Influence of Gas Phase Flame Retardants on Fire Toxicity

Transcription

1 Influence of Gas Phase Flame Retardants on Fire Toxicity Richard Hull 1

2 Fire Retardants Gas Phase Condensed Phase Flame Inhibitors e.g. Halogens, Phosphorus Diluents e.g. metal hydroxides, metal carbonates Heat Dissipation and absorption Barrier Formation Drip promoters (depolymerisation agents Char Inorganic Residues Intumescents Char promoters Carbon nanotubes? Acid + Blowing Agent + Carboniser Metal hydroxides + carbonates Nanoparticles Ionomer à calcium silicate (Casico) 2

3 Drivers in Fire Retardant development Decade Event Demand 1960s Widespread availability of cheap polymer products more serious fires Reduced ignitability 1970s Smoke much worse (PU foam furniture and halogenated flame retardants) Reduced smoke s Development of Cone Calorimeter Reduced Peak Heat Release Increase in deaths from smoke inhalation Reduced Fire Toxicity 2000s Halogen FRs found across the ecosystem Halogen-free FRs 2010s Climate change and other environmental concerns become mainstream Sustainable FRs 3

4 Potential toxic hazards from fire retardants 1. Fire retardant is toxic when it separates from the polymer (e.g. certain halogenated flame retardants) 2. Fire retardant (or its decomposition products) are toxic when released during a fire (e.g. certain organophosphates and halogenated dioxins) 3. Fire retardant increases the toxicity of the fire effluent (e.g. more CO or HCN) 4

5 1. Brominated Flame Retardants considered toxic Name Abbreviation Problems Action X m X n Polychlorobiphenyls PCB High toxicity Banned 1960s O Polybromobiphenyls PBB High toxicity (Michigan) Banned 1970s Br m Br n Pentabromodiphenylether PentaBDE High toxicity Banned 1990s Octabromodiphenylether OctaBDE High toxicity Banned 1990s Br Br Br Br Br Decabromodiphenylether DecaBDE PBT Voluntary withdrawal tris-1,3-dichloropropyl phosphate TDCPP Mutagenic, carcinogenic Banned for high risk applications Hexabromocyclododecane HBCD PBT Listed by Stockholm Convention Br 5

6 2. Trimethylol propane phosphate, and other bicyclic phosphate esters TMPP LD 50 /mg/kg >500 6

7 3. Fire Toxicity Fire toxicity depends on both material and fire condition For flammability, the worst case is well-ventilated For fire toxicity, the worst case is under-ventilated 7

8 UK Fire Deaths ( ) Unspecified Other Burns Burns/smoke Smoke No of deaths

9 No of hospital admissions UK Fire Injuries ( ) Burns Unspecified Other Shock only Physical Injuries Burns and overcome by gas or smoke Overcome by gas or smoke

10 Fire Retardants Gas Phase Condensed Phase Flame Inhibitors e.g. Halogens, Phosphorus Diluents e.g. metal hydroxides, metal carbonates Heat Dissipation and absorption Barrier Formation Drip promoters (depolymerisation agents Char Inorganic Residues Intumescents Char promoters Carbon nanotubes? Acid + Blowing Agent + Carboniser Metal hydroxides + carbonates Nanoparticles Ionomer à calcium silicate (Casico) 10

11 Key applications requiring gas phase FR Usually the most difficult materials to fire retard! Generally, low thermal inertia (kρc) materials, with high surface area! eg; Foams, fibres and films Particularly, textiles, flexible polyurethane foam (furnishings), polystyrene and rigid polyurethane foam insulation. 11

12 CO formation and destruction in a methane flame H + H 2 O D H 2 + OH CO 2 H H 2 O H + O 2 O + H 2 H 2 O + O D OH + O D OH + H D OH + OH HCHO + OH D HCO + H 2 O HCO + OH D CO + H 2 O CH 3 + O 2 D HCHO + OH CO OH H 2 CH 4 + OH D CH 3 + H 2 O CH 4 + H D CH 3 + H 2 CH 4 + O D CH 3 + OH CO + OH D CO 2 + H 12

13 Free Radical Reactions of HCN in a Flame NO NCO CN HCN CO O H OH H 2 O OH H + O 2 D OH + O O + H 2 D OH + H H 2 O + O D OH + OH HCN + OH D CN + H 2 O CN + OH D NCO + H CN + O 2 D NCO + O NCO + O D NO + CO NCO + NO D N 2 O + CO NCO + NO D N 2 + CO 2 HCN + OH D HOCN + H HCN + OH D HNCO + H 13

14 Halogen Flame Retardant Action ArX Ar + X where X is either Cl or Br. X reacts with fuel to form HX : X + ArH Ar + HX HX + H H 2 + X and HX + OH H 2 O + X Removal of the H and OH reduces the major heat release step: CO + OH CO 2 + H 14

15 PET (GRP) with Cl and Br FRs 3.0 CO Hypoxia HCl HBr Organic 2.0 FED Oxidative Pyrolysis Well-V Small UV Large UV 15

16 Cable Materials 2.0 CO HCl Hypoxia Oxidative Pyrolysis Well-V Large-UV Oxidative Pyrolysis Well-V Large-UV Oxidative Pyrolysis Well-V Large-UV Oxidative Pyrolysis Well-V Large-UV Oxidative Pyrolysis Well-V Large-UV Oxidative Pyrolysis Well-V Large-UV Oxidative Pyrolysis Well-V Large-UV Oxidative Pyrolysis Well-V Large-UV Oxidative Pyrolysis Well-V Large-UV Oxidative Pyrolysis Well-V Large-UV FED Halogen Free Data Cable PVC Data Cables Halogen Free Power Cables PVC Power Cables PVC Single Conductor Cable 16

17 Fire Toxicity Comparison (20 g/m 3 ) S Molyneux, A A Stec, T R Hull The effect of gas phase flame retardants on fire effluent toxicity Polymer Degradation and Stability 106 (2014)

18 R.J.Crewe, A.A.Stec, R.G.Walker, J.E.A.Shaw, Prof Richard T.R.Hull, Hull J.Rhodes September and T. 25, Garcia-Sorribes, 2014 Experimental Results of a Residential House Fire Test on Tenability: Temperature, Smoke and Gas Analyses, 18 Journal of Forensic Sci. 59, , 2014.

19 UK Fire Retardant sofa Ignition source 4 sheets newspaper 19

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21 UK FR sofa, after ignition by 4 sheets newspaper! 21

22 CO and HCN concentrations in house 22

23 Conclusions Fire toxicity continues to be the major killer in fires Halogenated flame retardants may suppress ignition, but they also increase the fire toxicity Toxic fumes from furniture and bedding probably cause most fire deaths. Currently only the ignitability, and not the toxicity of furniture is assessed. Our tests showed that used UK furniture can be consistently ignited using 4 sheets of newspaper. 23

24 Thank you for listening! Thanks to the team at UCLan, especially Dr Anna Stec and various students who did all the work! Questions? 24