A Schiff base silane complex transition metal modified ablative resistant resin matrix material, its preparation method and use

Abstract

The application provides a Schiff base silane complex transition metal modified ablation resistant resin matrix material and a preparation method and application thereof, and belongs to the field of thermal protection materials. A silane coupling agent with a hydroxyl-substituted aromatic Schiff base structure is synthesized, and a certain amount of the coupling agent is added to traditional silane and a thermosetting resin as raw materials, so that the compatibility of the organic silicon and the thermosetting resin is significantly improved. On the other hand, the introduction of the Schiff base structure improves the ability of the system to stably chelate transition metals, and the transition metals can be uniformly introduced into the thermosetting resin crosslinking network. The synergistic effect of the two significantly improves the ablation resistance of the material. The material has excellent ablation resistance, has a wide application prospect in the field of thermal protection materials, and is suitable for the fields of thermal protection of aircraft related structures in harsh thermal environments such as high-temperature gas and aerodynamic heat flow scouring.

Description

Technical Field

[0001] This invention belongs to the field of thermal protection materials, specifically relating to a Schiff base silane complexed transition metal modified ablation-resistant resin matrix material, its preparation method, and its uses. Background Technology

[0002] Thermal protection materials are crucial for the safe operation of spacecraft in extreme environments. With the rapid development of flight technology, the thermal environments faced by new-generation spacecraft are becoming increasingly demanding.

[0003] Resin-based ablation-resistant heat-resistant materials offer high heat protection efficiency and are currently the most widely used type of heat-resistant material. Phenolic resins, due to their simple molding process, good heat resistance, high mechanical strength, and outstanding instantaneous high-temperature ablation resistance, are often used as ablation-resistant heat-resistant structures and heat-resistant layer matrices. Phenolic resin-based composite materials play a crucial role in aircraft thermal protection composite materials.

[0004] Although traditional phenolic resin-based composite materials have excellent ablation performance and high material strength, the carbon layer produced by phenolic resin during the ablation process is mostly amorphous carbon, which has poor oxidation resistance, thermal stability and mechanical properties. It is easily ablated and sheared by aerodynamic forces, leading to severe ablation failure. This makes it difficult to meet the requirements of high heat resistance, oxidation resistance and maneuver overload resistance for the high Mach, high maneuverability and multi-space development of future aircraft.

[0005] On the one hand, polysiloxanes are polymers with excellent thermal stability and ablation properties. They can undergo in-situ ceramization during high-temperature carbonization, and are therefore widely used to modify polymers such as phenolic resins, epoxy resins, polyimides, polybenzoxazine, and polyurethanes to improve their flame retardant or ablation properties in aerobic environments. Organosilicones, through blending or chemical bonding into the resin network, can generate silica inorganic liquid films and silicon carbide ceramics in situ during ablation and carbonization, enhancing the material's resistance to thermomechanical and chemical-thermal oxidation losses on the ablated surface carbon layer. On the other hand, catalytic graphitization is an effective method for in-situ generation of graphite nanostructures within non-graphitic carbon (such as thermosetting resins) under the catalysis of transition metals (such as Ni, Co, Cu, and Fe). During carbonization, transition metal elements react with the amorphous glassy carbon framework or absorb hydrocarbon atmospheres, generating different types of graphite nanostructures through rearrangement of the amorphous structure. Generally, in order to obtain higher graphitization catalytic efficiency, a large amount of catalyst must be well dispersed in phenolic resin at the micron or nanoscale by mechanical blending or dissolution in a co-solvent.

[0006] Therefore, it is of great significance to develop a modified ablation-resistant resin with excellent antioxidant properties and char layer quality. Summary of the Invention

[0007] To overcome the aforementioned problems in existing technologies, and combining the advantages of polysiloxane modification to enhance antioxidant properties and catalytic graphitization to improve carbon layer quality, this invention aims to design a novel multifunctional silane coupling agent based on the molecular structure of hybrid resins. This agent improves the compatibility between the two phases while achieving coordination of transition metals. By chelating different types of transition metals, it plays a catalytic role in graphitization (Ni, Co, Cu, and Fe, etc.) or ceramicization (Ti, Zr, and Hf, etc.) during resin carbonization, further enhancing the ablation performance of phenolic resins. Hydroxyl-substituted Salenyl Schiff bases can react with phenolic resins under suitable conditions. Therefore, this invention designs and synthesizes a silane coupling agent with a hydroxyl-substituted aromatic Schiff base structure. The hydroxyl-substituted aromatic ring structure in the coupling agent provides reaction sites with phenolic resins, while the Schiff base structure provides chelation sites for stable coordination of transition metals. The silane coupling agent with a hydroxyl-substituted aromatic Schiff base structure designed and synthesized in this invention provides a new method for uniformly introducing transition metal elements into the crosslinking network of organosilicon hybrid phenolic resins.

[0008] This invention provides a Schiff base silane complexed transition metal modified resin, which is a composite material prepared from Schiff base silane coupling agent, thermosetting resin, alkoxysilane, organic acid, water and transition metal salt as raw materials.

[0009] The ratio of the Schiff base silane coupling agent, thermosetting resin, alkoxysilane, organic acid, water and transition metal salt is (0.01-50)g:(100-500)g:(100-500)g:(0-50)g:(0-50)g:(0-5)mol.

[0010] Further, the ratio of the Schiff base silane coupling agent, thermosetting resin, alkoxysilane, organic acid, water, and transition metal salt is (10-20)g:(140-160)g:(100-200)g:(0-10)g:(0-44.85)g:(0-0.022)mol, preferably 14.41g:150g:140g:(0-9.74)g:44.85g:(0-0.022)mol;

[0011] The thermosetting resin is a phenolic resin or a modified phenolic resin, preferably a boron phenolic resin or a modified boron phenolic resin; the alkoxysilane is methyltriethoxysilane, isobutyltriethoxysilane, γ-aminopropyltriethoxysilane, trimekoxysilane, or dialkoxysilane; the organic acid is acetic acid, formic acid, propionic acid, butyric acid, citric acid, lactic acid, malic acid, or tartaric acid; the transition metal salt is a nickel salt, iron salt, copper salt, chromium salt, cobalt salt, scandium salt, titanium salt, vanadium salt, manganese salt, zinc salt, rhodium salt, or palladium salt.

[0012] Furthermore, the transition metal salt is a transition metal chloride salt.

[0013] Furthermore, the ratio of the Schiff base silane coupling agent, thermosetting resin, alkoxysilane, organic acid, water and transition metal salt is 14.41g:150g:140g:(3.90-9.74)g:44.85g:0mol.

[0014] Furthermore, the ratio of the Schiff base silane coupling agent, thermosetting resin, alkoxysilane, organic acid, water and transition metal salt is 14.41g:150g:140g:3.90g:44.85g:0.022mol.

[0015] Furthermore, the Schiff base silane coupling agent is a product obtained by reacting an aminoalkoxysilane with salicylaldehyde or its derivative;

[0016] The mass ratio of the aminoalkoxysilane to salicylaldehyde or its derivative is 10:(3-5), preferably 10:4.41;

[0017] The aminoalkoxysilane is any one or a mixture of two or more of 3-aminopropyltriethoxysilane, aminopropyltrimethoxysilane, bis(tert-butylamino)silane, and 4-anilinetriethoxysilane.

[0018] Further, the Schiff base silane coupling agent is prepared by the following method: reacting an aminoalkoxysilane with salicylaldehyde or its derivative in an organic solvent to obtain the Schiff base silane coupling agent; wherein the reaction temperature is 40-70℃ and the reaction time is 1-4 hours; the mass ratio of the aminoalkoxysilane to the organic solvent is 10:(50-200).

[0019] Preferably, the organic solvent is ethanol, the reaction temperature is 60°C, and the reaction time is 2 hours; the mass ratio of the aminoalkoxysilane to the organic solvent is 10:100.

[0020] The present invention also provides a method for preparing the above-mentioned Schiff base silane complexed transition metal modified resin, the method comprising the following steps:

[0021] (a) Thermosetting resin, alkoxysilane, Schiff base silane coupling agent, water and organic acid are added to an organic solvent and reacted. After the reaction is completed, a resin solution is obtained.

[0022] (b) The organic solvent solution of the transition metal salt is added to react, and the organic solvent is removed after the reaction is completed to obtain the intermediate;

[0023] (c) Solidify the intermediate to obtain the final product.

[0024] Further, the organic solvents mentioned in steps (a) and (b) are alcohol solvents; the reaction temperature in step (a) is 80-100℃, the time is 2-8 hours, and the mass ratio of thermosetting resin to organic solvent is 150:(100-200); the reaction temperature in step (b) is 40-80℃, the time is 2-8 hours, and the molar mass ratio of transition metal salt to organic solvent in the organic solvent solution of transition metal salt is (0.002-0.022) mol:200g;

[0025] Preferably, the organic solvent in steps (a) and (b) is ethanol; the reaction temperature in step (a) is 80°C and the reaction time is 4 hours; the reaction temperature in step (b) is 60°C and the reaction time is 4 hours.

[0026] This invention also provides the use of the above-mentioned Schiff base silane complexed transition metal modified resin in thermal protection materials, ablation-resistant materials, and fireproof materials.

[0027] Furthermore, the thermal protection materials include aircraft thermal protection structural materials and engine thermal protection materials.

[0028] This invention synthesizes a silane coupling agent with a hydroxyl-substituted aromatic Schiff base structure. Using traditional silanes and thermosetting resins as raw materials, the addition of a certain amount of coupling agent significantly improves the compatibility between organosilicon and thermosetting resins. Furthermore, the introduction of the Schiff base structure enhances the system's ability to stably chelate transition metals, allowing the transition metals to be uniformly incorporated into the thermosetting resin crosslinking network. The combined effect of these two factors significantly improves the material's ablation resistance. The material of this invention exhibits excellent ablation resistance and has broad application prospects in the field of thermal protection materials. It is suitable for preparing structural components and protective materials for aircraft and related equipment that must withstand harsh environments such as high-temperature exhaust gases and aerodynamic heat flow.

[0029] The Schiff base silane coupling agent modified boron phenolic resin prepared by this invention has significantly improved ablation resistance and heat resistance. Among them, the Schiff base silane coupling agent modified boron phenolic resin of Example 4 has the lowest linear ablation rate and the best ablation resistance; the Schiff base silane coupling agent modified boron phenolic resin of Example 5 has the highest residual weight at 800℃ and the best heat resistance.

[0030] Furthermore, in the transition metal / Schiff base silane coupling agent modified boron phenolic resin prepared based on the Schiff base silane coupling agent modified boron phenolic resin of Example 4, when the transition metal is copper, the copper / Schiff base silane coupling agent modified boron phenolic resin has the lowest linear ablation rate and the best ablation resistance. When the same transition metal is used, adding more transition metal to the Schiff base silane coupling agent modified boron phenolic resin does not necessarily improve the heat resistance of the modified boron phenolic resin. Instead, it is necessary to control the specific amount of transition metal added according to this invention.

[0031] The Schiff base silane coupling agent modified boron phenolic resin of this invention has broad application prospects in the field of thermal protection materials. It is suitable for preparing structural components and protective materials for structural components that need to withstand the harsh environment of high-temperature combustion gases and aerodynamic heat flow in aircraft and related equipment.

[0032] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions or alterations can be made without departing from the basic technical concept of the present invention.

[0033] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Attached Figure Description

[0034] Figure 1 The resin solution is prepared by a single-step method.

[0035] Figure 2 SBPR and SNBPR resin solutions

[0036] Figure 3 Infrared spectra of boron phenolic resin modified with Schiff base coupling agent: (a) uncured, (b) cured, and (c) cured; XPS spectra of Si2p and B1s of the modified resin after curing; (f) 29Si solid-state NMR spectrum of the uncured resin; SEM morphology of the brittle fracture surface and its Si elemental mapping; (g) SBPR. 50-4 (h)SBPR B50-4 .

[0037] Figure 4 The images show (a) the SAXS spectrum and (b) the XRD spectrum of the cured resin.

[0038] Figure 5Transition metal / Schiff base silane coupling agent modified boron phenolic resin ethanol solution: (a) fluorescence spectrum, (c) ultraviolet spectrum; Iron / Schiff base silane coupling agent modified boron phenolic resin ethanol solution: (b) fluorescence spectrum, (d) ultraviolet spectrum; SFeBPR 50-3(11 / 9) Samples: (e) XPS, (f) TEM, (gj) elemental distribution of the mapping in Figure g.

[0039] Figure 6 The image shows the height contour (ah) and 3D morphology (ip) of the sample surface after 30 s ablation: (a, i) pure boron phenolic resin, (b, j) SBPR. B50-0 , (c, k)SBPR 50-0 , (d, l)SBPR 50-1 , (e, m)SBPR 50-2 , (f, n)SBPR 50-3 , (g, o)SBPR 50-4 , (h, p)SBPR B50-4 (q) Profile outline, (r) Line ablation rate distribution and (s) Width of ablation retreat region.

[0040] Figure 7 The linear ablation rate (a) and mass ablation rate (b) of the sample after 30 s of ablation are shown.

[0041] Figure 8 The thermogravimetric curves (a, c) and the residual weight at 800℃ (b, d) of each hybrid resin after curing are shown.

[0042] Figure 9 Thermogravimetric curves of modified phenolic resins obtained with different amounts of transition metals under nitrogen atmosphere. Detailed Implementation

[0043] Boron phenolic resin (BPR): Shaanxi Taihang Flame Arrestor Company, THC-400 boron phenolic resin, gel speed 70~100s / 200℃, free phenol content less than 7%, yellow blocky.

[0044] Methyltriethoxysilane (MTOS); 3-aminopropyltriethoxysilane (APTES); salicylaldehyde (SD); ethanol (Ethanol).

[0045] The raw materials and equipment used in this invention are all known products, obtained by purchasing commercially available products.

[0046] Table 1 Raw material formulations for each sample

[0047]

[0048]

[0049] Example 1: Schiff base silane coupling agent modified boron phenolic resin (SBPR) of the present invention 50-0 Preparation of )

[0050] Step 1. Preparation of Schiff base silane coupling agent (ATSD)

[0051] 10 g (0.045 mol) of 3-aminopropyltriethoxysilane, 4.41 g (0.036 mol) of salicylaldehyde, and 100 g of ethanol were added to a flask. The oil bath was heated to 60 °C and kept at this temperature for 2 hours under an inert atmosphere to obtain a bright yellow ethanol solution containing a Schiff base silane coupling agent. An excess of 3-aminopropyltriethoxysilane was used to ensure complete reaction of salicylaldehyde in the system. The remaining 3-aminopropyltriethoxysilane in the system also played a coupling role in subsequent reactions.

[0052] Step 2. The Schiff base silane coupling agent modified boron phenolic resin (SBPR) of the present invention 50-0 Preparation of )

[0053] Add 150g of boron phenolic resin and 200g of ethanol to a flask and stir at room temperature until the boron phenolic resin is completely dissolved. Then add 140g of methyltriethoxysilane and stir until evenly dispersed. Finally, add the ethanol solution of the Schiff base silane coupling agent prepared in step 1 of Example 1. Heat the oil bath to 80°C and react for 4 hours under an inert atmosphere to obtain the resin solution.

[0054] After the reaction was completed, the resin solution was concentrated by rotary evaporation and treated in a vacuum oven at 60°C for 12 hours to remove the solvent from the resin, thereby obtaining boron phenolic resin powder modified with Schiff base silane coupling agent.

[0055] The obtained modified boron phenolic resin powder was molded and cured. The curing process was as follows: 110℃ without pressure, held for 30 min; 110℃ to 140℃, heating rate 5℃ / min; 140℃, held for 30 min, and gradually increased pressure to 12-15 MPa; 140℃ to 180℃, heating rate 5℃ / min, maintaining pressure 12-15 MPa; 180℃, held for 2 h, maintaining pressure 12-15 MPa; 180℃ to 200℃, heating rate 5℃ / min, maintaining pressure 12-15 MPa; 200℃, held for 1 h, maintaining pressure 12-15 MPa; finally, maintaining pressure 12-15 MPa and naturally cooling to room temperature, thus obtaining the Schiff base silane coupling agent modified boron phenolic resin ablation resistant material.

[0056] Examples 2-3: Schiff base silane coupling agent modified boron phenolic resin of the present invention (Example 2 SBPR) 50-1 Example 3SBPR 50-2 Preparation of )

[0057] Take 150g of boron phenolic resin and SBPR according to Table 1 50-1 SBPR 50-2 The corresponding amount of ethanol in the sample formulation was added to the flask and stirred at room temperature until the boron phenolic resin was completely dissolved. Then, 140g of methyltriethoxysilane was added and stirred until evenly dispersed. Finally, the Schiff base-containing silane coupling agent solution prepared in step 1 of Example 1 was added. The oil bath was heated to 80°C, and under an inert atmosphere, a deionized water mixture solution (the amount added is shown in Table 1) was added dropwise to the flask through a constant pressure dropping funnel. After the addition was complete, the reaction was continued at 80°C for 4 hours to obtain the resin solution.

[0058] After the reaction was completed, the resin solution was concentrated by rotary evaporation and treated in a vacuum oven at 60°C for 12 hours to remove the solvent from the resin, thereby obtaining boron phenolic resin powder modified with Schiff base silane coupling agent.

[0059] The material is molded and cured using the same curing process as in Example 1, resulting in the Schiff base silane coupling agent modified boron phenolic resin ablation resistant material SBPR. 50-1 SBPR 50-2 .

[0060] Examples 4-5: Schiff base silane coupling agent modified boron phenolic resin of the present invention (Example 4 SBPR) 50-3 Example 5 SBPR 50-4 Preparation of )

[0061] Add 150g of boron phenolic resin and 100g of ethanol to a flask and stir at room temperature until the boron phenolic resin is completely dissolved. Then add 140g of methyltriethoxysilane and stir until evenly dispersed. Finally, add the ethanol solution of the Schiff base silane coupling agent prepared in step 1 of Example 1. Heat the oil bath to 80°C and add a mixture of acetic acid (addition amount corresponds to Table 1) and deionized water (44.85g of deionized water) dropwise to the flask through a constant pressure dropping funnel under an inert atmosphere. After the addition is complete, continue the reaction at 80°C for 4 hours to obtain the resin solution.

[0062] After the reaction was completed, the resin solution was concentrated by rotary evaporation and treated in a vacuum oven at 60°C for 12 hours to remove the solvent from the resin, thereby obtaining boron phenolic resin powder modified with Schiff base silane coupling agent.

[0063] The material is molded and cured using the same curing process as in Example 1, resulting in the Schiff base silane coupling agent modified boron phenolic resin ablation resistant material SBPR. 50-3 SBPR 50-4 .

[0064] As can be seen from the results of Experimental Example 4 below, the Schiff base silane coupling agent modified boron phenolic resin prepared according to the method of Example 4 of this invention has the lowest linear ablation rate and the best ablation resistance. Therefore, Examples 6-16, based on the Schiff base silane coupling agent modified boron phenolic resin of Example 4, further provide a method for preparing transition metal / Schiff base silane coupling agent modified boron phenolic resin.

[0065] Examples 6-16: Boron phenolic resin (SXBPR) modified with the transition metal / Schiff base silane coupling agent of the present invention. 50-3(Y) Preparation of ablation-resistant materials

[0066] Table 2 SXBPR 50 -3(Y) Sample Raw Material List (SXBPR) 50 In -3(Y), X represents the type of transition metal; Y represents the molar number of transition metals (0.0018).

[0067]

[0068] I. Preparation of SFeBPR 50-3(11 / 9)

[0069] 0.5947g (0.0022mol Fe) 3+ Prepare a ferric chloride ethanol solution by dissolving ferric chloride in 20g of ethanol.

[0070] Following the method of Example 4, a resin solution was prepared using the raw materials listed in Table 2, excluding the transition metal and ethanol (for resin preparation). After the resin solution was cooled to 60°C, ferric chloride ethanol solution was added dropwise to the flask through a constant-pressure dropping funnel under an inert atmosphere. After the addition was complete, the reaction was continued at 60°C for 4 hours.

[0071] After the reaction was completed, the solvent in the resin was removed by rotary evaporation and vacuum drying to obtain iron / Schiff base silane coupling agent modified boron phenolic resin powder (SFeBPR).

[0072] The material is molded and cured using the same curing process as in Example 1, resulting in the iron / Schiff base silane coupling agent modified boron phenolic resin ablation resistant material SFeBPR. 50-3(11 / 9) .

[0073] II. Preparation of the remaining samples in Table 2

[0074] Refer to SFeBPR 50-3(11 / 9) The preparation methods were used to prepare the remaining samples in Table 2.

[0075] Example 17: Preparation of the Schiff base silane coupling agent of the present invention

[0076] 10 g (0.045 mol) of 3-aminopropyltriethoxysilane, 4.41 g (0.036 mol) of salicylaldehyde, and 100 g of ethanol were added to a flask. The oil bath was heated to 60 °C and kept at this temperature for 2 hours under an inert atmosphere to obtain a bright yellow ethanol solution containing a Schiff base silane coupling agent. An excess of 3-aminopropyltriethoxysilane was used to ensure complete reaction of salicylaldehyde in the system. The remaining 3-aminopropyltriethoxysilane in the system also played a coupling role in subsequent reactions.

[0077] Example 18: Preparation of the Schiff base silane coupling agent of the present invention

[0078] 10 g (0.045 mol) of 3-aminopropyltriethoxysilane, 3.4 g (0.028 mol) of salicylaldehyde, and 50 g of ethanol were added to a flask. The oil bath was heated to 70 °C and kept at this temperature for 2 hours under an inert atmosphere to obtain a bright yellow ethanol solution containing a Schiff base silane coupling agent. An excess of 3-aminopropyltriethoxysilane was used to ensure complete reaction of salicylaldehyde in the system. The remaining 3-aminopropyltriethoxysilane in the system also played a coupling role in subsequent reactions.

[0079] Example 19: Preparation of the Schiff base silane coupling agent of the present invention

[0080] 10 g (0.045 mol) of 3-aminopropyltriethoxysilane, 4 g (0.036 mol) of salicylaldehyde, and 100 g of ethanol were added to a flask. The oil bath was heated to 65 °C and kept at this temperature for 2 hours under an inert atmosphere to obtain a bright yellow ethanol solution containing a Schiff base silane coupling agent. An excess of 3-aminopropyltriethoxysilane was used to ensure complete reaction of salicylaldehyde in the system. The remaining 3-aminopropyltriethoxysilane in the system also played a coupling role in subsequent reactions.

[0081] The following is the method for preparing the control sample.

[0082] Comparative Example 1, Silane-modified boron phenolic resin (SBPR) B50-0 Preparation of )

[0083] 150g of boron phenolic resin, 150g of methyltriethoxysilane, and 300g of ethanol were added to a flask and stirred at room temperature until completely dissolved. The oil bath was heated to 80℃ and reacted under an inert atmosphere for 4 hours. After the reaction was complete, the solvent in the resin was removed by rotary evaporation and a vacuum oven to obtain silane-modified boron phenolic resin powder.

[0084] The material is molded and cured using the same curing process as in Example 1, resulting in a silane-modified boron phenolic resin ablation-resistant material (SBPR). B50-0 ).

[0085] Comparative Example 2, Silane-modified boron phenolic resin (SBPR) B50-4 Preparation of )

[0086] 150g of boron phenolic resin, 150g of methyltriethoxysilane, and 200g of ethanol were added to a flask and stirred at room temperature until completely dissolved. An oil bath was heated to 80°C, and a mixed solution of acetic acid and deionized water (9.74g acetic acid and 44.85g deionized water) was added dropwise to the flask through a constant-pressure dropping funnel under an inert atmosphere. After the addition was complete, the reaction was continued at 80°C for 4 hours. After the reaction was completed, the solvent in the resin was removed by rotary evaporation and a vacuum oven to obtain silane-modified boron phenolic resin powder.

[0087] The material is molded and cured using the same curing process as in Example 1, resulting in a silane-modified boron phenolic resin ablation-resistant material (SBPR). B50-4 ).

[0088] Comparative Example 3: Preparation of Cured Boron Phenolic Resin (BPR')

[0089] Boron phenolic resin powder (BPR) was used for compression molding and then cured. The curing process was the same as in Example 1, thus obtaining boron phenolic resin ablation resistant material (BPR').

[0090] The following experimental examples demonstrate the beneficial effects of the present invention.

[0091] Experiment Example 1: Screening Experiment for the Preparation Method of Boron Phenolic Resin Modified by Transition Metal / Schiff Base Silane Coupling Agent I. Experimental Methods

[0092] Taking Example 9 as an example, the preparation method involves reacting Schiff base silane coupling agent with boron phenolic resin and methyltriethoxysilane at 80°C for a period of time, followed by the dropwise addition of Ni at 60°C. 2+ Low-temperature chelation was performed.

[0093] The screening control experiment used Schiff base silane coupling agent, boron phenolic resin, methyltriethoxysilane and Ni 2+ The single-step reaction process involves the following steps:

[0094] Add 150g of boron phenolic resin and 200g of ethanol to a flask and stir at room temperature until the boron phenolic resin is completely dissolved. Then add 140g of methyltriethoxysilane and stir until evenly dispersed. Finally, add the ethanol solution of the Schiff base silane coupling agent prepared in step 1 of Example 1. Heat the oil bath to 80°C and add nickel chloride ethanol solution dropwise to the flask through a constant pressure dropping funnel under an inert atmosphere. After the addition is complete, continue the reaction for 4 hours.

[0095] II. Experimental Results

[0096] The resin solution prepared using the screening control test method may have the following problems:

[0097] After about 1 hour of reaction, from Figure 1 As can be seen, the resin solution is opaque, and a large amount of precipitate will be formed in the reaction system, indicating that the silane condenses rapidly, leading to severe phase separation.

[0098] In Example 9 of this invention, a pre-reaction and chelation reaction were performed at two different temperatures. First, the Schiff base silane coupling agent and boron phenolic resin were pre-reacted at 80°C for 4 hours. Then, the system was cooled to 60°C. The resulting SBPR resin solution was then subjected to a low-temperature chelation reaction by adding a nickel chloride-containing ethanol solution. The degree of silane condensation within the system was controlled to obtain a SNBPR resin solution. Both the SBPR and SNBPR resin solutions were uniform and transparent. 2+ The resin color deepens after chelation (e.g.) Figure 2 The fact that it does not fade even after prolonged storage indicates that Ni... 2+ Stable coordination within the system.

[0099] Experimental results show that the resin solution obtained by the two-stage method in Example 9 of the present invention is stable and transparent. When metal ions are chelated by the method of Example 9 of the present invention, the metal ions are stably coordinated in the system. After chelation, the resin color deepens and does not fade over time.

[0100] Experimental Example 2: Structural Characterization of the Boron Phenolic Resin Modified by the Schiff Base Silane Coupling Agent of the Present Invention

[0101] I. Experimental Methods

[0102] Infrared spectroscopy test Figure 3 (ac) and 29Si solid-state NMR Figure 3 (f) Characterizing the structural changes of the modified resin before, during, and after curing. This was achieved using X-ray photoelectron spectroscopy (XPS). Figure 3 (d, e) characterize the structural differences of the modified resin after curing. The organosilicon phases and Si elemental distribution are characterized by scanning electron microscopy (SEM) morphology images of the brittle fracture surface of the cured resin and its mapping mode. Figure 3 (g, h).

[0103] SBPR 50-0 and SBPR 50-3 Small-angle X-ray diffraction (SAXS) tests were performed, and the experimental results are as follows: Figure 4 As shown in Figure a, X-ray diffraction (XRD) tests were performed on each cured resin, and the experimental results are as follows. Figure 4 As shown in b.

[0104] II. Experimental Results

[0105] Figure 3 a and Figure 3 In the infrared spectrum of the resin before and after curing, 1635 cm⁻¹ -1The peak at -CH=N indicates the successful introduction of the Schiff base structure. (960 cm⁻¹) -1 and 910cm -1 The peaks at Si-O-Ph and Si-OB indicate that organosilicones covalently attach siloxanes to phenolic resins through reactions with phenolic and boron hydroxyl groups.

[0106] Figure 3 b 960cm -1 The Si-O-Ph bond strength continuously weakens, indicating that there is some loss during the curing process. And at 1226 cm⁻¹... -1 The Ar-OH elution peak gradually weakens, indicating that as the curing reaction proceeds, the B-OH and Ph-OH in the system gradually react completely.

[0107] Figure 3 As can be seen in d, with the increase of deionized water / acetic acid and the decrease of ethanol, the relative content of Si-O-Si bonds in the Si element in the system gradually increases, from 32.3% in SBPR50-0 to 53.4% ​​in SBPR50-4, indicating that the degree of silane self-condensation in the system is continuously increasing.

[0108] Figure 3 e indicates that the B element in the cured resin participates in the resin curing process by forming BOC, BOB, and BO-Si forms. The appearance of BO-Si bonds further proves that organosilicon, through reaction with boron hydroxyl groups, covalently integrates siloxanes into the phenolic resin.

[0109] Figure 3 f indicates that as the amount of deionized water / acetic acid added increases and the amount of ethanol decreases, the number of ethoxy groups in the system continuously decreases, indicating that the degree of silane self-condensation increases.

[0110] contrast Figure 3 g and Figure 3 As can be seen, when the amount of deionized water / acetic acid added is the same as the amount of ethanol added, the addition of Schiff base coupling agent causes the organosilicon to undergo micron-level phase separation in the phenolic resin. Figure 3 h) transforms into a homogeneous system, and no obvious phase separation is observed.

[0111] Experimental results show that this invention can alter the degree of silane self-condensation within the system by adjusting the amounts of deionized water, acetic acid, and ethanol in the formulation. This invention continuously increases the degree of silane self-condensation by increasing the amounts of deionized water, acetic acid, and ethanol in the formulation. Simultaneously, the addition of a Schiff base coupling agent in this invention transforms the organosilicon in the system from a micron-scale phase separation to a homogeneous system, significantly improving the compatibility between organosilicon and boron phenolic resin, even when the degree of silane self-condensation within the system is not significantly different.

[0112] Figure 4 As can be seen, SBPR 50-0 The SAXS curve of the sample showed no scattering peaks, indicating the absence of microstructure; SBPR 50-3 The SAXS curve of the sample showed a weak scattering shoulder. Calculated using the Bragg formula (L=2π / q), the average distance between adjacent organosilicon phases was 14.3 nm. Figure 4 As can be seen in b, there is a passivated amorphous diffraction peak around 10.7°, corresponding to the organosilicon phase; for SBPR without the addition of Schiff base coupling agent... B50-4 The sample showed a significant increase in peak intensity and a narrower peak shape, indicating a larger organosilicon phase size. The experimental results further demonstrate that the addition of Schiff base coupling in this invention can significantly improve the compatibility between organosilicon and boron phenolic resin.

[0113] Experimental Example 3: Structural Characterization of Boron Phenolic Resin Modified by Transition Metal / Schiff Base Silane Coupling Agent of the Present Invention I. Experimental Methods

[0114] The fluorescence spectra of the boron phenolic resins modified with transition metal / Schiff base silane coupling agents in Examples 6-16 were detected using a fluorescence spectrometer (ethanol as solvent). The experimental results are as follows: Figure 5 a and Figure 5 As shown in b; the ultraviolet spectra of the boron phenolic resin modified with transition metal / Schiff base silane coupling agent in Examples 6-16 were detected using an ultraviolet-visible-near-infrared spectrophotometer (with ethanol as solvent), and the experimental results are as follows. Figure 5 c and Figure 5 As shown in d; the boron phenolic resin modified with iron / Schiff base silane coupling agent in Example 16 was characterized by X-ray photoelectron spectroscopy (XPS) and TEM, and the results are as follows. Figure 5 ej.

[0115] II. Experimental Results

[0116] Depend on Figure 5 As can be seen, the system underwent fluorescence quenching after the addition of equal amounts of different metal ions, proving the interaction between the transition metal and the Schiff base structure; based on the degree of quenching, it was found that the system was more reactive towards Fe... 3+ Cr 3+ and Cu 2+ Its recognition ability is superior to other transition metal ions. (By...) Figure 5 c shows that after adding equal amounts of different metal ions, the UV absorption spectra all showed significant changes (red or blue shift of the Schiff base n–π* peak; changes in peak intensity, etc.), indicating that the Schiff base structure coordinated with different metal ions to a certain extent; Figure 5 b shows that the fluorescence quenching phenomenon increases with Fe 3+ The effect gradually increases with increasing concentration; from Figure 5 d shows that the addition of Fe 3+Subsequently, a typical ligand-to-metal charge transfer transition (LMCT) of the metal complex appeared at 550 nm, and its intensity increased with increasing Fe. 3+ The fluorescence intensity increased with increasing dosage, indicating that the previous fluorescence quenching was not caused by the destruction of the Schiff base structure.

[0117] Depend on Figure 5 As can be seen from e, in some ATSDs, the C=N peak and Fe 3+ Coordination occurs, sharing electrons and reducing the electron cloud density around the N atom. This causes the peak to shift towards higher binding energies, indicating that Fe... 3+ Successfully coordinated with -CH=N in the ATSD structure; by Figure 5 As can be seen from fj, a Si-ON-Fe-rich phase was observed in keyi in the hybrid resin, which further proves that ATSD successfully chelated the transition metal.

[0118] Experimental Example 4: Test of the ablation performance of the modified boron phenolic resin of the present invention

[0119] I. Experimental Methods

[0120] According to the ablation resistance test standard GJB 323A-1996; heat flux density: 4000kW / m³ 2 Ablation time: 30s; ablation resistance test was conducted. Experimental results are as follows: Figure 6 (qs), Figure 7 And as shown in Table 2.

[0121] Table 2 Results of linear ablation rate and mass ablation rate for each cured resin

[0122]

[0123]

[0124] It can be seen that, compared with the cured boron phenolic resin (BPR') of Comparative Example 3 and the silane-modified boron phenolic resins of Comparative Examples 1 and 2, the linear ablation rate of the Schiff base silane coupling agent modified boron phenolic resins of Examples 3-5 of the present invention is significantly reduced. Among them, the Schiff base silane coupling agent modified boron phenolic resin of Example 4 has the lowest linear ablation rate and the best ablation resistance.

[0125] Further comparison of the boron phenolic resins modified with transition metal / Schiff base silane coupling agents in Examples 9-11 of this invention revealed that, under the same amount of transition metal added, when the transition metal is copper, the resulting copper / Schiff base silane coupling agent modified boron phenolic resin has the lowest linear ablation rate and the best ablation resistance.

[0126] Experimental Example 5: Heat Resistance Test of the Modified Boron Phenolic Resin of the Present Invention

[0127] Thermogravimetric analysis (TG) was used to test the thermogravimetric curves of the cured samples under nitrogen (N2) and air (Air) atmospheres, and the residual weight at 800℃ was obtained. The experimental results are as follows: Figure 8-9 And as shown in Table 3

[0128] Table 3. Residual weight (%) of each cured resin at 800℃

[0129]

[0130] from Figure 8 As can be seen from Table 3, regardless of whether it is in a nitrogen atmosphere or an air atmosphere, the residual weight of the boron phenolic resin modified with Schiff base silane coupling agent of the present invention at 800°C gradually increases with the increase of the degree of silane self-condensation. Among them, the boron phenolic resin modified with Schiff base silane coupling agent in Example 5 has the highest residual weight at 800°C in both nitrogen atmosphere and air atmosphere, and has the best heat resistance.

[0131] Further from Figure 9 As can be seen from Table 3, compared with the Schiff base silane coupling agent modified boron phenolic resin of Example 4, the iron / Schiff base silane coupling agent modified boron phenolic resin SFeBPR of Example 11 of this invention... 50-3(1 / 9) The residual weight at 800°C is increased, but the iron / Schiff base silane coupling agent modified boron phenolic resin SFeBPR of Example 16... 50-3(11 / 9) The residual weight at 800℃ actually decreased. This indicates that, with the same transition metal used, adding more transition metal to the Schiff base silane coupling agent-modified boron phenolic resin does not necessarily improve the heat resistance of the modified boron phenolic resin; rather, the specific amount of transition metal added needs to be controlled.

[0132] In summary, this invention synthesizes a silane coupling agent with a hydroxyl-substituted aromatic Schiff base structure. Using traditional silanes and thermosetting resins as raw materials, the addition of a certain amount of coupling agent significantly improves the compatibility between organosilicon and thermosetting resins. Furthermore, the introduction of the Schiff base structure enhances the system's ability to stably chelate transition metals, allowing the transition metals to be uniformly incorporated into the thermosetting resin crosslinking network. The combined effect of these two factors significantly improves the material's ablation resistance. The material of this invention exhibits excellent ablation resistance and has broad application prospects in the field of thermal protection materials. It is suitable for preparing structural components and protective materials for aircraft and related equipment that must withstand harsh environments such as high-temperature exhaust gases and aerodynamic heat flow.

Claims

1. A Schiff base silane complexed transition metal modified resin, characterized in that: It is a composite material prepared from Schiff base silane coupling agent, thermosetting resin, alkoxysilane, organic acid, water and transition metal salt as raw materials; the thermosetting resin is boron phenolic resin or modified boron phenolic resin; the Schiff base silane coupling agent is a product obtained by reacting aminoalkoxysilane and salicylaldehyde, and the aminoalkoxysilane is 3-aminopropyltriethoxysilane; The ratio of the Schiff base silane coupling agent, thermosetting resin, alkoxysilane, organic acid, water and transition metal salt is (0.01-50)g:(100-500)g:(100-500)g:(0-50)g:(0-50)g:(0.022-5)mol.

2. The Schiff base silane complexed transition metal modified resin according to claim 1, characterized in that: The ratio of the Schiff base silane coupling agent, thermosetting resin, alkoxysilane, organic acid, water and transition metal salt is (10-20)g : (140-160)g : (100-200)g : (0-10)g : (0-44.85)g : 0.022 mol; The alkoxysilane is methyltriethoxysilane, isobutyltriethoxysilane, γ-aminopropyltriethoxysilane, trimekoxysilane, or dialkoxysilane; the organic acid is acetic acid, formic acid, propionic acid, butyric acid, citric acid, lactic acid, malic acid, or tartaric acid; the transition metal salt is nickel salt, iron salt, copper salt, chromium salt, cobalt salt, scandium salt, titanium salt, vanadium salt, manganese salt, zinc salt, rhodium salt, or palladium salt.

3. The Schiff base silane complexed transition metal modified resin according to claim 2, characterized in that: The ratio of the Schiff base silane coupling agent, thermosetting resin, alkoxysilane, organic acid, water and transition metal salt is 14.41g:150g:140g:(0-9.74)g:44.85g:0.022 mol.

4. The Schiff base silane complexed transition metal modified resin according to claim 3, characterized in that: The ratio of the Schiff base silane coupling agent, thermosetting resin, alkoxysilane, organic acid, water and transition metal salt is 14.41g:150g:140g:3.90g:44.85g:0.022mol.

5. The Schiff base silane complexed transition metal modified resin according to claim 1, characterized in that: The mass ratio of the aminoalkoxysilane to salicylaldehyde is 10:(3-5).

6. The Schiff base silane complexed transition metal modified resin according to claim 5, characterized in that: The mass ratio of the aminoalkoxysilane to salicylaldehyde is 10:4.

41.

7. The Schiff base silane complexed transition metal modified resin according to any one of claims 1-6, characterized in that: The Schiff base silane coupling agent is prepared by the following method: reacting an aminoalkoxysilane with salicylaldehyde in an organic solvent to obtain the Schiff base silane coupling agent; wherein the reaction temperature is 40-70℃ and the reaction time is 1-4 hours; the mass ratio of the aminoalkoxysilane to the organic solvent is 10:(50-200).

8. The Schiff base silane complexed transition metal modified resin according to claim 7, characterized in that: The organic solvent is ethanol, the reaction temperature is 60°C, and the reaction time is 2 hours; the mass ratio of the aminoalkoxysilane to the organic solvent is 10:

100.

9. A method for preparing the Schiff base silane complexed transition metal modified resin according to any one of claims 1-8, characterized in that: The method includes the following steps: (a) A thermosetting resin, an alkoxysilane, a Schiff base silane coupling agent, water, and an organic acid are added to an organic solvent and reacted. After the reaction is complete, a resin solution is obtained. (b) The organic solvent solution of the transition metal salt is added to react, and the organic solvent is removed after the reaction is completed to obtain the intermediate; (c) Solidify the intermediate to obtain the final product.

10. The method according to claim 9, characterized in that: The organic solvents mentioned in steps (a) and (b) are alcohol solvents; the reaction temperature in step (a) is 80-100℃, the time is 2-8 hours, and the mass ratio of thermosetting resin to organic solvent is 150:(100-200); the reaction temperature in step (b) is 40-80℃, the time is 2-8 hours, and the molar mass ratio of transition metal salt to organic solvent in the organic solvent solution of transition metal salt is (0.002-0.022) mol:200g.

11. The method according to claim 10, characterized in that: The organic solvent used in steps (a) and (b) is ethanol; the reaction temperature in step (a) is 80°C and the reaction time is 4 hours; the reaction temperature in step (b) is 60°C and the reaction time is 4 hours.

12. The use of the Schiff base silane complexed transition metal modified resin according to any one of claims 1-8 in thermal protection materials, ablation-resistant materials, and fireproof materials.

13. The use according to claim 12, characterized in that: The thermal protection materials include thermal protection structural materials for aircraft and thermal protection materials for engines.

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