Preparation method of tetrafluoroethylene-hexafluoropropylene copolymer with regular chain segments

Abstract

The invention discloses a preparation method of a tetrafluoroethylene-hexafluoropropylene copolymer with regular chain segments, and relates to the technical field of fluorine-containing polymer synthesis. According to the method, the conversion efficiency of hexafluoropropylene and tetrafluoroethylene is optimized through constant-pressure continuous feeding, and a low-temperature and low-dosage initiator is adopted to prolong the chain growth stage and reduce the chain termination frequency, so that the copolymer with higher molecular weight and narrower molecular weight distribution is obtained. And the chain segment regularity of the copolymer is effectively improved by using the chain segment regularity accelerant and the specific molecular weight regulator, so that the tensile strength and the thermal deformation temperature are improved. And the performance deviation of different batches is obviously improved. The method has relatively good industrial operability and is suitable for preparing the high-performance fluoropolymer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fluoropolymer synthesis, and particularly relates to a preparation method of a chain segment regular tetrafluoroethylene-hexafluoropropylene copolymer. BACKGROUND

[0002] The copolymer of hexafluoropropylene (HFP) and tetrafluoroethylene (TFE), namely FEP (Fluorinated Ethylene Propylene), is a melt-processable fluoropolymer, which has superior chemical resistance and electrical insulation of PTFE-like polymers, and has the ability of extrusion and injection molding. The excellent performance of FEP makes it widely used in high-performance fields such as electronic insulation, chemical pipelines, chemical containers, etc.

[0003] Patent document: patent US20040072977A1 Aqueous emulsion polymerization process for producing fluoropolymers. The traditional industrial method for preparing FEP is mainly to use water phase emulsion or dispersion polymerization technology, and to copolymerize HFP and TFE by free radical method, such as. The process temperature is generally in the range of 10-100℃, and is preferably 30-80℃, the pressure is generally in the range of 4-30 bar (about 0.4-3.0 MPa), and the optimal pressure range is generally in the range of 0.8-2.0 MPa. Emulsifiers (such as PFOS, PFOA) are used to stabilize the dispersion system, to form a microemulsion in water, and to make the monomers polymerize in the particle core, so as to improve the reaction efficiency and product quality.

[0004] Although there are related patents and literatures reporting the preparation method of the system, the existing technology has the following deficiencies: Lack of systematic condition comparison: there are few systematic comparison studies on the performance indicators such as product conversion rate, molecular weight distribution, residual initiator content, etc. in the published data, especially the effect of different temperature and dosage combinations has not formed a complete system description.

[0005] Limited product performance: due to the insufficient optimization of the interaction among temperature-pressure-initiator, the melt flow index (MFI), molecular weight and processing performance consistency of the prepared FEP copolymer are often insufficient, which is difficult to meet the requirements of melt processability and physical performance at the application end.

[0006] Emulsifier residue problem: Although the patent document WO2020162512A1 Tetrafluoroethylene polymer production method and composition uses perfluorosulfonic acid emulsifier, there are technical challenges in degreasing, cleaning and eliminating residual emulsifier, which affects the performance and safety of the final resin.

[0007] Chain regularity problem: Patent document CN112358564A uses water as medium and organic peroxide of structural formula (1) as initiator to prepare polytetrafluoroethylene by precipitation polymerization of tetrafluoroethylene and hexafluoropropylene. In addition, the polymer particle size and melt viscosity are controllable, which can meet the needs of different aspects. It does not require the chain regularity of the copolymer.

[0008] There is an urgent need for an FEP preparation method with optimized process parameters, which can realize high conversion rate, high molecular weight, low residual agent, and multi-batch controllable industrial preparation system by reasonably controlling the type and dosage of initiator, temperature and pressure, constant pressure feeding mode, and clear post-treatment agent removal steps. SUMMARY

[0009] Based on the above background technology, the present application proposes a preparation method of chain segment regular tetrafluoroethylene-hexafluoropropylene copolymer.

[0010] The technical scheme is as follows: A preparation method of chain segment regular tetrafluoroethylene-hexafluoropropylene copolymer, according to mass fraction, comprising the following steps: a) After replacing the reaction kettle with nitrogen and vacuumizing, add 750-850 parts of deionized water; b) Introduce 350-450 parts of hexafluoropropylene monomer into the water phase; c) Increase the temperature in the kettle to 10-50℃; d) Add chain segment regularity promoter, 0.5-2 parts of surfactant, 0.1-1.2 parts of molecular weight regulator and 0.2-0.8 parts of initiator; e) Introduce tetrafluoroethylene monomer until the pressure in the kettle reaches 0.6-1.4 MPa, and the mass of TFE is 200-500 parts; f) Stir and continuously supply TFE monomer at the same time, and adjust the feed valve to keep the pressure in the kettle constant at 0.6-1.4 MPa; g) Maintain the pressure and temperature for 2.5-7 hours; h) After the reaction is completed, collect the material, and heat the obtained copolymer in a constant temperature oven at 40-80℃ for 2-5 hours to remove residual initiator and unreacted monomer.

[0011] Preferably, the oxygen content is not more than 10 ppm and the nitrogen content is not more than 5% after the reactor is vacuumed.

[0012] Preferably, the chain segment regularity promoter is added in an amount of 0.4-0.8 wt% of the total amount of hexafluoropropylene monomer.

[0013] Preferably, the chain segment regularity promoter is prepared by the following method: In the reactor, 3-7 parts of 3,3'-dipyridyl-6,6'-diamine, 9-18 parts of allyl glycidyl ether, 5-10 parts of 2-(perfluorohexyl)ethyl methacrylate, and 150-300 parts of ethanol are added, and the temperature is raised to 85-95°C for 180-220 minutes. The product is recrystallized from ethanol, filtered, and vacuum dried to remove residual ethanol to obtain the chain segment regularity promoter.

[0014] Preferably, the ethanol recrystallization process is at a dissolution temperature of 70-80°C and a cooling temperature of 0-5°C.

[0015] Preferably, the vacuum drying process is at a temperature of 60-70°C and a vacuum degree of 0.09 MPa.

[0016] Preferably, the surfactant is a mixture of one or more of ammonium perfluoropolyether carboxylate, ammonium perfluorooctyl sulfonate, and perfluorooctyl sulfonamide.

[0017] Preferably, the molecular weight regulator is selected from methanol or diethyl malonate.

[0018] Preferably, the initiator is selected from perfluorobutyryl peroxide, or perfluoro(3,6-dioxaoctanoyl) peroxide, or perfluoro(2-methyl-3-oxahexanoyl) peroxide.

[0019] Reaction mechanism The amino group of 3,3'-dipyridyl-6,6'-diamine undergoes ring-opening addition with the epoxy group of allyl glycidyl ether, and the remaining amino group undergoes Michael addition with the double bond of dimethyl fumarate. Ethanol as a solvent can promote the dissolution of 3,3'-dipyridyl-6,6'-diamine, increase the reaction rate, and the rigid structure of the dipyridyl ring enhances the π-π interaction between the additive and the fluoromonomer, thereby improving the chain segment regularity of the copolymer.

[0020] Compared with the prior art, the present application has the following advantages: 1) By using constant pressure continuous feeding in the present method, pressure drop or uneven reaction caused by one-time supply is avoided, thereby significantly improving the conversion efficiency of HFP and TFE monomers.

[0021] 2) The method uses low temperature and low dose initiator, which can prolong the chain growth stage, reduce the chain termination frequency, and form higher molecular weight and more uniform polymer molecular weight distribution.

[0022] 3) The tensile strength and heat distortion temperature of the copolymer are effectively improved, and the performance deviation of different batches of products is effectively improved. DETAILED DESCRIPTION

[0023] The characteristics of the present application are further illustrated by the following examples, but the scope of protection of the patent is not limited by the examples. Example 1

[0024] Raw material formula: Deionized water: 750g Hexafluoropropylene (HFP): 350g Tetrafluoroethylene (TFE): 200g Chain segment regularity promoter: 0.4wt% of total monomer (calculated as HFP+TFE) Surfactant (perfluoropolyether ammonium carboxylate): 0.5g Molecular weight regulator (methanol): 0.1g Initiator (perfluorobutyryl peroxide): 0.2g Preparation steps: 1. Reactor pretreatment (step a): Nitrogen was replaced in the reactor for 3 times, vacuumed to oxygen content ≤10ppm, nitrogen content ≤5%, and 750g deionized water was added.

[0025] 2. HFP is introduced (step b): 350g HFP is introduced into the water phase.

[0026] 3. Temperature rise (step c): the temperature in the kettle is raised to 10℃.

[0027] 4. Additives addition (step d): Add 0.4wt% of total monomer chain segment regularity promoter, 0.5g perfluoropolyether ammonium carboxylate, 0.1g methanol, and 0.2g perfluorobutyryl peroxide.

[0028] 5. TFE pressurization (step e): introduce TFE to reach 0.6MPa pressure in the kettle (total TFE mass 200g).

[0029] 6. Pressure control (step f): stir (300rpm) and continuously supply TFE, and maintain the pressure constant at 0.6MPa by adjusting the valve.

[0030] 7. Polymerization reaction (step g): reaction at 10℃, 0.6MPa for 2.5 hours.

[0031] 8. Post-treatment (step h): After collection, the copolymer was heated in a 40°C oven for 2 hours to remove residual material.

[0032] Segment regularity promoter preparation: Into the reactor were added 3 g 3,3'-dipyridyl-6,6'-diamine, 9 g allyl glycidyl ether, 5 g 2-(perfluorohexyl)ethyl methacrylate, 150 g ethanol, and the temperature was raised to 85°C for 180 minutes.

[0033] After dissolution at 70°C, recrystallization was performed by cooling to 0°C, and the product was dried at 60°C under 0.09 MPa vacuum after filtration to obtain the promoter. Example 2

[0034] Raw material formulation: Deionized water: 800 g HFP: 400 g TFE: 300 g Segment regularity promoter: 0.5 wt% of the total monomer amount Surfactant (ammonium perfluorooctylsulfonate): 1.0 g Molecular weight regulator (diethyl malonate): 0.5 g Initiator (perfluoro(3,6-dioxaoctanoyl) peroxide): 0.4 g Preparation steps: 1. Reactor pre-treatment: Same as Example 1, with the addition of 800 g deionized water.

[0035] 2. HFP introduction: 400 g HFP was introduced.

[0036] 3. Temperature increase: The temperature in the reactor was increased to 25°C.

[0037] 4. Additive addition: 0.5 wt% promoter, 1.0 g ammonium perfluorooctylsulfonate, 0.5 g diethyl malonate, and 0.4 g initiator were added.

[0038] 5. TFE pressurization: TFE was introduced to a pressure of 1.0 MPa (total mass 300 g).

[0039] 6. Pressure control: The pressure was maintained at 1.0 MPa, with a stirring speed of 350 rpm.

[0040] 7. Polymerization: The reaction was performed at 25°C and 1.0 MPa for 4 hours.

[0041] 8. Post-treatment: Heating in a 50°C oven for 3 hours.

[0042] Segment regularity promoter preparation: 5g 3,3'-dipyridyl-6,6'-diamine, 12g allyl glycidyl ether, 7g 2-(perfluorohexyl)ethyl methacrylate, 200g ethanol, 90°C for 200 minutes.

[0043] 75°C dissolution, 3°C recrystallization, 65°C, 0.09 MPa vacuum drying. Example 3

[0044] Raw material formulation: Deionized water: 820g HFP: 430g TFE: 400g Chain regularity promoter: 0.7 wt% of total monomer Surfactant (perfluorooctyl sulfonamide): 1.5g Molecular weight regulator (methanol): 0.8g Initiator (perfluoro(2-methyl-3-oxahexanoyl) peroxide): 0.6g Preparation steps: 1. Reactor pre-treatment: same as Example 1, add 820g deionized water.

[0045] 2. HFP introduction: introduce 430g HFP.

[0046] 3. Temperature increase: increase the temperature in the reactor to 40°C.

[0047] 4. Additives addition: add 0.7 wt% promoter, 1.5g perfluorooctyl sulfonamide, 0.8g methanol, 0.6g initiator.

[0048] 5. TFE pressurization: introduce TFE to a pressure of 1.2 MPa (total mass 400g).

[0049] 6. Pressure control: maintain a pressure of 1.2 MPa, stirring speed 400 rpm.

[0050] 7. Polymerization: 40°C, 1.2 MPa for 6 hours.

[0051] 8. Post-treatment: 70°C oven for 4 hours.

[0052] Chain regularity promoter preparation: 6g 3,3'-dipyridyl-6,6'-diamine, 16g allyl glycidyl ether, 9g 2-(perfluorohexyl)ethyl methacrylate, 250g ethanol, 92°C for 210 minutes.

[0053] 78°C dissolution, 4°C recrystallization, 68°C, 0.09 MPa vacuum drying. Example 4

[0054] Raw material formulation: Deionized water: 850 g HFP: 450 g TFE: 500 g Chain regularity promoter: 0.8 wt% of total monomer Surfactant (ammonium perfluoropolyether carboxylate + ammonium perfluorooctyl sulfonate, 1 : 1): 2.0 g Molecular weight regulator (diethyl malonate): 1.2 g Initiator (perfluorobutyryl peroxide): 0.8 g Preparation steps: 1. Reactor pre-treatment: same as Example 1, with 850 g of deionized water added.

[0055] 2. HFP introduction: 450 g of HFP was introduced.

[0056] 3. Temperature increase: the temperature in the reactor was increased to 50°C.

[0057] 4. Additives introduction: 0.8 wt% of promoter, 2.0 g of mixed surfactant, 1.2 g of diethyl malonate, and 0.8 g of initiator were added.

[0058] 5. TFE pressurization: TFE was introduced to a pressure of 1.4 MPa (total mass 500 g).

[0059] 6. Pressure control: the pressure was maintained at 1.4 MPa with a stirring speed of 450 rpm.

[0060] 7. Polymerization: the reaction was carried out at 50°C and 1.4 MPa for 7 hours.

[0061] 8. Post-treatment: heating in an oven at 80°C for 5 hours.

[0062] Chain regularity promoter preparation: 7 g of 3,3'-dipyridyl-6,6'-diamine, 18 g of allyl glycidyl ether, 10 g of 2-(perfluorohexyl)ethyl methacrylate, 300 g of ethanol, and 95°C for 220 minutes.

[0063] Dissolution at 80°C, recrystallization at 5°C, and drying at 70°C under 0.09 MPa vacuum.

[0064] Comparative Example 1 Raw material formulation: Deionized water: 750 g Hexafluoropropene (HFP): 350 g Tetrafluoroethylene (TFE): 200 g Chain regularity promoter: 0.4 wt% of total monomers (calculated as HFP+TFE) Surfactant (perfluoropolyether carboxylic acid ammonium): 0.5 g Molecular weight regulator (methanol): 0.1 g Initiator (perfluorobutyryl peroxide): 0.2 g Preparation steps: 1. Reactor pretreatment (step a): The reactor was replaced with nitrogen for 3 times, vacuumed to oxygen content ≤10 ppm, nitrogen content ≤5%, and 750 g of deionized water was added.

[0065] 2. HFP feeding (step b): 350 g of HFP was fed into the aqueous phase.

[0066] 3. Temperature rise (step c): the temperature in the reactor was raised to 10°C.

[0067] 4. Additive addition (step d): 0.5 g of perfluoropolyether carboxylic acid ammonium, 0.1 g of methanol, and 0.2 g of perfluorobutyryl peroxide were added.

[0068] 5. TFE pressurization (step e): TFE was fed until the pressure in the reactor reached 0.6 MPa (total mass of TFE 200 g).

[0069] 6. Pressure control (step f): stirring (300 rpm) and continuous supply of TFE, the pressure was maintained constant at 0.6 MPa by adjusting the valve.

[0070] 7. Polymerization reaction (step g): reaction at 10°C, 0.6 MPa for 2.5 hours.

[0071] 8. Post-treatment (step h): after the material was collected, the copolymer was heated in a 40°C constant temperature oven for 2 hours to remove the residual.

[0072] Comparative Example 2 Raw material formula: Deionized water: 750 g Hexafluoropropylene (HFP): 350 g Tetrafluoroethylene (TFE): 200 g Chain regularity promoter: 0.4 wt% of total monomers (calculated as HFP+TFE) Surfactant (perfluoropolyether carboxylic acid ammonium): 0.5 g Molecular weight regulator (methanol): 0.1 g Initiator (perfluorobutyryl peroxide): 0.2 g Preparation steps: 1. Reactor pretreatment (step a): The reactor 3 was replaced with nitrogen and vacuumed to an oxygen content of ≤10 ppm and a nitrogen content of ≤5%. 750 g of deionized water was added.

[0073] 2. HFP was introduced (step b): 350 g of HFP was introduced into the water phase.

[0074] 3. Temperature was raised (step c): The temperature in the reactor was raised to 10°C.

[0075] 4. Additives were added (step d): 0.4 wt% of the total amount of monomers of segment regularity promoter, 0.5 g of perfluoropolyether ammonium carboxylate, 0.1 g of methanol, and 0.2 g of perfluorobutyryl peroxide were added.

[0076] 5. TFE was pressurized (step e): TFE was introduced until the pressure in the reactor reached 0.6 MPa (total mass of TFE was 200 g).

[0077] 6. Pressure was controlled (step f): TFE was continuously supplied while stirring (300 rpm) and the pressure was maintained at 0.6 MPa by adjusting the valve.

[0078] 7. Polymerization was carried out (step g): The reaction was carried out at 10°C and 0.6 MPa for 2.5 hours.

[0079] 8. Post-treatment (step h): After the product was collected, the copolymer was heated in a thermostat at 40°C for 2 hours to remove the residual substances.

[0080] Preparation of segment regularity promoter: 9 g of allyl glycidyl ether, 5 g of 2-(perfluorohexyl)ethyl methacrylate, and 150 g of ethanol were added to the reactor, and the temperature was raised to 85°C for 180 minutes.

[0081] After being dissolved at 70°C, it was recrystallized by cooling to 0°C, and then dried at 60°C and 0.09 MPa vacuum after filtration to obtain the promoter.

[0082] Comparative Example 3 Raw material formula: Deionized water: 750 g Hexafluoropropylene (HFP): 350 g Tetrafluoroethylene (TFE): 200 g Segment regularity promoter: 0.4 wt% of the total amount of monomers (calculated based on HFP+TFE) Surfactant (perfluoropolyether ammonium carboxylate): 0.5 g Molecular weight regulator (methanol): 0.1 g Initiator (perfluorobutyryl peroxide): 0.2 g Preparation steps: 1. Reactor pretreatment (step a): The reactor 3 was purged with nitrogen and vacuumed to an oxygen content of ≤10 ppm and a nitrogen content of ≤5%. 750 g of deionized water was added.

[0083] 2. HFP introduction (step b): 350 g of HFP was introduced into the water phase.

[0084] 3. Temperature increase (step c): The temperature in the reactor was increased to 10°C.

[0085] 4. Additives addition (step d): 0.4 wt% of the total amount of monomers of segment regularity promoter, 0.5 g of perfluoropolyether ammonium carboxylate, 0.1 g of methanol, and 0.2 g of perfluorobutyryl peroxide were added.

[0086] 5. TFE pressurization (step e): TFE was introduced until the pressure in the reactor reached 0.6 MPa (total mass of TFE 200 g).

[0087] 6. Pressure control (step f): The TFE was continuously supplied while stirring (300 rpm) and the pressure was maintained constant at 0.6 MPa by adjusting the valve.

[0088] 7. Polymerization reaction (step g): The reaction was carried out at 10°C and 0.6 MPa for 2.5 hours.

[0089] 8. Post-treatment (step h): After the product was collected, the copolymer was heated in a thermostat at 40°C for 2 hours to remove the residual substances.

[0090] Segment regularity promoter preparation: 3 g of 3,3'-dipyridyl-6,6'-diamine, 9 g of allyl glycidyl ether, and 150 g of ethanol were added to the reactor, and the temperature was increased to 85°C for 180 minutes.

[0091] After dissolution at 70°C, it was recrystallized by cooling to 0°C, and after filtration, it was dried at 60°C under a vacuum of 0.09 MPa to obtain the promoter.

[0092] Test methods: 1) Melt flow index (MFI) The melt flow index (MFI) was determined according to ASTM D1238 / ISO 1133 at 260°C and a load of 2.16 kg, measuring the weight of the extruded material in 10 minutes (g / 10 min).

[0093] 2) Tensile strength test The tensile test was performed according to the ISO 527-1 standard. The test was performed at room temperature (23°C ± 2°C) at a tensile rate of 5 mm / min.

[0094] 3) Heat deflection temperature (HDT) test Heat deflection temperature test was performed according to ISO 75-1 standard. The test was performed at a temperature ramp of 2°C / min under a load of 0.45 MPa until the sample deformed visibly 4) Residual initiator content The content of unreacted or decomposed perfluorinated peroxide in the sample was detected by high performance liquid chromatography (HPLC) to quantify the residual ppm level.

[0095] Test results: The above data and analysis clearly demonstrate the superiority of the present method in terms of stable and adjustable molecular weight, tensile strength, heat deflection temperature, and low initiator residue.

[0096] The above is only a specific embodiment of the present application, but the technical features of the present application are not limited thereto. Any simple change, equivalent replacement or modification made on the basis of the present application to solve the basically same technical problem and achieve the basically same technical effect is covered within the protection scope of the present application.

Claims

1. A process for the preparation of a chain-regular tetrafluoroethylene-hexafluoropropylene copolymer, characterized by, According to the mass fraction, comprising the following steps: a) After the reactor is replaced with nitrogen and vacuumized, 750-850 parts of deionized water is added; b) 350-450 parts of hexafluoropropylene monomer is introduced into the water phase; c) The temperature in the reactor is raised to 10-50℃; d) Chain segment regularity promoter, 0.5-2 parts of surfactant, 0.1-1.2 parts of molecular weight regulator and 0.2-0.8 parts of initiator are added; e) Tetrafluoroethylene monomer is introduced until the pressure in the reactor reaches 0.6-1.4 MPa, and the mass of TFE is 200-500 parts; f) Stirring is carried out while continuously supplying TFE monomer, and the pressure in the reactor is kept constant at 0.6-1.4 MPa by adjusting the feed valve; g) The reaction is maintained at the pressure and temperature for 2.5-7 hours; h) After the reaction is completed, the product is collected, and the obtained copolymer is heated in a thermostat at 40-80℃ for 2-5 hours to remove residual initiator and unreacted monomer; The chain segment regularity promoter is prepared by reacting 3,3'-dipyridyl-6,6'-diamino, allyl glycidyl ether and 2-(perfluorohexyl)ethyl methacrylate.

2. A process for the preparation of a chain-regular tetrafluoroethylene-hexafluoropropylene copolymer according to claim 1, characterized in that: The oxygen content in the reactor after vacuumization is required to be no more than 10 ppm, and the nitrogen content is required to be no more than 5%.

3. A process for the preparation of a chain-regular tetrafluoroethylene-hexafluoropropylene copolymer according to claim 1, characterized by: The amount of chain segment regularity promoter added is 0.4-0.8 wt% of the total amount of hexafluoropropylene monomer.

4. A process for the preparation of a chain-regular tetrafluoroethylene-hexafluoropropylene copolymer according to claim 1, characterized by: Preparation method of the chain segment regularity promoter: In the reactor, 3-7 parts of 3,3'-dipyridyl-6,6'-diamino, 9-18 parts of allyl glycidyl ether, 5-10 parts of 2-(perfluorohexyl)ethyl methacrylate and 150-300 parts of ethanol are added, and the temperature is raised to 85-95℃ for 180-220 minutes. The product is recrystallized from ethanol, filtered and vacuum dried to remove residual ethanol to obtain the chain segment regularity promoter.

5. A process for the preparation of a chain-regular tetrafluoroethylene-hexafluoropropylene copolymer according to claim 4, characterized in that: The recrystallization process of ethanol: the dissolution temperature is 70-80℃, and the cooling temperature is 0-5℃.

6. A process for the preparation of a chain-regular tetrafluoroethylene-hexafluoropropylene copolymer according to claim 4, characterized by: The vacuum drying process: 60-70℃, vacuum degree 0.09 MPa.

7. A process for the preparation of a chain-regular tetrafluoroethylene-hexafluoropropylene copolymer according to claim 1, characterized by: The surfactant is a mixture of one or more of perfluoropolyether carboxylic acid ammonium, perfluorooctyl ammonium sulfonate and perfluorooctyl sulfonamide.

8. A process for the preparation of a chain-regular tetrafluoroethylene-hexafluoropropylene copolymer according to claim 1, characterized by: The molecular weight regulator is selected from at least one of methanol or diethyl malonate.

9. A process for the preparation of a chain-regular tetrafluoroethylene-hexafluoropropylene copolymer according to claim 1, characterized by: The initiator is selected from at least one of perfluorobutyryl peroxide, or perfluoro(3,6-dioxaoctanoyl) peroxide, or perfluoro(2-methyl-3-oxahexanoyl) peroxide.

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