A polysilazane imide high-temperature-resistant film material and a preparation method and application thereof

Abstract

The application relates to a polysilazane imide high-temperature-resistant film material and a preparation method and application thereof, which is prepared from amino-containing polysilazane oligomers and aromatic dianhydride through nucleophilic ring-opening addition reaction and thermal imidization treatment, and the thickness is 20-100 mu m; wherein the structure of the polysilazane imide is shown in a general formula (I). The imide ring is introduced in-situ into a polysilazane skeleton through nucleophilic ring-opening addition of amino and acid anhydride and thermal imidization reaction, and a hybrid film material with excellent film-forming property, mechanical property and thermal stability is obtained.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, and in particular to a high-temperature resistant polysilazaneimide thin film material, its preparation method, and its application. Background Technology

[0002] Polysilazanes are a class of inorganic polymers whose main chain is composed of alternating silicon and nitrogen atoms. Their Si-N backbone exhibits high bond energy and high rigidity, endowing the materials with excellent high-temperature resistance, oxidation resistance, and high-temperature ceramicization capability. Based on these properties, polysilazanes are widely used in high-temperature coatings, advanced ceramic precursors, and interface modification of fiber-reinforced composites, and have significant application value in extreme working conditions such as aerospace thermal protection and high-temperature functional coatings. However, the weak intermolecular forces and excessive chain flexibility of traditional polysilazane materials result in limited film-forming properties, high brittleness of the cured film, and low mechanical strength, making it difficult to independently prepare continuous, dense, and self-supporting functional thin film materials, which greatly limits their direct engineering applications in thin film form.

[0003] Polyimide is a class of high-performance aromatic heterocyclic polymers containing an imide ring structure in its molecular backbone. Its rigid imide ring structure endows the material with outstanding high-temperature resistance, excellent mechanical strength, good chemical stability, and film-forming processability, making it widely used in aerospace structural materials, flexible electronic substrates, high-temperature insulating films, semiconductor packaging, and other fields. It is one of the representative varieties of high-performance thin film materials. However, polyimide inevitably undergoes thermal oxidative degradation in ultra-high temperature and oxygen-containing environments, limiting its long-term operating temperature. Furthermore, it lacks the ability to undergo high-temperature ceramicization, failing to form a protective ceramic layer under extreme ultra-high temperature conditions. Ultimately, the material will experience structural collapse and failure, making it difficult to meet the higher-temperature application requirements of aerospace thermal protection and high-temperature ablation.

[0004] To address the performance shortcomings of the two types of materials mentioned above, researchers have attempted to composite polysilazane with polyimide to balance film-forming processability and high-temperature resistance. For example, CN108587163B discloses a method for preparing a polyimide / polysilazane hybrid film, in which perhydropolysilazane is dissolved in a polyamic acid solution, physically blended, then deposited, imidized, and the polysilazane is hydrolyzed to form a SiO2 nanophase, thereby achieving filling modification of the polyimide. CN103917364A uses a polysilazane-containing solution coated on the surface of a polyimide film followed by calcination to form a silicon oxide surface layer. However, in the above physical blending or surface coating methods, there is only a physical interaction between polysilazane and polyimide. The two components are prone to macroscopic phase separation driven by molecular thermal motion, resulting in interface defects, micropores, and stress concentration points inside the film. Under high-temperature service conditions, interface peeling is severe, and the improvement in mechanical properties and thermal stability is limited.

[0005] Therefore, how to combine the high-temperature resistance and oxidation resistance of polysilazane with the excellent mechanical properties and film-forming properties of polyimide at the molecular structure level to prepare a novel high-temperature resistant thin film material that combines the advantages of both types of materials has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In order to achieve synergistic performance between the inorganic heat-resistant framework of polysilazane and the rigid imide ring structure of polyimide at the molecular level, and to obtain a high-temperature resistant thin film material with excellent film-forming processability, high mechanical strength and ultra-high temperature thermal stability, this application provides a polysilazane imide high-temperature resistant thin film material, its preparation method and application.

[0007] In a first aspect, this application provides a high-temperature resistant polysilazaneimide thin film material, which adopts the following technical solution: A high-temperature resistant polysilazane imide thin film material is prepared by nucleophilic ring-opening addition reaction and thermal imidization treatment of an amino-containing polysilazane oligomer and an aromatic dianhydride, wherein the thickness of the polysilazane imide high-temperature resistant thin film material is 20-100 μm; wherein the structure of the polysilazane imide is as shown in general formula (I): ; In general formula (Ⅰ), n represents an integer from 1 to 100, and the R1 structure is selected from H, C1-C6 alkyl, C2-C6 alkenyl, C6-C 10 Aryl, halogenated C6-C 10 Any of the aryl groups; the R2 structure is selected from H, C1-C6 alkyl, C2-C6 alkenyl, C6-C 10 Aryl, halogenated C6-C 10 Any of the aryl groups; the R3 structure is selected from C1-C 10 Alkylene, carbonyl-containing C1-C10 Alkylene, C1-C containing unsaturated bonds 10 The R4 structure is selected from any one of alkylene groups or divalent groups containing aromatic rings; the R4 structure is selected from any one of amino-containing C1-C6 alkyl groups, amino-containing aryl groups, or amino-containing aralkyl groups.

[0008] The inventors discovered that the amino groups on the side chains of amino-containing polysilazane oligomers can act as nucleophilic sites, undergoing nucleophilic ring-opening addition reactions with the anhydride groups of aromatic dianhydrides. After the amino group performs nucleophilic attack on the carbonyl carbon of the anhydride, it forms an amide acid structure through tetrahedral intermediate ring opening, which is covalently linked to the ends of the polysilazane backbone or side chains. Subsequently, after thermal imidization treatment, the carboxyl group in the amide acid undergoes intramolecular dehydration cyclization with the ortho-amide group, forming a five-membered imide ring. In this process, the Si-N backbone of the polysilazane does not participate in significant bond breaking or rearrangement, and its inorganic framework integrity and heat resistance are maintained. The rigid imide ring introduced in situ can act as physical crosslinking nodes distributed between the molecular chains, making the film-forming properties and mechanical strength of the polysilazane different from the unmodified system.

[0009] Traditional polysilazane systems, due to the low steric hindrance of the Si-N backbone and the high flexibility of the chain segments, rely mainly on weak van der Waals forces to maintain the aggregated state between molecular chains. During solvent evaporation, internal stress accumulation can easily lead to film shrinkage or cracking, making it difficult to obtain continuous and complete self-supporting films. Even when films are formed, the resulting materials are often brittle, and their mechanical strength is insufficient to meet application requirements. While traditional polyimide systems possess good film-forming properties and mechanical properties, the dense imide rings and aromatic heterocyclic structures in their molecular chains are prone to oxidative crosslinking or chain breakage under ultra-high temperature and oxygen-containing environments, limiting their long-term thermal stability. In this application, the imide ring is covalently anchored to the Si-N backbone of the polysilazane, forming a rigid cross-linked network at the molecular level. The rigid imide ring can increase the strength and density of the interaction between molecular chains, so that the film has a relatively stable aggregated structure after solvent removal, thus exhibiting superior self-supporting film-forming properties and mechanical strength compared to unmodified polysilazane. The Si-N inorganic framework, as the main continuous phase of the film, provides a basis for the thermal stability of the material with its high bond energy. The rigid structure of the imide ring helps to suppress the thermal motion and degradation process of the molecular chains at high temperatures.

[0010] Furthermore, amino-containing polysilazane oligomers are macromolecular multifunctional systems, with each molecular chain containing multiple amino reaction sites. Upon reaction with aromatic dianhydrides, they can form a multi-site grafted crosslinked network structure. Compared to the linear polyimides formed by the reaction of traditional small-molecule diamines with dianhydrides, this multi-site grafted network structure provides a relatively dense distribution of rigid crosslinking points at the molecular level. When the membrane is under stress, stress can be transferred through the covalent bond network within the Si-N backbone, helping to alleviate stress concentration.

[0011] In one specific implementation, the number-average molecular weight of the amino-containing polysilazane oligomer is 500-10000.

[0012] When the number-average molecular weight of amino-containing polysilazane oligomers is in the range of 500-10000, the molecular chain length is moderate, and the solubility and reactivity are relatively balanced. If the molecular weight is too low (e.g., below 500), the chain segments are too short, resulting in insufficient intermolecular entanglement and making the film prone to defects. If the molecular weight is too high (e.g., above 10000), the solubility decreases and the density of reaction sites decreases, which is not conducive to a uniform reaction with dianhydrides. Compounds within this molecular weight range can ensure effective reaction with aromatic dianhydrides and form a stable aggregated structure during film formation, which helps to improve the mechanical properties and thermal stability of the film, while also considering the operability of the preparation process.

[0013] In one specific implementation, the aromatic dianhydride is selected from one or more of pyromellitic dianhydride, biphenyl dianhydride, and naphthalene dianhydride.

[0014] All of the aforementioned aromatic dianhydrides contain rigid aromatic ring structures. Upon reaction with amino-containing polysilazane oligomers, they can introduce rigid imide rings and aromatic residues in situ onto the Si-N backbone. Pyromellitic dianhydride has a compact structure and high reactivity, which helps form a network structure with relatively high crosslinking density. Biphenyltetracarboxylic dianhydride contains a biphenyl structure, which can increase the packing density between molecular chains, contributing to the mechanical modulus and dimensional stability of the film. Naphthalenetetracarboxylic dianhydride has a larger conjugated system, which can improve the heat resistance and thermo-oxidative aging resistance of hybrid films to a certain extent. By selecting one or more of the above dianhydrides in combination, it is helpful to adjust the interaction forces and aggregate structure between molecular chains, thereby obtaining a relatively flexible control space between film-forming properties, mechanical properties, and thermal stability.

[0015] Secondly, this application provides a method for preparing a high-temperature resistant polysilazaneimide thin film material, employing the following technical solution: A method for preparing a high-temperature resistant polysilazaneimide thin film material includes the following steps: S1. Dissolve an amino-containing polysilazane oligomer in an organic solvent to obtain a polysilazane solution; dissolve an aromatic dianhydride in an organic solvent to obtain a dianhydride solution; S2. Under an inert atmosphere, the dianhydride solution is added to the polysilazane solution to carry out a nucleophilic addition reaction to obtain a precursor solution; S3. The precursor solution is subjected to a film-forming treatment to obtain a precursor film; S4. The precursor film is subjected to heat treatment by segmented gradient heating to obtain the polysilazaneimide high-temperature resistant film material.

[0016] The thin film material prepared by the above steps contains both Si-N bonds and imide ring structures in its molecular structure. This preparation method involves pre-dissolving an amino-containing polysilazane oligomer and uniformly mixing it with a dianhydride solution, allowing the reaction to proceed in a homogeneous system. This helps improve the reaction efficiency between the amino and anhydride groups, resulting in a uniform distribution of the amyl acid structure between the polysilazane molecular chains. After film formation, a gradient heating heat treatment is performed, during which the amyl acid gradually dehydrates and cyclizes into imide rings. During this process, the Si-N backbone does not undergo significant degradation or rearrangement, preserving the heat resistance of the inorganic framework. Simultaneously, the rigid structure of the imide rings provides physical crosslinking points for the film, enabling it to exhibit relatively good mechanical strength while possessing a certain degree of flexibility. Compared to the unmodified polysilazane system, this film can achieve self-supporting film formation, and its thermal stability and mechanical properties are improved to some extent.

[0017] In one specific implementation, in step S1, the mass concentration of the amino-containing polysilazane oligomer in the polysilazane solution is 5-30 wt%; and / or, the mass concentration of the aromatic dianhydride in the dianhydride solution is 5-20 wt%.

[0018] The inventors discovered that the synergistic control of the concentrations of the polysilazane solution and the dianhydride solution has a certain impact on the structural uniformity and overall performance of the hybrid film. Specifically, when the concentration of the polysilazane solution is within the range of 5-30 wt%, the solution viscosity is relatively moderate, the molecular chains are in a stretched state, and the accessibility of the amino reaction sites is good, which is conducive to a uniform reaction with the dianhydride. When the concentration is too low (e.g., below 5 wt%), the solid content is too low, and the proportion of solvent evaporation during film formation is too high, which can easily lead to uneven film thickness or surface defects. When the concentration is too high (e.g., above 30 wt%), the degree of entanglement between molecular chains increases, which may affect the uniformity of the reaction system. Similarly, controlling the dianhydride solution concentration within the range of 5-20 wt% helps its dispersion and reaction efficiency in the polysilazane solution; when the concentration is too low, the amount of dianhydride added is limited, and the grafting degree is relatively limited; when the concentration is too high, localized uneven reactions may occur. By controlling the concentrations of both within the aforementioned range, a better balance can be achieved between solution reaction efficiency, film processingability, and film structure density, providing a relatively favorable process basis for the subsequent gradient heat treatment to form a uniform imide crosslinking network.

[0019] In one specific implementation, in step S2, the molar ratio of the amino-containing polysilazane oligomer to the aromatic dianhydride added in the precursor solution is 1:(0.5-15).

[0020] The inventors discovered that the molar ratio of amino-containing polysilazane oligomers to aromatic dianhydrides is one of the key factors affecting the structure and properties of hybrid films. When the molar ratio of polysilazane to dianhydride is controlled within the range of 1:(0.5-15), the functional group ratios of amino and anhydride groups in the system are relatively matched, which is conducive to the full progress of nucleophilic ring-opening addition reactions. When the molar ratio is too low (e.g., below 1:0.5), the amount of dianhydride added is relatively insufficient, a large number of amino groups on the polysilazane molecular chain do not participate in the reaction, and the introduction of imide rings is limited, so the improvement effect on film formation and mechanical properties may not be significant. When the molar ratio is too high (e.g., above 1:15), there is an excess of dianhydride in the system, and some free dianhydride monomers may remain. During heat treatment, uneven local highly cross-linked regions are easily formed, which has a certain impact on the density and flexibility of the film. By controlling the molar ratio within the above range, an appropriate density of imide ring structures can be introduced into the polysilazane molecular chain to form a relatively uniform graft crosslinking network. This helps to obtain better mechanical strength and thermal stability while maintaining the flexibility of the film, and the reaction system is less prone to gelation or phase separation, resulting in a wider process operation window.

[0021] In one specific embodiment, the organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0022] By employing the above-mentioned technical solutions, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone are all strongly polar aprotic solvents, exhibiting good solubility for amino-containing polysilazane oligomers and aromatic dianhydrides. This allows for uniform dispersion of reactants at the molecular level, facilitating effective contact and reaction between amino and anhydride groups. Simultaneously, these solvents possess high chemical inertness, making them less prone to significant side reactions with amino or anhydride functional groups at room temperature, thus ensuring selectivity in the reaction process. Furthermore, the moderate boiling points and relatively controllable evaporation rates of these solvents allow for the formation of a relatively stable solvent evaporation gradient during film formation, contributing to the acquisition of a smooth, dense precursor film and providing a relatively high-quality preform for subsequent thermal imidization treatment. By selecting one or more of these solvents in combination, the solubility and evaporation rates can be appropriately adjusted according to the specific reaction system, enhancing the flexibility and adaptability of the process.

[0023] In one specific implementation, in step S3, the film-forming process is selected from any one of casting film formation, spin coating film formation, and blade coating film formation.

[0024] Casting is suitable for preparing relatively large-area films, and films with relatively uniform thickness can be obtained by controlling the solution supply rate and doctor blade height. Spin coating uses the centrifugal force generated by the high-speed rotation of the substrate to spread the solution evenly, allowing for more precise control of film thickness, and is suitable for preparing small-area or ultra-thin films. Wafer coating is relatively flexible, allowing for the selection of different coating methods as needed, making it highly adaptable. All of the above film-forming methods have a certain tolerance for the viscosity and rheological properties of the precursor solution, and can be used directly without significantly altering the solution composition, requiring no additional process adjustments. By selecting any of the above film-forming methods, flexible choices can be made based on factors such as actual production scale, film thickness requirements, and substrate type, helping to meet the differentiated preparation needs of different application scenarios.

[0025] In one specific implementation scheme, in step S4, the segmented gradient heating method of heat treatment includes a stepped heat treatment by sequentially heating from room temperature to a first temperature segment, a second temperature segment, and a third temperature segment at a heating rate of 1-5℃ / min; wherein, the first temperature segment is 120-180℃ and held for 0.5-2h, the second temperature segment is 220-280℃ and held for 0.5-2h, and the third temperature segment is 280-350℃ and held for 0.5-2h.

[0026] The inventors discovered that a segmented gradient heating method can achieve selective process objectives at different temperature stages, helping to optimize the film structure formation process. The first temperature stage (120-180℃) allows residual organic solvents in the precursor film to gradually evaporate, while some amyl acids undergo initial cyclization. The relatively slow heating rate at this stage helps avoid film surface defects caused by rapid solvent evaporation. The second temperature stage (220-280℃) allows most of the amyl acids to undergo dehydration cyclization, forming imide ring structures. Holding at this temperature for a certain time helps the reaction to become more complete, thereby establishing a relatively uniform covalent crosslinking network between the polysilazane molecular chains. The third temperature stage (280-350℃) promotes further cyclization of residual amyl acids and removes any small amounts of by-reaction products or low-molecular-weight components that may be present in the system, improving the overall crosslinking density and structural stability of the film. Controlling the overall heating rate within the range of 1-5℃ / min helps avoid stress concentration or thermal decomposition side reactions within the film caused by excessively rapid heating, while also ensuring production efficiency. The aforementioned stepwise heating method provides relatively sufficient thermal driving conditions for the conversion of ammonium acid to imide without the introduction of additional catalysts, which helps to obtain a dense, flat and uniform hybrid film.

[0027] Thirdly, this application provides an application of the polysilazaneimide high-temperature resistant thin film material using the first aspect in the preparation of high-temperature resistant protective films and electronic insulating films.

[0028] The polysilazaneimide high-temperature resistant thin film material provided in this application has promising application prospects in the fields of high-temperature protection and electronic insulation. The molecular structure of this thin film material simultaneously contains a Si-N inorganic framework and an imide ring structure, which are connected by covalent bonds, achieving a certain balance between heat resistance and mechanical properties. In high-temperature protection applications, this film can undergo in-situ ceramic transformation under ultra-high temperature environments, forming a dense Si-NC inorganic protective layer, which helps to delay the expansion of thermo-oxidative corrosion into the internal structure. In electronic insulation applications, the molecular chains of the thin film material have a relatively uniform packing density, which can effectively suppress the formation of conductive or leakage paths, thus exhibiting relatively stable insulation performance. By applying the above-mentioned hybrid thin film material to the fields of high-temperature protection and electronic insulation, this application helps to fully utilize the advantages of its organic-inorganic hybrid structure, providing an optional solution for protection and insulation requirements under extreme operating conditions.

[0029] In summary, this application includes at least one of the following beneficial technical effects: 1. This application introduces an imide ring structure in situ into the polysilazane molecular backbone by causing an amino-containing polysilazane oligomer to undergo a nucleophilic ring-opening addition reaction with an aromatic dianhydride. This results in a thin film material whose molecular structure simultaneously contains a Si-N inorganic backbone and an imide ring structure. While maintaining the heat resistance of the inorganic backbone, the introduction of rigid crosslinking nodes helps to improve the film-forming properties and mechanical strength of the polysilazane system, achieving a relative balance between thermal stability and mechanical properties in the thin film material.

[0030] 2. This application controls the number average molecular weight of the amino-containing polysilazane oligomer in the range of 500-10000, the solution concentration and dianhydride concentration in the range of 5-30wt% and 5-20wt% respectively, and the molar ratio of polysilazane to dianhydride in the range of 1:(0.5-15), so that the reaction system has good uniformity and reaction efficiency, which helps to form a relatively uniformly distributed graft crosslinking network, thereby obtaining a hybrid thin film material with a relatively dense structure and relatively stable performance.

[0031] 3. This application employs a segmented gradient heating method to heat-treat the precursor film, allowing the amic acid structure in the precursor film to gradually complete the dehydration and cyclization reaction at different temperature stages. Combined with a relatively gentle heating rate and step-by-step heat preservation, this facilitates the full imidization reaction, resulting in a continuous, flat, and dense film structure with good overall performance. Detailed Implementation

[0032] The present application will be further described in detail below with reference to embodiments and comparative examples: Some of the raw materials used in the examples and comparative examples: The amino-containing polysilazane oligomers with number average molecular weights of 3000, 5000, and 10000 used in this application were all purchased from Wuxi Polymer High-Tech Materials Technology Co., Ltd. The structure of the polysilazane imide prepared by the amino-containing polysilazane oligomers is as shown in general formula (Ⅰ): ; Among them, R1, R2, R3, and R4 in the structural formula of the amino-containing polysilazane oligomer with a number average molecular weight of 3000 are respectively: ; Among them, R1, R2, R3, and R4 in the structural formula of the amino-containing polysilazane oligomer with a number average molecular weight of 5000 are respectively: ; Among them, R1, R2, R3, and R4 in the structural formula of the amino-containing polysilazane oligomer with a number average molecular weight of 10000 are respectively: .

[0033] Unless otherwise specified, all raw materials used in the examples and comparative examples are commercially available products. Example Example 1

[0034] The preparation of polysilazaneimide high-temperature resistant thin film material is as follows: S1. Add 10g of an amino-containing polysilazane oligomer with a number-average molecular weight of 3000 to 90g of N,N-dimethylformamide and stir at room temperature for 2h to obtain a polysilazane solution; add 3.2g of pyromellitic dianhydride to 30g of N,N-dimethylformamide and stir at room temperature for 2h to obtain a dianhydride solution; S2. Under nitrogen protection, the dianhydride solution was added to the polysilazane solution at a dropping time of 30 min, and the reaction was stirred at room temperature for 6 h to obtain the precursor solution (the molar ratio of amino-containing polysilazane oligomer to pyromellitic dianhydride in the precursor solution was 1:4.45). S3. The precursor solution is coated onto a clean glass substrate surface by casting, the wet film thickness is controlled to be 200 μm, and the film is pre-dried at 80°C for 2 hours to obtain the precursor film. S4. The precursor film is placed in an oven for segmented gradient heating heat treatment: the temperature is increased from room temperature to 150℃ at a heating rate of 2℃ / min and held for 1 hour; then the temperature is increased to 250℃ at a heating rate of 2℃ / min and held for 1 hour; then the temperature is increased to 300℃ at a heating rate of 2℃ / min and held for 1 hour; and then the temperature is naturally cooled to room temperature to obtain polysilazaneimide high temperature resistant film material. Example 2

[0035] The difference between Example 2 and Example 1 is only that in step S1 of Example 2, 10g of amino-containing polysilazane oligomer with a number average molecular weight of 3000 is replaced by an equal amount of 10g of amino-containing polysilazane oligomer with a number average molecular weight of 5000. In this example, in step S2, the molar ratio of amino-containing polysilazane oligomer to pyromellitic dianhydride in the precursor solution is 1:7.35. Example 3

[0036] The difference between Example 3 and Example 1 is only that in step S1 of Example 3, 10g of amino-containing polysilazane oligomer with a number average molecular weight of 3000 is replaced by an equal amount of 10g of amino-containing polysilazane oligomer with a number average molecular weight of 10000. In this example, in step S2, the molar ratio of amino-containing polysilazane oligomer to pyromellitic dianhydride in the precursor solution is 1:14.7. Example 4

[0037] The difference between Example 4 and Example 2 is only that in step S1 of Example 4, 3.2g of pyromellitic dianhydride is replaced by an equal amount of 3.2g of biphenyltetracarboxylic dianhydride. In this example, in step S2, the molar ratio of amino-containing polysilazane oligomer to biphenyltetracarboxylic dianhydride in the precursor solution is 1:5.45. Example 5

[0038] The difference between Example 5 and Example 2 is only that in step S1 of Example 5, 3.2g of pyromellitic dianhydride is replaced by an equal amount of 3.2g of naphthalenetetracarboxylic dianhydride. In this example, in step S2, the molar ratio of amino-containing polysilazane oligomer to naphthalenetetracarboxylic dianhydride in the precursor solution is 1:5.95.

[0039] Comparative Example 1 The only difference between Comparative Example 1 and Example 2 is that in step S2 of Comparative Example 1, 10g of amino-containing polysilazane oligomer with a number average molecular weight of 5000 is replaced by an equal amount of 10g of p-phenylenediamine.

[0040] Comparative Example 2 The only difference between Comparative Example 2 and Example 2 is that in Comparative Example 1, the segmented gradient heating heat treatment is replaced with a single-stage heating heat treatment in step S4. The specific content of step S4 is as follows: S4. Place the precursor film in an oven and heat it from room temperature to 300℃ at a heating rate of 2℃ / min, and keep it at that temperature for 3 hours; then cool it naturally to room temperature to obtain the polysilazaneimide high-temperature resistant film material.

[0041] The thickness of the polysilazaneimide high-temperature resistant film materials prepared in the above embodiments and comparative examples was controlled at 25 μm. Performance tests were conducted on the samples according to the following standards: 1. Referring to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", each sample was tested in strip form on a universal testing machine at the specified tensile rate, and the tensile strength, elongation at break and Young's modulus were recorded. 2. Referring to GB / T 27761-2011 "Test Method for Weight Loss and Residual Amount of Thermogravimetric Analyzer", a thermogravimetric analyzer was used to heat the sample from room temperature to 800℃ at a heating rate of 10℃ / min under a nitrogen atmosphere. The temperature at which the sample mass loss reached 5% (Td5%) was recorded.

[0042] 3. Place the sample in a 400℃ air-circulating oven for 2 hours. After removing it, allow it to cool naturally to room temperature. Visually observe and record the changes in the sample's appearance under a standard light source, including color changes, surface condition (whether it is smooth, whether there are cracks, bubbles, wrinkles, etc.), and overall integrity. 4. Before testing the integrity of the high-temperature ceramization structure, the polysilazaneimide high-temperature resistant thin film materials prepared in each example and comparative example were placed in a tube furnace and heated to 120°C at a heating rate of 2°C / min, and held for 1 hour; then heated to 500°C at a heating rate of 5°C / min, and held for 2 hours to obtain the ceramic precursor film; then the ceramic precursor films were heated to 600°C at a heating rate of 5°C / min, and held for 2 hours to obtain the ceramic thin film material. After cooling to room temperature, the appearance integrity of the ceramic film (whether it cracks, powders, deforms, etc.) was visually observed and recorded under a standard light source.

[0043] The test data are summarized in Table 1 below. Table 1. Performance test data of various polysilazaneimide high-temperature resistant thin film material samples

[0044] Based on Examples 1-5 and Table 1, it can be seen that, comparing Examples 1 (Mn=3000), 2 (Mn=5000), and 3 (Mn=10000), as the molecular weight of the amino-containing polysilazane oligomer increases, the tensile strength of the film first increases and then decreases, the elongation at break gradually decreases, while the Young's modulus and Td5% gradually increase. Relatively low molecular weight polysilazanes are beneficial for maintaining the flexibility of the film, while higher molecular weights result in increased Si-N backbone segments, an increased proportion of rigid structural units, improved film rigidity but a decrease in flexibility. Overall, film materials with good comprehensive performance can be obtained in the number-average molecular weight range of 3000-10000, with a relatively better balance between mechanical properties and thermal stability at Mn=5000.

[0045] Comparing Examples 2 (PMDA), 4 (BPDA), and 5 (NTDA), it is evident that the type of dianhydride has a differentiated impact on the film properties. The PMDA system exhibits better overall mechanical properties; the BPDA system, due to the presence of biphenyl rigid units, results in a film with a relatively high Young's modulus and pronounced rigidity; the NTDA system, with its larger conjugated system and higher bond energy due to the naphthalene ring structure, produces a film with superior resistance to thermo-oxidative aging. The films obtained from all three dianhydride systems maintained structural integrity after ceramization at 600℃, indicating that the preparation method described in this application has good applicability to different dianhydride monomers. In practical applications, the appropriate dianhydride monomer can be flexibly selected according to different requirements for mechanical strength, rigidity, or heat resistance. Combining Example 1 and Comparative Examples 1-2, and referring to Table 1, it can be seen that Comparative Example 1 used traditional small-molecule p-phenylenediamine to replace amino-containing polysilazane oligomers in the reaction with PMDA, resulting in a conventional polyimide film. While its room-temperature mechanical properties were slightly better than those of Example 1, its Td5% was significantly lower. After thermal aging at 400℃, it exhibited yellowing and microcracks, and after high-temperature treatment at 600℃, it completely carbonized and the film collapsed. This indicates that although conventional polyimide films have excellent room-temperature mechanical properties, the imide rings and aromatic heterocyclic structures in the molecular chain are prone to oxidative crosslinking and chain breakage under ultra-high temperature and aerobic conditions, resulting in insufficient long-term thermal stability and a lack of ceramic conversion capability.

[0046] Comparative Example 2 used a one-step heating process (directly heating to 300°C and holding) instead of a segmented gradient heating heat treatment. The resulting film's mechanical properties, Td5%, and appearance after 400°C thermal aging were all inferior to those of Example 1. This is because during the one-step rapid heating process, the solvent residue volatilization and the amide acid cyclization reaction occur simultaneously and violently, easily leading to stress concentration within the film and incomplete imidization. In contrast, the segmented gradient heating method allows the solvent to fully volatilize at low temperatures and the amide acid to cyclize in an orderly manner during the gradual heating process, which is beneficial for obtaining a film with a dense structure and low internal stress.

[0047] This application introduces an imide ring structure in situ onto the Si-N backbone of polysilazane by inducing a nucleophilic ring-opening addition reaction between an amino-containing polysilazane oligomer and an aromatic dianhydride. Following segmented gradient heating, an organic-inorganic hybrid high-temperature resistant film is obtained. This film exhibits both good mechanical properties and excellent ultra-high temperature thermal stability, remaining intact after thermal aging at 400℃. Furthermore, it can be in situ transformed into a dense Si-NC ceramic film at 600℃ while maintaining structural integrity. This overcomes the limitations of conventional polyimides in terms of insufficient ultra-high temperature stability and lack of ceramicization function while maintaining good mechanical properties. It also solves the problem of pure polysilazane's difficulty in self-supporting film formation.

[0048] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-temperature resistant polysilazaneimide thin film material, characterized in that, The polysilazane imide high-temperature resistant film material is prepared by nucleophilic ring-opening addition reaction and thermal imidization treatment of amino-containing polysilazane oligomers and aromatic dianhydrides, and the thickness of the polysilazane imide high-temperature resistant film material is 20-100 μm; wherein, the structure of the polysilazane imide is as shown in general formula (I): ； In general formula (Ⅰ), n represents an integer from 1 to 100, and the R1 structure is selected from H, C1-C6 alkyl, C2-C6 alkenyl, C6-C 10 Aryl, halogenated C6-C 10 Any of the aryl groups; the R2 structure is selected from H, C1-C6 alkyl, C2-C6 alkenyl, C6-C 10 Aryl, halogenated C6-C 10 Any of the aryl groups; the R3 structure is selected from C1-C 10 Alkylene, carbonyl-containing C1-C 10 Alkylene, C1-C containing unsaturated bonds 10 The R4 structure is selected from any one of alkylene groups or divalent groups containing aromatic rings; the R4 structure is selected from any one of amino-containing C1-C6 alkyl groups, amino-containing aryl groups, or amino-containing aralkyl groups.

2. The high-temperature resistant polysilazaneimide thin film material according to claim 1, characterized in that, The number average molecular weight of the amino-containing polysilazane oligomer is 500-10000.

3. The high-temperature resistant polysilazaneimide thin film material according to claim 1, characterized in that, The aromatic dianhydride is selected from one or more of pyromellitic dianhydride, biphenyl dianhydride, and naphthalene dianhydride.

4. A method for preparing the polysilazaneimide high-temperature resistant thin film material according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Dissolve an amino-containing polysilazane oligomer in an organic solvent to obtain a polysilazane solution; dissolve an aromatic dianhydride in an organic solvent to obtain a dianhydride solution; S2. Under an inert atmosphere, the dianhydride solution is added to the polysilazane solution to carry out a nucleophilic addition reaction to obtain a precursor solution; S3. The precursor solution is subjected to a film-forming treatment to obtain a precursor film; S4. The precursor film is subjected to heat treatment by segmented gradient heating to obtain the polysilazaneimide high-temperature resistant film material.

5. The method for preparing the polysilazaneimide high-temperature resistant thin film material according to claim 4, characterized in that, In step S1, the mass concentration of amino-containing polysilazane oligomer in the polysilazane solution is 5-30 wt%; and / or, the mass concentration of aromatic dianhydride in the dianhydride solution is 5-20 wt%.

6. The method for preparing the polysilazaneimide high-temperature resistant thin film material according to claim 4, characterized in that, In step S2, the molar ratio of the amino-containing polysilazane oligomer to the aromatic dianhydride added in the precursor solution is 1:(0.5-15).

7. The method for preparing the polysilazaneimide high-temperature resistant thin film material according to claim 4, characterized in that, The organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

8. The method for preparing the polysilazaneimide high-temperature resistant thin film material according to claim 4, characterized in that, In step S3, the film-forming process is selected from any one of casting film formation, spin coating film formation, and blade coating film formation.

9. The method for preparing the polysilazaneimide high-temperature resistant thin film material according to claim 4, characterized in that, In step S4, the segmented gradient heating method of heat treatment includes a stepped heat treatment by sequentially heating from room temperature to a first temperature segment, a second temperature segment, and a third temperature segment at a heating rate of 1-5℃ / min; wherein the first temperature segment is 120-180℃ and held for 0.5-2h, the second temperature segment is 220-280℃ and held for 0.5-2h, and the third temperature segment is 280-350℃ and held for 0.5-2h.

10. The application of the polysilazaneimide high-temperature resistant film material according to any one of claims 1-3 in the preparation of high-temperature resistant protective films and electronic insulating films.

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