| HS Code | 340064 |
| Chemical Formula | C4F7N |
| Iupac Name | 2,3,3,3-tetrafluoro-2-(trifluoromethyl)propanenitrile |
| Cas Number | 42532-60-5 |
| Molecular Weight | 195.04 g/mol |
| Appearance | Colorless gas (liquefied compressed gas) |
| Boiling Point | -4.7 °C |
| Melting Point | -121 °C |
| Critical Temperature | 121 °C |
| Vapor Density Air 1 | 6.73 |
| Vapor Pressure 25 C | ~0.30 MPa |
| Solubility In Water | Sparingly soluble |
| Dielectric Strength Relative To Sf6 | 2.2 |
| Global Warming Potential 100 Year | 2100 |
| Ozone Depletion Potential | 0 |
As an accredited Perfluoroisobutyronitrile factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Sealed stainless steel cylinder containing 1 kg of Perfluoroisobutyronitrile, fitted with a pressure valve, stored upright and away from moisture. |
| Container Loading (20′ FCL) | For Perfluoroisobutyronitrile, load 20′ FCL with cylinders upright, block and brace, secure straps, ventilate, and placard dangerous goods. |
| Shipping | Perfluoroisobutyronitrile is shipped as a non-flammable, liquefied gas under pressure in DOT-specified steel cylinders, classified as Class 2.2, UN 3163. Transport requires upright securing, pressure-rated valves, and leak-tight seals. Avoid release due to high global-warming potential. Labels, documentation, and temperature controls must comply with applicable dangerous-goods regulations. |
| Storage | Store Perfluoroisobutyronitrile in tightly sealed, corrosion-resistant containers in a cool, dry, well-ventilated area. Protect from moisture, direct sunlight, and high temperatures. Keep away from oxidizers, ignition sources, and incompatible materials. Use proper labeling and ensure containers are grounded when dispensing. Maintain appropriate pressure and temperature controls to prevent leakage or decomposition. |
| Shelf Life | Shelf life is typically 24 months when stored sealed, dry, and away from heat or moisture. |
In 145 kV to 420 kV gas-insulated metal-enclosed switchgear, busbar and disconnector compartments are charged with a binary mixture of perfluoroisobutyronitrile (C4F7N, CAS 42532-60-5) in carbon dioxide to serve as the primary dielectric phase. Because these compartments do not perform fault-current interruption, the formulation is specified for lightning impulse withstand, power-frequency withstand, and partial discharge suppression; a representative volume fraction from public equipment documentation is 4 % to 6 % C4F7N, balance CO2, with no intentional oxygen addition. Fill pressure is OEM-specific but commonly reported as 0.70 MPa to 0.85 MPa absolute at 20 °C for 145 kV compartments and 0.80 MPa to 0.95 MPa absolute for 420 kV busbar sections where enclosure diameter and conductor spacing create higher dielectric stress. Compliance for these compartments is assessed under IEC 62271-203 for gas-insulated metal-enclosed switchgear above 52 kV, together with IEC 62271-1 for common type-test requirements and IEC 60270 for partial discharge acceptance. At the substance level, EU import quantities above 1 t/a require REACH registration under EC 1907/2006. On the manufacturing floor, the assembled compartment is first evacuated to a residual pressure below 100 Pa and held under vacuum until moisture desorption from cast-resin insulators meets a gas-phase limit below 150 ppmv. The C4F7N/CO2 blend is then introduced through a gas-handling skid equipped with mass-flow controllers or gravimetric mixing; post-fill verification uses non-dispersive infrared analysis for CO2 and gas chromatography or mass spectrometry for C4F7N concentration, with tolerance typically ±0.1 % v/v. Leak testing is conducted with a fluoronitrile-specific sniffer at flange level, and the acceptable leak rate on finished compartments is generally below 0.1 % per year. Terminal product types include 145 kV GIS bays, 245 kV busbar/disconnector modules, and 420 kV GIS bays for air-insulated-to-gas-insulated substation interfaces. Operational boundaries include the requirement to use only OEM-qualified seal and desiccant sets because the polar nitrile can interact with elastomer formulations that were not validated for C4F7N exposure, and gas recovery systems must be rated for fluoronitrile decomposition products rather than SF6 alone.
| Equipment class | Governing standard | C4F7N addition ratio | Fill pressure at 20 °C |
|---|---|---|---|
| HV GIS busbar, 145–420 kV | IEC 62271-203 | 4 %–6 % in CO2 | 0.70–0.95 MPa abs |
| MV RMU, 12–24 kV | IEC 62271-200 | 5 %–7 % in CO2 | 0.11–0.14 MPa abs |
| GIL, 245–420 kV | IEC 62271-204 | 4 %–6 % in CO2 | 0.70–0.90 MPa abs |
| Circuit breaker, ≥145 kV | IEC 62271-100 | 4 %–5 % C4F7N, 6 %–10 % O2 | 0.80–1.00 MPa abs |
Sealed distribution tanks rated 12 kV to 24 kV use C4F7N as dielectric insulation around vacuum interrupters rather than as an arc-quenching medium, because load and fault interruption occur inside the vacuum envelope. This separation changes the formulation requirement: public documentation for SF6-free RMUs indicates a C4F7N volume fraction of 5 % to 7 % in CO2 at a factory fill pressure of 0.11 MPa to 0.14 MPa absolute, which is lower than high-voltage GIS because the metal-enclosed tank is designed as a sealed pressure system rather than a continuously served gas zone. Compliance is evaluated under IEC 62271-200 for metal-enclosed switchgear above 1 kV up to 52 kV, with internal arc classification according to IEC 62271-200 Annex A, loss of service continuity category LSC2A, and enclosure protection per IEC 60529. Production processes involve robotic welding of stainless steel tanks, helium leak testing of the welded shell, then evacuation to below 200 Pa and backfilling with a premixed C4F7N/CO2 blend through a metered valve. The filled tank is then subjected to a routine power-frequency withstand test at nameplate values, partial discharge measurement according to IEC 60270, and final gas density monitor calibration against the mixture-specific pressure-temperature curve. Internal arc tests require the pressure relief disc to open at a defined pressure, and post-test decomposition gas must be extracted through activated carbon filters before the test cell is entered. Terminal finished products include 12 kV ring main units for secondary substations, 24 kV compact switchgear for wind-turbine nacelles, and dry-type RMUs for mining distribution where no liquid dielectric is permitted. The main process conflict is internal arc pressure rise after fault: the lower gas density of C4F7N/CO2 relative to SF6 can alter pressure relief timing, so tank volume and vent area must be tested rather than scaled from SF6 designs. Published data for the long-term compatibility of the C4F7N/CO2 mixture with internal polyester insulation and current-transformer potting compounds remain limited; OEM qualification is required before changing resin systems.
Across long-distance high-current links in underground substations and hydropower caverns, C4F7N/CO2 insulation is deployed in gas-insulated transmission lines where the electric field is approximately radial and the gas volume per meter is substantially larger than in switchgear bays. A representative mixture for GIL applications is 4 % to 6 % C4F7N in CO2, with fill pressure adjusted from 0.70 MPa to 0.90 MPa absolute at 20 °C depending on the rated voltage of 245 kV or 420 kV and the conductor-to-enclosure diameter ratio. Compliance is assessed under IEC 62271-204 for gas-insulated metal-enclosed transmission lines and IEC 62271-203 where the GIL interfaces with GIS; partial discharge acceptance follows IEC 60270, and the installation is subject to the same high-voltage testing sequence as the connected switchgear. The production process differs from switchgear because long pipe sections are welded on-site, cleaned to a defined particulate class, then evacuated in sectional gas zones to avoid moisture accumulation at weld joints. Each gas zone is charged independently through an SF6-free filling skid; gas composition is verified by non-dispersive infrared analysis for CO2 and photoacoustic spectroscopy or gas chromatography for C4F7N. Because the gas volume per meter is large, density monitoring is preferred over pressure monitoring, and the pressure-temperature-density model must be programmed with the C4F7N/CO2 mixture constants rather than SF6 constants. Terminal products include 420 kV GIL for underground connections between GIS bays and power transformers, 245 kV gas-insulated bus ducts for city substation retrofits, and switchyard busbar sections exposed to high mechanical load. Operational boundaries include moisture ingress below 150 ppmv per gas zone and a site leak rate below 0.1 % per year across flange pairs; due to the large gas inventory, filling and recovery time is longer than for a switchgear bay, and the gas-handling skid must maintain sub-atmospheric recovery capacity to avoid release of C4F7N decomposition products after switching operations.
For circuit breaker chambers rated 145 kV and above, C4F7N is blended with oxygen and carbon dioxide because binary C4F7N/CO2 mixtures exhibit insufficient arc cooling and can generate conductive carbonaceous deposits during high-current interruption. Publicly documented ternary blends for this interruption duty contain 4 % to 5 % C4F7N, 6 % to 10 % O2, balance CO2, with a fill pressure usually set 0.1 MPa to 0.2 MPa higher than an equivalent SF6 interrupter to compensate for the lower thermal conductivity of the carrier gas. Compliance is verified under IEC 62271-100 for AC circuit breakers, including terminal fault interruption, short-line fault, capacitive current switching, and mechanical endurance tests; gas analysis after interruption tests follows OEM-specific procedures adapted from IEC 60480 for used SF6 but cannot be transferred directly because decomposition species differ. The production process includes PTFE nozzle machining with throat diameters tuned to the higher mass-flow requirements of CO2-rich mixtures, contact material selection for longer arc dwell, and a post-fill conditioning sequence in which the interrupter is operated several times under no-load to passivate fresh contacts before dielectric testing. After interruption tests, the gas is recovered through a scrubber skid containing activated alumina and soda lime because C4F7N decomposition products include fluorinated carbonyl species and nitrile-derived species that require chemical filtration before compression. Terminal products include 145 kV dead-tank circuit breakers, 245 kV live-tank breakers, and 420 kV GIS circuit-breaker bays with combined disconnector and earthing switch modules. The main technical boundary is that direct substitution of C4F7N/CO2/O2 into an SF6 puffer design without OEM re-rating is not permitted; arc chute geometry, nozzle volume, and contact travel must be validated for the lower arc thermal conductivity and different post-arc dielectric recovery rate.
Retrofilling a legacy SF6 busbar compartment with C4F7N/CO2 is technically observable only when the original equipment manufacturer has validated the enclosure dielectric margin, gas monitor recalibration, and seal compatibility for the alternative gas. The replacement fill typically uses 4 % to 6 % C4F7N in CO2, with the fill pressure raised by 0.1 MPa to 0.2 MPa absolute from the SF6 nameplate value, and the density monitor must be reprogrammed or replaced because the mixture’s pressure-temperature-density relationship deviates from SF6. Relevant standards for this field process include IEC 62271-4 for gas handling procedures, IEC 62271-203 for post-modification dielectric tests on GIS above 52 kV, and EU Regulation 517/2014 where the site operates under fluorinated-gas management obligations. The process sequence consists of gas recovery, evacuation below 100 Pa, moisture measurement below 150 ppmv, dry nitrogen purging, a second evacuation, then charging with the C4F7N/CO2 blend through a mass-flow-controlled skid. After filling, a 24 h static gas analysis is performed to verify mixture composition before the compartment is re-energized; leak testing is repeated at the same acceptance level as the original SF6 design. Published data for this specific configuration are limited for long-term contact wear, arc decomposition products, and elastomer aging after retrofill, so the final dielectric performance must be confirmed by field power-frequency and partial discharge tests according to IEC 60270. Terminal products are not new builds but re-qualified 145 kV and 245 kV GIS busbar sections returned to service with C4F7N/CO2 insulation; circuit breaker retrofill is outside this scope unless the OEM has separately validated interruption performance.
Gas-insulated current transformers, voltage transformers, and bushing gas compartments integrated into GIS use the same C4F7N/CO2 mixture as adjacent busbar sections, typically 5 % C4F7N in CO2, to avoid cross-contamination at barrier insulators and to maintain uniform gas analysis across the bay. Compliance for these low-gas-volume compartments is assessed under IEC 61869-1 for instrument transformer general requirements, IEC 60270 for partial discharge measurement, and IEEE C57.13 where North American installation practices apply. The production process differs from switchgear because the active winding and insulation assembly are installed before the gas compartment is welded or bolted; after evacuation and drying, the compartment is backfilled with premixed gas through a low-flow needle valve to avoid turbulence-induced particle contamination. Partial discharge testing is then performed at 1.2 times rated phase voltage, with acceptance limits often specified at 5 pC for GIS-integrated instrument transformers, and the test is repeated after thermal cycling to identify gas-density-related void formation in cast-resin insulation. Terminal products include 145 kV gas-insulated current transformers, 245 kV voltage transformers for revenue metering or protection, and 420 kV bushing gas monitoring nodes connected to the station SF6-free management system. Because the gas volume is small, temperature fluctuations have a proportionally larger effect on pressure indication; the density monitor or pressure transducer must use mixture-specific compensation curves, and published data for this specific configuration are limited for long-term partial discharge drift over 20-year service intervals.
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Perfluoroisobutyronitrile, designated C4F7N in switchgear gas specifications and supplied commercially as 3M Novec 4710 Insulating Gas, is a fluorinated nitrile used as the dielectric component in carbon dioxide-based gas mixtures for medium- and high-voltage gas-insulated switchgear. The compound has Chemical Abstracts Service registry number 42532-60-5, molecular formula C4F7N, and molecular weight 195.04 g/mol. The pure material is a colourless, nonflammable gas at standard ambient conditions; its boiling point of -4.7°C at 101.3 kPa prevents direct high-pressure use in outdoor equipment and makes carbon dioxide blending mandatory. Electrical-grade material is supplied against acceptance criteria derived from the purity framework of IEC 60376:2018. Typical lot release values are purity ≥ 99.0% by volume, moisture ≤ 15 ppm by mass, acidity ≤ 3 ppm as hydrofluoric acid, non-volatile residue ≤ 0.01% by mass, and oxygen ≤ 50 ppmv. Manufacturer technical bulletins report a 100-year global warming potential of 2100 and an ozone depletion potential of 0. Pure-vapour dielectric strength tested under ASTM D2477-18 at 100 kPa and 20°C is approximately 2.2 times that of technical-grade SF6. The product is supplied either as liquefied pure compound for OEM blending or as certified C4F7N/CO2 pre-mixtures with C4F7N content from 4% to 10% by volume. In OEM documentation, the gas system using C4F7N/CO2 is referenced under the trade designation g3 for high-voltage equipment. In actual GIS filling operations, the pure product is not used as a dielectric fill; the boiling point and dew-point constraints would require heated enclosures and pressure limits incompatible with standard switchgear construction.
The primary constraint is condensation of the fluoronitrile component. The pure component boiling point of -4.7°C does not define the mixture limit; the partial pressure of C4F7N in the blend is lower than the total fill pressure. For a 4% C4F7N/96% CO2 blend at 0.60 MPa absolute, the mixture is normally specified for a minimum operating temperature of -30°C. A 6% blend at the same pressure is limited to approximately -25°C, and a 10% blend is limited to approximately -5°C. The relationship is nonlinear because C4F7N vapour pressure follows an exponential temperature dependence; a concentration increase of 2 mol% can shift the condensation threshold by several kelvin. These values are not absolute; they depend on the total pressure, the accuracy of the blending system, and the presence of non-condensable impurities such as nitrogen or oxygen. Equipment manufacturers therefore specify maximum allowable C4F7N content for each filling pressure and minimum ambient temperature, and gas-filling records include the reference temperature at which the final pressure is measured. Published data for configurations operating below -30°C with this gas class is limited, and equipment for such climates generally derates the C4F7N content below 4%, which requires increased compartment size or higher CO2 pressure.
Interruption of short-circuit current in C4F7N/CO2 mixtures is dominated by the carbon dioxide carrier gas, not by the fluoronitrile. The fluoronitrile provides a strong electron-attachment cross-section that raises the dielectric withstand of the cold gas; the carbon dioxide supplies the mass flow, thermal conductivity, and pressure rise across the puffer that are necessary for arc cooling. In 145 kV gas-insulated switchgear, manufacturer-published type-test reports indicate that a 4% C4F7N/96% CO2 fill at 0.60 MPa absolute can meet short-circuit making and breaking duties up to 40 kA per IEC 62271-100 when the interrupter nozzle throat, contact travel, and puffer volume are re-optimized for CO2-dominated flow. This is a fundamental difference from SF6 switchgear, where the interrupting gas also provides most of the dielectric strength. The dielectric performance of the mixture at equal pressure is lower than SF6; therefore, equipment is designed with modified field grading, increased gas pressure, or larger clearance envelopes. The composite gas also exhibits a different pressure-temperature-density relationship, so density monitoring systems must be re-calibrated for the specific C4F7N/CO2 ratio; a standard SF6 density monitor will report an incorrect fill if reused without reprogramming. After fault interruption, decomposition products include carbon monoxide, lower fluorocarbons, and reactive fluoride species; gas sampling must use gas chromatography with mass-selective detection or Fourier-transform infrared spectroscopy because the routine IEC 60480 SF6 analysis matrix is not directly applicable.
On production filling lines for C4F7N/CO2-rated GIS, cylinders are held in heated cabinets between 15°C and 25°C. Adiabatic expansion at the pressure regulator can reduce the gas temperature below the blend dew point, producing two-phase flow and inaccurate fill pressure. Filling manifolds use pressure-controlled stainless-steel regulators and PTFE seat materials; the gas is introduced into evacuated compartments after the vacuum level has been verified. Evacuation to ≤ 50 Pa absolute for 30 min is required when ambient relative humidity exceeds 60%; residual moisture can hydrolyse decomposition products and form hydrofluoric acid in service. Dew-point transmitters calibrated for CO2 are installed in the fill line, and the final compartment pressure is normalised to 20°C using the gas-density curve for the specific blend. Field experience from retrofill projects has shown that incorrect cylinder orientation or withdrawal rates above approximately 2 kg/h per cylinder can cause liquid condensation in the regulator stage, producing intermittent pressure fluctuations and erroneous fill mass readings. Certified pre-mixture cylinders are controlled to ± 0.2 mol% C4F7N by gas chromatography with thermal conductivity detection at the blending plant. This is a tighter tolerance than typical industrial mixed-gas specifications and is required because the dielectric withstand of the mixture is sensitive to C4F7N content.
The substitution is not a direct drop-in fill. Because the dielectric strength of C4F7N/CO2 is lower than that of SF6 at the same pressure, OEMs raise the filling pressure from about 0.40 MPa to 0.60 MPa absolute for 145 kV GIS and may increase clearances or adjust field-grading screens. The environmental benefit is calculated from the gas mass and the composite global warming potential. A 4% C4F7N/96% CO2 mixture has a composite 100-year GWP of approximately 85, compared with 23,500 for SF6. This represents a reduction of more than 99% in global warming potential of the fill gas mass, assuming the same leakage mass is released. However, the fluoronitrile component has a GWP of 2100 and an atmospheric lifetime reported as 22 years; therefore, the gas is not environmentally benign if vented. The difference from fluoroketone C5F10O is material: C5F10O has a much lower GWP (<1) and a boiling point of 26.9°C, but its condensation threshold restricts low-temperature outdoor operation unless the partial pressure is kept very low. C4F7N remains gaseous at sub-zero conditions in CO2 mixtures, which is why it is preferred in outdoor equipment.
| Property | C4F7N | SF6 | C5F10O |
|---|---|---|---|
| Molecular weight | 195.04 g/mol | 146.06 g/mol | 266.03 g/mol |
| Boiling point at 101.3 kPa | -4.7°C | -63.8°C | 26.9°C |
| Dielectric strength relative to SF6 | ~2.2 | 1.0 | ~1.4 |
| 100-year GWP | 2100 | 23,500 | <1 |
| Ozone depletion potential | 0 | 0 | 0 |
Compared with SF6, C4F7N offers lower GWP but not zero; compared with C5F10O, it offers better low-temperature performance but higher GWP and stronger adsorption onto some desiccants. These differences determine the selection of C4F7N/CO2 for dead-tank GIS, gas-insulated bus ducts, and gas-insulated lines where cold-weather ratings are required, whereas C5F10O/air mixtures are typically restricted to temperature-controlled indoor installations.
After arc interruption or partial discharge activity, the gas cannot be evaluated using the SF6-specific acceptance levels of IEC 60480. Decomposition of C4F7N and CO2 generates carbon monoxide, fluorocarbon fragments, and reactive fluoride species that require dedicated measurement techniques. Utilities must establish a separate gas-analysis matrix that includes gas chromatography with mass-selective detection, Fourier-transform infrared spectroscopy, and hydrogen fluoride detector tubes. The absence of sulfur oxyfluoride species means that SOF2 and SO2F2 indicators used for SF6 condition assessment are not applicable. This is an operational discontinuity for maintenance organisations that have standardised SF6 gas carts and laboratory protocols. Adsorbent beds in the equipment must be treated as gas-ratio control elements, not only as moisture and decomposition-product scavengers, because some activated alumina and molecular sieve materials can adsorb C4F7N and shift the blend ratio during commissioning. OEM procedures require replacement of SF6-rated adsorbents with C4F7N/CO2-compatible beds when a compartment is retrofilled.
Chemical compatibility of perfluoroisobutyronitrile with elastomers, lubricants, and recovery compressors imposes additional boundaries. Oil-lubricated compressors and vacuum pumps can introduce hydrocarbon vapour into the gas stream, which can degrade dielectric performance and complicate post-fault gas analysis; dry-running or fluorinated-fluid-sealed recovery compressors are specified. Seal materials are limited to PTFE, fluorocarbon elastomers, or ethylene-propylene diene monomer that has been tested for fluoronitrile exposure; plasticizer extraction from nitrile rubber can produce non-volatile residue levels above the 0.01% acceptance criterion. Pure C4F7N and rich pre-mixtures should not be intentionally vented; recovery systems must be capable of separating or consolidating the gas at pressures above the mixture dew point. The parent vapour is not classified as ozone-depleting under the Montreal Protocol and is registered under REACH, but published acute inhalation data for the pure vapour is limited; the safety data sheet identifies potential exposure to hydrogen fluoride and carbon monoxide during thermal decomposition as the primary industrial hygiene concern. Cylinder storage temperatures above 50°C should be avoided because the vapour pressure of pure C4F7N rises rapidly with temperature and may exceed the pressure rating of standard mixed-gas regulators.
