A polyvinyl fluoride film, a method for preparing the same, and an application thereof

Abstract

This invention discloses a polyvinyl fluoride (PVC) film, characterized in that: the film-forming formula of the PVC film comprises 100 parts of PVC resin and 0.5-2 parts of a nucleating agent; the PVC resin is selected from at least one of PVC homopolymer or copolymer of PVC and other fluorinated monomers, the PVC resin has a weight-average molecular weight of 450,000-1,200,000, a molecular weight distribution of 1.1-2.0, a crystallinity of 40%-60%, and a crystal size of 4.0-10.0 nm; the nano-nucleating agent is inorganic nanoparticles with a particle size of 1-60 nm and a specific surface area of ​​10-800 m². 2 / g. The polyvinyl fluoride film of the present invention has excellent weather resistance, tear resistance and helium barrier properties, and can be used as a protective layer or barrier layer for aircraft composite materials, thereby effectively extending the service life of aircraft.

Description

Technical Field

[0001] This invention relates to the field of polymer technology, specifically to a polyvinyl fluoride film, its preparation method, and its application. Background Technology

[0002] The structural composition and performance requirements of aircraft materials are key factors in ensuring the safe and efficient operation of aircraft. The stratosphere, where aircraft operate, presents complex and unique environmental requirements, including large diurnal temperature variations, high radiation, high ozone levels, and other challenging conditions, placing stringent demands on the aging conditions of aircraft materials. During the actual preparation, assembly, and transportation of aircraft materials, they undergo environmental tests such as kneading, friction, folding, curling, dragging, and prolonged continuous stress. The areal density and strength of the materials directly affect critical indicators such as the aircraft's hovering time, load capacity, and flight safety. Therefore, materials must possess properties such as lightweight, high strength, good aging resistance, excellent barrier properties, and resistance to kneading. Thus, aircraft materials represent a significant challenge in this field.

[0003] In existing technologies, fluoropolymers are commonly used as weather-resistant layers in aircraft composite materials due to their excellent weather resistance. Furthermore, their good gas barrier properties also serve as an auxiliary gas barrier in aircraft materials. However, because fluoropolymers themselves have insufficient resistance to tearing, microcracks, holes, or localized damage inevitably occur on the surface during material processing and subsequent use, leading to gas leaks. Long-term gas leaks and material aging can cause significant damage to the structural integrity of the aircraft, increasing safety risks. Traditional repair methods typically require descent of the aircraft to the ground for manual repairs, which is not only time-consuming and labor-intensive but may also require releasing internal helium, increasing repair costs and complexity.

[0004] Chinese patent CN111016363A discloses a rub-resistant flexible composite material, wherein the anti-aging layer material is a polyvinyl fluoride film or a PVDF (polyvinylidene fluoride) film with a thickness of 12-50 μm and an areal density of 15-80 g / m³. 2 This method adds a layer of thermoplastic polyurethane film as a buffer layer, which provides both barrier properties and flexibility to cushion the impact of external forces on the barrier and anti-aging layers, thus offering protection. However, the addition of the buffer layer increases the already complex composite material structure from 7 layers to 9 layers, increasing the difficulty and complexity of the material preparation process. More steps and more precise control are needed to ensure the correct bonding and stable performance of each layer. This not only increases the difficulty of production but may also lead to low production efficiency.

[0005] In summary, existing weather-resistant materials have poor resistance to rubbing, and rubbing can easily cause leaks, which seriously affect the service life of aircraft. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a polyvinyl fluoride film that possesses excellent weather resistance, tear resistance, and helium barrier properties. It can be used as a protective or barrier layer for aircraft composite materials, thereby effectively extending the service life of aircraft composite materials.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A polyvinyl fluoride (PVC) film, wherein the film-forming formula comprises 100 parts of PVC resin and 0.5-2 parts of a nucleating agent; the PVC resin is selected from at least one of PVC homopolymer or copolymer of PVC and other fluorinated monomers, the PVC resin having a weight-average molecular weight of 450,000-1,200,000, a molecular weight distribution of 1.1-2.0, a crystallinity of 40%-60%, and a crystal size of 4.0-10.0 nm; the nucleating agent is surface-modified nano-inorganic particles with a particle size of 1-60 nm and a specific surface area of ​​10-800 m². 2 / g.

[0009] The areal density of the polyvinyl fluoride film of the present invention is 20-100 g / m³. 2 Helium permeability < 1.5 L / m 2 After 24 hours, the ultraviolet light transmittance is <0.1%, the film can withstand 100-360 rubs, has a tensile strength >70MPa, and an elongation at break >90%. Furthermore, the areal density of the polyvinyl fluoride film is 20-60 g / m³. 2 Helium permeability < 1.0 L / m 2 24h, UV transmittance <0.05%, rub resistance 120-360 times, tensile strength >80MPa, elongation at break >100%.

[0010] Polyvinyl fluoride (PVC) resin is the raw material for PVC films. The weight-average molecular weight, molecular weight distribution, crystallinity, and crystal size of the PVC resin are closely related to the film's properties. This invention, in order to improve the rub resistance of PVC films, selects PVC resins with specific properties as raw materials. Firstly, the PVC resin is required to have a suitable weight-average molecular weight and molecular weight distribution, resulting in more uniform lengths of the PVC molecular chains. This helps to enhance the cohesive force of the PVC film, thereby improving its strength and toughness. Secondly, selecting PVC resins with suitable crystallinity and crystal size results in a more compact and ordered molecular arrangement within the PVC molecular chains. This effectively improves the mechanical strength of the PVC film and helps it better disperse energy upon impact, reducing crack initiation and propagation, thus effectively enhancing the film's toughness. The tightly packed molecular chains of the PVC film described in this invention are more difficult for chemical substances to penetrate and damage, thereby improving its helium barrier properties.

[0011] Preferably, the polyvinyl fluoride resin has a weight-average molecular weight of 500,000 to 1,100,000, a molecular weight distribution of 1.1 to 1.8, a crystallinity of 42% to 55%, and a crystal size of 4.5 to 9.0 nm; more preferably, the polyvinyl fluoride resin has a weight-average molecular weight of 550,000 to 1,000,000, a molecular weight distribution of 1.1 to 1.5, a crystallinity of 45% to 55%, and a crystal size of 5.3 to 8.4 nm.

[0012] When the polyvinyl fluoride resin is a copolymer of vinyl fluoride and other comonomers, the weight percentage of vinyl fluoride in the polyvinyl fluoride resin is ≥75%. The other comonomers are unsaturated monomers with monoolefin bonds, including propylene ester monomers, fluorinated olefin monomers, or non-fluorinated olefin monomers. Specifically, the propylene ester monomers are selected from at least one of butyl methacrylate, methacrylic acid, butyl acrylate, ethyl acrylate, acrylic acid, and methacrylic acid; the fluorinated olefin monomers are selected from at least one of hexafluoropropylene, vinylidene fluoride, trifluorochloroethylene, and tetrafluoroethylene; and the non-fluorinated olefin monomers are selected from at least one of ethylene, propylene, isobutylene, vinyl chloride, vinyl butyric acid, and vinyl acetate.

[0013] Preferably, the surface-modified nano-inorganic particles have a particle size of 1–40 nm and a specific surface area of ​​60–800 m². 2 / g.

[0014] The inorganic nanoparticles are selected from at least one of nano-silica, nano-zinc oxide, nano-calcium carbonate, and nano-calcium sulfate.

[0015] Furthermore, the inorganic nanoparticles are surface-modified with a long-chain fluorinated silane coupling agent, wherein the long-chain fluorinated silane coupling agent is selected from at least one of perfluoroolefin-based trimethoxysilane, perfluoroolefin-based triethoxysilane, perfluoropolyether-based trimethoxysilane, perfluoropolyether-based triethoxysilane, and diperfluoropolyether-based tetraethoxysilane.

[0016] This invention utilizes long-chain fluorinated silanes as modifiers for surface grafting modification, introducing long-chain fluorinated groups onto the surface of inorganic nanoparticles. This significantly improves the dispersibility and compatibility of the inorganic nanoparticles in the formulation system. The introduction of fluorinated groups increases the polarity of the inorganic nanoparticles, improving their compatibility with polyvinyl fluoride resin. The introduction of long carbon chains enhances the entanglement between nano-silica and polyvinyl fluoride molecular chains, further improving compatibility with polyvinyl fluoride resin and preventing precipitation during film formation. When the number of carbon atoms in the fluorinated silane is low, the inorganic nanoparticles are highly active and easily precipitate at the extruder die. Excessively long carbon chains may lead to enhanced intermolecular interactions in the coupling agent, easily causing cross-linking and affecting the dispersion stability of the inorganic nanoparticles in the system. The long-chain fluorinated silane coupling agent has 6-17 carbon atoms, more preferably 6-12.

[0017] The polyvinyl fluoride film of the present invention further comprises fillers, light stabilizers, and pigments. The fillers are selected from at least one of titanium dioxide, calcium carbonate, silicates, zinc oxide, aluminum oxide, silicon nitride, and zirconium oxide, with an average particle size of 0.1–5 μm; the light stabilizers are oligomeric hindered amine light stabilizers with a molecular weight of 1000–4000; the pigments are at least one of carbon black, iron oxide black, copper chromium black, iron chromium black, composite titanium yellow, bismuth yellow, titanium nickel yellow, composite titanium red, cadmium red, or iron red, and are mainly used for coloring polyvinyl fluoride films.

[0018] More specifically, the film-forming formula of the polyvinyl fluoride film of the present invention includes: 100 parts of polyvinyl fluoride resin; 0.5 to 2 parts of nano-nucleating agent; 10 to 30 parts of filler; 0.5 to 3 parts of light stabilizer; and 0 to 2 parts of pigment.

[0019] The present invention also provides a method for preparing any of the above-described polyvinyl fluoride films, the method comprising the following steps:

[0020] S1: A film stretching slurry is formed by mixing polyvinyl fluoride resin, a latent solvent, a nano-nucleating agent, a filler, a light stabilizer, and a pigment.

[0021] S2: The film stretching slurry is added to an extruder and subjected to high-temperature extrusion casting, biaxial stretching, and devolatilization to form a polyvinyl fluoride film.

[0022] Specifically, during biaxial stretching, the longitudinal stretching shrinkage rate is 2%–10%; the transverse stretching shrinkage rate is 2%–15%; the devolatilization temperature is 150–190℃; and the setting temperature is 170–220℃. Preferably, the longitudinal stretching shrinkage rate is 2%–5%; the transverse stretching shrinkage rate is 2%–10%; the devolatilization temperature is 170–190℃; and the setting temperature is 180–200℃.

[0023] The surface-modified inorganic nanoparticles of this invention, under specific preparation process conditions, enhance the growth rate and crystallinity of polyvinyl fluoride (PVC) crystals by controlling the nucleation rate. This effectively controls the crystal size, reduces the difference in mechanical strength between the crystalline and amorphous regions of the PVC film, and achieves long-chain segment linkage between the crystalline and amorphous regions. This provides sufficient deformation space for the PVC molecular chains during rubbing tests, giving the PVC film both strength and toughness, thereby improving its rubbing resistance and barrier properties. Simultaneously, the hydroxyl groups on the surface of the modified inorganic nanoparticles form hydrogen bonds, increasing intermolecular interactions and further enhancing the mechanical properties of the PVC film. Utilizing the reversibility of hydrogen bonds, the PVC film can deform and absorb energy when subjected to rubbing forces, thus exhibiting excellent rubbing resistance.

[0024] This invention also provides an application of the aforementioned polyvinyl fluoride (PVC) film, which is used as a protective or barrier layer in aircraft composite materials. As a protective or barrier layer material for aircraft composite materials, lower areal density, helium transmittance, and ultraviolet transmittance are preferable; higher tumble resistance, tensile strength, and elongation at break are preferable. The PVC film of this invention, while possessing low areal density, excellent helium barrier properties, and ultraviolet barrier properties, exhibits excellent tumble resistance, maintaining good helium barrier performance before and after tumbling. This significantly improves the barrier and tumble resistance of the PVC film, making it suitable for use as a protective or barrier layer in aircraft composite materials. Furthermore, the PVC film of this invention can be directly laminated with the load-bearing layer using an adhesive, optimizing the number of functional structural layers in aircraft composite materials, effectively reducing the overall areal density of aircraft composite materials, and extending their service life.

[0025] The present invention also provides an aircraft composite material, which includes a weather-resistant protective layer, a first adhesive layer, a load-bearing layer, a second adhesive layer and a heat-sealing layer stacked in sequence, wherein the weather-resistant protective layer is composed of the polyvinyl fluoride film described in the present invention.

[0026] The technical solution of the present invention has the following technical advantages compared with the prior art:

[0027] 1. The polyvinyl fluoride film of the present invention has excellent weather resistance, tear resistance and helium barrier properties;

[0028] 2. The polyvinyl fluoride film of the present invention can be used as a protective layer or barrier layer for aircraft composite materials. It can be directly laminated with the load-bearing layer through an adhesive, which simplifies the structure of aircraft composite materials and effectively extends the service life of aircraft composite materials. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0030] The test methods for the embodiments and comparative examples of this invention are as follows:

[0031] 1) Crystallinity was tested using X-ray diffraction.

[0032] 2) Molecular weight and molecular weight distribution were determined using gel permeation chromatography.

[0033] 3) Areal density was tested according to GB / T 4669-2008;

[0034] 4) Helium permeability shall be tested in accordance with GB / T 1038-2000;

[0035] 5) The kneading test shall be conducted in accordance with the provisions of GB / T 41347-2022;

[0036] 6) Ultraviolet light transmittance shall be tested in accordance with the provisions of GB / T 2680-1994;

[0037] 7) Tensile properties shall be tested in accordance with the provisions of GB / T 1040.1-2006.

[0038] Example 1

[0039] S1: 100 parts of polyvinyl fluoride resin with a molecular weight of 650,000, a molecular weight distribution of 1.5, a crystallinity of 46%, and a crystal size of 6.4 nm, 2 parts of nano-silica treated with nonacarbon perfluoropolyether triethoxysilane, 25 parts of titanium dioxide, and 1.5 parts of light stabilizer. 5050H and 0.001 parts of carbon black were added to 180 parts of N,N-dimethylacetamide and dispersed by high-speed stirring for about 60 minutes to form a film-forming slurry.

[0040] S2: The film-forming slurry is passed through a twin-screw extruder, filter, melt metering pump, and die to obtain an extruded sheet. The sheet is cooled and shaped by a cold roller at 40°C. The sheet is then stretched longitudinally through a stretching roller at a ratio of 2.5 times, a stretching temperature of 100°C, and a shrinkage rate of 2.5%. It is then stretched laterally and heat-set on a transverse stretching machine at a ratio of 2.5 times, a stretching temperature of 130°C, and a shrinkage rate of 4%. The heat-set temperature is 180°C and the sizing temperature is 190°C. The polyvinyl fluoride film is further subjected to corona treatment (voltage 380V, frequency 18kHz) to obtain polyvinyl fluoride film I.

[0041] Example 2

[0042] The operation of Example 2 is the same as that of Example 1, except that 100 parts of polyvinyl fluoride resin with a molecular weight of 800,000, a molecular weight distribution of 1.2, a crystallinity of 50%, and a crystal size of 7.6 nm are used. The devolatilization temperature is controlled at 175°C and the setting temperature is controlled at 195°C. Other operations remain unchanged to obtain polyvinyl fluoride film II.

[0043] Example 3

[0044] The operation of Example 3 is the same as that of Example 1, except that: 1.5 parts of perfluorooctyltrimethoxysilane were used to treat nano-silica, which was stretched longitudinally by 3 times, while other operations remained unchanged, to obtain polyvinyl fluoride film III.

[0045] Example 4

[0046] Example 4 was performed in the same manner as Example 3, except that: 1.5 parts of nano-silica treated with nonacarbon perfluoropolyether triethoxysilane were used, the transverse stretching ratio was 3 times, the devolatilization temperature was 170°C, and other operations remained unchanged to obtain polyvinyl fluoride film IV.

[0047] Example 5

[0048] The operation of Example 5 is the same as that of Example 3, except that: 1.5 parts of nano-zinc oxide treated with nonacarbon perfluoropolyether triethoxysilane are used, and other operations remain unchanged to obtain polyvinyl fluoride film V.

[0049] Comparative Example 1

[0050] The operation of Comparative Example 1 is the same as that of Example 1, except that 100 parts of polyvinyl fluoride resin with a molecular weight of 400,000, a molecular weight distribution of 1.4, a crystallinity of 45%, and a crystal size of 7.5 nm are used, and other operations remain unchanged to obtain polyvinyl fluoride film DⅠ.

[0051] Comparative Example 2

[0052] The operation of Comparative Example 2 is the same as that of Example 1, except that 100 parts of polyvinyl fluoride resin with a molecular weight of 800,000, a molecular weight distribution of 1.2, a crystallinity of 40%, and a crystal size of 12.8 nm are used, and other operations remain unchanged to obtain polyvinyl fluoride film DⅡ.

[0053] Comparative Example 3

[0054] The operation of Comparative Example 3 was the same as that of Example 1, except that 100 parts of polyvinyl fluoride resin with a molecular weight of 650,000, a molecular weight distribution of 2.5, a crystallinity of 50%, and a crystal size of 6.0 nm were used, and other operations remained unchanged to obtain polyvinyl fluoride film DⅢ.

[0055] Comparative Example 4

[0056] The operation of Comparative Example 4 was the same as that of Example 1, except that 2 parts of untreated nano-silica were used, and other operations remained unchanged, to obtain polyvinyl fluoride film DⅣ.

[0057] Comparative Example 5

[0058] Existing in the market are polyvinyl fluoride films for aircraft composite materials, labeled as polyvinyl fluoride film DⅤ.

[0059] The areal density, helium permeability, rub resistance and mechanical properties of the polyvinyl fluoride films described in Examples 1-5 and Comparative Examples 1-5 were tested. The test results are detailed in Table 1.

[0060] Table 1. Performance test results of polyvinyl fluoride films in Examples 1-5 and Comparative Examples 1-5

[0061]

[0062] Application Example 1

[0063] The polyvinyl fluoride film I prepared in Example 1 is used as a protective layer and is sequentially laminated with a polyurethane adhesive layer, an aramid fiber fabric, a polyurethane adhesive layer and a thermoplastic polyurethane film layer to form the aircraft composite material I through composite lamination.

[0064] Application Example 2

[0065] The operation of Application Example 2 is the same as that of Application Example 1, except that the polyvinyl fluoride film II prepared in Example 2 is used as the protective layer, and other operations remain unchanged to obtain aircraft composite material II.

[0066] Application Example 3

[0067] The operation of Application Example 3 is the same as that of Application Example 1, except that the polyvinyl fluoride film III prepared in Example 3 is used as the protective layer and barrier layer, and other operations remain unchanged to obtain aircraft composite material III.

[0068] Application Example 4

[0069] The operation of Application Example 4 is the same as that of Application Example 1, except that the polyvinyl fluoride film IV prepared in Example 4 is used as the protective layer and barrier layer, and other operations remain unchanged to obtain aircraft composite material IV.

[0070] Application Example 5

[0071] The operation of Application Example 5 is the same as that of Application Example 1, except that the polyvinyl fluoride film V prepared in Example 5 is used as the protective layer and barrier layer, and other operations remain unchanged to obtain aircraft composite material V.

[0072] Application Comparative Example 1

[0073] The operation of Comparative Example 1 is the same as that of Application Example 1, except that the polyvinyl fluoride film DI prepared in Comparative Example 1 is used as the protective layer and barrier layer, and other operations remain unchanged to obtain the aircraft composite material DI.

[0074] Application Comparative Example 2

[0075] The operation of Comparative Example 2 is the same as that of Application Example 1, except that the polyvinyl fluoride film DII prepared in Comparative Example 2 is used as the protective layer and barrier layer, and other operations remain unchanged to obtain the aircraft composite material DII.

[0076] Application Comparative Example 3

[0077] The operation of Comparative Example 3 is the same as that of Application Example 1, except that the polyvinyl fluoride film DⅢ prepared in Comparative Example 3 is used as the protective layer and barrier layer, and other operations remain unchanged to obtain the aircraft composite material DⅢ.

[0078] Application Comparative Example 4

[0079] The operation of Comparative Example 4 is the same as that of Application Example 1, except that the polyvinyl fluoride film DⅣ prepared in Comparative Example 4 is used as the protective layer and barrier layer, and other operations remain unchanged to obtain the aircraft composite material DⅣ.

[0080] Application Comparative Example 5

[0081] The operation of Comparative Example 5 is the same as that of Application Example 1, except that the polyvinyl fluoride film DUV described in Comparative Example 5 is used as both a protective layer and a barrier layer, while other operations remain unchanged, to obtain the aircraft composite material DUV.

[0082] The areal density, helium permeability and rubbing resistance of the aircraft composite materials described in corresponding use cases 1 to 5 and comparative application examples 1 to 5 were tested. The test results are detailed in Table 2.

[0083] Table 2. Performance test results of composite materials in aircraft from Application Examples 1-5 and Comparative Application Examples 1-5

[0084] <![CDATA[Areal density / g / m 2 > <![CDATA[Helium gas permeation rate / L / m 2 ﹒24h]]> Kneading resistance Application Example 1 130 0.86 300 Application Example 2 123 0.60 360 Application Example 3 127 0.78 300 Application Example 4 122 0.69 320 Application Example 5 128 0.72 340 Comparative Application Example 1 127 3.06 60 Comparative Application Example 2 128 1.8 100 Comparative Application Example 3 125 2.62 80 Comparative Application Example 4 128 4.2 60 Comparative Application Example 5 135 2.41 120

[0085] In summary, the polyvinyl fluoride film of the present invention, when used as a protective layer for aircraft composite materials, simplifies the structure of the composite material while giving the prepared composite material excellent helium barrier properties and tear resistance.

Claims

1. A polyvinyl fluoride film, characterized in that: The film-forming formula of the polyvinyl fluoride film comprises 100 parts of polyvinyl fluoride resin and 0.5 to 2 parts of nucleating agent; the polyvinyl fluoride resin is selected from at least one of polyvinyl fluoride homopolymer or copolymer of vinyl fluoride and other fluorinated monomers, the polyvinyl fluoride resin has a weight-average molecular weight of 450,000 to 1,200,000, a molecular weight distribution of 1.1 to 2.0, a crystallinity of 40% to 60%, and a crystal size of 4.0 to 10.0 nm; the nucleating agent is surface-modified inorganic nanoparticles with a particle size of 1 to 60 nm and a specific surface area of ​​10 to 800 m². 2 / g.

2. The polyvinyl fluoride film according to claim 1, characterized in that: The areal density of the polyvinyl fluoride film is 20–100 g / m³. 2 Helium permeability < 1.5 L / m 2 24h, UV transmittance <0.1%, rub resistance 100-360 times, tensile strength >70MPa, elongation at break >90%.

3. The polyvinyl fluoride film according to claim 1, characterized in that: The inorganic nanoparticles are selected from at least one of nano-silica, nano-zinc oxide, nano-calcium carbonate, and nano-calcium sulfate.

4. The polyvinyl fluoride film according to claim 1, characterized in that: The nucleating agent is surface-modified with a long-chain fluorinated silane coupling agent, wherein the long-chain fluorinated silane coupling agent is selected from at least one of perfluoroolefin-based trimethoxysilane, perfluoroolefin-based triethoxysilane, perfluoropolyether-based trimethoxysilane, perfluoropolyether-based triethoxysilane, or diperfluoropolyether-based tetraethoxysilane.

5. The polyvinyl fluoride film according to claim 4, characterized in that: The long-chain fluorinated silane coupling agent has 6 to 17 carbon atoms.

6. The polyvinyl fluoride film according to claim 1, characterized in that: The polyvinyl fluoride film also includes fillers, light stabilizers, and pigments.

7. The polyvinyl fluoride film according to claim 6, characterized in that: The filler is selected from at least one of titanium dioxide, calcium carbonate, silicate, zinc oxide, aluminum oxide, silicon nitride and zirconium oxide, with an average particle size of 0.1 to 5 μm; the light stabilizer is an oligomer-type hindered amine light stabilizer with a molecular weight of 1000 to 4000; the pigment is at least one of carbon black, iron oxide black, copper chromium black, iron chromium black, composite titanium yellow, bismuth yellow, titanium nickel yellow, composite titanium red, cadmium red or iron red.

8. A method for preparing a polyvinyl fluoride film according to any one of claims 1 to 7, characterized in that: The preparation method includes the following steps: S1: A film stretching slurry is formed by mixing polyvinyl fluoride resin, a latent solvent, a nano-nucleating agent, a filler, a light stabilizer, and a pigment. S2: The film stretching slurry is added to an extruder and subjected to high-temperature extrusion casting, biaxial stretching, devolatilization and shaping to prepare a polyvinyl fluoride film.

9. The method for preparing polyvinyl fluoride film according to claim 8, characterized in that: When biaxially stretched, the longitudinal shrinkage rate is 2% to 5%; the transverse shrinkage rate is 2% to 10%; the devolatilization temperature is 170 to 190℃; and the setting temperature is 180 to 200℃.

10. The application of the polyvinyl fluoride film according to any one of claims 1 to 7 as a protective layer or barrier layer for aircraft composite materials.

11. An aircraft composite material, characterized in that: The aircraft composite material comprises a weather-resistant protective layer, a first adhesive layer, a load-bearing layer, a second adhesive layer, and a heat-sealing layer stacked sequentially, wherein the weather-resistant protective layer is composed of a polyvinyl fluoride film as described in any one of claims 1 to 7.

Images