ZrC / ZrB2 precursor modified ethylene propylene diene monomer composite material and preparation method thereof

Abstract

The invention discloses a preparation method of a ZrC / ZrB2 precursor modified ethylene propylene diene monomer composite material. The preparation method is specifically implemented according to the following steps: step 1, preparing a ZrC / ZrB2 precursor; 2, grinding and sieving the ZrC / ZrB2 solid in the step 1 to obtain micron-sized precursor powder, and then putting the micron-sized precursor powder into a graphite box to be pretreated in a cross-linking box; step 3, mixing the ZrC / ZrB2 precursor modified ethylene propylene diene monomer composite material; and step 4, carrying out vulcanization molding on the ZrC / ZrB2 precursor modified ethylene propylene diene monomer composite material. The invention also discloses the composite material prepared by the method. According to the invention, the ethylene propylene diene monomer is modified by the ZrC / ZrB2 precursor in a polymer form, so that the problem of interface mismatching of inorganic ceramic filler is avoided, and the filler is mixed more uniformly.

Description

Technical Field

[0001] The present invention belongs to the technical field of novel composite materials, and particularly relates to a ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer (EPDM) composite material, and the present invention also relates to a preparation method of the composite material. Background Art

[0002] A solid rocket engine is an important part of an aerospace vehicle. Its combustion chamber mainly consists of a shell, an insulation layer, a liner, and a grain. The insulation layer is located between the inner surface of the engine shell and the liner. The components of the insulation layer material generally include a polymer matrix material, fibers, ablation-resistant fillers, and flame retardants. Some formulations also require other components such as tackifiers, bonding agents, and processing aids. The selection of the insulation layer matrix material has a significant impact on the performance of the insulation layer. Generally, an elastic material with a low thermal conductivity, low density, low elastic modulus, and high elongation is used as the matrix material for the insulation layer, and good compatibility with the shell material and the propellant is required to ensure firm bonding between the insulation layer and the shell and the grain interfaces. Ethylene propylene diene monomer (EPDM) is an ideal matrix material for internal insulation materials. It is a terpolymer made of ethylene, propylene, and a small amount of conjugated diene. Its main chain is a saturated hydrocarbon structure, the double bond is in the side chain, there is no polar substituent in the molecule, the chain segment is relatively flexible, and it has the advantages of good heat resistance, low ablation rate, high elongation, low glass transition temperature, etc., and low density and large specific heat capacity.

[0003] Ethylene propylene diene monomer (EPDM) is an ideal matrix material for the internal insulation layer of solid rockets, but there are also certain defects. Its mechanical properties and flame retardant and heat insulation properties cannot serve for a long time in an environment of temperature rise and strong heat flux erosion, and it cannot be directly applied to the internal insulation layer of aerospace vehicles. Some high-performance fillers need to be added for modification. In addition, traditional ethylene propylene diene monomer composite materials mostly use ethylene propylene diene monomer with a C-C main chain as the matrix and are prepared by compounding high-temperature-resistant fillers such as carbon black and silica. When the material serves at high temperature, the rubber matrix will pyrolyze to form a carbonized layer, which has good heat insulation performance. However, under the erosion of hot flow gas and high-speed particles for a long time, the material will crack and oxidize to produce a large amount of 2 gases such as CO volatilize, resulting in phenomena such as large ablation, warping deformation, etc., and the mechanical properties rapidly decline, and the thermal protection effect is greatly weakened.

[0004] Currently, the main methods for improving the ablation resistance of ethylene propylene diene monomer (EPDM) rubber are as follows. One is to add non-metallic minerals such as mica, clay, kaolin, and montmorillonite to EPDM rubber, which can not only provide excellent high-temperature resistance but also endow the material with the ability to undergo in-situ ceramization transformation, jointly constituting a ceramic skeleton with the matrix pyrolysis products to provide sufficient strength. For example, the Chinese invention patent application number is CN202410522477.X and the publication number is CN118240306A. Also, by adding some ceramic fibers such as silicate fibers and glass fibers as reactive fillers to participate in the in-situ ceramization reaction, the density and strength of the ceramic body are further improved. For example, the Chinese invention patent application number is CN201710233776.1 and the publication number is CN106977823A. The addition of ceramic fillers and reinforcing fibers can effectively improve the high-temperature resistance and mechanical properties of EPDM rubber, but there will be an interface mismatch problem between the rubber (polymer) and the filler (ceramic). In addition, the distribution of the filler in the matrix needs to be considered, and its uneven distribution will lead to cracking of the ceramic product or peeling of the ceramic layer, greatly affecting the final structure and mechanical properties of the rubber. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method of ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material, which solves the problem of interface mismatch between rubber and filler in the prior art.

[0006] Another object of the present invention is to provide a composite material prepared by the preparation method of ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material.

[0007] The first technical solution adopted by the present invention is that the preparation method of ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material is specifically implemented according to the following steps: Step 1, prepare ZrC / ZrB 2 precursor; Step 2, grind and sieve the ZrC / ZrB 2 precursor obtained in Step 1 to obtain micron-sized precursor powder, and then place it in a graphite box for pretreatment in a crosslinking box; Step 3, mixing of ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material; Step 4, vulcanization molding of ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material.

[0008] The feature of the first technical solution of the present invention is further that, Step 1 specifically includes: in an oxygen-free and water-free environment, using zirconium tetrachloride as the zirconium source, dissolving and stirring it with ethanol in a three-necked flask for organic modification, adding acetylacetone as a chelating agent for chelation reaction; then adding a boron source, after reflux reaction, removing the solvent by vacuum distillation, and transferring it to a vacuum drying oven for drying after cooling to room temperature to obtain the ZrC / ZrB 2 precursor.

[0009] In step 1, the molar ratio of zirconium tetrachloride: ethanol: acetylacetone: boron source is 1:20:4:3. The boron source is one or a mixture of boron phenol formaldehyde, boric acid, and phenylboronic acid. Argon is introduced into the three-necked flask to ensure an oxygen-free environment.

[0010] In step 1, the temperature for organic modification is 20°C - 30°C, and the time is 30 min - 60 min; the temperature for chelation reaction is 50°C - 60°C, and the time is 60 min - 90 min; the temperature for reflux reaction is 100°C - 140°C, and the reaction time is 2 h; the temperature for the vacuum drying process is 60°C - 70 °C, and the drying time is 8 h - 12 h.

[0011] In step 2, the sieving parameter is 300 mesh, the pretreatment temperature of the precursor powder is 150°C - 170 °C, and the pretreatment time is 1 h - 3 h.

[0012] Step 3 specifically includes: by weight fraction of raw material components: 100 parts of ethylene propylene diene monomer rubber; 5 parts - 20 parts of the pretreated ZrC / ZrB 2 precursor powder; 10 parts - 20 parts of aramid fiber; 10 parts - 20 parts of boron phenol formaldehyde; 1 part - 6 parts of zinc oxide; 1 part - 2 parts of stearic acid; 1 part - 2 parts of DCP. Mix the raw materials of each group on an open mill according to the ratio, and then adjust the roller gap for thin-pass mixing to obtain an initial film, place it for 8 h - 10 h, and cool the film temperature.

[0013] In step 3, the mixing time is 20 min - 30 min, the roller gap for thin-pass on the open mill is not more than 1 mm, and the number of thin-pass times is 8 times - 10 times.

[0014] Step 4 specifically includes: placing the mold on a flat vulcanizer for preheating and spraying a release agent, cutting the film in step 3 according to the size requirements and filling it into the mold for flat vulcanization, and demolding and cooling to obtain.

[0015] In step 4, during the flat vulcanization process, the vulcanization temperature is 150°C - 170°C, the vulcanization pressure is 3 MPa - 5 MPa, and the vulcanization time is 30 min - 60 min.

[0016] The second technical solution adopted by the present invention is that the ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer rubber composite material prepared by the preparation method of2 Precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material.

[0017] The beneficial effects of the present invention are as follows: (1) During the combustion or pyrolysis process of the ZrC / ZrB 2 precursor-modified EPDM rubber composite material prepared by the present invention, the residue after the matrix material is pyrolyzed and the added ceramizable filler undergo a sintering reaction to form a ceramic layer, which maintains the original shape of the material and has a certain strength, thereby changing the heat and oxygen transfer processes, protecting the internal material and achieving the effect of antioxidant ablation.

[0018] (2) Both the ZrC / ZrB 2 precursor and the EPDM rubber are in the polymer form, and they can be better fused and dispersed during the rolling and mixing process. The combination of the two is stronger, and there is no problem of interfacial mismatch, avoiding the cracking and peeling problems of the subsequent ceramic products.

[0019] (3) The ZrC / ZrB 2 precursor will gradually transform into the ceramic phase at high temperature. The transformation process absorbs the released heat energy to extend the service time of the material, improving the high-temperature resistance and ablation resistance of the rubber. Moreover, the ultra-high temperature ceramic particles after ceramization have extremely high melting points, excellent mechanical properties and good thermal shock resistance, greatly improving the antioxidant ablation performance of the EPDM rubber. Description of the Drawings

[0020] Figure 1 is the preparation process diagram of the ZrC / ZrB 2 precursor-modified EPDM rubber composite material of the present invention; Figure 2 is the XRD diffraction pattern of the sintered product of the ZrC / ZrB 2 precursor at 1550 °C of the present invention; Figure 3 is the physical diagram of the ZrC / ZrB 2 precursor-modified EPDM rubber composite material of the present invention; Figure 4 is the SEM diagram of the ZrC / ZrB 2 precursor-modified EPDM rubber composite material of the present invention; Figure 5 is the tensile curve diagram of the ZrC / ZrB 2 precursor-modified EPDM rubber composite material of the present invention. Detailed Embodiments

[0021] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0022] The ZrC / ZrB of the present invention2 Preparation method of precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material, as Figure 1 shown, is specifically implemented according to the following steps: Step 1, prepare ZrC / ZrB 2 precursor; Step 1 is specifically as follows: In an oxygen-free and anhydrous environment, zirconium tetrachloride is used as the zirconium source, dissolved and stirred with ethanol in a three-necked flask for organicization, and acetylacetone is added as a chelating agent for chelation reaction; then a boron source is added, and after reflux reaction, the solvent is removed by vacuum distillation. After it is cooled to room temperature, it is transferred to a vacuum drying oven for drying to obtain ZrC / ZrB 2 precursor solid; In Step 1, the molar ratio of zirconium tetrachloride: ethanol: acetylacetone: boron source is 1:20:4:3. The boron source is one or a mixture of boron phenol formaldehyde, boric acid, and phenylboronic acid. Argon is continuously introduced into the three-necked flask to ensure an oxygen-free environment and avoid affecting the reactants; The temperature of organicization is 20°C - 30°C, and the time is 30 min - 60 min; the temperature of chelation reaction is 50°C - 60°C, and the time is 60 min - 90 min; the temperature of reflux reaction is 100°C - 140°C, and the reaction time is 2 h; the temperature of the vacuum drying process is 60°C - 70 °C, and the drying time is 8 h - 12 h; Step 2, grind and sieve the ZrC / ZrB 2 solid in Step 1 to obtain micron-sized precursor powder, and then place it in a graphite box for pretreatment in a crosslinking box; The sieve parameter is 300 mesh, the pretreatment temperature of the precursor powder is 150°C - 170 °C, and the pretreatment time is 1 h - 3 h; Step 3, mixing of ZrC / ZrB 2 precursor-modified EPDM rubber composite material; Step 3 is specifically as follows: By weight fraction of raw material components: 100 parts of EPDM rubber; 5 parts - 20 parts of pretreated ZrC / ZrB 2 precursor powder; 10 parts - 20 parts of aramid fiber; 10 parts - 20 parts of boron phenol formaldehyde; 1 part - 6 parts of zinc oxide; 1 part - 2 parts of stearic acid; 1 part - 2 parts of DCP. Mix the raw materials of each group according to the ratio in an open mill, and then adjust the roll gap for thin-pass mixing to obtain an initial film. Place it for 8 h - 10 h to cool the film temperature and release the stress generated during rubber mixing; The mixing time is 20 min - 30 min, the roll gap of thin-pass in the open mill is not more than 1 mm, and the number of thin-pass times is 8 times - 10 times; Step 4, vulcanization and molding of ZrC / ZrB 2 precursor-modified EPDM rubber composite material; Step 4 specifically includes: placing the mold on a flat vulcanizer for preheating and spraying a mold release agent, cutting the film in Step 3 according to the size requirements and filling it into the mold for flat vulcanization, and obtaining the product after demolding and cooling; During the flat vulcanization process, the vulcanization temperature is 150°C - 170°C, the preheating temperature is the same as the vulcanization temperature, the vulcanization pressure is 3 MPa - 5 MPa, and the vulcanization time is 30 min - 60 min.

[0023] Example 1 ZrC / ZrB 2 A preparation method of a precursor-modified ethylene propylene diene monomer composite material is specifically implemented according to the following steps: Step 1, in an oxygen-free and water-free environment, using 0.025 mol of zirconium tetrachloride as the zirconium source, dissolving and stirring with 0.5 mol of ethanol in a three-necked flask at 20°C for 60 min for organification, then adding 0.1 mol of acetylacetone as a chelating agent and reacting at 50°C for 60 min; then adding 0.075 mol of boron phenolic resin to provide a boron source, refluxing and reacting at 100°C for 2 h, removing the solvent by reduced pressure distillation, and transferring it to a vacuum drying oven at 60°C for drying for 8 h to obtain ZrC / ZrB 2 precursor solid; Step 2, grinding and sieving (300 mesh) the obtained ZrC / ZrB 2 precursor solid to obtain micron-sized ZrC / ZrB 2 precursor powder, placing it in a graphite box and performing pretreatment in a crosslinking box, with a pretreatment temperature of 150°C and a pretreatment time of 1 h; Step 3, the raw material composition is as follows by weight: 100 parts of ethylene propylene diene monomer; 5 parts of pretreated ZrC / ZrB 2 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; mixing each group of raw materials on an open mill for 20 min according to the ratio until evenly mixed, with a roll gap of 1 mm for thin passing and a thin passing times of 8 times to obtain an initial film, placing it for 8 h, cooling the film temperature, and releasing the stress generated during rubber mixing; Step 4, placing a mold with a size of Φ30 mm × 10 mm on a flat vulcanizer for preheating to 150°C and spraying a mold release agent, cutting the film according to the size requirements and filling it into the mold, and performing flat vulcanization at 150°C and 3 MPa for 60 min, and obtaining ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer composite material after demolding and cooling.

[0024] Example 2 ZrC / ZrB 2 A preparation method of a precursor-modified ethylene propylene diene monomer composite material is specifically implemented according to the following steps: Step 1, in an oxygen-free and water-free environment, using 0.025 mol of zirconium tetrachloride as the zirconium source, dissolve and stir it with 0.5 mol of ethanol in a three-necked flask at 20 °C for 60 min for organometallization. Then add 0.1 mol of acetylacetone as a chelating agent and react at 50 °C for 60 min; then add 0.075 mol of boric acid to provide the boron source, reflux and react at 100 °C for 2 h, remove the solvent by vacuum distillation, and transfer it to a vacuum drying oven after cooling to room temperature and dry at 60 °C for 8 h to obtain ZrC / ZrB 2 precursor solid; Step 2, grind and screen (300 mesh) the obtained ZrC / ZrB 2 precursor solid to obtain micron-scale ZrC / ZrB 2 precursor powder, place it in a graphite box and perform pretreatment in a crosslinking box, the pretreatment temperature is 150 °C, and the pretreatment time is 1 h; Place the pretreated ZrC / ZrB 2 precursor in a high-temperature tube furnace and sinter at 1550 °C in an argon atmosphere to obtain a sintered ceramic product, and its phase characterization is as Figure 2 shown. It can be seen that the sintered product of ZrC / ZrB 2 precursor at 1550 °C is ZrC and ZrB 2 two phases, and no other impurity phases are generated, indicating the successful preparation of ZrC / ZrB 2 precursor.

[0025] Step 3, the raw material composition is as follows by weight: 100 parts of ethylene propylene diene monomer rubber; and the treated ZrC / ZrB 2 precursor: 5 parts; aramid fiber: 10 parts; boron phenolic aldehyde: 10 parts; zinc oxide: 2 parts; stearic acid: 1 part; DCP: 1 part; mix each group of raw materials on an open mill for 20 min until evenly mixed, the roll gap for thin passing is 1 mm, and the number of thin passing times is 9 times to obtain an initial film, place it for 8 h, cool the film temperature, and release the stress generated during rubber mixing; Step 4, place a mold with dimensions of Φ 30 mm×10 mm on a flat vulcanizer and preheat it to 150 °C and spray a release agent, cut the film according to the size requirements and fill it into the mold, and perform flat vulcanization at 150 °C and 3 MPa for 60 min, and take out the mold and cool it to obtain ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer rubber composite material, as Figure 4 shown.

[0026] Example 3 ZrC / ZrB 2 Preparation method of precursor-modified ethylene propylene diene monomer rubber composite material, which is specifically implemented according to the following steps: Step 1, in an oxygen-free and water-free environment, using 0.025 mol of zirconium tetrachloride as the zirconium source, dissolve and stir it with 0.5 mol of ethanol in a three-necked flask at 25 °C for 60 min for organification, then add 0.1 mol of acetylacetone as a chelating agent and react at 60 °C for 75 min; then add 0.0375 mol of boron phenolic resin and 0.0375 mol of boric acid to provide the boron source, reflux and react at 120 °C for 2 h, remove the solvent by reduced pressure distillation, and transfer it to a vacuum drying oven at 65 °C for drying for 10 h to obtain ZrC / ZrB 2 precursor solid; Step 2, grind and screen the obtained ZrC / ZrB 2 precursor solid (300 mesh) to obtain micron-sized ZrC / ZrB 2 precursor powder, place it in a graphite box and perform pretreatment in a crosslinking box, the pretreatment temperature is 160 °C, and the pretreatment time is 2 h; Step 3, the raw material composition is by weight: 100 parts of ethylene propylene diene monomer rubber; pretreated ZrC / ZrB 2 precursor: 5 parts; aramid fiber: 15 parts; boron phenolic resin: 15 parts; zinc oxide: 3 parts; stearic acid: 1.5 parts; DCP: 1.5 parts; mix each group of raw materials on an open mill for 25 min until evenly mixed, the roller gap for thin-sheeting is 0.5 mm, and the number of thin-sheeting times is 10 times to obtain an initial film, place it for 9 h, cool the film temperature, and release the stress generated during rubber mixing; Step 4, place a mold with dimensions of Φ 30 mm×10 mm on a flat vulcanizer and preheat it to 160 °C and spray a mold release agent, cut the film according to the size requirements and fill it into the mold, vulcanize it on the flat vulcanizer at 160 °C and 4 MPa for 45 min, take out the mold and cool it to obtain ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer rubber composite material.

[0027] Example 4 ZrC / ZrB 2 Preparation method of ZrC / ZrB precursor-modified ethylene propylene diene monomer rubber composite material, which is specifically implemented according to the following steps: 2 precursor solid; Step 2, the obtained ZrC / ZrB2 The precursor solid is ground and sieved (300 mesh) to obtain micron-sized ZrC / ZrB 2 precursor powder, which is placed in a graphite box and pretreated in a crosslinking box at a pretreatment temperature of 160 °C for 2 h; Step 3: The raw material composition is as follows by weight: 100 parts of ethylene propylene diene monomer rubber; pretreated ZrC / ZrB 2 precursor powder 10 parts; aramid fiber 15 parts; boron phenolic aldehyde 15 parts; zinc oxide 4 parts; stearic acid 1.5 parts; DCP 1.5 parts; The raw materials of each group are mixed on an open mill for 25 min until evenly mixed. The roller spacing for thin passing is 0.5 mm, and the number of thin passing times is 9 times to obtain an initial film, which is placed for 9 h to cool the film temperature and release the stress generated during rubber mixing; Step 4: Place a mold with dimensions of Φ 30 mm×10 mm on a flat vulcanizing machine and preheat it to 160 °C, then spray a release agent. Cut the film according to the size requirements and fill it into the mold, and vulcanize it flat at 160 °C and 4 MPa for 45 min, and then take out the mold and cool it to obtain ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer rubber composite.

[0028] Example 5 ZrC / ZrB 2 A preparation method of a ZrC / ZrB precursor-modified ethylene propylene diene monomer rubber composite is specifically implemented according to the following steps: Step 1: In an oxygen-free and water-free environment, 0.025 mol of zirconium tetrachloride is used as a zirconium source, and it is dissolved and stirred in a three-necked flask with 0.5 mol of ethanol at 30 °C for 60 min for organification, and then 0.1 mol of acetylacetone is added as a chelating agent and reacted at 70 °C for 90 min; then 0.0375 mol of phenylboronic acid and 0.0375 mol of boric acid are added to provide a boron source, and the reaction is refluxed at 140 °C for 2 h. The solvent is removed by reduced pressure distillation, and after it is cooled to room temperature, it is transferred to a vacuum drying oven and dried at 70 °C for 12 h to obtain ZrC / ZrB 2 precursor solid; Step 2: The obtained ZrC / ZrB 2 precursor solid is ground and sieved (300 mesh) to obtain micron-sized ZrC / ZrB 2 precursor powder, which is placed in a graphite box and pretreated in a crosslinking box at a pretreatment temperature of 170 °C for 3 h; Step 3: The raw material composition is as follows by weight: 100 parts of ethylene propylene diene monomer rubber; pretreated ZrC / ZrB 215 parts of precursor powder; 20 parts of aramid fiber; 20 parts of boron phenolic resin; 5 parts of zinc oxide; 2 parts of stearic acid; 2 parts of DCP; Mix the raw materials of each group on an open mill for 30 min until evenly mixed. The roller spacing for thin pass is 0.8 mm, and the number of thin passes is 9 times to obtain the initial film. Let it stand for 10 h, cool the film temperature, and release the stress generated during rubber mixing; Step 4, Place a mold with dimensions of Φ 30 mm×10 mm on a flat vulcanizer and preheat it to 170 °C, then spray a mold release agent. Cut the film according to the size requirements and fill it into the mold. Vulcanize it on the flat vulcanizer at 170 °C and 5 MPa for 30 min, and then take it out of the mold and cool it to obtain ZrC / ZrB 2 Precursor-modified ethylene propylene diene monomer composite material.

[0029] Example 6 ZrC / ZrB 2 A preparation method of a precursor-modified ethylene propylene diene monomer composite material, which is specifically implemented according to the following steps: Step 1, In an oxygen-free and water-free environment, use 0.025 mol of zirconium tetrachloride as the zirconium source, dissolve and stir it with 0.5 mol of ethanol in a three-necked flask at 30 °C for 60 min for organic modification, then add 0.1 mol of acetylacetone as a chelating agent and react at 70 °C for 90 min; Then add 0.025 mol of boron phenolic resin, 0.025 mol of boric acid, and 0.025 mol of phenylboronic acid to provide the boron source, reflux and react at 140 °C for 2 h, remove the solvent by vacuum distillation, and transfer it to a vacuum drying oven at 70 °C for drying for 12 h after it cools to room temperature to obtain ZrC / ZrB 2 Precursor solid; Step 2, Grind and sieve the obtained ZrC / ZrB 2 Precursor solid (300 mesh) to obtain micron-sized ZrC / ZrB 2 Precursor powder, place it in a graphite box and perform pretreatment in a crosslinking box. The pretreatment temperature is 170 °C and the pretreatment time is 3 h; Step 3, The composition of the raw materials is as follows by weight: 100 parts of ethylene propylene diene monomer; Pretreated ZrC / ZrB 2 20 parts of precursor powder; 20 parts of aramid fiber; 20 parts of boron phenolic resin; 6 parts of zinc oxide; 2 parts of stearic acid; 2 parts of DCP; Mix the raw materials of each group on an open mill for 30 min until evenly mixed. The roller spacing for thin pass is 0.8 mm, and the number of thin passes is 10 times to obtain the initial film. Let it stand for 10 h, cool the film temperature, and release the stress generated during rubber mixing; Step 4: Place a mold with dimensions of Φ 30 mm × 10 mm on a flat vulcanizing machine, preheat it to 170 °C, and spray a release agent. Cut the film according to the size requirements and fill it into the mold. Vulcanize it on the flat vulcanizing machine at 170 °C and 5 MPa for 30 min, then take out the mold and cool it to obtain ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer (EPDM) composite material.

[0030] Comparative example A thermal protection material, the composition of its raw materials is as follows by weight: 100 parts of ethylene propylene diene monomer (EPDM); 15 parts of aramid fiber; 15 parts of boron phenolic resin; 3 parts of zinc oxide; 1.5 parts of stearic acid; 1.5 parts of dicumyl peroxide (DCP). Mix each group of raw materials on an open mill for 25 min until evenly mixed. The roller spacing for thin passing is 0.5 mm, and the number of thin passing times is 10 times to obtain an initial film. Let it stand for 9 h, cool the temperature of the film, and release the stress generated during rubber mixing; Place a mold with dimensions of Φ 30 mm × 10 mm on a flat vulcanizing machine, preheat it to 160 °C, and spray a release agent. Cut the film according to the size requirements and fill it into the mold. Vulcanize it on the flat vulcanizing machine at 160 °C and 4 MPa for 45 min, then take out the mold and cool it to obtain an ethylene propylene diene monomer (EPDM) composite material. Its properties are shown in Table 1.

[0031] The comparative example is the preparation process of the ethylene propylene diene monomer (EPDM) composite material in Example 3, only removing the ZrC / ZrB 2 precursor in the raw materials.

[0032] The following Table 1 shows the specific performance comparison of the ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer (EPDM) composite materials prepared in Examples 1 - 6 and the ethylene propylene diene monomer (EPDM) composite materials in the comparative example: Table 1

[0033] Based on the experimental data analysis in Table 1, compared with the ethylene propylene diene monomer (EPDM) composite material in the comparative example, the density and thermal conductivity of the ZrC / ZrB 2 precursor-modified ethylene propylene diene monomer (EPDM) composite materials prepared in Examples 1 - 6 are basically unchanged, but the hardness, tensile strength, elongation at break, and ablation performance are greatly improved. The ZrC / ZrB 2The hardness of the precursor-modified ethylene propylene diene monomer (EPDM) rubber composite is 66 HA - 75 HA, with the maximum increase in hardness being 25% compared to the comparative example; the tensile strength values of Examples 1 - 6 are 5.29 Mpa - 6.49 Mpa, with the maximum increase in tensile strength being 54.5% compared to the comparative example; the elongation at break ranges of Examples 1 - 6 are 616.87% - 705.9%, with the maximum increase in elongation at break being 66.1% compared to the comparative example; the linear ablation rate ranges of Examples 1 - 6 are 0.074 mm / s - 0.107 mm / s, with the linear ablation rate being reduced by 53.5% compared to the comparative example; the mass ablation rate ranges of Examples 1 - 6 are 0.041 - 0.057 g / s, with the mass ablation rate being reduced by 44.6% compared to the comparative example.

[0034] By adding ZrC / ZrB 2 precursor to the EPDM rubber composite and precisely regulating the content of the precursor components (preferably 5 wt% - 20 wt%) and the type of boron source, the synergistic optimization of the mechanical properties and thermal stability of the composite can be achieved. As Figure 3 shown from left to right in the figure are the ZrC / ZrB 2 precursor-modified EPDM rubber composites obtained from Examples 1 - 6, and the ZrC / ZrB 2 precursor forms a uniformly dispersed structure in the rubber matrix. 2 The surface-active hydroxyl groups contained in the ZrC / ZrB precursor chemically couple with the internal fillers in the rubber to form an interfacial enhancement layer, which is beneficial to improving the stress transfer efficiency; and the precursor forms hydrogen bonds with the hydrogen on the organic macromolecular chains in the rubber, forming a secondary cross-linking network that penetrates the matrix in the rubber as dynamic physical cross-linking points, which can effectively inhibit the propagation of microcracks. The synergistic effect of the hydrogen bond network and the chemical cross-linking network is beneficial to inhibiting the slippage of rubber molecular chains and enhancing the elongation at break of the composite. The tensile curve is as Figure 5 shown.

[0035] At the same time, in the ablation experiment, the in-situ ceramization reaction of the precursor at high temperature generates a continuous and dense Zr - B - C - N ceramic barrier layer, which reduces the ablation heat flux density, delays the heat transfer to the interior, and enhances the ablation resistance performance and service time of the rubber; and under high-temperature ablation, the filler network enables the material to maintain high thermal stability while effectively inhibiting the damage of the composite caused by thermal shock, greatly prolonging the service life of the composite.

[0036] In the present invention, the EPDM rubber is modified by the ZrC / ZrB 2 precursor in the form of a polymer, avoiding the interfacial mismatch problem existing in inorganic ceramic fillers, and at the same time, the filler mixing is more uniform. During service, the ZrC / ZrB 2The precursor will gradually transform into the ceramic phase at high temperature. During the transformation process, the heat energy released is absorbed, thereby prolonging the service time of the material to improve the high-temperature resistance and ablation resistance of the rubber. Moreover, the ultra-high temperature ceramic particles after ceramization have extremely high melting points, excellent mechanical properties, and good thermal shock resistance, greatly improving the antioxidant ablation performance of ethylene propylene diene monomer rubber.

Claims

1. A method for preparing a ZrC / ZrB2 precursor modified EPDM rubber composite material, characterized in that: Follow the steps below to implement it: Step 1, preparing a ZrC / ZrB2 precursor; Step 2, grinding and sieving the ZrC / ZrB2 precursor in step 1 to obtain micron-sized precursor powder, and then placing it in a graphite box and performing pretreatment in a cross-linking box; Step 3, mixing the ZrC / ZrB2 precursor modified EPDM rubber composite material; Step 4, vulcanization molding of ZrC / ZrB2 precursor modified EPDM rubber composite material.

2. The method for preparing the ZrC / ZrB2 precursor modified EPDM rubber composite material according to claim 1, characterized in that: The step 1 is specifically as follows: in an oxygen-free and water-free environment, zirconium tetrachloride is used as a zirconium source, dissolved and stirred with ethanol in a three-necked flask for organicization, and acetylacetone is added as a chelating agent for chelating reaction; a boron source is then added, and after reflux reaction, the solvent is removed by reduced pressure distillation, and after cooling to room temperature, it is transferred to a vacuum drying oven for drying to obtain a ZrC / ZrB2 precursor.

3. The method for preparing the ZrC / ZrB2 precursor modified EPDM rubber composite material according to claim 2, characterized in that: In step 1, the molar ratio of zirconium tetrachloride: ethanol: acetylacetone: boron source is 1:20:4:3, the boron source is a mixture of one or more of boron phenolic acid, boric acid, and phenylboric acid, and argon gas is introduced into the three-necked flask to ensure an oxygen-free environment.

4. The method for preparing the ZrC / ZrB2 precursor modified EPDM rubber composite material according to claim 2, characterized in that: In step 1, the temperature of the organic treatment is 20°C-30°C, and the time is 30min-60min; the temperature of the chelating reaction is 50°C-60°C, and the time is 60min-90min; the temperature of the reflux reaction is 100°C-140°C, and the reaction time is 2h; the temperature of the vacuum drying process is 60°C-70°C, and the drying time is 8h-12h.

5. The method for preparing the ZrC / ZrB2 precursor modified EPDM rubber composite material according to claim 1, characterized in that: In the step 2, the sieving parameter is 300 mesh, the precursor powder pretreatment temperature is 150° C.-170° C., and the pretreatment time is 1 h-3 h.

6. The method for preparing the ZrC / ZrB2 precursor modified EPDM rubber composite material according to claim 1, characterized in that: The step 3 is specifically as follows: according to the weight fraction of the raw material components: 100 parts of EPDM rubber; 5 parts to 20 parts of pretreated ZrC / ZrB2 precursor powder; 10 parts to 20 parts of aramid fiber; 10 parts to 20 parts of boron phenolic; 1-6 parts of zinc oxide; 1-2 parts of stearic acid; 1-2 parts of DCP. Mix each group of raw materials in an open mixer according to the ratio, and then adjust the roller spacing to perform thin mixing to obtain an initial film. Let it stand for 8h-10h and cool the film temperature.

7. The method for preparing the ZrC / ZrB2 precursor modified EPDM rubber composite material according to claim 6, characterized in that: In the step 3, the mixing time is 20 min-30 min, the roller spacing of the thin pass of the mixing mill is not greater than 1 mm, and the number of thin passes is 8-10 times.

8. The method for preparing the ZrC / ZrB2 precursor modified EPDM rubber composite material according to claim 1, characterized in that: The step 4 is specifically as follows: placing the mold on a flat vulcanizer for preheating and spraying a release agent, cutting the film in step 3 according to size requirements and filling it in the mold for flat vulcanization, and then removing the mold and cooling it.

9. The method for preparing the ZrC / ZrB2 precursor modified EPDM rubber composite material according to claim 8, characterized in that: In the step 4, during the vulcanization of the plate, the vulcanization temperature is 150° C.-170° C., the vulcanization pressure is 3 MPa-5 MPa, and the vulcanization time is 30 min-60 min.

10. A ZrC / ZrB2 precursor modified EPDM rubber composite material prepared according to the method for preparing a ZrC / ZrB2 precursor modified EPDM rubber composite material according to any one of claims 1 to 9.

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