Perfluoroalkyl Iodides and Other New-Generation Halon Replacements

These now comprise two major areas: the ... Studies have been conducted by both the Air Force ... Testing by the U.S. Air Force at Tyndall Air Force B...
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Chapter 14

Perfluoroalkyl Iodides and Other New-Generation Halon Replacements 1

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Downloaded by NORTH CAROLINA STATE UNIV on October 6, 2012 | http://pubs.acs.org Publication Date: May 5, 1997 | doi: 10.1021/bk-1995-0611.ch014

Robert E . Tapscott , Stephanie R. Skaggs , and Douglas Dierdorf 1

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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

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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

Downloaded by NORTH CAROLINA STATE UNIV on October 6, 2012 | http://pubs.acs.org Publication Date: May 5, 1997 | doi: 10.1021/bk-1995-0611.ch014

Property

Target

Ozone Depletion Potential