ZrC / ZrB2 Precursor-Modified Ethylene Propylene Diene Monomer Rubber Composite Material and Preparation Method Thereof

Abstract

The present invention discloses a preparation method of a ZrC / ZrB2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material, which is specifically implemented according to the following steps: Step 1, prepare the ZrC / ZrB2 precursor; Step 2, grind and screen the ZrC / ZrB2 solid in Step 1 to obtain a micron-level precursor powder, and then place it in a graphite box for pretreatment in a crosslinking box; Step 3, knead the ZrC / ZrB2 precursor-modified EPDM rubber composite material; Step 4, vulcanize and mold the ZrC / ZrB2 precursor-modified EPDM rubber composite material. The present invention also discloses the composite material prepared by this method. The present invention modifies the EPDM rubber with a polymer-form ZrC / ZrB2 precursor, avoiding the interfacial mismatch problem existing in inorganic ceramic fillers, and at the same time, the filler mixing is more uniform.

Description

Technical Field

[0001] The present invention belongs to the technical field of novel composite materials, and particularly relates to a ZrC / ZrB2 precursor-modified ethylene propylene diene monomer (EPDM) composite material. The present invention also relates to a preparation method of the composite material. Background Art

[0002] A solid rocket motor is an important part of an aerospace vehicle. Its combustion chamber mainly consists of a shell, an insulation layer, a liner, and a propellant 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, ablative-resistant fillers, flame retardants, and some formulations also need to select 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 it is required to have good compatibility with the shell material and the propellant to ensure firm bonding between the insulation layer and the shell and the propellant grain interfaces. Ethylene propylene diene monomer (EPDM) is an ideal matrix material for the internal insulation material. 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 also has a low density and a large specific heat capacity.

[0003] Ethylene propylene diene monomer (EPDM) is an ideal matrix material for the internal insulation layer of a solid rocket, but it also has 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 an aerospace vehicle. Some high-performance fillers need to be added for modification. In addition, traditional EPDM composite materials mostly use EPDM 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 temperatures, the rubber matrix will pyrolyze to form a carbonized layer, which has good heat insulation performance. However, under the long-term erosion of hot gas and high-speed particles, the material will crack and oxidize to produce a large amount of gases such as CO2 volatilization, resulting in phenomena such as large ablation and warping deformation, and the mechanical properties will rapidly decline, greatly weakening the thermal protection effect.

[0004] At present, 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, montmorillonite, etc. 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 forming 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 to further improve the density and strength of the ceramic body. 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 structure and mechanical properties of the final rubber. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of ZrC / ZrB2 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 purpose of the present invention is to provide a composite material prepared by the preparation method of ZrC / ZrB2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material.

[0007] The first technical solution adopted by the present invention is a preparation method of ZrC / ZrB2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material, which is specifically implemented according to the following steps:

[0008] Step 1, prepare ZrC / ZrB2 precursor;

[0009] Step 2, grind and sieve the ZrC / ZrB2 precursor in Step 1 to obtain micron-sized precursor powder, and then place it in a graphite box for pretreatment in a crosslinking box;

[0010] Step 3, mixing of ZrC / ZrB2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material;

[0011] Step 4, vulcanization and molding of ZrC / ZrB2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material.

[0012] The characteristics of the first technical solution of the present invention also lie in that

[0013] 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 organification, 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 a ZrC / ZrB2 precursor.

[0014] 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.

[0015] In Step 1, the temperature for organification 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.

[0016] 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.

[0017] 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 / ZrB2 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-sheet mixing to obtain an initial film, place it for 8 h - 10 h, and cool the film temperature.

[0018] In Step 3, the mixing time is 20 min - 30 min, the roller gap for thin-sheet mixing on the open mill is not more than 1 mm, and the number of thin-sheet passes is 8 - 10 times.

[0019] 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 the product.

[0020] 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.

[0021] The second technical solution adopted by the present invention is a ZrC / ZrB2 precursor-modified ethylene propylene diene monomer rubber composite material prepared by the preparation method of the ZrC / ZrB2 precursor-modified ethylene propylene diene monomer rubber composite material.

[0022] The beneficial effects of the present invention are as follows:

[0023] (1) During the combustion or pyrolysis process of the ZrC / ZrB2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material prepared by the present invention, the residue after the cracking of the matrix material 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 resistance.

[0024] (2) Both the ZrC / ZrB2 precursor and EPDM rubber are in polymer form, and they can be better fused and dispersed during the rolling and mixing process, with a stronger combination between the two, no interfacial mismatch problem, and avoiding the cracking and peeling problems of subsequent ceramic products.

[0025] (3) The ZrC / ZrB2 precursor gradually transforms into the ceramic phase at high temperatures. The transformation process absorbs the released thermal 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 resistance of EPDM rubber. Description of the Drawings

[0026] Figure 1 is the process flow chart of the preparation of the ZrC / ZrB2 precursor-modified EPDM rubber composite material of the present invention;

[0027] Figure 2 is the XRD diffraction pattern of the sintered product of the ZrC / ZrB2 precursor at 1550 °C in the present invention;

[0028] Figure 3 is the physical diagram of the ZrC / ZrB2 precursor-modified EPDM rubber composite material of the present invention;

[0029] Figure 4 is the SEM diagram of the ZrC / ZrB2 precursor-modified EPDM rubber composite material of the present invention;

[0030] Figure 5 is the tensile curve diagram of the ZrC / ZrB2 precursor-modified EPDM rubber composite material of the present invention. Detailed Embodiments

[0031] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0032] The preparation method of the ZrC / ZrB2 precursor-modified EPDM rubber composite material of the present invention, as Figure 1 shown, is specifically implemented according to the following steps:

[0033] Step 1, prepare the ZrC / ZrB2 precursor;

[0034] Specifically, in an oxygen-free and anhydrous environment, zirconium tetrachloride is used as the zirconium source and dissolved and stirred with ethanol in a three-necked flask for organification. Then acetylacetone is added as a chelating agent for chelation reaction. Next, a boron source is added, and after reflux reaction, the solvent is removed by vacuum distillation. After it cools to room temperature, it is transferred to a vacuum drying oven for drying to obtain the ZrC / ZrB2 precursor solid;

[0035] 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 borophenol 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;

[0036] The temperature for organification 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;

[0037] Step 2, grind and sieve the ZrC / ZrB2 solid in Step 1 to obtain micron-sized precursor powder, and then place it in a graphite box for pretreatment in a crosslinking box;

[0038] 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;

[0039] Step 3, mixing of the ZrC / ZrB2 precursor modified ethylene propylene diene monomer (EPDM) composite;

[0040] Specifically, by weight fraction of raw material components: 100 parts of ethylene propylene diene monomer; 5 parts - 20 parts of the pretreated ZrC / ZrB2 precursor powder; 10 parts - 20 parts of aramid fiber; 10 parts - 20 parts of borophenol formaldehyde; 1 part - 6 parts of zinc oxide; 1 part - 2 parts of stearic acid; 1 part - 2 parts of dicumyl peroxide (DCP). According to the ratio, the raw material components are mixed in an open mill, and then the roller gap is adjusted for thin-pass mixing to obtain an initial film, which is placed for 8 h - 10 h to cool the film temperature and release the stress generated during rubber mixing;

[0041] The mixing time is 20 min - 30 min, the roller gap for thin-pass in the open mill is not greater than 1 mm, and the number of thin-pass times is 8 times - 10 times;

[0042] Step 4, vulcanization and molding of the ZrC / ZrB2 precursor modified ethylene propylene diene monomer composite;

[0043] 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;

[0044] 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.

[0045] Example 1

[0046] A preparation method of a ZrC / ZrB2 precursor modified ethylene propylene diene monomer (EPDM) rubber composite material is specifically implemented according to the following steps:

[0047] Step 1, in an oxygen-free and water-free environment, using 0.025 mol of zirconium tetrachloride as the zirconium source, dissolving and stirring it with 0.5 mol of ethanol in a three-necked flask at 20°C for 60 min for organometallization, 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 vacuum distillation, and transferring it to a vacuum drying oven at 60°C for drying for 8 h to obtain a ZrC / ZrB2 precursor solid;

[0048] Step 2, grinding and sieving (300 mesh) the obtained ZrC / ZrB2 precursor solid to obtain a micron-sized ZrC / ZrB2 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;

[0049] Step 3, the raw material composition is as follows by weight: 100 parts of ethylene propylene diene monomer (EPDM) rubber; 5 parts of the pretreated ZrC / ZrB2 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 dicumyl peroxide (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 pass and a thin pass number 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;

[0050] Step 4, placing a mold with dimensions 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 the ZrC / ZrB2 precursor modified ethylene propylene diene monomer (EPDM) rubber composite material after demolding and cooling.

[0051] Example 2

[0052] A preparation method of a ZrC / ZrB2 precursor modified ethylene propylene diene monomer (EPDM) rubber composite material is specifically implemented according to the following steps:

[0053] Step 1, in an oxygen-free and water-free environment, 0.025 mol of zirconium tetrachloride is used as the zirconium source and dissolved and stirred with 0.5 mol of ethanol in a three-necked flask at 20 °C for 60 min for organic modification. Then, 0.1 mol of acetylacetone is added as a chelating agent and reacted at 50 °C for 60 min. Then, 0.075 mol of boric acid is added to provide the boron source, and the reaction is refluxed at 100 °C for 2 h. The solvent is removed by vacuum distillation. After cooling to room temperature, it is transferred to a vacuum drying oven and dried at 60 °C for 8 h to obtain the ZrC / ZrB2 precursor solid.

[0054] Step 2, the obtained ZrC / ZrB2 precursor solid is ground and sieved (300 mesh) to obtain a micron-sized ZrC / ZrB2 precursor powder, which is placed in a graphite box and pretreated in a cross-linking box at a pretreatment temperature of 150 °C for 1 h.

[0055] The pretreated ZrC / ZrB2 precursor is placed in a high-temperature tube furnace and sintered 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 the ZrC / ZrB2 precursor at 1550 °C is two phases of ZrC and ZrB2, and no other impurity phases are generated, indicating the successful preparation of the ZrC / ZrB2 precursor.

[0056] Step 3, the raw material composition is as follows by weight: 100 parts of ethylene propylene diene monomer rubber; 5 parts of the treated ZrC / ZrB2 precursor; 10 parts of aramid fiber; 10 parts of boron phenolic aldehyde; 2 parts of zinc oxide; 1 part of stearic acid; 1 part of DCP. According to the ratio, each group of raw materials is mixed on an open mill for 20 min until evenly mixed. The roller spacing for thin passing is 1 mm, and the number of thin passing times is 9 times to obtain an initial film, which is placed for 8 h to cool the film temperature and release the stress generated during rubber mixing.

[0057] Step 4, a mold with dimensions of Φ 30 mm × 10 mm is placed on a flat vulcanizer and preheated to 150 °C and a release agent is sprayed. The film is cut according to the size requirements and filled into the mold, and flat vulcanization is carried out at 150 °C and 3 MPa for 60 min. After demolding and cooling, a ZrC / ZrB2 precursor-modified ethylene propylene diene monomer rubber composite material is obtained, as Figure 4 shown.

[0058] Example 3

[0059] A preparation method of a ZrC / ZrB2 precursor-modified ethylene propylene diene monomer rubber composite material is specifically implemented according to the following steps:

[0060] Step 1, in an oxygen-free and water-free environment, using 0.025 mol of zirconium tetrachloride as the zirconium source, dissolve and stir 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 aldehyde and 0.0375 mol of boric acid to provide the boron source, reflux and react at 120 °C for 2 h, distill off the solvent under reduced pressure, and transfer it to a vacuum drying oven at 65 °C for drying for 10 h to obtain the ZrC / ZrB2 precursor solid;

[0061] Step 2, grind and sieve the obtained ZrC / ZrB2 precursor solid (300 mesh) to obtain micron-sized ZrC / ZrB2 precursor powder, place it in a graphite box and perform pretreatment in a crosslinking box, with a pretreatment temperature of 160 °C and a pretreatment time of 2 h;

[0062] Step 3, the raw material composition is by weight: 100 parts of ethylene propylene diene monomer rubber; 5 parts of the pretreated ZrC / ZrB2 precursor; 15 parts of aramid fiber; 15 parts of boron phenolic aldehyde; 3 parts of zinc oxide; 1.5 parts of stearic acid; 1.5 parts of DCP; mix each group of raw materials on an open mill for 25 min until evenly mixed, with the roll gap for calendering being 0.5 mm and the number of calendering times being 10 times to obtain the initial film, place it for 9 h, cool the film temperature, and release the stress generated during rubber mixing;

[0063] Step 4, place a mold with dimensions of Φ 30 mm×10 mm on a flat vulcanizer for preheating to 160 °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 160 °C and 4 MPa for 45 min, demold and cool to obtain the ZrC / ZrB2 precursor modified ethylene propylene diene monomer rubber composite material.

[0064] Example 4

[0065] A preparation method of a ZrC / ZrB2 precursor modified ethylene propylene diene monomer rubber composite material is specifically implemented according to the following steps:

[0066] Step 1, in an oxygen-free and water-free environment, using 0.025 mol of zirconium tetrachloride as the zirconium source, dissolve and stir 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 0.075 mol of phenylboronic acid to provide the boron source, reflux and react at 120 °C for 2 h, distill off the solvent under reduced pressure, and transfer it to a vacuum drying oven at 65 °C for drying for 10 h to obtain the ZrC / ZrB2 precursor solid;

[0067] Step 2: Grind the obtained ZrC / ZrB2 precursor solid and sieve it (300 mesh) to obtain micron-sized ZrC / ZrB2 precursor powder. Place it in a graphite box and perform pre-treatment in a cross-linking box at a pre-treatment temperature of 160 °C for 2 h;

[0068] Step 3: The raw material composition is as follows by weight: 100 parts of ethylene propylene diene monomer rubber; 10 parts of pre-treated ZrC / ZrB2 precursor powder; 15 parts of aramid fiber; 15 parts of boron phenolic aldehyde; 4 parts of zinc oxide; 1.5 parts of stearic acid; 1.5 parts of DCP. Mix each group of raw materials on an open mill for 25 min until evenly mixed. The roller gap for thin pass is 0.5 mm, and the number of thin passes is 9 times to obtain an initial film. Place it for 9 h, cool the film temperature, and release the stress generated during rubber mixing;

[0069] Step 4: Place a mold with dimensions of Φ 30 mm×10 mm on a flat vulcanizer, 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 vulcanizer at 160 °C and 4 MPa for 45 min, and take out the mold and cool it to obtain a ZrC / ZrB2 precursor-modified ethylene propylene diene monomer rubber composite material.

[0070] Example 5

[0071] A preparation method of a ZrC / ZrB2 precursor-modified ethylene propylene diene monomer rubber composite material is specifically implemented according to the following steps:

[0072] 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 organification, and then add 0.1 mol of acetylacetone as a chelating agent and react at 70 °C for 90 min; then add 0.0375 mol of phenylboronic acid and 0.0375 mol of boric acid to provide the boron source, reflux and react at 140 °C for 2 h, distill off the solvent under reduced pressure, and transfer it to a vacuum drying oven after cooling to room temperature and dry it at 70 °C for 12 h to obtain a ZrC / ZrB2 precursor solid;

[0073] Step 2: Grind the obtained ZrC / ZrB2 precursor solid and sieve it (300 mesh) to obtain micron-sized ZrC / ZrB2 precursor powder. Place it in a graphite box and perform pre-treatment in a cross-linking box at a pre-treatment temperature of 170 °C for 3 h;

[0074] Step 3: The raw material composition is as follows by weight: 100 parts of ethylene propylene diene monomer (EPDM); 15 parts of pretreated ZrC / ZrB2 precursor powder; 20 parts of aramid fiber; 20 parts of boron phenolic aldehyde; 5 parts of zinc oxide; 2 parts of stearic acid; 2 parts of dicumyl peroxide (DCP). Mix each group of raw materials on an open mill for 30 min until evenly mixed. The roller gap for thin passing is 0.8 mm, and the number of thin passing times is 9 to obtain an initial film. Let it stand for 10 h, cool the film temperature, and release the stress generated during rubber mixing.

[0075] 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 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 out the mold and cool it to obtain a ZrC / ZrB2 precursor modified EPDM composite material.

[0076] Example 6

[0077] A preparation method of a ZrC / ZrB2 precursor modified EPDM composite material is specifically implemented according to the following steps:

[0078] 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 organification, 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 aldehyde, 0.025 mol of boric acid, and 0.025 mol of phenylboronic acid to provide a boron source, reflux and react at 140 °C for 2 h, remove the solvent by reduced pressure distillation, and transfer it to a vacuum drying oven at 70 °C for drying for 12 h after cooling to room temperature to obtain a ZrC / ZrB2 precursor solid.

[0079] Step 2: Grind the obtained ZrC / ZrB2 precursor solid and sieve it (300 mesh) to obtain a micron-sized ZrC / ZrB2 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.

[0080] Step 3: The raw material composition is as follows by weight: 100 parts of EPDM; 20 parts of pretreated ZrC / ZrB2 precursor powder; 20 parts of aramid fiber; 20 parts of boron phenolic aldehyde; 6 parts of zinc oxide; 2 parts of stearic acid; 2 parts of DCP. Mix each group of raw materials on an open mill for 30 min until evenly mixed. The roller gap for thin passing is 0.8 mm, and the number of thin passing times is 10 to obtain an initial film. Let it stand for 10 h, cool the film temperature, and release the stress generated during rubber mixing.

[0081] Step 4: Place a mold with dimensions of Φ 30 mm×10 mm on a flat vulcanizer, 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 vulcanizer at 170 °C and 5 MPa for 30 min, then take it out of the mold and cool it to obtain the ZrC / ZrB2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite material.

[0082] Comparative example

[0083] A thermal protection material, the composition of its raw materials by weight is as follows: 100 parts of ethylene propylene diene monomer (EPDM) rubber; 15 parts of aramid fiber; 15 parts of boron phenolic aldehyde; 3 parts of zinc oxide; 1.5 parts of stearic acid; 1.5 parts of dicumyl peroxide (DCP). Mix the raw materials of each group on an open mill for 25 min until evenly mixed. The roller gap for thin pass is 0.5 mm, and the number of thin passes is 10 times to obtain the initial film. Let it stand for 9 h, cool the temperature of the film, and release the stress generated during rubber mixing.

[0084] Place a mold with dimensions of Φ 30 mm×10 mm on a flat vulcanizer, 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 vulcanizer at 160 °C and 4 MPa for 45 min, then take it out of the mold and cool it to obtain the ethylene propylene diene monomer (EPDM) rubber composite material. Its properties are shown in Table 1.

[0085] The comparative example is the preparation process of the ethylene propylene diene monomer (EPDM) rubber composite material in Example 3, only removing the ZrC / ZrB2 precursor in the raw materials.

[0086] The following Table 1 is a specific performance comparison table of the ZrC / ZrB2 precursor-modified ethylene propylene diene monomer (EPDM) rubber composite materials prepared in Examples 1-6 and the ethylene propylene diene monomer (EPDM) rubber composite material in the comparative example:

[0087] Table 1

[0088]

[0089] Based on the experimental data analysis in Table 1, compared with the ethylene-propylene-diene monomer (EPDM) rubber composite of the comparative example, the density and thermal conductivity of the ZrC / ZrB2 precursor modified EPDM rubber composites prepared in Examples 1 - 6 are basically unchanged, but the hardness, tensile strength, elongation at break, and ablation performance are greatly improved. The hardness of the ZrC / ZrB2 precursor modified EPDM rubber composites prepared in Examples 1 - 6 is 66 HA - 75 HA, with the maximum hardness increase of 25% compared with the comparative example; the tensile strength values of Examples 1 - 6 are 5.29 Mpa - 6.49 Mpa, with the maximum tensile strength increase of 54.5% compared with the comparative example; the elongation at break range of Examples 1 - 6 is 616.87% - 705.9%, with the maximum elongation at break increase of 66.1% compared with the comparative example; the linear ablation rate range of Examples 1 - 6 is 0.074 mm / s - 0.107 mm / s, with the linear ablation rate reduced by 53.5% compared with the comparative example; the mass ablation rate range of Examples 1 - 6 is 0.041 - 0.057 g / s, with the mass ablation rate reduced by 44.6% compared with the comparative example.

[0090] By adding ZrC / ZrB2 precursor to the EPDM rubber composite, accurately controlling the precursor component content (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 in the figure from left to right are the physical pictures of the ZrC / ZrB2 precursor modified EPDM rubber composites obtained in Examples 1 - 6. The ZrC / ZrB2 precursor with a polymer morphology of a specific molecular structure forms a uniformly dispersed structure in the rubber matrix. The surface-active hydroxyl groups contained in the ZrC / ZrB2 precursor chemically couple with the internal fillers in the rubber to form an interface 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 improving the elongation at break of the composite. The tensile curve is as Figure 5 shown.

[0091] Meanwhile, 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, reducing the ablation heat flux density, delaying the heat transfer to the interior, enhancing the anti-ablative 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 thermal shock to the composite, greatly prolonging the service life of the composite.

[0092] The present invention modifies ethylene propylene diene monomer (EPDM) rubber with a polymer-shaped ZrC / ZrB2 precursor, avoiding the interfacial mismatch problem existing in inorganic ceramic fillers, and at the same time making the filler mixing more uniform. During service, the ZrC / ZrB2 precursor gradually transforms into a ceramic phase at high temperature, and the transformation process absorbs the released heat energy to extend the service time of the material, thereby 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 anti-oxidation and ablation performance of ethylene propylene diene monomer (EPDM) rubber.

Claims

1. Preparation method of ZrC / ZrB2 precursor modified ethylene-propylene-diene monomer composite material, characterized in that, The implementation is specifically carried out according to the following steps: Step 1, prepare the ZrC / ZrB2 precursor; Step 2, grind and sieve the ZrC / ZrB2 precursor 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 the ZrC / ZrB2 precursor modified ethylene propylene diene monomer (EPDM) composite; Step 4, vulcanization molding of the ZrC / ZrB2 precursor modified EPDM composite; Specifically, Step 1 is as follows: In an oxygen-free and water-free environment, zirconium tetrachloride is used as the zirconium source, dissolved and stirred with ethanol in a three-necked flask for organification, 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 cools to room temperature, it is transferred to a vacuum drying oven for drying to obtain the ZrC / ZrB2 precursor; Specifically, Step 3 is as follows: Calculated by weight fraction of raw material components: 100 parts of EPDM; 5 parts - 20 parts of the pretreated ZrC / ZrB2 precursor powder; 10 parts - 20 parts of aramid fiber; 10 parts - 20 parts of boron phenolic aldehyde; 1 part - 6 parts of zinc oxide; 1 part - 2 parts of stearic acid; 1 part - 2 parts of dicumyl peroxide (DCP). According to the ratio, the raw materials of each group are mixed in an open mill, and then the roller spacing is adjusted for thin-pass mixing to obtain an initial film, which is placed for 8 h - 10 h to cool the film temperature; In Step 1, the molar ratio of zirconium tetrachloride: ethanol: acetylacetone: boron source is 1:20:4:

3. The boron source is one or more mixtures of boron phenolic aldehyde, boric acid, and phenylboronic acid. Argon is introduced into the three-necked flask to ensure an oxygen-free environment; In Step 1, the temperature of organification 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.

2. The preparation method of the ZrC / ZrB2 precursor modified ethylene-propylene-diene monomer rubber composite according to claim 1, characterized in that, 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.

3. The preparation method of the ZrC / ZrB2 precursor-modified ethylene propylene diene monomer rubber composite according to claim 1, wherein, In Step 3, the mixing time is 20 min - 30 min, the roller spacing 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.

4. The preparation method of the ZrC / ZrB2 precursor modified ethylene-propylene-diene monomer rubber composite according to claim 1, characterized in that, Specifically, Step 4 is as follows: Place the mold on a flat vulcanizer for preheating and spray a release agent. Cut the film in Step 3 according to the size requirements and fill it into the mold for flat vulcanization, and then take out the mold and cool it to obtain the product.

5. The preparation method of the ZrC / ZrB2 precursor modified ethylene-propylene-diene monomer rubber composite according to claim 4, characterized in that, 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.

6. The ZrC / ZrB2 precursor modified EPDM composite prepared by the preparation method of the ZrC / ZrB2 precursor modified EPDM composite according to any one of claims 1 - 5.

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