Rubber and preparation method thereof, fully-coated rubber O-shaped ring and preparation method and application of fully-coated rubber O-shaped ring

Abstract

The invention relates to the technical field of sealing elements, in particular to rubber, a preparation method of the rubber, a fully-coated rubber O-shaped ring and a preparation method and application of the fully-coated rubber O-shaped ring. The rubber provided by the invention is prepared from the following raw materials in parts by mass: 100 parts of ethylene propylene diene monomer, 30-50 parts of a reinforcing agent, 5-10 parts of a plasticizer, 1-2 parts of an antioxidant, 1-2 parts of a stabilizer, 0.8-1.2 parts of a vulcanizing agent, 0.5-1 part of an accelerant, 3-5 parts of zinc oxide, 1-1.5 parts of stearic acid, 3-6 parts of a special modification additive, 2-5 parts of a preservative and 3-5 parts of a phosphate flame retardant, the content of vinyl in the ethylene propylene diene monomer is 55 wt%-65 wt%; the vulcanizing agent comprises a bis (dithiourea) vulcanizing agent and / or zinc diethyl dithiocarbamate; the accelerant comprises tetramethyl thiuram disulfide and / or N-cyclohexyl-2-benzothiazole sulfonamide, and the accelerant comprises tetramethyl thiuram disulfide and / or N-cyclohexyl-2-benzothiazole sulfonamide. The rubber has excellent corrosion resistance against special liquid oxidants (e.g., HAP).

Description

Technical Field

[0001] The present invention relates to the technical field of seals, and particularly to a rubber and a preparation method thereof, a fully encapsulated rubber O-ring and a preparation method and application thereof. Background Art

[0002] Underwater special engines use special liquid oxidants as reactive fuels, which can overcome the disadvantages faced by traditional fuel systems such as oxygen deficiency, incomplete combustion, and low energy and specific impulse. It is the development trend of future high-performance underwater propulsion systems. However, at present, hydroxylammonium perchlorate (HAP), as a special liquid oxidant, has strong chemical corrosiveness and flammability, and has a chemical corrosive effect on traditional sealing materials such as nitrile rubber and fluororubber, and cannot ensure the storage safety of fuel during long-term static storage. In addition, the seals immersed in HAP liquid for a long time will be corroded, which will seriously affect the low friction and low damping performance of the seals during the transportation process, and even lead to seal failure, unstable fuel supply and leakage, affecting the working stability of the pressurization system and the combustion system, thus causing fluctuations in the power efficiency of the engine and seriously affecting the operation reliability and safety of the propulsion system.

[0003] The rubber O-ring is the most widely used seal, with a simple structure, convenient use and good sealing effect. However, when sealing the above special liquid oxidant, due to the corrosive effect of the special liquid oxidant, the rubber O-ring ages, and it is easy to lose its elastic compensation function in a short time, or after the rubber material ages, it is easy to be sheared and broken under the action of the sealing medium pressure, resulting in seal leakage. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a rubber and a preparation method thereof, a fully encapsulated rubber O-ring and a preparation method and application thereof, and the rubber has excellent corrosion resistance to special liquid oxidants (such as HAP).

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a rubber, which comprises the following preparation raw materials by mass parts: 100 parts of ethylene propylene diene monomer (EPDM) rubber, 30 - 50 parts of reinforcing agent, 5 - 10 parts of plasticizer, 1 - 2 parts of antioxidant, 1 - 2 parts of stabilizer, 0.8 - 1.2 parts of vulcanizing agent, 0.5 - 1 part of accelerator, 3 - 5 parts of zinc oxide, 1 - 1.5 parts of stearic acid, 3 - 6 parts of special modification additive, 2 - 5 parts of preservative and 3 - 5 parts of phosphate flame retardant; the vinyl content in the EPDM rubber is 55wt% - 65wt%; the vulcanizing agent comprises bis(dithiocarbamate) vulcanizing agent and / or zinc diethyldithiocarbamate; the accelerator comprises tetramethylthiuram disulfide and / or N-cyclohexyl-2-benzothiazolesulfenamide.

[0007] Preferably, the reinforcing agent comprises silica and / or perfluoropolyether oil;

[0008] The plasticizer comprises fluorosilicone oil and / or perfluoropolyether oil;

[0009] The model of the antioxidant comprises one or several of 4010NA, Irganox 1010 and Irganox 1076;

[0010] The stabilizer comprises antiozonant and / or hindered amine light stabilizer;

[0011] The special modification additive comprises fluorinated graphite and / or fluorinated graphene;

[0012] The preservative comprises microcrystalline wax and / or low molecular weight polyethylene wax, and the molecular weight of the low molecular weight polyethylene wax is 1000 - 5000 g / mol;

[0013] The phosphate flame retardant comprises triphenyl phosphate and / or resorcinol bis(diphenyl phosphate).

[0014] The present invention also provides a preparation method of the rubber according to the above technical solution, which comprises the following steps:

[0015] After adding the reinforcing agent, plasticizer, stearic acid and preservative into the EPDM rubber in a plasticized state in sequence, add the antioxidant, stabilizer, special modification additive and phosphate flame retardant, and finally add the vulcanizing agent, accelerator and zinc oxide, and carry out mixing to obtain a rubber compound;

[0016] Carry out open mill processing, vulcanization molding and aging treatment on the rubber compound in sequence to obtain the rubber.

[0017] Preferably, the temperature of the mixing is 50 - 70°C and the time is 6 - 8 min;

[0018] The pressure of the compression molding vulcanization is 10 - 20 MPa, the temperature is 160 - 180°C, and the time is 2 - 15 min;

[0019] The temperature of the aging treatment is 80-100 °C, and the time is 4-6 h.

[0020] The present invention also provides a fully encapsulated rubber O-ring, which includes an inner core rubber strip and a coating tube with heat shrinkage characteristics;

[0021] The inner core rubber strip is the rubber described in the above technical solution or the rubber prepared by the preparation method described in the above technical solution;

[0022] The material of the coating tube with heat shrinkage characteristics is fluorinated ethylene propylene copolymer.

[0023] Preferably, the preparation method of the coating tube with heat shrinkage characteristics includes the following steps:

[0024] After heating the coating tube made of fluorinated ethylene propylene copolymer, radially expanding the coating tube, and then successively performing cooling and setting and annealing treatments to obtain the coating tube with heat shrinkage characteristics;

[0025] The temperature of the heating is greater than the glass transition temperature and less than the melting temperature.

[0026] The present invention also provides a preparation method of the fully encapsulated rubber O-ring described in the above technical solution, which includes the following steps:

[0027] Insert the inner core rubber strip into the coating tube with heat shrinkage characteristics, and make one end of the coating tube with heat shrinkage characteristics expose the inner core rubber strip, denoted as end A; the other end does not expose the inner core rubber strip and has a cavity, denoted as end B; the lengths of the inner core rubber strip and the coating tube with heat shrinkage characteristics are equal;

[0028] After inserting a cylindrical stainless steel iron core with a wire diameter larger than the outer diameter of the inner core rubber strip into the cavity at end B for occupying the position, successively perform heat shrinkage and cooling and setting, and remove the cylindrical stainless steel iron core to obtain a misaligned coated rubber strip assembly;

[0029] Insert the inner core rubber strip exposed at end A in the misaligned coated rubber strip assembly into the cavity at end B of the misaligned coated rubber strip assembly, and bond the side faces at both ends of the inner core rubber strip after insertion, and form a closed ring body, and then successively perform circumferential seam butt welding and curing heat treatment to obtain the fully encapsulated rubber O-ring.

[0030] Preferably, the difference between the wire diameter of the cylindrical stainless steel iron core and the outer diameter of the inner core rubber strip is 0.1-0.3 mm;

[0031] The temperature of the heat shrinkage is 200-240 °C, and the time is 2-15 min.

[0032] Preferably, before the butt joint, apply neutral lubricant on the outer side of the inner core rubber strip at end A, and apply adhesive on the end face of the inner core rubber strip at end B;

[0033] The temperature of the circumferential seam butt welding is 280 - 300 °C, and the time is 10 - 50 s;

[0034] During the circumferential seam welding, use a quartz glass tube to sleeve the circumferential seam butt welding area to flatten the weld seam;

[0035] The temperature of the curing heat treatment is 180 - 200 °C, and the time is 10 - 24 h.

[0036] The present invention also provides the application of the fully - covered rubber O - ring described in the above technical solution or the fully - covered rubber O - ring prepared by the preparation method described in the above technical solution in the field of sealing against corrosion by special liquid oxidants.

[0037] The present invention provides a rubber. By mass, the inner core rubber strip comprises the following preparation raw materials: 100 parts of ethylene - propylene - diene monomer rubber, 30 - 50 parts of reinforcing agent, 5 - 10 parts of plasticizer, 1 - 2 parts of antioxidant, 1 - 2 parts of stabilizer, 0.8 - 1.2 parts of vulcanizing agent, 0.5 - 1 part of accelerator, 3 - 5 parts of zinc oxide, 1 - 1.5 parts of stearic acid, 3 - 6 parts of special modification additive, 2 - 5 parts of preservative, and 3 - 5 parts of phosphate flame retardant; the vinyl content in the ethylene - propylene - diene monomer rubber is 55 wt% - 65 wt%; the vulcanizing agent comprises bis - dithiocarbamate vulcanizing agent and / or zinc diethyldithiocarbamate; the accelerator comprises tetramethylthiuram disulfide and / or N - cyclohexyl - 2 - benzothiazolesulfonamide. The combination of the above - mentioned vulcanizing agent and accelerator used in the present invention can form a more stable cross - linked structure for the ethylene - propylene - diene monomer rubber with the above - mentioned vinyl content, thereby effectively reducing the risk of damage to the cross - linked network by special liquid oxidant (such as HAP) medium, and further enabling the rubber provided by the present invention to have the characteristic of strong corrosion resistance to special liquid oxidant (such as HAP) medium.

[0038] The present invention also provides a fully - covered rubber O - ring, which comprises an inner core rubber strip and a covering tube with heat - shrinkage characteristics; the inner core rubber strip is the rubber described in the above technical solution or the rubber prepared by the preparation method described in the above technical solution; the material of the covering tube with heat - shrinkage characteristics is fluorinated ethylene - propylene copolymer. The use of the covering tube with heat - shrinkage characteristics in the present invention can make the covering layer of the prepared fully - covered rubber O - ring heat - shrink and tightly wrap the inner core rubber strip, which can greatly increase the combination of the covering tube and the inner core rubber strip, improve the effectiveness of load transfer, effectively transfer the elastic force of the inner core rubber strip, improve the elastic compensation ability of the fully - covered rubber O - ring, prevent the covering tube from squeezing into the sealing gap and damaging after the fully - covered rubber O - ring is compressed, and improve the sealing reliability.

[0039] The present invention also provides a method for preparing the fully encapsulated rubber O-ring described in the above technical solution, including the following steps: threading the inner core rubber strip into the encapsulation tube with heat shrinkage characteristics, and exposing one end of the encapsulation tube with heat shrinkage characteristics to the inner core rubber strip, denoted as end A; the other end does not expose the inner core rubber strip and has a cavity, denoted as end B; the lengths of the inner core rubber strip and the encapsulation tube with heat shrinkage characteristics are equal; after inserting a cylindrical stainless steel iron core with a wire diameter larger than the outer diameter of the inner core rubber strip into the cavity at end B for occupying the position, heat shrinkage and cooling and shaping are carried out in sequence, and the cylindrical stainless steel iron core is removed to obtain a rubber strip assembly with misaligned encapsulation; the inner core rubber strip exposed at end A in the rubber strip assembly with misaligned encapsulation is inserted into the cavity at end B of the rubber strip assembly with misaligned encapsulation, and the side faces at both ends of the inner core rubber strip after insertion are adhesively bonded to form a closed ring body, and then circumferential seam butt welding and curing heat treatment are carried out in sequence to obtain the fully encapsulated rubber O-ring. The preparation method of the present invention improves the butt joint strength of the interface by combining misaligned encapsulation and butt joint adhesion, so as to ensure that the fully encapsulated rubber O-ring does not break during installation and service, and improves reliability. The fully encapsulated rubber O-ring prepared by using the preparation method has high protection reliability against strong corrosion of special liquid oxidants (such as HAP). BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic structural diagram of the inner core rubber strip, the encapsulation tube made of fluorinated ethylene propylene copolymer and the encapsulation tube with heat shrinkage characteristics described in the present application;

[0041] Figure 2 is a schematic structural diagram before heat shrinkage in the preparation method of the present invention;

[0042] Figure 3 is a schematic structural diagram after the rubber strip assembly with misaligned encapsulation is inserted into a thin-walled quartz tube in the present invention;

[0043] Figure 4 is a partial enlarged view of the interface at the insertion position in the preparation method of the present invention;

[0044] Figure 5 is a partial enlarged view of the interface of circumferential seam butt welding in the preparation method of the present invention;

[0045] Figure 6 is a partial enlarged view of the cross section of the fully encapsulated rubber O-ring and the interface thereof in the present invention;

[0046] Figure 7 is the change of tensile strength parameters of the inner core rubber strip of the fully encapsulated rubber O-ring described in Examples 1 to 3 under HAP corrosion and aging;

[0047] Figure 8 To implement the change in the elongation at break parameter of the inner core rubber strip of the fully encapsulated rubber O-ring described in Examples 1 to 3 under HAP corrosion aging;

[0048] Figure 9 To implement the change in the compression set parameter of the inner core rubber strip of the fully encapsulated rubber O-ring described in Examples 1 to 3 under HAP corrosion aging;

[0049] Among them, 1 is the structural schematic diagram of the inner core rubber strip, 2 is the structural schematic diagram of the coating tube made of fluorinated ethylene propylene copolymer, 21 is the coating tube with heat shrinkage characteristics before heat shrinkage, 3 is the cylindrical stainless steel iron core, 4 is the thin-walled quartz tube, 5 is the cavity formed after removing the cylindrical stainless steel iron core, 22 is the heat-shrunk coating tube coated on the inner core rubber strip, 6 is the adhesive coated on the end face of the inner core rubber strip, and 7 is the bonding interface. Detailed implementation mode

[0050] The present invention provides a rubber, which, by mass parts, comprises the following preparation raw materials: 100 parts of ethylene propylene diene monomer rubber, 30 - 50 parts of reinforcing agent, 5 - 10 parts of plasticizer, 1 - 2 parts of antioxidant, 1 - 2 parts of stabilizer, 0.8 - 1.2 parts of vulcanizing agent, 0.5 - 1 part of accelerator, 3 - 5 parts of zinc oxide, 1 - 1.5 parts of stearic acid, 3 - 6 parts of special modification auxiliary agent, 2 - 5 parts of preservative and 3 - 5 parts of phosphate flame retardant; the vinyl content in the ethylene propylene diene monomer rubber is 55wt% - 65wt%; the vulcanizing agent comprises bis(dithiocarbamate) vulcanizing agent and / or zinc diethyldithiocarbamate; the accelerator comprises tetramethylthiuram disulfide and / or N-cyclohexyl-2-benzothiazolesulfonamide.

[0051] By mass parts, the preparation raw materials of the rubber of the present invention comprise 100 parts of ethylene propylene diene monomer rubber (EPDM). In the present invention, the vinyl content in the ethylene propylene diene monomer rubber is 55% - 65%. In the embodiments of the present invention, the vinyl content in the ethylene propylene diene monomer rubber can be 65%, 60% or 55%.

[0052] In the present invention, controlling the vinyl content in the ethylene propylene diene monomer (EPDM) within the above range can make the molecular structure of the EPDM more saturated, reduce the proportion of unsaturated bonds, and decrease the sites that are easily oxidized or attacked, thereby improving the stability of the material in a strongly oxidizing environment (such as a special liquid oxidant medium like HAP). At the same time, it helps to resist the erosion of strongly corrosive chemical substances and extend the service life of the rubber in a harsh environment. In addition, the EPDM within the above vinyl content range has better thermal stability and mechanical properties. However, too high an ethylene content (greater than 65%) will make the EPDM brittle and reduce its flexibility; too low a vinyl content (less than 55%) will reduce the chemical resistance of the EPDM and deteriorate its corrosion resistance in a strongly oxidizing environment (such as a special liquid oxidant medium like HAP).

[0053] Based on the mass parts of the ethylene propylene diene monomer (EPDM), the preparation raw materials of the rubber in the present invention further include 30 - 50 parts of a reinforcing agent, more preferably 35 - 45 parts. In the embodiments of the present invention, the mass parts of the reinforcing agent in the preparation raw materials of the rubber can be 30 parts, 35 parts, or 45 parts.

[0054] In the present invention, the reinforcing agent preferably includes silica and / or nano-silicon. When the reinforcing agent is silica and nano-silicon, the present invention has no special limitation on the ratio of the silica and nano-silicon, and they can be mixed in any ratio. In the embodiments of the present invention, the reinforcing agent can be silica or nano-silicon.

[0055] In the present invention, the reinforcing agent can improve the mechanical properties of the rubber, reduce permeability and chemical reactivity, and thus improve its chemical corrosion resistance.

[0056] Based on the mass parts of the ethylene propylene diene monomer (EPDM), the preparation raw materials of the rubber in the present invention further include 5 - 10 parts of a plasticizer, preferably 6 - 8 parts. In the embodiments of the present invention, the mass parts of the plasticizer in the preparation raw materials of the rubber can be 10 parts or 8 parts.

[0057] In the present invention, the plasticizer preferably includes fluorosilicone oil and / or perfluoropolyether oil. When the plasticizer is fluorosilicone oil and perfluoropolyether oil, the present invention has no special limitation on the ratio of the fluorosilicone oil and perfluoropolyether oil, and they can be mixed in any ratio. In the embodiments of the present invention, the plasticizer can be fluorosilicone oil or perfluoropolyether oil.

[0058] In the present invention, both fluorosilicone oil and perfluoropolyether oil have low polarity and high chemical stability, and can maintain the flexibility and oxidation resistance of the rubber in a special liquid oxidant (such as HAP) medium.

[0059] Based on the parts by mass of the ethylene-propylene-diene monomer rubber, the raw materials for preparing the rubber of the present invention further include 1 to 2 parts of an antioxidant, preferably 1.3 to 1.7 parts. In the embodiments of the present invention, the parts by mass of the antioxidant in the raw materials for preparing the rubber can be 1 part or 1.2 parts.

[0060] In the present invention, the types of the antioxidant preferably include one or more of 4010NA, Irganox 1010, and Irganox 1076. When there are two or more of the above specific selections for the antioxidant, the present invention has no special limitation on the ratio of the above specific substances, and they can be mixed in any ratio. In the embodiments of the present invention, the types of the antioxidant can be 4010NA, Irganox 1010, or Irganox 1076.

[0061] In the present invention, the antioxidants of the above types can effectively inhibit free radical reactions and prevent the erosion of the rubber by oxidizing substances generated by the decomposition of special liquid oxidants (such as HAP) media.

[0062] Based on the parts by mass of the ethylene-propylene-diene monomer rubber, the raw materials for preparing the rubber of the present invention further include 1 to 2 parts of a stabilizer. In the embodiments of the present invention, the parts by mass of the stabilizer in the raw materials for preparing the rubber can be 2 parts.

[0063] In the present invention, the stabilizer preferably includes an anti-ozone agent and / or a hindered amine light stabilizer; the type of the anti-ozone agent is preferably 4020, and the type of the hindered amine light stabilizer is preferably Chimassorb 944. When the stabilizer is an anti-ozone agent and a hindered amine light stabilizer, the present invention has no special limitation on the ratio of the anti-ozone agent and the hindered amine light stabilizer, and they can be mixed in any ratio. In the embodiments of the present invention, it is 4020 or Chimassorb 944.

[0064] In the present invention, the stabilizer can improve the anti-ozone property of the rubber, prevent cracks and aging, especially the performance retention during long-term exposure to oxidants. At the same time, when the stabilizer includes a hindered amine light stabilizer, in addition to improving the anti-ozone performance to a certain extent, it can also capture free radicals through the hindered amine structure, thereby delaying the degradation of the rubber caused by ultraviolet light irradiation.

[0065] Based on the parts by mass of the ethylene-propylene-diene monomer rubber, the raw materials for preparing the rubber of the present invention further include 0.8 to 1.2 parts of a vulcanizing agent, preferably 0.9 to 1.1 parts. In the embodiments of the present invention, the parts by mass of the vulcanizing agent in the raw materials for preparing the rubber can be 1 part or 1.1 parts.

[0066] In the present invention, the vulcanizing agent includes bis(dithiocarbamoyl)disulfide (DTDM) and / or zinc diethyldithiocarbamate (ZnDDC). When the vulcanizing agent includes bis(dithiocarbamoyl)disulfide and zinc diethyldithiocarbamate, the present invention does not have any special limitation on the ratio of bis(dithiocarbamoyl)disulfide and zinc diethyldithiocarbamate, and they can be mixed in any ratio. In the embodiments of the present invention, the vulcanizing agent can be bis(dithiocarbamoyl)disulfide or zinc diethyldithiocarbamate.

[0067] In the present invention, the vulcanizing agent can enable the final rubber to form a stable vulcanization network. In a special liquid oxidant (such as HAP) medium, its antioxidant capacity and protective effect on the crosslinked structure are excellent, and the oxidation resistance is improved.

[0068] Based on the mass parts of the ethylene-propylene-diene monomer rubber, the preparation raw materials of the rubber in the present invention further include 0.5 to 1 part of an accelerator. In the embodiments of the present invention, the weight part of the accelerator in the preparation raw materials of the rubber can be 1 part.

[0069] In the present invention, the accelerator includes tetramethylthiuram disulfide (TMTD) and / or N-cyclohexyl-2-benzothiazolesulfonamide (CBS). When the accelerator includes tetramethylthiuram disulfide and N-cyclohexyl-2-benzothiazolesulfonamide, the present invention does not have any special limitation on the ratio of tetramethylthiuram disulfide and N-cyclohexyl-2-benzothiazolesulfonamide, and they can be mixed in any ratio. In the embodiments of the present invention, the accelerator can be tetramethylthiuram disulfide (TMTD) or N-cyclohexyl-2-benzothiazolesulfonamide (CBS).

[0070] The above-mentioned vulcanizing agent and accelerator used in combination in the present invention can enable the ethylene-propylene-diene monomer rubber with the above vinyl content to form a more stable crosslinked structure, thereby effectively reducing the risk of damage to the crosslinked network by a special liquid oxidant (such as HAP) medium.

[0071] Based on the mass parts of the ethylene-propylene-diene monomer rubber, the preparation raw materials of the rubber in the present invention further include 3 to 5 parts of zinc oxide, more preferably 3.5 to 5 parts. In the embodiments of the present invention, the mass parts of zinc oxide in the preparation raw materials of the rubber can be 3.5 parts, 4 parts or 5 parts.

[0072] In the present invention, the zinc oxide, as a vulcanization activator, can simultaneously improve the oxidation resistance and corrosion resistance of the rubber.

[0073] Based on the parts by mass of the ethylene-propylene-diene monomer rubber, the preparation raw materials of the rubber of the present invention further include 1 to 1.5 parts of stearic acid, more preferably 1.2 to 1.4 parts. In the embodiments of the present invention, the weight parts of stearic acid in the preparation raw materials of the rubber can be 1.5 parts, 1 part or 1.2 parts.

[0074] In the present invention, the stearic acid plays a role in enhancing lubrication and filler dispersion, and can improve the processing performance of the rubber.

[0075] Based on the parts by mass of the ethylene-propylene-diene monomer rubber, the preparation raw materials of the rubber of the present invention further include 3 to 6 parts of a special modification agent, preferably 3.5 to 5.5 parts. In the embodiments of the present invention, the weight parts of the special modification agent in the preparation raw materials of the rubber can be 4 parts or 5 parts.

[0076] In the present invention, the special modification agent preferably includes graphite fluoride (GF) and / or graphene fluoride. When the special modification agent is graphite fluoride and graphene fluoride, the present invention does not have any special limitation on the ratio of the graphite fluoride and graphene fluoride, and they can be mixed in any ratio. In the specific embodiments of the present invention, the special modification agent can be graphite fluoride or graphene fluoride.

[0077] In the present invention, both the graphite fluoride and graphene fluoride have excellent chemical inertness and high-temperature resistance. Adding them to the ethylene-propylene-diene monomer rubber can make the finally prepared rubber have excellent oxidation resistance, chemical resistance and heat resistance, and can prevent the erosion of the rubber matrix in the rubber by the special liquid oxidant (such as HAP) medium.

[0078] Based on the parts by mass of the ethylene-propylene-diene monomer rubber, the preparation raw materials of the rubber of the present invention further include 2 to 5 parts of a preservative, preferably 2.5 to 5 parts. In the embodiments of the present invention, the weight parts of the preservative in the preparation raw materials of the rubber can be 3 parts, 4 parts or 5 parts.

[0079] In the present invention, the preservative preferably includes microcrystalline wax and / or low molecular weight polyethylene wax (PE Wax), and the molecular weight of the low molecular weight polyethylene wax is preferably 1000 to 5000 g / mol. In the embodiments of the present invention, the preservative can be microcrystalline wax or low molecular weight polyethylene wax.

[0080] In the present invention, both the microcrystalline wax and low molecular weight polyethylene wax have relatively high melting points and excellent fluidity, can improve the surface smoothness and anti-permeability of the rubber, and at the same time provide a barrier effect in protecting against the erosion of the special liquid oxidant (such as HAP).

[0081] Based on the parts by mass of the ethylene-propylene-diene monomer rubber, the raw materials for preparing the rubber of the present invention further include 3 to 5 parts of a phosphate flame retardant, preferably 3.5 to 5 parts. In the examples of the present invention, the weight parts of the phosphate flame retardant in the raw materials for preparing the rubber can be 4 parts or 5 parts.

[0082] In the present invention, the phosphate flame retardant preferably includes triphenyl phosphate (TPP) and / or resorcinol bis(diphenyl phosphate) (RDP). When the phosphate flame retardant is TPP and RDP, the present invention has no special limitation on the ratio of TPP and RDP, and they can be mixed in any ratio. In the examples of the present invention, the phosphate flame retardant can be triphenyl phosphate (TPP) or resorcinol bis(diphenyl phosphate) (RDP).

[0083] In the present invention, the phosphate flame retardant not only has good flame retardant effect, but also can provide synergistic protection in high temperature and strong oxidation environment.

[0084] The present invention also provides a method for preparing the rubber according to the above technical solution, including the following steps:

[0085] After adding a reinforcing agent, a plasticizer, stearic acid and a preservative to the ethylene-propylene-diene monomer rubber in a plasticized state, an antioxidant, a stabilizer, a special modification aid and a phosphate flame retardant are added, and finally a vulcanizing agent, an accelerator and zinc oxide are added, and mixing is carried out to obtain a rubber compound;

[0086] The rubber compound is successively subjected to open mill processing, vulcanization molding and aging treatment to obtain the rubber (such as Figure 1 the structural schematic diagram shown by the reference numeral 1 in the drawings).

[0087] In the present invention, after adding a reinforcing agent, a plasticizer, stearic acid and a preservative to the ethylene-propylene-diene monomer rubber in a plasticized state, an antioxidant, a stabilizer, a special modification aid and a phosphate flame retardant are added, and finally a vulcanizing agent, an accelerator and zinc oxide are added, and mixing is carried out to obtain a rubber compound.

[0088] In the present invention, the method for preparing the ethylene-propylene-diene monomer rubber in a plasticized state is preferably to carry out internal mixing of the ethylene-propylene-diene monomer rubber in an internal mixer to obtain the ethylene-propylene-diene monomer rubber in a plasticized state. The present invention has no special limitation on the internal mixing process, and a process well-known to those skilled in the art can be adopted as long as the ethylene-propylene-diene monomer rubber is in a plasticized state.

[0089] The present invention has no special limitation on the addition method of the reinforcing agent, the plasticizer, stearic acid and the preservative, and a method well-known to those skilled in the art can be adopted to ensure that the reinforcing agent, the plasticizer, stearic acid and the preservative are uniformly dispersed in the ethylene-propylene-diene monomer rubber.

[0090] The present invention has no special limitation on the addition sequence and addition method of the antioxidant, stabilizer, special modification aid, and phosphate flame retardant, and the addition sequence and addition method well-known to those skilled in the art can be adopted.

[0091] The present invention has no special limitation on the addition sequence and addition method of the vulcanizing agent and accelerator, and the addition sequence and addition method well-known to those skilled in the art can be adopted.

[0092] In the present invention, the mixing sequence for preparing the above-mentioned rubber compound can avoid unnecessary interaction between the filler and the additives during the mixing process.

[0093] In the present invention, the temperature of the mixing is preferably 50-70°C, more preferably 55-65°C; the time is preferably 6-8 minutes, more preferably 6.5-7.5 minutes. In the examples of the present invention, the temperature of the mixing can be 60°C, 62°C or 70°C, and the time can be 8 minutes or 7 minutes.

[0094] In the present invention, the above-mentioned mixing conditions can avoid the decomposition of the vulcanizing agent due to overheating during the mixing process.

[0095] To obtain the rubber compound, the present invention successively subjects the rubber compound to open mill processing, vulcanization molding, and aging treatment to obtain the rubber.

[0096] In the present invention, the process of the open mill processing is preferably to transfer the rubber compound to an open mill for processing and sheet making; the present invention has no special limitation on the processes of the processing and sheet making, and the processes well-known to those skilled in the art can be adopted to make the thickness of the sheet obtained after sheet making within the range of 3-5 mm and ensure that the components in the rubber compound are uniformly mixed.

[0097] In the present invention, the vulcanization molding method is preferably compression molding vulcanization or extrusion molding.

[0098] In the present invention, the pressure of the compression molding vulcanization is preferably 10-20 MPa, more preferably 13-16 MPa; the temperature is preferably 160-180°C, more preferably 165-175°C; the time is preferably 2-15 minutes, more preferably 5-10 minutes. In the examples of the present invention, the pressure of the compression molding vulcanization can be 18 MPa, 16 MPa or 15 MPa, the temperature can be 175°C, 165°C or 162°C, and the time can be 10 minutes, 8 minutes or 15 minutes. In the present invention, the compression molding vulcanization is preferably carried out in a mold, and the present invention has no special limitation on the size of the mold, and it can be selected according to actual needs.

[0099] In the present invention, the temperature of the aging treatment is preferably 80-100°C, more preferably 85-95°C; the time is preferably 4-6 h, more preferably 4.5-5.5 h. In the embodiments of the present invention, the temperature of the aging treatment can be 85°C, 82°C or 90°C, and the time can be 6 h or 4 h.

[0100] In the present invention, the aging treatment can further improve the oxidation resistance and chemical resistance of the rubber.

[0101] The present invention does not impose any special limitations on the process of the extrusion molding, and any process well-known to those skilled in the art can be adopted.

[0102] The present invention does not impose any special limitations on the size of the rubber, and it can be selected according to actual needs.

[0103] The present invention also provides a fully encapsulated rubber O-ring, which includes an inner core rubber strip and a coating tube with heat shrinkage characteristics.

[0104] The inner core rubber strip is the rubber described in the above technical solution or the rubber prepared by the preparation method described in the above technical solution.

[0105] The material of the coating tube with heat shrinkage characteristics is fluorinated ethylene propylene copolymer (FEP).

[0106] In the present invention, the preparation method of the coating tube with heat shrinkage characteristics preferably includes the following steps:

[0107] After heating a coating tube made of fluorinated ethylene propylene copolymer (such as Figure 1 the structural schematic diagram shown by the reference numeral 2 in the figure), after radially expanding the coating tube, cooling and shaping and annealing treatments are sequentially carried out to obtain the coating tube with heat shrinkage characteristics (such as Figure 1 the structural schematic diagram shown by the reference numeral 21 in the figure);

[0108] The temperature of the heating is greater than the glass transition temperature (Tg) and less than the melting temperature.

[0109] In the present invention, the temperature of the heating is preferably 150-200°C, more preferably 160-190°C. In the embodiments of the present invention, the temperature of the heating can be 180°C.

[0110] In the present invention, the heating method is preferably heating using a hot blast stove or a heating mold.

[0111] In the present invention, the radial expansion is preferably an inner diameter expansion.

[0112] In the present invention, the radial stretching ratio of the radial expansion is preferably 1.1 to 2 times, more preferably 1.3 to 1.8 times; the expansion pressure is preferably 0.2 to 2 MPa, more preferably 0.5 to 1.5 MPa; the expansion speed is preferably 0.1 to 5 mm / s, more preferably 0.15 to 4 mm / s. In the embodiments of the present invention, the radial stretching ratio of the radial expansion can be 1.14 times, the expansion pressure can be 0.5 MPa, and the expansion speed can be 0.15 mm.

[0113] In the present invention, the radial stretching ratio preferably depends on the target heat shrinkage ratio, and the radial stretching ratio is preferably equal to the target heat shrinkage ratio; the expansion pressure is preferably adjusted according to the thickness of the coated tube, and the relationship between the expansion pressure and the thickness of the coated tube is preferably: the thicker the coated tube, the greater the required expansion pressure (there is no strict quantitative relationship); controlling the expansion speed within the above range can avoid material rupture caused by too fast expansion during the radial expansion process.

[0114] In the present invention, the cooling and shaping is preferably carried out by cooling in a cooling water tank. In the present invention, the temperature of the cooling and shaping is preferably 20 to 25 °C. In the embodiments of the present invention, the temperature of the cooling and shaping can be 20 °C.

[0115] In the present invention, the function of the cooling and shaping is to freeze the orientation state of the molecular chains.

[0116] In the present invention, the temperature of the annealing treatment is preferably 180 to 200 °C, more preferably 185 to 195 °C; the heat preservation time is preferably 0.5 to 1 h, more preferably 0.6 to 0.8 h; the heating rate for heating to the temperature of the annealing treatment is preferably 1 to 10 °C / min, more preferably 1 to 3 °C / min. In the embodiments of the present invention, the temperature of the annealing treatment can be 185 °C, the heat preservation time can be 0.5 h, and the heating rate can be 2 °C / min.

[0117] In the present invention, the function of the annealing treatment is to eliminate the residual internal stress during the radial expansion process and avoid the problem of size instability during the storage or use of the pipe; limiting the heating rate within the above range can avoid uneven size caused by thermal shock; the heat preservation time depends on the wall thickness of the coated tube, and the relationship between the heat preservation time and the wall thickness is that the thicker the wall thickness, the longer the heat preservation time, and the principle is to ensure that the temperature of all the pipes is evenly heated through.

[0118] After the annealing treatment is completed, the present invention preferably further includes cooling, and the cooling method is preferably natural cooling in the furnace to avoid deformation caused by thermal stress.

[0119] The present invention also provides a method for preparing the fully encapsulated rubber O-ring described in the above technical solution, including the following steps:

[0120] Insert the inner core rubber strip into the heat-shrinkable coating tube, and make one end of the heat-shrinkable coating tube expose the inner core rubber strip, denoted as end A; the other end does not expose the inner core rubber strip and has a cavity, denoted as end B; the lengths of the inner core rubber strip and the heat-shrinkable coating tube are equal;

[0121] After inserting a cylindrical stainless steel iron core with a wire diameter larger than the outer diameter of the inner core rubber strip into the cavity at end B for occupancy (the structural schematic diagram is as shown), perform heat shrinkage and cooling and shaping in sequence, and remove the cylindrical stainless steel iron core to obtain a rubber strip assembly with misaligned coating; Figure 2 Shown), and then perform heat shrinkage and cooling and shaping in sequence, and remove the cylindrical stainless steel iron core to obtain a rubber strip assembly with misaligned coating;

[0122] Insert the inner core rubber strip exposed at end A in the misaligned-coated rubber strip assembly into the cavity at end B of the misaligned-coated rubber strip assembly, and bond the side faces of both ends of the inner core rubber strip after insertion. After forming a closed ring, perform circumferential seam butt welding and curing heat treatment in sequence to obtain the fully encapsulated rubber O-ring.

[0123] In the present invention, the inner core rubber strip is inserted into the heat-shrinkable coating tube, and one end of the heat-shrinkable coating tube exposes the inner core rubber strip, denoted as end A; the other end does not expose the inner core rubber strip and has a cavity, denoted as end B; the lengths of the inner core rubber strip and the heat-shrinkable coating tube are equal; after inserting a cylindrical stainless steel iron core with a wire diameter larger than the outer diameter of the inner core rubber strip into the cavity at end B for occupancy, perform heat shrinkage and cooling and shaping in sequence, and remove the cylindrical stainless steel iron core to obtain a rubber strip assembly with misaligned coating.

[0124] In the present invention, the lengths of the inner core rubber strip and the heat-shrinkable coating tube are preferably calculated according to the circumference of the target coated O-ring's specifications.

[0125] The present invention does not have any special limitations on the outer diameter of the inner core rubber strip and the inner diameter of the coating tube, ensuring that there is a certain gap between the inner core rubber strip and the coating tube when the inner core rubber strip is inserted into the coating tube, and the smaller the gap, the better under the premise that it can be easily inserted. In the present invention, the unilateral gap between the inner core rubber strip and the coating tube is preferably 0.1 - 0.3 mm.

[0126] In the present invention, the length of the inner core rubber strip exposed at one end of the heat-shrinkable coating tube is determined according to the specifications of the target coated O-ring (the exposed length is greater than or equal to 5 mm and less than or equal to 10 times the wire diameter of the target coated O-ring).

[0127] In the present invention, the difference between the wire diameter of the cylindrical stainless steel core and the outer diameter of the inner core rubber strip is preferably 0.1 - 0.3 mm. In an embodiment of the present invention, the difference between the wire diameter of the cylindrical stainless steel core and the outer diameter of the inner core rubber strip can be 0.1 mm.

[0128] In the present invention, the end face of the cylindrical stainless steel core is preferably flat and smooth to ensure that it closely adheres to the end face of the ethylene propylene diene monomer (EPDM) rubber strip.

[0129] In the present invention, the heat shrinkage temperature is preferably 200 - 240 °C, more preferably 210 - 230 °C; the time is preferably 2 - 15 min, more preferably 5 - 10 min. In an embodiment of the present invention, the heat shrinkage temperature can be 220 °C and the time can be 5 min.

[0130] In the present invention, the heat shrinkage process preferably involves stably placing the intermediate structure obtained after occupying the position on a tray to prevent displacement, and then placing it in an oven for heating to perform heat shrinkage.

[0131] In the present invention, during the heat shrinkage process, the cladding tube radially contracts and wraps around the surfaces of the inner core rubber strip and the cylindrical stainless steel core to become a shrinkable FEP fluoroplastic tube.

[0132] In the present invention, the cooling and shaping method is preferably furnace cooling; the present invention has no special limitation on the furnace cooling process, and it can be carried out using a process well-known to those skilled in the art.

[0133] The present invention has no special limitation on the process of removing the cylindrical stainless steel core, and it can be carried out using a process well-known to those skilled in the art.

[0134] In the present invention, the outer diameter of the misaligned cladding rubber strip assembly is preferably the same as the outer diameter of the target cladding O-ring; the inner core rubber strip and the cladding tube are misaligned and the cladding rubber strip assembly is partially fully covered and partially has a lumen.

[0135] After obtaining the misaligned cladding rubber strip assembly, in the present invention, the inner core rubber strip exposed at the A end in the misaligned cladding rubber strip assembly is inserted into the cavity at the B end in the misaligned cladding rubber strip assembly, and the two side faces at both ends of the inserted inner core rubber strip are adhesively bonded together. After forming a closed ring, circumferential seam welding and curing heat treatment are carried out in sequence to obtain the fully covered rubber O-ring (as Figure 6 shown).

[0136] Before the butt joint, it is preferred in the present invention to cut the two ends of the misaligned rubber strip assembly with a sharp tool to make the end faces of the two ends flat and the surfaces dry and clean; then chemically treat the end faces of the rubber strips to improve the bonding strength in the subsequent processes. In the present invention, the chemical treatment preferably includes cleaning and coating an active intermediate layer in sequence; the present invention has no special limitation on the cleaning process, and it can be carried out by a process well-known to those skilled in the art and ensure that there are no impurities (such as oil stains, antioxidants, etc.) on the cleaned end faces. In the present invention, the material of the active intermediate layer is preferably a silane coupling agent. In the present invention, coating the active intermediate layer is more conducive to bonding.

[0137] After the chemical treatment is completed, the present invention also preferably includes coating a neutral lubricant on the outer side of the inner core rubber strip at the A end and coating an adhesive on the end face of the inner core rubber strip at the B end. In the present invention, the neutral lubricant is preferably silicone oil. The adhesive is preferably cyanoacrylate glue.

[0138] In the present invention, the process of the butt joint is preferably to insert the misaligned rubber strip assembly into a thin-walled quartz tube to ensure that the thin-walled quartz tube can freely slide outside the misaligned rubber strip assembly (as Figure 3 shown), and then insert the exposed inner core rubber strip at the A end in the misaligned rubber strip assembly into the cavity at the B end in the misaligned rubber strip assembly (as Figure 4 shown), and the two side faces of the inner core rubber strip after the butt joint are adhesively connected to form a closed ring. In the present invention, the wall thickness of the thin-walled quartz tube is preferably 0.2 - 0.5 mm, the length of the thin-walled quartz tube is preferably 10 - 25 mm, and the unilateral gap between the inner diameter of the thin-walled quartz tube and the outer diameter of the misaligned rubber strip assembly is preferably 0.1 - 0.3 mm.

[0139] In the present invention, the temperature of the circumferential seam butt welding is preferably 280 - 300 °C, and the time is preferably 10 - 50 s. In the embodiments of the present invention, the temperature of the circumferential seam butt welding can be 280 °C, and the time can be 22 s.

[0140] In the present invention, the process of the circumferential seam butt welding is preferably to move the thin-walled quartz tube to the circumferential joint of the closed ring, and then heat the thin-walled quartz tube with a hot air gun or a local heating device until the coated tube melts and apply a stable squeezing force in opposite directions on both sides of the joint (as Figure 5 shown). The present invention has no special limitation on the magnitude of the squeezing force, and it can be of a magnitude well-known to those skilled in the art and ensure complete sealing.

[0141] After the circumferential seam butt welding, the present invention preferably further includes cooling and solidification. In the present invention, during the cooling and solidification process, it is preferable to maintain the above-mentioned stable extrusion pressure and appropriately slide the thin-walled quartz tube to flatten the weld seam and discharge the bubbles generated during the heating process.

[0142] In the present invention, the auxiliary flattening process of the thin-walled quartz tube can ensure that the surface quality of the cladding tube during fusion welding is higher and smoother.

[0143] In the present invention, the temperature of the curing heat treatment is preferably 180-200 °C, and the time is preferably 10-24 h. In the embodiments of the present invention, the temperature of the curing heat treatment can be 185 °C, and the time can be 24 h. In the present invention, the curing heat treatment is preferably carried out in an oven.

[0144] After the curing heat treatment is completed, the present invention preferably further includes furnace cooling. After the furnace cooling is completed, the present invention preferably further includes breaking the thin-walled quartz tube.

[0145] The present invention also provides the application of the fully encapsulated rubber O-ring described in the above technical solution or the fully encapsulated rubber O-ring prepared by the preparation method described in the above technical solution in the field of sealing against corrosion by special liquid oxidants. In the present invention, the special liquid oxidant is preferably hydroxylammonium perchlorate (HAP). The present invention does not have any special limitations on the method of the application, and the method well-known to those skilled in the art can be used.

[0146] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

[0147] Example 1

[0148] Raw materials for preparing the inner core rubber strip: 100 parts by weight of ethylene propylene diene monomer rubber (vinyl content is 65%), 45 parts by weight of nano-silicon, 10 parts by weight of perfluoropolyether oil, 1.2 parts by weight of antioxidant Irganox1010, 2 parts by weight of anti-ozone agent 4020, 1.1 parts by weight of zinc diethyldithiocarbamate (ZnDDC), 1 part by weight of accelerator CBS (N-cyclohexyl-2-benzothiazole sulfonamide), 4 parts by weight of zinc oxide, 1.5 parts by weight of stearic acid, 5 parts by weight of fluorinated graphene, 4 parts by weight of low molecular weight polyethylene wax (molecular weight is 1000-3000 g / mol) and 4 parts by weight of phosphate flame retardant TPP;

[0149] Preparation process of the inner core rubber strip: After mixing ethylene propylene diene monomer (EPDM) rubber until it reaches a plasticized state, successively add nano-silicon, perfluoropolyether oil, stearic acid, and polyethylene wax to the obtained plasticized EPDM rubber, then add antioxidant Irganox1010, anti-ozone agent 4020, fluorinated graphene, and phosphate flame retardant, and finally add zinc diethyldithiocarbamate, accelerator CBS, and zinc oxide, and conduct mixing (temperature is 70 °C, time is 7 min) to obtain a rubber compound;

[0150] After transferring the rubber compound to a mill for rolling processing to obtain a rubber compound with a sheet thickness of 5 mm, place the rubber compound in a mold for compression molding and vulcanization (applying a pressure of 18 MPa, temperature of 175 °C, time of 10 min) and aging treatment (conducted in hot air, temperature of 90 °C, time of 4 h) to obtain a rubber (inner core rubber strip) (wire diameter is 3 mm);

[0151] Preparation process of the FEP coating tube with heat shrinkage characteristics: Heat an FEP coating tube with an inner diameter of 3 mm and a wall thickness of 0.5 mm in a hot air furnace to 180 °C to make it have good plastic deformation ability, then use a nitrogen cylinder, adjust the inflation and expansion pressure with a pressure reducing valve to 0.5 MPa, and the expansion speed is 0.15 mm / s, expand the inner diameter of the FEP coating tube to 3.5 mm to generate radial stress, so that its radial stretching ratio is 1.14 times, endowing it with heat shrinkage. After the radial expansion is completed, the particle size is quickly cooled through a cooling water (water temperature is 20 °C) tank to freeze the orientation state of the molecular chains. After annealing the cooled and shaped FEP coating tube (starting from 100 °C, increasing 10 °C every 10 min until the target annealing temperature is 185 °C, and holding for 0.5 h), slowly cool it to room temperature with the furnace to obtain an FEP coating tube with heat shrinkage characteristics (inner diameter is 3.5 mm, wall thickness is 0.2 mm, heat shrinkage ratio is 1.14);

[0152] Preparation method of fully encapsulated rubber O-ring: Cut an inner core rubber strip with a length of 188.5 mm and an FEP coating tube with heat shrinkage characteristics respectively. After threading the cut inner core rubber strip into the FEP coating tube with heat shrinkage characteristics, one end of the inner core rubber strip extends out of the FEP coating tube (A end), and the other end retracts into the FEP coating tube (B end), with a misalignment distance of 15 mm. Insert a cylindrical stainless steel iron core with a wire diameter of 3.3 mm (the cross-section is required to be flat and smooth and closely attached to the end face of the ethylene propylene diene monomer rubber strip) into the cavity of the FEP coating tube caused by the misalignment for positioning. Then, place the threaded inner core rubber strip, FEP coating tube, and cylindrical stainless steel iron core stably in a tray to prevent movement, and place them in an oven for heating (heating temperature is 220 °C, time is 5 min). Then, turn off the heating and cool down to room temperature with the furnace. After heating, the FEP coating tube radially shrinks and wraps around the inner core rubber strip and the cylindrical stainless steel iron core to become a shrunk FEP coating tube. After complete cooling and shaping, pull out the cylindrical stainless steel iron core to obtain a misaligned wrapped rubber strip assembly with the same outer diameter as the target fully encapsulated rubber O-ring;

[0153] Cut the two ends of the misaligned wrapped rubber strip assembly with a sharp tool to make them flat, and keep the surface dry and clean. Then, chemically treat the end face of the inner core rubber strip (remove the impurities on the end face surface with an organic solvent and then coat a silane coupling agent) to improve the bonding strength in the subsequent process. Then, put on a thin-walled quartz tube (wall thickness is 0.5 mm, length is 20 mm, and the unilateral gap between the inner diameter of the thin-walled quartz tube and the outer diameter of the misaligned wrapped rubber strip assembly is 0.2 mm), and the thin-walled quartz tube can slide freely outside the misaligned wrapped rubber strip assembly. Apply a neutral lubricant (specifically silicone oil) to the outer side of the inner core rubber strip exposed at the A end of the misaligned wrapped rubber strip assembly and insert it into the cavity of the B end (adhesive is applied to the end face of the inner core rubber strip, and the adhesive is specifically cyanoacrylate glue) of the misaligned wrapped rubber strip assembly (as shown in Figure 4 ), and the two side faces of the inner core rubber strip at both ends are adhesively connected after insertion to form a closed ring. After moving the thin-walled quartz tube to the annular joint of the closed body, use a local heating device equipped with a die head to heat the thin film quartz tube to melt the FEP coating tube (heating temperature is 280 °C, time is 22 s), and then apply a stable squeezing force in opposite directions on both sides of the joint to make the annular seam interface of the FEP coating tube melt and weld. Then, cool and solidify (the squeezing force remains stable during the cooling and solidifying process, and the thin-walled quartz tube is appropriately slid to flatten the weld seam and discharge the bubbles generated during the heating process to improve the welding quality). Finally, perform curing heat treatment (185 °C, 24 h), cool down to room temperature with the furnace, and then break the thin-walled quartz tube to obtain a fully encapsulated rubber O-ring (inner diameter is 60 mm, wire diameter is 3.55 mm).

[0154] Example 2

[0155] Raw materials for preparing the inner core rubber strip: 100 parts by weight of ethylene propylene diene monomer rubber (vinyl content is 60%), 35 parts by weight of white carbon black, 8 parts by weight of fluorosilicone oil, 1 part by weight of antioxidant 4010NA, 2 parts by weight of anti-ozone agent 4020, 1 part by weight of bis(dithiocarbamate) vulcanizing agent (DTDM), 1 part by weight of accelerator TMTD (tetramethylthiuram disulfide), 3.5 parts by weight of zinc oxide, 1 part by weight of stearic acid, 5 parts by weight of fluorinated graphite, 3 parts by weight of low molecular weight polyethylene wax (molecular weight is 1000 - 3000 g / mol) and 5 parts by weight of phosphate flame retardant TPP;

[0156] Preparation process of the inner core rubber strip: After kneading the ethylene propylene diene monomer rubber to a plasticized state, successively add white carbon black, fluorosilicone oil, stearic acid and polyethylene wax to the obtained plasticized ethylene propylene diene monomer rubber, then add antioxidant 4010NA, anti-ozone agent 4020, fluorinated graphite and phosphate flame retardant, and finally add bis(dithiocarbamate) vulcanizing agent, accelerator TMTD and zinc oxide, and carry out kneading (temperature is 62 °C, time is 8 min) to obtain the rubber compound;

[0157] After transferring the rubber compound to an open mill for open mill processing to obtain a rubber compound with a sheet thickness of 5 mm, put the rubber compound into a mold for compression molding and vulcanization (applied pressure is 16 MPa, temperature is 165 °C, time is 8 min) and aging treatment (in hot air, temperature is 82 °C, time is 6 h) to obtain rubber (inner core rubber strip) (wire diameter is 3 mm);

[0158] The preparation process of the FEP coating tube with heat shrinkage characteristics refers to Example 1;

[0159] The preparation method of the fully coated rubber O-ring refers to Example 1.

[0160] Example 3

[0161] Raw materials for preparing the inner core rubber strip: 100 parts by weight of ethylene propylene diene monomer rubber (vinyl content is 55%), 30 parts by weight of nano-silicon, 10 parts by weight of high fluoropolyether oil, 1 part by weight of antioxidant Irganox 1076, 2 parts by weight of hindered amine light stabilizer Chimassorb 944, 1.1 parts by weight of zinc diethyldithiocarbamate (ZnDDC), 1 part by weight of accelerator CBS (N-cyclohexyl-2-benzothiazolesulfonamide), 5 parts by weight of zinc oxide, 1.2 parts by weight of stearic acid, 4 parts by weight of fluorinated graphene, 5 parts by weight of microcrystalline wax and 4 parts by weight of phosphate flame retardant RDP;

[0162] Preparation process of the inner core rubber strip: After mixing ethylene propylene diene monomer (EPDM) rubber until it reaches a plasticized state, successively add nano-silicon, perfluoropolyether oil, stearic acid, and microcrystalline wax to the obtained plasticized EPDM rubber, then add antioxidant Irganox1076, hindered amine light stabilizer Chimassorb 944, fluorinated graphene, and phosphate flame retardant, and finally add zinc diethyldithiocarbamate, accelerator CBS, and zinc oxide, and conduct mixing (temperature is 60°C, time is 8 min) to obtain a rubber compound;

[0163] After transferring the rubber compound to a two-roll mill for rolling processing to obtain a rubber compound with a sheet thickness of 3 mm, place the rubber compound in a mold for compression molding and vulcanization (applying a pressure of 15 MPa, temperature of 162°C, time of 15 min) and aging treatment (conducted in hot air, temperature of 85°C, time of 6 h) to obtain a rubber (inner core rubber strip) (wire diameter is 3 mm);

[0164] The preparation process of the FEP coating tube with heat shrinkage characteristics refers to Example 1;

[0165] The preparation method of the fully covered rubber O-ring refers to Example 1.

[0166] Test example

[0167] Make the inner core rubber strips described in Examples 1 to 3 into standard tensile specimens of type II (refer to GB / T528 - 2009) and standard compression specimens of type A (refer to DB / T7759.1 - 2015), and test their performance parameters such as tensile strength, elongation at break, and compression set after being soaked in HAP for 1, 3, 7, 14, 28, 56, 112, and 224 days respectively. The test results are shown in Table 1 and Figures 7-9 as shown (where Figure 7 is the change in the tensile strength parameter of the inner core rubber strip of the fully covered rubber O-ring described in Examples 1 to 3 under HAP corrosion aging, Figure 8 is the change in the elongation at break parameter of the inner core rubber strip of the fully covered rubber O-ring described in Examples 1 to 3 under HAP corrosion aging, Figure 9 is the change in the compression set parameter of the inner core rubber strip of the fully covered rubber O-ring described in Examples 1 to 3 under HAP corrosion aging);

[0168] Table 1 Performance parameters of the inner core rubber strips described in Examples 1 to 3

[0169]

[0170] From Table 1 and Figures 7-9It can be seen that under the corrosion of the HAP solution, the inner core rubber strips described in Examples 1 to 3 still have a tensile strength greater than 15 MPa, an elongation at break greater than 150%, and a compression set less than 20% after 224 days of testing, and show the characteristic of tending to be stable with the increase of the test duration, indicating that they have good tolerance to the corrosion and aging of HAP.

[0171] The fully encapsulated rubber O-rings prepared in Examples 1 to 3 were subjected to a HAP solution immersion test with reference to Part 5.6 of GB / T 5720-2008, and parameters such as the change in tensile properties, mass and volume, and hardness (IRHD) before and after 48 hours of immersion were tested. The test results are shown in Table 2.

[0172] Table 2 Performance parameters of the fully encapsulated rubber O-rings described in Examples 1 to 3 for HAP solution

[0173]

[0174] As can be seen from Table 2, for the fully encapsulated rubber O-rings prepared in Examples 1 to 3 before and after immersion in the HAP solution, the change rate of tensile strength is within ±5‰, the change in elongation at break is within ±2%, the mass change rate is within 1%, and the hardness change is within ±1 (IRHD). No corrosion signs were found on the surface of the fully encapsulated rubber O-rings before and after the immersion test, and there was no obvious difference observed with the naked eye. The above data show that the outer coating layer plays a good isolation role against the corrosion of the HAP solution, and the change in the index parameters before and after immersion is very small, which is at the same order of magnitude as the measurement error, indicating that they have good tolerance to the corrosion and aging of HAP.

[0175] The above description is only a preferred embodiment of the present invention and does not impose any form of limitation on the present invention. It should be noted that for those of ordinary skill in the art, several improvements and refinements can be made without departing from the principle of the present invention, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A rubber, characterized in that, By mass parts, it includes the following preparation raw materials: 100 parts of ethylene propylene diene monomer rubber, 30 - 50 parts of reinforcing agent, 5 - 10 parts of plasticizer, 1 - 2 parts of antioxidant, 1 - 2 parts of stabilizer, 0.8 - 1.2 parts of vulcanizing agent, 0.5 - 1 part of accelerator, 3 - 5 parts of zinc oxide, 1 - 1.5 parts of stearic acid, 3 - 6 parts of special modification additive, 2 - 5 parts of preservative and 3 - 5 parts of phosphate flame retardant; the vinyl content in the ethylene propylene diene monomer rubber is 55wt% - 65wt%; the vulcanizing agent includes bis(dithiocarbamate) vulcanizing agent and / or zinc diethyldithiocarbamate; the accelerator includes tetramethylthiuram disulfide and / or N-cyclohexyl-2-benzothiazolesulfenamide.

2. The rubber according to claim 1, wherein The reinforcing agent includes silica and / or perfluoropolyether oil; The plasticizer includes fluorosilicone oil and / or perfluoropolyether oil; The model of the antioxidant includes one or several of 4010NA, Irganox 1010 and Irganox 1076; The stabilizer includes antiozonant and / or hindered amine light stabilizer; The special modification additive includes fluorinated graphite and / or fluorinated graphene; The preservative includes microcrystalline wax and / or low molecular weight polyethylene wax, and the molecular weight of the low molecular weight polyethylene wax is 1000 - 5000g / mol; The phosphate flame retardant includes triphenyl phosphate and / or resorcinol bis(diphenyl phosphate).

3. The preparation method of the rubber according to claim 1 or 2, characterized in that, It includes the following steps: After sequentially adding the reinforcing agent, plasticizer, stearic acid and preservative to the plasticized ethylene propylene diene monomer rubber, add the antioxidant, stabilizer, special modification additive and phosphate flame retardant, and finally add the vulcanizing agent, accelerator and zinc oxide, and carry out mixing to obtain the rubber compound; Carry out open mill processing, vulcanization molding and aging treatment on the rubber compound in sequence to obtain the rubber.

4. The preparation method according to claim 3, characterized in that, The temperature of the mixing is 50 - 70°C, and the time is 6 - 8min; The pressure of the compression molding vulcanization is 10 - 20MPa, the temperature is 160 - 180°C, and the time is 2 - 15min; The temperature of the aging treatment is 80 - 100°C, and the time is 4 - 6h.

5. A fully encapsulated rubber O-ring, including an inner core rubber strip and a coating tube with heat shrinkage characteristics; The inner core rubber strip is the rubber described in claim 1 or 2 or the rubber prepared by the preparation method described in claim 3 or 4; The material of the coating tube with heat shrinkage characteristics is fluorinated ethylene propylene copolymer.

6. The fully encapsulated rubber O-ring according to claim 5, wherein, The preparation method of the coating tube with heat shrinkage characteristics includes the following steps: After heating the coating tube made of fluorinated ethylene propylene copolymer, radially expand the coating tube, and then carry out cooling and shaping and annealing treatment in sequence to obtain the coating tube with heat shrinkage characteristics; The heating temperature is greater than the glass transition temperature and less than the melting temperature.

7. The preparation method of the fully encapsulated rubber O-ring described in claim 5 or 6, including the following steps: Insert the inner core rubber strip into the heat-shrinkable coating tube, and make one end of the heat-shrinkable coating tube expose the inner core rubber strip, denoted as end A; the other end does not expose the inner core rubber strip and has a cavity, denoted as end B; the lengths of the inner core rubber strip and the heat-shrinkable coating tube are equal; After inserting a cylindrical stainless steel iron core with a wire diameter larger than the outer diameter of the inner core rubber strip into the cavity at end B for occupying the position, perform heat shrinkage and cooling and shaping in sequence, and pull out the cylindrical stainless steel iron core to obtain a rubber strip assembly with misaligned coating; Insert the inner core rubber strip exposed at end A in the misaligned-coated rubber strip assembly into the cavity at end B of the misaligned-coated rubber strip assembly, and bond the side faces of both ends of the inner core rubber strip after the insertion to form a closed ring. Then, perform circumferential seam butt welding and curing heat treatment in sequence to obtain the fully coated rubber O-ring; 8. The preparation method according to claim 7, characterized in that, The difference between the wire diameter of the cylindrical stainless steel iron core and the outer diameter of the inner core rubber strip is 0.1 - 0.3 mm; The temperature of the heat shrinkage is 200 - 240 °C, and the time is 2 - 15 min; 9. The preparation method according to claim 7, characterized in that, Before the insertion, apply a neutral lubricant to the outer side of the inner core rubber strip at end A, and apply an adhesive to the end face of the inner core rubber strip at end B; The temperature of the circumferential seam butt welding is 280 - 300 °C, and the time is 10 - 50 s; During the circumferential seam welding, use a quartz glass tube to cover the circumferential seam butt welding place to flatten the weld seam; The temperature of the curing heat treatment is 180 - 200 °C, and the time is 10 - 24 h; 10. Application of the fully coated rubber O-ring according to claim 5 or 6 or the fully coated rubber O-ring prepared by the preparation method according to any one of claims 7 - 9 in the field of sealing against corrosion by special liquid oxidants.

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