Chapter 14
Perfluoroalkyl Iodides and Other New-Generation Halon Replacements 1
1,3
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Robert E . Tapscott , Stephanie R. Skaggs , and Douglas Dierdorf 1
2
Center for Global Environmental Technologies, New Mexico Engineering Research Institute, University of New Mexico, Albuquerque,NM87131 H T L / K I N - T E C H Division, Pacific Scientific, 3916 Juan Tabo, Northeast, Albuquerque, NM 87111
2
New-generation halon substitute candidates can be divided into two groups: tropodegradable replacements, highly efficient halocarbons with short atmospheric lifetimes, and advanced agents, non -halocarbons. At present, the most promising tropodegradable replacements are the iodides, which exhibit fire extinguishment capabilities similar to the halons. Among the advanced agents, the phosphonitriles have been shown to be superior to halons in laboratory-scale extinguishment tests. To date, across a broad range of applications, no Halon 1301 substitute has been proven to provide total-flood protection against fires and explosions in normally occupied areas without major changes in system hardware. Moreover, few halon substitutes have been found that are as effective as Halon 1211 for streaming (e.g., portables). Much of the work to date has focused on first-generation halon replacements (7). For the most part, first-generation agents are the three families of halocarbons — hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs or FCs). No chemicals within these families have an effectiveness equal to that of Halon 1301 or Halon 1211, except for very specialized scenarios. Moreover, many, if not all of these materials have some environmental drawbacks. HCFCs cause some ozone depletion, and PFCs (and to a lesser extent, HFCs) cause global warming (Table I). The HCFCs and PFCs are already facing some regulatory actions due to their perceived environmental impact. It is extremely unlikely that any environmentally acceptable first-generation agent with an effectiveness equal to that of the existing halons will be found. There is, therefore, an increasing interest in materials other than the first-generation materials as halon substitutes. These now comprise two major areas: the tropodegradable halocarbons (2) and advanced agents (3). 3
Current address: HTL/KIN-TECH Division, Pacific Scientific, 3916 Juan Tabo, Northeast, Albuquerque, NM 87111 0097-6156/95/0611-0151$12.00/0 © 1995 American Chemical Society In Halon Replacements; Miziolek, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1997.
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HALON REPLACEMENTS
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Table I. Relative Properties of Halocarbon Families* Halocarbon Family
Fire Exting. Ozone Global Ability Depletion Warming
Toxicity
perfluorocarbons PFCs (FCs)
moderate
nil
very high, atmospheric lifetimes around 3000 years
very low
hydrofluorocarbons HFCs
moderate
ml
high, lifetimes tens to hundreds of years
low to moderate, some cardiac sensitization
chlorofluorocarbons CFCs
moderate
Class I ODSs
high
low to moderate, some cardiac sensitization
hydrochlorofluoro carbons HCFCs
moderate
Class II ODSs
low to moderate, short atmospheric lifetimes
low to moderate, some cardiac sensitization
bromofluorocarbons BFCs
excellent
Class I ODSs, production ban
moderate to high
low to high, some cardiac sensitization
hydrobromofluoro carbons HBFCs
excellent
Class II ODSs
low to moderate, short atmospheric lifetimes
moderate to high
fluoroiodocarbons FICs
excellent
low, near zero
very low, atmospheric lifetimes of days
moderate to high, significant cardiac sensitization
*Fire extinguishment abilities are a summarization of data from a variety of sources, in particular from Reference 4, which contains cup burner data for 53 compounds. Sources for assessment of relative ozone depletion, global warming, and toxicity include the U.S. E P A Significant New Alternatives Program (SNAP) assessment (5) and reports of the Intergovernmental Panel on Climate Change (IPCC). Reference 6.
In Halon Replacements; Miziolek, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1997.
14. TAPSCOTT ET AL.
Perfluoroalkyl Iodides as Halon Replacements
A target specification for an ideal halon replacement can be refined to that summarized in Table II. Table II. Idealized Specification For Halon Replacements
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Property
Target
Ozone Depletion Potential
