Fluoroethers and Other
`Next-Generation Fluids
`
`Donald B. Bivens, Ph.D.
`Member ASHRAE
`
`Barbara H. Minor
`
`ABSTRACT
`
`and a summary of findings for toxicity, stability, atmo­
`spheric
`lifetimes, refrigeration performance, and
`Hydrofiuorocarbons (HFCs) have been predomi­
`
`manufacturing considerations. Each next-generation
`nantly chosen as the zero ozone depletion potential
`fluid mentioned in the text will be included in a master
`
`
`(ODP) alternatives for chlorofiuorocarbon (CFC) refrig­
`table of compounds (Table 1). References for each fluid
`erants. Since there might be other types of zero ODP
`and property value are included in the table.
`
`compounds more preferable than HFCs as working
`
`
`fiuids, several organizations have investigated fluori­
`BEFORE THE MONTREAL PROTOCOL
`nated ethers, alcohols, amines, silicon, and sulfur
`The earliest patent for fluorinated ethers as refrig­
`compounds. Evaluation criteria included toxicity,
`erants was issued to Booth ( 193 7), claiming halogenated
`
`
`
`
`nonfiammability, stability, atmosphe1ic lifetime, refrig­
`methyl ether compounds in general and specifically
`
`
`eration performance, and manufacturing feasibility
`
`and 142aE CCHClFOCH2F), 143E (CHF20CH2F),
`
`
`and cost. Although a few of the compounds have
`133aE (CF30CC1H2).
`
`
`predicted refrigeration performance close to HFCs, at
`
`this stage of the evaluations none appears to have a
`Eiseman {1968) received a patent on a process for
`
`
`to challenge balance of refrigerant fluid requirements
`refrigeration with fluorinated ethers having the
`HFCs.
`formula CF30CnHmF(zn-m+l)
`where n = 1-2 and m = 1-
`3. These compounds had a relatively higher heat of
`vaporization compared to commercial refrigerants
`such as R-12 (a CFC), R-23 (an HFC), and R-22 (an
`HCFC) and compared to perfluorinated ethers such as
`116E (CF 30CF 3). Compounds mentioned in the claims
`were 143aE (CF30CH3), 227eaE {CF30CHFCF3),
`
`236faE (CF30CH2CF3), 125E (CF30CHF2), and
`227caEaj3 (CF30CF2CHF2).
`Simons et al. (1977) received a patent in 1977 on
`aerosol applications of 134E (CHF20CHF2), 116E, and
`125E. In the patent text was information on biological
`testing of these compounds, concluding that 134E and
`116E had less biological activity than 125E.
`Powell (1985) received a patent with allowed
`claims for a high-temperature heat pump operating
`with hydrofluorocarbon R-245ca (CHF2CF2CHzF),
`
`254cbEj3y(CHF2CF20CH3), or fluoroamines ofseveral
`different formulae. One fluoroamine claimed was trif­
`luoroethylamine, NH2(CH2CF3). Powell's objective
`
`
`INTRODUCTION
`
`Hydrofluorocarbons (HFCs) have been chosen as
`the zero ozone depletion potential (ODP) altematives
`for chlorofluorocarbon (CFC) refrigerants; however,
`there are several reasons to continue searching for
`other types of zero ODP compounds as working fluids:
`other compounds might have better refrigeration
`performance, lower atmospheric lifetimes, or lower
`manufacturing cost or some toxicity problem might
`have been discovered during testing of HFCs. These
`HFC alternative fluids have been termed "next-gener­
`ation fluids" beyond HFCs
`The fluids of this investigation have some fluorine
`
`content, as fluorine atoms impart characteristics of
`stability and nonflammability. Fluorinated ethers,
`alcohols, amines, silicon, and sulfur compounds were
`investigated. The following sections will include a liter­
`ature review, description and listing ofthe compounds,
`
`Donald B. Bivens is an engineering fellow and Barbara H. Minor is a research
`in the Fluoroproducts Business
`associate
`Unit of E. I. DuPont de Nemours & Company, Wilmington,
`Del.
`
`122
`
`ASHRAE/NIST Refdgerants Conference-October 1997
`
`Page 1 of 8
`
`Arkema Exhibit 1132
`
`

`
`was to provide stable fluids for heat pumps operating at
`high output temperatures.
`The chlorofluorocarbon/ozone controversy began to
`receive more attention at this time, evidenced by the
`Vienna Convention for the Protection of the Ozone
`Layer fmalized and adopted in March 1985 (UNEP
`1985). Multinational discussions continued after the
`Vienna Convention, culminating in the signing of the
`Montreal Protocol in September 1987. The agreement
`limited production of specified chlorofluorocarbons
`(UNEP 1987).
`Chlorofluorocarbon alternatives were researched
`in the mid-1970s after publication of Molina and
`Rowland's 1974 paper on ozone layer depletion poten­
`tial by chlorofluorocarbons. Great effort was expended
`trying to validate the theory, and the only significant
`impact on CFCs was banning their use in ''nonessen­
`tial" aerosols in 1978 (Federal Register 1978) by the
`United States, followed by similar actions in Sweden,
`Norway, and Canada.
`The 1985 Vienna Convention signaled renewed
`ozone depletion concern, and some researchers in
`industry, academic, and governmental laboratories
`quietly began reconsideration of CFC alternatives.
`One example(Smith 1992) was the United States Envi­
`ronmental Protection Agency {EPA) convening a group
`of experts in the spring of 1987 to assess the potential
`for finding suitable CFC alternatives. Recommenda­
`tions included back-up replacements if the primary
`candidates were deemed unacceptable (Bare 1993).
`
`AFTER THE MONTREAL PROTOCOL
`Research into CFC alternatives became more
`active after the Montreal Protocol was signed in 1987
`and even more emphasized after publication of data on
`ozone layer thinning in 1988 (New York Times 1988).
`The need to consider a wide range of alternatives
`including fluorinated ethers was expressed at the 1988
`Workshop on Property Data Needs for Ozone-Safe
`Refrigerants at the National Institute of Standards
`and Technology in Gaithersburg, Maryland (Hill
`1988). Accordingly, the scope of worldwide alternatives
`research included HCFC and HFC compounds and also
`other compounds, such as fluorinated ethers, alcohols,
`amines, sulfur- and silicon-containing compounds,
`hydrocarbons, ammonia, and carbon dioxide. The crite­
`ria of toxicity and nonflammability limited the appli­
`cation possibilities for hydrocarbons and ammonia.
`In 1988 the EPA and EPRI funded a project with
`two universities to synthesize fluorinated propanes,
`butanes, and ethers, which might be CFC alternatives
`(Smith 1992). Of 34 compmmds synthesized, 11 were
`the fluorinated ethers: 116E, 125E, 134E, 143E,
`(CF30CF2CHF2),
`143aE,
`227caEap
`218E2
`(CF30CF20CF3),
`(cyclo-CF2CF20CF2-},
`c216E
`
`c225eEafl (cyclo-CHFCF20CF2-}, c2&4fEap {cyclo­
`CH2CF20CFd, and c216E2 (cyclo-CF20CF20CF2-).
`Two of these ethers were selected for further study:
`143aE as a replacement for R-12 and 125E as a
`replacement for R-115.
`William L. Kopko presented a paper at the 1989
`American Society of Heating, Refrigerating and Air­
`Conditioning Engineers (ASHRAE) CFC Technology
`Conference at Gaithersburg, Maryland (Kopko 1989),
`in which he suggested several fluorinated ethers be
`investigated as CFC refrigerant alternatives: 134E as
`a substitute for R-114, 123bE (CHF20CFC12) as a
`substitute for R-113, and 143E as a substitute for R-11.
`Vineyard and Sand of ORNL and Statt of the U.S.
`Department of Energy (DOE) in 1989 compiled an
`extensive
`list of potential
`refrigerant mixture
`compounds and properties (Vineyard et al. 1989),
`including the fluorinated ethers 116E, 125E, 143aE,
`218E (CF30CF2CF3), 227eaE (CF30CHFCF3), 134E,
`236faE
`{CF30CH2CF3), 143E, 227caEafl,
`and
`254cbEap (CHF20CF2CH3).
`
`PATENT ACTIVITY
`Research on CFC alternatives beyond HFCs and
`HCFCs was under way by refrigerant manufacturers
`in the late 1980s as evidenced by patent activity that
`became public information. O'Neill and Holdsworth
`{1990) received a patent on 134E as a refrigerant on
`October 9, 1990; the patent filing date was February
`28, 1989. Fellows et al. (1990) received a patent on a
`mixture of R-22 and 125E on August 14, 1990; the
`patent had been filed on September 26, 1989. Several
`patent applications had the priority date of September
`6, 1989 {Omure et al. 1991a, 1991b, 1991c, 1991d,
`l991e), for fluorinated ethers, amines, and sulfur­
`containing compounds as refrigerants. Compounds
`included were 116E, 125E, CF3SF5, C2F5NF2, and
`(CF3)2NF. Omure's company continued with patent
`applications having priority dates of August 30, 1990
`{Teraoka et al. 1992) and August 31, 1990 (Hara et al.
`1992; Inagaki et al. 1992) for additional CFC alterna­
`tives. These
`included CH3-N::CH2, CF2{NF)2,
`CHF2NF2, F2S::O, FSSF, CF3SH, CH3SiH2F, a series
`of C2-C4 fluoroethers, and a series of C2-C4 sulfur­
`containing compounds. Graphs of energy efficiency and
`capacity for these compounds vs. R-12, R-22, and R-502
`were presented. Adcock (1993) received a patent on
`fluorinated oxetanes having the structures cyclo­
`CF2CFHCF2-0- and cyclo-CF2CH2CF2-0-; his Ui:dted
`States filing date was December 9, 1991. Patron and
`Sievert (1995) received a patent on two fluorinated
`ethers as refrigerants: 236caE and 236eaEfly having
`boiling points of 28SC and 23.2°C. Their filing date
`was January 25, 1993. There have been additional
`patents granted for refrigerant mixtures containing
`
`ASHRAEINIST Refrigerants Conference-October 1997
`
`123
`
`Page 2 of 8
`
`

`
`fluorinated ethers and other fluorinated corripounds,
`and a selected few can be reviewed in Klug et al. (1997);
`and Powell et al. (1994).
`
`RESEARCH INSTITUTE OF INNOVATIVE
`TECHNOLOGY FOR THE EARTH
`
`The Japanese government provided money in 1990
`for a five-year program targeted at fluorinated
`compounds containing oxygen, nitrogen, or silicon
`under the name Development of Advanced Refriger­
`ants for Compression Heat Pumps (Sekiya and Misaki
`1996). The money was administered by the New
`Energy Development Organization (NEDO), and the
`project was assigned to the Research Institute oflnno­
`vative Technology for the Earth (RITE). There was
`additional cooperative research with the National
`Institute of Materials and Chemicals Research
`(NIMC), Ten Japanese companies provided their
`personnel for research on this project at RITE. The
`project had many activities, including initial research
`for compound selection, synthesis, measurement of
`properties, evaluation of safety and environmental
`impact, and overall assessment of suitability.
`About 500 compounds were considered, with 70
`being synthesized for additional property characteriza­
`tion (Sekiya and Misaki 1996). A partial listing of the
`compounds being studied was provided by Suga (1993),
`which included 16 fluorinated alcohols and 28 fluori­
`nated ethers. Only one of the fluorinated alcohols had
`a boiling point low enough to be considered for a refrig­
`erant application. This was (CF3)3COH, having a boil­
`ing point of 45GC and being a potential replacement for
`R-113 (48"C boiling point). The 28 fluorinated ethers
`were all three-carbon linear compounds. The purpos·e
`of the listing was to illustrate the effect of molecular
`structure (location and number of hydrogen and fluo­
`rine atoms) on estimated atmospheric lifetimes.
`Selected targeted compounds by RITE were
`reported by Misaki and Sekiya (1994). The article
`included 19 fluorinated ethers, five fluorinated
`compounds containing nitrogen, and five containing
`silicon. These compounds are listed in Table 1. All of
`the fluorinated ethers were of three or four carbon
`chain length. Initial data on toxicity, flammability, and
`atmospheric lifetimes were provided (see Table 1).
`Three fluorinated ether compounds targeted by
`RITE were described by Misaki and Sekiya (1995).
`These were 245cbEj3y
`(CF3CF20CH3), 347sEyo
`(CF3CF2CF20CH3), and 34 7mmyEj3y ((CF3)2CFOCH3,
`having boiling points of 5.6°C, 34.2"C, and 29.4"C,
`respectively. Atmospheric lifetimes were five to six
`years for all three compounds. The paper had data on
`thermophysical properties, thermal stability, flamma­
`bility, toxicity, and atmospheric lifetime of the
`compounds. Some of these data are in Table 1. Patent
`
`applications for these compounds were filed in Japan in
`March 1995 (Ito et al. 1996; Nagasaki et al. 1996; Suga
`et al. 1996).
`As reported in two different publications (Sekiya
`and Misaki 1996; Misaki and Sekiya 1996), these three
`compounds have been selected for further study of
`toxicity, practical application tests, and improved
`synthesis procedures.
`As an observation by the authors of this paper,
`the Japanese project was an impressive cooperative
`effort of researchers from many different companies
`and academic and governmental laboratories. In
`addition to the three compounds selected for further
`study as low environmental impact refrigerants,
`basic know ledge of molecular structure effects on
`properties was developed during
`the five-year
`research project. This knowledge will be useful in
`studies of future refrigerants.
`
`·
`
`INVEST IGATIONS FOR REFRIGERANT
`SUITABILITY-TOXICITY
`
`Toxicity data in Table 1 have been taken from liter­
`ature s ources and from acute toxicity testing of selected
`fluorinated compounds. References for data sources
`are shown in parentheses for each compound. The
`"approximate lethal concentration" (ALC) is the expo
`sure level at which deaths occur in a group of rats.
`NOEL is a "no observed effect level." A convulsant is
`d.efmed as a central nervous system (CNS) stimulant
`usually observed as tremors. An anesthetic is defmed
`as "CNS depression," observed as weakness, lethargy,
`dizziness, and/or sleepiness.
`Data show there is wide variation in the toxicity of
`alternatives. Some have very low toxicity, such as
`236eaE,By, which has been extensively tested and is a
`commercial anesthetic. Some compounds, such as
`143aE, 347mfcEaj), and 356mffE,By, have a high degree
`of acute toxicity. Different isomers, such as the 347
`series fluoroethers, have varying toxicity. Although
`there are data from Simons et al. (1977) indicating
`some concern about 125E biological effects, more
`recent data indicates >100,000 ppm ALC (Haskell
`1992-1996). The fluorosulphides tested showed low
`acute toxicity; however, these compounds were fully
`fluorinated. It is expected that the reactive fluorinated
`sulfur compounds F 28==0 and FSSF would have toxic
`effects. There are very little toxicity data on the fluoro­
`amine compounds,
`Any promising next-generation refrigerant must
`undergo extensive toxicity testing. Future toxicity
`screening costs could possibly be reduced if more infor­
`mation were available on toxicity of functional groups
`present in the fluorinated ethers, amines, silicon, and
`sulfur compounds.
`
`124
`
`ASHRAE/NIST Refrigerants Conference-October 1997
`
`Page 3 of 8
`
`

`
`and can require sample quantities
`that are not always
`INVESTIGATIONS FOR REFRIGERANT
`available.
`SUIT ABILITY-THERMAL STABILITY
`Thermal stability is a critical factor in determining
`
`Cooper and Cunningham (1992, 1993) used empir­
`
`ical structure-activity relationships to estimate tropo­
`Data from the liter­
`
`viability of a refrigerant.
`long-term
`spheric lifetimes of HFCs and fluorinated ethers
`ature and from tests (DuPont 1992-1996) are included
`containing two and three carbon atoms. As expected,
`
`in Table 1. For the tests, 5g of refrigerant were placed
`
`
`they found shorter lifetimes as the number athydrogen
`in sealed tubes containing various combinations
`of
`The effect of inserting an oxygen into
`
`
`lubricant, copper, aluminum, and steel coupons. Tubes
`atoms increased.
`an HFC molecule usually was toward shorter
`were held at 175°C for two weeks, then checked for
`lifetimes,
`but not in all cases. Shorter lifetimes were calculated
`
`decomposition and metal attack. Stability tests also
`were run by RITE (Misaki and Sekiya 1994, 1996) at
`
`for molecules containing the structural units CH30-,
`CH2FO-, -CH20-, and -CHFO-. Fluorinated ethers that
`120°C and 175°C.
`
`did not contain at least one of those structural units
`According to O'Neill (1993), the stability of fluori­
`
`were predicted to have longer lifetimes
`
`nated ethers in contact with glass is unpredictable. He
`than the HFC
`counterparts. Two examples illustrate this: R-134/
`reported the following compounds unstable in glass:
`and
`CH2FOCH3 (161E), CHF20CH3 (152aE),
`134E and R-125/125E. The HFC molecular formulae
`are CHF2CHF2 and CHF2CF3, respectively. The four
`CHF20CH2F (143E). CHF20CHF2 (134E) was stable
`in glass after impurities such as 143E and 152aE were
`structural units previously mentioned will not be
`removed. O'Neill further reported that 134E reacts
`present in 134E or 125E; therefore, these fluoroethers
`
`could have longer lifetimes than their HFC counter­
`with polyglycol lubricants but not with polyolester
`lifetimes are
`
`parts. This is the case, as the tropospheric
`lubricants.
`for R-134 and 134E (Calm
`12 and 23 years respectively,
`Doerr et al. (1993) made an extensive study of
`1995) and 36 and 171 years for R-125 and 125E
`CF3CH20CHF2 (245faE,By), finding it to be thermally
`(DeMore 1994).
`
`stable in the presence of metals but reacting with glass
`to produce high pressures. The reaction was acceler­
`values are in Table 1. Few
`All available lifetime
`ated in the presence of oxygen or peroxides.
`data are available for the other classes of next-genera­
`Doerr speculated on stability of fluorinated ether
`tion compounds. RITE (Misaki and Sekiya 1994) esti­
`compounds, observing that perfluoroethers and totally
`mated lifetimes of0.1 to 3.1 years for four compounds
`
`halogenated ethers usually are stable and concluding
`
`containing nitrogen.
`
`with either all fluorines or
`that fluoroether molecules,
`all hydrogens on the carbon attached to the oxygen,
`
`should offer the greatest stability. This seems to be the
`case for the three fluoroethers selected by RITE
`(Misaki and Sekiya 1996) for future study:
`The flammability classification of a compound has .
`
`
`CF3CF20CH3, CF3CF2CF20CH3, and(CF3)2CFOCH3•
`a 'significant impact on its potential
`as a refrigerant.
`However, this generalization must be used with
`The United States organizations
`
`Underwriters Labo­
`
`- caution, as Sako et al. (1994) reported thermal decom­
`ratories and ASHRAE recently cooperated to clearly
`
`
`position ofCHF 2CF 20CH3 during lab oratory measure­
`define criteria for testing and flammability definition
`ments of critical properties. The presence of unstable
`
`of a refrigerant (Iracki 1997). This has included revi­
`impurities also could be a factor.
`sions to test procedure ASTM D-681 (1985). None of the
`Stability of the silicon, sulfur, and nitrogen­
`
`compounds in this review have been subjected to the
`containingcompounds in Table 1 is not as well defmed.
`new test procedure; however, some guidelines can be
`
`Generally, it is known that S-F and Si-H bonds can be
`
`used for initial screening of potential flammability.
`
`reactive (DuPont 1997), so refrigerant stability tests
`test data have shown the need
`Previous flammability
`must be run on any next-generation candidates having
`for substantially more fluorine on a molecule than
`these atoms.
`hydrogen for a compound to be nonflammable. The
`
`ratio F/(F+H) should be 0.67 0.70 or higher to ensure
`nonflammability. Flammability ratios are shown in
`Table 1. Molecules with ratios around 0.60 may or may
`
`not be flammable. Position of the fluorine and hydro­
`A major goal in studying next-generation alterna­
`
`gen on the molecule will have some effect on flamma­
`tives is to determine whether other types of non-ozone­
`bility. Fluorinated sulfur compounds were found to be
`
`depleting molecules could have lower tropospheric life­
`surprisingly flammable. The perfluorinated molecules
`times than HFCs and possibly less environmental
`CF3SCF3 and CF3CF2SCF2CF3 were flammable at
`
`impact. Unfortunately, obtaining experimental life­
`100°C in ASTM D-681 test apparatus.
`time values is difficult(Cooper and Cunningham 1992)
`
`INVESTIGATIONS FOR REFRIGERANT
`SUITABILITY-TROPOSPHERIC LIFETIME
`
`INVESTIGATIONS FOR REFRIGERANT
`SUITABILITY-FLAMMABILITY
`
`ASHRAE!NIST Refrigerants Conference-October 1997
`
`125
`
`Page 4 of 8
`
`

`
`INVESTIGATIONS FOR REFRIGERANT SUITABILTY­
`REFRIGERANT CYCLE PERFORMANCE
`
`1.1
`
`<t � 1.05
`
`u
`£ � 0.95
`·� Qi 0.9 ..
`a. 0 0.85
`u
`
`
`
`F
`-
`
`
`.236faE. ...
`
`___
`
`o.a
`0.9
`
`.
`..... .. ...
`
`-···
`
`-
`
`-----
`
`----------·
`
`•
`··-----
`
`
`
`
`
` - _1_3:-�---
` • •
` F3SCF2
` F56F2H
`
`-_ ... - ------
`
`22 caEbg
`-
`
` -----.-·-- ---
`21BE
`
`1.5 1,6
`1.1
`1.2 1.3 1.4
`Capacity relative to CFC-114
`Figm·e 3 Performance us. R-114.
`
`thermodynamic cycle
`Modeling refrigerant
`performance gives an indication of whether a next­
`generation refrigerant can provide similar effi­
`c iency and capacity compared to CFCs, HCFCs, or
`HFCs. Figures 1, 2, and 3 show calculated relative
`r efrigerant per formance fer potential nonflamma­
`b le al ter natives to R-22, R 134a, R-114, R-11, and
`R 123 at conditions of 130°F (54.4°C) condenser '
`45°F (7.2°C) evaporator, 10°F (5.56°C) subcooling,
`a nd 65°F (18.3oC) return gas temperature. An
`equation of state model was used to predict cycle
`p er formance, with model coefficients estimated
`based on compound structure and boiling point.
`The data points in Figures 1, 2, and 3 show the
`following:
`
`• Some of the potential R-11 alternatives for
`future study might be 236eaE,By, 347mmyE,By,
`and 347sEyo.
`• Perfluorinated molecules such as 218E 218E2
`c216E, c216E2, SF5CF3, and N(CF3)s p�rformed
`poorly.
`
`•
`
`•
`
`•
`
`0
`
`None of the alternatives matched performance
`for R 22 or R-134a.
`Three nitrogen-containing compounds had mod­
`RITE performance data (Misaki and Sekiya 1996)
`eled capacity values near R-22 and R-134a.
`were similar to estimates for347mmyEfiy and 347sEyo
`As boiling points and molecular size increase
`performance of alternative molecules is mor�
`in Figure 2 and for 245cbE/)y in Figure 3. Perlormance
`data also were comparable to data reported by De Votta
`comparable to existing refrigerants such as R-
`et al. (1993a) for 134E, 218E2, c216E, and N(CF 3)3, as
`114 and R-123, resulting in more potential
`well as 245caEaf3 (DeVotta et al. 1993b). Several
`alternatives.
`compounds, such as 143E, 143aE, 152E, CF3SCF 3, and
`Some of the potential R-114 alternatives for
`245faE,By were not included in the analysis due to toxic
`!ty, stability, or flammability concerns.
`future study might be 134E, 245cb:&5y, and sul­
`fur-containing compounds.
`
`MANUFACTURING AND COST CONSIDERATIONS
`
`Another critical factor in selecting a new alterna­
`tive is the practicality and cost of manufacturing on a
`large scale. Sekiya and Misaki
`(1996) described
`synthesis routes to several types of alternatives in their
`paper. In studying fluoroethers, fluoroamines, and
`fluorinated sulphur compounds, several difficulties,
`such as synthesis routes, reaction rates, and compound
`purity, were encountered in simply synthesizing small
`quantities of compounds. In most cases, candidates
`under consideration were larger, more complex mole­
`cules requiring multistep synthesis routes. Compound
`costs increase as the number of fluorine and carbon
`atoms increase, and the refrigerants industry has
`already seen this in manufacturing costs of HFCs .
`There can be additional costs for adding oxygen, nitro­
`gen, or sulphur atoms. As expected, initial manufac­
`turing cost estimates for selected next-generation
`alternatives show higher costs than HFCs.
`
`1.6
`
`·-·-
`
`
`1.4
`
`CONCLUSIONS
`
`1. Several potential next-generation alternatives
`have been identified for future study, with relatively
`more candidates being available for R-11 and R-114
`
`0.2
`
`Q.4
`
`1.02
`
`0.8
`0.6
`1.2
`Capacity relative to HCFC-22
`Figure 1 Performance us. R-22 and R-134a.
`.. --.... . -- ..
`· ·-- -- GFG H · ·
`· ··
`--·- .....
` ..... .
`- � I:!C.C
`-234fEbg
`. . -
`.
` • -
` .
`.
` .
` 236caE 1!.
`286�a .. b.!l._ .. _
`
`
`1.4
`
` -·· -
`
`·-·-
`
`
`
`.
`
` g
`
`• 34
`
`
`
` 5 •
`o.a
`1
`1.2
`Capacity relative to CFC-11
`Figure 2 Performance us. R-11 and R-123.
`
`o.a
`
`,. 1
`� 0.98
`(.) 0 0.96 ..
`� 0.94
`� � 0.92 ..
`g; 0.9
`(.) 0.68
`0.86
`o.4
`
`126
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`
`replacement stlidies than for R� 134a and R�22 replace­
`ment.
`2. An enonnous amount of effort and expense is
`required for identifying, synthesizing, and runing the
`many types of tests (stability, toxicity, tropospheric
`lifetime, properties, performance) to qualify a new
`refrigerant.
`3. At this point in the studies, none of the next�
`generation candidates appears to have a balance of
`refrigerant fluid performance, safety/environmental
`properties, and manufacturing feasibility/cost to chal­
`lenge HFCs.
`4. There are opportunities to add to our under�
`standing of fluorinated compound toxicity, stability,
`tropospheric lifetime, and flammability by relating
`these properties to molecular structure.
`
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