Preparation method of ceramic modified epdm composite material modified by kh570

Abstract

The application discloses a preparation method of a KH570 modified ceramic modified EPDM composite material, specifically comprises the following steps: preparing a SiZrBC ceramic precursor; preparing a KH570 modified SiZrBC ceramic precursor; mixing ternary ethylene propylene rubber, the KH570 modified SiZrBC ceramic precursor, aramid fiber, boron phenolic resin, zinc oxide, stearic acid and DCP in a thin way to obtain a rubber sheet; and the rubber sheet is filled in a mold for flat plate vulcanization, and the mold is taken out and cooled, and the operation is completed. Through the chemical bonding effect of KH570, the physical blending system is changed into a structure with chemical crosslinking points, and the strong interface interaction enables stress to be effectively transmitted between the EPDM matrix and the SiZrBC rigid particles. The SiZrBC precursor provides rigid support as a reinforcing phase, and good interface bonding ensures that the matrix can effectively transmit the load to the reinforcing phase when subjected to external force, so that the reinforcing effect is achieved.

Description

Technical Field

[0001] This invention belongs to the field of rubber composite material preparation technology, specifically relating to a method for preparing KH570-modified ceramic-modified EPDM composite materials. Background Technology

[0002] Key components such as solid rocket engines, missile nose cones, and spacecraft thermal protection systems face severe challenges from the coupling of ablation and mechanical loads under extreme service environments, including instantaneous ultra-high temperatures, high-speed particle erosion, and severe thermochemical corrosion. The ablation resistance of materials directly determines the reliability, safety, and service life of related equipment. Therefore, developing novel composite materials that combine excellent ablation resistance with reliable mechanical properties has become an important cutting-edge direction in the field of thermal protection.

[0003] Ethylene propylene diene monomer (EPDM) rubber, due to its saturated molecular structure, possesses excellent resistance to heat and oxygen aging, ozone, and chemical media, as well as superior elasticity and flexibility, making it an indispensable material for thermal insulation applications in solid rocket motors. Furthermore, EPDM has a low glass transition temperature, maintaining elasticity over a wide temperature range and effectively buffering thermal stress. However, EPDM has limited high-temperature resistance and ablation resistance, and is highly susceptible to pyrolysis, oxidation, and physical corrosion in high-temperature flames, making it unsuitable for meeting extreme thermal protection requirements on its own. Therefore, a large amount of functional fillers is typically introduced into the EPDM matrix to construct an effective thermal barrier and ablation-resistant system, forming a continuous, dense, and high-strength char layer on the material surface to prevent heat and oxygen penetration, protecting the matrix material from damage.

[0004] Traditional EPDM ablation-resistant composites typically use aramid fibers, phenolic resins, and inorganic fillers as reinforcing phases. These fillers can improve the heat resistance and char residue of the material to some extent, thereby improving the ablation resistance of the EPDM composite. However, due to the poor interfacial compatibility between the fillers and the rubber matrix, dispersion uniformity and stress transfer are affected, leading to a decrease in mechanical properties. In addition, during the ablation process, the char layer structure formed by traditional inorganic fillers is loose and lacks strength, making it easily eroded and peeled off by high-speed airflow, resulting in unsatisfactory ablation resistance. To achieve a certain level of ablation resistance, high filler content is usually required, which often makes rubber mixing difficult and severely impairs the intrinsic flexibility of EPDM.

[0005] In recent years, organic-inorganic hybrid polymer ceramic precursors, such as polycarbosilane (PCS), polysilazane (PSZ), polysiloxane (PDMS), and octahedral silsesquioxane (POSS), have opened up new avenues for the preparation of high-performance polymer-derived ceramic (PDC) composites. These ceramic precursors can undergo crosslinking, pyrolysis, and in-situ transformation into advanced ceramic phases such as SiC, Si3N4, and SiOC at high temperatures, offering advantages such as relatively low transformation temperatures, high ceramic yields, controllable structures, and good compatibility with matrix composite processes. Ceramic precursors not only provide excellent high-temperature resistance but also endow materials with the ability to undergo in-situ ceramic transformation, further improving the density and strength of the ceramic matrix. However, interfacial mismatch between EPDM and fillers also exists. Furthermore, uneven distribution of fillers in the matrix can lead to cracking of the ceramic product or detachment of the ceramic layer, significantly affecting the final structure and mechanical properties of the rubber. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing KH570-modified ceramic-modified EPDM composite materials, which significantly improves the ablation resistance and high-temperature stability of the composite materials.

[0007] The technical solution adopted in this invention is a method for preparing KH570-modified ceramic-modified EPDM composite materials, specifically implemented according to the following steps: Step 1: Prepare SiZrBC ceramic precursor; Step 2: Prepare KH570 modified SiZrBC ceramic precursor; Step 3: EPDM rubber, KH570 modified SiZrBC ceramic precursor, aramid fiber, boron phenolic resin, zinc oxide, stearic acid and DCP are mixed in a thin-pass mixture to obtain a film. Step 4: Place the mold on a flat vulcanizing machine for preheating and spray with a release agent. Fill the mold with the film and perform flat vulcanization. Remove from the mold and cool to obtain KH570 modified ceramic EPDM composite material.

[0008] The invention is further characterized in that, Step 1 specifically involves: In an argon atmosphere, zirconium tetrachloride was mixed with ethanol for an organication reaction, followed by the addition of acetylacetone for a chelation reaction. Boric acid, 1,4-butanediol, hydroquinone, and tetraethyl orthosilicate were then added sequentially. After reflux condensation, the mixture was distilled under reduced pressure, cooled, and dried under vacuum to obtain the SiZrBC ceramic precursor. The molar ratio of zirconium tetrachloride, ethanol, acetylacetone, boric acid, 1,4-butanediol, hydroquinone, and tetraethyl orthosilicate was 1:20:4:3:2:1:1. The organication reaction temperature was 20-30℃, and the reaction time was 30-60 min; the chelation reaction temperature was 50-80℃, and the reaction time was 30-60 min; the reflux reaction temperature was 80-120℃, and the reaction time was 2-4 h; the vacuum drying temperature was 60-80℃, and the drying time was 12-24 h.

[0009] Step 2 specifically involves: The SiZrBC ceramic precursor obtained in step 1 was dissolved and stirred in an ethanol solution, and then KH570 hydrolysis solution was added dropwise. After reflux reaction, the mixture was distilled under reduced pressure, cooled, and dried under vacuum to obtain the KH570 modified SiZrBC ceramic precursor.

[0010] The preparation process of KH570 hydrolysis solution is as follows: KH570 is dissolved in a mixture of water and anhydrous ethanol for hydrolysis at a temperature of 40-60℃ for 1-2 hours.

[0011] The dissolution temperature is 30-60℃, and the dissolution time is 10-30 min; the reflux reaction temperature is 80-120℃, and the reflux reaction time is 2-4 h; the vacuum drying temperature is 60-80℃, and the drying time is 12-24 h.

[0012] Step 3 specifically involves: Weigh the following materials according to the weight fraction of the raw material components: 100 parts of EPDM rubber; 5-20 parts of KH570 modified SiZrBC ceramic precursor; 10-20 parts of aramid fiber; 10-20 parts of boron phenolic resin; 1-6 parts of zinc oxide; 1-2 parts of stearic acid; 1-2 parts of DCP. Adjust the roller spacing and perform thin-pass mixing of the raw materials in a two-roll mill to obtain the initial film. Let it stand for 8-10 hours to obtain the final film. The mixing time is 20-30 minutes. The roller spacing of the two-roll mill for thin-pass mixing should not be greater than 1 mm, and the number of thin-pass mixing cycles should be 5-10 times.

[0013] In step 4, the vulcanization temperature during the plate vulcanization process is 150-170℃, the vulcanization pressure is 3-5 MPa, and the vulcanization time is 30-60 min.

[0014] Another technical solution adopted in this invention is the KH570 modified ceramic-modified EPDM composite material prepared by the preparation method of KH570 modified ceramic-modified EPDM composite material.

[0015] The beneficial effects of this invention are: (1) The method of the present invention utilizes the silane coupling agent KH570 to modify the surface of the SiZrBC ceramic precursor. The alkoxy group at one end of KH570 can chemically react with the hydroxyl groups on the surface of the SiZrBC precursor, while the organic functional group (such as methacryloyloxy) at the other end has excellent compatibility with the EPDM matrix. This "molecular bridge" effect effectively reduces the surface energy of the ceramic precursor, prevents the aggregation of its nanoparticles, and enables it to achieve uniform dispersion at the nanoscale or even molecular level in the EPDM matrix.

[0016] (2) The method of the present invention transforms the originally physically blended system into a structure with chemical crosslinking points through the chemical bonding of KH570. This strong interfacial interaction enables stress to be effectively transferred between the EPDM matrix and the SiZrBC rigid particles. The SiZrBC precursor provides rigid support as a reinforcing phase, while the good interfacial bonding ensures that the matrix can effectively transfer the load to the reinforcing phase when subjected to external forces, thereby achieving a reinforcement effect while maintaining the good elasticity of EPDM.

[0017] (3) In the method of the present invention, the uniformly dispersed SiZrBC precursor can undergo in-situ ceramic transformation during the decomposition of EPDM under high-temperature ablation. After KH570 modification, an active interface layer is formed around the precursor, which promotes the formation and sintering of high-temperature ceramic phases such as SiC, ZrC, and ZrB2. In addition, due to the uniform dispersion of the precursor and its tight bonding with the matrix, the ceramic layer formed at high temperature is more dense, continuous, and crack-free, which can effectively block the erosion of oxygen and heat flow, and significantly improve the ablation resistance and high-temperature stability of the material. The KH570-modified SiZrBC precursor can also be used as a highly efficient char-forming agent, which can significantly improve the char rate of EPDM composite material at high temperature. A high char rate means that less combustible gas is released during combustion, and more substances are converted into a heat-insulating and oxygen-barrier carbon layer. The silicon and zirconium elements introduced by the SiZrBC precursor have extremely high thermal stability, and their ceramicization process can absorb heat, significantly delaying the thermal decomposition temperature of the composite material and improving the service life of the material under extreme thermal environments. Attached Figure Description

[0018] Figure 1 This is the Fourier transform infrared spectrum of the KH570-modified SiZrBC precursor prepared in the embodiments of the present invention; Figure 2This is the XRD diffraction pattern of the KH570-modified SiZrBC precursor prepared in the embodiment of the present invention after pyrolysis at 1600℃. Figure 3a This is a SEM image of the KH570-modified SiZrBC precursor prepared in this embodiment of the invention after pyrolysis at 1600℃. Figure 3b This is an EDS surface scan of the Zr element distribution of the KH570-modified SiZrBC precursor prepared in this embodiment of the invention after pyrolysis at 1600℃. Figure 3c This is an EDS surface scan of the Si element distribution of the KH570 modified SiZrBC precursor prepared in this embodiment of the invention after pyrolysis at 1600℃. Figure 3d This is an EDS surface scan B element distribution diagram of the KH570 modified SiZrBC precursor prepared in the embodiment of the present invention after pyrolysis at 1600℃. Figure 3e This is an EDS surface scan C element distribution diagram of the KH570 modified SiZrBC precursor prepared in the embodiment of the present invention after pyrolysis at 1600℃. Figure 3f The percentage of each element in the EDS surface scan of the KH570-modified SiZrBC precursor prepared in the embodiments of the present invention after pyrolysis at 1600℃. Figure 4 This is a tensile curve of the KH570-modified SiZrBC precursor-modified EPDM composite material prepared in the embodiments of the present invention. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0020] The preparation method of the KH570-modified ceramic-modified EPDM composite material of the present invention is carried out according to the following steps: Step 1, preparing the SiZrBC ceramic precursor; specifically: In an oxygen-free and anhydrous environment, zirconium tetrachloride was used as the zirconium source and mixed with ethanol for an organic reaction. Acetylacetone was added as a chelating agent for a chelation reaction. Boric acid, 1,4-butanediol, hydroquinone, and tetraethyl orthosilicate were added in sequence. After reflux reaction, the solvent was removed by vacuum distillation. After cooling to room temperature, it was transferred to a vacuum drying oven for drying to obtain the SiZrBC ceramic precursor.

[0021] The molar ratio of zirconium tetrachloride, ethanol, acetylacetone, boric acid, 1,4-butanediol, hydroquinone, and tetraethyl orthosilicate is 1:20:4:3:2:1:1; argon gas is introduced to ensure an oxygen-free environment.

[0022] The organication reaction temperature is 20-30℃, and the reaction time is 30-60 min. The chelation reaction temperature is 50-80℃, and the reaction time is 30-60 min; The reflux reaction temperature is 80-120℃, and the reaction time is 2-4 h; The vacuum drying temperature is 60-80℃, and the drying time is 12-24 h.

[0023] Step 2, prepare KH570 modified SiZrBC ceramic precursor; specifically: The SiZrBC ceramic precursor obtained in step 1 was dissolved and stirred in an ethanol solution, and then KH570 hydrolysis solution was added dropwise. After reflux reaction, the solvent was removed by vacuum distillation. After cooling to room temperature, it was transferred to a vacuum drying oven for drying to obtain KH570 modified SiZrBC ceramic precursor.

[0024] The preparation process of KH570 hydrolysis solution is as follows: KH570 is dissolved in a mixture of water and anhydrous ethanol for hydrolysis; the hydrolysis temperature is 40-60℃ and the hydrolysis time is 1-2 h. The mass ratio of SiZrBC ceramic precursor, KH570 and ethanol is 1:0.05-0.15:4, and the mass ratio of water to ethanol in the hydrolysis solution is 1:4.

[0025] The dissolution temperature is 30-60℃, and the dissolution time is 10-30 min; The reflux reaction temperature is 80-120℃, and the reflux reaction time is 2-4 h; The vacuum drying temperature is 60-80℃, and the drying time is 12-24 h.

[0026] Step 3, mixing of KH570-modified SiZrBC ceramic precursor with modified EPDM composite material; specifically: Weigh the following materials according to the weight fraction of the raw material components: 100 parts of EPDM rubber; 5-20 parts of KH570 modified SiZrBC ceramic precursor; 10-20 parts of aramid fiber; 10-20 parts of boron phenolic resin; 1-6 parts of zinc oxide; 1-2 parts of stearic acid; and 1-2 parts of DCP. Mix the raw materials in an open mill according to the proportions, and then adjust the roller spacing for thin-pass mixing to obtain the initial film. Let it stand for 8-10 hours to cool the film temperature.

[0027] The mixing time is 20-30 min, the roller spacing of the open mill thin pass is no more than 1 mm, and the number of thin passes is 5-10.

[0028] Step 4, vulcanization molding of the KH570-modified SiZrBC precursor-modified EPDM composite material; specifically: The mold is placed on a flat vulcanizing machine for preheating and a release agent is sprayed. The film in step 3 is cut according to the size requirements and filled into the mold for flat vulcanization. After demolding and cooling, the KH570 modified SiZrBC precursor modified EPDM composite material is obtained. During the plate vulcanization process, the vulcanization temperature is 150-170℃, the vulcanization pressure is 3-5 MPa, and the vulcanization time is 30-60 min.

[0029] Example 1 The preparation method of the KH570 modified SiZrBC precursor modified EPDM composite material of the present invention is carried out according to the following steps: Step 1: In an oxygen-free and anhydrous environment, 0.05 mol zirconium tetrachloride was used as the zirconium source and dissolved with 1 mol ethanol in a three-necked flask at 20°C and stirred for 30 min to carry out organication. 0.2 mol acetylacetone was added as a chelating agent to carry out the chelation reaction. Then, 0.15 mol boric acid, 0.1 mol 1,4-butanediol, 0.05 mol hydroquinone, and 0.05 mol tetraethyl orthosilicate were added sequentially. After reflux at 80°C for 2 h, the solvent was removed by vacuum distillation. After cooling to room temperature, it was transferred to a vacuum drying oven at 60°C and dried for 24 h to obtain the SiZrBC precursor.

[0030] Step 2: Dissolve the SiZrBC precursor from Step 1 in an ethanol solution at 60°C and stir for 30 min. Then, dissolve KH570 (5% by mass of SiZrBC precursor) in a mixed solution of water and anhydrous ethanol and hydrolyze it at 60°C for 1 h. Subsequently, add the KH570 hydrolysate dropwise and reflux at 80°C for 4 h. Remove the solvent by vacuum distillation and let it cool to room temperature. Then, transfer it to a vacuum drying oven and dry it at 60°C for 24 h to obtain the SiZrBC precursor.

[0031] Step 3: According to the weight fraction of raw material components: 100 parts of EPDM rubber; 5 parts of KH570 modified precursor powder; 10 parts of aramid fiber; 10 parts of boron phenolic resin; 1 part of zinc oxide; 1 part of stearic acid; 1 part of DCP. Mix the raw materials in an open mill according to the proportion, and then adjust the roller spacing to perform thin-pass mixing to obtain the initial rubber sheet. Let it stand for 8 hours to cool the rubber sheet temperature and release the stress generated by the rubber sheet.

[0032] Step 4: Place the mold on a flat vulcanizing machine, preheat it to 160°C and spray a release agent. Cut the film from Step 3 according to the size requirements and fill it into the mold. Perform flat vulcanization at 160°C and 3 MPa. Remove from the mold and cool to obtain the KH570 modified SiZrBC precursor modified EPDM composite material.

[0033] like Figure 1The figure shows the Fourier transform infrared (FTIR) spectra of KH570, the SiZrBC precursor, and the KH570-modified SiZrBC precursor. It can be seen that the KH570-modified SiZrBC precursor exhibits stretching vibration peaks of Si-O-Zr, Si-O-Si, and BO-Zr bonds. Furthermore, a stretching vibration peak of the C=C bond in KH570 is also observed, indicating that the KH570-modified SiZrBC precursor has been successfully prepared.

[0034] like Figure 2 The image shows the XRD diffraction pattern of the precursor after sintering at 1600℃. It can be seen that the ceramic products of the precursor are only ZrB2, ZrC and SiC, with no other impurities.

[0035] like Figures 3a-3f The image shows SEM and EDS images of the precursor after sintering at 1600℃. It can be seen that Zr, Si, B, and C elements are uniformly distributed in the ceramic. Furthermore, Si exists in the ceramic in the form of nanowires.

[0036] like Figure 4 As shown, the stress-strain curve of the EPDM composite material modified by SiZrBC precursor modified by KH570 is shown. It can be seen that the modified precursor effectively improves the mechanical properties of the EPDM composite material, with a tensile strength of 10.1 MPa and an elongation at break of 1053%.

[0037] Example 2 The preparation method of the KH570 modified SiZrBC precursor modified EPDM composite material of the present invention is carried out according to the following steps: Step 1: In an oxygen-free and anhydrous environment, 0.05 mol zirconium tetrachloride was used as the zirconium source and dissolved with 1 mol ethanol in a three-necked flask at 20°C and stirred for 30 min to carry out organication. 0.2 mol acetylacetone was added as a chelating agent to carry out the chelation reaction. Then, 0.15 mol boric acid, 0.1 mol 1,4-butanediol, 0.05 mol hydroquinone, and 0.05 mol tetraethyl orthosilicate were added sequentially. After reflux at 80°C for 2 h, the solvent was removed by vacuum distillation. After cooling to room temperature, it was transferred to a vacuum drying oven at 60°C and dried for 24 h to obtain the SiZrBC precursor.

[0038] Step 2: Dissolve the SiZrBC precursor from Step 1 in an ethanol solution at 60°C and stir for 30 min. Then, dissolve KH570 (10% by mass of SiZrBC precursor) in a mixed solution of water and anhydrous ethanol and hydrolyze it at 60°C for 1 h. Subsequently, gradually add the prepared KH570 hydrolysis solution dropwise. After refluxing at 80°C for 4 h, remove the solvent by vacuum distillation. After cooling to room temperature, transfer it to a vacuum drying oven and dry at 60°C for 24 h to obtain the SiZrBC precursor.

[0039] Step 3: According to the weight fraction of raw material components: 100 parts of EPDM rubber; 5 parts of KH570 modified precursor powder; 10 parts of aramid fiber; 10 parts of boron phenolic resin; 1 part of zinc oxide; 1 part of stearic acid; 1 part of DCP. Mix the raw materials in an open mill according to the proportion, and then adjust the roller spacing to perform thin-pass mixing to obtain the initial rubber sheet. Let it stand for 8 hours to cool the rubber sheet temperature and release the stress generated by the rubber sheet.

[0040] Step 4: Place the mold on a flat vulcanizing machine, preheat it to 160°C and spray a release agent. Cut the film from Step 3 according to the size requirements and fill it into the mold. Perform flat vulcanization at 160°C and 3 MPa. Remove from the mold and cool to obtain the KH570 modified SiZrBC precursor modified EPDM composite material.

[0041] Example 3 The preparation method of the KH570-modified SiZrBC precursor-modified EPDM composite material of the present invention is carried out according to the following steps: Step 1: In an oxygen-free and anhydrous environment, 0.05 mol zirconium tetrachloride was used as the zirconium source and dissolved with 1 mol ethanol in a three-necked flask at 20°C and stirred for 30 min to carry out organication. 0.2 mol acetylacetone was added as a chelating agent to carry out the chelation reaction. Then, 0.15 mol boric acid, 0.1 mol 1,4-butanediol, 0.05 mol hydroquinone, and 0.05 mol tetraethyl orthosilicate were added sequentially. After reflux at 80°C for 2 h, the solvent was removed by vacuum distillation. After cooling to room temperature, it was transferred to a vacuum drying oven at 60°C and dried for 24 h to obtain the SiZrBC precursor.

[0042] Step 2: Dissolve and stir the dried SiZrBC precursor from Step 1 in an ethanol solution at 60°C for 30 min. Then, hydrolyze KH570 (15% by mass of SiZrBC precursor) in a mixed solution of water and anhydrous ethanol at 60°C for 1 h. Subsequently, gradually add the prepared KH570 hydrolysis solution dropwise. After refluxing at 80°C for 4 h, remove the solvent by vacuum distillation. After cooling to room temperature, transfer to a vacuum drying oven and dry at 60°C for 24 h to obtain the SiZrBC precursor.

[0043] Step 3: According to the weight fraction of raw material components: 100 parts of EPDM rubber; 5 parts of KH570 modified precursor powder; 10 parts of aramid fiber; 10 parts of boron phenolic resin; 1 part of zinc oxide; 1 part of stearic acid; 1 part of DCP. Mix the raw materials in an open mill according to the proportion, and then adjust the roller spacing to perform thin-pass mixing to obtain the initial rubber sheet. Let it stand for 8 hours to cool the rubber sheet temperature and release the stress generated by the rubber sheet.

[0044] Step 4: Place the mold on a flat vulcanizing machine, preheat it to 160°C and spray a release agent. Cut the film from Step 3 according to the size requirements and fill it into the mold. Perform flat vulcanization at 160°C and 3 MPa. Remove from the mold and cool to obtain the KH570 modified SiZrBC precursor modified EPDM composite material.

[0045] Example 4 The preparation method of the KH570-modified SiZrBC precursor-modified EPDM composite material of the present invention is carried out according to the following steps: Step 1: In an oxygen-free and anhydrous environment, 0.05 mol zirconium tetrachloride was used as the zirconium source and dissolved with 1 mol ethanol in a three-necked flask at 20°C and stirred for 30 min to carry out organication. 0.2 mol acetylacetone was added as a chelating agent to carry out the chelation reaction. Then, 0.15 mol boric acid, 0.1 mol 1,4-butanediol, 0.05 mol hydroquinone, and 0.05 mol tetraethyl orthosilicate were added sequentially. After reflux at 80°C for 2 h, the solvent was removed by vacuum distillation. After cooling to room temperature, it was transferred to a vacuum drying oven at 60°C and dried for 24 h to obtain the SiZrBC precursor.

[0046] Step 2: Dissolve the SiZrBC precursor from Step 1 in an ethanol solution at 60°C and stir for 30 min. Then, dissolve KH570 (10% by mass of SiZrBC precursor) in a mixed solution of water and anhydrous ethanol and hydrolyze it at 60°C for 1 h. Subsequently, gradually add the prepared KH570 hydrolysis solution dropwise. After refluxing at 80°C for 4 h, remove the solvent by vacuum distillation. After cooling to room temperature, transfer it to a vacuum drying oven and dry at 60°C for 24 h to obtain the SiZrBC precursor.

[0047] Step 3: According to the weight fraction of raw material components: 100 parts of EPDM rubber; 10 parts of KH570 modified precursor powder; 10 parts of aramid fiber; 10 parts of boron phenolic resin; 1 part of zinc oxide; 1 part of stearic acid; 1 part of DCP. Mix the raw materials in an open mill according to the proportion, and then adjust the roller spacing to perform thin-pass mixing to obtain the initial rubber sheet. Let it stand for 8 hours to cool the rubber sheet temperature and release the stress generated by the rubber sheet.

[0048] Step 4: Place the mold on a flat vulcanizing machine, preheat it to 160°C and spray a release agent. Cut the film from Step 3 according to the size requirements and fill it into the mold. Perform flat vulcanization at 160°C and 3 MPa. Remove from the mold and cool to obtain the KH570 modified SiZrBC precursor modified EPDM composite material.

[0049] Example 5 The preparation method of the KH570-modified SiZrBC precursor-modified EPDM composite material of the present invention is carried out according to the following steps: Step 1: In an oxygen-free and anhydrous environment, 0.05 mol zirconium tetrachloride was used as the zirconium source and dissolved with 1 mol ethanol in a three-necked flask at 20°C and stirred for 30 min to carry out organication. 0.2 mol acetylacetone was added as a chelating agent to carry out the chelation reaction. Then, 0.15 mol boric acid, 0.1 mol 1,4-butanediol, 0.05 mol hydroquinone, and 0.05 mol tetraethyl orthosilicate were added sequentially. After reflux at 80°C for 2 h, the solvent was removed by vacuum distillation. After cooling to room temperature, it was transferred to a vacuum drying oven at 60°C and dried for 24 h to obtain the SiZrBC precursor.

[0050] Step 2: Dissolve the SiZrBC precursor from Step 1 in an ethanol solution at 60°C and stir for 30 min. Then, dissolve KH570 (10% by mass of SiZrBC precursor) in a mixed solution of water and anhydrous ethanol and hydrolyze it at 60°C for 1 h. Subsequently, gradually add the prepared KH570 hydrolysis solution dropwise. After refluxing at 80°C for 4 h, remove the solvent by vacuum distillation. After cooling to room temperature, transfer it to a vacuum drying oven and dry at 60°C for 24 h to obtain the SiZrBC precursor.

[0051] Step 3: According to the weight fraction of raw material components: 100 parts of EPDM rubber; 15 parts of KH570 modified precursor powder; 10 parts of aramid fiber; 10 parts of boron phenolic resin; 1 part of zinc oxide; 1 part of stearic acid; 1 part of DCP. Mix the raw materials in an open mill according to the proportion, and then adjust the roller spacing to perform thin-pass mixing to obtain the initial rubber sheet. Let it stand for 8 hours to cool the rubber sheet temperature and release the stress generated by the rubber sheet.

[0052] Step 4: Place the mold on a flat vulcanizing machine, preheat it to 160°C and spray a release agent. Cut the film from Step 3 according to the size requirements and fill it into the mold. Perform flat vulcanization at 160°C and 3 MPa. Remove from the mold and cool to obtain the KH570 modified SiZrBC precursor modified EPDM composite material.

[0053] Comparative Example 1 The preparation method of SiZrBC precursor modified EPDM composite material is as follows: Step 1: In an oxygen-free and anhydrous environment, 0.05 mol zirconium tetrachloride was used as the zirconium source and dissolved with 1 mol ethanol in a three-necked flask at 20°C and stirred for 30 min to carry out organication. 0.2 mol acetylacetone was added as a chelating agent to carry out the chelation reaction. Then, 0.15 mol boric acid, 0.1 mol 1,4-butanediol, 0.05 mol hydroquinone, and 0.05 mol tetraethyl orthosilicate were added sequentially. After reflux at 80°C for 2 h, the solvent was removed by vacuum distillation. After cooling to room temperature, it was transferred to a vacuum drying oven at 60°C and dried for 24 h to obtain the SiZrBC precursor.

[0054] Step 2, according to the weight fraction of raw material components: 100 parts of EPDM rubber; 5 parts of SiZrBC precursor; 10 parts of aramid fiber; 10 parts of boron phenolic resin; 1 part of zinc oxide; 1 part of stearic acid; 1 part of DCP. Mix the raw materials in an open mill according to the proportion, and then adjust the roller spacing to perform thin-pass mixing to obtain the initial rubber sheet. Let it stand for 8 hours to cool the rubber sheet temperature and release the stress generated by the rubber sheet.

[0055] Step 3: Place the mold on a flat vulcanizing machine, preheat it to 160°C and spray a release agent. Cut the film from Step 2 according to the size requirements and fill it into the mold. Perform flat vulcanization at 160°C and 3 MPa. Remove from the mold and cool to obtain SiZrBC precursor modified EPDM composite material.

[0056] Comparative Example 2 The preparation method of EPDM composite material is as follows: Step 1: According to the weight fraction of raw material components: 100 parts of EPDM rubber; 10 parts of aramid fiber; 10 parts of boron phenolic resin; 1 part of zinc oxide; 1 part of stearic acid; 1 part of DCP. Mix the raw materials in an open mill according to the ratio, and then adjust the roller spacing to perform thin-pass mixing to obtain the initial rubber sheet. Let it stand for 8 hours to cool the temperature of the rubber sheet and release the stress generated by the rubber sheet.

[0057] Step 2: Place the mold on a flat vulcanizing machine, preheat it to 160°C and spray a release agent. Cut the film from Step 1 according to the size requirements and fill it into the mold. Perform flat vulcanization at 160°C and 3 MPa. Remove from the mold and cool to obtain EPDM composite material.

[0058] Example 6 Table 1 shows a comparison of the properties of the EPDM composite materials prepared in Comparative Examples 1-2 and Examples 1-5. Table 1. Properties of EPDM composite materials prepared in Comparative Examples 1-2 and Examples 1-5

[0059] Based on the experimental data analysis in Table 1, Examples 1-3 analyzed the performance effects of different mass ratios of KH570-modified SiZrBC precursor-modified EPDM composites. The results showed that as the KH570 content gradually increased, the mechanical properties and ablation performance first increased and then decreased. Appropriate addition of KH570 effectively improved the interfacial compatibility between EPDM and SiZrBC. However, excessive addition of KH570 molecules could lead to self-polymerization, thus disrupting the matrix continuity. Examples 4 and 5 compared the performance effects of different amounts of KH570-modified SiZrBC precursor-modified EPDM composites. The results showed that as the amount of KH570 increased, the performance of EPDM decreased. Because KH570 contains double bonds, excessive filler would excessively consume peroxide free radicals, leading to a decrease in crosslinking density and thus affecting its performance.

[0060] In Comparative Example 2, due to the absence of precursor particles, the EPDM composite material failed to form a dense, high-strength ceramic protective layer during high-temperature ablation. The carbon layer formed solely by aramid fibers and phenolic resin was loose and low-strength, easily eroded by high-speed airflow, leading to reduced ablation performance. Furthermore, the lack of effective interfacial coupling between aramid fibers and EPDM reduced stress transfer efficiency, consequently resulting in decreased mechanical properties.

[0061] For Comparative Example 1, the unmodified SiZrBC precursor has a high surface polarity, poor compatibility with the EPDM matrix, and is prone to agglomeration, forming stress concentration points and thus leading to a decrease in mechanical properties. Furthermore, during the ablation process, the agglomeration of the precursor results in uneven distribution of the in-situ generated ceramic phase, which cannot effectively block oxygen and heat flow, leading to a higher linear ablation rate than in the example.

[0062] In summary, for KH570-modified SiZrBC precursor-modified EPDM composites, the modified EPDM composites exhibit the best performance when the mass ratio of KH570 is 10% and the precursor content is 5 parts.

Claims

1. A method for preparing KH570-modified ceramic-modified EPDM composite materials, characterized in that, The specific steps are as follows: Step 1: Prepare SiZrBC ceramic precursor; Step 2: Prepare KH570 modified SiZrBC ceramic precursor; Step 3: EPDM rubber, KH570 modified SiZrBC ceramic precursor, aramid fiber, boron phenolic resin, zinc oxide, stearic acid and DCP are mixed in a thin-pass mixture to obtain a film. Step 4: Place the mold on a flat vulcanizing machine for preheating and spray with a release agent. Fill the mold with the film and perform flat vulcanization. Remove from the mold and cool to obtain KH570 modified ceramic EPDM composite material.

2. The method for preparing the KH570-modified ceramic-modified EPDM composite material as described in claim 1, characterized in that, In step 1, specifically: In an argon atmosphere, zirconium tetrachloride was mixed with ethanol for an organic reaction, acetylacetone was added for a chelation reaction, and then boric acid, 1,4-butanediol, hydroquinone, and tetraethyl orthosilicate were added in sequence. After reflux reaction, the mixture was distilled under reduced pressure, cooled, and dried under vacuum to obtain the SiZrBC ceramic precursor.

3. The method for preparing the KH570-modified ceramic-modified EPDM composite material as described in claim 2, characterized in that, The molar ratio of zirconium tetrachloride, ethanol, acetylacetone, boric acid, 1,4-butanediol, hydroquinone, and tetraethyl orthosilicate is 1:20:4:3:2:1:

1.

4. The method for preparing the KH570-modified ceramic-modified EPDM composite material as described in claim 2, characterized in that, The organication reaction temperature is 20-30℃, and the reaction time is 30-60 min; the chelation reaction temperature is 50-80℃, and the reaction time is 30-60 min; the reflux reaction temperature is 80-120℃, and the reaction time is 2-4 h; the vacuum drying temperature is 60-80℃, and the drying time is 12-24 h.

5. The method for preparing the KH570-modified ceramic-modified EPDM composite material as described in claim 1, characterized in that, Step 2 specifically involves: The SiZrBC ceramic precursor obtained in step 1 was dissolved and stirred in an ethanol solution, and then KH570 hydrolysis solution was added dropwise. After reflux reaction, the mixture was distilled under reduced pressure, cooled, and dried under vacuum to obtain the KH570 modified SiZrBC ceramic precursor.

6. The method for preparing the KH570-modified ceramic-modified EPDM composite material as described in claim 5, characterized in that, The preparation process of KH570 hydrolysis solution is as follows: KH570 is dissolved in a mixture of water and anhydrous ethanol for hydrolysis at a temperature of 40-60℃ for 1-2 hours.

7. The method for preparing the KH570-modified ceramic-modified EPDM composite material as described in claim 5, characterized in that, The dissolution temperature is 30-60℃, and the dissolution time is 10-30 min; the reflux reaction temperature is 80-120℃, and the reflux reaction time is 2-4 h; the vacuum drying temperature is 60-80℃, and the drying time is 12-24 h.

8. The method for preparing the KH570-modified ceramic-modified EPDM composite material as described in claim 1, characterized in that, Step 3 specifically involves: Weigh the following materials according to the weight fraction of the raw material components: 100 parts of EPDM rubber; 5-20 parts of KH570 modified SiZrBC ceramic precursor; 10-20 parts of aramid fiber. 10-20 parts boron phenolic resin; 1-6 parts zinc oxide; Stearic acid 1-2 parts; DCP 1-2 parts; adjust the roller spacing and mix the raw materials in a two-roll mill to obtain the initial film; let it stand for 8-10 hours to obtain the final film. The mixing time is 20-30 min, the roller spacing of the open mill thin pass is no more than 1 mm, and the number of thin passes is 5-10.

9. The method for preparing the KH570-modified ceramic-modified EPDM composite material as described in claim 1, characterized in that, In step 4, the vulcanization temperature during the plate vulcanization process is 150-170℃, the vulcanization pressure is 3-5 MPa, and the vulcanization time is 30-60 min.

10. The KH570-modified ceramic-modified EPDM composite material prepared by the method for preparing KH570-modified ceramic-modified EPDM composite material according to any one of claims 1-9.

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