays a crucial role in determining the combustion behaviour. Therefore, an understanding of the pyrolysis reactions in this interface region, the so-called ‘dark flame’ region, is essential to an understanding of the chemistry of polymer combustion, and the mechanisms of flame retardant behaviour, with the caveat that oxidative pyrolysis also needs to be understood as an element of the process. In a real fire situation, the heating rate at the polymer surface exceeds 300 K/min. This condition is outside of the scope of attainment of conventional thermal experimental techniques, which are typically no higher than 100 K/min. For this reason, results obtained from conventional pyrolysis experiments may not be directly relevant to real fire situations. However, rapid heating rates, analogous to those occurring in real fires, are readily obtained by means of focused laser light.

34

Test Methods for Fire Retardancy Price has reported the use of pulsed laser pyrolysis to generate conditions, analogous to those behind the flame front in a real fire, at the surface of a polymer sample. The temporal behaviour of the species escaping from the reaction zone created in this way at the polymer surface is monitored by the very fast scanning time-of-flight mass spectrometer (ToF-MS). The ToF-MS is able to provide a complete mass spectral analysis every 25 µs. This identifies the species involves and indicates their relative concentrations. Studies on a series of flame retarded rigid PU foams [8, 91] which varied in isocyanate index and the molecular weight of the polyols used in their preparation showed that the flame retardance of the samples increased with increasing isocyanate index and weight fraction of the isocyanate. Laser pyrolysis experiments involving these samples found that the volatiles were mainly the monomer and oligomers of polypropylene glycol used to produce the foam plus lower molecular weight species of which CO2 formed the major part. An increase in isocyanate index results in a reduction in the extent of monomer/oligomer evolution and an increase in the low molecular weight species. With reference to the behaviour of the foams in a real fire situation, it could be imagined that the monomer/oligomer components and their breakdown products would act as ‘fuel’ in the flame region while the low molecular weight species dominated by CO2 would be relatively non-flammable. An increase of isocyanate index is equivalent to making less ‘fuel’ and more of the ‘inert gases’ available to the burning zone and thus improving the fire resistance of the rigid PU foams. Price [88] also showed that laser pyrolysis of polymethylmethacrylate (PMMA) yields essentially only the monomer, methylmethacrylate (MMA), which would be the fuel in any fire situation. The same experiments but with the PMMA flame retarded with 20% ATH showed significantly reduced quantities of the monomer whereas large amounts of water and CO2 were evolved. The implication of these results is that in a real fire situation, the ATH influences the PMMA pyrolysis to facilitate a reduction in the amount of fuel evolved whilst adding non-combustible gases (e.g., steam) into the flames. Assuming this behaviour mirrors what happens behind the flame front in a real fire, then both these products will significantly retard the burning processes in a conflagration. Firstly, both steam and CO2 are non-flammable and would, therefore, not add to the fuel available to the flames. Also, both would act as diluents, thereby, reducing the rate of the flame reactions and, thus, the rate of heat release. Secondly, water is released via the very endothermic decomposition of aluminium oxide trihydrate. This endothermicity would result in a significant cooling of the PMMA surface and, consequently, a reduction in the rate of polymer decomposition and, thus, in the rate of fuel supply to the flames. If the latter is sufficient, then the flame will extinguish. Thirdly, water has a high heat capacity, which will cause considerable cooling in the flame. Thus, much less heat will be available to the polymer surface to sustain the

35

Characteristics and Analysis of Non-Flammable Polymers combustion cycle. Again, there is the possibility that this effect will be sufficient to extinguish the flame. Ebdon and co-workers [86] discussed the application of laser pyrolysis to studies of the flame retardance of polystyrenes and PMMA with covalently bound phosphorus groups including vinyl phosphoric acid, several dialkyl vinyl phosphates, and various vinyl and allyl phosphine oxides. TGA and measurements of LOI and char yields were used to provide a preliminary evaluation of the flame retardance of these polymers. The phosphorus-containing polymers all produce char on burning (and also on heating in air or nitrogen) and have LOI higher than those of the parent homopolymers, indicating significant flame retardance involving condensed-phase mechanisms. But although there are general correlations between LOI, char yield and phosphorus content, some copolymers have higher than expected LOI and/or yield, whilst others have lower char yields indicating that the phosphorus environment is significant. So that mechanisms of flame retardance could be investigated in more detail, laser pyrolysis/ToF-MS and MS thermal analysis were applied to study the decomposition behaviour of three of the MMA copolymers: those containing pyrocatecholvinylphosphate, diethyl-p-vinyl benzylphosphonate (MMA-DEpVBP) and di(2-phenylethyl) vinylphosphonate (MMA-PEVP) as co-monomers. The laser pyrolysis experiments provide information on probable polymer behaviour behind the flame front in a polymer fire and reveal that copolymerisation of MMA with the comonomers does not greatly alter the pyrolysis mechanism compared with that of PMMA. The amounts of MMA monomer evolved during pyrolysis, however, are much reduced for the copolymerised samples. Since MMA is the major fuel evolved during the combustion of PMMA and its copolymers, this effect must be a major contributing factor to the reduced flammability shown by the copolymers. MMADEpVBP underwent the most extensive decomposition following laser pyrolysis. Significant amounts of highly flammable methane and ethane in particular were detected. Such increased amounts would also occur if the copolymer were to be exposed to high temperature conditions when burnt. Hence, it seems reasonable that the MMA-DEpVBP has a lower LOI value than anticipated, despite it giving a relatively high yield of char. Mass spectrometric thermal analysis studies of the MMAPEVP provide evidence that the PEVP unit decomposes around 200 °C, eliminating styrene, with evolution of MMA reaching a maximum about 50 °C higher. Possible mechanisms for these processes are suggested.

References 1.

36

W. Becker in Brandverhalten von Kunststoffen, Ed., J. Troitzsch, Carl Hanser Verlag, Munich, Germany, 1982.

Test Methods for Fire Retardancy 2.

G. Schreyer in Konstruieren mit Kunststoffen, Carl Hanser Verlag, Munich, Germany, 1972.

3.

F.H. Prager, Kunststoffe im Bau, 1978, 13, 2, 45.

4.

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5.

ASTM D635, Test Method for Rate of Burning and/or Extent and Time of Burning of Plastics in a Horizontal Position, 2010.

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ASTM D2863, Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-like Combustion of Plastics (Oxygen Index), 2012.

7.

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37

Characteristics and Analysis of Non-Flammable Polymers 17. ASTM D2843, Test Method for Density of Smoke from the Burning or Decomposition of Plastics, 2010. 18. PN K-02501, Rolling Stock - Smoke Properties of Materials - Requirements and Test Methods, 2000. 19. BSS 7239, Toxic, Gas Sampling and Analytical Procedures, 2011. 20. ASTM D2843, Test Method for Density of Smoke from the Burning or Decomposition of Plastics, 2010. 21. DIN 50267-2-1, Common Test Methods for Cables under Fire Conditions Tests on Gases Evolved during Combustion of Material from Cables - Part 2-1: Procedures - Determination of the Amount of Halogen Acid Gas, 1999. 22. DIN 50267-2-3, Common Test Methods for Cables under Fire Conditions Tests on Gases Evolved During Combustion of Material from Cables - Part 2-3: Procedures - Determination of Degree of Acidity of Gases for Cables by Determination of the Weighted Average of pH and Conductivity, 1999. 23. DIN 50267-2-2, Common Test Methods for Cables Under Fire Conditions Tests on Gases Evolved During Combustion of Material From Cables - Part 2-2: Procedures - Determination of Degree of Acidity of Gases for Materials by Measuring pH and Conductivity, 1999. 24. DIN EN 50267-1, Common Test Methods for Cables Under Fire Conditions Tests on Gases Evolved During Combustion of Materials From Cables - Part 1: Apparatus, 1999. 25. DIN 53436-1, Producing Thermal Decomposition Products from Materials in an Air Stream and their Toxicological Testing; Decomposition Apparatus and Determination of Test Temperature, 1981. 26. DIN EN 60695-5-1, Fire Hazard Testing - Part 5-1: Corrosion Damage Effects of Fire Effluent - General Guidance, 2003. 27. F. Dabrowski, M. Le Bras, R. Delobel, D. Le Maguer, P. Bardollet and J. Aymami in Proceedings of the BPF Flame Retardants 2002 Conference, London, UK, 2002, Paper No.15, p.127. 28. W.S. Jou, K.N. Chen, D.Y. Chao, C.Y. Lin and J.T. Yeh, Polymer Degradation and Stability, 2001, 74, 2, 239.

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Test Methods for Fire Retardancy 29. ASTM D1356, Test Method for Quantitative Determination of Phases in Portland Cement Clinker by Microscopical Point-Count Procedure, 2012. 30. V. Babrauskas, Development of the Cone Calorimeter, A Bench-Scale Heat Release Rate Apparatus based on Oxygen Consumption, NBSIR 82-2611, US National Bureau of Standards, Gaithersburg, MD, USA, 1982. 31. V. Babrauskas, Fire and Materials, 1984, 8, 2, 81. 32. C-L. Chiang, C-C. Ma, H.R. Chang and S-C. Lu in Proceedings of the 4th Asian Australasian Conference on Composite Materials, Sydney, Australia, 2004, p.748. 33. P-L. Kuo, J-M. Chang and T-L. Wang, Journal of Applied Polymer Science, 1998, 69, 8, 1635. 34. A. Baudrey, J. Dufay, N. Regnier and B. Mortaigne, Polymer Degradation and Stability, 1998, 61, 3, 441. 35. M. Spontón, L.A. Mercado, J.C. Ronda, M. Galià and V. Cádiz, Polymer Degradation and Stability, 2008, 93, 2025. 36. M. Hou, W. Liu, Q. Su and Y. Liu, Polymer Journal, 2007, 39, 7, 696. 37. Y-F. Shih, Y-T. Wang, R-J. Jeng and K-M. Wei, Polymer Degradation and Stability, 2004, 86, 2, 339. 38. H. Liang and W. Shi, Polymer Degradation and Stability, 2004, 84, 3, 525. 39. M. Modesti and A. Lorenzetti, Polymer Degradation and Stability, 2002, 78, 2, 341. 40. M. Modesti, A. Lorenzetti, F. Simioni and G. Camino, Polymer Degradation and Stability, 2002, 77, 2, 195. 41. DIN 4102-2, Behaviour of Building Materials and Components in Fire Building Components - Definitions, Requirements and Tests, 1977. 42. S-B. Kwak and J-D. Nam, Polymer Engineering and Science, 2002, 42, 8, 1674. 43. M. Le Bras, S. Bourbigot and B. Revel, Journal of Materials Science, 1999, 34, 23, 5777.

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Characteristics and Analysis of Non-Flammable Polymers 44. J.E. Connell, E. Metcalfe and M.J.K. Thomas, Polymer International, 2000, 49, 10, 1092. 45. F-Y. Hshieh and H.D. Beeson, Fire and Materials, 1997, 21, 1, 41. 46. S. Bourbigot and M. Le Bras in Fire Retardancy of Polymers, Eds., M. Le Bras, G. Camino, S. Bourbigot and R. Delobel, Royal Society of Chemistry, Cambridge, UK, 1998, p.222. 47. J. Wachowicz, Fire and Materials, 1998, 22, 5, 213. 48. P. Eigenmann, Materie Plastiche ed Elastomeri, 1995, 4, 194. 49. U. Sorathia, J. Ness and M. Blum, Composites Part A: Applied Science and Manufacturing, 1999, 30A, 5, 707. 50. Plastics in Building Construction, 1997, 21, 2. 51. U. Sorathia and C.P. Beck in Proceedings of Improved Fire and Smoke Resistant Materials for Commercial Aircraft Interiors Conference, 1995, p.93. 52. FM 4470, Single-Ply, Polymer-Modified Bitumen Sheet, Built-Up Roof (BUR) and Liquid Applied Roof Assemblies for use in Class 1 and Noncombustible Roof Deck Construction, 2012. 53. UL 1256, Fire Test of Roof Deck Constructions, 2007. 54. UL 1715, Fire Test of Interior Finish Material, 2008. 55. Y. Cai, Y. Hu, L. Song, Y. Tang, R. Yang, Y. Zhang, Z. Chen and W.C. Fan, Journal of Applied Polymer Science, 2006, 99, 4, 1320. 56. S. Chang, T. Xie and G. Yang, Polymer International, 2007, 56, 9, 1135. 57. F.D. Smith, Private Communication. 58. C. Siat, M. Le Bras and S. Bourbigot, Fire and Materials, 1998, 22, 3, 119. 59. L. Du, B. Qu and M. Zhang, Polymer Degradation and Stability, 2007, 92, 3, 497.

40

Test Methods for Fire Retardancy 60. J.H. Koo, S. Lao, W. Ho, K. Ngyuen, J. Cheng, L. Pilato, G. Wissler and M. Ervin in Proceedings of the SAMPE Fall Technical Conference: Global Advances in Materials and Process Engineering, Dallas, TX, USA, 2006, Paper No.32, p.16. 61. L. Wang, Q. Ji, T.E. Glass, M. Muggli, T.C. Ward, J.E. McGrath, G. Burns and U. Sorathia in Proceedings of the 151st ACS Rubber Division Meeting, Anaheim, CA, USA, Spring 1997, Paper No.51, p.13. 62. W. Qiang, C. Zhang, R. Liang and B. Wong in Proceedings of the SAMPE 08 Conference: National and Process Innovations Changing our World, Long Beach, CA, USA, 2008, Volume 53, Paper No.93. 63. T. Kashiwagi, E. Grulke, J. Hilding, K. Groth, R. Harris, K. Butler, J. Shields, S. Kharchenko and J. Douglas, Polymer, 2004, 45, 12, 4227. 64. ASTM D4809, Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter (Precision Method), 2012. 65. ISO 5660-1, Reaction-to-Fire Tests - Heat Release, Smoke Production and Mass Loss Rate - Part 1: Heat Release Rate (Cone Calorimeter Method), 2002. 66. F.D. Hileman, K.J. Vorhees, L.H. Wojcik, M.M. Bikly, P.W. Ryan and I.N. Eihorn, Journal of Polymer Science: Polymer Chemistry Edition, 1975, 13, 3, 571. 67. E.A. Boettner, G. Ball and B. Weiss, Journal of Applied Polymer Science, 1969, 13, 2, 377. 68. J. Michal, J. Mitera and S. Tardon, Fire and Materials, 1976, 1, 4, 160. 69. J. Morikawa, Journal of Combustion Toxicology, 1978, 5, 349. 70. J.C. Liao and R.F. Browner, Analytical Chemistry, 1978, 50, 12, 1683. 71. K.T. Joseph and R.F. Browner, Analytical Chemistry, 1980, 52, 7, 1083. 72. H. Zhang, P.R. Westmoreland and R.J. Farris in Proceedings of the ACS Polymeric Materials Science and Engineering Meeting, Chicago, IL, USA, Fall 2001, 85, 463. 73. H. Zhang, R.J. Farris and P.R. Westmoreland, Macromolecules, 2003, 36, 11, 3944.

41

Characteristics and Analysis of Non-Flammable Polymers 74. T. Zhong, M.M. Maroto-Valer, J.M. Andresen, J.W. Miller, M.L. Listemann, W.R. Furlan and D. Morita, Polymer Preprints, 2001, 42, 2, 687. 75. R.N. Water in Proceedings of the 3rd Triennial International Aircraft Fire and Cabin Safety Research Conference, Atlantic City, NJ, USA, 2001. 76. H. Sato, K. Kondo, S. Tsuge, H. Ohtani and N. Sato, Polymer Degradation and Stability, 1998, 62, 1, 41. 77. Z. Wang, G. Wu, Y. Hu, Y. Ding K. Hu and W. Fan, Polymer Degradation and Stability, 2002, 77, 3, 427. 78. H. Zhang, P.R. Westmoreland, R.J. Farris, E.B. Coughlin, A. Plichta and Z.K. Brzozowski, Polymer, 2002, 43, 20, 5463. 79. Z. Tang, M.M. Maroto-Valer, J.M. Andresen, J.W. Miller, M.L. Listemann, P.L. McDaniel, D.K. Morita and W.R. Furlan, Polymer, 2002, 43, 24, 6471. 80. ASTM D3014, Standard Test Method for Flame Height, Time of Burning and Loss of Mass of Rigid Thermoset Cellular Plastics in Vertical Position, 2011. 81. D. Price, G.J. Milnes and F. Gao, Polymer Degradation and Stability, 1996, 54, 2-3, 235. 82. D. Price, G.J. Milnes, C. Lukas and T.R. Hull, International Journal of Mass Spectrometry and Ion Processes, 1984, 60, 1, 225. 83. D. Price, G.J. Milnes, C. Lukas and A.M. Phillips, Journal of Analytical and Applied Pyrolysis, 1987, 11, 499. 84. D. Price, K.A. Lincoln and G.J. Milnes, International Journal of Mass Spectrometry and Ion Processes, 1990, 100, 77. 85. F. Gao, D. Price and G.J. Milnes, Rapid Communications in Mass Spectrometry, 1997, 11, 7, 791. 86.

J.R. Ebdon, P. Joseph, B.J. Hunt, D. Price, G.J. Milnes and F. Goa in Proceedings of the 8th Annual Conference on Flame Retardancy, Stamford, CT, USA, 1997.

87. D. Price, F. Gao, G.J. Milnes, B. Eling, C.I. Lindsay and P.T. McGrail, Polymer Degradation and Stability, 1998, 64, 3, 403. 88. D. Price, Polymer News, 1999, 24, 3, 88.

42

Test Methods for Fire Retardancy 89. F. Gao, D. Price, G.J. Milnes, B. Eling, C.I. Lindsay and P.T. McGrail, Journal of Analytical and Applied Pyrolysis, 1997, 40-41, 217. 90. J.R. Ebdon, D. Price, B.J. Hunt, P. Joseph, F. Gao, G.J. Milnes and L.K. Cunliffe, Polymer Degradation and Stability, 2000, 69, 267. 91. D. Price, C. Lukas, G.J. Milnes, R. Whitehead and I. Schopov, European Polymer Journal, 1993, 19, 3, 219.

43

Characteristics and Analysis of Non-Flammable Polymers

44

3

Building Construction Materials, Industrial Applications and Furnishings

3.1 Building Applications The construction field is forced to comply with the most encompassing set of regulations. In Germany the requirements for fire prevention and protection are contained in or regulated through zoning regulations, building permits, and guidelines, as well as construction-specific codes such as DIN 4102-7 [1]. Analogous regulations are promulgated through, for example, the building regulations in the UK, building codes in the USA, or the guidelines of the fire police in Switzerland. According to DIN 4102-7 [1], combustible building materials are categorised into ‘B1: schwerentflammbar (heaving burning), B2: normal entflammbar (normal burning) or B3: leichtenflammbar (light burning)’, using both a small burner test and a large chimney test procedure. The small burner test consists of a vertically oriented specimen, which is exposed on either edge or side to a specific ignition flame for 15 seconds. To obtain a B2 classification, the flame front may not have reached a previously marked line at 150 mm within a 20 second time interval inclusive of the 15 second flame exposure time. The test for possible B1 performance uses four vertically arranged test samples, 1000 × 190 mm. The samples, in this in case a chimney arrangement, are exposed to a flame source at their lower edge using a gas ring burner for periods of ten minutes. Test criteria consist of use of an undamaged length of sample and control of combustion gas temperatures. Dripping behaviour, if any, is noted even though it is not part of the test classification. However, such an observation may be required to obtain the necessary building permits. Enhanced tests and performance criteria have been developed for classification of composites into B1, B2, and B3 categories. Floor coverings are evaluated for B1 performance, using both a critical flux test and a modified small burner test procedure. To obtain a B2 rating using this modified test requires an increased time of 30 seconds. The critical radiant flux test measures the contribution to flame spread of a horizontally oriented test sample. The sample is exposed to a radiant energy flux of varying intensity. The flames may not propagate past the 0.45 W/cm2 exposure limit. This so-called ‘critical limit’ was determined using wood parquet flooring.

45

Characteristics and Analysis of Non-Flammable Polymers Single burning item test for class B, C, and D materials or intermediate combustibility have been introduced [2] and equipment is now available for carrying out six new test methods for European-wide classification of construction products. It has proved difficult to determine any correlation between the test results of the various national procedures [3]. Because of this, the experts of TC92 of the International Standards Organization (ISO) have undertaken the development of a test procedure to characterise independently, ignitability, flame spread, rates of heat release, and other fire related parameters [4–6]. Worldwide efforts continue to correlate laboratory tests to real life fires [4]. Examples of such programmes are the corner test programme carried out by Factory Safety Manual and the corrugated metal tool deck [7-9] trials carried out by the Netherlands Organisation for Applied Scientific Research (TNO). The corner test has been used to determine the fire behaviour of rigid foam materials when exposed to a severe wood fire. Construction elements and special constructions: The fire resistance of constructions that form an enclosed space is determined by the phenomenon of flashover, i.e., the extension of the fire from the room of origin to adjacent spaces. Containment of the fire is through a sufficiently high fire resistance performance of the components forming the enclosed space, such as walls, ceilings and doors. For proper classification, it is necessary to ensure that construction details, such as holes for cables, water, or other piping, as well as joint details, do not result in weak spots allowing fire penetration. To assess fire safety of construction components properly, their performance is determined relative to thermal loading of the panels using a standard time-temperature profile in DIN 4102-7 [1]. Such a profile has been adopted both nationally and as ISO 834-1 [10]. Construction elements are assembled into the wall or ceiling test furnace in the same form as they would be used. The elements are then subjected to the standard time-temperature exposure for the time interval corresponding to the rating desired. Acceptance requires that fire breakthrough does not occur, that structural integrity be preserved, and that temperature gradients remain within specified limits. In Germany, speciality constructions such as parapets have reduced fire performance requirements because of the lower fire risk associated with such applications. The reduced test conditions essentially consist of a modified (flattened) standardised curve according to DIN 4102-3 [11]. For single case evaluation of the fire performance of parapet elements, application-like model tests can be conducted using a test device currently used for testing facades [12]. Roofing is evaluated for fire spread caused by external fire sources and radiant heat. According to DIN 4102-7 [1] the fire source consists of 600 g of wood shavings. The test is carried out at roof inclinations of 15° and 30º. Neither burn-through nor unacceptable fire spread may occur in order to pass the performance criteria. The

46

Building Construction Materials, Industrial Applications and Furnishings corresponding testing in the Netherlands is regulated under NEN 6065 [13] and NEN 6066 [14]. For proper risk assessment of the fire performance of metal roof constructions, model fire test studies were done [15]. The trials carried out by TNO indicated that the fire performance classification of the insulation was the main factor influencing fire spread along the upper roof system to adjacent sections. Sommer [16] has discussed the suitability of halogen-free fire retardant systems from meeting the specifications of fire regulations in the building, rolling stock and electrical industries. Representatives of various industries [17] have examined some smoke depressants and flame retardant resins introduced by various US Companies in relation to US legislation. These include smoke suppressed polyvinylchloride (PVC) (BF Goodrich) and polyurethane (PU) foams (Mobay Chemical), and smoke suppressant additives from Climax Molybdenum, and Sherwin-Williams (molybdenum compounds), Solem Industries, and Alcoa Chemicals (aluminium trihydrates, for polypropylene (PP) and PVC), Dover Chemical Corp., (aromatic bromine compound for PP), and US Borax (zinc borate).

3.1.1 Building Wrap CSIRO, Australia [18] claim that plastic building wraps are being disadvantaged because of anomalies in the Building Code of Australia requirements relating to flammability testing. A wrap material must have a certain flammability index when tested in accordance with the Australian Standard AS 1530.2 [19]. Meaningful results for plastics-based materials cannot be obtained from this test, which was devised for cellulose-based materials. Plastics-based building wraps are further disadvantaged in Australia from the loading classification they receive by having their loading related to tensile strength.

3.1.2 Roofing Following the fire in 1953 at General Motors’ (GM) transmission plant in Livonia, Michigan, it was realised that there was a need for test methods for roofing systems. Also, there was a need for a method for measuring and evaluating smoke production from polystyrene foam. The GM fire involved a localised internal fire, which spread, fuelled by the roof covering assembly to eventually engulf the whole building. Details are given of a new UL test method, which uses oxygen consumption calorimetry to

47

Characteristics and Analysis of Non-Flammable Polymers quantify the roof covering materials’ consumption to the underdeck fire sources by capturing effluent from beneath the roof assembly and recording the rate of heat production in kW per minute. In North America, polyisocyanurate (PIR) insulation is used heavily in commercial roofing applications [20]. It has high thermal resistance and good fire properties, making it the best insulation choice. It has been known for a while that the initial thermal resistance of PIR boards will change very slowly over time. Because the lifetime of such products is long, thermal ageing is caused by the diffusion of a multitude of gases, and the insulation product is not homogeneous. The PIR industry has now identified a test method based on a Canadian Standard, CAN/ULC S770 [21], which defines the long-term thermal resistance (LTTR) as the average weighted thermal resistance over a 15 year period. One of the objectives of this paper was to compare the LTTR value predicted by this test method to those obtained from the mathematical modelling and calculation algorithms. Another aim of this study [20] was to compare the thermal resistance of pentane-blown polyurethane PIR laminate boards aged in a laboratory environment since early 1998 to those obtained from the mathematical modelling and calculation algorithms [22].

3.1.3 Air Handling Ducts Julius [23] has discussed air-handling ducts with respect to flammability and flammability testing. The importance of corrosion resistance is also emphasised. A new performance phenolic resin (phenol resorcinol resin) was developed for usage in fibre glass reinforced plastics. It offers a flame spread and smoke rating of 10 without the usage of any additives. The product offers outstanding heat stability and aging properties to the point where continuous operating temperatures can exceed conventional thermoset resins. Its corrosion resistance in numerous organic and inorganic environments is excellent at elevated temperatures. Julius [23] discusses the ASTM E84 Tunnel Test [24] for determining flame spread and smoke density. This test is run in a 7.6 m long by 60 cm wide furnace. Two gas ports are located at the air inlet or the fire end of the test chamber. The test specimen is placed in the test chamber 19 cm above the gas ports and is sealed with an asbestos-cement board and an airtight metal lid. A thermocouple is located at the 7 m mark and records the temperature during the test run. The readings of time versus temperature are used to determine the fuel contributed. A series of windows are located along the side of the furnace to allow observation of the flame front. A light source and photoelectric cell are located in the vent pipe at least 4.9 m from the vent end of the chamber. The light absorption is used to calculate the smoke developed. A calibration run is made with asbestos cement board, which represents a 0

48

Building Construction Materials, Industrial Applications and Furnishings classification. During a test, the gas burners are ignited and the flame should extend to 1.4 m down the funnel on the surface of the material being tested. Temperature and smoke readings are automatically recorded. An observer watches the flame front and records the position of the flame front every 30 seconds for a period of 10 minutes. The flame spread is calculated from a graph of the distance versus time. The area under the curve of this graph is determined after subtracting 1.4 m from the distance values, since this is the length of the gas flames. Often during a test of highly fire retardant plastic, the flame front recedes after burning through the material immediately over the gas flame. When plotting the flame spread rating curve, the distance value never recedes, and the maximum value is plotted to the 10 minute mark. For example, if the flame spread reaches 3.7 m at 6 minutes and then recedes, the graph area will remain at the 3.7 m mark from 6 minutes to 10 minutes. The smoke results are calculated by determining the area under the light absorption versus time curve, dividing by the light absorption versus time curve obtained using red oak as a standard material, and multiplying by 100. Overall, the tunnel test is conceptually simple, provides a large enough surface area to simulate a real fire, and gives reasonably reproducible results. Table 3.1 depicts the flame spread and smoke density values for various premium fire retardant resins. All products meet a class 1 flame spread rating with the phenol resorcinol product providing an outstanding value of 10.

Table 3.1 Flame spread and smoke density values for various resins – all tests conducted per the ASTM E84 [24] tunnel test* Resins Phenol resorcinol Brominated bisphenol A polyester a

Brominated bisphenol A epoxy vinyl ester a

Flame spread

Smoke density

10

10

15

600-800

20

600-800

: Contains 5% antimony trioxide.

* All laminates consisted of 1 ply C-glass veil and 2 plies of chopped strand mat followed by 1 ply C-glass veil. Reproduced with permission from W.H. Julius in Proceedings of the Composites Institute 45th Annual Conference, Washington, DC, USA, 1990, Paper No.2-D. ©1990, Composites Institute [23]

49

Characteristics and Analysis of Non-Flammable Polymers

3.2 Harmonisation of Fire Safety Assessments Moves to harmonise fire safety assessment for building products in Europe has sparked a major shake-up in the flammability testing and classification of polymer materials [2]. As far back as 1998, over 30 tests were in use and more have been developed since then. The most radical change will be the introduction of the Single Burning Item for class B, C and D materials of intermediate combustibility, including most plastics. Two of the tests – a furnace test for non-combustibility and the oxygen bomb calorimeter – are used to classify the least combustible materials (classes A and B) and will apply to both flooring and non-flooring products. Flooring products are also be tested by two further tests including the floor radiant panel, while non-flooring products of appreciable combustibility, in classes E and F, are tested by an existing small burner test. However, the most radical change is in the introduction of the single burning item (SBI) test, for class B, C, and D materials of intermediate combustibility, including most plastics. Work on this test was led by the Fire Research Station at the Building Research Establishment at Garston near Watford, as the UK representative in the EC laboratories group. The SBI test was developed to simulate a single item burning close to the corner of a room, which is considered a worst-case scenario. As an intermediate scale test, it is intended to address conflicting concerns over the cost of full-scale testing and the validity of bench testing of small samples. Basically the test involves mounting a corner section specimen – a vertical 1.5 m high by 1.0 m wide panel and another 1.5 m by 0.5 m at 90 degrees – under an enclosed calorimeter hood. The Fire Research Station says the setup can accurately measure the rate of heat release, considered one of the most important parameters in assessing fire growth, also time to ignition, rate of lateral flame spread, time of production of flaming droplets and rate of smoke release. A full summary of publishing standards for the evaluation of construction materials is given in Appendix 3.1.

3.3 Mining Applications Mining applications require that specific test criteria be met because of the extraordinary difficulties in rescue and fire extinguishing efforts underground. Highly expandable and combustible blowing agents may not be used if they increase the fire hazard underground. In case of an accidental fire, the blowing agents used

50

Building Construction Materials, Industrial Applications and Furnishings should not propagate the fire. The tunnel test facility as per DIN 22118 [25] is used, for example, to evaluate the contribution to fire spread of conveyer belts with textile inserts, such as would be used in anthracite mines. The test samples measure 1200 × 90 mm and are placed horizontally into the laboratory test tunnel. The test sample is exposed from underneath to the flame of a special propane burner for a period of 15 minutes. The burner is positioned 170 mm from the front edge of the sample. A maximum burn extent and afterburn are specified in order to meet the minimum test criteria. The basis for the standardisation of this test procedure was a series of full-scale tests carried out by the Tremonia Mining Organisation in Dortmund, Germany. Wachowicz [26] has discussed the theoretical basis for calculation of heat release rate (HRR) during burning of conveyor belts in a fire-testing gallery. Taking as an example the results of measurements of oxygen, carbon dioxide and carbon monoxide content in the products of combustion of conveyor belts during the testing of their flammability, the possibility has been demonstrated for using the calculations of HRR in an assessment of conveyor belt flammability. The total quantity of heat released during the belt fire can provide the basis for developing a new method of testing as well as the criteria for assessment of fire resistance of the conveyor belts using oxygen consumption calorimetry. The determination of the flammability of the conveyor belt is based on the results obtained in the drum friction test and in the full-scale gallery fire test [27–30]. The method of full-scale gallery fire test enables the basic characteristics of the fire safety to be determined including the property of the belt self-extinguishing outside the seat of the fire, and thereby determines the possibility of the fire spreading along the conveyor to other areas of the mine. This method, similar to other traditional flame methods only, enables one to observe the results of the influence of the fire after finishing the test and making the measurements of the remaining quantities after extinguishing the fire of the belt sections under test. In the 1980s, in the USA and Europe, new methods of testing the flammability of materials were introduced. They rely on calculating the HRR of materials from the rate of oxygen consumption. Huggett [31] calculated the heat released per unit mass of oxygen consumed for the organic materials in the burning process. He also proved that the effect of incomplete combustion and differentiation of the burnt materials has only a slight influence on the results obtained. These findings were of basic importance for the development of new methods of testing the flammability of materials using this relationship. The HRR is, at present, one of the most important parameters used in the assessment of the fire hazards related to the use of organic materials.

51

Characteristics and Analysis of Non-Flammable Polymers The trials undertaken to calculate the HRR have shown that this parameter can be used to obtain an adequate correlation of the course of burning of the belt in the full-scale gallery fire test. This makes it possible to develop a fast method of testing the flammability of conveyor belts by oxygen consumption calorimetry. Wachowicz [32] in his original paper investigates the fire testing gallery method further. The full-scale testing of the flammability of conveyor belts are carried out in the experimental fire gallery with the cross-section of 3.57 m2 and a length of 100 m. The gallery is made of chamotte brick and the roof is semi-spherical in shape. According to the combustion test measurements in the fire-testing gallery, as presented in the Polish PN-93/C05013 [33] a standard 42 m long and 0.5 m wide section of the belt is taken for testing. The belt is placed 1 m above the floor on steel rods. The flame source is 300 kg mass of dry pine wood with a humidity of 10 ± 3%. Ventilation air is provided by a fan located at the gallery intake. The velocity of air fed into the gallery is 1.2 m/s. During the belt combustion, the temperature inside the gallery is measured, also the concentrations of carbon monoxide, carbon dioxide and oxygen. The heat release Q can be calculated from the equation:

Q = ;1 -

A Z c 1 + 0.1715 X CO mE 15.437 0.265 X AO 2

Where: Z = XAO2 (1 - XAO2 – XACO – XACO2) XACO = the carbon monoxide concentration in the air leaving the gallery. XAO2 = the concentration of oxygen in the air leaving the gallery. XACO2 = the concentration of carbon dioxide air leaving the gallery. The dependence of the amount of heat released in the course of combustion of a conveyor belt in a fire-testing gallery defines the dynamics of the belt combustion process. This relationship provides valuable information for the determination of the hazard related to the use of conveyor belts in mines [32]. Also, the calculations of the HRR during burning of the conveyor belts in the fire

52

Building Construction Materials, Industrial Applications and Furnishings testing gallery can be the basis of the development of a new method for conveyor belt testing. In further work Wachowicz [26] compared large-scale gallery testing with cone calorimetry in the evaluation of the flammability of conveyor belts. A good correlation is shown between results of conveyor belt flammability during combustion in a fire testing gallery and predicted HRR based on bench scale cone calorimetry. The conveyor belt flammability investigations were carried out using a standard cone calorimeter. The testing of conveyor belt flammability using a cone calorimeter was to the standards, ISO 5660-1 [34] and ASTM E1354 [35].

3.4 Furnishing Materials Based on detailed fire statistics [36-38] the UK has prepared fire legislation law using test and performance criteria of BS 5852 [39]. As in the USA [40], the primary consideration is the reduction of the fire risk in homes from cigarette ignition sources. In those cases where the cigarette ignition and/or the simulated match ignition conditions are not successfully passed, the furniture must be labelled to that effect and identified. All furniture is required to pass this cigarette ignition test. The test procedures are based on numerous full-scale model fire tests that were done worldwide. Aside from governmentally required testing [41, 42], industry carried out extensive testing and trials to ensure statistically correct test and performance criteria [43-47]. The British Property Service Agency responsible for furniture procurement, requires application-oriented tests with correspondingly staggered ignition sources from cigarettes to a wooden crib [48]. Squires [49] investigated the use of melt blendable phosphorus/bromine flameretardants in PP woven and non-woven fabrics and carpets. Consistent high quality injection moulded parts met V2 ratings in the UL 94 test. Good results are easily achieved with minimal fire retardant loading or the use of a synergist. The US additionally imposes materials-specific requirements. Examples of these are the California State statutes and the regulations of the New York Port Authority [50] for cushioning materials, which must meet the construction-specific tests such as ASTM E162 [15] and ASTM D2843 [15]. If the cushioning materials fail, upholstery combinations may be substituted. Handermann [51] has discussed the use of flame retardant PU for furniture and home upholstered furnishings, particularly bedding.

53

Characteristics and Analysis of Non-Flammable Polymers Handermann [52] has also discussed the statistics underlying the US effort to render home furnishings safe by imparting to them safe effective open-flame resistance. Also developments in flame-resistant barrier technology using Bazofil melamine fibre are summarised. Test results in both bedding and upholstered furniture applications are also examined. A classification scheme to produce optimum fibre blends to make flame resistant bonded highloft products is described. Blends of Bazofil, Visil, modacrylic and low-melt polyester fibres, in thermally bonded highloft form, are shown to provide a cost-effective, high-performance flame resistant barrier product for the home furnishings market. A patented core-spun yarn technology, consisting of fine denier glass filament, wrapped with Bazofil, modacrylic and polyester fibres was also shown to provide a suitable product for this market. Bazofil/polyester blends, which retain the features of polyester fibrefill, can be made to prevent flame penetration in horizontal test procedures. A full summary of standard test procedures for the evaluation of the retardancy in furnishings is given in Appendix 3.11.

References 1.

DIN 4102-7, Fire Behaviour of Building Materials and Building Components - Part 7: Roofing, Definitions, Requirements and Testing, 1998.

2.

Plastics and Rubber Weekly, 1998, 1730, 9.

3.

H.W. Emmons, Fire Research Abstracts and Reviews, 1968, 10, 2, 133.

4.

ISO TR 3814, Test for Measuring ‘Reaction-To-Fire’ of Building Materials – their Development and Application, 1989.

5.

ISO 5658-2, Reaction to Fire Tests – Spread of Flame Test – Part 2: Lateral Spread on Building and Transport Products in Vertical Configuration, 2011.

6.

ISO 5659-2, Plastics – Smoke Generation - Part 2: Determination of Optical Density by a Single-Chamber Test, 2012.

7.

A Fire Study of Rigid Cellular Plastic Materials for Insulated Wall and Roof/ Ceiling Constructions, Factory Mutual Research Corporation, USA, 2000.

8.

H. Zorgmann in Proceedings of the 5th International Brandshutzseminar Conference, Karlsruhe, Germany, 1976.

9.

F.H. Prager and H. Zorgmann, Kunststoffe im Bau, 1979, 14, 2, 57.

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Building Construction Materials, Industrial Applications and Furnishings 10. ISO 834-1, Fire Resistance Tests - Elements of Building Construction – Part 1: General Requirements, 2012. 11. DIN 4102-3, Fire Behaviour of Building Materials and Building Components; Fire Walls and Non-Load-Bearing External Walls; Definitions, Requirements and Tests, 2009. 12. W. Klöker, H. Niesel, F.H. Prager, H.W. Schiffer, O. Bökenkamp and H.G. Klingelhöfer, Kunststoffe, 1997, 67, 8, 438. 13. NEN 6065, Determination of the Contribution to Fire Propagation of Building Products, 1997. 14. NEN 6066 Determination of the Smoke Production during Fire of Building Products, 1997. 15. ASTM D2843, Test Method for Density of Smoke from the Burning or Decomposition of Plastics, 2010. 16. M. Sommer, Kunststoffe Plast Europe, 2000, 90, 6, 29. 17. Plastics World, 1982, 40, 55. 18. Plastic News International, 2000, p.34. 19. AS 1530.2, Methods for Fire Tests on Building Materials, Components and Structures - Test for Flammability of Materials, 1993. 20. Plastics in Building Construction, 1997, 21, 2. 21. CAN/ULC S770, Standard Test Method for Determination of Long-Term Thermal Resistance of Closed-Cell Thermal Insulating Foams, 2009. 22. S.N. Singh, M. Ntiru and K. Dedecker, Rubber and Plastics News, 2003, 32, 18, 15. 23. W.H. Julius in Proceedings of the SPI Composites Institute - 45th Annual Conference, Washington, DC, USA, 1990, Paper No.2-D. 24. ASTM E84, Test Method for Surface Burning Characteristics of Building Materials, 2012. 25. DIN 22118, Conveyor Belts with Textile Plies for use in Coal Mining - Fire Testing, 1991.

55

Characteristics and Analysis of Non-Flammable Polymers 26. J. Wachowicz, Fire and Materials, 1998, 22, 5, 213. 27. J. Wachowicz in Proceedings of the 2nd International Conference on Conveyor Belt Transportation in Mining, Ustroń, Poland, 1994. 28. J. Wachowicz and B. Matecki in Scientific Works of Institute of Mining and Engineering, Technical University of Wroclaw, Wroclaw, Poland, 1992, 68, 191. 29. B. Matecki and J. Wachowicz in Problems Involved in the Application of the Drum Friction Test for Evaluating Fire Resistant Rubber Conveyor Belts in the Mining Industry, Przegląd Gόrniczy, Poland, 1992, 10, 10. 30. J. Wachowicz in Proceedings of the Flame Retardants 96’ Conference, London, UK, 1996, p.253. 31. C. Huggett, Fire and Materials, 1980, 4, 2, 61. 32. J. Wachowicz, Fire and Materials, 1997, 21, 6, 253. 33. PN 93/C-05013, Slow-Burning Conveyor Belts - Methods of Testing of SlowBurning, 1993. 34. ISO 5660-1, Reaction-to-Fire Tests − Heat Release, Smoke Production and Mass Loss Rate - Part 1: Heat Release Rate (Cone Calorimeter Method), 2002. 35. ASTM E1354, Test Method for Heat and Visible Smoke Release Rates for Materials and Products using an Oxygen Consumption Calorimeter, 2011. 36. S.E. Chandler, The Incidence of Residential Fires in London – The Effects of Housing and Other Social Factors, BRE Information Paper, IP 20/79, BRE, Borehamwood, Hertfordshire, UK, 1979. 37. S.E. Chandler in Some Trends in Furniture Fires in Domestic Premises, BRECP 66/76 BRE, Borehamwood, Hertfordshire, UK, 1976. 38. S.E. Chandler and R. Baldwin, Fire and Materials, 1976, 1, 76. 39. BS 5852, Methods of Test for Assessment of the Ignitability of Upholstered Seating by Smouldering and Flaming Ignition Sources, 2006. 40. W.G. Berl and B.M. Halpin, Fire Journal, 1979, 105.

56

Building Construction Materials, Industrial Applications and Furnishings 41. K.N. Palmer, W. Taylor and K.T. Paul in Fire Hazards of Plastics in Furniture and Furnishings: Characteristics of the Burning, BRE-CP 3/75, HMSO, London, UK, 1975. 42. K.N Palmer, W. Taylor and K.T. Paul in Fire Hazards of Plastics in Furniture and Furnishings: Fully Furnished Rooms, BRE-CP 21/76, HSMO, London, UK, 1976. 43. W.J. Wilson in Proceedings of the SPI 4th Annual Combustion Symposium, London, UK, 1975, p.62. 44. F.H. Prager in Proceedings of the 5th International Conference Brandshutzseminar, Karlsruhe, Germany, 1976. 45. R.P. Marchant in The Ignitability of Upholstery by Smokers’ Materials, FIRA, Stevenage, UK, 1977. 46. Requirements, Test Procedure and Apparatus for Testing the Flame Retardance of Upholstered Furniture, State of California Technical Information Bulletin 116, State of California, Department of Consumer Affairs, Bureau of Home Furnishings and Thermal Insulations, North Highlands, CA, USA, 2000. 47. Requirements, Test Procedure and Apparatus for Testing the Flame Retardance of Resilient Filling Materials Used in Upholstered Furniture, State of California Technical Information Bulletin 117, State of California, Department of Consumer Affairs, Bureau of Home Furnishings and Thermal Insulations, North Highlands, CA, USA, 2000. 48. DOE/PSA, Fire Retardant Specifications No.551, Department of the Environment, London, UK. 49. G.E. Squires in Proceedings of the Flame Retardants ’96 Conference, London, UK, 1996, p.107. 50. Specifications Governing the Flammability of Upholstery Material and Plastic Furniture, The New York Authority, NY, USA, 1977. 51. A.C. Handermann in Proceedings of the Alliance for the Polyurethanes Industry - Polyurethanes EXPO 2003 Conference, Orlando, FL, USA, 2003, p.349. 52. A.C. Handermann, Journal of Industrial Textiles, 2004, 33, 3, 159.

57

Characteristics and Analysis of Non-Flammable Polymers

58

4

Applications of Fire Retardant Polymers: Electrical Applications

In Germany performance requirements for electric applications are regulated through VDE and DIN EN guidelines [1, 2]. Localised smouldering or ignition may result from overhead wires, sparking contacts, or other failures of electrical equipment. Underwriter Laboratories, Inc., (UL) has developed universally applicable fire protection test procedures. According to UL 94 [3] (see Table 2.1) horizontally (or if applicable, vertically) oriented test samples are exposed to a gas flame source. Test criteria consist of the rate of burning, the burn distance, or the continued burning of test samples themselves and/or drippings from melted materials after removal of the flame source. Tests have been reported for polyamide-6,6 formulations containing melamine polyphosphate as flame retardant [4], ethylene-vinyl acetate copolymer containing ammonium polyphosphate as flame retardant [5], and elastomer materials [6]. A horizontal test procedure using a 30 second flame exposure is used for determining the Horizontal Burn classification. This test is analogous to ASTM D635 [7] (Table 2.1) and the discontinued ASTM D1692 [8]. Bar-like samples measuring 127 × 12.7 × 6.4 mm are used in both the vertical and the horizontal test procedures. The vertical test procedure also requires that the test specimens be conditioned for seven days at 70 ºC [3, 9]. The sample is ignited at the lower end. The afterburn time of the sample or dripped material is used for classifying samples as V0, V1 or V2. The ASTM E162 test procedure [10] normally used for construction applications is used to test larger-sized electrical boxes or housings. The requirements for such are outlined in UL 94 [3]. In this test, the contribution of the sample to surface flame spread is measured under conditions where the sample is exposed to a specified radiant heat flux. Another application-specific procedure is the test for hot wires or contacts [5] according to DIN EN ISO 60695-5-1 [11] in which the sample is exposed to a glowing wire at a temperature between 550 and 960 ºC. Potential ignition sources through failure of overhead wires or termination screws are simulated in this procedure. The performance of insulation is determined by contact with hot, glowing wires. The test procedure specifies stepwise increasing temperatures in the range 450–906 ºC when wire temperatures at the point of failure are determined.

59

Characteristics and Analysis of Non-Flammable Polymers Test criteria include ignition time, dripping, and subsequent burning. The insulation test sample is moulded on a movable fixture and pressed against the hot wire loop with a force of 1 N. The penetration distance is restricted. The exact temperature of the wire loop is measured with a miniature thermocouple. UL 746C [12] provides general guidelines (including required flammability ratings) for materials employed in electrical enclosures. However, when an end-product standard calls for more stringent requirements than those of UL 746C, the more stringent requirements take precedence. The failure of electrical appliances or fixtures can initiate smouldering, which could lead to localised fires, such as are simulated in, for example, DIN EN 60695-11-5 [13], through, for example, flame exposure from a Bunsen burner. Depending on the application (TV cabinets, cables and so on), other fire sources are used. A widely used test procedure is the glowing rod test. Here a rod-shaped test sample is pressed tip-to-tip against a glowing rod heated to 960 ºC with a force of 1 N. Test criteria specify burning rate and extent. Flame retardancy for electrical and electronic appliances and wiring has been discussed by various workers including Dawson and Landry [14] and Canaud and co-workers [15]. Porro [16] investigated the electrical properties of filled and unfilled aliphatic polyketones [15]. Flame-retardant thermoplastic elastomers have been discussed by DeMaio and Baushke [6]. The corrosiveness of combustion products has been considered in a variety of ways in relation to actual fire damage as well as large scale experiments. Electrical insulation studies have been carried out [17-19] using the combustion tube apparatus to provide the data necessary for standard work. DIN EN 50267-2-1 [20] provides information concerning test and performance criteria for the determination of the corrosiveness of combustion products from fires of electrical origin [20–23]. Gareiss [24] has discussed problems associated with the use of halogen-containing flame retardants in plastics. Developments by BASF in halogen-free flame-retardants based on red phosphorus, magnesium hydroxide and organic nitrogen compounds are reviewed and the use of these additives in engineering plastics for electrical applications and machines are examined. Flame-retardants based on red phosphorus are often used, for example, in the fabrication of polyamide-6 circuit breakers and terminal blocks [25]. These have excellent insulating properties and heat ageing in addition to excellent flame retardant behaviour and their toughness and rigidity are good. Eigenmann [26] presents data on oxygen index, toxicity index and smoke density of polymers, which contain different flame-retardants. Other flame-retardant polymers can also be used. 60

Applications of Fire Retardant Polymers: Electrical Applications Low smoke fire retardant polymers are obviously of great interest in the electrical and other industries. Details are given of a flame-retardant, low-smoke thermoplastic compound with good moisture resistance and hot pressure performance, which was developed by AEI Compounds to meet the requirements of limited toxic/corrosive fume emission in cable insulation. Available in a natural colour, black, or ultraviolet-stabilised, Catapyrric TP544 has been designed for easy processing and has a high melt flow index whilst maintaining good mechanical properties. The datasheet presents technical data on the physical, mechanical, thermal, fire and electrical properties of the grade, while guidelines are also given on extruder temperatures conditions, head and tool design, masterbatch addition, storage and shelf life. DeMaio and Baushke [6] used flammability tests to select elastomeric materials, which meet industry flammability standards, with the emphasis on elastomeric materials for mass transit applications and electrical applications. The intricacies of the UL 94 V0 listings are briefly considered, flammability ratings for cellular silicones are tabulated and regional fire testing services and UL laboratories in the USA and Canada are listed. To reduce the likelihood that a system will experience fire, many Companies write UL V0 listings into contract requirements when purchasing electrical enclosures. The UL V0 listing is a stringent flammability test for elastomers. But just because a material can serve in high temperature applications, does not automatically guarantee that it has adequate flammability resistance to qualify for the UL 94 V0 rating. A case in point is the various brands of silicone. As a class of materials, silicone retains its dimensional stability and resistance to compression set at continuous use temperature up to 199 ºC. When exposed to burning conditions, however, not all brands of silicone pass the UL V0 test. Several elastomers including Neoprene, polyurethane, silicone and ethylene-propylenediene monomer rubber were tested according to the UL 94 V0 procedure. Each material was exposed to flame for two, one second intervals. To pass the test, each individual specimen had to cease burning 10 seconds after flame application. Of these, only a cellular silicone called Bisco passed while another manufacturer’s silicone severely charred and supported a flame. Similarly, in a 60 second UL heat flammability-1 (HF-1) test, a sample of the same cellular silicone met test criteria while another silicone curled and burned, failing the test requirements. The difficulty of getting a UL V0 rating is further complicated by the fact that pigmentation can affect the flammability of an elastomer. Some typical flammability

61

Characteristics and Analysis of Non-Flammable Polymers ratings for cellular silicones are listed in Table 4.1. The electrical applications of various types of polymers are reviewed in Table 4.2.

Table 4.1 Flammability ratings for bisco cellular silicones Flame Relative Fire, smoke and toxicity Industry Designation class hardness Extra soft

Soft

Medium

Firm

Extra firm

BF-1000

UL 94 V0 and HF-1 [3]

ASTM E162 [10], ASTM E662 [27],

Rail

ASTM D3675 [28] and BS 6853 [29]

Aircraft

FAA AC 25.853-1 [30]

Rail/aircraft

and BSS 7239 [31]

HT-870

UL 94 V0 and FAA AC 25.853-1 [30] UL 94 HF-1

HT-800

UL 94 V0 ASTM E162 [10], ASTM E662 [27], and ASTM D3675 [28] and BS 6853 [29] UL 94 FAA AC 25.853-1 [30] HF-1

HT-820

UL 94 V0 and FAA AC 25.853-1 [30] UL 94 HF-1

HT-840

UL 94 V0 ASTM E162 [10], ASTM E662 [27] and UL 94 FAA AC 25.853-1 [30] HF-1

Aircraft

Rail Aircraft Rail/aircraft

Aircraft

Rail Aircraft

Reproduced with permission from DeMaio and S. Baushke, Machine Design, 2002, 74, 52. ©2002, Penton Media, Inc., [6]

62

Applications of Fire Retardant Polymers: Electrical Applications

Table 4.2 Flame retardant polymer uses – electrical applications Polymer

Testing

Fire retardant additive

Application

Reference

Rubber

Flammability

Cable insulation for high tension, low tension cables

-

[32]

Polypropylene

Glow wire rating

Electrical

-

[33]

Wire and cable insulation

Aluminium hydroxide

[15]

Electrical insulation

Aluminium hydroxide

[34]

Ethylene-propylenediene - carbon black - Ageing tests aluminium hydroxide Ethylene-propylenediene - carbon black - Flammability aluminium hydroxide Polyamides Flame retardancy

Electrical

Polyamide, 30% glass Ignition resistance fibre filled

Control switchgear

Polyphenylene ether

-

Circuit boards

Polycarbonate

V0 rated flame retardant

Electrical

Polystyrene

-

Polystyrene

Polystyrene Polyvinyl chloride

Polyvinyl chloride

-

Fire resistance glow wire test -

-

Flame resistant polyethylene terephthalate Brominated epoxy compound

[35]

-

[39]

Electrical and electronic equipment Ethane 1,2 bis (penta Television and business bromophenyl) machines and ethylene bis (tetra-bromide phthalimide) Hexabromo Fire boxes, switch gear cyclodecane

[36] [37, 38]

[14]

[40]

[41]

Electrical

Brominated flame retardant

[42]

Cable insulation

Aluminium trihydrate antimony trioxide

[43]

Optical and electrical application

-

[44]

-

[45]

Thermoplastic polyester-silicone

-

polyimide Depending on glow wire ratings between Polypropylene 750 and 960 ºC, V0 Electrical application or V2 flammability rating Source: Author’s own files

63

Characteristics and Analysis of Non-Flammable Polymers Standard test procedures for the evaluation of fire retardancy of polymers used in electrical applications are reviewed in Appendix 3.5.

References 1.

DIN VDE 0472-814, Testing of Cables, Wires and Flexible Cords Continuance of Insulation Effect Under Fire Conditions, 1991. [In German]

2.

DIN EN 60950-1, Information Technology Equipment - Safety - Part 1: General Requirements, 2012.

3.

UL 94, Tests for Flammability of Plastics Materials for Parts in Devices and Appliances, 2012.

4.

F. Dabrowski, M. Le Bras, R. Delobel, D. Le Maguer, P. Bardollet and J. Aymani in Proceedings of a BPF and Interscience Conference: Flame Retardants 2002, London, UK, 2002, Paper No.15, p.127.

5.

M. Le Bras, S. Bourbigot, C. Siat and R. Delobel in Fire Retardancy of Polymers: the use of Intumescence, Eds., M. Le Bras, G. Camino, S. Bourbigot and R. Delobet, Royal Society of Chemistry, Cambridge, UK, 1998, p.266.

6.

C.W. DeMaio and S. Baushke, Machine Design, 2002, 74, 4, 58.

7.

ASTM D635, Test Method for Rate of Burning and/or Extent and Times of Burning of Plastics in a Horizontal Position, 2010.

8.

ASTM D1692, Standard Method of Test for Flammability of Plastic Sheeting and Cellular Plastics, 1976.

9.

UL 1416, Overcurrent and Overtemperature Protectors for Radio- and Television-Type Appliances, 2012.

10. ASTM E162, Test Method for Surface Flammability of Materials using a Radiant Heat Energy Source, 2012. 11. DIN EN 60695-5-1, Fire Hazard Testing – Part 5-1: Corrosion Damage Effects of Fire Effluent – General Guidance, 2003. 12. UL 746C, Polymeric Materials – Use in Electrical Equipment Evaluations, 2012.

64

Applications of Fire Retardant Polymers: Electrical Applications 13. DIN EN 60695-11-5, Fire Hazard Testing – Part 11-5: Test Flames – NeedleFlame Test Method – Apparatus, Confirmatory Test Arrangement and Guidance, 2005. 14. R.B. Dawson and S.D. Landry in Proceedings of a SPE Conference - GPEC 2003: Plastics Impact on the Environment, Detroit, MI, USA, 2003, p.191. 15. C. Canaud, L.L.Y. Visconte and R.C.R. Nunes, Macromolecular Materials and Engineering, 2001, 286, 7, 377. 16. P. Porro, Materie Plastiche ed Elastomeri, 1998, 63, 11-12, 732. 17. F.W. Locher and S. Sprung, Beton, 1970, 2, 63. 18. F.W. Locher and S. Sprung, Beton, 1970, 3, 99. 19. C. Hammer and K. Fischer, Beton, 1971, 9, 20. 20. DIN EN 50267-2-1, Common Test Methods for Cables Under Fire Conditions – Tests on Gases Evolved During Combustion of Material from Cables – Part 2-1: Procedures – Determination of the Amount of Halogen Acid Gas, 1999. 21. DIN EN 50267-1, Common Test Methods for Cable Under Fire Conditions – Tests on Gases Evolved During Combustion of Materials from Cables – Part 1: Apparatus, 1999. 22. DIN EN 50267-2-2, Common Test Methods for Cables under Fire Conditions – Tests on Gases Evolved during Combustion of Material from Cables – Part 2-2: Procedures – Determination of Degree of Acidity of Gases for Materials by Measuring pH and Conductivity, 1999. 23. DIN EN 50267-2-3, Common Test Methods for Cables under Fire Conditions – Tests on Gases Evolved During Combustion of Material from Cables – Part 2-3: Procedures – Determination of Degree of Acidity of Gases for Cables by Determination of the Weighted Average of pH and Conductivity, 1999. 24. B. Gareiss, Plast’ 21, 1996, 53, 46. 25. Popular Plastics and Packaging, 2007, p.46. 26. P. Eigenmann, Materie Plastiche ed Elastomeri, 1995, 4, 194.

65

Characteristics and Analysis of Non-Flammable Polymers 27. ASTM E662, Standard Test Method for Specific Optical Density of Smoke Generated by Solid Materials, 2013. 28. ASTM D3675, Test Method for Surface Flammability of Flexible Cellular Materials Using a Radiant Heat Energy Source, 2012. 29. BS 6853, Code of Practice for Fire Precautions in the Design and Construction of Passenger Carrying Trains, 2002. 30. FAA AC 25.853-1, Flammability Requirements for Aircraft Seat Cushions, 1986. 31. BSS 7239, Boeing Procedure for Testing Toxic Gas Generation During Combustion of Polymers. 32. R. Petrus and B. Poisson, Plastiques et Elastomeres Magazine, 2002, 54, 3, 32. 33. European Plastics News, 1999, 26, 43. 34. C. Canaud and L.L.Y. Visconte and R.C.R. Nunes, Polimeros: Ciencia e Technologia, 2001, 11, 1, 35. 35. K-M. Reinfrank and R. Neuhaus, Kunststoffe Plast Europe, 2004, 94, 8, 91. 36. M. Le Gault, Canadian Plastics, 2003, 61, 6, 21. 37. G.W. Yeager, Y. Pan and J.E. Tracy, inventors; General Electric Co., assignee; EP 0921158B1, 2005. 38. G.W. Yeager, Y. Pan and J.E. Tracy, inventors; General Electric Co., assignee; EP 0921158A2, 1999. 39. Modern Plastics International, 1999, 7, 127. 40. T. De Soto, R. Dawson and S.D. Landry in Proceedings of the Rapra Technology Conference - Addcon World 2001, Berlin, Germany, 2001, Paper No.12. 41. Plastics Additives and Compounding, 2002, 4, 10. 42. Modern Plastics International, 1998, 28, 106. 43. G.C. Tesoro, Polymer Plastics Technology and Engineering, 1982, 18, 2, 123.

66

Applications of Fire Retardant Polymers: Electrical Applications 44. L. Castelani, inventor; Pirelli Cavi SpA, assignee; US 5910365A, 1999. 45. Design Engineering, 1999, August, p.28.

67

Characteristics and Analysis of Non-Flammable Polymers

68

5

Applications of Fire Retardant Polymers: Transportation Applications

5.1 Motor Vehicles The Federal Motor Vehicle Safety Standard (FMVSS) [1] serves as a worldwide basis for specification in outfitting automotives. This test provides for a limiting burning rate of ‘10 cm per minute’ and falls under the jurisdiction of the Federal Highway Administration of the US. It has been incorporated worldwide into industrial specifications, national standards, as well as international ISO standards [2]. The test sample measures 356 mm × 100 mm × d mm, (d is the sample thickness) and is supported horizontally. The free end is subjected to a specific flame exposure. Actual application-ready materials are to be tested [1]. These include composites, such as laminates prepared using adhesives, flame-lamination, and so on. The decisive test criterion is the burning rate. To ensure that the parts that might be individually exported satisfy the requirements of the American statutes, the automotive industry has, in part, adopted more stringent internal requirements such as limitation of burn distance. The vertically or horizontally arranged test samples are subjected to a wide specified flame for three minutes in the vertical configuration and two minutes in the horizontal configuration. The extent of surface destruction is used to determine the ratings ranging from ‘B1, leichtbrennbar’ (light burning) to ‘B4, nightbrennbar’ (no burning). The dripping characteristics as well as the visually determined smoke characteristics are divided into various classifications. Alpha Packaging Films [3] developed a flame retardant door liner for the automotive industry, which they claim, may meet safety standards and may have a host of other applications. Their product is a non-flammable polyethylene film, known as fireretardant grade, which avoids the potential hazard of giving off toxic fumes in the event of a fire.

5.2 Railway Vehicles The use of antimony-based flame retardant is avoided by using a halogenated

69

Characteristics and Analysis of Non-Flammable Polymers polyphosphate and this also provides a very low level of toxicity. Kicko-Walczak [4] has described a new polyester resin with reduced flammability and smoke evolution capacity for use in the transportation and building industries. Smoke evolution (in a National Bureau of Standards (NBS) chamber by the ASTM E662 method [5]) and ignitability (by the oxygen index method) were investigated for glass reinforced polyester (GRP) laminates obtained from unsaturated polyesters containing chlorine and bromine in the chain. In these studies, the effect on these properties of such additives as antimony trioxide (Sb2O3), aluminium hydroxide (Al(OH)3), tin hydroxide (SnO), magnesium hydroxide (Mg(OH)2) and melamine disphosphate in an amount of up to 30 mass% was determined. The most efficient ignition and smoke evolution retarder from among the investigated compounds was magnesium hydroxide (Mg(OH)2). An appreciable reduction in smoke evolution was also observed with hydrated tin dioxide (SnO2). GRP laminates with these additives meet the fire safety recommendations concerning smoke evolution devised by the polymer resin industry. Kicko-Walczak [4] adopted a method based on the measurement of ‘illuminence’ [6] for the evaluation of the smoking intensity of the polymers. This test is based on the measurement of the quantity of light incident upon a surface during the initial period of four minutes period of burning time. A special smoke chamber made of heat insulated material, 750 × 750 × 1000 mm (± 5 mm) in internal size, was used. The chamber was equipped with an ignition system, an illuminence measuring system, and a ventilation system. In Figure 5.1 is plotted illuminence (Elx) against time (t). Three polymers containing different smoke repressent additives were investigated. Zinc hydroxy stannate (SnZn(OH)6) and zinc stannate (ZnSnO3) were particularly effective as smoke repressents, especially when used in chlorinated and brominated resins. A synergism exists between these suppressants and the halogen incorporated into the resin chain. Such resins are suitable for rolling stock construction [7] and other applications such as floors, walls and ceilings. Woodward and Brown [8] have described fire retardant glass fibre resin reinforced composite based on acrylic acid and Al(OH)3, flame retardant and a wetting agent. Flammability and mechanical properties are discussed.

5.3 Marine Applications The requirements of the Seeberufsgenossenschaft apply to ocean liners operating under the German flag. While many aspects are regulated through the Intergovernmental Maritime Consulting Organisation, the setting of test and performance criteria for combustible materials is left to national agencies. For ships with German registration,

70

Applications of Fire Retardant Polymers: Transportation Applications a limited use of combustible products is permitted. These must, however, conform to the construction class B1 in accordance with DIN 4102-7 [9]. In addition, the judgement of relative toxicity must be favourable. Through animal experiments, the relative toxicity of the combustion products of the test material may be no worse than that of the combustion products of wood or cork. In order to minimise the potential for fire spread, these construction elements must additionally be covered by steel with a minimum thickness of 1 mm. Analogous safety requirements, for example those covering combustible insulation, are specified as part of the Merchant Shipping Notice M782 in the UK [10].

100

80

E1lx

60 7 40 3

20

0 0

48

96

104

192

240

t, s

Figure 5.1 Measurement of illuminence as a measure of smoking intensity of glass reinforced polyester laminate. Reproduced with permission from E. Kicko Walczak, Polymer Degradation and Stability, 1999, 64, 439. ©1999, Elsevier [4]

71

Characteristics and Analysis of Non-Flammable Polymers

5.4 Aircraft The aircraft industry uses, on a worldwide basis, the smoke density apparatus developed by the NBS. A vertically oriented test sample is subjected to a radiant heat flux of 2.5 W/cm2. The test is run both with and without a pilot ignition flame. The attenuation of the light beam of a vertically oriented measuring system is determined. A promising development is the ISO smoke box [11], developed by ISO TC92. One of the benefits of this method is the ability to also test composite materials. The smoke development is measured in the presence of a radiant energy flux in the range 0-5 W/cm2 with piloted ignition. The regulations of the US Federal Aviation Administration (FAA) are applicable worldwide to the aircraft transportation industry. The test requirements are specified by Federal Air Regulations – FAR 25.853 [12]. Test samples are oriented vertically, horizontally, or at a 45º angle and exposed to a specified Bunsen burner ignition source. Test criteria consist of burn distance, occurrence of dripping behaviour, and continued burning after removal of the ignition source. Internal industry specifications [13] also limit, among other factors, smoke density and toxicity of combustion products. The determination of toxicity is made from an analytical perspective. The concentrations and compositions of the combustion products are determined from gas samples obtained during smoke density measurements in a NBS chamber. Concentrations of sulfur dioxide, carbon monoxide, carbon dioxide, hydrogen cyanide, hydrogen chloride, and so on, are determined. The French aircraft seating manufacturer Groupe JSO has recently patented [14] a process that allows melamine resin to be incorporated in the seat cushioning offering a significant weight saving. According to BASF who manufacture the Basotect foam used in this application it has a density of less than 10 kg/m3, which means cushioning can be made at least 50% lighter than with standard foam. ISO has developed a composite cushion comprising Basotect and a standard foam, marketed under the Soly’t name. Cushioning made from this composite showed no signs of compression fatigue when subjected to 80,000 loaded cycles. The foam also passed demanding fire safety tests withstanding a direct flame of 1000 ºC for two minutes whilst retaining 90% of its original mass. The estimated weight savings of one kg per seat, which for an Airbus 380 would amount to a fuel saving, which in two months would recoup the cost of refitting an aircraft with these cushions. Various standard test procedures for fire retardancy in vehicles, rolling stock and aircraft are reviewed in Appendixes 3.7, 3.8, 3.9, 3.10 and 3.12.

72

Applications of Fire Retardant Polymers: Transportation Applications

References 1.

Federal Motor Vehicles Safety Standard (FMVSS) 302, Flammability of Materials used in the Occupant Compartments of Motor Vehicles, 1991.

2.

ISO 3795, Road Vehicles and Tractors and Machinery for Agriculture and Forestry – Determination of Burning Behaviour of Interior Materials, 1989.

3.

Converter, 2001, 38, 12, 20.

4.

E. Kicko-Walczak, Polymer Degradation and Stability, 1999, 64, 3, 439.

5.

ASTM E662, Test Method for Specific Optical Density of Smoke Generated by Solid Materials, 2012.

6.

G.A. Skinner, L.E. Parker and P.J. Marshall, Fire and Materials, 1976, 1, 4, 154.

7.

R.W. Adams, Plastics Engineering, 1988, 44, 3, 59.

8.

M.G. Woodward and N. Brown, Composites Plastiques Renforces Fibres de Verre Textile, 1997, 21, 82.

9.

DIN 4102-7, Fire Behaviour of Building Materials and Building Components – Part 7: Roofing Definitions, Requirements and Testing, 1998.

10. Merchant Shipping Notice M782 - Polyurethane Foam and other Organic Foam Materials, Department of Trade, Marine Division, London, UK, 1976. 11. ISO 5659-2, Plastics – Smoke Generation – Part 2: Determination of Optical Density by a Single-Chamber Test, 2012. 12. FAR 25.853, Airworthiness Standards: Transport Category Airplanes, Compartment Interiors, 2013. 13. H-J. Cantow, M. Kowalski and C. Krozer, Angewandte Chemie International Edition in English, 1972, 11, 334. 14. Plastic and Rubber Weekly, 2004, 19th March, p.4.

73

Characteristics and Analysis of Non-Flammable Polymers

74

6

Flammability Characteristics

6.1 Carbon Hydrogen Polymers

6.1.1 Polyolefins Various fire retardant additives have been incorporated into polyethylene (PE) and polypropylene (PP) to improve their flammability characteristics. These include graphite – halogen free flame retardant [1], graphite – magnesium hydroxide blends [2], magnesium hydroxide – red phosphorus blends [3], multi-walled carbon nanotubes [4], nanoclay-based concentrates [5], pentabromobenzyl acrylate [6], expandable graphite – ammonium polyphosphate [1], expandable graphite – zinc borate [1], and expandable graphite microcapsulated red phosphorus [1]. Xie and Qu [1] showed by limiting oxygen index (LOI) and cone calorimetry measurement that the heat release rate (HRR) and effective heat of combustion of polyolefins decreased and that the residue of carbonaceous char increased significantly with the addition of expanded graphite and/or other halogen-free expanded graphite additives. It was shown that the decrease in these values was due to the increase of oxidative degradation temperature and the decrease of oxidation heat. Additives which are particularly effective include PE and magnesium hydroxide – red phosphorus [3]. Chen and co-workers [2] carried out a study of the flammability characteristics and synergistic effects of different particle sizes of expanded graphite with modified magnesium hydroxide in flame retardant PP composites. They showed by LOI measurements that the particle size of the expanded graphite had a great effect on the flammability of PP – magnesium hydroxide – expanded graphite composites: their similar particle sizes increased the LOI value. Renaut and co-workers [7] discussed the fire retardancy of PP – polycarbonate (PC) blends. Fire retardant (FR) properties of the blends were shown to be gradually affected by the presence of polyolefins grafted with functional groups as compatabilisers.

75

Characteristics and Analysis of Non-Flammable Polymers

6.1.2 Polystyrene Fire retardants used in polystyrene (PS) include montmorillonite clay, polytetrafluoroethylene (PTFE) [8], bromine-based flame retardants such as brominated bisphenol A [9], brominated phenyl oxide or tetrabromophthalic anhydride, or magnesium hydroxide [10, 11]. Sanchez-Olivares and co-workers [12], in their study of the effect of montmorillonite clay on the burning rate of PS and PS–polyethylene terephthalate blends, showed that increased combustion rate accompanied the incorporation of montmorillonite particles in high-impact polystyrene (HIPS) formulations. Chang and co-workers [10, 11] studied the effect of a maleinated styreneethylenebutylene-styrene elastomer on the flammability of HIPS – PS encapsulated magnesium hydroxide composites. Cone calorimetry, LOI and UL 94 [13] horizontal burning tests were all used in this evaluation. Flammability and rheological properties were dependent on the microstructure. Combustion tests showed that compared to the composites containing untreated magnesium hydroxide, the fire retardancy of the composites containing PS encapsulated magnesium hydroxide was improved significantly. There was a critical PS magnesium hydroxide ratio of 6.0% for optimum flame retardancy.

6.1.3 Polyarylates Zhang and co-workers [14] studied the thermal decomposition behaviour and flammability of the polyarylates based on bisphenol A, 1,1-dichloro-2,2-bis(4-hydroxyphenyl) ethylene (BPC II) and 4,4´-dihydroxy-3-ethoxybenzylidenoacetophenone (Chalcon II), their copolymers and blends. Pyrolysis-gas chromatography-mass spectrometry (PyGC-MS), simultaneous thermogravimetric analysis (TGA) and pyrolysis-combustion flow calorimetry were used in this investigation. It was found that BPC II is an extremely fire resistant thermoplastic that can be used as an efficient flame retardant agent. Chalcon II is of interest as an ultraviolet (UV) visible sensitive polymer with a relatively low HRR and a high char yield. Pyrolysis–combustion flow calorimetry results show that the total heat of combustion of the copolymers or blends changes linearly with the composition but the change of maximum HRR and char yield depends on the chemical structure of the components.

76

Flammability Characteristics

6.2 Carbon – Oxygen Containing Polymers

6.2.1 Epoxy Resins Hshieh and Beeson [15] carried out flammability testing of flame retarded epoxy composites containing glass fibre aramid C (Kevlar 49) and graphite fibre reinforcement using the NASA upward flame propagation test, the controlled-atmosphere cone calorimeter test, and the liquid oxygen (LOX) mechanical impact test. The upward flame propagation test showed that phenolic/graphite had the highest flame resistance and epoxy/graphite had the lowest flame resistance. The controlled-atmosphere cone calorimeter was used to investigate the effect of oxygen concentration and fibre reinforcement on the burning behaviour of the composites. The LOX mechanical impact test showed that the epoxy/glass fibre had the lowest ignition resistance and the phenolic/aramid had the highest ignition resistance in LOX. Ding and Shi [16] carried out thermal degradation and flame retardancy studies on hexacrylated cyclophosphazene with UV reactive acrylic groups (HACP) or blends with non-reactive ethyl groups (HECP). These compounds were used as flame retardants for a commercial UV-curable epoxy acrylate EB600 (UCB Co.). The thermal behaviour and degradation mechanism were monitored by TGA, in situ Fourier-transform infrared spectrometry and calculation of apparent activation energy. The UV-cured blends exhibited better thermal stability at elevated temperatures with higher char yields than the pure EB600 sample. The flame retardancy of the blends was examined by LOI measurements. It was found that the HACP blends had higher LOI than the HECP blends. The use of organically modified clay as a filler in epoxy resin nanocomposites have been shown to have a low flammability rating in the UL 94 test [13]. High levels of clay improved the flame resistance appreciably [17]. Jeng and co-workers [18] carried out flame retardancy evaluations on epoxy polymers using phosphorus containing polyalkylene amines with or without aromatic groups as curatives. These phosphorus-containing epoxy resins were investigated using thermal analysis, flame retardance and degradation behaviour. The introduction of a soft -P-O- linkage, polyalkylene and hard aromatic groups into the backbone of the amines gave epoxy resins with tunable flexibility. The phosphorus-containing epoxy resins showed excellent flame retardant properties, and were useful in flame retardant epoxy coatings and other applications such as adhesives, and composite fabrications. The efficiency of phosphorus groups in improving flame retardancy of the resins is illustrated in Table 6.1 in which the LOI obtained is recorded against phosphorus

77

Characteristics and Analysis of Non-Flammable Polymers content for a range of polymers. The phosphorus-free epoxies were found to have LOI values in the 8–12 range whereas the LOI values of the phosphorus containing polymers were in the range of 21-32. High LOI values were obtained for the polymers containing 3.46% phosphorus (LOI of 27) and 4.07% phosphorus (LOI of 31). Other flame retardant epoxy resins systems are reviewed in Table 6.2.

Table 6.1 LOI values of the amine cured epoxy resins with various phosphorus contents Phosphorus content (%) LOI 2.58

23

1.94

23

1.29

22

0.65

21

2.06

22

1.55

22

1.03

21

0.52

21

3.46

27

2.60

25

1.73

24

0.87

21

2.77

28

2.08

26

1.39

25

0.69

24

2.32

23

4.07

31

2.50

28

0

18

0

18

0

19

0

21

Source: Author’s own files

78

Flammability Characteristics

Tables 6.2 Flame retardants for epoxy resins Comments on flame Epoxy compound Flame retardant retardancy Modified epoxy polyester systems

Phosphorus halogen and antimony oxide free

Epoxy/amine hydride resins

Nil

Mixed epoxy and phenolic resins

Nil

Phosphorus and silicon containing epoxy resins

Nil

Epoxy resin modified with bisphenol S (4,4´dihydroxydiphenyl sulfone

Introduction of Linear phenyl organophosphate groups phosphonate or a tribranched phosphate reduce flammability

Polymeric epoxy resins

Epoxy resins modified with organophosphate Epoxy resins modified with polysiloxane containing organophosphorus and epoxide groups Epoxy amine thermosets bisphenol A, 1,4´-bis-4-[(4hydroxy) phenyliminemethylidiene] phenoxybenzene Hybrids of epoxy and phenyltrisilanol polyhedral oligmomeric silsesquioxane Crosslinked cresolNovolac epoxy networks Source: Author’s own files

LOI measurements Good flame retardant properties Fire retardancy was classified as M3 and F1 for pure epoxy resin Flame retardant properties evaluated: high LOI values indicated that epoxy resins containing hetero atoms are effective flame retardants

Brominated flame retardants Organophosphate type, for example, bis(3dihydroxyphenyl) phenyl/phosphate

-

Reference [19] [20] [21]

[22]

[23]

[24]

UL 94 V0 [13] rating was achieved

[25]

Pendant cyclic phosphorus containing groups

LOI and cone calorimetry performed to evaluate flame retardancy

[26]

Phenoxy

Good flame retardancy

[14]

Flame retardant reduced smoke generation and CO and CO2 production

[26]

Lower flame retardancy for crosslinked resin compound to uncrosslinked resin

[28]

Aluminium triacetyl acetonate as a latent catalyst

-

79

Characteristics and Analysis of Non-Flammable Polymers

6.2.2 Polyesters Stackman [29] carried out a study to find systems suitable for reducing the flammability of polyethylene terephthalate (PET) and poly-1,4-butylene terephthalate (PBT) while retaining the chemical and physical properties of the original polymers. The additives used were phosphine oxides, phosphonates and phosphates and their activity was assessed by means of an oxygen index test. Most of the phosphorus esters were found to be volatile under the blending conditions and both the halogenated phosphorus esters and halogenated derivatives of phosphorus oxide proved to be ineffective as flame retardants. Sato and co-workers [30] studied the thermal degradation of flame retarded PBT. The flame retarded PBT contained brominated polycarbonate plus antimony trioxide as a synergistic agent. These polymers were studied by means of various temperatureprogrammed analytical techniques such as temperature-programmed Py-MS, temperature-programmed pyrolysis-atomic emission detention and temperatureprogrammed Py-GC. During the degradation of the flame-retarded PBT, brominated phenols were first observed to evolve at temperatures slightly lower than those for the flammable product evolution from the substrate polymer PBT, followed by the evolution of hydrogen bromide over the whole range of degradation temperatures for the substrate polymer. These degradation processes were closely related to the synergistic effects of antimony trioxide on the decomposition of brominated polycarbonate in the flame-retardant system to promote the thermal degradation of brominated polycarbonate at lower temperatures than those for pure brominated polycarbonate. Furthermore, the evolution of the flame poisoning antimony tribromide formed through the reaction between brominated polycarbonate and antimony trioxide could also be monitored directly by temperature-programmed pyrolysis techniques. On the basis of the data obtained by these temperature-programmed pyrolysis techniques it was possible to obtain information on the thermal degradation of flame retarded PBT and on the synergistic flame-retarding mechanisms. Price and co-workers [31] used their laser pyrolysis/time-of-flight mass spectrometry technique to model the behaviour in the so-called dark flame region behind the flame front in a polymer fire and to investigate flame retarded polymethylmethacrylate (PMMA). The laser pyrolysis of the aluminium oxide trihydrate (ATH) retarded PMMA produces a large amount of water and carbon dioxide as volatiles. Also, the amount of the monomer evolved is reduced significantly compared to that obtained from pure PMMA. The implications of these results is that in a real fire situation ATH influences PMMA pyrolysis in such a manner as to bring about a reduction in the evolved ‘fuel’ whilst at the same time adding non-combustible gases to the flame region. These processes render the PMMA flame retardant.

80

Flammability Characteristics Hernangil and co-workers [32] studied the fire behaviour of halogenated polyester resins containing zinc compounds as fire retardants and smoke suppressants. They pointed out that it is important to take into account two different aspects of the problem: (a) reaction to fire, in which material flammability (exclusively in the gas phase) and combustability (in the gas and solid phases) are issues, and (b) smoke emission from the material subjected to overheating, in which smoke density and toxicity are major concerns. Improvements in fire properties can be achieved using fire retardants and smoke suppressants. Fire retardants can act by interfering in the radical chain reactions that take place in combustion processes, or physically, by forming a protective layer, either by giving off non-flammable gases to dilute flammable ones and exclude oxygen from the fire area in the gas phase, or by promoting endothermic reactions or surface dehydration. Smoke suppressants such as zinc compounds can also act both physically and chemically, by formation of halides and oxyhalides in redox reactions in the condensed and gas phase. Baudry and co-workers [33] observed that the fire behaviour, as ascertained by LOI measurements, of unsaturated polymers improved when samples with a cyclopentadiene end-cap were cured. LOI was determined on 10 × 150 mm specimens of 3 mm thickness using the NF EN ISO 4589-1 [34], NF EN ISO 4589-2 [35] and NF EN ISO 4589-3 [36] procedures. Analyses were conducted at ambient temperature, with a 40 ml/s gas flow in the quartz column. The oxygen ratio variation in the gas was 0.2%. Results were obtained on three samples tested in the same conditions. LOI were determined for samples crosslinked at ambient temperature, without post cure, and for samples after post cure. In Table 6.3 are shown the LOI values for the three materials studied. Even though the results depend on the time between processing and testing, the interest of this analysis is that during work on composites of large dimensions, as in the naval industry, for example, structures are not post-cured. During the course of post cure, the amount of volatile emission is between 0.2 wt% and 0.4 wt% of the sample. When unsaturated polyesters are post-cured, the oxygen indexes of the three materials are greater than 18, which means that the materials do not burn in air. When samples are not post-cured, the larger quantity of volatile products makes LOI values lower. In the case of sample A, the value is less than 18. The LOI value increases when the styrene content decreases. This shows the need to limit the amount of styrene in the structure of polyester systems to improve their fire behaviour. With a LOI index of 21-22 these materials with dicyclopentadiene chain ends do not burn in air. Furthermore, the fact that these materials are not used in the form of the pure matrix, but in the form of composites with glass fibres, would

81

Characteristics and Analysis of Non-Flammable Polymers again improve their fire characteristics. Further work on fire retardancy in polyesters is reviewed in Table 6.4.

Table 6.3 LOI Index determined on samples crosslinked at ambient temperature and on post-cured samples Styrene weight in network (%) Sample

A

LOI

Before post-cure

After postcure

Sample without post-cure

Post-cured sample

40.2

40.0

17.9 ± 0.2

18.2 ± 0.2

B

34.9

34.6

18.6 ± 0.2

19.1 ± 0.2

C

33.5

33.1

21.2 ± 0.2

22.1 ± 0.2

Source: Author’s own files

6.2.3 Polycarbonates Antimony trioxide-brominated PC [30], silicones [46, 47] and hydroxyapatite [48] have all been studied as flame-retardants for PC. Figure 6.1 shows the perceived flame retardancy mechanism occurring during the thermal decomposition of PC containing trifunctional phenyl silicone based additives [47]. This process involves the formation of a p-cumylphenoxy end-structure. A compound was produced during pyrolysis. Here, an electrophilic silyl radical produced from the trifunctional siloxane units through the elimination of a phenyl group attacks the ether-like oxygen atom of a carbonate linkage in the PC chain to form a crosslinking structure containing a tetrafunctional siloxane unit, leaving a carbonyl radical which gave the p-cumylphenoxy end structure through decarboxylation and hydrogen abstraction. Figure 6.1 shows a possible formation process of the carboxyl branching structure of thermally treated flame retardant polycarbonate system (FR-PC). In this case, the silyl radical also attacks the ether like oxygen atom in a similar manner as shown in Figure 6.2 through simultaneous Fries rearrangement rather than decarboxylation. The resulting carboxyl branching structure in the PC chain is accompanied by the phenyl silyl ether linkage, which might construct stronger crosslinking structures.

82

Flammability Characteristics

Polyester Unsaturated polyester PET-co-polyethylene9,10-dihydro-10[2,3-di(hydroxyl carbonyl)propyl]-10phosphaphenanthrene10-oxide

Flame retardant unsaturated polyesters containing chlorine or bromine

Polyester resins

Table 6.4 Fire retardant polyesters Flame retardant Comments on flame agents retardancy

Reference

Antimony oxide

Synergistic flame retardant

[37]

Phosphorus containing flame retardant

Index and LOI reported

[38]

Inherent fire retardancy measured

[39]

Methods of determining flammability discussed

[40]

Chlorendic acid or dibromoneopentyl glycol (60–70%) with addition of antimony trioxide (Sb2O3), ZnSnO3, or triethyl phosphate as flame retarders, increases the LOI by up to 40% Inorganic and organic flame retardants, halogen free

PMMA expandable graphite composites

Silane grafted on polymer

Unsaturated polyesters

Aluminium trihydrate

Phosphorus containing unsaturated polyesters

Expandable graphite ammonium polyphosphate, triphenyl phosphate

Polyester

Aluminium trihydrate

LOI and TGA used to calculate flame retardance and thermal stability Cone calorimetry to measure ignition time, heat release, smoke emission and toxicity, even small additions of aluminium trihydrate improved fire performance Flammability and thermal properties investigated, by UL 94 [13] and LOI. Polymers containing ethylene glycol and ammonium polyphosphate showed the best flame retardance Improvement of the fire reaction of polyesters particularly heat release and smoke generation

[41]

[42, 43]

[44]

[45]

Source: Author's own files

83

Characteristics and Analysis of Non-Flammable Polymers CH3 O

O

+

O

Si

O

C

C

O

O

O

CH3

O

CH3

O Si

C

O

O

O

CH3

O

+

C

Thermal reaction

scission at Si–C H abstraction

O

C

CH3 +

C

C

O

O

O

CH3

C. O

decarboxylation H abstraction CH3 O

C

C

O

O

CH3

p-cumylphenoxy end structure

CH3 H3CO

C CH3

Reactive pyrolysis to form X

TMAH

Compound X

Figure 6.1 Formation pathway of the p-cumylphenoxy end structure and its characteristic product (compound X) for the thermally treated FR-PC. TMAH = tetramethylammonium hydroxide. Reproduced with permission from K. Hayashida, H. Ohtani, S. Tsuge and K. Nakanishi, Polymer Bulletin, 2002, 48, 483. ©2002, Springer [47]

84

Flammability Characteristics

CH3 O

Si

O

+

O

O

C

C

O

O

C O

CH3

O

( CH3

+

CH3

.

O)3Si

C

O H

C

O

C

O

C O

CH3

Thermal reaction

scission at Si–C Fries rearrangement

O H abstraction

CH3

CH3 ( O)3Si CH3

+

C

C

O O

CH3

C

O

C O

O CH3 carboxylic branching structure TMAH

C

H3CO H3CO

C

CH3 O Compound Y

OCH3

Reactive pyrolysis to form Y

CH3

Figure 6.2 Formation pathway of the carboxylic branching structure and its characteristic product (compound Y) for the thermally treated FR-PC. Reproduced with permission from K. Hayashida, H. Ohtani, S. Tsuge and K. Nakanishi, Polymer Bulletin, 2002, 48, 483. ©2002, Springer [47]

85

Characteristics and Analysis of Non-Flammable Polymers Hayashida and co-workers [47] demonstrated that silicone derivatives containing phenylsiloxane units were effective flame-retardants for PC materials through not only its excellent dispersing ability in the PC substrate but also its ability to form a flame-retardant char barrier consisting of the branched silicone and condensed aromatic compounds during combustion. Thus, results from this work suggest that the formation of the crosslinking structures between FR-PC substrates and the phenyl silicone-based additives might also play an important role for the flame retardancy of the FR-PC system. At an early stage of the combustion, silyl radicals formed through the releasing phenyl groups develop the crosslinking structures, which should promote the formation of the char barrier on the surface of the PC material to reduce the radiant heat of flame and to restrict the diffusion of flammable products into the combustion zone. Thus, the crosslinked structure formed might also suppress the thermal decomposition of the whole material body and confine the movements of the degradation products in the material. These effects would develop synergistically the flame retardancy of the phenylsilicone-containing PC material.

6.2.4 Phenolic Resins Various workers have discussed flame retardancy in phenolic resins [49-52]. Alkyl ammonium treated montmorillonite [52], silica [50], and polysiloxane [51], have all been studied as flame-retardants for phenolic resins. Chiang and co-workers [50] studied the flame retardance of phenolic resin-silica nanocomposites. The char yields of the polymer were observed to increase when the tetraethoxysilane content of the polymer was increased. LOI and UL-94 [13] tests revealed that the hybrid possessed excellent flame resistance. Lin and co-workers [51] observed that curing phenolic resins with epoxies instead of with hexamethylene tetramine yields polymers which have almost the same flame retardance as polymers produced with hexamethylene tetramine curing. They also have toughness, stiffness, good thermal stability, excellent flame retardance and low glass transition temperature (Tg).

6.2.5 Polyketones Porro [53] has compared the flammability characteristics of non-reinforced, glass fibre reinforced and mineral reinforced and mineral filled grades of polyketones.

86

Flammability Characteristics

6.3 Chlorinated Polymers

6.3.1 Chlorinated Polyethylene Chlorinated polyethylene (CPE) is a PE that has random chlorine substitution. It has toughness and barrier properties, as well as ignition resistance. Depending on the degree of chlorination, CPE polymers can have elastomer or thermoplastic forms which have extraordinary compatibility with a range of other materials. This makes CPE readily adaptable to common compounding and curing techniques. CPE polymers can produce end products that are hard and tough or soft and flexible. Most commercial CPE products contain 25–50 wt% chlorine. CPE is an ignition-resistant PE. It is also used in blends to change the ignition characteristics of other polymers. CPE has no unsaturation in the polymer backbone, giving it excellent ozone and weathering properties. The saturated backbone also results in a temperature stability that allows CPE to perform well continuously at temperatures of 150 ºC. CPE can provide satisfactory resistance to most acids, bases, oils and alcohols.

6.3.2 Chlorosulfonated Polyethylene Donskoi and co-workers [54] showed that each of the components of a chlorosulfonated polyethylene (CSPE) mix has its own influence on the fireproofing properties and chemical processes that occur. In this case, the thermal properties of the vulcanisates of CSPE were studied, and also the heat flows from the flame on the surface of the specimen. It was established that the thermooxidative breakdown of CSPE and vulcanisates based on it during heating under dynamic conditions, is a multi-stage process. The results of tests involving various fillers and plasticisers made it possible to create rubber-like, high-impact resistant materials.

6.3.3 Polyvinylchloride Various workers have discussed the fire retardancy of polyvinylchloride (PVC) [55-59] using ammonium treated clay montmorillonite nanocomposites [52], hydroxyapatite nanocomposites [56] and antimony trioxide [57]. Lum [60] examined the effect of flame retardant additives on polymer pyrolysis reactions with a PVC composition containing 3 phr of Sb2O3. It is well known that a synergistic flame retardancy effect is observed when Sb2O3 is incorporated into organic halide materials such as PVC.

87

Characteristics and Analysis of Non-Flammable Polymers The presence of antimony trichloride in the products of laser vaporisation of PVC provide direct evidence for the production of volatile antimony trichloride.

6.4 Nitrogen Containing Polymers

6.4.1 Polyurethane Several workers have discussed flame retardancy in polyurethane (PU) insulating materials and foams [31, 57-59, 61-64]. Price and workers [31] studied the flame retardancy of rigid PU foams with various isocyanate indexes using the laser pyrolysis-mass spectrometry technique. The flame retardance of these materials is shown to increase with increasing isocyanate index and weight fraction of isocyanate. Laser pyrolysis experiments with these samples showed that the major volatiles are dominated by monomer and oligomers of the polypropylene glycol used to produce the foam, plus lower molecular weight species of which carbon dioxide appear to be a significant part. An increase in isocyanate index results in a reduction in the extent of monomer/oligomer evolution and an increase in the low molecular weight species. The flame retardant mechanism using phosphorus, introduced as low percentages of dimethyl methylphosphonate, is attributed to a reduction in fuel evolution via pyrolysis of rigid PU foams. Kou and co-workers [64] have reported on the use of non-halogenated phosphorus type flame retardants in the formulation of alkylphosphate-type polyols and their corresponding PU. The organic or inorganic phosphorus compounds for flame retardants are used either by blending with polymers or by reacting them into the polymers. Phosphorus compounds exhibit their function in the gaseous state and/or as solid-state fire protection [65, 66]. For the former, it can quench flammable particles such as H· and HO· [67]. For the latter, it can form polyphosphoric acid-like glass upon heating to protect the burning surface, [68-70], or it can form an inflammable char by reacting with organic components. Polyols are important intermediates for PU, which are used for PU foam [71, 72] and artificial leathers, where inflammability is required for many applications. The flame retardant properties of several phosphorus containing polyols was evaluated

88

Flammability Characteristics by LOI measurement which is calculated from the phosphorus content and the temperature accompanying 50% weight loss, i.e., degradation. Kuo and co-workers [64] showed that the LOI [73, 74] is a good parameter to predict the flame-retarding ability of a material. It is defined as the oxygen ratio in a mixture of N2/O2, under which the sample can just keep burning (LOI)m after it is ignited. For the polyphosphate, the (LOI)m value was calculated using the relationship previously established by Annakutty and Kishore [75]:

(LOI)m = 3.0 (TS)⅓ (PC)½

Where (LOI)m is defined as the minimum percentage of oxygen required in a nitrogenoxygen atmosphere surrounding the sample to maintain its combustion for at least 30 seconds after ignition. PC is the phosphorus content and TS is the percentage stability defined as ‘100 – percentage of instability’, i.e., T0.5/10 (T0.5 is the temperature at 50% weight loss). By using the experimental data, the (LOI)m value was calculated as 46.3 for the ethylene glycol - butyl phosphorodichloridate (PBE) reaction product, and 33.8 for the 1,4-butanediol - butyl phosphorodichloridate (PBB) reaction product. Material that has a LOI value higher than 26 can be regarded as having flame-retarding ability. Comparing this LOI value, it shows that the PBE and PBB have very high LOI values and can be regarded as effective flame-retarding materials. From its (LOI)m value, PBE has a better flame-retarding ability than PBB. This result coincides with that obtained from char residue data at 800 ºC, as mentioned previously. Similarly, the LOI value for the PBE-toluene diisocyanate reaction product (PETD) and PBB-toluene diisocyanate reaction products (PBTD) were calculated for the previously mentioned method to be 34.6 for PETD and 16.3 for PBTD. Again PETD has the higher (LOI)m than PBTD. Compared with PBE and PBB, the corresponding polyurethanes, PETD and PBTD have lower (LOI)m values. Even though PETD and PBTD have lower phosphorus contents, they result in rather high (LOI)m values and the accompanying good flame-retarding ability. Other types of flame retardants that have been incorporated into PU are reviewed in Table 6.5.

89

Characteristics and Analysis of Non-Flammable Polymers

Polyurethane

Table 6.5 Fire retardant polyurethanes Comments on flame Flame retardant retardancy

4,4´-Diphenyl methane diisocynate, 1,6-hexamethylene diisocyanate and polyoxypropylenediol

3-Chloro-1,2 propanediol or 1,2-propanediol

Rigid polyurethane foams

-

Polyisocyanurate - PU foam

Expandable graphite

PU

Various

PU foam

-

-

Reference

[57]

Temperature stability up to 250 ºC, fire behaviour studied

[58]

Fire behaviour of this foam considerably improved by use of expanded graphite

[59]

-

[61]

Response to fire measured

[62]

Rigid PU foam

Dimethylmethyl phosphonate

Laser pyrolysis – mass spectrometry studies

Alkyl phosphate PU

Organophosphorus

LOI values reported

[63-65] [66]

Source: Author’s own files

6.4.2 Polyamides Various types of flame retardant additives have been used in polyamides including magnesium hydroxide – red phosphorus in glass fibre reinforced polyamide [76], chemically modified montmorillonite organoclays [77], surface modified nanosilica [77], carbon nanofibres in polyamides 11 and 12 [78], and dodecyl sulfate anionmodified MgAl (H-DS) interlayers in polyamide 6 [79]. Koo and co-workers [78] attempted to develop polyamides 11 and 12 with enhanced flame retardancy and thermal and mechanical properties by the incorporation of montmorillonite clays, silica and carbon fibre-polymer nanocomposites. Flammability properties of the nanocomposites were compared with those of the virgin polyamides, using cone calorimetry with an external heat flux of 50 kW/m2. Cone calorimetry was also used in an evaluation of polyamide 6 – anion modified Mg/Al interlayer formulation [79]. The data from the cone calorimeter shows that the heat production rate (HPR) and mass loss weight of the sample with 5 wt% MgAl(H-DS) decrease considerably to 664 kW/m2/s and 0.161 g/m2/s from 1064 kW/m2/s and 0.252 g/m2/s

90

Flammability Characteristics of pure polyamide 6, respectively. This kind of exfoliated nanocomposite is promising for the application of flame-retardant polymeric materials.

6.4.3 Polyimidoamide Nanocomposites Janowska and co-workers [63] studied the flammability characteristics of polyimidoamide-organically modified clay nanocomposites. The fibres produced were multi-functional and showed an increase in porosity and sorption properties. They also had a high thermal stability and reduced flammability when compared to fibres without montmorillonite.

6.5 Phosphorus and Silicon Containing Flame Retardants Isobutyl bis(glycidylpropylether) phosphine oxide [77], oligomeric polyalkyl phosphate polyols [64], triacryloyloxyethyl phosphate (TAEP), diacryloyloxyethyl ethyl phosphate (DAEEP) [80] and phosphate methacrylate [80-82] have all been used to improve the flame retardancy of alkyl phosphate type polymers. Isobutyl bis(glycidylpropylether) phosphine oxide has been used as a crosslinking agent for phenolic novolac resin [77] in the production of phosphorus containing novolacepoxy systems. It was shown that samples containing more than 2% phosphorus content produced a V0 material, the industry standard for flame retardancy, but phosphorus-free polymers and those containing less than 2% phosphorus were consumed in the first ignition. Polyalkylene phosphate polyols based PU have flame retarding properties [66]. The combustion of a polymer is generally described in three stages: fuel production, ignition and then burning. When a polymeric material is heated with rising temperature, eventually the polymer starts to degrade. During the degradation, small molecules are produced in which the combustible compounds are evaporated and mixed with air, forming a flammable mixture. When the concentration of the mixture and also the temperature reach the flammability limits, the polymer starts to burn. The exothermic heat from the burning process feeds back to the condensed phase, causing further degradation of the polymer [83]. Therefore, the combustion behaviour of a flammable material is strongly affected by the degradation of its components. Phosphorus-containing compounds are a family of condensed-phased FR, which are able to increase the conversion of organic matter to char during burning, and, thus

91

Characteristics and Analysis of Non-Flammable Polymers decrease the amount of flammable volatile gases reaching the flame zone, and reduce the heat transfer from the flame to the polymer. Therefore, a knowledge of the relationship between the mode of action of phosphorus polymers during degradation and the nature of the flame retardant is very important to an understanding of the basis of flame retardancy [84]. Liang and Shi [80] have shown that TAEP and DAEEP can be used as FR multifunctional monomers for UV curable systems. The UV cured TAEP and DAEEP films have LOI of 36 and 29, respectively. Their thermal behaviour was studied by TGA and they show three characteristic degradation temperature regions, attributed to the decomposition of phosphate, thermal pyrolysis of the acrylate side chains, and decomposition of unstable structures in the char. It is proposed that the degraded products of phosphate form polyphosphoric acid, which further catalyses the breakage of carbonyl groups to form an intumenscent char, preventing the samples from further burning. Liang and Shi [80] showed that from 160 ºC to 270 ºC the degradation is mainly attributed to the fast degradation of phosphate groups. From 270 ºC to 350 ºC, polyphosphoric acid is formed, which catalyses the breakage of carbonyl groups to form polynuclear aromatic structures. When raising the temperature over 500 ºC, some unstable structures in the char are decomposed, resulting in the formation of phosphorus oxides and some volatile aromatic molecules. The main difference in the degradation of DAEEP and TAEP films is that DAEEP film released C2H4 and (HO)3POC2H5 during the first step with a great reduction in the flame-retardant properties of DAEEP film. DAEEP film has a lower LOI of 29 compared with that of 36 for TAEP film. The proposed decomposition mechanism is depicted in Figure 6.3.

92

Flammability Characteristics

O P

O C2H4+C2H5OP(O)(OH)2+C2H5OP(OH)3+(C2H5O)2P(OH)2+

OC2H5

O P

O OCH2CH2OCCH=CH2

O CH

COCH2CH2

O

O

CH2=CHOCCH=CH2+

P

O

O

OP

CH2=CHOC

CH2

P

OH

OH

CH + Phosphoric acid CH

Major O CH2

CH

CHOC

Poly(phosphoric acid) + H2O

CH2

Method 1

+ HCO + CO2 O CH2

CHOC

CH + Phosphoric acid + Poly(phosphoric acid) + H2O CH

Minor

Method 2 O O

O

OC

OH + (C2H3)OP(OH)3 + C2H2

Char

Figure 6.3 Decomposition mechanism of TAEP. Reproduced with permission from H. Liang and W. Shi, Polymer Degradation and Stability, 2004, 85, 525. ©2004, Elsevier [80]

93

Characteristics and Analysis of Non-Flammable Polymers

100

Mass (%)

80

TAEP DAEEP

1.5

60 40

0.0

20

–1.5

DTG (%/ºC)

3.0

0 –3.0 200

400

600

800

Temperature (ºC)

Figure 6.4 Weight loss/temperature curves of DAEEP and TAEP. Reproduced with permission from H. Liang and W. Shi, Polymer Degradation and Stability, 2004, 85, 525. ©2004, Elsevier [80]

Figure 6.4 shows the phosphorus contents and the weight loss of phosphorus in DAEEP and TAEP films after treatment at 180, 300, 400, 500, and 600 ºC. Raising the temperature from 180 ºC to 300 ºC, the phosphorus contents of both polymers increase quickly and the DAEEP film has a 20% weight loss of phosphorus, while the TAEP film has only 3% loss. In this temperature range, a large amount of carbon releases as CHO and CO2, whereas polyphosphoric acid is hard to volatilise, resulting in the increase of phosphorus content. However, a small amount of (HO)3POC2H5 might be released from DAEEP film in this temperature range, resulting in a 20% weight loss of phosphorus. When raising the temperature over 300 ºC the trend of the phosphorus contents and the weight loss of phosphorus in the two films are very similar. From 300 ºC to 400 ºC, polyphosphoric acid catalyses the breakage of the remaining carbonyl groups to release CO2 and H2O, resulting in the increase of phosphorus content. When raising the temperature over 400 ºC, the phosphorus content decreases because some phosphorus oxides volatilise.

94

Flammability Characteristics Sponton and co-workers [22] prepared a range of phosphorus and silicon containing epoxy resins from (2,5-dihydroxphenyl)diphenyl phosphine oxide (Gly-HPO), diglycidyloxy methylphenyl silane (DGMPS) and 1,4-bis(glycidyloxydimethyl silyl)benzene (BGDMSB) as epoxy monomers and diaminodiphenylmethane (DDM), bis(3-aminophenyl)methyl phosphine oxide (BAMPO) and bis(4-aminophenoxy) dimethyl silane (APDS) as curing agents. Their thermal dynamic mechanical and flame retardant properties were evaluated. The high LOI values confirmed that epoxy resins containing hetero-atoms are effective flame retardants. The LOI values of the phosphorus-silicon-containing epoxy resins are shown in Table 6.6. Materials with outstanding LOI values are obtained with the corresponding excellent flame retardant properties [81, 82, 85, 86]. It was shown that the presence of phosphorus in phosphorus-containing epoxy resins increases the LOI values even when the phosphorus content is low, and no significant differences with the phosphorus content are observed. For the silicon-containing epoxy resins, the LOI values increase with increasing silicon content up to a content of 10%. However, a synergistic effect cannot be observed for phosphorus-silicon-containing epoxy resins and significant improvements in LOI values are not obtained.

6.5 Silicon Containing Flame Retardants Connell and co-workers [87] investigated silicate siloxane fire retardant composites derived from vermiculite by reaction with hydroxyl-terminated polydimethylsiloxanes. Cone calorimetry was used to obtain HRR measurements. The results show that even at the highest irradiance levels the samples have very long ignition times. Ignition resistance deceases as the hydrocarbon content of the composite increases. The results from the cone calorimeter were obtained by Py-GC-MS, which show that small, volatile, silicone-containing molecules are formed during pyrolysis. Harada and co-workers [88] investigated the flame retardancy of polyglycidyloxypropyl silsesquioxane layered titanate nanocomposites. The UL 94 test method [13] was used to investigate the burning properties of the nanocomposites. It was found that the spherical titanate-filled nanocomposite sample burned from one end to the other, whereas a fire extinguishing property was observed in the sheet-like titanate-filled nanocomposites. The latter nanocomposites were classified as UL 94 V0, even with a 5 wt% layered titanate content.

95

Characteristics and Analysis of Non-Flammable Polymers

Table 6.6 Curing and post-curing conditions and Tg data of the epoxy resins Sample

Epoxy Curing monomer a agent b

Curing agent b

1 2 3 4 5 6 7 8 9

Gly-HPO DDM 120 ºC, 2 h Gly-HPO BAMPO 140 ºC, 2 h Gly-HPO APDS 120 ºC, 2 h DGMPS DDM 105 ºC, 2 h DGMPS BAMPO 150 ºC, 1 h DGMPS APDS 120 ºC, 3 h BGDMSB DDM 120 ºC, 2 h BGDMSB BAMPO 145 ºC, 2 h BGDMSB APDS 120 ºC, 3 h Gly-HPO/ DDM 120 ºC, 2 h 10 DGMPS Gly-HPO/ BAMPO 145 ºC, 3 h 11 DGMPS Gly-HPO/ APDS 120 ºC, 3 h 12 DGMPS Gly-HPO/ 120 ºC, 2 h DDM 13 BGDMSB Gly-HPO/ BAMPO 145 ºC, 3 h 14 BGDMSB Gly-HPO/ 15 APDS 120 ºC, 3 h BGDMSB DDM = Diamino diphenyl methane

Tg (°C) Post-curing

½ ∆Cpc

E″maxd

Tan∆ maxe

200 ºC, 3 h 200 ºC, 2 h 180 ºC, 2 h 165 ºC, 2 h 180 ºC, 1 h 160 ºC, 3 h 180 ºC, 2 h 195 ºC, 2 h 180 ºC, 2 h

193 198 167 77 75 70 60 80 59

181 154 158 72 76 63 62 90 53

193 194 167 87 84 70 64 105 68

180 ºC, 2 h

125

123

139

195 ºC, 2 h

146

136

148

160 ºC, 3 h

120

100

118

180 ºC, 2 h

123

119

138

195 ºC, 3 h

145

130

148

160 ºC, 3 h

100

84

99

a

For the mixtures of epoxy monomers, 1:1 mol ratio was used.

b

Stoichiometric amounts were used in all cases.

c

From differential scanning calorimetry method measurements (10 ºC/min).

d

Maximum of the loss modulus from dynamic mechanical thermal analysis measurements.

e

α relaxation peak of the loss factor.

Reproduced with permission from M. Sponton, L.A. Mercado, J.C. Ronda, M. Galia and V. Cadiz, Polymer Degradation and Stability, 2008, 93, 2025. ©2008, Elsevier [22]

6.6 Review - Fire Retardancy of Polymers It is seen from Table 6.7 that, without exception, in a wide range of commercially available fire retardant polymers the incorporation of fire retardant additives into the formulation produces distinct improvements in LOI values and flammability and flame spread characteristics of the polymers listed.

96

Flammability Characteristics

Table 6.7 Comparison of fire retardant characteristics of non-fire retardant, (i.e., no fire retardant additives incorporated) and fire retardant versions, (i.e., fire retardant additives incorporated in polymer formulation) Non-fire retardant version of Fire retardant versions of polymer, (i.e., no fire retardant polymer, (i.e., with added fire additives in polymer formulations) retardant chemicals) Oxygen Polymer Oxygen index index Flame Flame rating* (%) Flammability rating Flammability spread spread (UL 94) [13] (%) (UL 94) PP

17 (Very poor)

HIPS

18 (Very poor)

HB (Poor)

Very poor Very poor Good

Alkyds

50 (Good)

HB (Very poor) V0 (Good)

Polyester

23 (Poor)

V1/V2 (Good)

Good

PBT

25 (Poor)

V1/V2 (Poor)

Poor

PET

20 (Poor)

HB (Poor)

Epoxy resins Polyphenylene oxide

28 (Poor)

V0 (Poor)

Very good Poor

20 (Poor)

HB (Poor)

PC

25 (Poor)

Polyamide-6,6

Good

Good

Good

Good

Good

Good

Good Very good

Good

Good

Good

Good

Good

-

-

Good Very good Very good Very good -

Poor

Good

Good

Good

V1/V2 (Poor)

Good

35% (Very good)

Very good

Very good

23 (Poor)

HB (Poor)

Poor

Good

Good

Very good

18 (Very poor)

V1 (Very poor)

Poor

Good

Good

Good

19

HB (Poor)

Poor

30% (Good)

Good

Very good

PU

19 (Poor)

HB (Poor)

Poor

-

-

-

Diallylphthalate

25 (Good)

V1/V2 (Poor)

Poor

Good

Very good

Very good

Styreneacrylonitrile Acrylonitrilebutadiene-styrene

Very good

*Oxygen index rating 28% - V0 Source: Author’s own files

97

Characteristics and Analysis of Non-Flammable Polymers Generally LOI values improve from a poor UL 94 rating of horizontal burning (HB) to a good or very good UL 94 rating of V1 or V2 and flame spread characteristics improve from poor/very poor to good/very good. However, with none of the types of polymers listed in Table 6.7, which without the addition of fire retardant additives, are not fire retardant, do we reach the fire retardant values quoted in Table 6.8 for intrinsically fire retardant polymers, i.e., those which do not require the presence of fire retardant additives in their formulation to impart fire retardancy. These are graded in Table 6.8 according to their LOI value in the range 31% (ethylene tetrafluroethylene copolymer) to 95% for polymers such as fluorinated ethylene propylene and PTFE. Only in the latter category are excellent flame spread characteristics achieved.

Table 6.8 Intrinsically flame retardant polymers in order of increasing oxygen index Oxygen index Flammability Polymer Flame spread (%) (UL 94) [13] Oxygen index range up to 39% Ethylenetetrafluoroethylene Polyvinyl fluoride Polyvinylidene fluoride Polyether ketone Polyether sulfone

35 (Very good) 35 (Very poor) 35 (Very good) 25 (Very good) 36 (Very good)

V0 V0 V0 V0 V1

Very good Exceptional Exceptional Very good Very good

V0 V1 V0 V0 V0

Very good Very good Very good Very good Very good

V0 V0

Very good Very good

V0

Very good

V0 V0 V0

Excellent Excellent Excellent

Oxygen under range 40-49% Silcones Polyamideimide UPVC Polyphenylene sulfide Polyetherimide

40 (Very good) 43 (Very good) 45 (Excellent) 46 (Excellent) 47 (Very good)

Oxygen index range 50-59% Chlorinated PVC Polyimide

50 (Very good) 53 (Very good)

Oxygen index range 60-69% Ethylenechlorotrifluoroethylene

60 (Excellent)

Oxygen index range above 90% Fluorinated ethylene-propylene Perfluoroalkoxyethelne Polytetrafluoroethylene UPVC - Unplasticised PVC Source: Author’s own files

98

95 (Excellent) 95 (Excellent) 95 (Excellent)

Flammability Characteristics Some types of polymers are not yet available commercially as fire retardant formulations. Their fire retardant characteristics are given in Table 6.9.

Table 6.9 Flammability characteristics of non-flame retardant polymers for which flame retardant versions, (i.e., with non-flammable additives) are not commercially available Oxygen index (%)

Flammability (UL 94) [A]

Flame spread

Low-density polyethylene

17

HB

Very poor

Crosslinked polyethylene

17

HB

Very poor

High-density polyethylene

17

HB

Very poor

PMMA

18

HB

Poor

Styrene-acrylonitrile

18

HB

Very poor

Ethylene-vinyl acetate

19

HB

Very poor

Styrene-maleic anhydride

19

HB

Very poor

Acrylate-styrene-acrylonitrile

19

HB

Very poor

PU

19

HB

Very poor

Plasticised PVC

24

V2

Good

Phenol-formaldehyde

25

HB

Good

Diallylisophthalate

27

V1

Poor

Urea formaldehyde

30

V0

Very good

Polysulfone

30

V1

Good

Acrylonitrile-butadiene–styrene

30

V0

Poor

Polymer

Source: Author’s own files

Key mechanical and electrical properties of intrinsically fire retardant polymers (i.e., LOI > 30%) are listed in Tables 6.10 and 6.11, respectively.

99

Characteristics and Analysis of Non-Flammable Polymers

Table 6.10 Key mechanical properties of intrinsically flame retardant polymers Oxygen index (%)

Elongation at break (%)

Tensile strength (MPa)

Flexural modulus (GPa)

Polysulfone

30 (Very good)

80 (Very good)

70 (Good)

2.68 (Poor)

Ethylene tetrafluoroethylene

31 (Very good)

150 (Very good)

58 (Poor)

1.4 (Very poor)

Polyvinyl fluoride

35 (Very good)

150 (Very good)

40 (Very poor)

1.4 (Very poor)

Polyether ether ketone

35 (Very good)

50 (Very good)

92 (Very good)

Poor

Polyether sulfone

36 (Very good)

60 (Very good)

84 (Very good)

2.65 (Poor)

Unsaturated PVC

40 (Very good)

60 (Very good)

51 (Very poor)

3.00 (Poor)

Silicone

40 (Very good)

2 (Poor)

28 (Very poor)

3.5 (Poor)

Polyamide imide

43 (Very good)

36 (Good)

185 (Excellent)

4.58 (Good)

Polyvinylidene fluoride

46 (Very good)

86 (Very good)

Poor

Very poor

Polyetherimide

47 (Very good)

60 (Very good)

105 (Very good)

3.3 (Very good)

Chlorinated PVC

50 (Very good)

30 (Good)

68 good

3.1 (Poor)

Polyimide

53 (Very good)

Good

Good

Poor

Ethylene chlorotrifluoroethylene

60 (Excellent)

200 (Very good)

30

17

PTFE

95 (Excellent)

400 (Excellent)

25 (Very poor)

0.7 (Very poor)

Perfluoroalkoxyethylene

95 (Excellent)

300 (Excellent)

29 (Very poor)

07 (Very poor)

Fluorinated ethylene propylene

95 (Excellent)

150 (Very good)

14 (Very poor)

0.6 (Very poor)

Polymer

Source: Author’s own files

100

Flammability Characteristics

Table 6.11 Key electrical properties of intrinsically flame retardant polymers Volume Dielectric Dielectric Dissipation Oxygen resistivity Polymer strength constant factor at 1 index (%) (log Ohm(mV/m) at 1 kHz kHz cm) Polysulfone

30 (Very good)

16.0 (Very good)

16.7 (Poor)

3.5 (Very good)

0.001 (Good)

Tetrafluoroethylene

31 (Very good)

16 (Very good)

25 (Good)

2.6 (Very good)

0.0008 (Good)

Polyvinyl fluoride

35 (Very good)

13 (Poor)

20 (Good)

8 (Very poor)

0.5 (Very poor)

Polyether ketone

35 (Very good)

16.7 (Very good)

19 (Good)

3.2 (Very good)

0.0016 (Very good)

Polyether sulfone

36 (Very good)

17.5 (Very good)

16 (Poor)

3.5 (Good)

0.0021 (Good)

UPVC

40 (Very good)

14 (Good)

14 (Good)

3.1 (Very good)

0.025 (Poor)

Silicone

40 (Very good)

15 (Good)

15.8 (Poor)

2.9 (Very good)

0.002 (Good)

Polyamide imide

43 (Very good)

17 (Very good)

23 (Very good)

3.5 (Good)

0.0001 (Very good)

46 (Very good)

5 (Very poor)

-

-

-

Polyether imide

47 (Very good)

16 (Good)

24 (Good)

3.15 (Very good)

0.00013 (Very good)

Chlorinated PVC

50 (Very good)

14 (Very poor)

14 (Very poor)

3.1 (Very good)

0.025 (Very poor)

Polyimide

53 (Very good)

Very good

Good

Good

Good

Ethylene chlorotrifluoroethylene

60 (Excellent)

15 (Good)

40 (Excellent)

2.6 (Very good)

0.002 (Poor)

PTFE

95 (Excellent)

18 (Excellent)

45 (Excellent)

2.1 (Excellent)

0.0001 (Excellent)

Perfluoroalkoxyethylene

95 (Excellent)

18 (Excellent)

45 (Excellent)

2.1 (Very good)

0.0002 (Very good)

95 (Excellent)

18 (Excellent)

50 (Excellent)

2.1 (Excellent)

0.0002 (Excellent)

Polyvinylidene fluoride

Fluorinated ethylene propylene Source: Author’s own files

101

Characteristics and Analysis of Non-Flammable Polymers

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Characteristics and Analysis of Non-Flammable Polymers 65. S.L. Madorsky in Thermal Degradation of Organic Polymers, WileyInterscience, New York, NY, USA, 1964, p.238. 66. M. Lewin, A. Basch and M. Lewin in Flame-Retardant Polymeric Materials, Volume 2, Eds., M. Lewin, S.M. Atlas and E.M. Pearce, Plenum, Press, New York, NY, USA, 1978, p.1. 67. J.W. Hastie and C.L. McBee, Mechanistic Studies of Triphenylphosphine Oxide-Poly(Ethyleneterephthalate) and Related Flame Retardant Systems, National Bureau of Standard Final Report, 1975, NBSIR 75-741, National Bureau of Standards, Washington, DC, USA, 1975. 68. A.E. Sherr, H.C. Gillham and H.G. Klein in Stabilization of Polymers and Stabilizer Processes, Ed., N.A. Platzer, ACS Advances in Chemistry Series Volume 85, ACS, Washington, DC, USA, 1968, p.307. 69. S.K. Brauman, Journal of Fire and Flammability, 1976, 6, 41. 70. S.K. Brauman, Journal of Fire Retardant Chemistry, 1977, 4, 1, 18. 71. E.D. Weil in Flame Retardancy of Polymeric Materials, Volume 4, Eds., W.C. Kuryla and A.J. Papa, Marcel Dekker, New York, NY, USA, 1978, p.31. 72. L. Zabski, W. Walczyk and Z. Jedlinski, Chemicke Zvesti, 1976, 30, 3, 311. 73. ASTM D2863, Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index), 2012. 74. JIS K7201-2, Plastics - Determination of Burning Behaviour by Oxygen Index - Part 2: Ambient-Temperature Test, 2007. 75. K.S. Annakutty and K. Kishore, Polymer, 1988, 29, 7, 1273. 76. L. Iturri, Plast’ 21, 1996, 52, 26. 77. M.A. Espinoso, M. Galià and V. Càdiz, Journal of Polymer Science, Part A: Polymer Chemistry Edition, 2004, 42, 14, 3516. 78. J.H. Koo, E. Lao, W. Ho, K. Ngyuen, J. Cheng, L. Pilato, G. Wissler and M. Ervin in Proceedings of the SAMPE Fall Technical Conference: Global Advances in Materials and Process Engineering, Dallas, TX, USA, 2006, Paper No.32.

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Flammability Characteristics 79. L. Du, B. Qu and M. Zhang, Polymer Degradation and Stability, 2007, 92, 3, 497. 80. H. Liang and W. Shi, Polymer Degradation and Stability, 2004, 84, 3, 525. 81. G. Ribera, L.A. Mercado, M. Galià and V. Cádiz, Journal of Applied Polymer Science, 2006, 99, 4, 1367. 82. L.A. Mercado, M. Galià and J.A. Reina, Polymer Degradation and Stability, 2000, 91, 11, 2588. 83. G. Camino, L. Costa and M.P.L. Di Cortemiglia, Polymer Degradation and Stability, 1991, 33, 2, 131. 84. S.W. Zhu and W.F. Shi, Polymer Degradation and Stability, 2003, 80, 2, 217. 85. M. Spontón, J.C. Ronda, M. Galià and V. Cádiz, Journal of Polymer Science Part A: Polymer Chemistry, 2007, 45, 11, 2142. 86. L.A. Mercado, J.A. Reina and M. Galià, Journal of Polymer Science Part A: Polymer Chemistry Edition, 2006, 44, 19, 5580. 87. J.E Connell, E. Metcalf and M.J.K. Thomas, Polymer International, 2000, 49, 10, 1092. 88. M. Harada, S. Minamigawa and M. Ochi, Journal of Applied Polymer Science, 2008, 110, 5, 2649.

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Characteristics and Analysis of Non-Flammable Polymers

108

7

Intumescent Polymers

7.1 Intumescent Polypropylene and Polyethylene Polypropylene (PP), for example, burns very easily and dripping is observed during its combustion. The use of virgin PP is thus limited when flammability properties are required. Several approaches have been developed to increase its fire-retardant properties. Hornsby [1] reviewed the approach of using classical fillers in PP to increase its fire-retardancy behaviour. With classical fillers, the main problem is the loading (typically between 40% and 60% of total mass), which directly affects the mechanical properties of the polymer. Another problem is that the filler must be treated to increase its interfacial adhesion with the matrix. Another solution to improve the fire-retardant (FR) properties of polymers is the use of intumescent additives [2, 3]. Intumescent technology [4, 5] has found a place in polymer science as a method of imparting flame retardancy to polymeric materials. On heating, FR intumescent materials form a foamed cellular charred layer on their surfaces [6, 7], which protects the underlying materials from the action of heat flux and flame. The proposed mechanism [8] is based on the charred layer acting as a physical barrier, which retards heat and mass transfer between the gas and the condensed phase. The first generation of carbonisation agents used in intumescent formulations for thermoplastics consist of polyols, such as pentaerythritol, mannitol, or sorbitol [911]. Problems include the migration/blooming of the additives, their water solubility, and their reaction with the acid source during the processing of the formulation. Polyethylenic polymers are used in many fields such as building materials, transport or electrical engineering applications. Due to their chemical constitution, these polymers are easily flammable and so, flame retardancy becomes an important requirement for many of them. This can be obtained in several ways, one of these being incorporation of additives. Halogen compounds were widely used for this purpose, but their corrosiveness, the toxicity of their combustion products and their smoke production has promoted an interest in developing halogen-free flame-retardants [11-14]. A solution of limiting the burning mechanism can be by developing on the outer surface of the polymer, a glassy [15] or an expanded shield [16] which may at least

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Characteristics and Analysis of Non-Flammable Polymers partially, limit the transfer of fuel to the gas phase, the transfer of heat from the flame to the condensed phase and eventually oxygen diffusion in the condensed phase. In particular, FR intumescent materials are halogen-free and form on heating, foamed cellular charred layers on the surface, which protect the underlying material from the action of the heat flux or of a flame. Generally, intumescent formulations contain three active ingredients [5, 16]: an acid source (phosphate, borate): a carbonisation compound (polyols) and a blowing agent (melamine, isocyanurate). First the acid source breaks down to yield a mineral acid. Then, it takes a part in the dehydration of the compound to yield the carbon char and finally, the blowing agent decomposes to yield gaseous products. The gaseous products cause the char to swell and thus provide the insulating material, which then decomposes under the action of the outer heat flux. Three different types of halogen-free intumescent charring agents have been identified [17] (Table 7.1). All those compounds lead to the formation of a superficial char layer that prevents further decomposition but they act in three different ways: • Ammonium polyphosphate (APP) leads to the formation of a char layer through the linking of phosphates to the ester group; the latter are readily eliminated forming conjugated double bonds, which finally cyclise to give a char [18]. • Melamine cyanurate (MC) acts through endothermic decomposition and formation of condensation polymers such as melamine, which constitutes the superficial char layer [19]. Two schemes of condensation have been proposed [20]: the first states that condensation leads to the fused-ring structure of cyanuric triamide which reacts as a trifunctional monomer to give the final condensate; the second states that the melamine unit is the trifunctional monomer which progressively condenses to give a product in which triazine rings are linked by –NH– bridges. • Expandable graphite (EG) leads to the formation of a char layer characterised by the presence of ‘worms’, deriving from its expansion. According to some authors [21], the expansion of EG is due to a redox process between sulfuric acid, intercalated between graphic layers, and the graphite itself that originates the blowing gases according to the reaction:



110

C + 2H2SO4 → CO2 + 2H2O + 2SO2

Intumescent Polymers

Table 7.1 Results of fire behaviour tests based on DIN 4102-2 [22] Sample

Ignited on Corner

Ignited on Surface

Ammonium polyphosphate (APP)

-

Not B2

Not B2

Melamine cyanurate (MC)

-

Not B2

Not B2

B2

B2

B2

Expanded graphite (EG)

Reproduced with permission from M. Modesti and A. Lorenzetti, Polymer Degradation and Stability, 2002, 78, 341. ©2002, Elsevier [17]

7.1.1 Nanoplatelet/Nanofibre Modified Polymer Matrices Increased flammability resistance has been noted to be an important property enhancement involving nanoplatelet/nanofibre modification of polymeric matrices. While the specific reasons for this are under continuing investigation, a qualitative explanation observed in many studies involves the formation of a stable carbon/ nanoplatelet or nanofibre surface. This surface exhibits analogous characteristics to intumescent coatings whereby the resultant ‘char’ provides protection to the interior of the specimen by preventing continual surface regeneration of available fuel to continue the combustion process. The primary advantage noted with nanofiller incorporation is the reduction in the maximum heat release rate (HRR) (determined by cone calorimetry) [23, 24]. While significant reductions can be observed in the maximum HRR, the total heat release remains constant with nanofiller addition. The relevance of reducing the maximum HRR is to minimise the flame propagation to adjacent areas in the range of the ignited material (dimensions in the range of meter). The flammability improvements for nanofiller addition are less advantageous when the more common empirical regulatory (pass/fail) lammability, i.e., UL 94 [25], ASTM flammability tests [26, 27] are used. In specific cases, the nanoparticle addition can result in a reduced flammability rating due to the melt viscosity increase preventing dripping as a mechanism of lame extinguishing (e.g., changes a UL 94 rating from V2 to HB) [27]. The primary advantage for nanofiller addition for these tests generally involves reduction in the amount of FR additives that need to be incorporated to pass the specific test [27, 28]. This has been observed in various nanoparticle modified composites including exfoliated clay with halogen-based flame retardants/antimony trioxide (Sb2O3) [29] and ethylene vinyl acetate copolymer (EVA) nanocomposites with magnesium hydroxide nanoparticles and microencapsulated red phosphorus [30]. The majority of the FR studies on nanofiller incorporation in polymers involve exfoliated clay. Studies involving polyamide-6 (PA-6) [24, 31] and PP [32] yielded

111

Characteristics and Analysis of Non-Flammable Polymers similar observations with reduced peak HRR as measured by cone calorimetry but no change in the total heat release with exfoliated clay addition. While the curve position and shape will vary for different polymer matrix materials and nanofiller incorporation, the generalised behaviour of the decreased peak HRR with basically no change in the overall heat release (area under the curve) is very typical. The surface characteristics during and after forced combustion show that incomplete surface coverage will lead to poorer flammability resistance and can be related to low nanofiller level, low aspect ratio, poor dispersion and/or agglomeration during combustion. This generalised behaviour is true for exfoliated clay as well as carbon nanotubes as discussed next. Studies involving carbon nanotubes have also shown that the decrease in the peak HRR with no change in the total heat release, occurs with an effectiveness equal to or better than exfoliated clay [33, 34]. The level of dispersion of the carbon nanotubes in the polymer matrix was shown to be an important variable [33]. Upon combustion, the surface layer was enriched with a protective nanotube network providing a thermal and structural barrier to the combustion process. Continuity of the network was important to achieve optimum performance at very low levels of nanotube incorporation. Poor dispersion did not allow a continuous surface network during the combustion process. It was noted that the incorporation of nanoclay and carbon nanotubes often results in a slightly earlier ignition than the unmodified polymer presumably due to the increased thermal conductivity. However, at the later stages of combustion the reinforcement of the char layer provides a stable thermal barrier preventing regeneration of polymer at the surface available for rapid combustion. Paul and Robeson [35] have reviewed polymer nanotechnology including a study of polymer matrix-based nanocomposites and exfoliated clay-based nanocomposites. Intumescence of polyethylene (PE) and PP has been reviewed using as intumescent agents: zeolites [36], melamine phosphate and pentaerythritol [37]. Ammonium polyphosphate-pentaerythritol [38], zinc borate and ammonium polyphosphate [39], and APP [40], limiting oxygen index (LOI) [36, 37], cone calorimetry [36] and the UL 94 test [25, 36, 37] have all been used in these studies. For melamine phosphate-pentaerythritol-polypropylene, the char former/blowing agent ratio was shown to have a significant effect on flame retardancy [37].

7.2 Polypropylene-Polyamide-6 Almeras and co-workers [40] studied the efficiency of various compatabilising agents in intumescent PP-PA-6-APP blends. It was shown that addition of APP and PA-6

112

Intumescent Polymers imparts desired ire properties to the blends. In particular, the LOI increases from 17-32 vol% O2 when PP is blended with a combination of APP, PA-6 and EVA. Moreover, oxygen consumption calorimetry shows a significant decrease in the peak of HRR from 1500 kW/m2 (virgin polymer [41-44]) to 320 kW/m2 for the blend. However, the stability of the APP/PA-6 blends obtained by direct mixing of APP in molten PA-6 is low because of the poor compatibility of APP and PA-6; a migration of the mineral salt [45] occurs during solidification of molten blend versus time, and, thus, an interfacial agent is needed to prevent the exudation phenomenon. EVAx (where x is the percentage of vinyl acetate) are known to be efficient interfacial agents [46, 47]. Moreover, incorporating APP/PA-6 into EVAx confers improved ire properties. Ethylene-butyl acrylate-maleic anhydride (EBuAMA) and EVAx have been used as interfacial agents in polyoleins [48]. Moreover, it has been shown that these interfacial agents [41, 42] directly influence the fire properties. In particular, an acidity reinforcement of the intumescent char was proposed to explain the synergistic effect of EVA. Although the effect of interfacial agent on the ire properties has been investigated, no investigation on the blend morphology has been carried out.

7.3 Intumescent Polystyrene and Polymethyl Methacrylate Ebdon and co-workers [49] observed that with formulations comprising polystyrene or methyl methacrylate (MMA) and vinyl phosphonic acid, dialkyl vinyl phosphates or vinyl and allylphosphine oxides, all the phosphorus containing polymers produced an intumescent char on burning. These polymers have LOI values higher than those of the parent homopolymers indicating significant flame retardance involving condensed-phase mechanisms. But although there are general correlations between LOI, char yield and phosphorus content, some copolymers have higher than expected LOI and/or char yield, whilst others have lower, indicating that the phosphorus environment is significant. So that mechanisms of FR could be investigated in more detail, laser pyrolysis/time-of-flight mass spectrometry and mass spectrometric thermal analysis were applied to study the decomposition behaviour of three of the MMA copolymers containing (a) pyrocatecholvinylphosphate (MMA-PCVP), (b) diethyl-pvinyl-benzylphosphonate (MMA-DEpVBP) and (c) di(2-phenylethyl) vinylphosphate (MMA-PEVP) as co-monomers. The laser pyrolysis experiments provided information on probable polymer behaviour behind the flame front in a polymer fire and reveal that copolymerisation of MMA with the comonomers does not greatly alter the pyrolysis mechanism compared with that of polymethyl methacrylate (PMMA). The amounts of MMA monomer evolved during pyrolysis, however, are much reduced for the copolymerised samples. Since MMA is the major fuel evolved during the combustion of PMMA and its copolymers, this effect must be a major contributing factor to the reduced lammability shown by the copolymers. MMA-DEpVBP underwent

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Characteristics and Analysis of Non-Flammable Polymers the most extensive decomposition following laser pyrolysis. Significant amounts of highly flammable methane and ethane in particular were detected. Such increased amounts would also occur if the copolymer were to be exposed to high temperature conditions when burnt. Hence, it seems reasonable that the MMA-DEpVBP has a lower LOI value than anticipated, despite it giving a relatively high yield of char. Mass spectrometric thermal analysis studies of the MMA-PEVP provide evidence that the PEVP unit decomposes around 200 °C, eliminating styrene, with the evolution of MMA reaching a maximum about 50 °C higher. Possible mechanisms for these processes are suggested.

7.4 Intumescent Ethylene-Vinyl Acetate Copolymer Le Bras and co-workers [50] developed lame retardant intumescent formulations using the association of APP as the acid source and PA-6 as the carbonisation agent in an EVA (8%) copolymer matrix. Insertion of APP-PA-6 in EVA leads to a significant improvement in the fire performance of the material [51, 52]. Interesting results are obtained in EVA with the intumescent (APP/PA-6) system at 30 wt% or 40 wt% loading. The optimal LOI ratio for APP/PA-6 is 5 wt%/wt and the UL 94 V0 rating (vertical lame test) is achieved [25, 48, 53, 54]. The cone calorimeter allows the simulation of the conditions of fire at a small bench scale and to measure in particular, the heat release during combustion using oxygen consumption calorimetry [55-57]. Indeed, it has now been established that the property, which most critically defines a fire is the HRR [58–63], because two conditions are necessary for a fire to propagate from the product first ignited to another one, in the surroundings. First, sufficient energy, as heat, needs to be released to cause secondary ignition. Secondly, the heat release needs to occur sufficiently fast so that the heat it not quenched in the ‘cold’ air surrounding the latter product. The virgin polymer has a RHR maximum at about 1800 kW/m2 whereas the RHR of the EVA-APP/PA-6 formulation is only about 400 kW/m2. In order to understand the ire behaviour of the EVA-APP/PA-6 formulation, Le Bras and co-workers [50] deal with the chemical characterisation of the intumescent materials formed during combustion in the conditions that occur in a cone calorimeter.

114

Intumescent Polymers

7.5 Intumescent Styrene-Butadiene Copolymer Claire and co-workers [64] observed that when a mixture of APP, pentaerythritol and melamine is applied for fire proofing of intumescent styrene-butadiene, cyanide is obtained in the gas combustion product at high temperature.

7.6 Intumescent Polyisocyanurate Polyurethane Foams EG-triethylphosphate (TEP) [17, 65], APP-melamine ammonium phosphate and APP-PA-6 and cyanurate-EG [66] have all been used in intumescent studies on polyisocyanurate-polyurethane (PU) foams. TEP-EG illed PU foams [65] showed an overall improvement of their ire behaviour, the LOI increasing and the RHR decreasing with increasing iller content. The best ire performance was obtained using TEP and EG in a synergistic combination. The results of the cone calorimeter analyses are shown in Figures 7.1-7.4. The ignition time is always very low (about 5 seconds) because of the cellular structure of the samples, the high level of radiant flux and the high flammability of the blowing agent. The results obtained for RHR (Figures 7.1 and 7.2) show that both the EG and TEP lead to a significant reduction of both peak and mean values. The carbon monoxide/ carbon dioxide (CO/CO2) weight ratio (Figures 7.3 and 7.4) represent the extent of complete combustion: the greater this ratio, the lower the combustion completeness, and therefore the greater the toxicity of the smoke developed and consequently the more dangerous the material. From these results it can be observed that the CO/CO2 weight ratio increases signiicantly only in the presence of very high EG content (25 wt%), while the increase in TEP content does not affect this ratio considerably. Physical-mechanical and morphological characterisation shows that in these polymers the presence of filler causes only slight worsening of physical and mechanical properties. In particular the greatest effect of flame retardants has been seen on the thermal conductivity for EG illed foams. The filled foams show an overall improvement of their fire behaviour; the higher the iller content the higher the LOI and the lower the RHR. In particular, the best ire performances are obtained using both TEP and EG in synergistic combination.

115

Characteristics and Analysis of Non-Flammable Polymers 200

Peak Average

180

RHR (kW/m2)

160 140 120 100 80 60 40 20 0 0

5

10

15

20

25

Figure 7.1 RHR and average values as a function of the amount of EG. Reproduced with permission from M. Modesti, A. Lorenzetti, F. Simioni and G. Camino, Polymer Degradation and Stability, 2002, 77, 2, 195. ©2002, Elsevier [65]

140 Peak Average

RHR (kW/m2)

120 100 80 60 40 20 0 0

0.5

1

1.5

2

2.5

3

Figure 7.2 RHR and peak and average values as a function of the amount of triethylphosphate (TEP). Reproduced with permission from M. Modesti, A. Lorenzetti, F. Simioni and G. Camino, Polymer Degradation and Stability, 2002, 77, 2, 195. ©2002, Elsevier [65]

116

Intumescent Polymers

CO/CO2 average value [kg/kg]

0.10 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 0

5

10

15

20

25

Figure 7.3 CO/CO2 average values as a function of the amount of EG. Reproduced with permission from M. Modesti, A. Lorenzetti, F. Simioni and G. Camino, Polymer Degradation and Stability, 2002, 77, 2, 195. ©2002, Elsevier [65]

CO/CO2 average value [kg/kg]

0.10 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 0

0.5

1

1.5

2

2.5

3

Figure 7.4 CO/CO2 average values as a function of the amount of TEP. Reproduced with permission from M. Modesti, A. Lorenzetti, F. Simioni and G. Camino, Polymer Degradation and Stability, 2002, 77, 2, 195. ©2002, Elsevier [65]

117

Characteristics and Analysis of Non-Flammable Polymers Modesti and co-workers [65] and Modesti and Lorenzetti [17] studied the effects of different charring agents on the physical-mechanical properties and fire behaviour. They investigated the effect of varying the amounts of APP, MC and EG. When involved in the fire they all lead to the formation of a char layer on the polymer surface, but their ways of providing fire retardancy are different. APP leads to the formation of a char layer through the linking of phosphates to the ester group. MC acts through endothermic decomposition leading to evolution of ammonia and formation of condensation polymers. EG leads to formation of a char layer characterised by the presence of ‘worms’ resulting from its expansion. It was found that the higher the iller content the lower the compression strength. The presence of APP and MC results in worsening of thermal conductivity while the EG leads to an increase in thermal conductivity. Cone calorimetry and the LOI test were used to study the ire behaviour and the best results were obtained with the EG. The fire reaction of filled polyisocyanurate-PU foams has been analysed by use of DIN 4102-2 [22] and LOI tests. The results of the DIN 4102-2 test are reported in Table 7.1. Only the foams illed with EG containing at least 15 wt% of iller, can be classiied as B2 materials. Pentane blown foams illed with 25% of APP and MC cannot be rated as B2. The LOI test showed that the LOI increases with increasing iller content. In particular while the presence of MC does not signiicantly change the LOI, the presence of APP and EG leads to an increase of about 25% and 35%, respectively, using 25% of the filler. The most important result from the RHR measurements is the considerable decrease that is achieved in RHR in the presence of 25 wt% of EG: the maximum value of RHR decreases by about 60% and the mean value by about 80%; the results are also satisfactory in the presence of 15 wt% of EG. Moreover, it has been observed that both APP and MC are more effective at a lower amount as the maximum RHR value is lower with 15 wt% than with 25 wt% of filler. Therefore, it seems that the flame retardancy of the foams does not increase continuously with the filler content but rather shows an optimum. No signiicant inluence of either APP or MC on the mean relative HRR was observed. The CO/CO2 weight ratio results show that in the presence of EG, the values of the CO/CO2 ratio are fairly high, while in the presence of APP or MC the ratios become lower. EG leads to formation of a char layer characterised by the presence of ‘worms’ resulting from its expansion. It was found that the higher the filler content the lower the compression strength. The presence of APP or MC results in worsening of thermal conductivity while the presence of EG leads to an increase in thermal conductivity. Cone calorimetry and the LOI test were used to study the ire behaviour. The best

118

Intumescent Polymers results were obtained with EG. The RHR peak value is believed by many ire scientists to be responsible for the ‘flashover’ phenomena in a real fire situation [67] while the CO/CO2 weight ratio, being an index of combustion completeness, can be considered as an index of smoke toxicity. At the moment, standard regulations exists only for RHR (ISO 5660 [68]), while for the other parameters the measurements are not standardised. To overcome the problems of poor repeatability of data, five specimens for each sample were submitted to each kind of test.

7.7 Intumescent Siloxone – Polyurethane Copolymers The thermal stability of siloxone-PU copolymers is similar to that of standard PU foam [66]. However, the char yield at 700 °C was higher and increased with silicon content. Cone calorimetry results showed that with 15% polydimethylsiloxane content, the HRR could be reduced to one-third that of the PU control. For this composition, the copolymer mechanical properties were comparable to those of the PU control.

7.8 Fire Retardant Additives The development of flame retardant additives for polymeric materials that could simultaneously promote both gas-phase and solid-phase types of action could result in products that are both more cost-effective and more environmentally-friendly than those currently in use [69]. These include bromoanilino triazine derivatives and bromoaryl phosphates. Both have the potential to display both solid-phase and gasphase FR activity. These were evaluated by a variety of thermal methods. Some of these compounds had the potential to display dual functional behaviour as FR, i.e., to maintain the good gas phase activity associated with organohalogen compounds while, at the same time promoting the development of protective char at the solid phase.

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Intumescent Polymers 17. M. Modesti and A. Lorenzetti, Polymer Degradation and Stability, 2002, 78, 2, 341. 18. K. Kishore and K. Mohandas, Combustion and Flame, 1981, 43, 145. 19. A.P. Taylor and F.R. Sale, Die Makromolekulare Chemie - Macromolecular Symposia, 1993, 74, 85. 20. L. Costa and G.J. Camino, Thermal Analysis, 1988, 34, 2, 423. 21. G. Camino, S. Duquesne, R. Delobel, B. Eling, C. Lindsay, T. Roels in Fire and Polymers: Materials and Solutions for Hazard Prevention, Eds., G.L. Nelson and C.A. Wilkie, ACS Symposium Series No.797, ACS, Washington, DC, USA, 2001. 22. DIN 4102-2, Behaviour of Building Materials and Components in Fire Building Components - Definitions, Requirements and Tests, 1977. 23. A.B. Morgan, Polymers for Advanced Technologies, 2006, 17, 4, 206. 24. A. Dasari, Z-Z. Yu, Y-W. Mai and S. Lui, Nanotechnology, 2007, 18, 44, 445602. 25. UL 94, Tests for Flammability of Plastic Materials for Parts in Devices and Appliances, 2013. 26. S. Bourbigot, Duquesne and C. Jama, Macromolecular Symposia, 2006, 233, 1, 180. 27. B. Schartel, M. Bartholmai and U. Knoll, Polymers for Advanced Technologies, 2006, 17, 9-10, 772. 28. S. Nazare, B.K. Kandola and A.R. Horrocks, Polymers for Advanced Technologies, 2006, 17, 4, 294. 29. M. Zanetti, G. Camino, D. Canavese, A.B. Morgan, F.J. Lamelas and C.A. Wilkie, Chemistry of Materials, 2002, 14, 1, 189. 30. J-P. Lv and W-H. Liu, Journal of Applied Polymer Science, 2007, 105, 2, 333. 31. T. Kashiwagi, R.H. Harris, Jr., X. Zhang, R.M. Briber, B.H. Cipriano, S.R. Raghaven, W.H. Awad and J.R. Shields, Polymer, 2004, 45, 3, 881. 32. H. Qin, S. Zhang, C. Zhao, G. Hu and M. Yang, Polymer, 2005, 46, 19, 8386.

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Characteristics and Analysis of Non-Flammable Polymers 33. T. Kashiwagi, F. Du, K.I. Winey, K.M. Groth, J.R. Shields, S.P. Bellayer, H. Kim and J.F. Douglas, Polymer, 2005, 46, 2, 471. 34. T. Kashiwagi, E. Grulke, J. Hilding, R. Harris, W. Awad and J. Douglas, Macromolecular Rapid Communications, 2002, 23, 13, 761. 35. D.R. Paul and L.M. Robeson, Polymer, 2008, 49, 15, 3187. 36. S. Bourgbigot and M. Le Bras in Fire Retardancy of Polymers, Eds., M. Le Bras, G. Camino, S. Bourbigot and R. Delobel, Royal Society of Chemistry, Cambridge UK, 1998, 54F, 222. 37. Y. Chen, Y. Liu, Q. Wang, H. Yin, N. Aelmans and R. Kierkels, Polymer Degradation and Stability, 2003, 81, 2, 215. 38. Z-L. Ma, J-G. Gao and L-G. Bai, Journal Applied Polymer Science, 2004, 92, 3, 1388. 39. B. Qu and R. Xie, Polymer International, 2003, 52, 9, 1415. 40. X. Almeras, N. Renaut, C. Jama, M. Le Bras, A. Toth, S. Bourbigot, G. Marosi and F. Poutch, Journal of Applied Polymer Science, 2004, 93, 1, 402. 41. S. Bourbigot and M. Le Bras in International Plastics Flammability Handbook: Principles, Regulations, Testing and Approval, 3rd Edition, Ed., J. Troitzsch, Hanser, New York, NY, USA, 2004, Chapter 5. 42. X. Almeras, F. Dabrowski, M. Le Bras, F. Poutch, S. Bourbigot, G. Marosi and P. Anna, Polymer Degradation and Stability, 2002, 77, 2, 305. 43. X. Almeras, F. Dabrowski, M. Le Bras, S. Delobel, S. Bourbigot, G. Marosi and P. Anna, Polymer Degradation and Stability, 2002, 77, 315. 44. T.J. Shields and J. Zhang in Polypropylene: An A-Z Reference, Ed., J. KargerKocsis, Kluwer Academic, Dordrecht, The Netherlands, 1999, p.247. 45. M. Le Bras, S. Bourbigot, E. Felix, F. Pouille, C. Siat and M. Traisnel, Polymer, 2000, 41, 14, 5283. 46. S.V. Levchik, L. Costa and G. Camino, Polymer Degradation and Stability, 1992, 36, 3, 229. 47. S.V. Levchik, G. Camino, L. Costa and G.F. Levchik, Fire and Materials, 1995, 19, 1, 1.

122

Intumescent Polymers 48. S. Bourbigot, M. Le Bras and C. Siat in Recent Advances in Flame Retardancy of Polymeric Materials, Volume 7, Ed., M. Lewin, BCC Publishers, Norwalk, CT, USA, 1997, p.146. 49. J.R. Ebdon, D. Price B.J. Hunt, P. Joseph, F. Gao, G.J Milnes and L.K. Cunliffe, Polymer Degradation and Stability, 2000, 69, 3, 277. 50. M. Le Bras, B. Bourbigot and B. Revel, Journal of Materials Science, 1999, 34, 23, 5777. 51. M. Le Bras, S. Bourbigot, S. Siat and R. Delobel in Fire Retardancy of Polymers – The Use of Intumescence, Eds., M. Le Bras, G. Camino, S. Bourbigot and R. Delobel, The Royal Society of Chemistry, Cambridge, UK, 1998, p.266. 52. C. Siat, M. Le Bras and S. Bourbigot, Fire and Materials, 1998, 22, 3, 119. 53. ASTM D2863, Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-like Combustion of Plastics (Oxygen Index), 2012. 54. ASTM D635, Test Method for Rate of Burning and/or Extent and Time of Burning of Plastics in a Horizontal Position, 2010. 55. C. Huggett, The Journal of Fire and Flammability, 1980, 12, 235. 56. V. Babrauskas, Development of the Cone Calorimeter – A Bench Scale Heat Release Rate Apparatus base on Oxygen Consumption, NBSIR 82-2611, US National Bureau of Standards, Gaithersburg, USA, 1982. 57. B. Babrauskas, Fire and Materials, 1984, 8, 2, 81. 58. S.J. Grayson in Heat Release in Fires, Eds., V. Babrauskas and S.J. Grayson, Taylor and Francis, London, UK, 1992, p.1. 59. M.M. Hirschler, Fire Safety Journal, 1991, 17, 3, 239. 60. M. Hirschler, Journal of Fire Sciences, 1987, 5, 289. 61. E.E. Smith in Ignition, Heat Release and Noncombustibility of Materials, ASTM STP 502, Ed., A.F. Robertson, ASTM, Philadelphia, PA, USA, 1972, p.119. 62. P.H. Thomas in Proceedings of Fire: Control the Heat, Reduce the Hazard Conference, Ed., P. Fardell, Fire Research Station, London, UK, 1998, p.1. 123

Characteristics and Analysis of Non-Flammable Polymers 63. V. Babrauskas in Proceedings of Fire: Control the Heat, Reduce the Hazard Conference, Ed., P. Fardell, Fire Research Station, London, UK, 1988, p.4. 64. E. Gaudin, C. Rossi, Y. Claire, A. Perichaud, L.E. Watik, H. Zineddine, J. Kaloustian and M. Sergent in Fire Retardancy of Polymers, Eds., M. Le Bras, G. Camino, S. Bourbigot and R. Delobel, The Royal Society of Chemistry, Cambridge, UK, 1984, 54F, 437. 65. M. Modesti, A. Lorenzetti, F. Simioni and G. Camino, Polymer Degradation and Stability, 2002, 77, 2, 195. 66. L. Wang, Q. Ji, T.E. Glass, M. Muggli, T.C. Ward, J.E. McGrath and U. Sorathia in Proceedings of the 151st ACS Rubber Division Meeting, Anaheim, CA, USA, Spring 1997, Paper No.51. 67. R. Van Speybroeck, P. Van Hess and F. Vandevelde, Cellular Polymers, 1992, 11, 2, 96. 68. ISO 5660-1, Reaction-To-Fire Tests - Heat Release, Smoke Production and Mass Loss Rate - Part 1: Heat Release Rate (Cone Calorimeter Method), 2002.

124

8

Effect of Reinforcing Agents, Fillers and Flame Retardants on Polymer Properties

8.1 Flammability Characteristics As would be expected, the incorporation of a fire retardant additive improves all fire testing parameters to the good or very good category. Higher additions of inert fillers may, in some case, improve fire retardancy characteristics over those obtained for a virgin fire retardant polymer. This occurs in the case of fire retardant polyphenylene oxide (PPO), where, as shown in Table 8.1, the addition of 30% glass fibre to the virgin polymer improves flame spread from the good to the very good category. For some non-fire retardant grades of polymers, fire retardancy characteristics might improve when a filler is incorporated into the formulation. Thus, for epoxy resins, the incorporation of minerals, glass fibre, silica or graphite all improve flame spread, flammability and LOI from the poor category for the virgin polymer to the good category. Such improvement, cannot, however, be taken for granted. No improvement in fire retardancy characteristics were observed when a wide range of fillers/reinforcing agents were incorporated into non-fire retardant: PC, PBT, PET, PA-6,6 or SAN copolymer. In some cases the incorporation of a fire retardant can affect mechanical, electrical and thermal properties of polymers. These factors should be considered before any decisions are made on the selection of a fire retardant polymer for a particular application. The incorporation of a reinforcing agent such as glass fibres into a non-fire retardant or a fire retardant formulation might also have an effect on polymer properties as discussed next.

125

Characteristics and Analysis of Non-Flammable Polymers

Table 8.1 Comparison of fire retardancy properties of non-fire retardant and fire retardant grades of polymers containing various reinforcing agents Non-fire retardant grades Fire retardant grades Polymer Filler Flame Flame Flammability LOI Flammability LOI spread spread Virgin

Poor

Poor

Poor

-

-

-

Mineral and Glass fibre

Good

Good

Good

Very good

Very good

Very good

Minerals

Good

Good

Good

-

-

-

Glass fibre

Good

Good

Good

-

-

-

Silica

Good

poor

Good

-

-

-

Carbon fibre

Good

Good

Good

-

-

-

Virgin

Poor

Poor

Poor

Good

Good

Good

10% Glass fibre

Poor

Poor

Good

Good

Good

Good

30% Glass fibre

Poor

Poor

Good

Very good

Good

Good

Virgin

Good

Poor

Poor

Very good

Very good

Very good

15% PTFE

Good

Poor

Poor

-

-

-

30% Carbon

Poor

Poor

Poor

-

-

-

20% Glass fibre

Good

Poor

Poor

-

-

-

Polyester

Virgin

Good

Good

Poor

Very good

Very good

Very good

Diallyphthalate

Virgin

Poor

Poor

Good

Very good

Very good

Good

Virgin

Poor

Poor

Poor

Very good

Good

Good

30% Glass fibre

Poor

Poor

Poor

Very good

Good

Good

Virgin 30% Glass fibre

Poor

Poor

Poor

Very good

Good

Good

Epoxies

PPO

PC

PET

126

Effect of Reinforcing Agents, Fillers and Flame Retardants on Polymer Properties

PBT

PA-6,6

SAN

35% Glass fibre

Poor

Poor

Poor

-

35% Glass fibre

-

Mineral

Poor

Poor

Poor

-

Mineral

-

45% Glass fibre

Poor

Poor

Poor

-

45% Glass fibre

-

15% Glass fibre

Poor

Very poor

Very poor

-

15% Glass fibre

-

35% Mica

Poor

Poor

Poor

-

35% Mica

-

Good

Good

Virgin

Poor

Poor

Poor

Very good

10% Carbon

Poor

Poor

Poor

-

-

-

30% Carbon

Poor

Poor

Poor

-

-

-

20% PTFE

Poor

Poor

Poor

-

-

-

40% Mineral

Poor

Poor

Poor

-

-

-

60% Glass fibre

Poor

Poor

Poor

-

-

-

Virgin

Poor

Poor

Poor

Good

Good

Good

30% Glass fibre

Very poor

Very poor

Poor

-

-

-

Poor

Poor

Poor

Very good

Good

Good

Acrylonitrilebutadiene Virgin -styrene

LOI – Limiting oxygen index PA-6,6 - Polyamide-6,6 PBT - Polybutylene terephthalate PC - Polycarbonate PET - Polyethylene terephthalate PTFE – Polytetrafluorethylene SAN - Styrene-acrylonitrile Source: Author’s own files

8.2 Effect on Physical Properties 8.2.1 Mechanical Properties The information available on the effects of fire-retardants on the mechanical properties of various polymers is given in Table 8.2.

127

128

Nil

Nil 30% Glass fibre Nil 10% Glass fibre 30% Glass fibre Nil

PA-6,6

SAN

Polyesters Nil

PP

PPO

PBT

Filler

Polymer

Poor

Poor

Poor Good

Very poor Poor

Very good

Very good Very good Poor

Good

0.05

Very poor >1.6

Good

Very poor -

Very poor -

0.16

Good

Very good

Poor

0.02

0.11

Poor

Poor

Poor

Good

Poor

-

Good

Very poor

Flexural modulus (GPa)

Poor

Good

Very poor Very poor

Very good Very good

Good

Good

-

Good

Poor

Tensile Notched strength Izod impact strength (kJ/m) (MPa)

Good

Poor

Very good

Elongation at Strain at break (%) yield (%)

Very poor -

Good

Very poor

Flexural modulus (GPa)

Very good Very good Poor

Good

Good

Tensile strength (MPa)

Poor

Good

Poor

Good

Good

Poor

Poor

Good

Good Very poor

Very poor

Very poor

Good

-

Very poor Poor

Elongation at Strain at break (%) yield (%)

Table 8.2 Comparison of mechanical properties of filled and unfilled non-fire retardant and fire retardant grades Fire retardant Polymer Filler None fire retardant grades Fire retardant grades grades

Characteristics and Analysis of Non-Flammable Polymers

Nil

PBT

fibre

Glass

30%

fibre

Glass

10%

Nil

fibre

glass

Volume

Very good

Good

Very good

Good

Good

Good

Good

Good

Very good

cm)

(Ohm-

resistivity

Source: Author’s own files

PPO

resin

Epoxy

Nil

SAN

Mineral

Nil

Nil

Nil

Filler

PA-6,6

phthalate

Diallyl-

PC

Polymer

Poor

Poor

Good

Poor

Good

Very good

Poor

Poor

MHz)

factor (1

Poor

Poor

Very poor

Very good Very good

Very good Very good

Very good Very good

Poor

Very good Poor

Very good Poor

Good

Good

Very good Poor

(1 kHz)

(mV/m)

Good

constant

strength

Dielectric Dielectric Dissipating arc

Surface

Good

Poor

Very poor

Very good

Very good

Good

Excellent

Excellent

Very poor

(Ohm)

resistance

Non-fire retardant grades Volume

Very poor

Poor

Poor

Good

Good

Poor

Excellent

Excellent

Poor

(Ohm)

Very good

Good

Very good

Good

Good

Good

Good

Good

Very good

(Ohm/m)

resistance resistivity

Tracking

Very poor

Good

Good

Very poor

Good

Good

Poor

Poor

Good

(mV/m)

strength

Dielectric

Very good

Very good

Very good

Good

Very good

Very good

Good

Good

Very good

Ohm)

(1 kHz

constant

Dielectric

Good

Good

Good

Very poor

Very poor

Poor

Poor

Poor

Poor

MHz)

factor (1

Dissipation

Fire retardant grades

Very poor

Very poor

Very poor

Very good

Good

Good

Good

Good

Very poor

(Ohm)

resistance

arc

Surface

Table 8.3 Comparison of electrical properties of filled and unfilled non-fire retardant and fire retardant grades

Very poor

Very poor

Poor

Poor

Very poor

Poor

Very good

Very good

Very poor

(Ohm)

resistance

Tracking

Effect of Reinforcing Agents, Fillers and Flame Retardants on Polymer Properties

129

130

Very good

Nil

Glass fibre and mineral

PA-6,6

Epoxy resins

Source: Author’s own files

Good

Nil

Polyesters

Very good

Good

Nil

HIPS

Poor

Nil

PP

Glass fibre Good

Poor

Nil

PBT (30%)

Very good

Nil

SAN

Good

Nil

Filler

PC

Polymer

Fire retardant grades

Very good

Poor

Good

Poor

Poor

Very good

Poor

Good

Good

Very poor

Very good

Poor

Poor

Very poor

Very poor

Poor

Very poor

Good

Good

Very good

Poor

Poor

Good

Poor

Good

Good

Very good Very good

Poor

Good

Good

Poor

Good

Very poor

Good

Good

Very good

Poor

Excellent

Poor

Poor

Very good

Poor

Poor

Good

Very poor

Good

Poor

Poor

Very poor

Very poor

Very poor

Very poor

Good

Very poor

Poor

Very good

Good

Poor

Good

Very poor

Good

Good

Heat Heat Expansion Expansion distortion Brittle Mould distortion Brittle Mould coefficient coefficient temperature temperature shrinkage temperature temperature shrinkage (mm × °C (mm × ºC at 1.8 mPa (%) (%) at 1.8 mPa, (%) (%) × 10-5) × 10-5) (ºC) (ºC)

Non-fire retardant grades

Table 8.4 Comparison of thermal properties of filled and unfilled non-fire retardant and fire retardant grades

Characteristics and Analysis of Non-Flammable Polymers

Effect of Reinforcing Agents, Fillers and Flame Retardants on Polymer Properties The incorporation of 10-30% of glass fibre into the formulation of either non-fire retardant or fire retardant grades produces improvement in tensile strength, flexural modulus and percentage elongation at break and, in the case of the fire retardant grade in the percentage strain at yield.

8.2.2 Electrical Properties The incorporation of a fire retardant additive, in the case of some polymers, produces a deterioration in surface arc resistance and tracking resistance. This has been observed in the case of diallyl phthalate, PA-6,6 and PBT. A slight deterioration in dissipation factor was also observed for PBT, PPO and PP. The incorporation of 10% to 30% of glass fibre into the non-fire retardant and fire retardant PPO formulations causes a decrease in dielectric strength.

8.2.3 Thermal Properties The only effects on the thermal properties seen from the incorporation of a fire retardant additive occurs in the case of high-impact polystyrene (HIPS) where, as shown in Table 8.4, the incorporation of a fire retardant leads to a decease in expansion coefficient and, in the case of the polyesters, where the incorporation of a fire retardant produces a small improvement in heat distortion temperature.

131

Characteristics and Analysis of Non-Flammable Polymers

132

A

ppendix 1 Particular Test Procedures

1.1 Limited Oxygen Index ASTM D2863 (2012)

Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index).

ASTM 1354 (2011)

Test Method for Heat and Visible Smoke Release Rates for Materials and Products using an Oxygen Consumption Calorimeter.

DIN 4102-2 (1977)

Behaviour of Building Materials and Components in Fire - Building Components - Definitions, Requirements and Test.

Partially superseded by DIN EN 1363-1, DIN EN 1364-1, DIN EN 1364-2, DIN EN 1365-1, DIN EN 1365-2, DIN EN 1365-3, DIN EN 1365-4

1.2 Cone Calorimetry ASTM D4809 (2012)

Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter (Precision Method).

ASTM E1354 (2011)

Test Method for Heat and Visible Smoke Release Rates for Materials and Products using an Oxygen Consumption Calorimeter.

ISO 5660-1 (2002)

Reaction-to-Fire Tests - Heat Release, Smoke Production and Mass Loss Rate - Part 1: Heat Release Rate (Cone Calorimeter Method).

133

Characteristics and Analysis of Non-Flammable Polymers

ISO 5660-2 (2002)

Reaction-to-Fire Tests - Heat Release, Smoke Production and Mass Loss Rate Part 2: Smoke Production Rate (Dynamic Measurement).

US National Bureau of Stands NBSIR 82-2611

Development of the Cone Calorimeter – A Bench-Scale Heat Release Rate Apparatus based on Oxygen Consumption.

V. Babrauskas, National Bureau of Standards, Gaithersburg, MD, USA, 1982.

1.3 Glow Wire Test VDE 0740-2-3 (2012)

Handgefuehrte Motorbetriebene Elektrowerkzeuge - Sicherheit - Teil 2-3: Besondere Anforderungen für Schleifer, Polierer und Schleifer mit Schleifblatt (IEC 60745-2-3:2006 + A1:2010 + A1:2010/Corrigendum February 2011).

1.4 Smoke Generation ASTM E84 (2012)

Test Method for Surface Burning Characteristics of Building Materials.

ASTM D2843 (2010)

Test Method for Density of Smoke from the Burning Or Decomposition of Plastics.

ISO 5659-2 (2012)

Plastics - Smoke Generation - Part 2: Determination of Optical Density by a Single-Chamber Test.

PN K02501 (2000)

Rolling Stock - Smoke Properties of Materials - Requirements and Test Methods.

1.5 Toxic Gas Production ASTM D2843 (2010)

Test Method for Density of Smoke from the Burning or Decomposition of Plastics.

DIN EN 50267-2-1 (1999)

Common Test Methods for Cables under Fire Conditions Tests on Gases Evolved During Combustion of Material From Cables - Part 2-1: Procedures - Determination of the Amount of Halogen Acid Gas.

DIN EN 50267-2-3 (1999)

Common Test Methods for Cables under Fire Conditions - Tests on Gases Evolved During Combustion of Material From Cables - Part 2-3: Procedures - Determination of Degree of Acidity of Gases for Cables by Determination of the Weighted Average of pH and Conductivity.

134

Appendix 1 Particular Test Procedures

DIN 50267-2-2 (1999)

Common Test Methods for Cables under Fire Conditions - Tests on Gases Evolved During Combustion of Material from Cables - Part 2-2: Procedures - Determination of Degree of Acidity of Gases for Materials by Measuring pH and Conductivity.

DIN 50267-1 (1998)

Common Test Methods for Cables under Fire Conditions - Tests on Gases Evolved During Combustion of Materials from Cables - Part 1: Apparatus.

DIN 53436-1 (1981)

Producing Thermal Decomposition Products from Materials in an Air Stream and their Toxicological Testing; Decomposition Apparatus and Determination of Test Temperature.

DIN EN 60695-5-1 (2003)

Fire Hazard Testing - Part 5-1: Corrosion Damage Effects of Fire Effluent - General Guidance.

PN K-02501 (2000)

Rolling Stock - Smoke Properties of Materials - Requirements and Test Methods.

135

Characteristics and Analysis of Non-Flammable Polymers

136

A

ppendix 2 Standard Test Procedures

2.1 ASTM Standards ASTM E84 (2012c)

Standard Test Method for Surface Burning Characteristics of Building Materials.

ASTM E162 (20012a)

Standard Test Method for Surface Flammability of Materials Using a Radiant Heat Source.

ASTM E662 (20012a)

Standard Test Method for Specific Optical Density of Smoke Generated by Solid Materials.

ASTM D635 (2010)

Standard Test Method for Rate of Burning and/or Extent and Times of Burning of Plastics in a Horizontal Position.

ASTM C1166 (2011)

Standard Test Method for Flame Propagation of Dense and Cellular Elastomeric, Gaskets and Accessories.

ASTM E1354 (2011b)

Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products using an Oxygen Consumption Calorimeter.

ASTM D2843 (2010)

Standard Test Method for Density of Smoke from the Burning of Decomposition of Plastics.

ASTM D2863 (2012e1)

Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle Like Combustion of Plastics (Oxygen Index).

ASTM D3014 (2011)

Standard Test Method for Flame Height, Time of Burning, and Loss of Mass of Rigid Thermoset Cellular Plastics in a Vertical Position.

ASTM D3675 (2012)

Standard Test Method for Surface Flammability of Flexible Cellular Materials Using a Radiant Heat Energy Source.

ASTM D4852 (2009e1)

Standard Practice for Evaluation of Attached Upholstery Fabrics.

2.2 Boeing Standards BSS 6853 (1999)

Code of Practice for Fire Precautions in the Design and Construction of Passenger Carrying Trains.

BSS 7239 (2011)

Boeing Procedure for Testing Toxic Gas Generation during Combustion of Polymers used in Aircraft Interiors and Construction Materials.

137

Characteristics and Analysis of Non-Flammable Polymers

2.3 DIN Specifications DIN 0866 (2003)

Audio Video and Electronic Sound Equipment Fire Safety Requirements.

DIN 4102–7 (1998)

Fire Behaviour of Building Materials and Building Components - Part 7: Roofing, Definitions, Requirements and Testing.

DIN 22118 (1991)

Conveyor Belts with Textile Plies for use in Coal Mining – Fire Testing.

DIN EN 50267-1 (1999)

Common Test Methods for Cables Under Fire Conditions Tests on Gases Evolved During Combustion of Materials from Cables - Part 1: Apparatus.

DIN EN 50267-2-1 (1999)

Common Test Methods for Cable Under Fire Conditions Tests on Gases Evolved During Combustion of Material from Cables - Part 2-1: Procedures - Determination of the Amount of Halogen Acid Gas.

DIN EN 50267-2-3 (1999)

Common Test Methods for Cables Under Fire Conditions – Tests on Gases Evolved During Combustion of Material from Cables – Part 2-3: Procedures – Determination of Degree of Acidity of Gases for Cables by Determination of the Weighted Average of pH and Electrical Conductivity.

DIN 51755 (1974)

Testing of Mineral Oils and other Combustible Liquids; Determination of Flash Point by the Closed Tester According to Abel-Pensky.

DIN 53436 (2003)

Construction Materials Fire Testing Producing Thermal Decomposition Products from Materials in a Air Stream and Toxicological Testing.

DIN EN 60695-5-1 (2003)

Fire Hazard Testing – Part 5-1: Corrosion Damage Effects of Fire Effluent – General Guidance.

DIN EN 60695-11-5 (2005)

Fire Hazard Testing - Part 11-5: Test Flames - Needle-Flame Test Method - Apparatus, Confirmatory Test Arrangement and Guidance.

DIN 75200 (1980)

Determination of Burning Behaviour of Interior Materials of Motor Vehicles.

DIN 60695-5-1 (2003)

Fire Hazard Testing - Part 5-1: Corrosion Damage Effects of Fire Effluent - General Guidance.

2.4 Underwriters Laboratory (UL) Standards UL 94 (2012)

Tests for Flammability of Plastic Materials for Parts in Devices and Appliances.

UL 746C (2012)

Polymeric Materials - Use in Electrical Equipment Evaluations.

UL 1256 (2007)

Fire Test of Roof Deck Constructions.

138

Appendix 2 Standard Test Procedures

UL 1416 (2012)

Overcurrent and Overtemperature Protectors for Radio- and Television-Type Appliances.

UL 1581 (2011)

Reference Standard for Electrical Wires, Cables and Flexible Cords.

UL 60950-1 (2011)

Information Technology Equipment – Safety – Part 1: General Requirements.

2.5 ISO Specifications ISO 834-1 (2012)

Fire Resistance Tests – Elements of Building Construction Part 1: General Requirements.

ISO 1523 (2002)

Determination of Flash Point - Closed Cup Equilibrium Method.

ISO 3814 (1989)

Tests for Measuring Reaction to Fire of Building Materials Development and Application.

ISO 5658-2 (2001)

Reaction to Fire Tests - Spread of Flame – Part 2: Lateral Spread on Building and Transport Products in Vertical Configuration.

ISO 5658-4 (2011)

Reaction to Fire Tests - Spread of Flame – Part 4: Intermediate-Scale Test of Vertical Spread of Flame with Vertically Oriented Specimen.

ISO 5659-2 (2012)

Plastics - Smoke Generation – Part 2: Determiantion of Optical Density by a Single-Chamber Test.

ISO 5660-1 (2002)

Reaction-to-Fire Tests - Heat Release, Smoke Production and Mass Loss Rate – Part 1: Heat Release Rate (Core Calorimetry Method).

ISO 19706 (2011)

Guidance for Assessing the Fire Threat to People.

2.6 Federal Air Regulations (FAR) FAR 25.853-1 (1986)

Flammability Requirements for Aircraft Seat Cushions.

2.7 VDE Specifications VDE 0860 (2011)

Audio, Video and Similar Electronic Apparatus – Routine Electrical Safety Testing in Production.

VDE 0471-2-10 (2001)

Fire Hazard Testing – Part 2-10: Glowing/Hot-Wire Based Test Methods; Glow Wire Apparatus and Common Test Procedure.

2.8 FM Standards FM 4470 (2012)

Single-Ply, Polymer-Modified Bitumen Sheet, Built-Up Roof (BUR) and Liquid Applied Roof Assemblies for use in Class 1 and Noncombustible Roof Deck Construction.

139

Characteristics and Analysis of Non-Flammable Polymers

2.9 Vehicle Safety FM USS 302 (1973)

Notice 6, Fire Testing of Vehicles.

2.10 Australian Standards AS 1530.2 (1993)

Methods for Fire Tests on Building Materials, Components and Structures - Part 2: Test for Flammability of Materials.

2.11 Dutch NEN Standards NEN 6065 (1997)

Determination of the Contribution to Fire Propagation of Building Products.

NEN 6066 (1997)

Determination of the Smoke Production During Fire of Building Products.

2.12 Polish PN Standards PN K-02501 (2000)

Rolling Stock - Smoke Properties of Materials – Requirements and Test Methods.

PN 93/C-05013 (1993)

Slow-Burning Conveyor Belts - Methods of Testing of Slow Burning.

2.13 ATS FAAR methods ATS FAAR Test specification number

Tests covered

10.04020

Ignition properties of plastic (ASTM).

10.04000

Incandescence resistance of rigid plastics in horizontal position (DIN, ASTM, CEI, UNI).

10.05470

Smoke density combustion of materials (ASTM).

10.05600

Resistance to combustion of materials used inside automotive vehicles (DIN, FED, FIAT, ISO).

10.05200

Fire resistance of building materials (ISO).

10.05050

Flame resistance of vertical specimens (DIN, CSE, UNI).

10.05020

Fire reaction of specimens exposed to radiant heat (ISO).

10.05500

Response of plastics to ignition by small flame (ASTM).

10.05400

Burning rate and flame resistance of rigid insulating materials (ASTM, UL94).

140

Appendix 2 Standard Test Procedures

10.5700

Flammability test (UL94).

10.05000

Rate of burning of rigid specimens exposed to ignition flame of 45º (ASTM D635).

10.05454

Flammability test (UL 1581).

10.04070 10.04050

Oxygen index (DIN, ASTM, BS, CCI).

10.05300

Flammability by glow wire (DIN 695, VDE 0471-2-3).

141

Characteristics and Analysis of Non-Flammable Polymers

142

A

ppendix 3 Standard Fire Retardancy Specifications Listed Under Index Type and Application of Polymer under Test

3.1 Construction Materials BSS 7239

Boeing Procedure for Testing Toxic Gas Generation During Combustion of Polymers.

ASTM E1354 (2011)

Test Method for Heat and Visible Smoke Release Rates for Materials and Products using an Oxygen Consumption Calorimeter.

ASTM D2563 (2008)

Practice for Classifying Visual Defects in Glass-Reinforced Plastic Laminate Parts.

ASTM D2843 (2010)

Test Method for Density of Smoke from the Burning or Decomposition of Plastics.

UL 1256 (2007)

Fire Test of Roof Deck Constructions.

UL 94 (2012)

Tests for Flammability of Plastic Materials for Parts in Devices and Appliances.

ISO 5660-1 (2002)

Reaction-to-Fire Tests - Heat Release, Smoke Production and Mass Loss Rate – Part 1: Heat Release Rate (Cone Calorimetry Method).

ISO 834-1 (2012)

Fire Resistance Tests - Elements of Building Construction – Part 1: General Requirements.

ISO TR 3814 (1989)

Test for Measuring ‘Reaction-to-Fire’ of Building Materials – their Development and Application.

ISO 5658 - 2 (2011)

Reaction to Fire Tests – Spread of Flame Test – Part 2: Lateral Spread on Building and Transport Products in Vertical Configuration.

ISO 5658 - 4 (2001)

Reaction to Fire Tests – Spread of Flame Test – Part 4: IntermediateScale Test of Vertical Spread of Flame with Vertically Oriented Specimen.

ISO 5659-2 (2012)

Plastics – Smoke Generation – Part 2: Determination of Optical Density by a Single-Chamber Test.

ISO TR 3814 (1989)

Test for Measuring ‘Reaction-to-Fire’ of Building Materials – Their Development and Application.

DIN 53436-1 (1981)

Producing Thermal Decomposition Products from Materials in an Air Stream and their Toxiological Testing; Decomposition Apparatus and Determination of Test Temperature.

143

Characteristics and Analysis of Non-Flammable Polymers

DIN EN 13238 (2010)

Reaction to Fire Tests for Building Products - Conditioning Procedures and General Rules for Selection of Substrates.

DIN 22118 (1991)

Conveyor Belts with Textile Plies for use in Coal Mining - Fire Testing.

DIN 4102-7 (1998)

Fire Behaviour of Building Materials and Building Components Part 7: Roofing; Definitions, Requirements and Testing.

3.2 Dutch Standards NEN 6065 (1997)

Determination of the Contribution to Fire Propagation of Building Products.

NEN 6066 (1997)

Determination of Smoke Production during Fire of Building Products.

3.3 Polish Standards PN 93/C-05013 (1993)

Slow Burning Conveyor Belts - Methods of Testing of Slow Burning.

3.4 Canadian Standards FM 4470 (2012)

Single-Ply, Polymer-Modified Bitumen Sheet, Built-Up Roof (BUR) and Liquid Applied Roof Assemblies for use in Class 1 and Noncombustible Roof Deck Construction.

3.5 Electrical Components VDE 0805-514 (2009)

Audio- und Video-Geraete und Einrichtungen der Informationstechnik - Stueckpruefungen der Elektrischen Sicherheit in der Fertigung.

ASTM D635 (2010)

Test Method for Rate of Burning and/or Extent and Time of Burning of Plastics in a Horizontal Position.

ASTM E162 (2012)

Test Method for Surface Flammability of Materials using a Radiant Heat Energy Source.

DIN VDE 0472-814 (1991)

Testing of Cables, Wires and Flexible Cords - Continuance of Insulation Effect Under Fire Conditions.

DIN EN 50267-1 (1999)

Common Test Methods for Cables under Fire Conditions Tests on Gases Evolved During Combustion of Materials from Cables – Part 1: Apparatus.

DIN EN 50267-2-1 (1999)

Common Test Methods for Cables under Fire Conditions – Tests on Gases Evolved During Combustion of Material from Cables – Part 2-1: Procedures – Determination of the Amount of Halogen Acid Gas.

144

Appendix 3 Standard Fire Retardancy Specifications Listed Under Index Type and Application of Polymer under Test DIN EN 50267-2-2 (1999)

Common Test Methods for Cables under Fire Conditions – Tests on Gases Evolved During Combustion of Material from Cables – Part 2-2: Procedures – Determination of Degree of Acidity of Gases for Materials by Measuring pH and Conductivity.

DIN EN 50267-2-3 (1999)

Common Test Methods for Cables Under Fire Conditions – Tests on Gases Evolved During Combustion of Material from Cables – Part 2-3: Procedures – Determination of Degree of Acidity of Gases for Cables by Determination of the Weighted Average of pH and Conductivity.

UL 746C (2012)

Polymeric Materials – Use in Electrical Equipment Evaluations.

UL 94 (2012)

Tests for Flammability of Plastic Materials for Parts in Devices and Appliances.

UL 1581 (2011)

Reference Standard for Electrical Wires, Cables and Flexible Cords.

UL 1416 (2012)

Overcurrent and Overtemperature Protectors for Radio- and Television-Type Appliances.

3.6 Dutch Standards for Fire Retardance of Electrical Goods NEN EN 50267-1 (1999)

Electric Cables - Common Test Methods for Behaviour Under Fire Conditions - Gases Evolved During Combustion of Material From Cables - Part 1: Apparatus.

NEN EN 50267-2-1 (1999)

Common Test Methods for Cables Under Fire Conditions - Tests on Gases Evolved During Combustion of Materials From Cables - Part 2-1: Procedures - Determination of the Amount of Halogen Acid Gas.

NEN EN 50267-2-2 (1999)

Common Test Methods for Cables Under Fire Conditions - Tests on Gases Evolved During Combustion of Materials from Cables - Part 2-2: Procedures - Determination of Degree of Acidity of Gases for Materials by Measuring pH and Conductivity.

NEN EN 50267-2-3 (1999)

Common Test Methods for Cables Under Fire Conditions - Tests on Gases Evolved During Combustion of Materials From Cables - Part 2-3: Procedure - Determination of Degree of Acidity of Gases for Cables by Determination of the Weighted Average of pH and Conductivity.

145

Characteristics and Analysis of Non-Flammable Polymers

3.7 Vehicles ASTM E662 (2012)

Test Method for Specific Optical Density of Smoke Generated by Solid Materials.

ISO 3795 (1989)

Road Vehicles and Tractors and Machinery for Agriculture and Forestry - Determination of Burning Behaviour of Interior Materials.

DIN 75200 (1980)

Determination of Burning Behaviour of Interior Materials in Motor Vehicles.

DIN 4102 (1977)

Behaviour of Building Materials and Components in Fire.

3.8 Federal Motor Vehicle Safety Standard FMVSS 302 (1973)

Notice 6, Test Procedures and Specimen Preparation.

FMVSS 302 (1973)

Notice 7, Federal Regulation Proposed Covered Components.

3.9 Aircraft and Aerospace BSS 7239

Boeing Procedure for Testing Toxic Gas Generation during Combustion of Polymers in Aircraft Interiors and Construction Materials.

3.10 Federal Air Regulation ISO 5659-2 (2012)

Plastics - Smoke Generation – Part 2: Determination of Optical Density by a Single-Chamber Test.

3.11 Furnishings and Decorative Materials ASTM E162 (2012)

Test Method for Surface Flammability of Materials using a Radiant Heat Energy Source.

ASTM D2843 (2010)

Test Method for Density of Smoke from the Burning or Decomposition of Plastics.

UL 1715 (2008)

Fire Test of Interior Finish Materials.

ASTM 2863 (2012e1)

Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index).

3.12 Rolling Stock ASTM E662 (2012)

Test Method for Specific Optical Density of Smoke Generated by Solid Materials.

ASTM D3675 (2012)

Test Method for Surface Flammability of Flexible Cellular Materials using a Radiant Heat Energy Source.

146

Appendix 3 Standard Fire Retardancy Specifications Listed Under Index Type and Application of Polymer under Test BS 6853 (1999)

Code of Practice for Fire Precautions in the Design and Construction of Passenger Carrying Trains.

PN K-02501 (2000)

Rolling Stock - Smoke Properties of Materials - Requirements and Test Methods.

147

Characteristics and Analysis of Non-Flammable Polymers

148

A

bbreviations

(LOI)m

The minimum percentage of oxygen required in a nitrogen-oxygen atmosphere surrounding the sample to maintain its combustion for at least 30 seconds after ignition

Al(OH)3

Aluminium hydroxide

APDS

Bis(4-aminophenoxy)dimethyl silane

APP

Ammonium polyphosphate

ASTM

American Society for Testing and Materials

ATH

Aluminium trihydrate

ATS

Air Traffic Services

BAMPO

Bis(3-aminophenyl)methyl phosphine oxide

BGDMSB

1,4-Bis(glycidyloxydimethyl silyl)-benzene

BPA

Bisphenol A

BPC II

1,1-Dichloro-2,2-bis(4-hydroxylphenyl)ethylene

BS

British Standard

BSS

Boeing Standard

CEI

Comitato Elettrotecnico Italiano

Chalcon II

4,4´-Dihydroxy-3-ethoxy benzylidenoacetophenone polyarylate

CO

Carbon monoxide(s)

CO2

Carbon dioxide

149

Characteristics and Analysis of Non-Flammable Polymers CPE

Chlorinated polyethylene

CSA

Canadian Standards Association

CSPE

Chlorosulfonated polyethylene

DAEEP

Diacryloyloxyethyl ethyl phosphate

DDM

Diaminodiphenylmethane

DEpVBP

Diethyl-p-vinyl benzylphosphonate

DGMPS

Diglycidyloxy methylphenyl silane

DIN

Deutsches Institut für Normung eV

Ds

Smoke density

EBuAMA

Ethylene - butyl acrylate - maleic anhydride

EG

Expandable/expanded graphite

EVA

Ethylene vinyl acetate copolymer

FAA

Federal Aviation Authority

FAAR

Federal Aviation Administration Requirements

FAR

Federal Aviation Regulation

FED

Federal standards

FIAT

Fabbrica Italiana Automobili do Torino

FMVSS

Federal Motor Vehicle Safety Standard

FR

Fire retardant(s)

FR-PC

Fire-retardant polycarbonate

GC

Gas chromatography

Gly-HPO

(2,5-Dihydroxphenyl)diphenyl phosphine oxide

GM

General Motors

150

Abbreviations GRP

Glass reinforced polyester

H-DS

Dodecyl sulfate (anion modified)

HACP

Hexacrylated cyclophosphazene with UV reactive acrylic groups

HB

Horizontal burn

HBF

Horizontal burned foam

HBr

Hydrogen bromide

HCl

Hydrogen chloride

HCN

Hydrogen cyanide

HECP

Hexacrylated cyclophosphazene with non-reactive ethyl groups

HF

Heat flammability

HF-1

Horizontal foam-1

HF-2

Horizontal foam-2

HIPS

High-impact polystyrene

HOC

Heat output coefficient

HPR

Heat production rate

HRR

Heat release rate(s)

Is

Flame spread index

ISO

International Organization for Standardization

LDPE

Low-density polyethylene

LLDPE

Linear low-density polyethylene

LOI

Limiting oxygen index(s)

LOX

Liquid oxygen

LTTR

Long-term thermal resistance

151

Characteristics and Analysis of Non-Flammable Polymers MC

Melamine cyanurate

Mg(OH)2

Magnesium hydroxide

MMA

Methyl methacrylate

MS

Mass spectrometry

NASA

National Aeronautics and Space Administration

NBS

National Bureau of Standards

ND

Not detected

NIST

National Institute of Science and Technology

NMR

Nuclear magnetic resonance

OIT

Oxygen index test

PA-6

Polyamide-6

PA-6,6

Polyamide-6,6

PBB

1,4-Butanediol - butyl phosphorodichloridate

PBE

Ethylene glycol - butyl phosphorodichloridate

PBT

Polybutylene terephthalate

PBTD

PBB-toluene diisocyanate

PC

Polycarbonate

PCFC

Pyrolysis combustion flow calorimetry

PE

Polyethylene

PEEK

Polyetheretherketone

PET

Polyethylene terephthalate

PETD

PBE-toluene diisocyanate

PEVP

Di(2-phenylethyl) vinylphosphonate

152

Abbreviations PI

Polyisocyanurate

PMMA

Polymethylmethacrylate

PP

Polypropylene

ppm

Parts per million

PPO

Polyphenylene oxide

PS

Polystyrene

PTFE

Polytetrafluoroethylene

PU

Polyurethane(s)

PVC

Polyvinylchloride

Py

Pyrolysis

Py-GC-MS

Pyrolysis-gas chromatography-mass spectrometry

RHR

Rate of heat release(s)

SAN

Styrene-acrylonitrile

Sb2O3

Antimony trioxide

SBI

Single burning item

SEA

Specific extinction areas

SnO

Tin hydroxide

SnO2

Tin dioxide

SnZn(OH)6

Zinc hydroxy stannate

SPR

Smoke production rate

T0.5

The temperature at 50% weight loss

TAEP

Triacryloyloxyethyl phosphate

TC

Technical Committee

153

Characteristics and Analysis of Non-Flammable Polymers TEP

Triethyl phosphate

Tg

Glass transisition temperature

TGA

Thermogravimetric analysis

TMAH

Tetramethylammonium hydroxide

TNO

Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek (Netherlands Organisation for Applied Scientific Research)

ToF-MS

Time-of-flight mass spectrometry

TS

Percentage stability

UL

Underwriters’ Laboratories

UNI

Italian Organization for Standardization

UPVC

Unplasticised PVC

UV

Ultraviolet

V0

Burning stops within 10 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.

V1

Burning stops within 30 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.

V2

Burning stops within 30 seconds on a vertical specimen; drips of flaming particles are allowed.

VDE

Verband Deutscher Elektroingenieure (German Equivalent of IEEE)

ZnSnO3

Zinc stannate

154

I

ndex

A

abcd abcd abcd

Acetate copolymers, 21 Acrylic acid, 70 Acrylonitrile, 97, 99, 127 Additives, 1, 3, 8, 19, 22-23, 25-26, 47-48, 60, 66, 70, 75, 80, 82, 86-87, 90, 9699, 109, 111, 119 Adhesion, 109 Aluminium, 21, 26, 35, 47, 63, 70, 79-80, 83 American Society for Testing of Materials, 13-16, 18, 20, 23-24, 26, 28, 31, 33, 37-39, 41-42, 48-49, 53, 55-56, 59, 62, 64, 66, 70, 73, 106, 111, 123 Aramid, 77 Arc resistance, 131

B British Standard, 13, 53, 56, 62, 66

abcd

C

a b c d Carbon black, 63 Carbon dioxide, 3, 16, 20, 31-33, 35, 51-52, 72, 80, 88, 94, 110, 115, 117-119 Carbon fibre, 90 abcd Carbon nanotubes, 75, 112 a Chlorosulfonated polyethylene, 87 Classification, 15, 45-47, 49-50, 54, 59 α฀β฀χ฀δ Coatings, 77, 111 Compression, 61, 72, 118 ❁ Copolymerisation, 36, 113 Curing, 86-87, 95-96

D Density, 12-13, 15-17, 28, 30, 33, 37-38, 48-49, 54-55, 60, 66, 72-73, 81, 99 Derivatives, 5, 8, 29, 80, 86, 119

155

Characteristics and Analysis of Non-Flammable Polymers Diallyl phthalate, 131 Dielectric, 101, 129, 131 Differential scanning calorimetry, 96 Diffusion, 6, 48, 86, 110 Dimensional stability, 61 Dissipation, 101, 129, 131 Draw, 14 Dynamic, 87, 95-96 mechanical thermal analysis, 96

E Elastomers, 14-15, 17, 37, 60-61 Electrical, 21, 37, 47, 59-65, 67, 99, 101, 109, 125, 129, 131 Electron, 18, 20 Elongation at break, 131 Epoxy resin, 77, 79 Ethylene vinyl acetate, 111, 113-114 copolymer, 59, 114 Expansion coefficient, 131 Exposure, 12, 25, 45-46, 59-60, 69

F Filler, 18, 77, 109, 115, 118, 125-126, 128-130 Fire test, 27, 40, 47, 51-52 Flame resistance, 13, 54, 77, 86 Flame retardancy, 42, 60, 63, 76-77, 79, 82, 86-88, 90-92, 95, 106, 109, 112, 118, 120, 123 Flame retardant, 1, 6, 9, 18-20, 30, 34, 47, 53, 59-60, 63, 69-70, 75-80, 82-83, 87-88, 90, 92, 95, 98-101, 106, 114, 119 Flammability, 12-15, 17-18, 21, 30-33, 36-37, 47-48, 50-53, 55, 57, 60-64, 66, 70, 73, 75-77, 79-81, 83, 85-87, 89-91, 93, 95-99, 101-103, 105-107, 109, 111113, 115, 120-123, 125-126 Flexibility, 77 Flexural Modulus, 131

G Gas chromatography, 28-30, 33, 76, 80, 95 mass spectrometry, 76 Gaskets, 14, 37 Glass, 18-26, 29, 41, 48-49, 54, 63, 70-71, 77, 81, 86, 88, 90, 124-131

156

Index fibre, 19-20, 22, 29, 70, 77, 86, 90, 125-126, 130-131 transition temperature, 86, 96

H Hardness, 62 Heat, 1-5, 8, 11, 13-15, 18, 20-27, 30-32, 34-35, 37, 39, 41, 46, 48, 50-52, 56, 59-61, 64, 66, 70, 72, 75-76, 83, 86-87, 90-92, 109-112, 114, 123-124, 130131 High-density polyethylene, 28, 99 Hydrogen chloride, 6-8, 16, 31, 33, 72 Hydrolysis, 8

I Impact, 12, 65, 76-77, 87, 128, 131 Infrared, 77 Injection, 8, 10, 19, 53 moulding, 8 Inorganic, 48, 83, 88 International Organization of Standards, 13, 28, 41, 46, 53-56, 59, 69, 72-73, 81, 104, 119, 124

K Kevlar, 77

L Lamination, 69 Limiting oxygen index(s), 18-20, 36, 75-79, 81-83, 86, 89-90, 92, 95-96, 98-99, 112-115, 118, 125-127 Linear low-density polyethylene, 30 Loss factor, 96 Loss Modulus, 96 Low-density polyethylene, 30, 99

M Mass spectrometric thermal analysis, 36, 113-114 Mass spectrometry, 28-31, 35-36, 76, 80, 95 Materials, 4, 8, 12-18, 20-21, 27-28, 30-31, 37-41, 45-51, 53-57, 59-61, 64-66, 69-70, 72-73, 81, 86-89, 91, 95, 102-103, 105-106, 109-110, 112, 114, 118123 Melt, 53-54, 61, 111

157

Characteristics and Analysis of Non-Flammable Polymers flow index, 61 viscosity, 111 Methyl methacrylate, 35-36, 113-114 Modulus, 96, 100, 128, 131 Molecular weight, 28-30, 35, 88

N Nanotechnology, 112, 121 Natural rubber, 28 Neoprene, 61 Nuclear magnetic resonance, 18, 20 Nylon, 28

O Orientation, 23 Oxidative, 3, 34, 75 Oxygen, 1-2, 4, 6, 12-14, 17-18, 20, 27, 30-31, 37, 39, 47, 50-52, 56, 60, 70, 75, 77, 80-82, 89, 97-101, 104, 106, 110, 112-114, 123, 127 index test, 12, 14, 18 Ozone, 87

P Phenol-formaldehyde, 99 Polyamide(s), 18-21, 28, 59-60, 63, 90-91, 97, 100-101, 111-115, 123, 125, 127131 imide, 100-101 Polyarylates, 76 Polycarbonate, 29, 31, 63, 75, 80, 82, 84-86, 89, 97, 125-127, 129-130 Polydimethylsiloxane(s), 28, 95, 119 Polyester, 1, 4, 29, 49, 54, 63, 70-71, 79, 81, 83, 97, 126 Polyether ether ketone, 31, 100 Polyetherimide, 98, 100 Polyethylene, 28-31, 63, 69, 75-76, 80, 87, 99, 109, 112, 127 terephthalate, 76, 80, 183, 97, 125-127 Polyimide, 31, 63, 98, 100-101 Polymeric, 3, 41, 64, 79, 91, 102, 105-106, 109, 111, 119-120, 123 Polymethyl methacrylate, 35-36, 80, 83, 99, 113 Polyolefins, 21, 75, 113 Polyphenylene ether, 63 Polyphenylene oxide, 125

158

Index Polypropylene, 20-21, 28, 35, 47, 53, 63, 75, 88, 97, 109, 111-113, 120, 122, 128, 130-131 Polystyrene, 27, 47, 63, 76, 113, 131 Polytetrafluoroethylene, 76, 98, 100-101, 126-127 Polyurethane(s), 20, 28-29, 33, 35, 47-48, 53, 57, 61, 73, 88-91, 97, 99, 105, 115, 118-119 Polyvinyl chloride, 47, 63, 87-88, 98-101 Polyvinyl fluoride, 98, 100-101 Polyvinylidene fluoride, 98, 100 Processing, 6, 9, 61, 81, 105, 109, 120 Production, 4, 12, 15-16, 21, 23-25, 27, 41, 47-48, 50, 55-56, 79, 88, 90-91, 109, 124 Pyrolysis, 1-4, 6, 28-30, 33-36, 42-43, 76, 80, 82, 84-85, 87-88, 90, 92, 95, 113114 gas chromatography, 29-30, 76, 80, 95 mass spectrometry, 29-31, 76, 80, 88, 95

Q Quality control, 12

R Reinforcing agent, 125 Relative humidity, 15 Resin transfer moulding, 25

S Shrinkage, 130 Solution, 109 Sorption, 91 Specific heat, 5 Stability, 7, 10, 38-40, 42-43, 48, 61, 71, 73, 77, 83, 86-87, 89-91, 93-94, 96, 102-105, 107, 111, 113, 116-117, 119-124 Stiffness, 86 Strain at yield, 131 Styrene-acrylonitrile, 99, 127 Styrene-butadiene, 115

T Temperature, 2-4, 11-12, 15, 18, 25, 29, 31, 33, 36, 38, 46, 48-49, 52, 59-61, 75, 80-82, 86-87, 89-92, 94, 104, 106, 114-115, 130-131

159

Characteristics and Analysis of Non-Flammable Polymers Tensile strength, 47, 131 Thermal analysis, 8, 30, 36, 77, 96, 113-114, 121 Thermal conductivity, 5, 12, 112, 115, 118 Thermal degradation, 29-30, 77, 80, 106 Thermal stability, 77, 86, 91, 119 Thermogravimetric analysis, 13, 20, 31, 36, 76-77, 83, 92 Thermooxidative, 87 Thermoplastics, 109 Thermosets, 79 Thickness, 3, 17, 27, 69, 71, 81 Tracking resistance, 131

U Ultraviolet, 30, 61, 76-77, 92 Unplasticised polyvinyl chloride, 98, 101

V Viscosity, 19, 111

W Water, 8, 20, 25, 35, 42, 46, 80, 109 Wetting agent, 70

160

Published by Smithers Rapra Technology Ltd, 2013

Non-flammable polymers are polymers that are resistant to degradation and burning at high temperatures. In recent years there has been an increasing demand for fire retardant versions of a range of plastics. These types of polymers are particularly important in areas where there are enclosed spaces such as in skyscrapers, boats, trains and aeroplanes. Non-flammable polymers are also found in adhesives, electronic insulation and in military applications such as canvas tents and in domestic applications such as furniture, clothes, bedding, upholstery and electrical goods. This book discusses the mechanisms of fire-retardancy and how it can be achieved in polymers. There is extensive coverage of the applications and uses of fire-retardant polymers. There are also three Appendices, which give listings of all the Standards relevant to fire-retardancy of polymers. This book will be of interest not only to those working in the production of fire-retardant polymers but also to design engineers and producers in the polymer fabrication industries.

Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK Telephone: +44 (0)1939 250383 Fax: +44 (0)1939 251118 Web: www.polymer-books.com