Ablation-resistant metal-modified polysilazane resin, and preparation method and application thereof

Abstract

The application relates to the technical field of high polymer materials, and discloses an ablation-resistant metal-modified polysilaborazane resin as well as a preparation method and application thereof. The method comprises the following steps: (1) under an argon or nitrogen atmosphere, a part of hexamethyldisilazane is added into a solution containing a metal chloride to perform a first contact reaction, and an intermediate compound I is obtained; (2) under the argon or nitrogen atmosphere, another part of hexamethyldisilazane is added into a mixed solution of boron trichloride and methyldichlorosilane, and then the intermediate compound I is mixed to perform a second contact reaction, and an intermediate compound II is obtained; and (3) under the argon or nitrogen atmosphere, the intermediate compound II is subjected to a segmented heating and curing treatment, and the ablation-resistant metal-modified polysilaborazane resin is obtained. In the application, refractory metal elements are introduced into a polymerization system in the form of prefabricated metal silazane precursors in situ, a polysilaborazane resin with uniform metal distribution is successfully prepared, the ablation-resistant and high-temperature-resistant performance of the material is significantly improved, the reaction process is controllable, and the industrial application prospect is good.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to an ablation-resistant metal-modified polysiloxane-boron alkane resin, its preparation method, and its applications. Background Technology

[0002] As spacecraft evolve towards higher speeds and longer flight times, their thermal protection systems face extremely harsh aerodynamic heating environments. During high-speed atmospheric reentry or prolonged near-space flight, the surfaces and critical components of spacecraft must withstand sustained high temperatures exceeding 1500°C and severe ablation. Therefore, developing novel thermal protection materials that are lightweight, high-strength, and especially possess excellent ablation resistance and thermal shock resistance has become one of the core technological challenges in ensuring the safety and reliability of advanced aerospace equipment.

[0003] Among numerous candidate materials, polysiloxane-boron alkane resin, due to its molecular backbone composed of strong covalent bonds such as Si-N and BN, exhibits intrinsic high-temperature stability, excellent oxidation resistance, and ablation resistance potential, and is considered a promising ceramic precursor and high-temperature resistant resin matrix. To further enhance its extreme operating temperature and overall protective performance, the introduction of high-melting-point refractory metal elements (such as Ti, Zr, Hf, and Ta) for modification has become an important research direction in this field. The introduction of metal elements is expected to form high-melting-point ceramic phases (such as carbides and nitrides) in the material, which can not only significantly improve the thermal stability and ablation resistance of the matrix, but also potentially endow the material with tunable electromagnetic properties, expanding its applications in broadband stealth, electromagnetic shielding, and other fields.

[0004] Currently, the preparation strategies for metal-modified polyborosilicates mainly focus on the "post-polymerization modification" route. For example, CN120230295A discloses the method of first synthesizing polyborosilicate fluids, and then using organometallic compounds such as tantalum ethoxide to crosslink with its active groups (such as Si-H bonds) to introduce tantalum. Similarly, other technologies (such as CN114276149A and CN120099711A) use hafnium-containing organometallic compounds to react with polyborosilicates, aiming to control the electromagnetic properties of the material. While these methods have made some progress, their inherent bottlenecks are becoming increasingly apparent: First, metal modifiers are introduced only after the polymer skeleton has been initially formed, relying on their diffusion and reaction in viscous polymer melts or solutions. This makes it difficult to achieve uniform dispersion of metal atoms at the molecular scale, which can easily lead to local aggregation or phase separation, affecting the material's uniformity. Second, due to the limited number of reactive sites and steric hindrance, the introduction of high-content metal elements is often difficult, and unreacted organometallic groups may remain due to incomplete reactions, affecting the purity and performance of the final ceramic product. Third, the degree of crosslinking reaction is affected by various factors, making it difficult to precisely control the binding state and distribution of metal elements and the polymer network.

[0005] Therefore, the key to improving the performance of metal-modified polysiloxane-boron alkane resin and meeting the needs of next-generation ultra-high temperature thermal protection materials lies in developing a novel synthesis method that can achieve efficient, uniform, and controllable introduction of refractory metal elements from the perspective of molecular structure design, and overcoming the bottleneck of post-polymerization modification strategies. Summary of the Invention

[0006] The purpose of this invention is to solve the problem in the prior art that it is difficult to achieve uniform dispersion and high content of metal elements at the molecular level when preparing metal-modified polysiloxane nitride resin.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for preparing an ablation-resistant metal-modified polysiloxane-boron alkane resin, the method comprising the following steps: (1) Under an argon or nitrogen atmosphere, a portion of hexamethyldisilazane is added dropwise to a solution containing metal chloride to carry out the first contact reaction, yielding intermediate compound I; (2) Under an argon or nitrogen atmosphere, another portion of hexamethyldisilazane is first added dropwise to a mixed solution of boron trichloride and methyldichlorosilane, and then mixed with the intermediate compound I to carry out a second contact reaction to obtain intermediate compound II; (3) Under an argon or nitrogen atmosphere, the intermediate compound II is subjected to segmented heating and curing treatment to obtain the ablation-resistant metal-modified polysilicon boron alkane resin.

[0008] A second aspect of the present invention provides an ablation-resistant metal-modified polysiloxane resin prepared by the method described in the first aspect.

[0009] The third aspect of the present invention provides the application of the ablation-resistant metal-modified polysiloxane-boron alkane resin described in the first aspect in the preparation of thermal protection materials, ablation-resistant coatings or ceramic precursors.

[0010] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The method provided by this invention abandons the traditional "post-polymerization modification" strategy and adopts a "two-step in-situ copolymerization" route. Metal chlorides are pre-formed into "metal compounds with trimethylsilyl nitrogen groups" with well-defined structures, making them active precursors that can be directly copolymerized with boron and silicon monomers. In the subsequent polycondensation reaction, the metal center of this compound can participate in the construction of the polymer backbone simultaneously with elements such as Si, B, and N, thereby achieving in-situ embedding and uniform distribution of metal atoms in the molecular chain structure. This effectively overcomes the problem of easy aggregation and uneven diffusion of metal species in the post-modification process, laying the molecular foundation for obtaining ablation-resistant materials with uniform composition and stable performance.

[0011] (2) This invention provides a refined process flow and stringent reaction conditions tailored to the unique copolymerization reaction described above. Specifically, in the critical stages of reactant mixing and initial polymerization, a low-temperature initiation of -40°C to -10°C and an extremely slow programmed temperature increase of 10-30°C / h are employed. This highly controllable process not only helps suppress side reactions but also further ensures the stable and complete reaction of the metal precursor with other monomers, allowing for precise optimization of each reaction step. Compared to post-modification methods that rely on later diffusion and crosslinking, the process of this invention offers higher repeatability and is more conducive to the industrial-scale preparation and quality stability of the product.

[0012] (3) After introducing refractory metals (such as Ti, Zr, Hf) through the method of this invention, the residual mass of the resulting resin at 800℃ under an inert atmosphere can reach up to 86.10%, which is a significant improvement compared to unmodified polysiloxane. The metal elements not only act as crosslinking centers to increase the network density of the precursor and reduce the volatilization of organic components at high temperatures, but also form a stable ceramic phase with a high melting point with the matrix at higher temperatures, thereby endowing the material with excellent ablation resistance. In addition, by selecting different types and contents of metal chlorides, while ensuring ablation resistance, the electromagnetic parameters and other properties of the material can be controlled within a certain range, expanding its application potential in the field of high-temperature functional protection. Attached Figure Description

[0013] Figure 1 This is a hydrogen NMR spectrum of the ablation-resistant metal-modified polysiloxane nitride resin prepared in a preferred embodiment of the present invention. Figure 2 These are thermogravimetric curves of the ablation-resistant metal-modified polysilicon boroazine resin and the polysilicon boroazine resin prepared in the embodiments and comparative examples of the present invention. Figure 3 These are scanning electron microscope (SEM) images of the ablation-resistant metal-modified polysilicon boroazine resin and polysilicon boroazine resin prepared in Example 1 and Comparative Example 2 of this invention. Detailed Implementation

[0014] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0015] As mentioned above, the first aspect of the present invention provides a method for preparing an ablation-resistant metal-modified polysiloxane-boron alkane resin, the method comprising the following steps: (1) Under an argon or nitrogen atmosphere, a portion of hexamethyldisilazane is added dropwise to a solution containing metal chloride to carry out the first contact reaction, yielding intermediate compound I; (2) Under an argon or nitrogen atmosphere, another portion of hexamethyldisilazane is first added dropwise to a mixed solution of boron trichloride and methyldichlorosilane, and then mixed with the intermediate compound I to carry out a second contact reaction to obtain intermediate compound II; (3) Under an argon or nitrogen atmosphere, the intermediate compound II is subjected to segmented heating and curing treatment to obtain the ablation-resistant metal-modified polysilicon boron alkane resin.

[0016] It should be noted that, in this invention, both the portion of hexamethyldisilazane and the other portion of hexamethyldisilazane are hexamethyldisilazane.

[0017] In a preferred embodiment, in step (1), the solution containing the metal chloride is a solution obtained by dissolving the metal chloride in a solvent, and the solvent is selected from at least one of anhydrous toluene, anhydrous xylene, anhydrous tetrahydrofuran, and anhydrous N,N-dimethylformamide.

[0018] More preferably, in step (1), the metal chloride is dissolved in a solvent at a molar ratio of 1:10-30 to obtain the solution containing the metal chloride.

[0019] In a preferred embodiment, in step (1), the metal chloride is selected from at least one of molybdenum chloride, tungsten chloride, titanium chloride, zirconium chloride, yttrium chloride, lanthanum chloride, niobium chloride, nickel chloride, hafnium chloride, samarium chloride, vanadium chloride, rhodium chloride, holmium chloride, cobalt chloride, chromium chloride, titanium dicene dichlorodi ...

[0020] More preferably, in step (1), the metal chloride is selected from at least one of titanium chloride, zirconium chloride, hafnium chloride, tantalum chloride, titanium dichlorocerocene, zirconium dichlorocerocene, and hafnium dichlorocerocene.

[0021] More preferably, in step (1), the metal chloride is at least one of hafnium chloride, titanium chloride, and zirconium chloride.

[0022] According to a preferred embodiment, in step (1), the first contact reaction includes: adding a portion of hexamethyldisilazane dropwise to the solution containing the metal chloride at -40°C to -10°C, then raising the temperature to 100-130°C at a rate of 10-30°C / h, and holding the temperature for 1-3h to obtain intermediate compound I. In this preferred embodiment, the method of the present invention is more conducive to suppressing side reactions and can further ensure the stable and complete reaction between the metal precursor and other monomers.

[0023] Preferably, in step (1), during the first contact reaction, the dropping rate of the portion of hexamethyldisilazane is 2-6 mL / min. This preferred method maintains the thermal balance of the system, effectively suppressing excessive crosslinking caused by excessively high local concentrations, thereby achieving precise control of the polymerization rate.

[0024] In a preferred embodiment, in step (1), the molar ratio of the portion of hexamethyldisilazane to the metal chloride in the solution containing the metal chloride is 2-6:1. This preferred embodiment ensures that the metal-chlorine bond is fully substituted while effectively suppressing side reactions.

[0025] In a preferred embodiment, in step (2), the operation of the second contact reaction includes: first mixing the boron trichloride and the methyldichlorosilane at -40°C to -10°C, then adding the other part of hexamethyldisilazane dropwise, and heating to 22-28°C for 15 hours; then heating to 100-130°C at a rate of 10-30°C / hour and reacting for 0.5-2 hours; subsequently adding the intermediate compound I, continuing the reaction for 0.5-2 hours, and then heating to 220-320°C at the same rate for 1-2 hours, and obtaining the intermediate compound II by vacuum distillation. In this preferred configuration, the initial reaction rate of boron trichloride, methyldichlorosilane, and hexamethyldisilazane can be controlled at low temperatures to avoid uncontrollable excessively rapid reactions and side reactions. Furthermore, intermediate compound I is added during the subsequent stepwise heating process. In the subsequent polycondensation reaction, its metal center can participate in the construction of the polymer backbone simultaneously with elements such as Si, B, and N, thereby achieving in-situ embedding and uniform distribution of metal atoms in the molecular chain structure.

[0026] Preferably, in this invention, the conditions for vacuum distillation in step (2) are at least: pressure < 100 Pa, time 5-60 min, and temperature 220-320 °C.

[0027] Preferably, in step (2), the dropping rate of the other portion of hexamethyldisilazane is 2-6 mL / min.

[0028] In a preferred embodiment, in step (2), the mass ratio of boron trichloride, methyl dichlorosilane, another portion of hexamethyldisilazane to intermediate compound I is 1:0.5-2:5-12:0.5-2.

[0029] According to a preferred embodiment, in step (3), the segmented heating and curing process includes: in an inert atmosphere, the intermediate compound II is heated to 350-400°C in stages at a rate of 5-20°C / min; wherein, the intermediate compound II is held at 100°C, 200°C and 300°C for 0.5-2 hours each, and finally held at 350-400°C for 1-6 hours to obtain the ablation-resistant metal-modified polysiloxane-boron alkane resin.

[0030] It should be noted that there are no specific requirements for the heating equipment and medium in this invention. Conventional techniques in the field can be used. For example, heating can be performed using a heating jacket, metal bath or tube furnace that meets the temperature requirements.

[0031] As previously stated, a second aspect of the present invention provides an ablation-resistant metal-modified polysiloxane-2-monocyanate resin prepared by the method described in the first aspect.

[0032] As previously stated, the third aspect of the present invention provides the application of the ablation-resistant metal-modified polysiloxane-boron alkane resin described in the first aspect in the preparation of thermal protection materials, ablation-resistant coatings, or ceramic precursors.

[0033] The present invention will be described in detail below through examples. Unless otherwise specified, the raw materials used are all commercially available products.

[0034] Unless otherwise specified, "room temperature" or "room temperature" as used in this invention refers to a temperature of 22-28°C.

[0035] Solutions containing metal chlorides: Solution I containing metal chloride: prepared by dissolving the metal chloride (titanium chloride) in a solvent (anhydrous toluene) at a molar ratio of 1:19; Solution II containing metal chloride: The solution is prepared by dissolving the metal chloride (zirconium chloride) in a solvent (anhydrous N,N-dimethylformamide) at a molar ratio of 1:26. Solution III containing metal chloride: prepared by dissolving metal chloride (hafnium chloride) in solvent (anhydrous xylene) at a molar ratio of 1:16.

[0036] Unless otherwise specified, in this invention, the yield of intermediate compound II refers to the percentage of its mass relative to the total mass of all starting materials (including metal chlorides, boron trichloride, methyldichlorosilane and hexamethyldisilazane used in each step) input in steps (1) and (2). Example 1

[0037] This embodiment illustrates that the method for preparing ablation-resistant metal-modified polysiloxane boronazine resin provided by the present invention is carried out according to the following steps: (1) Under an argon atmosphere, a solution containing metal chloride (solution I containing metal chloride) is subjected to a first contact reaction with a portion of hexamethyldisilazane: At -20°C, a portion of the hexamethyldisilazane was added dropwise to the solution containing the metal chloride at a rate of 3 mL / min, and then the temperature was increased to 120°C at a rate of 25°C / h, and then kept at this temperature for 2 h to obtain intermediate compound I; the molar ratio of the portion of hexamethyldisilazane to the metal chloride in the solution containing the metal chloride was 4.1:1. (2) Under an argon atmosphere, boron trichloride, methyldichlorosilane, and another portion of hexamethyldisilazane were reacted with the intermediate compound I in a mass ratio of 1.0:2.0:8.3:0.6 to undergo a second contact reaction: First, boron trichloride and methyldichlorosilane were mixed at -40°C, and then another portion of hexamethyldisilazane was added dropwise at a rate of 3 mL / min. The mixture was heated to room temperature and reacted for 15 h. Then, the temperature was increased to 120°C at a rate of 25°C / h and reacted for 1 h. Subsequently, intermediate compound I was added, and the mixture was reacted for another 1 h. Then, the temperature was increased to 290°C at a rate of 25°C / h and reacted for 1 h. After vacuum distillation at 290°C (pressure < 100 Pa, time 15 min), intermediate compound II was obtained with a yield of 9.32 wt%. (3) Under an argon atmosphere, the intermediate compound II is subjected to segmented heat curing treatment: The intermediate compound II was heated to 400°C in stages at a rate of 10°C / min; wherein, it was held at 100°C, 200°C and 300°C for 0.5 h each, and finally held at 400°C for 4 h to obtain the ablation-resistant metal-modified polysilicon boronazine resin, named P1.

[0038] Figure 1 The 1H NMR spectrum of P1 is shown. The spectrum shows that the characteristic peaks at 0.05-0.1 ppm, 0.8-1.0 ppm, 1.6-2.1 ppm, and 4.5-5.1 ppm belong to the -SiCH3, -SiNH-, -BNH-, and -SiH- structures, respectively. Notably, the 1.25 ppm peak corresponds to the characteristic peak of -TiNH-. The simultaneous appearance of these characteristic peaks demonstrates the successful synthesis of the titanium-modified polysilicon boronazine resin precursor. Example 2

[0039] This embodiment illustrates that the method for preparing ablation-resistant metal-modified polysiloxane boronazine resin provided by the present invention is carried out according to the following steps: (1) Under an argon atmosphere, a solution containing metal chloride (solution II containing metal chloride) is subjected to a first contact reaction with a portion of hexamethyldisilazane: At -40°C, a portion of the hexamethyldisilazane was added dropwise to the solution containing the metal chloride at a rate of 4 mL / min, and then the temperature was increased to 120°C at a rate of 30°C / h, and then kept at this temperature for 2 h to obtain intermediate compound I; the molar ratio of the portion of hexamethyldisilazane to the metal chloride in the solution containing the metal chloride was 4.1:1. (2) Under an argon atmosphere, boron trichloride, methyldichlorosilane, and another portion of hexamethyldisilazane were reacted with the intermediate compound I in a mass ratio of 1.0:2.0:8.3:0.6 to undergo a second contact reaction: First, boron trichloride and methyldichlorosilane were mixed at -40°C, and then another portion of hexamethyldisilazane was added dropwise at a rate of 4 mL / min. The mixture was heated to room temperature and reacted for 15 h. Then, the temperature was increased to 120°C at a rate of 30°C / h and reacted for 1 h. Subsequently, intermediate compound I was added, and the mixture was reacted for another 1 h. Then, the temperature was increased to 320°C at a rate of 30°C / h and reacted for 2 h. After vacuum distillation at 320°C (pressure < 100 Pa, time 34 min), intermediate compound II was obtained with a yield of 10.35 wt%. (3) Under an argon atmosphere, the intermediate compound II is subjected to a segmented heat curing treatment: The intermediate compound II was heated to 400°C in stages at a rate of 5°C / min; wherein, it was held at 100°C, 200°C and 300°C for 1 hour each, and finally held at 400°C for 3 hours to obtain the ablation-resistant metal-modified polysilicon boronazine resin, named P2. Example 3

[0040] This embodiment uses a method similar to that of Embodiment 1, except that the parameters in step (2) are different. Specifically: (2) Under an argon atmosphere, boron trichloride, methyldichlorosilane, and another portion of hexamethyldisilazane were reacted with the intermediate compound I in a mass ratio of 1.0:1.0:8.3:0.6 to undergo a second contact reaction: First, boron trichloride and methyldichlorosilane were mixed at -30°C, and then another portion of hexamethyldisilazane was added dropwise at a rate of 3 mL / min. The mixture was heated to room temperature and reacted for 15 h. Then, the temperature was increased to 120°C at a rate of 30°C / h and reacted for 1 h. Subsequently, intermediate compound I was added, and the mixture was reacted for another 1 h. Then, the temperature was increased to 270°C at the same rate and reacted for 1 h. After vacuum distillation at 270°C (pressure < 100 Pa, time 21 min), intermediate compound II was obtained with a yield of 9.18 wt%. Ultimately, an ablation-resistant metal-modified polysiloxane-boron alkane resin was obtained and named P3. Example 4

[0041] This embodiment uses a method similar to that of Embodiment 1, except that the parameters in steps (2) and (3) are different. Specifically: (2) Under an argon atmosphere, boron trichloride, methyldichlorosilane, and another portion of hexamethyldisilazane were reacted with the intermediate compound I in a mass ratio of 1.0:2.0:8.3:1.2 to undergo a second contact reaction: First, boron trichloride and methyldichlorosilane were mixed at -40°C, and then another portion of hexamethyldisilazane was added dropwise at a rate of 4 mL / min. The mixture was heated to room temperature and reacted for 15 h. Then, the temperature was increased to 120°C at a rate of 20°C / h and reacted for 1 h. Subsequently, intermediate compound I was added, and the mixture was reacted for another 1 h. Then, the temperature was increased to 270°C at a rate of 20°C / h and reacted for 2 h. After vacuum distillation at 270°C (pressure < 100 Pa, time 19 min), intermediate compound II was obtained with a yield of 8.82 wt%. (3) Under an argon atmosphere, the intermediate compound II is subjected to a segmented heat curing treatment: The process was carried out in an inert atmosphere, with the intermediate compound II being heated to 400°C in stages at a rate of 15°C / min; wherein, the intermediate compound was held at 100°C, 200°C and 300°C for 1 hour each, and finally held at 400°C for 4 hours; the resulting ablation-resistant metal-modified polysilicon boroazine resin was named P4. Example 5

[0042] This embodiment illustrates that the method for preparing ablation-resistant metal-modified polysiloxane boronazine resin provided by the present invention is carried out according to the following steps: (1) Under an argon atmosphere, a solution containing metal chloride (solution I containing metal chloride) is subjected to a first contact reaction with a portion of hexamethyldisilazane: At -30°C, a portion of the hexamethyldisilazane was added dropwise to the solution containing the metal chloride at a rate of 3 mL / min, and then the temperature was increased to 120°C at a rate of 25°C / h, and then kept at this temperature for 2h to obtain intermediate compound I; the molar ratio of the portion of hexamethyldisilazane to the metal chloride in the solution containing the metal chloride was 2:1. (2) Under an argon atmosphere, boron trichloride, methyldichlorosilane, and another portion of hexamethyldisilazane were reacted with the intermediate compound I in a mass ratio of 1.0:2.0:8.3:0.6 to undergo a second contact reaction: First, boron trichloride and methyldichlorosilane were mixed at -40°C, and then another portion of hexamethyldisilazane was added dropwise at a rate of 4 mL / min. The mixture was heated to room temperature and reacted for 15 h. Then, the temperature was increased to 120°C at a rate of 25°C / h and reacted for 1 h. Subsequently, intermediate compound I was added, and the mixture was reacted for another 1 h. Then, the temperature was increased to 290°C at the same rate and reacted for 1 h. After vacuum distillation at 290°C (pressure < 100 Pa, time 42 min), intermediate compound II was obtained with a yield of 9.65 wt%. (3) Under an argon atmosphere, the intermediate compound II is subjected to segmented heat curing treatment: The intermediate compound II was heated to 400°C in stages at a rate of 15°C / min; wherein, it was held at 100°C, 200°C and 300°C for 1 hour each, and finally held at 400°C for 2 hours to obtain the ablation-resistant metal-modified polysiloxane-boron alkane resin, named P5. Example 6

[0043] This embodiment illustrates that the method for preparing ablation-resistant metal-modified polysiloxane boronazine resin provided by the present invention is carried out according to the following steps: (1) Under an argon atmosphere, a solution containing metal chloride (solution III containing metal chloride) is subjected to a first contact reaction with a portion of hexamethyldisilazane: At -40°C, a portion of the hexamethyldisilazane was added dropwise to the solution containing the metal chloride at a rate of 2 mL / min, and then the temperature was increased to 120°C at a rate of 20°C / h, and then kept at this temperature for 2 h to obtain intermediate compound I; the molar ratio of the portion of hexamethyldisilazane to the metal chloride in the solution containing the metal chloride was 4.1:1; (2) Under an argon atmosphere, boron trichloride, methyldichlorosilane, and another portion of hexamethyldisilazane are reacted with the intermediate compound I in a mass ratio of 1.0:2.0:7.0:1.5 to undergo a second contact reaction: First, boron trichloride and methyldichlorosilane were mixed at -35°C, and then another portion of hexamethyldisilazane was added dropwise at a rate of 2 mL / min. The mixture was heated to room temperature and reacted for 15 h. Then, the temperature was increased to 120°C at a rate of 20°C / h and reacted for 1 h. Subsequently, intermediate compound I was added, and the mixture was reacted for another 1 h. Then, the temperature was increased to 270°C at the same rate and reacted for 1 h. After vacuum distillation at 270°C (pressure < 100 Pa, time 38 min), intermediate compound II was obtained with a yield of 10.48 wt%. (3) Under an argon atmosphere, the intermediate compound II is subjected to segmented heat curing treatment: The intermediate compound II was heated to 400°C in stages at a rate of 10°C / min; wherein, it was held at 100°C, 200°C and 300°C for 0.5 h each, and finally held at 400°C for 4 h to obtain the ablation-resistant metal-modified polysilicon boronazine resin, named P6.

[0044] Comparative Example 1 This comparative example was conducted using a method similar to that of Example 1, except that intermediate compound I was not prepared. Specifically, it included: S1. Under an argon atmosphere, boron trichloride, methyldichlorosilane, and hexamethyldisilazane are reacted in a mass ratio of 1.0:1.0:8.3, including: First, boron trichloride and methyldichlorosilane were mixed at -40°C, and then hexamethyldisilazane was added dropwise at a rate of 3 mL / min. The mixture was heated to room temperature and reacted for 15 h. Then, the temperature was increased to 120°C at a rate of 20°C / h and reacted for 2 h. Finally, the temperature was increased to 270°C at the same rate and reacted for 1 h. The mixture was then distilled under reduced pressure at 270°C (pressure < 100 Pa, time 15 min) to obtain intermediate compound III with a yield of 8.71 wt%. S2. Under an argon atmosphere, the intermediate compound III is subjected to segmented heat curing treatment: The intermediate compound III was heated to 400°C in stages at a rate of 15°C / min; wherein, it was held at 100°C, 200°C and 300°C for 1 hour each, and finally held at 400°C for 4 hours; thus, a polysiloxane-boron alkane resin was obtained, named DP1.

[0045] Comparative Example 2 This comparative example was conducted using a method similar to that of Example 1, except that step (3) did not involve staged heating. Specifically: (3) Under an argon atmosphere, the intermediate compound II is subjected to heat curing treatment: The process was carried out in an inert atmosphere. The intermediate compound II was directly heated to 400°C at a rate of 10°C / min and then held at that temperature for 6 hours to obtain a polysiloxane-boronazine resin, named DP2.

[0046] Comparative Example 3 This comparative example was conducted using a method similar to that of Example 1, except that steps (1) and (2) did not involve dropwise addition. Specifically: (1) Under an argon atmosphere, a solution containing metal chloride (solution I containing metal chloride) is subjected to a first contact reaction with a portion of hexamethyldisilazane: At -40°C, a portion of the hexamethyldisilazane was added to the solution containing the metal chloride in one step, and then the temperature was increased to 120°C at a rate of 25°C / h, and then kept at that temperature for 2h to obtain intermediate compound I; the molar ratio of the portion of hexamethyldisilazane to the metal chloride in the solution containing the metal chloride was 4.1:1; (2) Under an argon atmosphere, boron trichloride, methyldichlorosilane, and another portion of hexamethyldisilazane were reacted with the intermediate compound I in a mass ratio of 1.0:2.0:8.3:0.6 to undergo a second contact reaction: Boron trichloride and methyldichlorosilane were first mixed at -40°C, and then another portion of hexamethyldisilazane was added at once. The mixture was heated to room temperature and reacted for 15 h. Then, the temperature was increased to 120°C at a rate of 25°C / h and reacted for 1 h. Subsequently, intermediate compound I was added, and the mixture was reacted for another 1 h. Then, the temperature was increased to 290°C at the same rate and reacted for 1 h. After vacuum distillation at 290°C (pressure < 100 Pa, time 15 min), intermediate compound II was obtained with a yield of 4.63 wt%. Finally, a polysiloxane-boron-alkane resin was obtained, named DP3.

[0047] The results showed that this comparative ratio not only caused the reaction rate to run out of control, but also resulted in a large amount of low-boiling-point raw materials being carried away and lost along with volatile byproducts, significantly reducing the effective utilization rate of raw materials. Ultimately, the yield of intermediate compound II, the product of the polymerization reaction, was only 50% of that of P1, which seriously deviated from the principle of atom economy.

[0048] Test Example 1 The performance of the ablation-resistant metal-modified polysiloxane and polysiloxane resins prepared in the above examples was tested: The test was conducted according to the national standard GB / T 27761-2011 "Test Methods for Weight Loss and Residual Amount of Thermogravimetric Analyzer". The results are shown in Table 1 and... Figure 2 .

[0049] in, Figure 2 The thermogravimetric curves of the ablation-resistant metal-modified polysilicon boroazine resin and polysilicon boroazine resin prepared in the embodiments of the present invention and Comparative Example 1 are shown. It can be seen from the figure that P1 has significantly better high-temperature resistance than DP1.

[0050] also, Figure 3 The scanning electron microscope images of P1 and DP2 are shown. The comparison reveals that the preparation method of DP2 causes small molecules and volatile components inside the polymer to escape rapidly. Due to the lack of sufficient diffusion relaxation time, a large number of micropores are formed inside the material, and the density is significantly reduced compared with P1, which seriously affects its subsequent application as a high-temperature resistant structural material.

[0051] Early process defects in DP2 and DP3 (such as micropores in DP2 and low yields caused by raw material entrainment due to uncontrolled reaction in DP3) lead to severe degradation of material properties, making them unsuitable for practical applications.

[0052] Table 1 The results above demonstrate that the ablation-resistant metal-modified polysiloxane-boronazine resin preparation method provided by this invention, using refractory metals as crosslinking centers, increases the density of the precursor network structure and reduces the generation of volatile organic compounds, thereby increasing the high-temperature residual rate and improving high-temperature resistance. Furthermore, at higher temperatures, the metal and matrix material can form a high-melting-point, non-volatile ceramic phase, further enhancing high-temperature resistance. This method achieves uniform embedding and precise control of refractory metal elements within the polysiloxane-boronazine molecular chain. The resin obtained by this invention exhibits excellent high-temperature and ablation resistance properties. It not only has good density but also achieves a residual mass of up to 86.10% at 800℃, a significant improvement compared to the unmodified resin (64.77%). This provides a high-performance material solution for thermal protection in extreme environments, ensuring both high residual mass and process controllability and product quality.

[0053] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing ablation-resistant metal-modified polysiloxane-boron alkane resin, characterized in that, The method includes the following steps: (1) Under an argon or nitrogen atmosphere, a portion of hexamethyldisilazane is added dropwise to a solution containing metal chloride to carry out the first contact reaction, yielding intermediate compound I; (2) Under an argon or nitrogen atmosphere, another portion of hexamethyldisilazane is first added dropwise to a mixed solution of boron trichloride and methyldichlorosilane, and then mixed with the intermediate compound I to carry out a second contact reaction to obtain intermediate compound II; (3) Under an argon or nitrogen atmosphere, the intermediate compound II is subjected to segmented heating and curing treatment to obtain the ablation-resistant metal-modified polysilicon boron alkane resin.

2. The method according to claim 1, characterized in that, In step (1), the metal chloride is selected from at least one of molybdenum chloride, tungsten chloride, titanium chloride, zirconium chloride, yttrium chloride, lanthanum chloride, niobium chloride, nickel chloride, hafnium chloride, samarium chloride, vanadium chloride, rhodium chloride, holmium chloride, cobalt chloride, chromium chloride, and tantalum chloride.

3. The method according to claim 1 or 2, characterized in that, In step (1), the operation of the first contact reaction includes: adding a portion of the hexamethyldisilazane dropwise to the solution containing the metal chloride at -40°C to -10°C, then heating to 100-130°C at a rate of 10-30°C / h, and then holding at the temperature for 1-3h to obtain intermediate compound I.

4. The method according to claim 1 or 2, characterized in that, In step (1), the molar ratio of the portion of hexamethyldisilazane to the metal chloride in the solution containing the metal chloride is 2-6:

1.

5. The method according to claim 1 or 2, characterized in that, In step (2), the operation of the second contact reaction includes: first, mixing the boron trichloride and the methyldichlorosilane at -40°C to -10°C, then adding the other part of hexamethyldisilazane dropwise, and heating to 22-28°C for 15 hours; then heating to 100-130°C at a rate of 10-30°C / h for 0.5-2 hours; then adding the intermediate compound I, continuing the reaction for 0.5-2 hours, and then heating to 220-320°C at the same rate for 1-2 hours, and obtaining the intermediate compound II by vacuum distillation.

6. The method according to claim 1 or 2, characterized in that, In step (2), the mass ratio of boron trichloride, methyl dichlorosilane, another portion of hexamethyldisilazane to intermediate compound I is 1:0.5-2:5-12:0.5-2.

7. The method according to claim 1 or 2, characterized in that, In step (3), the segmented heating and curing process includes: heating the intermediate compound II to 350-400℃ in stages at a rate of 5-20℃ / min under an argon or nitrogen atmosphere; wherein, the intermediate compound II is held at 100℃, 200℃ and 300℃ for 0.5-2h each, and finally held at 350-400℃ for 1-6h to obtain the ablation-resistant metal-modified polysiloxane-boron nitride resin.

8. The method according to claim 1 or 2, characterized in that, In step (1), the solution containing the metal chloride is a solution obtained by dissolving the metal chloride in a solvent, and the solvent is selected from at least one of anhydrous toluene, anhydrous xylene, anhydrous tetrahydrofuran, and anhydrous N,N-dimethylformamide.

9. An ablation-resistant metal-modified polysiloxane-boron alkane resin prepared by any one of claims 1-8.

10. The use of the ablation-resistant metal-modified polysiloxane nitride resin of claim 9 in the preparation of thermal protection materials or ceramic precursors.

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