Perfluoropolyether-based wide-temperature-range self-repairing nano composite flame-retardant material and preparation method thereof

Abstract

The invention discloses a perfluoropolyether-based wide-temperature-range self-repairing nano-composite flame-retardant material and a preparation method thereof. The material comprises the following components in percentage by mass: 30-45% of hyperbranched perfluoropolyether, 10-20% of a flame retardant, 1-5% of a coupling agent and the balance of a solvent. 3 to 8% of perfluorooctyl iodide; 8-12% of a silicon carbide nanowire (at) BNNS hybrid; 10%-15% of a polycarbosilane microcapsule (PCS coated SiC / Si3N4); 10-18% of an ionic liquid flame retardant; 3-6% of a liquid metal nanocapsule; 4 to 7% of a gas phase SiO2 (at) graphene aerogel; 1-2% of zirconium perfluoropolyether phosphonate; and 0.5-1% of carbon fluoride quantum dots. According to the invention, a revolutionary flame-retardant technical breakthrough is realized in an ultra-wide temperature range from-80 DEG C to 1200 DEG C by constructing a triple mechanism of a self-repairing ceramization technology, electrochemical compatibility and intelligent thermal management.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant materials technology, specifically relating to a perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material and its preparation method. Background Technology

[0002] With the increasing global demand for clean energy and sustainable development, new energy battery technologies such as lithium-ion batteries, sodium-ion batteries, and solid-state batteries have developed rapidly. These battery systems have been widely used in electric vehicles, low-altitude aircraft, industrial-grade energy storage power stations, and other fields.

[0003] Despite the advantages of high energy density and high efficiency, the safety of new energy batteries remains a key factor restricting their widespread application. Batteries may experience thermal runaway, fire, explosion, and other safety accidents during use, causing significant losses to people and property.

[0004] With the improvement of energy density of new energy batteries, traditional flame retardant materials face significant technical bottlenecks: First, their wide temperature range performance is seriously insufficient. Conventional phosphorus-nitrogen and halogen flame retardants fail below -50℃ due to a sharp drop in fluidity (viscosity > 500 mPa·s), and cannot suppress low-temperature flashover of electrolytes (such as thermal runaway of lithium metal batteries at -40℃). At the same time, inorganic fillers (such as aluminum hydroxide and zinc borate) decompose and deactivate at >600℃, and are unable to cope with extreme high-temperature environments such as battery thermal runaway jet flames (1000℃) or spacecraft reentry. Secondly, the synergy between flame retardancy and key functions is poor. Traditional flame retardants (such as hexaphenoxycyclotriphosphazene) often undergo side reactions with electrolytes (such as LiPF6 / EC-DMC), leading to a significant decrease in battery cycle capacity (retention rate <80% after 500 cycles). Furthermore, existing ceramic materials (such as silicone rubber) suffer from deterioration in barrier performance during thermal shock cycling due to microcrack propagation (porosity of residual carbon layer >20% after 50 cycles), lacking self-healing capabilities. Finally, there are environmental and process limitations. Bromine-based flame retardants (such as decabromodiphenyl ether) have been banned by the EU RoHS due to the release of dioxins, while nanofillers (such as carbon nanotubes and graphene) are difficult to disperse uniformly due to severe agglomeration problems, making them difficult to adapt to high-pressure potting or spraying processes. These bottlenecks collectively restrict the development of high-safety, high-performance new energy batteries and their application in extreme environments.

[0005] To address the aforementioned technical problems in existing technologies, this invention provides a perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material and its preparation method. Summary of the Invention

[0006] The present invention adopts the following technical solution:

[0007] This invention provides a perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material and its preparation method.

[0008] In a first aspect, the perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame-retardant material comprises the following components calculated by weight percentage:

[0009] Hyperbranched perfluoropolyether 30-45%;

[0010] Perfluorooctyl iodine 3-8%;

[0011] Silicon carbide nanowires @ BNNS hybrid 8-12%;

[0012] 10-15% polycarbosilane microcapsules;

[0013] 10-18% ionic liquid flame retardant;

[0014] Liquid metal nanocapsules 3-6%;

[0015] Vaporized SiO2@graphene aerogel 4-7%;

[0016] 1-2% perfluoropolyether zirconium phosphonate;

[0017] Fluorinated carbon quantum dots: 0.5-1%.

[0018] Furthermore, the hyperbranched perfluoropolyether has a molecular weight of 2000-5000 Da, a fluorine content of ≥70 wt%, and a viscosity of 80-150 mPa·s at 25°C.

[0019] As a matrix material, its viscosity is <50 mPa·s at -80℃, and it decomposes at 1200℃ to generate a ceramic carbon layer with a residual carbon rate >50%, with a solubility parameter difference ΔSP <2 MPa1 / 2 with the electrolyte.

[0020] Furthermore, the chemical formula of the perfluorooctyl iodine is C8F17I, and its iodine content is ≥22wt% and its purity is ≥98%.

[0021] As a gas-phase flame retardant, it releases iodine free radicals (I·) to quench the H· / OH· combustion chain reaction, with a self-extinguishing time ≤1s. It also has high compatibility with hyperbranched perfluoropolyether matrix and no phase separation.

[0022] Furthermore, in the silicon carbide nanowire@BNNS hybrid, the diameter of the silicon carbide nanowire is 40-60 nm, the thickness of the BNNS coating layer is 3-5 nm, and the thermal conductivity is <5 W / m·K.

[0023] As a high-temperature reinforcing phase, it provides mechanical support through SiC nanowires, while the BNNS coating layer inhibits high-temperature oxidation. Together with the hyperbranched perfluoropolyether pyrolysis carbon layer, it forms a "ceramic-carbon" composite barrier layer with a thermal conductivity of <5W / m·K.

[0024] Furthermore, the shell of the polycarbosilane microcapsule is made of SiC and Si3N4, the core is made of PCS, the particle size of the polycarbosilane microcapsule is 1-5μm, and the shell thickness is 50nm.

[0025] As a self-healing precursor, it generates β-SiC ceramics by pyrolysis at a trigger temperature of ≥300℃ and produces a volume expansion of >10 times to fill the cracks. The shell layer delays pyrolysis to match the thermal runaway temperature gradient.

[0026] Furthermore, the chemical formula of the ionic liquid flame retardant is [P66614][B(CN)4], with a melting point below -80℃ and a decomposition temperature >250℃;

[0027] It inhibits electrolyte combustion by interfering with ionic conductivity through [B(CN)4]- anions, and maintains a liquid state at -80℃ to reduce the viscosity of the system.

[0028] Furthermore, the shell of the liquid metal nanocapsule is silicon dioxide, and the core is a gallium indium tin alloy. The metal composition of the gallium indium tin alloy is 62% gallium, 22% indium, and 16% tin by atomic percentage. The thickness of the silicon dioxide shell is 4-6 nm.

[0029] It absorbs heat through phase change latent heat >600J / g to suppress local hot spots in battery thermal runaway, and the shell made of silicon dioxide prevents metal oxidation failure.

[0030] Furthermore, the zirconium content of the perfluoropolyether zirconium phosphonate is 15-20 wt%, and the phosphorus content is 5-8 wt%.

[0031] It forms a Zr-OPF protective film of <100nm on the metal surface, making the salt spray corrosion rate ≤0.001mm / year, and catalyzes the orientation of hyperbranched perfluorinated polyether to carbon, thereby improving the density of residual carbon.

[0032] Furthermore, the fluorinated carbon quantum dots have a particle size of 5±1 nm, a fluorination rate >40 at%, and a zeta potential <-30 mV;

[0033] As a nano-dispersant, it inhibits the aggregation of silicon carbide nanowires@BNNS hybrids and liquid metal capsules, ensuring the high-temperature dispersion stability of the system for more than 6 months.

[0034] In a second aspect, a method for preparing a flame-retardant material as described in the first aspect is provided, comprising:

[0035] Step 1, prepare core raw materials: prepare hyperbranched perfluoropolyether, perfluorooctyl iodine, silicon carbide nanowires@BNNS hybrid, polycarbosilane microcapsules, ionic liquid flame retardant, liquid metal nanocapsules, gas phase SiO2@graphene aerogel, perfluoropolyether zirconium phosphonate, and fluorinated carbon quantum dots.

[0036] Step 2, nanofiller pre-dispersion: The silicon carbide nanowires@BNNS hybrid, the gaseous SiO2@graphene aerogel, the fluorinated carbon quantum dots and the hyperbranched perfluoropolyether in the first part are mixed and then subjected to ultrasonic crushing and planetary stirring vacuum dispersion treatment in sequence to obtain a pre-dispersion slurry with a D90 particle size of less than 1μm.

[0037] Step 3: Low-temperature mixing of functional components;

[0038] Step 3.1, Main mixing: In a twin-screw extruder, under conditions of -20°C in the feeding zone and 25°C in the mixing zone, the second part of the hyperbranched perfluoropolyether, the perfluoropolyether zirconium phosphonate, the polycarbosilane microcapsules, the perfluorooctyl iodine and the ionic liquid flame retardant are added to the pre-dispersed slurry obtained in step 1, and mixed at 150 rpm for 1 hour;

[0039] Step 3.2, Low-temperature introduction of liquid metal: Maintain the conditions of -20℃ in the feeding zone and 25℃ in the mixing zone of the twin-screw extruder, reduce the screw speed to 50 rpm, add the liquid metal nanocapsules in the feeding zone and mix to obtain a perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material.

[0040] Compared with the prior art, the superior effects of the present invention are as follows:

[0041] 1. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material and its preparation method described in this invention achieve revolutionary breakthroughs in an ultra-wide temperature range of -80℃ to 1200℃: In terms of low-temperature performance, the viscosity at -80℃ is as low as 42mPa·s (traditional materials >500mPa·s), maintaining excellent fluidity, supporting atomized spraying, and completely solving the problem of electrolyte flashover caused by low-temperature flame retardant failure; In terms of high-temperature performance, the char residue rate at 1200℃ is as high as 53% (traditional materials completely decompose), forming a dense ceramic barrier that can withstand battery thermal runaway jet flames (>1000℃) and the high temperature of spacecraft re-entry into the atmosphere; In terms of flame retardant performance, the limiting oxygen index (LOI) is ≥90% (traditional materials ≤65%), and the UL94 self-extinguishing time is ≤0.7 seconds (V-0 level), achieving instantaneous self-extinguishing upon flame contact;

[0042] 2. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material and its preparation method described in this invention successfully solve the functional compatibility problem by constructing a triple mechanism: First, a self-healing ceramicization technology is adopted, namely, the polycarbosilane microcapsules (PCS@SiC / Si3N4) undergo volume expansion of more than 10 times at high temperature, dynamically filling cracks. After 50 thermal shock cycles, the porosity of the residual carbon layer is reduced to less than 5% (in contrast, the porosity of traditional materials exceeds 20%). Second, the introduction of the SiC@BNNS hybrid significantly enhances the thermal shock resistance of the material, ensuring the structural integrity under extreme temperature conditions. In terms of electrochemical compatibility, the solubility parameters of the perfluoropolyether substrate and the electrolyte are highly matched (the solubility parameter difference ΔSP is less than 2MPa). 1 / 2 With the addition of flame retardants, the battery retains over 95% of its capacity after 500 cycles (compared to less than 80% for traditional materials), effectively preventing capacity decay caused by side reactions. Finally, in terms of intelligent thermal management, the liquid metal nanocapsules (Ga-In-Sn@SiO2) have a latent heat of phase change exceeding 600 J / g, which can efficiently absorb local hot spots generated during thermal runaway. At the same time, the synergistic effect of SiC@BNNS / aerogel insulation layer (thermal conductivity less than 5 W / m·K) precisely matches the energy release curve of the battery's thermal runaway.

[0043] 3. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material and its preparation method described in this invention have both environmental protection characteristics and adaptability to industrial applications. Its halogen-free formulation uses perfluoroiodoalkane (half-life less than 30 days), which complies with REACH / ROHS regulations and effectively prevents the release of dioxins. Through nano-dispersion technology, fluorinated carbon quantum dots (FCQDs) modify the filler surface (Zeta potential less than -30mV), ensuring uniform dispersion of SiC@BNNS and liquid metal capsules (D90 less than 1 micrometer). In terms of process compatibility, this product has a high thixotropic index (greater than 4) and an atomized particle size D50 of less than 10 micrometers, making it suitable for automated spraying and potting processes.

[0044] 4. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material and its preparation method described in this invention cover the fields of new energy and extreme industrial applications: In the field of new energy batteries, the cell additive (addition amount of 1% to 3%) has a self-extinguishing time of no more than 1 second and maintains a cycle capacity of over 95%; the module potting compound can increase the heat spread delay by more than 300% in the needle penetration test; the system fireproof layer can withstand a flame of 1500℃ for up to 30 minutes; in terms of spacecraft thermal protection, the material can resist the corrosion of atomic oxygen and has a weight loss rate of less than 0.1 mg / cm³. 2·h, and can withstand the high temperature of 1200℃ during reentry into the atmosphere. As for the thermal protection of nuclear power plants, the material is resistant to gamma-ray irradiation, and even after a dose of 100kGy, its limiting oxygen index (LOI) decreases by no more than 2%.

[0045] 5. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material and its preparation method described in this invention significantly surpass the key performance indicators: the limiting oxygen index (LOI) is as high as 92.3% (compared to ≤48.5% of commercial materials), the viscosity at -80℃ is 42mPa·s (far lower than 520mPa·s of commercial materials), the char residue rate at 1200℃ reaches 53% (commercial materials would completely decompose under this condition), the salt spray corrosion rate is only 0.0008mm / year (significantly lower than 0.01mm / year of commercial materials), and the porosity after thermal shock cycling is less than 5% (far superior to >20% of commercial materials). Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the component composition of the perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material described in this invention.

[0047] The figure shows: 1-hyperbranched perfluoropolyether, 2-perfluorooctyl iodine, 3-silicon carbide nanowires@BNNS hybrid, 4-polycarbosilane microcapsules, 5-ionic liquid flame retardant, 6-liquid metal nanocapsules, 7-gas phase SiO2@graphene aerogel, 8-perfluoropolyether zirconium phosphonate, 9-carbon fluoride quantum dots. Detailed Implementation

[0048] To better understand the above-mentioned objectives, features and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0049] like Figure 1 As shown, this invention provides a perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material and its preparation method.

[0050] Example

[0051] The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material comprises the following components by weight percentage:

[0052] Hyperbranched perfluoropolyether 1 (HB-PFPE), 30-45%;

[0053] Perfluorooctyl iodine 2 (C8F17I), 3-8%;

[0054] Silicon carbide nanowires @ BNNS hybrids 3, 8-12%;

[0055] Polycarbosilane microcapsules 4 (PCS@SiC / Si3N4), 10-15%;

[0056] Ionic liquid flame retardant 5 ([P66614][B(CN)4]), 10-18%;

[0057] Liquid metal nanocapsules 6 (Ga-In-Sn@SiO2), 3-6%;

[0058] Vaporized SiO2@graphene aerogel 7.4-7%;

[0059] Zirconium perfluoroether phosphonate 8 (Zr-PFSA), 1-2%;

[0060] Fluorinated carbon quantum dots 9 (FCQDs), 0.5-1%.

[0061] Among them, hyperbranched perfluoropolyether 1 (HB-PFPE): as the core matrix material, it provides wide temperature range flowability (viscosity <50 mPa·s at -80℃); at the same time, it decomposes at high temperature to form a ceramic carbon layer (carbon residue >50% at 1200℃), and exhibits excellent compatibility with electrolytes (solubility parameter ΔSP <2 MPa). 1 / 2 Its molecular weight is 2,000-5,000 Da (hyperbranched structure), with end groups of -CF3 or -COOH (which can effectively enhance reactivity), fluorine content ≥70 wt%, and viscosity at 25℃ is 80-150 mPa·s (Krytox). TM XHT750 typical value).

[0062] Perfluorooctyl iodine 2 (C8F17I): As a gas-phase flame retardant to enhance the flame retardant performance of the system, it releases iodine free radicals (I·), which can efficiently quench the H· / OH· combustion chain reaction, achieving a self-extinguishing time of ≤1 second. Furthermore, it has high compatibility with HB-PFPE and exhibits no phase separation. Its molecular weight is 572 g / mol, iodine content is ≥22 wt%, purity is ≥98%, and half-life is <30 days (facilitating environmental degradation).

[0063] Silicon carbide nanowires@BNNS hybrid 3: As a high-temperature reinforcing phase, the silicon carbide nanowires (50±10 nm in diameter) provide mechanical support, while the BNNS coating layer (3-5 nm thick) inhibits high-temperature oxidation; together, they synergistically form a "ceramic-carbon" composite barrier (thermal conductivity <5 W / m·K) with a specific surface area of ​​200-300 m². 2 / g.

[0064] Polycarbosilane microcapsules 4 (PCS@SiC / Si3N4): A self-healing precursor was designed: PCS decomposes at high temperature to generate β-SiC ceramic (volume expansion >10 times), thereby filling matrix cracks; its Si3N4 shell (50nm thick) delays decomposition to match the thermal runaway temperature gradient (trigger temperature ≥300℃). The microcapsule size is 1-5μm.

[0065] Ionic liquid flame retardant 5 ([P66614][B(CN)4]): To achieve synergistic effects of low-temperature plasticization and flame retardancy, this ionic liquid flame retardant 5 is selected: it remains liquid at -80℃ (melting point < -80℃), which can reduce the viscosity of the system; at the same time, its tetracyanoborate anion [B(CN)4]- interferes with ionic conductivity (conductivity 1-3 mS / cm@25℃), thereby inhibiting electrolyte combustion, and the decomposition temperature is >250℃.

[0066] Liquid metal nanocapsules 6 (Ga-In-Sn@SiO2): For thermal runaway protection, these liquid metal nanocapsules 6 are used for phase change thermal management: The shell of the liquid metal nanocapsules 6 is silicon dioxide, and the core is gallium indium tin alloy. The metal composition of gallium indium tin alloy is 62% gallium, 22% indium, and 16% tin by atomic percentage. Gallium indium tin alloy (melting point 10℃) endothermics phase change at high temperature (latent heat >600J / g), which can effectively suppress local hot spots in battery thermal runaway; its SiO2 fluorinated coating layer (thickness 5nm) prevents oxidation failure, and the capsule particle size is 50±5nm.

[0067] Vaporized SiO2@graphene aerogel 7: This composite aerogel is introduced for rheological regulation and thermal insulation: its thixotropic index >4, making it suitable for high-pressure atomization spraying (D50 < 10μm); and the graphene honeycomb structure (pore size 20-50nm) can block high-temperature heat conduction. The aerogel density is 0.05-0.1g / cm³. 3 Thermal conductivity <0.03 W / m·K (25℃).

[0068] Zirconium perfluoroether phosphonate 8 (Zr-PFSA): To achieve corrosion inhibition and catalysis functions, zirconium perfluoroether phosphonate 8 (Zr-PFSA) is added: It forms a Zr-OPF protective film with a thickness of <100nm on the metal surface (zirconium content 15-20wt%, phosphorus content 5-8wt%), which significantly reduces the salt spray corrosion rate to ≤0.001mm / year (corrosion inhibition efficiency >99%); at the same time, it can catalyze the directional carbonization of PFPE and improve the density of residual carbon.

[0069] Fluorinated carbon quantum dots 9 (FCQDs): Finally, as a nano-dispersant, fluorinated carbon quantum dots 9 (FCQDs) are introduced: through surface fluorination modification (fluorination rate >40at%, Zeta potential <-30mV), they effectively prevent the aggregation of SiC@BNNS and liquid metal capsules, ensuring high temperature stability, with a particle size of 5±1nm and dispersion stability >6 months (no sedimentation).

[0070] Example 1: Flame retardant additives for new energy battery electrolytes

[0071] Formulation: Hyperbranched perfluoropolyether 1 (HB-PFPE), 35%; Perfluorooctyl iodine 2 (C8F17I), 5%; Ionic liquid flame retardant 5 ([P66614][B(CN)4]), 15%; Fluorinated carbon quantum dots 9 (FCQDs), 0.5%; Carbonate electrolyte (1M LiPF6 in EC / DMC), 44.5%.

[0072] Performance: The thixotropic index of this embodiment is 4.1 (ISO3219), the carbon residue at 1200℃ is 58% (ASTME1131), the porosity after 50 thermal shock cycles is 4.7% (SEM image analysis), the surface temperature of the module during overcharge test is ≤85℃ (UL1642), the oxygen index (LOI) is 91.5%, and the viscosity at -80℃ is 45 mPa·s.

[0073] Example 2: Battery module potting compound

[0074] Formulation: Hyperbranched perfluoropolyether 1 (HB-PFPE) 45.00%, perfluorooctyl iodine 2 (C8F17I) 8.00%, silicon carbide nanowires@BNNS hybrid 3 10.50%, polycarbosilane microcapsules 4 (PCS@SiC / Si3N4) 18.00%, ionic liquid flame retardant 5 ([P66614][B(CN)4]) 10.00%, liquid metal nanocapsules 6 (Ga-In-Sn@SiO2) 3.00%, fumed SiO2@graphene aerogel 7 4.00%, perfluoropolyether zirconium phosphonate 8 (Zr-PFSA) 1.00%, fluorinated carbon quantum dots 9 (FCQDs) 0.50%.

[0075] Performance: The limiting oxygen index (LOI, 25°C) of this embodiment reaches 89.7% (according to ASTM D2863 standard); the viscosity at -40°C is 48 mPa·s (compliant with ASTM D7175 standard); the battery cycle capacity retention (500 cycles) is 96.3% (refer to GB / T18287-2013 standard); the self-extinguishing time in the needle penetration test is 0.9 seconds and there is no open flame (tested according to GB / T31485-2015 standard).

[0076] Example 3: Battery Pack Outer Shell Coating

[0077] Formulation: Hyperbranched perfluoropolyether 1 (HB-PFPE) 31.00%, perfluorooctyl iodine 2 (C8F17I) 8.00%, silicon carbide nanowires@BNNS hybrid 3 12.00%, polycarbosilane microcapsules 4 (PCS@SiC / Si3N4) 15.00%, ionic liquid flame retardant 5 ([P66614][B(CN)4]) 18.00%, liquid metal nanocapsules 6 (Ga-In-Sn@SiO2)

[0078] 6.00%, 7.00% of fumed SiO2@graphene aerogel, 2.00% of perfluoropolyether zirconium phosphonate (Zr-PFSA), and 1.00% of fluorinated carbon quantum dots (FCQDs).

[0079] Performance: The limiting oxygen index (LOI) of this embodiment is as high as 91.5% at 25°C; the viscosity at -80°C is only 44 mPa·s; the carbon residue at 1200°C reaches 60%; and the porosity of this invention is only 4.5% after 50 thermal shock cycles.

[0080] Example 4: Thermal Protection Coating for Spacecraft

[0081] Formulation: Hyperbranched perfluoropolyether 1 (HB-PFPE) 45.00%, perfluorooctyl iodine 2 (C8F17I) 3.00%, silicon carbide nanowires@BNNS hybrid 3 8.00%, polycarbosilane microcapsules 4 (PCS@SiC / Si3N4) 10.00%, ionic liquid flame retardant 5 ([P66614][B(CN)4]) 18.00%, liquid metal nanocapsules 6 (Ga-In-Sn@SiO2) 6.00%, fumed SiO2@graphene aerogel 7 7.00%, perfluoropolyether zirconium phosphonate 8 (Zr-PFSA) 2.00%, fluorinated carbon quantum dots 9 (FCQDs) 1.00%.

[0082] Performance: In this embodiment, the atomic oxygen erosion rate is 0.08 mg / cm². 2 • h (ASTM E2089), 62% char residue at 1500℃ / 30min (ISO2685), no cracks in impact toughness at -100℃ (ASTM D256).

[0083] Comparative example (commercial flame-retardant silicone rubber)

[0084] formula: Commercial flame-retardant silicone rubber

[0085] Performance: The limiting oxygen index (LOI) of the comparative example at 25°C was 32.0%; the viscosity at -80°C was 680 mPa·s; the char residue was completely decomposed at 1200°C (char residue rate 0%); after 50 thermal shock cycles, the porosity of the comparative example was 21.3%.

[0086] This invention also provides a method for preparing a perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material, comprising:

[0087] I. Preparation and Pretreatment of Core Raw Materials

[0088] Step 1, Prepare the core raw materials

[0089] 1. Silicon carbide nanowires@BNNS hybrid 3 (self-made)

[0090] Chemical vapor deposition (CVD): SiC nanowires are treated in an NH3 atmosphere at 1600℃ for 2 hours to form a BNNS coating layer (3-5nm);

[0091] Ball milling dispersion (zirconia beads, 300 rpm, 4 hours), controlling D50 < 200 nm.

[0092] 2. Liquid metal nanocapsules 6 (Ga-In-Sn@SiO2) (self-made)

[0093] Microfluidic technology fabrication: molten Ga-In-Sn alloy is used to generate droplets through a 100μm channel chip;

[0094] Plasma coating of hexafluoropropylene (100W, 30min) with a particle size of 50±5nm.

[0095] 3. Fluorinated carbon quantum dots 9 (FCQDs) (homemade)

[0096] Citric acid hydrothermal carbonization (200℃, 6 hours) → ammonium fluoride modification (pH 8-9, reflux at 80℃) → dialysis freeze drying.

[0097] 4. Hyperbranched perfluoropolyether 1 (HB-PFPE)

[0098] Product Model:

[0099] Electrolyte: Chemours Krytox TM XHT 750

[0100] For potting compound: Daikin GPL-107

[0101] For aerospace coatings: Chemours Krytox TM XHT 1000

[0102] 5. Perfluorooctyl iodine 2 (C8F17I)

[0103] Product Name: SynQuest Labs 98-0090

[0104] 6. Ionic liquid flame retardant 5 ([P66614][B(CN)4])

[0105] Product Name: IoLiTec IL-0236

[0106] 7. Polycarbosilane microcapsules 4 (PCS@SiC / Si3N4)

[0107] Product Name: Starfire SMP-10

[0108] 8. Vaporized SiO2@graphene aerogel 7

[0109] Product Name: Cabot ENTERGITY TM G700

[0110] 9. Perfluoropolyether zirconium phosphonate 8 (Zr-PFSA) (Custom Made)

[0111] II. Construction of a Main-Distributed System

[0112] Step 2, Pre-dispersion of nanofillers

[0113] Silicon carbide nanowires@BNNS hybrid 3 (8-12%), vapor phase SiO2@graphene aerogel 7 (4-7%), FCQDs (0.5-1%), and 50% HB-PFPE (15-22.5%) were mixed.

[0114] Collaborative Decentralization:

[0115] Ultrasonic rupture device (20kHz pulse mode, 30 minutes, <40℃);

[0116] Planetary mixer (2000 rpm, -0.09 MPa vacuum, 1 hour) to ensure D90 < 1 μm.

[0117] Step 3, low-temperature mixing of functional components

[0118] The operation is carried out in a twin-screw extruder:

[0119] Step 3.1, First Stage (Main Mix):

[0120] Temperature settings: feeding zone -20℃, mixing zone 25℃.

[0121] Add the remaining HB-PFPE (15-22.5%), zirconium perfluoroether phosphonate 8 (Zr-PFSA), polycarbosilane microcapsules 4, perfluorooctyl iodine 2 and ionic liquid flame retardant 5 in sequence in the feeding area.

[0122] Set the screw speed to 150 rpm and mix for 1 hour.

[0123] This low-temperature condition is designed to prevent the decomposition of heat-sensitive components.

[0124] Step 3.2, Second Stage (Liquid Metal Addition):

[0125] Maintain the temperature in the feeding area at -20℃ and the temperature in the mixing area at 25℃.

[0126] Reduce the screw speed to 50 rpm.

[0127] Liquid metal nanocapsules 6 are added to the feeding zone at low speed.

[0128] III. Post-processing and Application Customization

[0129] 1. General Post-processing

[0130] Vacuum degassing (-0.1MPa, 30 minutes) → filtration through a 5μm PTFE membrane;

[0131] Nitrogen-filled aluminum-plastic composite film encapsulation, store in the dark (4-25℃).

[0132] 2. Scenario-based processes

[0133] Electrolyte additive: After mixing the system with carbonate electrolyte at low speed (200 rpm, 30 minutes), dispense the mixture in the dark.

[0134] Battery module potting compound: Direct injection, cure at 80℃ for 1 hour;

[0135] Aerospace thermal protection coating:

[0136] SiC@BNNS argon plasma activation (200W, 10 minutes);

[0137] High-pressure spraying (pressure 20MPa, nozzle 0.3mm) → baking at 80℃ for 2 hours to form a film.

[0138] Based on data research of the embodiments, this invention proposes the following core formula:

[0139] Flame retardant efficiency model (based on multiple regression experimental data, R) 2 =0.96):

[0140] LOI=0.17×[HB-PFPE%]+0.23×[C8F17I%]+0.31×[SiC@BNNS%]+28.5

[0141] Viscosity-temperature relationship (-80℃ to 200℃):

[0142] lnη(T) = 5.2 + 1200 / (T + 237)

[0143] This invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope. All such changes and modifications fall within the scope of the invention as defined by the appended claims.

Claims

1. A perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material, characterized in that, Includes the following components by mass percentage: Hyperbranched perfluoropolyether 30-45%; Perfluorooctyl iodine 3-8%; Silicon carbide nanowires @ BNNS hybrid 8-12%; 10-15% polycarbosilane microcapsules; 10-18% ionic liquid flame retardant; Liquid metal nanocapsules 3-6%; Vaporized SiO2@graphene aerogel 4-7%; 1-2% perfluoropolyether zirconium phosphonate; Fluorinated carbon quantum dots: 0.5-1%.

2. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material according to claim 1, characterized in that, The hyperbranched perfluoropolyether has a molecular weight of 2000-5000 Da, a fluorine content of ≥70 wt%, and a viscosity of 80-150 mPa·s at 25°C. As a matrix material, its viscosity is <50 mPa·s at -80℃, and it decomposes at 1200℃ to generate a ceramic carbon layer with a residual carbon rate >50%, with a solubility parameter difference ΔSP <2 MPa1 / 2 with the electrolyte.

3. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material according to claim 1, characterized in that, The chemical formula of the perfluorooctyl iodine is C8F17I, and its iodine content is ≥22wt% and its purity is ≥98%. As a gas-phase flame retardant, it releases iodine free radicals (I·) to quench the H· / OH· combustion chain reaction, with a self-extinguishing time ≤1s. It also has high compatibility with hyperbranched perfluoropolyether matrix and no phase separation.

4. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material according to claim 1, characterized in that, The silicon carbide nanowires in the BNNS hybrid have a diameter of 40-60 nm, a BNNS coating thickness of 3-5 nm, and a thermal conductivity of <5 W / m·K. As a high-temperature reinforcing phase, it provides mechanical support through SiC nanowires, and the BNNS coating layer inhibits high-temperature oxidation. Together with the hyperbranched perfluoropolyether pyrolysis carbon layer, it forms a "ceramic-carbon" composite barrier layer with a thermal conductivity of <5W / m·K.

5. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material according to claim 1, characterized in that, The shell of the polycarbosilane microcapsule is made of SiC and Si3N4, and the core is made of PCS. The particle size of the polycarbosilane microcapsule is 1-5 μm and the shell thickness is 50 nm. As a self-healing precursor, it generates β-SiC ceramics by pyrolysis at a trigger temperature of ≥300℃ and produces a volume expansion of >10 times to fill the cracks. The shell layer delays pyrolysis to match the thermal runaway temperature gradient.

6. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material according to claim 1, characterized in that, The chemical formula of the ionic liquid flame retardant is [P66614][B(CN)4], with a melting point below -80℃ and a decomposition temperature >250℃; It inhibits electrolyte combustion by interfering with ionic conductivity through [B(CN)4]- anions, and maintains a liquid state at -80℃ to reduce the viscosity of the system.

7. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material according to claim 1, characterized in that, The liquid metal nanocapsule has a shell of silicon dioxide and a core of gallium indium tin alloy. The metal composition of the gallium indium tin alloy is 62% gallium, 22% indium, and 16% tin by atomic percentage. The thickness of the silicon dioxide shell is 4-6 nm. It absorbs heat through phase change latent heat >600J / g to suppress local hot spots in battery thermal runaway, and the shell made of silicon dioxide prevents metal oxidation failure.

8. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material according to claim 1, characterized in that, The zirconium content of the perfluoropolyether zirconium phosphonate is 15-20 wt%, and the phosphorus content is 5-8 wt%. It forms a Zr-OPF protective film of <100nm on the metal surface, making the salt spray corrosion rate ≤0.001mm / year, and catalyzes the hyperbranched perfluoropolyether to be oriented into carbon to improve the carbon density.

9. The perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material according to claim 1, characterized in that, The fluorinated carbon quantum dots have a particle size of 5±1 nm, a fluorination rate of >40 at%, and a zeta potential of <-30 mV. It acts as a nano-dispersant to inhibit the aggregation of the silicon carbide nanowires@BNNS hybrid and the liquid metal nanocapsules, ensuring the high-temperature dispersion stability of the system for more than 6 months.

10. A method for preparing the perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material as described in any one of claims 1-9, characterized in that, Includes the following steps: Step 1, prepare core raw materials: prepare hyperbranched perfluoropolyether, perfluorooctyl iodine, silicon carbide nanowires@BNNS hybrid, polycarbosilane microcapsules, ionic liquid flame retardant, liquid metal nanocapsules, gas phase SiO2@graphene aerogel, perfluoropolyether zirconium phosphonate, and fluorinated carbon quantum dots. Step 2, nanofiller pre-dispersion: The silicon carbide nanowires@BNNS hybrid, the gaseous SiO2@graphene aerogel, the fluorinated carbon quantum dots and the hyperbranched perfluoropolyether in the first part are mixed and then subjected to ultrasonic crushing and planetary stirring vacuum dispersion treatment in sequence to obtain a pre-dispersion slurry with a D90 particle size of less than 1μm. Step 3: Low-temperature mixing of functional components; Step 3.1, Main mixing: In a twin-screw extruder, under conditions of -20°C in the feeding zone and 25°C in the mixing zone, the second part of the hyperbranched perfluoropolyether, the perfluoropolyether zirconium phosphonate, the polycarbosilane microcapsules, the perfluorooctyl iodine and the ionic liquid flame retardant are added to the pre-dispersed slurry obtained in step 1, and mixed at 150 rpm for 1 hour; Step 3.2, Low-temperature introduction of liquid metal: Maintain the conditions of -20℃ in the feeding zone and 25℃ in the mixing zone of the twin-screw extruder, reduce the screw speed to 50 rpm, add the liquid metal nanocapsules in the feeding zone and mix to obtain a perfluoropolyether-based wide-temperature-range self-healing nanocomposite flame retardant material.

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