A poly(dimethyldiphenylisomide) siloxane / phenol formaldehyde based dual network hybrid resin and its preparation method and use

Abstract

The application provides a poly(dimethyl diphenyl imide) siloxane / phenolic based double network hybrid resin and a preparation method and application thereof, and belongs to the field of advanced material technology. The application firstly provides a copolymer for preparing an ablative thermal protection hybrid resin, and the structure of the copolymer is shown as formula I. Then, the hybrid resin prepared from the copolymer is provided. The copolymer shown as formula I and the phenolic resin in the hybrid resin of the application have good compatibility, and the copolymer is uniformly distributed in the phenolic resin; and the hybrid resin is graphitized and ceramized in the ablative process, and has excellent ablative resistance. The application provides a new idea and method for preparing a new ablative resistant hybrid phenolic resin through copolymerization, and a new ablative resistant hybrid resin which is expected to meet the increasingly severe flight environment in the future is prepared.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of advanced materials technology, and particularly relates to a poly(dimethyl diphenyl imide) siloxane / phenolic based dual network hybrid resin and a preparation method and use thereof. BACKGROUND

[0002] With the increasing interest in space exploration in the world, the environment served by the spacecraft is also more and more harsh, which accelerates the development of new materials with higher performance for spacecraft that can cope with extreme conditions. When the spacecraft enters the atmosphere, the shock between the external gas and the surface of the spacecraft will produce very serious thermal load. At this time, a thermal protection system (TPS) is needed to protect the spacecraft from the thermal load. Phenolic resin (PR) is the most widely used TPS material to date, but as the service environment becomes increasingly harsh, traditional phenolic resin has already been unable to perform its duties, and there is an urgent need for modification to meet more demanding environments.

[0003] The ceramic fillers will undergo complex endothermic reactions during ablation process, generating a protective ceramic layer to resist the erosion of heat flow. Therefore, ceramic fillers such as SiC, POSS, ZrSi2, ZrB2, etc. are often introduced into PR. Wang (Wang S, Huang H, Tian Y, et al. Effects of SiC content on mechanical, thermal and ablative properties of carbon / phenolic composites [J]. Ceramics International, 2020, 46(10): 16151-16156.) tried to introduce SiC into PR, and found that SiC can form a liquid protective film of SiO2 during ablation, thereby reducing the linear ablation rate of the material. Ding (Ding J, Yang T, Huang Z, et al. Thermal stability and ablation resistance, and ablation mechanism of carbon-phenolic composites with different zirconium silicide particle loadings [J]. Composites Part B: Engineering, 2018, 154: 313-320.) et al. found that the introduced ZrSi2 can form a SiO2-ZrO2 ceramic protective layer covering the ablation surface of the composite material. However, the interface compatibility between the introduced ceramic fillers and PR is poor, and it is difficult to disperse uniformly, and the ceramic fillers are easy to agglomerate in the PR matrix, which is undoubtedly not conducive to the further improvement of the ablation performance of the material.

[0004] To avoid the reunion phenomenon, researchers now focus on introducing ceramic elements such as B, Si, Zr, etc. into the PR matrix through chemical bonds. During the ablation process, organosilicon will undergo complex ceramic reaction to generate high-temperature ceramics such as SiO2 and SiC, which greatly improves the ablation resistance of the material, so it has attracted more and more researchers' attention. For example, Li (Li S, Han Y, Chen F, et al. The effect of structure on thermal stability and anti-oxidation mechanism of silicone modified phenolic resin [J]. Polymer Degradation and Stability, 2016, 124: 68-76.) introduced different polymerization degrees of silane into PR through Si-O-ph bond, and prepared organosilicon / phenolic hybrid resin with uniform dispersion and greatly improved thermal residual weight at 800℃. However, the molecular weight of these introduced polysiloxane is low (Mn is only a few hundred g·mol -1 ), which will produce backbiting reaction during ablation process, producing a large amount of volatile and flammable cyclic siloxane. Cyclic siloxane not only hinders the occurrence of ceramic reaction, but also destroys the integrity of the carbon layer, leading to the decline of ablation resistance. While the higher molecular weight of organosilicon resin has poor compatibility with PR, and the hybrid resin will phase separate, which will adversely affect the ablation performance. Therefore, how to balance high molecular weight and good compatibility is a key to the preparation of high-performance hybrid resin at present. SUMMARY

[0005] In order to solve the problems existing in the prior art, the present application provides a poly(dimethyl diphthalimide) siloxane / phenolic-based double network hybrid resin and its preparation method and use.

[0006] The present application provides a copolymer for preparing an ablation heat protection hybrid resin, which has the structure shown in formula I:

[0007]

[0008] wherein x is selected from an integer from 0 to 6;

[0009] y is selected from an integer from 3 to 18;

[0010] z is selected from an integer from 3 to 24.

[0011] Further,

[0012] x is selected from an integer from 1 to 2;

[0013] y is selected from an integer from 7 to 10;

[0014] z is an integer selected from 8 to 12.

[0015] Further, the aforementioned copolymer is prepared from PMP, 3,3',4,4'-biphenyl tetracarboxylic dianhydride and (3-aminopropyl)triethoxysilane as raw materials;

[0016] The PMP is synthesized by anionic ring-opening polymerization from octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl)tetramethyldisiloxane as raw materials.

[0017] Further, the aforementioned copolymer is prepared from PMP, 3,3',4,4'-biphenyl tetracarboxylic dianhydride and (3-aminopropyl)triethoxysilane as raw materials;

[0018] The molar ratio of the amino group in the PMP to the anhydride in the 3,3',4,4'-biphenyl tetracarboxylic dianhydride is 1:1 to 1.1;

[0019] The (3-aminopropyl)triethoxysilane is 0 to 40 mol% of the amino group content in the PMP;

[0020] Preferably, the (3-aminopropyl)triethoxysilane is 20 to 40 mol% of the amino group content in the PMP.

[0021] Preferably, the (3-aminopropyl)triethoxysilane is 20 to 40 mol% of the amino group content in the PMP.

[0022] Further, the aforementioned copolymer is prepared from PMP, 3,3',4,4'-biphenyl tetracarboxylic dianhydride and (3-aminopropyl)triethoxysilane as raw materials;

[0023] The molar ratio of the octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl)tetramethyldisiloxane is 0 to 6:2 to 12:0 to 4;

[0024] Preferably, the molar ratio of the octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl)tetramethyldisiloxane is 0.5 to 3:7 to 10:1 to 3;

[0025] More preferably, the molar ratio of the octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl)tetramethyldisiloxane is 0.5 to 3:7 to 9.5:2;

[0026] More preferably, the molar ratio of the octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl)tetramethyldisiloxane is 1.5:8.5:2.

[0027] Further, the preparation method of the PMP comprises the following steps:

[0028] The octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane, 1,3-bis(3-aminopropyl)tetramethyldisiloxane and catalyst are mixed, nitrogen is introduced, and then the reaction is carried out to obtain the product.

[0029] Preferably, the catalyst is selected from tetramethylammonium hydroxide;

[0030] Preferably, the reaction is carried out under vacuum.

[0031] Preferably, the reaction is carried out at 100-120℃ for 1-5h, and then heated to 150-200℃ for 0.5-5h.

[0032] More preferably, the mass of the catalyst is 0.5-5wt% of the total mass of octaphenylcyclotetrasiloxane and octamethylcyclotetrasiloxane.

[0033] The present application also provides a method for preparing the copolymer as described above, which comprises the following steps:

[0034] (1) mixing 3,3',4,4'-diphenyltetracarboxylic dianhydride and PMP in a solvent and then reacting;

[0035] (2) adding (3-aminopropyl)triethoxysilane and then continuing the reaction to obtain the copolymer.

[0036] Preferably, the solvent is tetrahydrofuran.

[0037] Preferably, the reaction temperature in step (1) is 30-50℃, and the reaction time is 1-5h.

[0038] Preferably, the reaction temperature in step (2) is 30-50℃, and the reaction time is 1-5h.

[0039] Preferably, the mass ratio of the solvent to PMP in step (1) is (1-5):1.

[0040] More preferably, the mass ratio of the solvent to PMP in step (1) is (1-5):1.

[0041] The present application also provides the use of the copolymer and the resin as described above as raw materials for preparing an ablative thermal protection hybrid resin.

[0042] Preferably, the resin is phenolic resin.

[0043] The present application also provides an ablative thermal protection hybrid resin, which is prepared by mixing and reacting the copolymer and the resin as described above, and then curing and imidizing.

[0044] Preferably, the mass ratio of the copolymer to the resin is 1:1-5.

[0045] Preferably, the reaction is carried out in a solvent.

[0046] Preferably, the reaction temperature is 80-100℃, and the reaction time is 1-10h.

[0047] Preferably, the reaction temperature is 80-100℃, and the reaction time is 1-10h.

[0048] And / or, the curing and imidization process is to hold at 100-120°C for 0.1-1 h, at 130-170°C for 1-5 h, at 180-190°C for 1-5 h, and at 200-220°C for 1-5 h in sequence;

[0049] More preferably, the resin is a phenolic resin;

[0050] And / or, the mass ratio of the copolymer to the resin is 1:2;

[0051] And / or, the solvent is anhydrous ethanol;

[0052] And / or, the solvent is removed by vacuuming before curing and imidization;

[0053] And / or, the curing and imidization process is to hold at 120°C for 0.5 h, at 160°C for 1 h, at 180°C for 1 h, and at 200°C for 2 h in sequence.

[0054] The present invention also provides the use of the aforementioned copolymer or the aforementioned ablation heat protection hybrid resin in the preparation of ablation-resistant materials;

[0055] Preferably, the ablation-resistant material is an ablation-resistant material used in extreme environments.

[0056] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0057] This invention provides a copolymer that, when mixed with and imidized with a phenolic resin, yields a hybrid resin with a dual-network structure. This hybrid resin exhibits good compatibility between the copolymer and the phenolic resin, with the copolymer being uniformly distributed within the phenolic resin. Furthermore, this hybrid resin undergoes graphitization and ceramization during ablation, demonstrating excellent ablation resistance. This invention provides a method and approach for preparing novel ablation-resistant hybrid phenolic resins through copolymerization, potentially meeting the demands of increasingly demanding future flight environments.

[0058] In this invention, PMPI undergoes graphitization and ceramization reactions during ablation to generate a carbon layer and a SiO2 liquid film covering the carbon layer. Coke and SiO2 undergo a carbothermic reduction reaction to generate SiC grains. Subsequently, the SiC grains continuously grow, increasing the viscosity and oxygen diffusion coefficient of the SiO2 liquid film. This endows the SiO2 protective layer with excellent resistance to the mechanical erosion of oxyacetylene flames and its ability to isolate oxygen. Simultaneously, the SiO2 liquid film also possesses strong radiative heat dissipation capabilities. Together, these factors significantly enhance the ablation resistance of the PMPI / PR hybrid resin.

[0059] Obviously, according to the above content of the present application, other various forms of modification, replacement or change can be made according to the common technical knowledge and usual means in the art without departing from the above basic technical idea of the present application.

[0060] The above content of the present application will be further explained in detail through the following specific embodiments. However, it should not be understood that the above subject matter of the present application is limited to the following examples. Any technology realized based on the above content of the present application belongs to the scope of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 Synthetic route of poly(dimethyldiphenylphosphineimine) siloxane / phenolic based hybrid resin of the present application: a is the synthetic route of PMP; b is the synthetic route of PMPA; c is the synthetic route of PMPI / PR hybrid resin.

[0062] Figure 2 Structural characterization results of PMP, PMPA and hybrid resin of the present application: a is the FTIR spectrum of PMP; b is the H-NMR spectrum of PMP; c is the FTIR spectrum of PMPA; d is the FTIR spectrum of hybrid resin and phenolic resin (PR). 1 H-NMR spectrum; c is the FTIR spectrum of PMPA; d is the FTIR spectrum of hybrid resin and phenolic resin (PR).

[0063] Figure 3 Scanning electron microscope (SEM) images of PMPI / PR hybrid resin with different phenyl contents: a is S0; b is S5; c is S 15 ; d is S 20 .

[0064] Figure 4 Scanning electron microscope image of pure phenolic resin (PR).

[0065] Figure 5 AFM and TEM test results of hybrid resin S 15 : a is the AFM image of S 15 ; b is the HAADF image of S 15 .

[0066] Figure 6 TGA results of PMPI / PR hybrid resin with different phenyl contents: a is 800℃, nitrogen; b is 800℃, air; c is degradation activation energy.

[0067] Figure 7 Optical images after ablation of different resins.

[0068] Figure 8The results of the ablation resistance of the PMPI / PR hybrid resin of the present application: a is the linear ablation rate of the PMPI / PR hybrid resin; b is the mass ablation rate of the PMPI / PR hybrid resin; c is a schematic diagram of the ablation layer; d is the thickness distribution of the residual resin; e is the linear ablation rate distribution; x in d and e represents the different positions of the sample cross-section starting from one end of the cross-section to a straight line in the cross-section.

[0069] Figure 9 The XRD patterns and SEM images of the carbon layer of each resin after ablation: a is the XRD pattern of the carbon layer; b is the SEM pattern of the carbon layer of PR after ablation; c is the SEM pattern of the carbon layer of S0 after ablation; d is the SEM pattern of the carbon layer of S5 after ablation; e is the SEM pattern of the carbon layer of S10 after ablation; f is the SEM pattern of the carbon layer of S15 after ablation; g is the SEM pattern of the carbon layer of S20 after ablation; h is the SEM pattern of the carbon layer of S25 after ablation; i is the SEM pattern of the carbon layer of S30 after ablation; j is the SEM pattern of the carbon layer of S35 after ablation; k is the SEM pattern of the carbon layer of S40 after ablation; l is the SEM pattern of the carbon layer of S45 after ablation; m is the SEM pattern of the carbon layer of S50 after ablation; n is the SEM pattern of the carbon layer of S55 after ablation; o is the SEM pattern of the carbon layer of S60 after ablation; p is the SEM pattern of the carbon layer of S65 after ablation; q is the SEM pattern of the carbon layer of S70 after ablation; r is the SEM pattern of the carbon layer of S75 after ablation; s is the SEM pattern of the carbon layer of S80 after ablation; t is the SEM pattern of the carbon layer of S85 after ablation; u is the SEM pattern of the carbon layer of S90 after ablation; v is the SEM pattern of the carbon layer of S95 after ablation; w is the SEM pattern of the carbon layer of S100 after ablation. 15 The SEM pattern of the carbon layer after ablation; f is the SEM pattern of the carbon layer of S 30 The SEM pattern of the carbon layer after ablation; d' is the image of the red box in d after magnification; e' is the image of the red box in e after magnification; f' is the image of the red box in f after magnification. DETAILED DESCRIPTION

[0070] The raw materials and equipment used in the specific embodiments of the present application are known products, which can be obtained by purchasing commercially available products. The full name and corresponding abbreviation of some reagents used in the specific embodiments of the present application are as follows:

[0071] Octaphenylcyclotetrasiloxane (P4), octamethylcyclotetrasiloxane (D4), (3-aminopropyl)triethoxysilane (APTES), 3,3',4,4'-diphenyltetracarboxylic dianhydride (BPDA).

[0072] Example 1, Preparation of poly(dimethyl diphenyl imide) siloxane / phenolic based double network hybrid resin of the present application

[0073] 1. Synthesis of PMP with different phenyl contents

[0074] PMP is synthesized by anionic ring-opening polymerization of D4, P4, 1,3-bis(3- aminopropyl)tetramethyldisiloxane under the catalysis of tetramethylammonium hydroxide. Specifically, D4, P4, capping agent 1,3-bis(3-aminopropyl)tetramethyldisiloxane and tetramethylammonium hydroxide (TMAOH) are added to a three-necked flask, which is first vacuumed at 60°C to remove the water in the system. Then, the system is restored to normal pressure by introducing nitrogen, and reacted at 120°C for 2.5 h. Then, the temperature of the system is increased to 150°C for 0.5 h, and the catalyst tetramethylammonium hydroxide is decomposed into trimethylamine and methanol. Finally, the system is vacuumed to remove the unreacted monomers, trimethylamine and methanol, and a colorless transparent viscous liquid is obtained, which is PMP. The synthesis route of PMP is as follows: Figure 1The raw material formula for synthesizing PMP with different phenyl content is shown in Table 1. The amount of catalyst tetramethylammonium hydroxide is 0.5wt% of the total mass of P4 and D4. In Table 1, PMP0 represents the synthesized PMP with 0% of the molar content of phenyl, PMP5 represents the synthesized PMP with 5% of the molar content of phenyl, PMP 15 represents the synthesized PMP with 15% of the molar content of phenyl, PMP 30 represents the synthesized PMP with 30% of the molar content of phenyl.

[0075] Table 1. Raw material formula for synthesizing PMP with different phenyl content

[0076]

[0077] 2. Synthesis of PMPA with different phenyl content

[0078] Under the nitrogen atmosphere, THF solution containing 50wt% PMP was added dropwise into a three-necked flask containing BPDA (the molar ratio of amino group in PMP to anhydride in BPDA is 1:1.05) and tetrahydrofuran (THF, the mass ratio of THF to PMP is 1:1), and the reaction was carried out at 35℃ for 2.5h to ensure that the molecular chain was capped with excess anhydride. Then, capping agent APTES (the amount of APTES is 20mol% of the amino content in PMP) was added, and the reaction was continued for 1h to obtain transparent viscous PMPA. The synthesis route of PMPA is shown in Figure 1 b). PMPA with different phenyl content was prepared using PMP with different phenyl content, which are respectively named as PMPA0, PMPA5, PMPA 15 , PMPA 30 .

[0079] 3. Synthesis of PMPI / PR hybrid resin with different phenyl content

[0080] PMPA was added into anhydrous ethanol solution containing 50wt% PR (the mass ratio of PR to anhydrous ethanol is 1:1), and the mass ratio of PMPA to PR is 1:2, and the reaction was carried out at 80℃ for 1h, and then the solvent was removed by vacuum at 90℃ to obtain light yellow powder. The hybrid resin was cured and imidized by hot pressing, and finally PMPI / PR hybrid resin was obtained. The curing and imidization program is 0.5h at 120℃, 1h at 160℃, 2h at 180℃, and 2h at 200℃ in sequence. The synthesis route of PMPI / PR hybrid resin is shown in Figure 1 c). PMPI / PR hybrid resin with different phenyl content was prepared using PMPA with different phenyl content, which are respectively named as S0, S5, S 15 , S 30 .

[0081] The following specific experimental examples demonstrate the beneficial effects of the present invention.

[0082] Experimental Example 1: Structural Characterization of PMP and PMPI / PR Hybrid Resins with Different Phenyl Content

[0083] 1. Experimental Methods

[0084] Fourier transform infrared spectroscopy (FTIR) was used to analyze PMP0, PMP5, and PMP prepared according to the method described in Example 1. 15 PMP 30 PMPA0, PMPA5, PMPA 15 PMPA 30 S0, S5, S 15 S 30 The test was performed using pure phenolic resin (PR); 1H NMR spectroscopy was employed. 1 H-NMR spectroscopy was used to analyze PMP0, PMP5, and PMP prepared according to the method described in Example 1. 15 and PMP 30 Conduct testing.

[0085] FTIR detection conditions: at room temperature, performed on a Nicolet IS50 spectrometer.

[0086] 1 H-NMR detection conditions: The sample was dissolved in CDCl3 and the analysis was performed on a Bruker AV III HD 400MHz spectrometer.

[0087] 2. Experimental Results

[0088] Figure 2 (a) and 2(b) give the FTIR and FTIR of PMPs with different phenyl contents. 1 H-NMR results. Figure 2 (a) 3380~3310cm -1 The absorption peak corresponds to the NH stretching vibration of the terminal amino group in the PMP molecular chain. The peaks are located in the range of 3067–3007 cm⁻¹. -1 The peaks near the phenyl group represent the CH stretching vibrations on the benzene ring, which increase with increasing phenyl content. (1132–1009 cm⁻¹) -1 The broad peaks in the vicinity correspond to the Si-O-Si backbone in the molecular chain. Figure 2 In (b), the chemical shift at 0.1 ppm corresponds to the characteristic absorption peak of the side methyl group in PMP, and the multiple peaks between 7.0 and 8.0 ppm correspond to the characteristic absorption peak of H on the benzene ring. The characteristic absorption peak of the amino group is located at 1.4 ppm, which coincides with the -C-CH2-C- in 1,3-bis(3-aminopropyl)tetramethyldisiloxane.1 The integral areas of characteristic absorption peaks of different functional groups in the H-NMR spectra were used to calculate the phenyl and amino content in PMPs with different phenyl contents, and the results are shown in Table 2. In addition, the molecular weight data of various PMPs with different phenyl contents are also listed in Table 2.

[0089] Table 2. Content of phenyl and amino groups in PMP and molecular weight of PMP

[0090]

[0091] Figure 2 In (c), at 1644cm -1 The amide I band appears at 1574 cm⁻¹, representing the C=O stretching vibration in ammonium acids. -1 The NH-angle vibration at this point corresponds to the "cyclic breathing" mode found in aromatic amines, belonging to the amide II band. This evidence indicates that amide acids have been successfully introduced into PMPA. The FTIR spectra of the cured and imidized hybrid resins are shown below. Figure 2 As shown in (d). The hybrid resin at 1775 cm⁻¹ -1 and 1716cm -1 Absorption peaks appeared nearby for both asymmetric and symmetric C=O stretching of the imide group. (1390 cm⁻¹) -1 The peak at 970 cm⁻¹ represents the CN stretching vibration in the imide group. -1 The nearby peaks belong to the Si-O-ph structure, indicating that the ethoxy group at the end of the PMPI molecular chain successfully reacted with the hydroxyl group in PR, promoting the construction of the three-dimensional cross-linked network structure.

[0092] Experimental Example 2: Microstructure of PMPI / PR hybrid resins with different phenyl contents

[0093] 1. Experimental Methods

[0094] S0, S5, and S2 prepared according to the method described in Example 1 were analyzed using SEM. 15 S 30 The pure phenolic resin (PR) was analyzed and subjected to EDS analysis. AFM and TEM were used to analyze the S... 15 Conduct testing.

[0095] SEM detection conditions: After the sample was fractured in liquid nitrogen, it was observed using a Hitachi Co. S-4800 electron microscope at an accelerating voltage of 15kV.

[0096] AFM testing conditions: Use the tapping mode on the Bruker Dimension ICON to observe the sample cross-section.

[0097] The detection condition of TEM: After the resin section was dyed with phosphotungstic acid, it was observed on Talos F200S G2.

[0098] 2. Experimental results

[0099] Figure 3 SEM test images of the cross-section of hybrid resins with different phenyl contents, Figure 4 SEM images of the cross-section of pure PR. EDS analysis showed that the silicone resins with different phenyl contents were uniformly distributed in the PR matrix, without obvious phase separation behavior. This indicates that the introduction of ethoxyl groups, imide rings and phenyl groups into the silicone chain segment can significantly improve the compatibility with PR, thereby avoiding the generation of island phase structure. To further accurately characterize the phase structure of the hybrid resin, S 15 AFM and TEM tests were performed.

[0100] Figure 5 (a) is the tapping mode of S 15 using AFM. According to the different forces between the probe and the PMPI soft chain and the PR hard chain, the hybrid resin presents a light and dark distribution of the bicontinuous structure in the phase diagram. Figure 5 (b) is the HAADF image of S 15 , and the black part is PMPI. It can be seen that PMPI is in a nanoscale co-continuous distribution in the matrix, similar to AFM. These results show that S 15 presents a microstructure of a nanoscale bicontinuous network.

[0101] Test Example 3, Thermal Property Study

[0102] 1. Experimental method

[0103] S0, S5, S 15 , S 30 and pure phenolic resin (PR) prepared according to the method described in Example 1 were subjected to thermogravimetric analysis (TGA) detection.

[0104] The detection condition of TGA: The test was performed on NETZSCH STA 449F3 at a heating rate of 10℃ / min.

[0105] 2. Experimental results

[0106] In order to evaluate the effect of the introduction of PMPI on the thermal stability of the hybrid resin, the thermal degradation behavior of the hybrid resin of the present application under nitrogen and air atmosphere was studied using TGA, and the results are shown in Figure 6 Table 3 lists the characteristic data of resin thermal degradation and heat resistance index. Under nitrogen, S0-S 30The thermal residual weight of S0, S5, S10 and S15 at 800℃ were 47%, 46%, 46% and 46%, respectively, which were lower than that of pure PR. This might be due to the introduction of PMPI which destroyed the three-dimensional network structure of PR and reduced the crosslinking degree. In air, the thermal residual weight of S0, S5, S10 and S15 at 250-350℃ increased, which might be due to the ceramic reaction of PMPI segments to form SiO2, resulting in weight gain. At 800℃, the thermal residual weight of S0-S15 were all around 10%, which was significantly higher than that of pure PR (1.9%). This was because PMPI formed a dense SiO2 protective layer under high temperature and oxygen atmosphere, which slowed down the thermal decomposition and oxidation of PR matrix to a certain extent. 15 15

[0107] The degradation activation energy E of all samples was calculated by Friedman method at a heating rate of 10℃ / min. a (Friedman method according to the method described in the literature, Paik P, Kar KK. Thermal degradation kinetics and estimation of lifetime of polyethylene particles: Effects of particle size. Materials Chemistry and Physics. 2009; 113(2-3): 953-61.) and the results are shown in Figure (c). The Ea of S0 (16.71 kJ / mol), S5 (17.29 kJ / mol), S10 (16.08 kJ / mol) were all higher than that of pure PR (11.76 kJ / mol). However, the Ea of S15 (9.62 kJ / mol) showed a significant decrease. The higher degradation activation energy of S0-S10 was mainly due to the introduction of Si-O-Si bond (446 kJ / mol) with high bond energy in the matrix, which was much higher than C-C (358 kJ / mol) and C-O (384 kJ / mol) bonds. At the same time, the introduced phenyl group could inhibit the decomposition of Si-O-Si bond, thereby increasing the degradation activation energy of hybrid resin. However, when the phenyl content was too high (S15), the large steric hindrance was not conducive to the chemical bonding and entanglement of PMPI and PR molecular chains, which greatly destroyed the three-dimensional network structure, resulting in lower degradation activation energy. These results showed that the introduction of PMPI with appropriate phenyl content should be able to inhibit the thermal degradation of hybrid resin. Figure 6 15 30 15 30

[0108] Table 3. Thermal degradation characteristic data

[0109] ​​​​​​​

[0110] T 5％ and T 30％ These are the decomposition temperatures corresponding to 5% and 30% weight loss, respectively. * T Heat-resistance index =0.49×[T 5％ +0.6×(T 30％ –T 5％ )).

[0111] Experimental Example 4: Ablation Resistance of PMPI / PR Hybrid Resin

[0112] 1. Experimental Methods

[0113] S0, S5, and S prepared according to the method described in Example 1 15 S 30 The ablation resistance of pure phenolic resin (PR) was tested.

[0114] Test method for ablation resistance: According to GJB 323A-1996, using the ZR-323A oxyacetylene ablation machine from Xi'an Zhirui Company, at 4MW / m 2 Ablation under hot flow for 30 seconds.

[0115] 2. Experimental Results

[0116] Using a heat flux of 4MW / m 2 The ablation resistance of the hybrid resin of this invention was tested using an oxyacetylene flame. Optical images of the ablated hybrid resin are shown below. Figure 7 As shown. Figure 8 (a) and (b) show the linear ablation rate (LAR) and mass ablation rate (MAR) of the resin. With the gradual increase of phenyl content, the linear ablation rate of the hybrid resin gradually decreases, and its ablation resistance improves. 15 The linear ablation rate was the lowest (0.055 mm / s), a decrease of 74.4% compared to pure PR (0.21 mm / s). However, with further increases in phenyl content, the linear ablation rate of the hybrid resin increased, and its ablation resistance decreased. Regarding the mass ablation rate, S... 15The ablation rate of the treatment (0.055 g / s) decreased by approximately 15.1% compared to pure PR (0.067 g / s). Compared with PR composites incorporating tetrasilanol octaphenyl POSS (T-POSS) (Niu Z, Li G, Ma X, et al. Synergetic effect of O-POSS and T-POSS to enhance ablative resistant of phenolic-based silica fiber composites via strong interphase strength and ceramic formation[J]. Composites Part A: Applied Science and Manufacturing, 2022, 155: 106855.) and carbon nanotubes (CNTs) (Wang ZJ, Kwon DJ, Gu GY, et al. Ablative and mechanical evaluation of CNT / phenolic composites by thermal and microstructural analyses[J]. Composites Part B: Engineering, 2014, 60: 597-602.) (LAR values ​​are 0.100 mm / s and 0.130 mm / s, respectively), S 15 The LAR value decreased significantly, and the ablation resistance was significantly improved.

[0117] The PR, S0, and S values ​​of the sample were measured using a 3D profilometer. 15 The residual thickness after ablation was calculated, and the thickness difference at each location before and after ablation was divided by the ablation time to obtain the LAR at the corresponding point. Figure 8 In (d), the ablated PR and S 15 Compared to S0, the thickness of the ablation edge region increased significantly, while S0 did not show a significant increase in thickness at the ablation edge region. In the central ablation region where the flame was most intense, S0 and S... f Compared to PR, there was no significant reduction in thickness. For example... Figure 8 As shown in (e), the introduction of an appropriate amount of phenyl group makes S 15 Compared to S0 and PR, the LAR at all points remains at a low level, with a maximum LAR of only 0.055 mm / s, approximately one-quarter that of pure PR (0.21 mm / s). In summary, the hybrid resin of this invention can effectively resist the erosion of high-heat-flux flames and is expected to withstand more demanding service environments in the future.

[0118] The carbon layer of each resin after ablation was characterized by XRD to confirm its composition, and the results are shown in Fig. Figure 9 The diffraction peak observed near 23.6° corresponds to amorphous SiO2. The peaks appearing near 35.3°, 59.9°, and 71.7° belong to the (1 1 1), (2 2 0), and (3 1 1) diffraction planes of SiC, respectively, which match the cubic structure of β-SiC. In addition, a small shoulder peak appears on the left side of the (1 1 1) peak, which is a stacking fault formed during the growth of SiC grains during ablation. The diffraction peaks at 2θ = 25.7° and 43.1° belong to the (002) and (100) reflections of graphite, indicating that the PR matrix was graphitized during ablation.

[0119] Figure 9 (b)~ (c) (d) (e) (f) Figure 9 (f) XRD and EDS mapping results show that, compared with the smooth carbon layer of pure PR, the side of the carbon layer of S0-S 30 is covered with a layer of SiO2 / SiC composite ceramic protective layer, which can help to enhance the ability of the hybrid resin to resist the impact of high-speed oxygen-containing hot gas flow. Compared with S5-S 30 , S0's carbon layer side is covered with a large number of SiO2 spheres with larger diameters, which may be due to the fact that the liquid SiO2 generated on the surface of S0's carbon layer during ablation is not strong enough to resist the high-speed and high-pressure oxygen-acetylene flame, resulting in its flowing with the hot air to the original layer. These washed-down molten SiO2 undergo nucleation, growth on the side of the carbon layer, and after the ablation ends, as the temperature decreases, the surface tension of SiO2 increases, gradually cooling to form spheres. As shown in 30 , the red box in the middle of S5-S Figure 9 (d')~ (e) (f) Figure 9 (f'), the diameter of the SiO2 spheres on the side of the carbon layer is significantly reduced, which may be related to the fact that the introduction of phenyl groups helps to increase the viscosity of the SiO2 liquid film, thereby improving its ability to resist the impact of hot gas flow.

[0120] The above experimental results show that the PMPI / PR hybrid resin of the present application has good ablation resistance, among which S 15 has the best ablation resistance.

[0121] In conclusion, the copolymer can be mixed with phenolic resin to obtain a hybrid resin with a double network structure after imidization. The hybrid resin has good compatibility between the copolymer and the phenolic resin, and the copolymer is uniformly distributed in the phenolic resin. Moreover, the hybrid resin is graphitized and ceramized during the ablation process, and has excellent ablation resistance. The application provides a new idea and method for preparing a new ablation-resistant hybrid phenolic resin by copolymerization, and a new ablation-resistant hybrid resin which is expected to meet the increasingly harsh flight environment in the future is prepared.

Claims

1. An ablative thermal protection hybrid resin, characterized in that: It is prepared by mixing the copolymer with the resin and then curing and imidizing; Formula I x is an integer selected from 1 to 6; y is an integer selected from 3 to 18; z is an integer selected from 3 to 24; The resin is a phenolic resin.

2. The ablative thermal protection hybrid resin according to claim 1, wherein: In the copolymer, x is an integer selected from 1 to 2; y is an integer selected from 7 to 10; z is an integer selected from 8 to 12.

3. The ablative thermal protection hybrid resin according to claim 1 or 2, characterized in that: The copolymer is prepared from PMP, 3,3',4,4'-biphenyl tetracarboxylic dianhydride and (3-aminopropyl) triethoxysilane as raw materials. The PMP is synthesized by anionic ring-opening polymerization from octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl) tetramethyldisiloxane as raw materials.

4. The ablative thermal protection hybrid resin according to claim 3, wherein: The molar ratio of the amino group in the PMP to the anhydride in the 3,3',4,4'-biphenyl tetracarboxylic dianhydride is 1:1 to 1.1; The (3-aminopropyl) triethoxysilane is 20 to 40 mol% of the amino content in the PMP.

5. The ablative thermal protection hybrid resin according to claim 4, wherein: The (3-aminopropyl) triethoxysilane is 20 mol% of the amino content in the PMP.

6. The ablative thermal protection hybrid resin according to claim 3, wherein: The molar ratio of the octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl) tetramethyldisiloxane is 0.5 to 6:2 to 12:1 to 4.

7. The ablative thermal protection hybrid resin according to claim 6, wherein: The molar ratio of the octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl) tetramethyldisiloxane is 0.5 to 3:7 to 10:1 to 3.

8. The ablative thermal protection hybrid resin according to claim 7, wherein: The molar ratio of the octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl) tetramethyldisiloxane is 0.5 to 3:7 to 9.5:

2.

9. The ablative thermal protection hybrid resin according to claim 8, wherein: The molar ratio of the octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl) tetramethyldisiloxane is 1.5:8.5:

2.

10. The ablative thermal protection hybrid resin of claim 3, wherein: The preparation method of the PMP comprises the following steps: Mixing octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane, 1,3-bis(3-aminopropyl) tetramethyldisiloxane and a catalyst, introducing nitrogen, and then reacting to obtain the PMP.

11. The ablative thermal protection hybrid resin according to claim 10, wherein: The catalyst is selected from tetramethylammonium hydroxide; And / or, the vacuum is pumped before the nitrogen is introduced; And / or, the reaction is carried out at 100 to 120℃ for 1 to 5h, and then heated to 150 to 200℃ for 0.5 to 5h.

12. The ablative thermal protection hybrid resin according to claim 11, characterized in that: The mass of the catalyst is 0.5 to 5wt% of the total mass of the octaphenylcyclotetrasiloxane and the octamethylcyclotetrasiloxane.

13. The ablative thermal protection hybrid resin according to claim 3, wherein: The preparation method of the copolymer comprises the following steps: (1) mixing 3,3',4,4'-biphenyl tetracarboxylic dianhydride and PMP in a solvent and then reacting; (2) adding (3-aminopropyl) triethoxysilane and then continuing to react to obtain the copolymer.

14. The ablative thermal protection hybrid resin according to claim 13, characterized in that: In step (1), the solvent is tetrahydrofuran; And / or, in step (1), the reaction temperature is 30 to 50℃, and the reaction time is 1 to 5h; And / or, in step (2), the reaction temperature is 30 to 50℃, and the reaction time is 1 to 5h.

15. The ablative thermal protection hybrid resin according to claim 14, wherein: In step (1), the mass ratio of the solvent to PMP is (1-5):

1.

16. The ablative thermal protection hybrid resin according to claim 1, wherein: the mass ratio of the copolymer to resin is 1:1-5; and / or, the reaction is carried out in a solvent; and / or, the reaction temperature is 80-100 °C; the reaction time is 1-10 h; and / or, the curing and imidization procedure is 100-120 °C for 0.1-1 h, 130-170 °C for 1-5 h, 180-190 °C for 1-5 h, and 200-220 °C for 1-5 h, in sequence.

17. The ablative thermal protection hybrid resin according to claim 16, wherein: and / or, the mass ratio of the copolymer to resin is 1:2; and / or, the solvent is anhydrous ethanol; and / or, the solvent is removed by vacuum before the curing and imidization; and / or, the curing and imidization procedure is 120 °C for 0.5 h, 160 °C for 1 h, 180 °C for 1 h, and 200 °C for 2 h, in sequence.

18. Use of the ablative thermal protection hybrid resin according to any one of claims 1-17 for the preparation of a material resistant to ablation.

19. Use according to claim 18, characterized in that: The material resistant to ablation is a material resistant to ablation for use in extreme environments.

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