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1,1-Difluoroethylene (Vinylidene Fluoride / VDF), identified in industrial chemistry, fluoropolymer synthesis, and fluorochemical engineering by the molecular formula C2H2F2, is a synthetic organic compound belonging to the class of fluorinated alkenes and organofluorides.
1,1-Difluoroethylene, being a colorless and extremely flammable gas with a faint ethereal odor at room temperature, stands out for high reactivity and polymerization capability.
1,1-Difluoroethylene plays a strategic role in the chemical industry primarily as a monomer in the synthesis of fluoropolymers, an intermediate in producing fluorinated fluorosilicone resins with high thermal and chemical resistance, and a processing agent in advanced polymerization reactors.
CAS Number: 75-38-7.
EC / EINECS Number: 200-867-7.
PubChem CID: 6369.
UN Dangerous Goods Number: UN 1959 (Class 2.1 Flammable Gas).
Molecular Weight: 64.03 g/mol.
Synonyms: 1,1-Difluoroethylene, 1,1-Difluoroethene, Vinylidene fluoride, Vinylidene difluoride, 1,1-DFE, Ethene, 1,1-difluoro-, VDF, Fluoroethylene, Vinyl fluoride derivative.
Key Properties, Physicochemistry, and Identifiers
Density: Liquid density 1.263 g/cm3 at boiling point; gas density 2.67 g/L at 21 °C.
Melting Point: -144 °C.
Boiling Point: -85.7 °C.
Flash Point: Ultra-flammable in gas state (<-80 °C for liquefied gas).
Vapor Pressure: 3620 kPa (35.7 atm) at 21 °C.
Water Solubility: Very slightly soluble in water (0.63 g/L at 25 °C).
Solubility in Organic Solvents: Soluble in ethanol, diethyl ether, acetone, tetrahydrofuran, and chlorinated organic solvents.
Thermal Decomposition: 1,1-Difluoroethylene decomposes into highly toxic and corrosive hydrogen fluoride (HF) and carbonyl fluoride gases upon exposure to high temperatures or open flames.
Food Additive Status: 1,1-Difluoroethylene is strictly not suitable for food additive use or human consumption (No E-number).
Manufacturing Processes and Chemical Synthesis
1. Pyrolysis of 1,1,1-Trifluoroethane: 1,1-Difluoroethylene is synthesized on an industrial scale mostly via thermal pyrolysis of 1,1,1-trifluoroethane (R-143a) or 1-chloro-1,1-difluoroethane (R-142b) at high temperatures with elimination of hydrogen chloride (HCl).
2. Synthesis from Chlorodifluoromethane: 1,1-Difluoroethylene can also be produced via high-pressure catalytic gas-phase reactions of chlorodifluoromethane (R-22) and radical reactants.
3. Purification and Gas Cylinder Filling: Crude 1,1-Difluoroethylene gas obtained from the reaction mixture is brought to high purity via cryogenic distillation and stored in pressurized steel cylinders with added inhibitors to prevent spontaneous polymerization.
Applications and Industrial Uses
1. PVDF Polymer Production: The primary industrial application of 1,1-Difluoroethylene is its use as a monomer in homopolymerization to synthesize high-performance polyvinylidene fluoride (PVDF) plastic resins.
2. Fluoroelastomer (FKM) Synthesis: 1,1-Difluoroethylene is copolymerized with hexafluoropropylene (HFP) and tetrafluoroethylene (TFE) to produce FKM fluororubbers featuring high thermal and chemical resistance.
3. Lithium-Ion Binder Materials: PVDF resins based on 1,1-Difluoroethylene hold a strategic position as binders in cathode and anode electrode adhesives of lithium-ion batteries.
4. Piezoelectric and Piezo-Sensor Manufacturing: 1,1-Difluoroethylene copolymers (PVDF-TrFE) are used in acoustic sensors and medical ultrasonic devices thanks to their piezoelectric and pyroelectric properties.
5. Chemical Intermediate: 1,1-Difluoroethylene is evaluated as a building block in synthesizing advanced fluorinated specialty chemicals, pharmaceutical building blocks, and fluorinated solvent components.
6. High-Durability Membrane Coatings: 1,1-Difluoroethylene polymers are utilized in water purification membranes, architectural protective exterior paints, and photovoltaic panel backsheets.
Safety, Toxicology, and Storage Standards
Hazard Classification: According to GHS standards, 1,1-Difluoroethylene is classified as Extremely Flammable Gas (Category 1A) and Gas Under Pressure (Pressurized Liquefied Gas).
Health Risks and Toxicity: Inhalation of high concentrations of 1,1-Difluoroethylene gas causes asphyxiation by reducing ambient oxygen, mild drowsiness, and dizziness.
Contact Risk: Rapid evaporation of liquefied 1,1-Difluoroethylene gas causes severe cryogenic burns (frostbite) upon skin and eye contact.
EHS and Storage Conditions: 1,1-Difluoroethylene must be kept strictly away from ignition sources, sparks, open flames, static electricity, and direct sunlight.
Chemical Incompatibility: 1,1-Difluoroethylene can react violently and explosively upon contact with strong oxidizers, halogens, alkali metals, and reactive catalysts.
Storage Standards: 1,1-Difluoroethylene must be stored in a cool, ventilated, explosion-proof (ATEX) dedicated pressure steel cylinder storage area, with cylinders secured in an upright position.
