A sealing material and a method for producing the same

Abstract

The application provides a sealing material and a preparation method thereof, and belongs to the technical field of static sealing materials.The sealing material comprises, from top to bottom, a layer of expanded polytetrafluoroethylene and a layer of pressure-sensitive adhesive arranged in sequence; the layer of expanded polytetrafluoroethylene comprises, from top to bottom, a wear-resistant layer, an expanded layer and a modified layer.The high-elasticity and anti-creep composite sealing material prepared by the application has good wear resistance of the layer of expanded polytetrafluoroethylene, which can reduce abrasion, and the pressure-sensitive adhesive and the sealing surface can be bonded together, so that the reliability and service life of the sealing material can be greatly increased.The results of the examples show that the elongation at break of the sealing material provided by the application is greater than or equal to 500%, the 23 DEG C 180 DEG peeling strength is greater than or equal to 6 N / m, and the tensile strength is greater than or equal to 4 MPa.

Description

Technical Field

[0001] This invention relates to the field of static sealing materials technology, and in particular to a sealing material and its preparation method. Background Technology

[0002] The reliability of helicopters in complex environments is a key factor affecting their performance. Compared to fixed-wing aircraft, helicopters typically fly at altitudes below 6,000 meters and cruise at speeds around 280 km / h, classifying them as low-to-medium altitude, low-speed aircraft. Operating in harsh natural environments such as humid heat, dry cold, sandstorms, and seawater, helicopters are highly susceptible to corrosion of their structures and system components, leading to component failures. Furthermore, the vibrations generated by the rotor and transmission components during flight place even higher demands on the overall sealing and protection of the aircraft.

[0003] Helicopter structural sealing involves installing sealing materials at the joints of frames and beams, as well as other sealing ports and covers, to prevent corrosion of the frames, beams, and internal fuselage caused by moisture, salt spray, and dirt. However, the rubber and expanded PTFE used in these seals exhibit poor creep resistance and resilience under vibration conditions, leading to premature seal failure and a short service life. In extreme environments, their lifespan does not exceed six months. To address the poor sealing performance of PTFE alone in helicopter structures, composite sealing materials combining PTFE and elastomers such as polyurethane and rubber have been developed in recent years. These highly flexible elastomers compensate for the insufficient elasticity of PTFE. Using PTFE and elastomers together as sealing materials offers more advantages and a wider range of applications than using them alone, combining the benefits of both. The elastomer provides sufficient sealing preload and compensates for the wear of the PTFE sealing material, significantly improving sealing performance. However, existing composites still suffer from insufficient flexibility and strength of PTFE, low surface energy of the PTFE material, and weak bonding strength between the PTFE and elastomer layers.

[0004] Therefore, providing a sealing material with high flexibility, high strength, good creep resistance and resilience has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a sealing material and its preparation method. The sealing material provided by this invention has excellent corrosion resistance, non-aging properties, creep resistance, low coefficient of friction, and high tensile strength.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a sealing material comprising an expanded polytetrafluoroethylene layer and a pressure-sensitive adhesive layer stacked sequentially from top to bottom;

[0008] The expanded polytetrafluoroethylene layer comprises a wear-resistant layer, an expanded layer, and a modified layer stacked sequentially from top to bottom.

[0009] Preferably, the sealing material further includes an elastomer layer located between the expanded polytetrafluoroethylene layer and the pressure-sensitive adhesive layer.

[0010] Preferably, the thickness of the expanded polytetrafluoroethylene layer is 300–1000 μm, and the thickness deviation of the expanded polytetrafluoroethylene layer is ≤10 μm; the thickness of the elastomer layer is 210–800 μm, and the thickness deviation of the elastomer layer is ≤10 μm; the thickness of the pressure-sensitive adhesive layer is 1–20 μm, and the thickness deviation of the pressure-sensitive adhesive is ≤2 μm.

[0011] Preferably, the raw materials for preparing the wear-resistant layer, by mass percentage, include 60-80% PTFE resin, 10-39.5% liquid lubricant, and 0.5-10% inorganic oxide; the raw materials for preparing the expanded layer include 60-85% PTFE resin and 15-40% liquid lubricant; and the raw materials for preparing the modified layer include 60-80% PTFE resin, 10-39.5% liquid lubricant, and 0.5-10% thermoplastic fluoropolymer.

[0012] Preferably, the PTFE resin is a PTFE resin with a crystallinity ≥97%; the liquid lubricant is naphtha, white oil, or mineral oil; the inorganic oxide is one or more of silicon dioxide, alumina, and rare earth oxides; and the thermoplastic fluoropolymer is one or more of polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, perfluoroethylene propylene, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, polyvinylidene fluoride, trifluorochloroethylene homopolymer and copolymer, and perfluorosulfonic acid resin.

[0013] Preferably, the preparation method of the expanded polytetrafluoroethylene layer is to prepare a wear-resistant layer, an expanded layer and a modified layer separately, and then combine the wear-resistant layer, the expanded layer and the modified layer to obtain the expanded polytetrafluoroethylene layer.

[0014] Alternatively, the raw materials for the wear-resistant layer, expanded layer, and modified layer can be separately prepared into wear-resistant layer sheets, expanded layer sheets, and modified layer sheets, respectively. These sheets are then stacked together and sequentially dried and stretched to obtain an expanded polytetrafluoroethylene layer.

[0015] Preferably, the raw materials for preparing the elastomer layer include one or more of polyurethane elastomer, polyurethane rubber, curable siloxane, fluorosilicone rubber, perfluororubber, and perfluoropolyether silicone rubber.

[0016] Preferably, the raw materials for preparing the pressure-sensitive adhesive layer include polytetrahydrofuran ether polyurethane prepolymer, tackifier, filler, and solvent; the tackifier is a polymer tackifier, phenolic tackifier, or rosin tackifier, the filler is a silicate, carbonate, or oxide, and the solvent is toluene, ethyl acetate, or ethanol.

[0017] Preferably, the raw materials for preparing the pressure-sensitive adhesive layer are 10-40 wt.% polytetrahydrofuran ether polyurethane prepolymer, 10-30 wt.% tackifier, 10-50 wt.% filler, and 30-60 wt.% solvent.

[0018] This invention provides a method for preparing the sealing material described in the above technical solution, comprising: using an expanded polytetrafluoroethylene layer as a base film, coating a pressure-sensitive adhesive solution extruded by a screw extruder onto the expanded polytetrafluoroethylene layer, and obtaining the sealing material after drying;

[0019] When the sealing material includes an elastomer layer, an expanded polytetrafluoroethylene (PTFE) layer is used as the base film. The elastomer layer is extruded onto the expanded PTFE layer using a screw extruder. After the elastomer layer is dried on the expanded PTFE layer, a pressure-sensitive adhesive solution extruded by the screw extruder is coated onto the elastomer layer. After drying, the sealing material is obtained.

[0020] This invention provides a sealing material comprising a layer of expanded polytetrafluoroethylene (PTFE) and a pressure-sensitive adhesive layer stacked sequentially from top to bottom; the expanded PTFE layer further comprises a wear-resistant layer, an expanded layer, and a modified layer stacked sequentially from top to bottom. The expanded PTFE layer in the high-elasticity, creep-resistant composite sealing material prepared by this invention exhibits excellent wear resistance, reducing wear. Combined with the adhesion between the pressure-sensitive adhesive and the sealing surface, this significantly increases the reliability and lifespan of the seal. Furthermore, the material used in this invention possesses excellent chemical resistance, meeting the needs of helicopters operating in complex environments. Results from the embodiments show that the sealing material provided by this invention has an elongation at break ≥500%, a 180° peel strength at 23°C ≥6 N / m, and a tensile strength ≥4 MPa. Attached Figure Description

[0021] Figure 1 A schematic diagram of the structure of the sealing material provided by the present invention;

[0022] Figure 1 In the middle, 10 is the expanded polytetrafluoroethylene layer, 20 is the middle elastomer layer, and 30 is the bottom layer coated with pressure-sensitive adhesive.

[0023] Figure 2 This is a schematic diagram of the expanded polytetrafluoroethylene layer in the sealing material provided by the present invention.

[0024] Figure 2 In the diagram, 101 is the wear-resistant layer, 102 is the expanded layer, and 103 is the modified layer.

[0025] Figure 3 This is a uniaxial tensile SEM image of the expanded polytetrafluoroethylene layer prepared in Example 3 of the present invention;

[0026] Figure 3 In the diagram, 1001 represents the fibril, and 1002 represents the polymer node.

[0027] Figure 4 This is a uniaxial tensile SEM image of the expanded polytetrafluoroethylene layer prepared in Example 4 of the present invention;

[0028] Figure 4 In the diagram, 2001 represents the fibril and 2002 represents the polymer node. Detailed Implementation

[0029] The present invention provides a sealing material comprising an expanded polytetrafluoroethylene layer and a pressure-sensitive adhesive layer stacked sequentially from top to bottom.

[0030] In this invention, the expanded polytetrafluoroethylene layer comprises a wear-resistant layer, an expanded layer, and a modified layer stacked sequentially from top to bottom.

[0031] In this invention, the preferred method for preparing the expanded polytetrafluoroethylene (PTFE) layer is to prepare a wear-resistant layer, an expanded layer, and a modified layer separately, and then combine the wear-resistant layer, the expanded layer, and the modified layer to obtain the expanded PTFE layer; or the preferred method for preparing the expanded PTFE layer is to prepare the raw materials of the wear-resistant layer, the expanded layer, and the modified layer into wear-resistant layer sheets, expanded layer sheets, and modified layer sheets respectively, and then stack the wear-resistant layer sheets, expanded layer sheets, and modified layer sheets together and sequentially dry and stretch them to obtain the expanded PTFE layer.

[0032] In this invention, when the expanded polytetrafluoroethylene (PTFE) layer is prepared by separately preparing a wear-resistant layer, an expanded layer, and a modified layer, and then combining the wear-resistant layer, the expanded layer, and the modified layer to obtain the expanded PTFE layer, the composite temperature is preferably 320–400°C, more preferably 350–380°C; the composite pressure is preferably 0.1–1 MPa, more preferably 0.2–0.8 MPa, and even more preferably 0.4–0.6 MPa; the composite time is preferably 10–200 s, more preferably 20–150 s, and even more preferably 20–100 s. In this invention, the composite is preferably performed on a flatbed press or a roller press; the thickness of the expanded PTFE layer is preferably 300–1000 μm, more preferably 500–800 μm; and the thickness deviation of the expanded PTFE layer is preferably ≤10 μm.

[0033] In this invention, the raw materials for preparing the wear-resistant layer preferably include 60-80% PTFE resin, 10-39.5% liquid lubricant, and 0.5-10% inorganic oxides by weight percentage. In this invention, the PTFE resin in the wear-resistant layer is the main film-forming material, the liquid lubricant acts as a pore-forming agent and also provides lubrication; the inorganic oxides have high hardness and mainly play a role in wear resistance. By controlling the amount of each component, a better wear-resistant effect can be achieved.

[0034] In this invention, the PTFE resin is preferably a PTFE resin with a crystallinity of ≥97%; the liquid lubricant is preferably naphtha, white oil, or mineral oil; the inorganic oxide is preferably one or more of silicon dioxide, aluminum oxide, and rare earth oxides, and the rare earth oxide is preferably cerium oxide or lanthanum oxide.

[0035] In this invention, the method for preparing the wear-resistant layer preferably includes the following steps:

[0036] (1) Mix PTFE resin, liquid lubricant and inorganic oxide, and then press and extrude to obtain the first preform;

[0037] (2) The first blank obtained in step (1) is dried and stretched sequentially to obtain the first composite film;

[0038] (3) The first composite film obtained in step (2) is laminated with n layers to obtain a wear-resistant layer.

[0039] The present invention preferably involves mixing PTFE resin, liquid lubricant, and inorganic oxide, followed by pressing and extrusion molding to obtain a first preform. The present invention does not impose any particular limitations on the specific mixing operation of the PTFE resin, liquid lubricant, and inorganic oxide, as long as the components are mixed uniformly.

[0040] In this invention, the pressing is preferably performed in a plunger press. In this invention, the shape of the pressed product is preferably tubular or cylindrical. In this invention, the extrusion molding is preferably performed in a plunger extruder. This invention does not impose any specific limitations on the model of the plunger press and plunger extruder; commercially available products well-known to those skilled in the art can be used.

[0041] In this invention, the density of the first blank is preferably 1.4 to 1.8 g / cm³. 3 More preferably, it is 1.5–1.7 g / cm³. 3 Further preferred value is 1.6 g / cm³ 3 The thickness of the first blank is preferably 50-300 μm, more preferably 100-250 μm, and even more preferably 150-200 μm.

[0042] After obtaining the first blank, the present invention preferably dries and stretches the first blank sequentially to obtain the first composite film.

[0043] In this invention, the drying is preferably carried out in an oven; the drying temperature is preferably 80–230°C, more preferably 100–200°C, and even more preferably 120–150°C. This invention removes liquid lubricants through drying.

[0044] In this invention, the stretching is preferably uniaxial stretching or biaxial stretching.

[0045] In this invention, the uniaxial stretching ratio is preferably 2 to 9 times, more preferably 3 to 8 times, and even more preferably 4 to 7 times; the longitudinal tensile strength of the uniaxial stretching is preferably 10 to 50 MPa, more preferably 20 to 40 MPa, and even more preferably 30 MPa; the transverse tensile strength of the uniaxial stretching is preferably 0.1 to 2 MPa, more preferably 0.5 to 1.5 MPa; and the density of the first composite film obtained by uniaxial stretching is preferably 0.3 to 0.9 g / cm³. 3 More preferably, it is 0.4–0.8 g / cm³. 3 More preferably, it is 0.5–0.7 g / cm³. 3 .

[0046] In this invention, the longitudinal stretching ratio of the biaxial stretching is preferably 2 to 20 times, more preferably 5 to 15 times, and even more preferably 8 to 12 times; the transverse stretching ratio of the biaxial stretching is preferably 10 to 40 times, more preferably 15 to 35 times, and even more preferably 20 to 30 times; the longitudinal tensile strength of the biaxial stretching is preferably 20 to 80 MPa, more preferably 30 to 70 MPa, and even more preferably 40 to 60 MPa; the transverse tensile strength of the biaxial stretching is preferably 20 to 80 MPa, more preferably 30 to 70 MPa, and even more preferably 40 to 60 MPa; the density of the first composite film obtained by biaxial stretching is preferably 0.2 to 0.8 g / cm³. 3 More preferably, it is 0.3–0.7 g / cm³. 3 More preferably, it is 0.4–0.6 g / cm³. 3 .

[0047] After obtaining the first composite film, the present invention preferably combines n layers of the first composite film to obtain a wear-resistant layer.

[0048] In this invention, n is preferably ≥1, more preferably 2-5, and even more preferably 3-4. In this invention, the composite temperature is preferably 200-320℃, more preferably 250-300℃; the composite pressure is preferably 0.1-1MPa, more preferably 0.2-0.8MPa, and even more preferably 0.4-0.6MPa; the composite time is preferably 10-200s, more preferably 20-150s, and even more preferably 20-100s. In this invention, the composite is preferably performed on a flatbed press or a roller press.

[0049] In this invention, the thickness of the wear-resistant layer is preferably 90-400 μm, more preferably 150-250 μm; the thickness deviation of the wear-resistant layer is preferably ≤10 μm.

[0050] This invention constructs a wear-resistant layer by using a multi-layer composite method, which increases the thickness of the film while also increasing the uniformity of the thickness. During the composite process, the composite films can be stacked in opposite directions in the transverse direction, which can eliminate the deviation caused by equipment precision issues when preparing single-layer films.

[0051] In this invention, the raw materials for preparing the expanded layer preferably include 60-85% PTFE resin and 15-40% liquid lubricant by weight percentage.

[0052] In this invention, the PTFE resin is preferably a PTFE resin with a crystallinity of ≥97%; the liquid lubricant is preferably naphtha, white oil, or mineral oil. In this invention, the PTFE resin in the expanded layer is the main film-forming material, and the liquid lubricant acts as a pore-forming agent and also provides lubrication.

[0053] In this invention, the method for preparing the expanded layer preferably includes the following steps:

[0054] 1) After mixing PTFE resin and liquid lubricant, the mixture is dried to form granules, which are then pressed and extruded to obtain a second preform;

[0055] 2) The second preform obtained in step (2) is dried and stretched sequentially to obtain the second composite film;

[0056] 3) Composite the second composite film obtained in step (2) with n layers to obtain an expanded layer.

[0057] In this invention, PTFE resin and liquid lubricant are mixed and dried to form granules, which are then pressed and extruded to obtain a second preform. This invention does not have specific limitations on the specific mixing operation of the PTFE resin and liquid lubricant, as long as the components are mixed uniformly.

[0058] In this invention, the particle size of the granules is preferably 10-600 μm, more preferably 50-400 μm.

[0059] In this invention, the pressing is preferably performed in a plunger press. In this invention, the shape of the pressed product is preferably tubular or cylindrical. In this invention, the extrusion molding is preferably performed in a plunger extruder. This invention does not impose any specific limitations on the model of the plunger press and plunger extruder; commercially available products well-known to those skilled in the art can be used.

[0060] In this invention, the density of the second blank is preferably 1.4 to 1.8 g / cm³. 3 More preferably, it is 1.5–1.7 g / cm³. 3 Further preferred value is 1.6 g / cm³ 3 The thickness of the second blank is preferably 50-220 μm, more preferably 100-200 μm, and even more preferably 150-200 μm.

[0061] After obtaining the second preform, the present invention preferably dries and stretches the second preform sequentially to obtain the second composite film.

[0062] In this invention, the drying is preferably carried out in an oven; the drying temperature is preferably 80–230°C, more preferably 100–200°C, and even more preferably 120–150°C. This invention removes liquid lubricants through drying.

[0063] In this invention, the stretching is preferably uniaxial stretching or biaxial stretching.

[0064] In this invention, the uniaxial stretching ratio is preferably 3 to 9 times, more preferably 4 to 8 times, and even more preferably 5 to 7 times; the longitudinal tensile strength of the uniaxial stretching is preferably 10 to 40 MPa, more preferably 20 to 30 MPa; the transverse tensile strength of the uniaxial stretching is preferably 0.1 to 1.5 MPa, more preferably 0.5 to 1.0 MPa; and the density of the second composite film obtained by uniaxial stretching is preferably 0.2 to 0.8 g / cm³. 3 More preferably, it is 0.3–0.6 g / cm³. 3 .

[0065] In this invention, the longitudinal stretching ratio of the biaxial stretching is preferably 2 to 20 times, more preferably 5 to 15 times, and even more preferably 8 to 12 times; the transverse stretching ratio of the biaxial stretching is preferably 10 to 40 times, more preferably 15 to 35 times, and even more preferably 20 to 30 times; the longitudinal tensile strength of the biaxial stretching is preferably 20 to 80 MPa, more preferably 30 to 70 MPa, and even more preferably 40 to 60 MPa; the transverse tensile strength of the biaxial stretching is preferably 20 to 80 MPa, more preferably 30 to 70 MPa, and even more preferably 40 to 60 MPa; the density of the second composite membrane obtained by biaxial stretching is preferably 0.1 to 0.7 g / cm³. 3 More preferably, it is 0.3–0.5 g / cm³. 3 .

[0066] After obtaining the second composite film, the present invention preferably combines n layers of the second composite film to obtain an expanded layer.

[0067] In this invention, n is preferably ≥1, more preferably 2-5, and even more preferably 3-4. In this invention, the composite temperature is preferably 200-320℃, more preferably 250-300℃; the composite pressure is preferably 0.1-1MPa, more preferably 0.2-0.8MPa, and even more preferably 0.4-0.6MPa; the composite time is preferably 10-200s, more preferably 20-150s, and even more preferably 20-100s. In this invention, the composite is preferably performed on a flatbed press or a roller press.

[0068] The thickness of the expanded layer is preferably 200–600 μm, more preferably 300–500 μm; the thickness deviation of the expanded layer is preferably ≤10 μm.

[0069] In this invention, the thickness of the expanded layer is greater than that of the wear-resistant layer, which can better increase the leakage resistance of the sealing material. At the same time, the unique high-density fiber structure of the expanded body gives it strong creep resistance.

[0070] In this invention, the raw materials for preparing the modified layer, by weight percentage, include 60-80% PTFE resin, 10-39.5% liquid lubricant, and 0.5-10% thermoplastic fluoropolymer.

[0071] In this invention, the PTFE resin is preferably a PTFE resin with a crystallinity ≥97%; the liquid lubricant is preferably naphtha, white oil, or mineral oil; and the thermoplastic fluoropolymer is preferably one or more of polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene copolymer (ETFE), perfluoroethylene propylene (FEP), tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA), polyvinylidene fluoride (PVF), trifluorochloroethylene homopolymer and copolymer (PCTFE), and perfluorosulfonic acid resin (PFSA). In this invention, the PTFE resin in the modified layer is the main film-forming material, the liquid lubricant acts as a pore-forming agent and also provides lubrication, and the thermoplastic fluoropolymer can increase the interfacial adhesion, mainly used for bonding elastic materials.

[0072] In this invention, the method for preparing the modified layer preferably includes the following steps:

[0073] 1) PTFE resin, liquid lubricant and thermoplastic fluoropolymer are mixed and dried to form granules, which are then pressed and extruded to obtain a third preform;

[0074] 2) The third preform obtained in step (2) is dried and stretched sequentially to obtain the third composite film;

[0075] 3) Composite the third composite film obtained in step (2) with n layers to obtain the modified layer.

[0076] In this invention, PTFE resin, liquid lubricant, and thermoplastic fluoropolymer are mixed, dried to form granules, and then pressed and extruded to obtain a third preform. This invention does not impose specific limitations on the mixing process of the PTFE resin, liquid lubricant, and thermoplastic fluoropolymer, as long as the components are mixed uniformly.

[0077] In this invention, the particle size of the granules is preferably 10-600 μm, more preferably 50-400 μm.

[0078] In this invention, the pressing is preferably performed in a plunger press. In this invention, the shape of the pressed product is preferably tubular or cylindrical. In this invention, the extrusion molding is preferably performed in a plunger extruder. This invention does not impose any specific limitations on the model of the plunger press and plunger extruder; commercially available products well-known to those skilled in the art can be used.

[0079] In this invention, the density of the third preform is preferably 1.4 to 1.8 g / cm³. 3 More preferably, it is 1.5–1.7 g / cm³. 3 Further preferred value is 1.6 g / cm³ 3The thickness of the third blank is preferably 50-150 μm, more preferably 80-120 μm.

[0080] After obtaining the third preform, the present invention preferably dries and stretches the third preform sequentially to obtain the third composite film.

[0081] In this invention, the drying is preferably carried out in an oven; the drying temperature is preferably 80–230°C, more preferably 100–200°C, and even more preferably 120–150°C. This invention removes liquid lubricants through drying.

[0082] In this invention, the stretching is preferably uniaxial stretching or biaxial stretching.

[0083] In this invention, the uniaxial stretching ratio is preferably 3 to 9 times, more preferably 4 to 8 times, and even more preferably 5 to 7 times; the longitudinal tensile strength of the uniaxial stretching is preferably 10 to 40 MPa, more preferably 20 to 30 MPa; the transverse tensile strength of the uniaxial stretching is preferably 0.1 to 1.5 MPa, more preferably 0.5 to 1.0 MPa; and the density of the third composite membrane obtained by uniaxial stretching is preferably 0.2 to 0.8 g / cm³. 3 More preferably, it is 0.3–0.6 g / cm³. 3 .

[0084] In this invention, the longitudinal stretching ratio of the biaxial stretching is preferably 2 to 20 times, more preferably 5 to 15 times, and even more preferably 8 to 12 times; the transverse stretching ratio of the biaxial stretching is preferably 10 to 40 times, more preferably 15 to 35 times, and even more preferably 20 to 30 times; the longitudinal tensile strength of the biaxial stretching is preferably 20 to 80 MPa, more preferably 30 to 70 MPa, and even more preferably 40 to 60 MPa; the transverse tensile strength of the biaxial stretching is preferably 20 to 80 MPa, more preferably 30 to 70 MPa, and even more preferably 40 to 60 MPa; the density of the third composite membrane obtained by biaxial stretching is preferably 0.1 to 0.7 g / cm³. 3 More preferably, it is 0.3–0.5 g / cm³. 3 .

[0085] After obtaining the third composite membrane, the present invention preferably combines n layers of the third composite membrane to obtain a modified layer.

[0086] In this invention, n is preferably ≥1, more preferably 2-5, and even more preferably 3-4. In this invention, the composite temperature is preferably 200-320℃, more preferably 250-300℃; the composite pressure is preferably 0.1-1MPa, more preferably 0.2-0.8MPa, and even more preferably 0.4-0.6MPa; the composite time is preferably 10-200s, more preferably 20-150s, and even more preferably 20-100s. In this invention, the composite is preferably performed on a flatbed press or a roller press.

[0087] The thickness of the modified layer is preferably 60–200 μm, more preferably 80–150 μm; the thickness deviation of the modified layer is preferably ≤10 μm.

[0088] In this invention, the PTFE resin and liquid lubricant in the wear-resistant layer, the expanded layer and the modified layer have the same function. Adding inorganic materials to the wear-resistant layer can increase wear resistance, and adding thermoplastic fluoropolymers to the modified layer can provide adhesion, but it still has the function of an expanded layer, only the expansion effect is weakened.

[0089] In this invention, when the preferred method for preparing the expanded polytetrafluoroethylene (PTFE) layer is to separately prepare wear-resistant layer sheets, expanded layer sheets, and modified layer sheets from the raw materials of the wear-resistant layer, expanded layer, and modified layer, and then stack the wear-resistant layer sheets, expanded layer sheets, and modified layer sheets, and sequentially dry and stretch them to obtain the expanded PTFE layer, the wear-resistant layer sheet corresponds to the aforementioned first preform, the expanded layer sheet corresponds to the aforementioned second preform, and the modified layer sheet corresponds to the aforementioned third preform. In this invention, because the above preparation method uses three-layer extruded sheets that can be bonded together in an oven while the lubricant is evaporated, there is no need for lamination on a flatbed press or roller press after uniaxial or biaxial stretching.

[0090] In this invention, the drying is preferably carried out in an oven; the drying temperature is preferably 80–230°C, more preferably 100–200°C, and even more preferably 120–150°C. This invention removes liquid lubricants through drying.

[0091] In this invention, the stretching is preferably uniaxial stretching or biaxial stretching.

[0092] In this invention, the uniaxial stretching ratio is preferably 2 to 9 times, more preferably 4 to 8 times, and even more preferably 5 to 7 times; the longitudinal tensile strength of the uniaxial stretching is preferably 10 to 50 MPa, more preferably 20 to 30 MPa; the transverse tensile strength of the uniaxial stretching is preferably 0.1 to 1.5 MPa, more preferably 0.5 to 1.0 MPa; and the density of the expanded polytetrafluoroethylene layer obtained by uniaxial stretching is preferably 0.3 to 0.9 g / cm³.3 More preferably, it is 0.4–0.8 g / cm³. 3 .

[0093] In this invention, the longitudinal stretching ratio of the biaxial stretching is preferably 2 to 20 times, more preferably 5 to 15 times, and even more preferably 8 to 12 times; the transverse stretching ratio of the biaxial stretching is preferably 10 to 40 times, more preferably 15 to 35 times, and even more preferably 20 to 30 times; the longitudinal tensile strength of the biaxial stretching is preferably 20 to 80 MPa, more preferably 30 to 70 MPa, and even more preferably 40 to 60 MPa; the transverse tensile strength of the biaxial stretching is preferably 20 to 80 MPa, more preferably 30 to 70 MPa, and even more preferably 40 to 60 MPa; the density of the expanded polytetrafluoroethylene layer obtained by biaxial stretching is preferably 0.2 to 0.8 g / cm³. 3 More preferably, it is 0.3–0.6 g / cm³. 3 .

[0094] In this invention, the thickness of the expanded polytetrafluoroethylene layer is preferably 210-1200 μm, more preferably 300-1000 μm, and even more preferably 400-800 μm; the thickness deviation of the expanded polytetrafluoroethylene layer is preferably ≤10 μm.

[0095] In this invention, the sealing material preferably further includes an elastomer layer, which is preferably located between the expanded polytetrafluoroethylene layer and the pressure-sensitive adhesive layer. In this invention, the elastomer layer provides sufficient sealing preload, compensating for the wear of the pure expanded polytetrafluoroethylene sealing ring and significantly improving sealing performance.

[0096] In this invention, the raw materials for preparing the elastomer layer preferably include one or more of polyurethane elastomers, polyurethane rubber, curable siloxanes, fluorosilicone rubber, perfluororubber, and perfluoropolyether silicone rubber, more preferably polyurethane elastomers or polyurethane rubber, and even more preferably polyurethane elastomers.

[0097] In this invention, the raw materials for preparing the polyurethane elastomer preferably include polyurethane prepolymer, crosslinking agent, accelerator and chain extender, more preferably 50-100 wt.% polytetrahydrofuran ether polyurethane prepolymer, 0-20 wt.% crosslinking agent, 0-10 wt.% accelerator and 0-20 wt.% chain extender.

[0098] In this invention, the polyurethane prepolymer is preferably a polymer compound generated by the reaction of polyols and isocyanates, more preferably a polyether-type polyurethane prepolymer; the polyether-type polyurethane prepolymer is preferably a polyoxypropylene ether polyurethane prepolymer, a polytetrahydrofuran ether polyurethane prepolymer, or a polycarbonate polyurethane prepolymer, more preferably a polytetrahydrofuran ether polyurethane prepolymer. This invention does not impose any particular limitation on the preparation method of the polyurethane elastomer; it can be prepared using methods skilled in the art or commercially available products. The polyurethane elastomer prepared using the above-mentioned polyurethane prepolymer exhibits better tear resistance and resilience, and is therefore more suitable as a sealing material.

[0099] In this invention, the crosslinking agent preferably includes one or more of hexamethylene diisocyanate, dimethylolpropionic acid, neopentyl glycol, and ethylenediamine, more preferably dimethylolpropionic acid. In this invention, the crosslinking agent exhibits better compatibility, reaction rate, and crosslinking density with the polyurethane prepolymer, enabling the polyurethane prepolymer to undergo a crosslinking reaction, thereby forming a network structure.

[0100] In this invention, the accelerator preferably includes one or more of dibutyltin dilaurate, stannous octoate, triethyltin acetate, and lead octoate, more preferably dibutyltin dilaurate. In this invention, the accelerator can control the reaction rate, has good stability and low toxicity, and can accelerate the crosslinking reaction of polyurethane prepolymers, thereby shortening processing time and improving production efficiency.

[0101] In this invention, the chain extender is preferably a small molecule alcohol, water, or amine. In this invention, the chain extender can increase the molecular weight and elasticity of the prepolymer.

[0102] In this invention, when the polyurethane prepolymer is a polytetrahydrofuran ether polyurethane prepolymer, the preferred method for preparing the elastomer layer is as follows:

[0103] I. Tetrahydrofuran and an epoxy compound are subjected to ring-opening polymerization in the presence of a catalyst to obtain polytetrahydrofuran ether polyol. Then, the polytetrahydrofuran ether polyol is mixed with cyanate ester and reacted to obtain polytetrahydrofuran ether polyurethane prepolymer.

[0104] II. Mix the polytetrahydrofuran ether polyurethane prepolymer, crosslinking agent, accelerator and chain extender obtained in step I to obtain a mixture;

[0105] III. The mixture obtained in step II is sequentially melted, extruded and calendered to obtain an elastomer layer.

[0106] The present invention preferably involves ring-opening polymerization of tetrahydrofuran and an epoxy compound in the presence of a catalyst to obtain polytetrahydrofuran ether polyol, and then reacting the polytetrahydrofuran ether polyol with a cyanate ester to obtain a polytetrahydrofuran ether polyurethane prepolymer.

[0107] In this invention, the epoxy compound is preferably propylene oxide or ethylene oxide; the catalyst is preferably sodium hydroxide or potassium hydroxide; and the cyanate is preferably hexamethylene isocyanate, methyl isocyanate, or phenyl isocyanate. In this invention, the mass ratio of the polytetrahydrofuran ether polyol to the isocyanate is preferably 1:(1-3), more preferably 1:2. In this invention, the tetrahydrofuran ring structure in the polytetrahydrofuran ether molecular chain has similar chemical properties to the fluorine atom structure in the polytetrafluoroethylene molecular chain, and can form certain interaction forces.

[0108] After obtaining the polytetrahydrofuran ether polyurethane prepolymer, the present invention mixes the polytetrahydrofuran ether polyurethane prepolymer, crosslinking agent, accelerator and chain extender to obtain a mixture.

[0109] After obtaining the mixture, the present invention sequentially melts, extrudes, and calenders the mixture to obtain an elastomer layer. In the present invention, the extrusion speed is preferably 1–30 m / min, more preferably 5–25 m / min, and even more preferably 10–20 m / min. The present invention does not impose any special limitations on the specific operations of melting, extrusion, and calendering, as long as the thickness of the elastomer layer meets the requirements.

[0110] In this invention, the thickness of the elastomer layer is preferably 210-800 μm, more preferably 300-700 μm, and even more preferably 400-600 μm; the thickness deviation of the elastomer layer is preferably ≤10 μm.

[0111] In this invention, the raw materials for preparing the pressure-sensitive adhesive layer preferably include polytetrahydrofuran ether polyurethane prepolymer, tackifier, filler, and solvent, more preferably 10-40 wt.% polytetrahydrofuran ether polyurethane prepolymer, 10-30 wt.% tackifier, 10-50 wt.% filler, and 30-60 wt.% solvent. In this invention, the tackifier is preferably a polymeric tackifier, a phenolic tackifier, or a rosin-based tackifier, more preferably a polymeric tackifier; the filler is preferably a silicate, carbonate, or oxide, more preferably a silicate; the solvent is preferably toluene, ethyl acetate, or ethanol, more preferably toluene. In this invention, the polytetrahydrofuran ether polyurethane prepolymer is the main adhesive component and has good compatibility with the elastomer layer; the tackifier can improve adhesion; the filler can adjust the hardness and viscosity of the pressure-sensitive adhesive; and the solvent plays a role in dissolving and adjusting viscosity.

[0112] In this invention, the preferred method for preparing the pressure-sensitive adhesive layer is as follows:

[0113] 1. Tetrahydrofuran and an epoxy compound are subjected to ring-opening polymerization in the presence of a catalyst to obtain polytetrahydrofuran ether polyol. Then, the polytetrahydrofuran ether polyol is mixed with cyanate ester and reacted to obtain polytetrahydrofuran ether polyurethane prepolymer.

[0114] 2. The polytetrahydrofuran ether polyurethane prepolymer, tackifier, filler and solvent obtained in step one are mixed and reacted to obtain a pressure-sensitive adhesive solution;

[0115] 3. The pressure-sensitive adhesive solution obtained in step 2 is coated and dried sequentially to obtain a pressure-sensitive adhesive layer; the drying method is preferably hot air drying, radiation drying or roller drying.

[0116] In this invention, tetrahydrofuran and an epoxy compound are preferably subjected to ring-opening polymerization in the presence of a catalyst to obtain polytetrahydrofuran ether polyol. Then, the polytetrahydrofuran ether polyol is mixed and reacted with a cyanate ester to obtain a polytetrahydrofuran ether polyurethane prepolymer. In this invention, the specific types and amounts of the raw materials are preferably the same as described above, and will not be repeated here.

[0117] After obtaining the polytetrahydrofuran ether polyurethane prepolymer, the present invention preferably mixes the polytetrahydrofuran ether polyurethane prepolymer, tackifier, filler and solvent and reacts them to obtain a pressure-sensitive adhesive solution.

[0118] In this invention, the mixing is preferably carried out under stirring conditions, and the stirring speed is preferably 300-600 rpm.

[0119] In this invention, the reaction temperature is preferably 20-150°C, more preferably 50-100°C; the reaction time is preferably 2-6 hours, more preferably 3-5 hours.

[0120] After obtaining the pressure-sensitive adhesive solution, the present invention preferably coats and dries the pressure-sensitive adhesive solution sequentially to obtain a pressure-sensitive adhesive layer. In the present invention, the drying method is preferably hot air drying, radiation drying, or roller drying.

[0121] In this invention, the thickness of the pressure-sensitive adhesive layer is preferably 1 to 20 μm, more preferably 5 to 15 μm, and even more preferably 10 μm; the thickness deviation of the pressure-sensitive adhesive is ≤2 μm.

[0122] This invention provides a method for preparing the sealing material described in the above technical solution, comprising: using an expanded polytetrafluoroethylene layer as a base film, coating a pressure-sensitive adhesive solution extruded by a screw extruder onto the expanded polytetrafluoroethylene layer, and obtaining the sealing material after drying;

[0123] When the sealing material includes an elastomer layer, an expanded polytetrafluoroethylene (PTFE) layer is used as the base film. The elastomer layer is extruded onto the expanded PTFE layer using a screw extruder. After the elastomer layer is dried on the expanded PTFE layer, a pressure-sensitive adhesive solution extruded by the screw extruder is coated onto the elastomer layer. After drying, the sealing material is obtained.

[0124] The present invention does not impose any special limitations on the specific parameters in the preparation method, which can be determined based on the technical common sense of those skilled in the art.

[0125] The highly elastic, creep-resistant composite sealing material prepared in this invention provides sufficient sealing preload through the elastomer, compensating for the wear of the pure expanded polytetrafluoroethylene (PTFE) sealing ring and significantly improving sealing performance. The expanded PTFE layer exhibits good wear resistance, further reducing wear. Combined with the adhesion between the pressure-sensitive adhesive and the sealing surface, this greatly increases the reliability and lifespan of the seal. Furthermore, the materials used in this invention possess excellent chemical resistance, meeting the needs of helicopters operating in complex environments.

[0126] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0127] Example 1

[0128] A sealing material is prepared by: placing a 210μm expanded polytetrafluoroethylene (PTFE) layer as a base film on a conveyor belt; extruding an elastomer layer onto the expanded PTFE layer using a screw extruder; drying the 210μm thick elastomer layer on the expanded PTFE layer at 80°C for 5 minutes; then coating the elastomer layer with a pressure-sensitive adhesive solution extruded by the screw extruder onto the elastomer layer, with a pressure-sensitive adhesive layer thickness of 10μm; and finally obtaining a 430μm sealing material after drying.

[0129] The method for preparing the elastomer layer is as follows:

[0130] I. Tetrahydrofuran and an epoxy compound are subjected to ring-opening polymerization in the presence of a catalyst to obtain polytetrahydrofuran ether polyol. Then, the polytetrahydrofuran ether polyol is mixed with cyanate ester and reacted to obtain polytetrahydrofuran ether polyurethane prepolymer.

[0131] II. Mix 85 wt.% of the polytetrahydrofuran ether polyurethane prepolymer obtained in step I, 5 wt.% of dimethylolpropionic acid, 5 wt.% of dibutyltin dilaurate, and 5 wt.% of water to obtain a mixture;

[0132] III. The mixture obtained in step II is sequentially melted, extruded, and calendered to obtain an elastomer layer; the extrusion speed is 10 m / min.

[0133] The method for preparing the pressure-sensitive adhesive layer is as follows:

[0134] 1. Tetrahydrofuran and an epoxy compound are subjected to ring-opening polymerization in the presence of a catalyst to obtain polytetrahydrofuran ether polyol. Then, the polytetrahydrofuran ether polyol is mixed with cyanate ester and reacted to obtain polytetrahydrofuran ether polyurethane prepolymer.

[0135] 2. Mix 40 wt.% of the polytetrahydrofuran ether polyurethane prepolymer obtained in step 1, 20 wt.% of the polymer tackifier, 20 wt.% of the silicate, and 20 wt.% of the toluene, and react them to obtain a pressure-sensitive adhesive solution;

[0136] 3. The pressure-sensitive adhesive solution obtained in step 2 is coated and dried with hot air in sequence to obtain a pressure-sensitive adhesive layer.

[0137] The performance of the sealing material prepared in Example 1 was tested, and the results are shown in Table 1:

[0138] Table 1. Performance of the sealing material prepared in Example 1

[0139] performance Performance indicators Experimental methods thickness 430μm GB / T7125-1999 density <![CDATA[0.130g / cm 3 ]]> GB / T1033-1996 Tensile strength 4MPa GB / T1040-2006 Elongation at break 500％ GB / T1040-2006 180° peel strength, 23°C 6N / m GB / T2792-1998

[0140] Example 2

[0141] A sealing material is prepared by: placing a 900μm expanded polytetrafluoroethylene (PTFE) layer as a base film on a conveyor belt; extruding an elastomer layer onto the expanded PTFE layer using a screw extruder; drying the 210μm thick elastomer layer on the expanded PTFE layer at 80°C for 5 minutes; then coating the elastomer layer with a pressure-sensitive adhesive solution extruded by the screw extruder onto the elastomer layer, with a pressure-sensitive adhesive layer thickness of 10μm; and finally obtaining a 1120μm sealing material after drying.

[0142] The method for preparing the elastomer layer is as follows:

[0143] I. Tetrahydrofuran and an epoxy compound are subjected to ring-opening polymerization in the presence of a catalyst to obtain polytetrahydrofuran ether polyol. Then, the polytetrahydrofuran ether polyol is mixed with cyanate ester and reacted to obtain polytetrahydrofuran ether polyurethane prepolymer.

[0144] II. Mix 50 wt.% of the polytetrahydrofuran ether polyurethane prepolymer obtained in step I, 20 wt.% of dimethylolpropionic acid, 10 wt.% of hexamethylene diisocyanate and 20 wt.% of water to obtain a mixture;

[0145] III. The mixture obtained in step II is sequentially melted, extruded, and calendered to obtain an elastomer layer; the extrusion speed is 30 m / min.

[0146] The method for preparing the pressure-sensitive adhesive layer is as follows:

[0147] 1. Tetrahydrofuran and an epoxy compound are subjected to ring-opening polymerization in the presence of a catalyst to obtain polytetrahydrofuran ether polyol. Then, the polytetrahydrofuran ether polyol is mixed with cyanate ester and reacted to obtain polytetrahydrofuran ether polyurethane prepolymer.

[0148] 2. Mix 20 wt.% of the polytetrahydrofuran ether polyurethane prepolymer obtained in step 1, 30 wt.% of the polymer tackifier, 30 wt.% of the silicate, and 20 wt.% of the toluene, and react them to obtain a pressure-sensitive adhesive solution;

[0149] 3. The pressure-sensitive adhesive solution obtained in step 2 is coated and dried with hot air in sequence to obtain a pressure-sensitive adhesive layer.

[0150] The performance of the sealing material prepared in Example 2 was tested, and the results are shown in Table 2:

[0151] Table 2. Performance of the sealing material prepared in Example 2

[0152] performance Performance indicators Test methods thickness 1120μm GB / T7125-1999 density <![CDATA[0.12g / cm 3 ]]> GB / T1033-1996 Tensile strength 5MPa GB / T1040-2006 Elongation at break 650％ GB / T1040-2006 180° peel strength, 23°C 7N / m GB / T2792-1998

[0153] Example 3

[0154] A method for preparing an expanded polytetrafluoroethylene layer is as follows:

[0155] (1) A mixture of 65 wt.% Shandong Dongyue Company D204PTFE resin, 25 wt.% white oil, and 10 wt.% cerium oxide was thoroughly mixed. The granules were then extruded into tubular or cylindrical shapes using a plunger press, and then extruded through a plunger extrusion die to produce a product with a density of 1.8 g / cm³. 3 A first preform with a thickness of 300 μm; lubricant removed by evaporation in an oven at 230 °C; uniaxial stretching with a magnification of 2 times and a density of 0.9 g / cm³. 3 The longitudinal tensile strength is 20MPa, the transverse tensile strength is 2MPa, and a wear-resistant layer with a thickness of 300μm and a thickness deviation of ≤10μm is obtained.

[0156] (2) A mixture of 75 wt.% Shandong Dongyue Company D204PTFE resin and 25 wt.% white oil was thoroughly mixed, and the granules were extruded into tubular or cylindrical shapes using a plunger press. The mixture was then extruded through a plunger extruder and die to produce a product with a density of 1.4 g / cm³. 3The second preform, 300 μm thick, had its lubricant removed by evaporation in an oven at 230°C; it underwent uniaxial stretching with a magnification of 2 times and a density of 0.5 g / cm³. 3 The longitudinal tensile strength is 20MPa, the transverse tensile strength is 1MPa, and an expanded layer with a thickness of 300μm and a thickness deviation of ≤10μm is obtained.

[0157] (3) A mixture of 75 wt.% Shandong Dongyue Company D204PTFE resin, 15 wt.% white oil, and 5 wt.% FEP was thoroughly mixed. The granules were then extruded into tubular or cylindrical shapes using a plunger press, and finally extruded through a plunger extrusion die to produce a product with a density of 1.6 g / cm³. 3 A third preform with a thickness of 300 μm was prepared by removing the lubricant through evaporation in an oven at 230 °C; the magnification was 2 times during uniaxial stretching, and the density was 0.9 g / cm³. 3 The longitudinal tensile strength is 20MPa, the transverse tensile strength is 1.5MPa, and a modified layer with a thickness of 200μm and a thickness deviation of ≤10μm is obtained.

[0158] (4) The above wear-resistant layer, expanded layer and modified layer are combined into a single material in a flat press at a temperature of 320℃, a pressure of 0.1MPa and a time of 50 seconds to obtain an expanded polytetrafluoroethylene layer with a thickness of 700μm and a thickness deviation of ≤10μm.

[0159] The properties of the expanded polytetrafluoroethylene layer prepared in Example 3 were tested, and the results are shown in Table 3:

[0160] Table 3. Performance of the expanded polytetrafluoroethylene layer prepared in Example 3

[0161] performance Performance indicators Test methods thickness 700μm GB / T7125-1999 Longitudinal tensile strength 20MPa GB / T1040-2006 Transverse tensile strength 2MPa GB / T1040-2006

[0162] Example 4

[0163] A method for preparing an expanded polytetrafluoroethylene layer is as follows:

[0164] (1) A mixture of 70 wt.% Shandong Dongyue Company D204PTFE resin, 25 wt.% white oil, and 5 wt.% cerium oxide was thoroughly mixed. The granules were then extruded into tubular or cylindrical shapes using a plunger press, and finally extruded through a plunger extrusion die to produce a product with a density of 1.7 g / cm³. 3 A first preform with a thickness of 100 μm was prepared; the lubricant was removed by evaporation in an oven at a temperature of 230 °C; biaxial stretching was performed with a longitudinal magnification of 6 times and a transverse magnification of 20 times, resulting in a density of 0.3 g / cm³. 3 The longitudinal tensile strength is 50MPa, the transverse tensile strength is 60MPa, and a wear-resistant layer with a thickness of 120μm and a thickness deviation of ≤10μm is obtained.

[0165] (2) A mixture of 70 wt.% Shandong Dongyue Company D204PTFE resin and 30 wt.% white oil was thoroughly mixed, and the granules were extruded into tubular or cylindrical shapes using a plunger press. The mixture was then extruded through a plunger extruder and die to produce a product with a density of 1.6 g / cm³. 3 The second preform, 200 μm thick, was prepared by evaporating the lubricant in an oven at 230°C; it was then subjected to biaxial stretching with a longitudinal magnification of 5x and a transverse magnification of 30x, resulting in a density of 0.2 g / cm³. 3 The longitudinal tensile strength is 40MPa, the transverse tensile strength is 50MPa, and an expanded layer with a thickness of 220μm and a thickness deviation of ≤10μm is obtained.

[0166] (3) A mixture of 65 wt.% Shandong Dongyue Company D204PTFE resin, 25 wt.% white oil, and 5 wt.% FEP was thoroughly mixed. The granules were then extruded into tubular or cylindrical shapes using a plunger press, and finally extruded through a plunger extrusion die to produce a product with a density of 1.6 g / cm³. 3 The third preform, 100 μm thick, was prepared by evaporating the lubricant in an oven at 230°C; it was then biaxially stretched with a longitudinal magnification of 3x and a transverse magnification of 25x, resulting in a density of 0.35 g / cm³. 3 The longitudinal tensile strength is 45MPa, the transverse tensile strength is 55MPa, and a modified layer with a thickness of 120μm and a thickness deviation of ≤10μm is obtained.

[0167] (4) The above-mentioned wear-resistant layer, expanded layer and modified layer are combined into a single material in a flat press at a temperature of 320℃, a pressure of 0.3MPa and a time of 200 seconds to obtain an expanded polytetrafluoroethylene layer with a thickness of 800μm and a thickness deviation of ≤10μm.

[0168] The properties of the expanded polytetrafluoroethylene layer prepared in Example 4 were tested, and the results are shown in Table 4:

[0169] Table 4. Performance of the expanded polytetrafluoroethylene layer prepared in Example 4

[0170] performance Performance indicators Test methods thickness 800μm GB / T7125-1999 Longitudinal tensile strength 50MPa GB / T1040-2006 Transverse tensile strength 50MPa GB / T1040-2006

[0171] Figure 1 This is a schematic diagram of the structure of the sealing material provided by the present invention. Figure 1 In the middle, 10 is the expanded polytetrafluoroethylene layer, 20 is the middle elastomer layer, and 30 is the bottom layer coated with pressure-sensitive adhesive.

[0172] Figure 2 This is a schematic diagram of the expanded polytetrafluoroethylene layer in the sealing material provided by the present invention. Figure 2 In the diagram, 101 is the wear-resistant layer, 102 is the expanded layer, and 103 is the modified layer. Figure 2 It can be seen that the expanded polytetrafluoroethylene layer has a network structure with microfibers, which gives it excellent flexibility and resilience. This sealing material exhibits excellent sealing performance in sealing parts under low pressure, and also has excellent corrosion resistance, non-aging properties, creep resistance, low coefficient of friction, and high tensile strength.

[0173] Figure 3 This is a uniaxial tensile SEM image of the expanded polytetrafluoroethylene layer prepared in Example 3 of the present invention. Figure 3 In the diagram, 1001 represents the fibril and 1002 represents the polymer node. Figure 4 This is a uniaxial tensile SEM image of the expanded polytetrafluoroethylene layer prepared in Example 4 of the present invention. Figure 4 In the diagram, 2001 represents the fibril, and 2002 represents the polymer node. (The rest of the text appears to be a fragment and doesn't translate directly.) Figure 3 and Figure 4 It can be seen that the typical properties of this structure include an average fibril length of 1–25 μm between nodes and a void volume of 30–95%.

[0174] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A sealing material, comprising an expanded polytetrafluoroethylene layer and a pressure-sensitive adhesive layer stacked sequentially from top to bottom; The expanded polytetrafluoroethylene layer includes a wear-resistant layer, an expanded layer, and a modified layer stacked sequentially from top to bottom; The raw materials for preparing the wear-resistant layer, by weight percentage, include 60-80% PTFE resin, 10-39.5% liquid lubricant, and 0.5-10% inorganic oxide; the raw materials for preparing the expanded layer include 60-85% PTFE resin and 15-40% liquid lubricant; the raw materials for preparing the modified layer include 60-80% PTFE resin, 10-39.5% liquid lubricant, and 0.5-10% thermoplastic fluoropolymer. The raw materials for preparing the pressure-sensitive adhesive layer include polytetrahydrofuran ether polyurethane prepolymer, tackifier, filler, and solvent; the tackifier is a phenolic tackifier or a rosin-based tackifier, the filler is a silicate, carbonate, or oxide, and the solvent is toluene, ethyl acetate, or ethanol; The sealing material further includes an elastomer layer, which is located between the expanded polytetrafluoroethylene layer and the pressure-sensitive adhesive layer; the raw materials for preparing the elastomer layer include one or more of polyurethane elastomer, curable siloxane, fluorosilicone rubber, perfluororubber and perfluoropolyether silicone rubber.

2. The sealing material according to claim 1, characterized in that, The thickness of the expanded polytetrafluoroethylene layer is 300~1000μm, and the thickness deviation of the expanded polytetrafluoroethylene layer is ≤10μm; the thickness of the elastomer layer is 210~800μm, and the thickness deviation of the elastomer layer is ≤10μm; the thickness of the pressure-sensitive adhesive layer is 1~20μm, and the thickness deviation of the pressure-sensitive adhesive is ≤2μm.

3. The sealing material according to claim 1, characterized in that, The PTFE resin is a PTFE resin with a crystallinity ≥97%; the liquid lubricant is naphtha, white oil, or mineral oil; the inorganic oxide is one or more of silicon dioxide, alumina, and rare earth oxides; the thermoplastic fluoropolymer is one or more of polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, perfluoroethylene propylene, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, polyvinylidene fluoride, trifluorochloroethylene homopolymer and copolymer, and perfluorosulfonic acid resin.

4. The sealing material according to claim 1, characterized in that, The preparation method of the expanded polytetrafluoroethylene layer is to prepare a wear-resistant layer, an expanded layer and a modified layer separately, dry and stretch them, and then combine the wear-resistant layer, the expanded layer and the modified layer to obtain the expanded polytetrafluoroethylene layer. Alternatively, the raw materials for the wear-resistant layer, the expanded layer, and the modified layer can be prepared into wear-resistant layer sheets, expanded layer sheets, and modified layer sheets respectively. Then, the wear-resistant layer sheets, expanded layer sheets, and modified layer sheets are stacked together and dried and stretched in sequence to obtain an expanded polytetrafluoroethylene layer.

5. The sealing material according to claim 1, characterized in that, The raw materials for preparing the pressure-sensitive adhesive layer are 10-40 wt.% polytetrahydrofuran ether polyurethane prepolymer, 10-30 wt.% tackifier, 10-50 wt.% filler, and 30-60 wt.% solvent.

6. A method for preparing the sealing material according to any one of claims 1 to 5, comprising: Using expanded polytetrafluoroethylene (PTFE) layer as the base film, pressure-sensitive adhesive solution extruded by a screw extruder is coated onto the expanded PTFE layer, and after drying, a sealing material is obtained. When the sealing material includes an elastomer layer, an expanded polytetrafluoroethylene (PTFE) layer is used as the base film. The elastomer layer is extruded onto the expanded PTFE layer using a screw extruder. After the elastomer layer is dried on the expanded PTFE layer, a pressure-sensitive adhesive solution extruded by the screw extruder is coated onto the elastomer layer. After drying, the sealing material is obtained.

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