Radiation-resistant silicone rubber for high-performance cable

Abstract

The invention relates to the technical field of silicone rubber, in particular to radiation-resistant silicone rubber for a high-performance cable. The composite material comprises a high-energy ray attenuation outer layer, a free radical dynamic capture middle layer and a stress buffer combination inner layer, wherein the outer layer contains nano titanium dioxide, cadmium tungstate, phenyl silicone rubber and a silane coupling agent KH-570; the middle layer contains a main antioxidant, an auxiliary antioxidant, vinyl silicone rubber and carbon nanotubes; the outer layer and the middle layer are crosslinked to form an interpenetrating network to improve the diffusion efficiency of free radicals, the antioxidant in the middle layer diffuses in a gradient manner to inhibit oxidation, and the white carbon black in the inner layer diffuses to form a nano anchor to enhance interlocking and free radical capture; the silicone rubber cable material has the advantages that the silicone rubber cable material can inhibit breakage and excessive crosslinking of silicone rubber molecular chains from ray shielding, free radical removal and stress relief, the protection efficiency is enhanced through a cross-layer synergistic mechanism, the comprehensive performance of the material in the intense radiation environment is effectively improved, and the long-term stable application of the silicone rubber cable in the intense radiation environment is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone rubber, in particular to a radiation-resistant silicone rubber for high-performance cables. Background Art

[0002] With the rapid development of modern science and technology, the demand for high-performance cables is increasing in many fields, such as aerospace, nuclear energy utilization, and electronic information, and extremely stringent requirements are being placed on their performance. Silicone rubber has become a common choice in the field of cable materials due to its excellent high temperature resistance, chemical corrosion resistance, good electrical insulation properties, and long-term use in a wide temperature range.

[0003] However, in these application scenarios, cables are often exposed to high-energy rays, which can cause the silicone rubber molecular chains to break (degrade) or over-crosslink (harden and become brittle), thereby reducing the performance of the silicone rubber, affecting the normal use of the cables, shortening their service life, and even causing safety accidents.

[0004] In the existing technology, the radiation resistance of silicone rubber is usually improved by adding radiation-resistant additives and changing the molecular structure of silicone rubber. For example, adding lead oxide, bismuth trioxide, and gadolinium oxide as radiation-resistant additives can improve the radiation resistance of silicone rubber, but these methods are still insufficient for silicone rubber cables that are exposed to strong radiation environments for a long time. On the one hand, the amount of additives added is limited, and excessive addition will affect other properties of silicone rubber, such as processing properties and mechanical properties. On the other hand, simple additives cannot fundamentally solve the damage of high-energy rays to the silicone rubber molecular chain. Not only can they not completely inhibit the breakage and excessive cross-linking of the molecular chain, they may also reduce some of the original excellent properties of silicone rubber, such as flexibility and electrical insulation, thereby limiting the long-term stable application of silicone rubber cables in strong radiation environments.

[0005] In view of this, there is an urgent need for a high-performance radiation-resistant silicone rubber for cables. Summary of the Invention

[0006] The object of the present invention is to provide a high-performance radiation-resistant silicone rubber for cables to solve the problems raised in the above background technology.

[0007] To achieve the above objectives, firstly, the present invention provides a radiation-resistant silicone rubber for high-performance cables, comprising a high-energy ray attenuation outer layer, a free radical dynamic capture middle layer, and a stress buffering bonding inner layer:

[0008] The high-energy ray attenuation outer layer comprises at least 30-40 parts of nano-titanium dioxide with a particle size of 20-40 nm, 25-30 parts of cadmium tungstate (CdWO4), 20-25 parts of phenyl silicone rubber with a phenyl content of 20%-25%, and 1-2 parts of silane coupling agent KH-570, wherein: the nano-titanium dioxide can scatter gamma rays and electron beams below 50 keV at high frequencies through the strong scattering effect of the nano-particle size; at the same time, the surface hydroxyl groups thereof form a hydrogen bond network with the phenyl silicone rubber through the silane coupling agent KH-570, thereby improving the dispersion of the filler and preventing agglomeration from forming a ray penetration channel; the cadmium tungstate is a high atomic number shielding material (Z=48) that can shield X-rays and gamma rays above 50 keV. The photoelectric absorption effect is generated by absorbing the K-edge energy value of cadmium tungstate to generate photoelectrons and Auger electrons to consume energy, and form energy segment complementarity with nano-titanium dioxide, covering a wide range of radiation spectrum; the conjugated π electron cloud of the phenyl chain segment of the phenyl silicone rubber can disperse the radiation energy and inhibit the breakage of the molecular chain; the silane coupling agent KH-570 uses "bifunctional bridging" to condense with the nano-filler at one end and copolymerize with the phenyl silicone rubber at the other end to form a covalent bonding interface, thereby improving the bonding strength between the filler and the matrix and preventing the filler from falling off under radiation; in addition, a "scattering-absorption double-layer barrier" is constructed by nano-titanium dioxide and cadmium tungstate, phenyl silicone rubber acts as a flexible carrier to fix the spatial distribution of the filler, and the coupling agent strengthens the interface bonding to form a multi-level radiation attenuation network;

[0009] The free radical dynamic capture intermediate layer comprises at least 10-15 parts of a primary antioxidant, 4-6 parts of a secondary antioxidant, 65-70 parts of vinyl silicone rubber, and 3-5 parts of carbon nanotubes (CNTs) with a diameter of less than 5 nm, wherein: the primary antioxidant is a hindered phenol antioxidant, which can quench primary free radicals generated by irradiation in a short time through the transfer of phenolic hydroxyl hydrogen atoms, and its long alkyl chain has good compatibility with the substrate, thereby increasing the stability of the antioxidant process; the secondary antioxidant is dilauryl thiodipropionate (DLTP), which decomposes peroxides with the help of thioether groups, forming a cyclic action mechanism with the primary antioxidant to enhance the antioxidant effect; the carbon nanotubes adsorb free radicals through their high specific surface area and act as nano-heat-conducting channels to conduct heat generated by irradiation, thereby reducing the temperature rise and inhibiting thermal-oxidative synergistic damage; the vinyl silicone rubber comprises at least 0.5-0.7 parts of a cross-linking agent to form a network structure with low cross-linking density and construct a free radical diffusion channel;

[0010] The stress buffer bonding inner layer comprises at least 22-28 parts of fumed silica with a particle size of 8-12 nm, 12-18 parts of a flexible toughening agent with a molecular weight of 50,000-80,000, 55-60 parts of a vinyl silicone rubber of the same material as the cable matrix, and 1-2 parts of a silane coupling agent KH-590, wherein: the fumed silica forms a "filler-coupling agent" chemical anchor point through the condensation of the surface silanol group with the methoxy group of the silane coupling agent KH-590, and at the same time, the primary particles are entangled through hydrogen bonds to form a nano-scale network structure, so that the peeling strength between the inner layer and the cable matrix is ​​improved; the flexible toughening agent is polydimethylsiloxane (PDMS), and its linear molecular chain is interspersed in the vinyl silicone rubber. A "rigid-flexible" structure is formed in the rubber network, absorbing radiation-induced volume expansion stress through conformational changes in the flexible chain segments, thereby increasing the elongation at break of the inner layer and reducing stress. At the same time, chemical bonding is formed with the vinyl silicone rubber, which is the same material as the cable matrix, through a co-vulcanization process, eliminating the risk of interface delamination. Its low molecular weight chain segments diffuse to form a 10-20μm transition layer. The silane coupling agent KH-590 reacts with the hydroxyl group of silica through the mercapto group and copolymerizes the vinyl group with the vinyl silicone rubber to form a "filler-coupling agent-matrix" covalent bridging network, thereby enhancing the shear strength of the free radical dynamic capture intermediate layer and the stress buffer bonded inner layer, forming a dual protection mechanism of interface reinforcement and stress dissipation.

[0011] The phenyl segments of the high-energy ray attenuating outer layer of phenyl silicone rubber react with the vinyl silicone rubber of the free radical dynamic capture middle layer through cross-linking to form a "phenyl segment-vinyl segment" interpenetrating network; the antioxidant molecules in the free radical dynamic capture middle layer diffuse to the inner and outer layers with a concentration gradient, forming an antioxidant-rich layer 10-15 μm thick in the outer layer to inhibit the oxidative chain breakage of the phenyl silicone rubber. At the same time, the stress buffering combined with the low molecular weight chains of the flexible toughening agent in the inner layer migrate to the free radical dynamic capture middle layer, reducing the resistance to the movement of the antioxidant molecules and increasing the free radical scavenging rate, forming a "dynamic protection gradient"; the stress buffering combined with the inner layer of fumed silica diffuses into the free radical dynamic capture middle layer through the interface to a depth of 20-30 nm, forming a "nano-anchor" structure, which not only enhances the mechanical interlocking between the layers but also serves as a secondary site for free radical capture (hydroxyl adsorption of silica surface·OH free radicals), further improving the free radical scavenging efficiency of the free radical dynamic capture middle layer.

[0012] Second, according to Figure 1 As shown, the present invention provides a radiation-resistant silicone rubber for high-performance cables, which also includes the following steps of preparing the silicone rubber:

[0013] S1. Preparation of high-energy ray attenuation outer layer slurry: pre-plasticize the phenyl silicone rubber, then add nano-titanium dioxide, cadmium tungstate and alkane coupling agent KH-570 into a high-speed disperser, and stir at 75-85°C and 1800-2200 r / min for 30-40 min to allow condensation of hydroxyl groups on the filler surface with methoxy groups of the coupling agent. Then, add the pre-plasticized phenyl silicone rubber, and continue stirring for 1-1.5 h. During this period, ultrasonic vibration (frequency 35-45 kHz, power 450-550 W) is used to assist dispersion. The mixture is cyclically ground 3-4 times on a three-roll mill (roller spacing 10 μm) until the filler dispersion is ≥95% (D90 ≤60 nm as measured by a laser particle size analyzer), and the slurry viscosity is 5000-8000 mPa·s to form a high-energy ray attenuation outer layer slurry;

[0014] Pre-plasticization treatment steps: put the phenyl silicone rubber into a two-roll mill, under the conditions of roller temperature of 100-110℃ and roller distance of 1-2mm, first thin pass 2-3 times to soften the rubber material and wrap the roller, then adjust the roller distance to 0.5-1mm for thin pass operation, and thin pass 8-10 times in total. After each thin pass, make a triangle bag and turn over to fully shear the phenyl silicone rubber, so that the molecular weight distribution is uniform and the vinyl activity in the molecular chain is activated at the same time;

[0015] S2. Dynamic capture of free radicals and mixing of the intermediate rubber material: first put the vinyl silicone rubber into a two-roll mill, and pass it through 5-8 times at a roller temperature of 55-65°C and a roller distance of 0.5-0.8mm to fully plasticize it and evenly wrap the roller. Then, add the main antioxidant and the auxiliary antioxidant in turn, and mix them for 10-15 minutes at a roller distance of 2-3mm to completely disperse the filler. Then, add the carbon nanotubes by the segmented feeding method, and pass it through the roller distance of 0.3-0.5mm to achieve carbon nanotubes through strong shear force. The rollers are uniformly dispersed into the tubes, during which the roller temperature is controlled not to exceed 80°C by circulating water cooling. Finally, a cross-linking agent (such as double 25) is added and mixed for 8-12 minutes at a roller distance of 3-4 mm until there is no granular filler. A microscope is used to detect that there are no agglomerates with a size greater than 50 μm. After unrolling, the sheets are placed in an environment of 23±2°C and relative humidity of 50±5% for 24 hours to allow the antioxidant to form a concentration gradient through molecular thermal motion, thereby forming an intermediate layer rubber compound with a gel content of 45%-50% and a low cross-linking density;

[0016] S3. Co-vulcanization pretreatment of stress buffering and inner layer rubber compound: first, put the cable matrix, vinyl silicone rubber and flexible toughening agent into a planetary mixer, and stir at a speed of 150-180r / min at 90-100℃ in a vacuum environment for 50-60min. Through mechanical shearing and molecular thermal motion, the flexible chain segments of the flexible toughening agent are evenly dispersed in the silicone rubber matrix. Then, add fumed silica and silane coupling agent KH-590, and knead for 2-2.5h at 110-120℃ and 0.4-0.6MPa pressure to make the silanol group on the surface of fumed silica condense with the mercapto group of silane coupling agent KH-590 to form Si-O-Si covalent bonds. At the same time, the linear molecular chains of the flexible toughening agent are interspersed in the silicone rubber network, and a "rigid-flexible interlocking" structure is formed through physical entanglement and chemical cross-linking, forming a stress buffering and inner layer rubber compound with high ductility and strong interface bonding force.

[0017] S4. Three-layer co-extrusion coating and gradient cross-linking: Using a three-layer co-extrusion device with a screw length-diameter ratio of 28:1, the high-energy ray attenuation outer layer slurry is coated on the surface of the cable infrastructure through a screw extruder at a temperature of 110-130°C and a line speed of 0.5-1.0m / min to form an 80-120μm thick shielding layer. Then, the middle layer rubber is covered on the outer layer with a thickness of 40-60μm by a gravure roller coater with an anilox roller line number of 200-300 lines / inch. The active groups of the middle layer cross-linking agent (double 25) are initially contacted and reacted with the vinyl groups of the outer layer phenyl silicone rubber to form a transition cross-linking zone. Finally, the stress buffer is combined with the inner layer rubber and the cable infrastructure by a hot pressing device at a pressure of 1.2-1.5MPa and a temperature of 150-160°C for 30-45min to form a gradient cross-linking structure of "shielding layer-capture layer-buffer layer";

[0018] S5. Post-electron beam irradiation treatment and performance optimization: The coated cable is sent to the electron beam irradiation chamber and irradiated with a cumulative dose of 15-20kGy at a dose rate of 5-10kGy / h at room temperature. At this time, the electron beam triggers a copolymerization reaction between the vinyl groups in the outer layer phenyl silicone rubber and the middle layer vinyl silicone rubber, thereby increasing the density of the interpenetrating network and promoting the inner layer of fumed silica nanoparticles to diffuse and penetrate into the middle layer to a depth of 20-30nm, forming a dense "nano-anchor" structure. After irradiation, the cable is placed in an environment of 70-75℃ for 24h aging treatment to complete the concentration gradient distribution of the antioxidant molecules, and finally a radiation-resistant silicone rubber cable material is obtained.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The radiation-resistant silicone rubber used in this high-performance cable has a three-layer composite structure consisting of a high-energy ray attenuation outer layer, a free radical dynamic capture middle layer, and a stress buffering inner layer. The outer layer of nano-titanium dioxide and cadmium tungstate forms a "scattering-absorption double-layer barrier" to attenuate ray energy. The main and auxiliary antioxidants in the middle layer work together with carbon nanotubes to capture free radicals and dissipate heat. The inner layer of fumed silica and polydimethylsiloxane achieve interface reinforcement and stress buffering. This material not only inhibits the breakage and excessive cross-linking of silicone rubber molecular chains throughout the entire process from ray shielding and free radical scavenging to stress relief, but also enhances its protective effectiveness through a cross-layer synergistic mechanism. For example, the outer layer of phenyl silicone rubber and the middle layer of vinyl silicone rubber cross-link to form an interpenetrating network, which improves the diffusion efficiency of free radicals into the middle layer. The antioxidant in the middle layer diffuses to the outer layer with a concentration gradient to form an enrichment layer to inhibit oxidative chain breakage. The inner layer of fumed silica diffuses into the middle layer to form "nano-anchors" to enhance mechanical interlocking and free radical capture capabilities. This material can also effectively improve its overall performance in strong radiation environments, thereby increasing the long-term and stable application of silicone rubber cables in strong radiation environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of the steps for preparing the radiation-resistant silicone rubber of the present invention. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] Example 1

[0024] Formula: The high-energy ray attenuation outer layer uses 35 parts of nano-titanium dioxide with a particle size of 30nm, 27 parts of cadmium tungstate, 22 parts of phenyl silicone rubber with a phenyl content of 22% and 1.5 parts of silane coupling agent KH-570; the free radical dynamic capture middle layer uses 12 parts of main antioxidant, 6 parts of auxiliary antioxidant, 68 parts of vinyl silicone rubber and 4 parts of carbon nanotubes with a diameter of less than 5nm; the stress buffer bonding inner layer uses 25 parts of fumed silica with a particle size of 10nm, 18 parts of flexible toughening agent with a molecular weight of 60,000, 58 parts of vinyl silicone rubber of the same material as the cable matrix and 1.5 parts of silane coupling agent KH-590.

[0025] The preparation steps are as follows:

[0026] Preparation of outer layer slurry: Phenyl silicone rubber was put into a two-roll mill and thin-rolled 10 times at a roller temperature of 105°C and a roller gap of 1mm (first, thin-rolled 3 times with a roller gap of 1mm to soften the roller, then adjusted to 0.5mm and thin-rolled 7 times and triangularly rolled) to homogenize the molecular chain and activate the vinyl activity; nano-titanium dioxide, cadmium tungstate and KH-570 were added to a high-speed disperser and stirred at 80°C and 2000r / min for 35min. After the hydroxyl groups on the filler surface condensed with the methoxy groups of the coupling agent, pre-plasticized phenyl silicone rubber was added and stirred for 1.2h. During this period, 40kHz, 500W ultrasonic vibration was applied to assist dispersion; finally, it was cyclically ground 4 times on a three-roll mill (roll gap of 10μm) until D90 = 55nm and the dispersion was ≥95% as measured by a laser particle size analyzer, forming a uniform paste slurry with a viscosity of 6500mPa·s;

[0027] Mixing of the intermediate layer rubber compound: put the vinyl silicone rubber into a two-roll mill, pass it through the mill for 6 times at a roll temperature of 60°C and a roll distance of 0.6mm until it is evenly wrapped around the roll, then add the primary antioxidant and the secondary antioxidant in sequence, and mix for 12 minutes at a roll distance of 2.5mm until the filler is completely dispersed; add carbon nanotubes by a segmented feeding method, disperse them by a thin pass at a roll distance of 0.4mm, and control the roll temperature to ≤75°C by circulating water cooling; finally, add 0.6 parts of a double-two-five crosslinking agent, mix for 10 minutes at a roll distance of 3.5mm until there are no particle agglomerates, and after microscopic examination to find no particles larger than 50μm, remove the sheet and place it in an environment at 23±2°C and 50±5% humidity for 24 hours to form a low crosslinking density rubber compound with a gel content of 48%;

[0028] Pretreatment of the inner rubber compound: The cable matrix, vinyl silicone rubber, and PDMS were placed in a planetary mixer and stirred at 160 rpm for 55 minutes under a vacuum environment at 95°C to uniformly disperse the PDMS flexible chain segments. Fumed silica and KH-590 were added and kneaded at 115°C and 0.5 MPa for 2.2 hours to allow the silanol groups on the silica surface to condense with the mercapto groups in KH-590 to form Si-O-Si covalent bonds. At the same time, the PDMS chain segments were interspersed in the silicone rubber network to form a "rigid-flexible interlocking" structure.

[0029] Three-layer co-extrusion coating and cross-linking: Using a three-layer co-extrusion device with an aspect ratio of 28:1, the outer layer slurry was extruded and coated onto the surface of the cable base structure at a line speed of 0.8m / min at 120°C to form a 100μm thick shielding layer. Then, a gravure roller coater (anilox roller with 250 lines / inch) was used to coat the outer layer with a middle layer of rubber at a thickness of 45μm to form a transitional cross-linking zone. Finally, the inner layer of rubber and the cable base were simultaneously vulcanized for 40 minutes using a hot press laminating device (1.3MPa pressure, 155°C) to form a gradient cross-linking structure.

[0030] Electron beam post-treatment: The coated cable is sent to the electron beam irradiation chamber and irradiated with a cumulative dose of 18kGy at a dose rate of 8kGy / h to form "nano-anchors"; after irradiation, the cable is placed in a 72°C environment for 24 hours to complete the concentration gradient distribution of the antioxidant and obtain the target material.

[0031] Example 2

[0032] Formula: The high-energy ray attenuation outer layer uses 30 parts of nano-titanium dioxide with a particle size of 20nm, 30 parts of cadmium tungstate, 20 parts of phenyl silicone rubber with a phenyl content of 20% and 1 part of silane coupling agent KH-570; the free radical dynamic capture middle layer contains 10 parts of main antioxidant, 4 parts of auxiliary antioxidant, 65 parts of vinyl silicone rubber and 5 parts of carbon nanotubes with a diameter of less than 5nm; the stress buffer bonding inner layer is composed of 22 parts of fumed silica with a particle size of 8nm, 12 parts of flexible toughening agent with a molecular weight of 50,000, 55 parts of vinyl silicone rubber of the same material as the cable matrix and 2 parts of silane coupling agent KH-590.

[0033] Preparation: The preparation process is the same as that of Example 1, but with some differences in parameters: in the preparation of the high-energy ray attenuation outer layer slurry, the high-speed disperser stirring temperature is 75°C, the speed is 1800r / min, the stirring time is 30min and 1h, the ultrasonic frequency is 35kHz, and the power is 450W; in the mixing of the free radical dynamic capture middle layer rubber compound, the roller temperature of the two-roll open mill is 55°C, the roller gap is 0.5mm, and the roller gap is 0.3mm when adding carbon nanotubes; in the stress buffer combined with the inner layer rubber compound co-vulcanization pretreatment, the planetary mixer is at 90 ℃ vacuum environment, stirring at a speed of 150r / min for 50min, kneading temperature of 110℃, pressure of 0.4MPa, and kneading time of 2h; for three-layer co-extrusion coating and gradient cross-linking, the screw extruder temperature is 110℃, the line speed is 0.5m / min, the line number of the gravure roller coater is 200 lines / inch, the hot pressing pressure is 1.2MPa, the temperature is 150℃, and the vulcanization time is 30min; for electron beam irradiation post-treatment, the dose rate is 5kGy / h, the cumulative dose is 15kGy, and the aging treatment temperature is 70℃.

[0034] Example 3

[0035] Formula: The high-energy ray attenuation outer layer is composed of 40 parts of nano-titanium dioxide with a particle size of 40nm, 25 parts of cadmium tungstate, 25 parts of phenyl silicone rubber with a phenyl content of 25% and 2 parts of silane coupling agent KH-570; the free radical dynamic capture middle layer uses 15 parts of main antioxidant, 5 parts of auxiliary antioxidant, 70 parts of vinyl silicone rubber and 3 parts of carbon nanotubes with a diameter of less than 5nm; the stress buffer bonding inner layer uses 28 parts of fumed silica with a particle size of 12nm, 15 parts of flexible toughening agent with a molecular weight of 80,000, 60 parts of vinyl silicone rubber of the same material as the cable matrix and 1 part of silane coupling agent KH-590.

[0036] Preparation: The preparation process is the same as that of Example 1, but with some differences in parameters: when preparing the outer layer slurry for high-energy ray attenuation, the high-speed disperser stirring temperature is 85°C, the speed is 2200r / min, the stirring time is 40min and 1.5h, the ultrasonic frequency is 45kHz, and the power is 550W; when mixing the intermediate rubber compound for free radical dynamic capture, the roller temperature of the two-roll mill is 65°C, the roller gap is 0.8mm, and the roller gap is 0.5mm when adding carbon nanotubes; when stress buffering is combined with the co-vulcanization pretreatment of the inner rubber compound, the planetary mixer is at 100 ℃ vacuum environment, stirring at a speed of 180r / min for 60min, kneading temperature of 120℃, pressure of 0.6MPa, and kneading time of 2.5h; for co-extrusion coating and gradient cross-linking of the three-layer structure, the temperature of the screw extruder is 130℃, the line speed is 1.0m / min, the line number of the gravure roller coater is 300 lines / inch, the hot pressing pressure is 1.5MPa, the temperature is 160℃, and the vulcanization time is 45min; for electron beam irradiation post-treatment, the dose rate is 10kGy / h, the cumulative dose is 20kGy, and the aging treatment temperature is 75℃.

[0037] Table 1 Amounts of raw materials used in Examples 1-3

[0038]

[0039] In order to verify that the radiation-resistant silicone rubber material prepared in the embodiment of the present invention has good radiation resistance and comprehensive mechanical properties, the radiation-resistant silicone rubber material provided in the embodiment of the present invention is described through the following test examples.

[0040] Test example

[0041] The purpose of this test group is to explore the effects of different component ratios on radiation-resistant silicone rubber materials and to detect the radiation resistance, mechanical stability and interface bonding strength of the radiation-resistant silicone rubber materials of the present invention.

[0042] Test objectives: Test group A, test group B, and test group C respectively use the composition ratios of the radiation-resistant silicone rubber materials provided in Examples 1-3; the control examples use control group A, control group B, control group C, and control group D, wherein:

[0043] Control group A

[0044] Formula: 100 parts vinyl silicone rubber, 20 parts bismuth trioxide, 40 parts fumed silica, 2 parts peroxide crosslinker;

[0045] Preparation steps: put vinyl silicone rubber into an open mill and pass it through the roll mill 5 times at a roller temperature of 80°C until it wraps around the roller; then add bismuth trioxide and white carbon black in sequence, mix with a roller distance of 2mm for 15 minutes until the filler is evenly dispersed; then add peroxide crosslinking agent, mix evenly and then take the sheet out, and vulcanize it on a flat vulcanizer at 170°C and 10MPa pressure for 10 minutes to obtain silicone rubber material.

[0046] Control group B

[0047] Formula: 100 parts phenyl silicone rubber (phenyl content 10%), 35 parts fumed silica and 2 parts peroxide crosslinker;

[0048] Preparation steps: Phenyl silicone rubber is put into a two-roll mill, thinned 8 times at a roller temperature of 110°C, and rolled into a triangle bag until uniformly plasticized; then fumed silica is added, and the roller spacing is 1.5mm and mixed for 20 minutes until there are no obvious particles; then a peroxide crosslinking agent is added, and after mixing evenly, it is vulcanized at 175°C and 12MPa pressure on a flat vulcanizer for 12 minutes to obtain the material.

[0049] Control group C

[0050] Formula: The formula of the free radical dynamic capture middle layer and the stress buffer combined inner layer is the same as that of Example 1, but without the high-energy ray attenuation outer layer, and the middle layer rubber is directly coated on the surface of the cable base structure.

[0051] Preparation: During the preparation process, the step of preparing the high-energy ray attenuation outer layer slurry is omitted, and the process starts from the step of mixing the intermediate layer rubber compound for dynamic capture of free radicals. The subsequent steps are the same as those in Example 1, but in the three-layer structure co-extrusion coating and gradient cross-linking steps, the intermediate layer rubber compound is directly coated on the surface of the cable base structure, and then stress buffering combined with the coating and vulcanization of the inner layer rubber compound are performed.

[0052] Control group D

[0053] Formula: The formula of the high-energy ray attenuation outer layer and the stress buffer combined inner layer is the same as that of Example 1, but there is no free radical dynamic capture intermediate layer, and the stress buffer combined inner layer is directly combined with the high-energy ray attenuation outer layer.

[0054] Preparation: During preparation, the high-energy ray attenuation outer layer slurry is prepared first, and then the stress buffering combined inner layer rubber is co-extruded and gradient cross-linked with the outer layer slurry, and the free radical dynamic capture intermediate layer rubber mixing step and related intermediate layer coating operations are omitted. The stress buffering combined inner layer rubber is directly vulcanized synchronously with the high-energy ray attenuation outer layer and the cable base structure in the hot pressing bonding device. The vulcanization conditions are the same as those in Example 1.

[0055] Test method: According to the radiation resistance, mechanical stability and interface bonding strength of the radiation-resistant silicone rubber material of the present invention, tests are carried out respectively. The specific test methods are as follows:

[0056] Radiation resistance: The sample was irradiated with a cobalt-60 source gamma ray device with a cumulative dose of 10 5 Gy irradiation, with a controlled dose rate of 5kGy / h; the tensile strength and elongation at break of the specimens were tested before and after irradiation according to GB / T528-2009. The specimens were dumbbell type III, and the tensile speed was set at 500mm / min. The performance retention rate was calculated using the following formula:

[0057] Tensile strength retention (%) = (tensile strength after irradiation / initial tensile strength) × 100%;

[0058] Retention rate of elongation at break (%) = (elongation at break after irradiation / initial elongation at break) × 100%.

[0059] Mechanical stability: At room temperature (23±2°C), the initial tensile strength and elongation at break of the specimens were tested according to GB / T528-2009, and the Shore A hardness was tested according to GB / T531.1-2008. Five specimens were tested per group and the average value was calculated. The specimens were then aged in an aging chamber at 150°C for 168 hours. After cooling to room temperature, the above tests were repeated. The rate of change in performance was calculated using the following formula:

[0060] Performance change rate (%) = [(performance value after aging - initial performance value) / initial performance value] × 100%.

[0061] Interface bonding strength: According to GB / T2792-2014, the sample was made into a 25mm wide strip and the interface bonding strength between the outer layer and the inner layer was tested by a 180° peel test at a peel speed of 50mm / min in an environment of 23±2°C and a relative humidity of 50±5%. The interface bonding strength was calculated using the following formula:

[0062] Interface bonding strength (N / cm) = peeling force (N) / sample width (cm).

[0063] Specific detection indicators are shown in Table 2.

[0064] Table 2 Test indicators of each sample

[0065]

[0066] As shown in Table 2, the embodiment of the present invention significantly outperforms the control group of the prior art in terms of radiation resistance, mechanical stability, and interface bonding strength through the three-layer composite structure and cross-layer synergistic mechanism. The specific effects are as follows:

[0067] The radiation resistance of the embodiments of the present invention (test groups A, B, and C) is significantly better, with a tensile strength retention rate of 83% to 88% and an elongation at break retention rate of 77% to 82% after irradiation, while that of the control group A is only 52% and 45%, and that of the control group B is 65% and 58%; this is mainly because the "scattering-absorption double-layer barrier" of the outer layer of the present invention can attenuate more than 80% of the incident radiation energy, the main and auxiliary antioxidants and carbon nanotubes in the middle layer can efficiently capture residual free radicals, and the stress buffer structure in the inner layer can eliminate the concentration of irradiation stress, forming a full-process protection, and fundamentally inhibiting molecular chain breakage and excessive cross-linking; the control group A of the prior art relies on a single additive for physical shielding and cannot prevent free radical damage; the control group B has a low phenyl content and no middle layer antioxidant system, so oxidative chain breakage is obvious after irradiation;

[0068] In terms of mechanical stability, the strength change rate of the test group after thermal aging was +2% to +5%, and the hardness change was +4 to +6 ShoreA, which were better than the +12% and +18 ShoreA of the control group A and the +15% and +16 ShoreA of the control group D. The inner layer of polydimethylsiloxane flexible chain segments of the present invention form a "rigid-flexible interlocking" network with the vinyl silicone rubber, the low cross-linking density structure of the middle layer relieves thermal stress, and the outer layer of phenyl silicone rubber enhances thermal stability, so that the material maintains stable mechanical properties over a wide temperature range. The control group C has no outer layer shielding, and the heat-oxidation synergistic damage is aggravated. The control group D has no middle layer to capture peroxides, which causes the material to harden and become brittle.

[0069] In terms of interface bonding strength, the test group was 7.6-8.5 N / cm, which was 69%-89% higher than the control groups A and B. The present invention forms covalent bonds through silane coupling agents, diffuses inner-layer white carbon black nanoparticles to form a "nano-anchor" structure, and cross-links the outer and middle layers to form an interpenetrating network, thereby achieving dual reinforcement of physical entanglement and chemical bonding of interlayer molecular chains. Due to the lack of gradient cross-linking technology and nano-interface design, the control group only physically adheres between layers and is prone to delamination and cracking due to radiation stress.

[0070] In summary, the present invention forms a full-process protection system of "ray shielding-free radical scavenging-stress buffering" through a three-layer composite structure design of a high-energy ray attenuation outer layer, a free radical dynamic capture middle layer and a stress buffering inner layer, combined with an interpenetrating network cross-linking, antioxidant gradient diffusion and nano-anchor reinforcement cross-layer synergistic mechanism; compared with the existing technology, this material has a 10 5 After Gy irradiation, the strength retention rate is increased by more than 30%, and the interface bonding strength is increased by 69%-89%, thereby improving the long-term stability and reliability of high-performance cables in strong radiation environments.

[0071] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A radiation-resistant silicone rubber for high-performance cables, characterized in that: It includes a high-energy ray attenuation outer layer, a free radical dynamic capture middle layer and a stress buffer bonding inner layer: The high-energy ray attenuation outer layer comprises at least nano-titanium dioxide, cadmium tungstate, phenyl silicone rubber and silane coupling agent KH-570. Nano-titanium dioxide scatters rays below 50keV, and cadmium tungstate absorbs rays above 50keV, forming a barrier with complementary energy bands. Phenyl silicone rubber disperses energy through a conjugated structure, and the silane coupling agent KH-570 can enhance interfacial bonding, thereby jointly constructing a multi-level ray attenuation network. The free radical dynamic capture intermediate layer comprises at least a primary antioxidant, a secondary antioxidant, vinyl silicone rubber and carbon nanotubes, wherein the vinyl silicone rubber contains a crosslinking agent to form a low crosslinking density network to construct a free radical diffusion channel; The stress buffer bonding inner layer comprises at least fumed silica, a flexible toughening agent, vinyl silicone rubber of the same material as the cable matrix, and a silane coupling agent KH-590. The fumed silica forms chemical anchor points through condensation of surface silanol groups with methoxy groups of the silane coupling agent KH-590, and the primary particles are entangled into a nano-network structure through hydrogen bonds. The high-energy ray attenuation outer layer phenyl silicone rubber and the free radical dynamic capture middle layer vinyl silicone rubber are cross-linked to form a "phenyl-vinyl chain segment" interpenetrating network. The antioxidant in the free radical dynamic capture middle layer diffuses into the high-energy ray attenuation outer layer to form an enrichment layer to inhibit oxidation. While stress buffering is combined with the migration of the inner layer flexible chain segments, fumed silica diffuses into the free radical dynamic capture middle layer to form a 20-30nm "nano-anchor" structure.

2. The radiation-resistant silicone rubber for high-performance cables according to claim 1, characterized in that: The amount of the nano titanium dioxide is 30-40 parts, and its particle size is 20-40nm; the amount of the cadmium tungstate is 25-30 parts; the amount of the phenyl silicone rubber is 20-25 parts, and its phenyl content is 20%-25%; the amount of the silane coupling agent KH-570 is 1-2 parts; The dosage of the primary antioxidant is 10-15 parts; the dosage of the secondary antioxidant is 4-6 parts; The amount of the vinyl silicone rubber is 65-70 parts; the amount of the crosslinking agent is 0.5-0.7 parts; the amount of the carbon nanotube is 3-5 parts, and its diameter is less than 5nm; The amount of the fumed silica is 22-28 parts, and its particle size is 8-12 nm; the amount of the flexible toughening agent is 12-18 parts, and its molecular weight is 50,000-80,000; the amount of the cable matrix vinyl silicone rubber is 55-60 parts; and the amount of the silane coupling agent KH-590 is 1-2 parts.

3. The radiation-resistant silicone rubber for high-performance cables according to claim 1, characterized in that: The main antioxidant is a hindered phenol antioxidant, and the secondary antioxidant is dilauryl thiodipropionate. The hindered phenol antioxidant quenches irradiated primary free radicals through phenolic hydroxyl hydrogen atom transfer, and the dilauryl thiodipropionate decomposes peroxides with the help of thioether groups, forming a cyclic action mechanism with the hindered phenol antioxidant.

4. The radiation-resistant silicone rubber for high-performance cables according to claim 1, characterized in that: The flexible toughening agent is polydimethylsiloxane, and the linear chains of polydimethylsiloxane are interspersed in the vinyl silicone rubber network to form a "rigid and flexible" structure to absorb stress, and its low molecular weight chain segments diffuse to form a 10-20μm transition layer.

5. The radiation-resistant silicone rubber for high-performance cables according to claim 1, characterized in that: The following steps are also included for preparing silicone rubber: S1. Preparation of high-energy ray attenuating outer layer slurry: pre-plasticize phenyl silicone rubber, then add nano titanium dioxide, cadmium tungstate and alkane coupling agent KH-570 into a high-speed disperser and stir to condense the filler and coupling agent, then add the pre-plasticized phenyl silicone rubber and continue stirring to form a high-energy ray attenuating outer layer slurry; S2. Dynamic capture of free radicals and mixing of the intermediate rubber layer: First, the vinyl silicone rubber is put into a two-roll mill for plasticization and coating, and then the primary antioxidant and the secondary antioxidant are mixed and dispersed; carbon nanotubes are added by a staged feeding method, and then a cross-linking agent is added and mixed until there are no particles larger than 50 μm. After microscopic inspection, the sheet is removed and left to stand, forming an intermediate rubber layer with a gel content of 45%-50% and a low cross-linking density; S3. Co-vulcanization pretreatment of stress buffering and inner layer rubber compound: First, the cable matrix and vinyl silicone rubber and flexible toughening agent are put into a planetary mixer for stirring, and then fumed silica and silane coupling agent KH-590 are added and kneaded to form a stress buffering and inner layer rubber compound; S4. Three-layer co-extrusion coating and gradient cross-linking: A three-layer co-extrusion device is used to apply the high-energy ray attenuating outer layer slurry to the surface of the cable base structure through a screw extruder to form a shielding layer. The middle layer rubber is then covered on the outer layer by a gravure roller coater to form a transitional cross-linking zone. Finally, a hot pressing laminating device is used to simultaneously vulcanize the stress buffering inner layer rubber and the cable base structure to form a gradient cross-linking structure of "shielding layer-capturing layer-buffer layer"; S5. Post-electron beam irradiation treatment and performance optimization: The coated cable is sent to the electron beam irradiation room and irradiated with a cumulative dose of 15-20 kGy at a dose rate of 5-10 kGy / h at room temperature. The cable is then placed in an environment of 70-75°C for 24 hours of aging treatment to finally produce a radiation-resistant silicone rubber cable material.

6. The radiation-resistant silicone rubber for high-performance cables according to claim 5, characterized in that: In the S1, the pre-plasticization treatment step is as follows: the phenyl silicone rubber is put into a two-roll open mill, and under the conditions of a roller temperature of 100-110°C and a roller distance of 1-2mm, the rubber is first thin-passed 2-3 times to soften the rubber material and wrap the rollers, and then the roller distance is adjusted to 0.5-1mm for thin-passing operation, and a total of 8-10 thin-passing operations are performed throughout the whole process. After each thin-passing, a triangle bag is formed and the rubber is re-mixed to homogenize the molecular weight distribution and activate the vinyl activity in the molecular chain.

7. The radiation-resistant silicone rubber for high-performance cables according to claim 5, characterized in that: In S1, nano-titanium dioxide, cadmium tungstate and alkane coupling agent KH-570 are stirred in a high-speed disperser at 75-85°C and 1800-2200 r / min for 30-40 minutes; after adding phenyl silicone rubber, stirring is continued in the high-speed disperser for 1-1.5 hours, during which time 35-45kHz, 450-550W ultrasonic waves are used to assist dispersion, and the mixture is cyclically ground on a three-roll mill for 3-4 times until the dispersion degree is ≥95% and the viscosity is 5000-8000 mPa·s.

8. The radiation-resistant silicone rubber for high-performance cables according to claim 5, characterized in that: In the S2, the vinyl silicone rubber is plasticized by passing it through a two-roll mill for 5-8 times at a roller temperature of 55-65° C. and a roller gap of 0.5-0.8 mm; the main antioxidant and the auxiliary antioxidant are mixed for 10-15 minutes at a roller gap of 2-3 mm on the two-roll mill; the carbon nanotubes are added in small amounts in 2-3 times by the staged feeding method, and after each addition, they are dispersed by strong shearing and thinning with a roller gap of 0.3-0.5 mm; the crosslinking agent is mixed for 8-12 minutes at a roller gap of 3-4 mm on the two-roll mill; and the mixing is carried out for 24 hours in an environment of 23±2° C. and a relative humidity of 50±5%.

9. The radiation-resistant silicone rubber for high-performance cables according to claim 5, characterized in that: In S3, the planetary mixer stirs the cable substrate, vinyl silicone rubber and flexible toughening agent at a speed of 150-180 r / min under a vacuum environment at 90-100° C. for 50-60 minutes; the planetary mixer kneads the fumed silica and silane coupling agent KH-590 at a temperature of 110-120° C. and a pressure of 0.4-0.6 MPa for 2-2.5 hours.

10. The radiation-resistant silicone rubber for high-performance cables according to claim 5, characterized in that: In the S4, the screw length-diameter ratio of the three-layer co-extrusion equipment is 28:1; the screw extruder is used to apply the high-energy ray attenuating outer layer slurry to the surface of the cable infrastructure at a temperature of 110-130°C and a line speed of 0.5-1.0 m / min, and the thickness of the shielding layer is 80-120 μm; the gravure roller coater is used to cover the middle layer rubber with an anilox roller line count of 200-300 lines / inch, and the covering thickness is 40-60 μm; the hot pressing laminating device is used for synchronous vulcanization for 30-45 minutes at a pressure of 1.2-1.5 MPa and a temperature of 150-160°C.

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