A high-performance rubber-plastic composite sealing strip for new energy vehicles and a preparation process thereof

Abstract

The application relates to the technical field of rubber products, and discloses a high-performance rubber-plastic composite sealing strip for new energy vehicles and a preparation process thereof. The sealing strip is composed of dense rubber mixing rubber and sponge rubber mixing rubber which are co-extruded and attached. Maleic anhydride grafted EPDM rubber and silane coupling agent are used to realize in-situ reaction, so that the covalent bond is formed between the aluminum hydroxide flame retardant and the rubber matrix, the mechanical strength of the material is maintained while the flame retardant property is ensured, the dielectric loss factor is adjusted by combining polyethylene glycol and high wear-resistant furnace black, the microwave heating rate is matched with the dense rubber, synchronous cross-interface co-vulcanization is realized at the interface of the two rubber layers, the time nodes of cross-linking and foaming kinetics are matched in the preparation process, the cross-linking network is established before a large amount of foaming, and a closed cell structure is formed. The in-situ coupling enhancement and microwave dielectric matching mechanism are used, the high flame retardant property and the mechanical strength are maintained, synchronous vulcanization across the interface is realized, and the composite delamination is prevented.

Description

Technical Field

[0001] This invention relates to the field of rubber product technology, specifically to a high-performance rubber-plastic composite sealing strip for new energy vehicles and its preparation process. Background Technology

[0002] The widespread adoption of new energy vehicles has placed more stringent demands on the overall performance of vehicle body sealing strips. Currently, automotive sealing strips typically use EPDM rubber as the base material and are manufactured through a dual-composite co-extrusion process of dense rubber and sponge rubber, as well as a microwave continuous vulcanization process. In addition to meeting basic requirements for dustproofing, waterproofing, and shock absorption and rebound, sealing materials for new energy vehicles must also comply with more stringent vehicle flame retardant safety regulations.

[0003] To achieve the target flame retardant rating, the current common practice is to mix a large amount of inorganic flame retardant into the dense rubber formulation. This treatment method disrupts the original mechanical balance of the rubber material. There is a problem of poor compatibility between a large amount of high-rigidity inorganic powder and the non-polar EPDM rubber matrix. The powder particles are difficult to uniformly integrate into the macromolecular network. Under stress, stress concentration will occur at the phase interface, resulting in a significant decrease in the tensile strength and tear strength of the modified rubber compound.

[0004] Meanwhile, the addition of high-filler polar inorganic flame retardants alters the electromagnetic properties of the dense rubber, causing its dielectric loss factor to rise sharply in the microwave alternating electric field. In actual co-extrusion microwave continuous vulcanization production lines, the rate at which the dense rubber layer absorbs microwave heat far exceeds that of the conventionally formulated sponge rubber layer. This difference in dielectric properties leads to asynchronous temperature rises at the bonding interface between the two rubber materials. The dense rubber layer reaches the activation temperature first and begins to crosslink, while the sponge rubber layer remains at a lower temperature. The time difference in the vulcanization reaction hinders the mutual diffusion of macromolecular chain segments on both sides of the interface and the establishment of cross-interface covalent bonds, ultimately resulting in insufficient interlayer bonding of the product. During long-term use of the vehicle, tearing and delamination are highly likely to occur.

[0005] In addition, during the foaming process of hot air and microwave, the sponge layer generally faces the process difficulty of matching the cross-linking reaction with the foaming kinetics. If the rubber matrix has not yet established an initial cross-linking network with a certain physical strength when the foaming agent produces gas and expands, the disorderly expanding gas will easily break through the weak cell walls, and adjacent cells will merge to form interconnected pores. This structural defect will lead to a decrease in the compressive strength of the sponge layer and an increase in the permanent compression deformation rate, which will directly affect the long-term rebound bonding effect of the sealing strip. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a high-performance rubber-plastic composite sealing strip for new energy vehicles and its preparation process. It solves the problems of decreased physical and mechanical strength of existing composite sealing strips during high-filling flame-retardant modification, as well as the interface delamination caused by the difference in dielectric properties between the solid rubber and the sponge rubber during microwave continuous vulcanization.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a high-performance rubber-plastic composite sealing strip for new energy vehicles, wherein the sealing strip is composed of co-extruded and laminated dense rubber compound and sponge rubber compound; The dense rubber compound is made from the following raw materials in parts by weight: 80-120 parts of unmodified EPDM rubber, 5-15 parts of maleic anhydride-grafted EPDM rubber, 40-60 parts of fast-extrusion furnace black, 40-60 parts of aluminum hydroxide, 10-20 parts of ammonium polyphosphate, 5-10 parts of melamine cyanurate, 1-3 parts of vinyltriethoxysilane, 30-50 parts of hydrogenated petroleum heavy alkane fraction, 4-6 parts of zinc oxide, 1-2 parts of stearic acid, 1-2 parts of sulfur, 1.5-2.5 parts of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.5-1.5 parts of tetramethylthiuram disulfide. The sponge rubber compound is made from the following raw materials in parts by weight: 80-120 parts of unmodified EPDM rubber, 20-40 parts of fast-extrusion furnace black, 10-20 parts of high-abrasion furnace black, 2-5 parts of polyethylene glycol, 40-60 parts of hydrogenated petroleum heavy alkane fraction, 4-6 parts of zinc oxide, 1-2 parts of stearic acid, 2-4 parts of 4,4'-oxobisbenzenesulfonyl hydrazine, 1-2 parts of azodicarbonamide, 1-1.5 parts of sulfur, 1-2 parts of N-tert-butyl-2-benzothiazole sulfenamide, and 1-1.5 parts of bispentamethylene thiuram tetrasulfide. In the dense rubber compound, the maleic anhydride-grafted EPDM rubber and the vinyltriethoxysilane undergo a synergistic in-situ reaction, causing the aluminum hydroxide to form covalent bonds with the rubber matrix to achieve physical reinforcement and flame retardancy. In the sponge rubber compound, the dielectric loss factor of the sponge rubber is adjusted by combining the high abrasion-resistant furnace black with the polyethylene glycol to match the heating rate of the solid rubber compound under a microwave field, thereby achieving synchronous cross-interfacial co-vulcanization crosslinking at the interface between the solid rubber and the sponge rubber.

[0008] By adopting the above technical solution, the present invention introduces an in-situ interface coupling enhancement mechanism and a microwave dielectric matching co-curing mechanism into the formulation system to solve the problems of mechanical attenuation and delamination in multilayer co-extrusion vulcanization under high filling conditions.

[0009] Conventional high-filling-content flame retardants are prone to causing stress concentration defects in rubber systems. To address this, the present invention constructs a covalent bond network between inorganic flame retardant particles and the rubber matrix within a dense rubber layer. During the mixing process, the ethoxy group of vinyltriethoxysilane undergoes a hydrolysis reaction to generate a silanol group. This group then undergoes dehydration condensation with the free hydroxyl groups on the surface of inorganic aluminum hydroxide to form an aluminum-oxygen-silicon chemical bond.

[0010] When heated, the anhydride groups on the maleic anhydride-grafted EPDM rubber molecular chain undergo ring-opening and esterification with the free hydroxyl groups remaining on the aluminum hydroxide surface. During the microwave vulcanization stage, the vinyl groups at the ends of the silane molecules grafted onto the aluminum hydroxide surface undergo covalent cross-linking with the unsaturated double bonds of the unmodified EPDM rubber molecular chain under the action of the vulcanization system.

[0011] The above reaction process essentially transforms aluminum hydroxide particles into cross-linking nodes in the three-dimensional network of rubber. Under stress, the stress can be transferred from the rubber matrix to the inorganic particles along the chemical bonds, preventing interface debonding. Combined with the expandable carbonized layer generated by heating ammonium polyphosphate and melamine cyanurate, it achieves physical barrier against oxygen and heat, allowing the rubber compound to retain its basic tensile strength while possessing flame retardant properties.

[0012] To address the issue of simultaneous vulcanization of composite cross-sections under alternating microwave electric fields, this invention introduces polyethylene glycol and high-abrasion-resistant furnace black into the sponge adhesive layer formulation. The polyethylene glycol coating on the surface of the high-abrasion-resistant furnace black improves the powder dispersion state, while the polar ether bonds within its structure induce dipole polarization loss in the microwave field, converting microwave energy into thermal energy.

[0013] This combination of polar ether bonds and conductive carbon black mesh improves the overall dielectric loss factor of the sponge adhesive, making the heat generation rate inside the sponge more consistent with the dense adhesive layer filled with a large amount of polar inorganic flame retardant. When the two adhesives converge at the head and enter the microwave field, due to the matching heating environment, the rubber macromolecular chains on both sides of the interface can be activated and cross-linked synchronously, forming a penetrating covalent bond network at the interface, thus avoiding the interlayer delamination phenomenon caused by the difference in vulcanization rate.

[0014] Preferably, the ammonium polyphosphate has a degree of polymerization greater than 1000, a crystal form of type II, a phosphorus mass fraction greater than 31%, and a nitrogen mass fraction greater than 14%; the kinematic viscosity at 40°C for both the first and second hydrogenated heavy petroleum alkane fractions is 90 mmHg. 2 / s to 120mm 2 / s, flash point greater than 200℃.

[0015] By adopting the above technical solution, the selection of ammonium polyphosphate with a degree of polymerization greater than 1000 and exhibiting type II crystallization is mainly due to its low water solubility, which prevents the sealing strip from precipitating flame retardants and whitening on the surface during long-term water immersion or high humidity environments in vehicles.

[0016] The formula uses hydrogenated petroleum heavy alkane fractions with high flash point and high viscosity as processing oil. On the one hand, it physically plasticizes EPDM rubber through the long-chain alkane structure and reduces mixing energy consumption. On the other hand, it avoids the risk of volatilization and foaming of the rubber compound under microwave hot air vulcanization conditions above 200°C, and maintains the smoothness and density of the dense rubber layer.

[0017] Preferably, in the first unmodified EPDM rubber and the second unmodified EPDM rubber, the mass fraction of ethylene units is 65% to 75%, the mass fraction of 5-ethylidene-2-norbornene units is 4% to 8%, and the Mooney viscosity ML1+4 is 60 to 80 under 125°C testing conditions; the number average molecular weight of the polyethylene glycol is 3800 to 4200, and the hydroxyl value ranges from 26 to 32 mgKOH / g.

[0018] By adopting the above technical solution, the mass fraction of ethylene units is controlled within the above range, so that the uncured rubber compound has the raw rubber strength required to maintain the extrusion molding size. The mass fraction of 5-ethylene-2-norbornene units is set in the range of 4% to 8%, which provides a crosslinking reaction rate suitable for rapid microwave continuous vulcanization process.

[0019] Limiting the number average molecular weight of polyethylene glycol to between 3800 and 4200 is to balance preventing migration and external spraying during processing, while avoiding problems such as mixing difficulties and reduced polarization loss efficiency caused by excessively large molecular weight.

[0020] Preferably, the maleic anhydride-grafted EPDM rubber is obtained by melt grafting of the following components in a twin-screw extruder: 80-120 parts of EPDM rubber, 1.5-2.5 parts of maleic anhydride, and 0.05-0.15 parts of dicumyl peroxide.

[0021] By adopting the above technical solution, the high shear field of a twin-screw extruder combined with a trace amount of initiator is used to achieve melt grafting of maleic anhydride onto the rubber backbone.

[0022] By controlling the amount of initiator to 0.05-0.15 parts, the self-crosslinking side reaction of rubber macromolecules at high temperature is limited while ensuring the grafting rate of polar groups, and the amount of gel formation is controlled, thereby ensuring the compatibility of the modified polymer when it is added to the compact rubber compound.

[0023] Secondly, the present invention provides a manufacturing process for a high-performance rubber-plastic composite sealing strip for new energy vehicles, comprising the following steps: S1. Add the raw materials of the dense rubber to the internal mixer to mix and discharge the rubber, then transfer it to the open mill to add the vulcanization system, mix evenly in triangular bags, and then sheet and let it stand to obtain the dense rubber compound. S2. Add the relevant raw materials of sponge rubber to the internal mixer for mixing and discharge, then transfer to the open mill, add foaming agent and vulcanization system, mix evenly in triangular bags, and then sheet out and let stand to obtain sponge rubber compound. S3. The dense rubber compound and the sponge rubber compound are fed into the composite extruder for co-extrusion to form a composite sealing strip semi-finished product; then they are sequentially fed into the microwave vulcanization section and the hot air drying tunnel to complete the vulcanization and foaming process, and a continuous composite sealing strip is obtained. S4. Apply silicone oil to the surface of the composite sealing strip continuous body and bake it in an infrared drying tunnel to achieve leveling. After cooling, cut it to obtain a high-performance rubber and plastic composite sealing strip for new energy vehicles.

[0024] By adopting the above technical solution, the process of mastering inorganic fillers and adding vulcanizing agents and foaming agents is carried out in different stages in different equipment. The high temperature and high shear conditions in the internal mixer stage provide an environment for the surface modification reaction of flame retardants and silane coupling agents. The subsequent operation in the open mill at a lower temperature ensures the safety of heat-sensitive additives when they are mixed in. Relying on continuous co-extrusion and microwave hot air series heating, the cross-sectional profile of the composite product is formed and vulcanized for mass production.

[0025] Preferably, the step of preparing the dense rubber compound in S1 includes: adding the first unmodified EPDM rubber, maleic anhydride-grafted EPDM rubber, the first fast-extrusion furnace black, aluminum hydroxide, ammonium polyphosphate, melamine cyanurate, vinyltriethoxysilane, the first hydrogenated petroleum heavy alkane fraction, the first zinc oxide and the first stearic acid into a mixer, mixing at a speed of 40-50 r / min, and discharging the rubber at a set discharge temperature of 130-140℃; After desizing, the rubber compound is transferred to a two-roll mill with the roll temperature set at 50-60℃. First sulfur, N-cyclohexyl-2-benzothiazole sulfenamide and tetramethylthiuram disulfide are added and mixed evenly in a triangular bag. After sheeting, it is kept at a constant temperature of 25℃ for 16-24 hours to obtain the dense rubber compound.

[0026] By adopting the above technical solution, the discharge temperature setting of 130-140℃ in the internal mixer meets the thermodynamic conditions required for the hydrolysis and condensation of silane coupling agent and the esterification and grafting of maleic anhydride, allowing for more thorough surface modification of fillers. Limiting the open mill roll temperature to the range of 50-60℃ prevents early scorching of the sulfur system. The sheeting and resting process after mixing allows sufficient time for the macromolecular chain segments inside the rubber compound to relax, releasing the internal stress accumulated during processing, which helps to improve the smoothness of the final co-extruded surface.

[0027] Preferably, the step of preparing the sponge rubber compound in S2 includes: adding the second unmodified EPDM rubber, the second fast-extrusion furnace black, the high abrasion-resistant furnace black, polyethylene glycol, the second hydrogenated petroleum heavy alkane fraction, the second zinc oxide, and the second stearic acid into a mixer, mixing at a speed of 40-50 r / min, and discharging the rubber at a set discharge temperature of 130-140℃; After desizing, the rubber compound is transferred to a two-roll mill with the roll temperature set at 50-60℃. 4,4'-oxobis(benzenesulfonyl)hydrazine, azodicarbonamide, second sulfur, N-tert-butyl-2-benzothiazole sulfenamide, and bis(pentamethylene)thiuram tetrasulfide are added and mixed evenly in a triangular bundle. After sheeting, the mixture is kept at a constant temperature of 25℃ for 16-24 hours to obtain the sponge rubber compound.

[0028] By adopting the above technical solution, the two-stage mixing process also maintains the structural stability of the foaming agent under low roller temperature operation. The step foaming system composed of azodicarbonamide and 4,4'-oxobisbenzenesulfonylhydrazine remains chemically inert during the low temperature period of mixing.

[0029] After a long period of constant temperature and static storage, the bonding network formed by carbon black and other powder materials in the rubber matrix reaches a stable state, enabling the semi-finished sponge to obtain structural support to resist deformation and collapse before foaming.

[0030] Preferably, the co-extrusion step in S3 includes: feeding the stored dense rubber compound and sponge rubber compound into the two extrusion heads of the composite extruder for plasticization; allowing the two rubber materials to enter the composite die head together and bond under the conditions of extruder barrel temperature of 60-70℃, die head temperature of 80-90℃, and controlled extrusion line speed of 10-15m / min; and forming the composite sealing strip semi-finished product with a predetermined cross-sectional shape through co-extrusion through the die.

[0031] By adopting the above technical solution and setting the stepped temperature parameters from the barrel to the die head, the two rubber compounds have matching flow and extrusion pressure in the extruder. When the rubber compounds merge in the flow channel of the composite die head, the macromolecular chain segments diffuse and entangle with each other across the physical interface under the combined action of fluid pressure and heat. The establishment of this physical interpenetrating interface prepares for the covalent crosslinking in the subsequent vulcanization process.

[0032] Preferably, the microwave foaming vulcanization step in S3 includes: immersing the co-extruded composite sealing strip semi-finished product in a microwave vulcanization section with a microwave frequency of 2450MHz and a microwave power of 4-8kW for radiation activation. Then it enters a hot air drying tunnel with a temperature of 200-230℃ to complete the vulcanization and foaming process; By controlling the heating conditions, the torque start-up time of the sponge rubber is made earlier than the foaming start-up time, and the peak foaming pressure is before the positive vulcanization time, so as to establish a cross-linking network and form a closed-cell structure.

[0033] By adopting the above technical solution, a control mechanism is established in the process that matches the foaming kinetics and crosslinking kinetics in time. In the initial stage of heating caused by microwave radiation and hot air, the decomposition of vulcanization accelerator triggers early crosslinking. At this time, the torque start-up time occurs earlier than the foaming start time, and the rubber macromolecules first construct a partial crosslinking network, and the viscosity of the rubber melt increases accordingly.

[0034] As the temperature inside the drying tunnel continues to rise, the stepped foaming system reaches its decomposition temperature and begins to release nitrogen. At this point, the matrix network with a certain physical strength constrains the gas expansion, limiting the long-range diffusion of gas molecules and preventing the bubbles from coalescing. When the cell expansion generates the maximum foaming pressure, the cross-linking reaction of the adhesive reaches the positive vulcanization point. The matrix network completes its curing and fixes the cell structure within the sponge matrix. This prevents the phenomenon of gas breaking through the pore walls and forming interconnected pores due to the weakness of the matrix, thus ensuring the regular closed-cell morphology after foaming.

[0035] Preferably, the surface spraying and heat setting steps in S4 include: uniformly spraying silicone oil with a main chain composed of siloxane bonds and a dynamic viscosity of 100-300 mPa·s at 25°C onto the surface of the composite sealing strip continuous after treatment in S3; baking it in an infrared drying tunnel at 120-150°C for 20-40 seconds to form a surface friction-reducing layer; and then cutting it after being pulled and cooled to 25°C by air cooling to obtain the high-performance rubber-plastic composite sealing strip for new energy vehicles.

[0036] By adopting the above technical solution, siloxane polymers with specific viscosity ranges can spread and partially penetrate and adhere to the rubber surface under the radiant heat field of the infrared drying tunnel, thereby reducing the friction coefficient of the outer surface of the dense rubber, reducing abnormal noise caused by the opening and closing of the car door, and reducing the probability of the rubber sealing strip sticking to or freezing on the metal paint surface of the car body under extreme hot and cold climate conditions.

[0037] This invention provides a high-performance rubber-plastic composite sealing strip for new energy vehicles and its manufacturing process. It has the following beneficial effects: 1. This invention introduces maleic anhydride-grafted EPDM rubber and vinyltriethoxysilane into a dense rubber compound, allowing a large amount of inorganic flame retardant aluminum hydroxide to form a strong covalent bond with the rubber matrix through multiple chemical reactions. This in-situ interfacial coupling reinforcement mechanism transforms inorganic particles that would otherwise cause stress concentration into stress-bearing nodes in a cross-linked network. While maintaining the synergistic flame retardant properties of ammonium polyphosphate and melamine cyanurate, it also maintains the physical tensile strength of the composite sealing strip matrix, solving the technical problem that conventional high-filler flame retardant modification leads to mechanical degradation of the rubber compound.

[0038] 2. This invention improves the overall dielectric loss factor of the sponge adhesive by adding high abrasion-resistant furnace black and polyethylene glycol to the sponge adhesive formulation, thereby adjusting the distribution and polarity of the conductive grid within the sponge system. This scheme makes the heat generation and heating rate of the sponge adhesive in the alternating microwave electric field more consistent with the dense adhesive layer filled with a large amount of polar flame retardant. This ensures that the two adhesives in different formulation systems can undergo activation and cross-linking reactions simultaneously at the composite interface, establishing a cross-interface covalent penetration network and eliminating the interlayer delamination defect caused by asynchronous vulcanization from the root.

[0039] 3. This invention establishes and controls a time-matching mechanism between foaming kinetics and crosslinking kinetics in the preparation of the sponge adhesive layer. By utilizing a step-type foaming system composed of azodicarbonamide and 4,4'-oxobisbenzenesulfonylhydrazine, and in conjunction with specific heating conditions, the rubber matrix establishes an initial crosslinking network before the foaming agent generates a large amount of gas to constrain the long-range diffusion of gas molecules. The matrix is ​​vulcanized and cured precisely when the foaming pressure reaches its peak. This kinetic matching method avoids the problem of insufficient matrix strength leading to gas breaking through the pore walls and forming interconnected pores. This results in a uniform and regular closed-cell structure in the sponge layer, ensuring that the sealing strip has a low compression set. Attached Figure Description

[0040] Figure 1 This is a schematic diagram showing the change of dielectric loss factor of different adhesives with test frequency. Figure 2 A schematic diagram of the internal temperature change of different rubber compounds under a microwave field over time. Figure 3 This is a schematic diagram of the vulcanization and foaming kinetics curves of sponge rubber, where a is a schematic diagram of the vulcanization torque changing with time, and b is a schematic diagram of the foaming pressure changing with time. Figure 4 This is a schematic diagram of the storage modulus of the dense rubber compound of the present invention as a function of strain. Figure 5 This is a schematic diagram showing the distribution of tensile and tear strength of the dense adhesive sample of the present invention; Figure 6 This is a schematic diagram of the horizontal burning velocity distribution of the dense adhesive sample of the present invention; Figure 7 This is a schematic diagram of the peeling force versus fixture displacement at a constant stretching rate according to the present invention. Figure 8 This is a schematic diagram of the change curve of average tensile force during the stable peeling stage of the present invention.

[0041] Figure 9 This is a schematic diagram of the high-temperature compression permanent deformation and vacuum water absorption rate test of the sponge rubber sample of the present invention. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Please see the appendix Figure 1 -Appendix Figure 9 : The main raw materials and reagents used in the following examples and comparative examples are as follows. Unless otherwise specified, all reagents are commercially available analytical grade or higher purity products.

[0044] Ammonium polyphosphate: degree of polymerization of 1000 to 3000, crystal form II, phosphorus mass fraction of 31% to 33%, nitrogen mass fraction of 14% to 16%, CAS number 68333-79-9.

[0045] Polyethylene glycol: number average molecular weight of 3800 to 4200, hydroxyl value of 26 to 32 mgKOH / g, CAS number 25322-68-3.

[0046] Hydrogenated petroleum heavy alkane fraction: kinematic viscosity at 40℃ is 90 mmHg 2 / s to 120mm 2 / s, flash point is 200℃ to 260℃, CAS number is 64742-54-7.

[0047] Silicone oil: A linear homopolymer with a main chain composed of siloxane bonds and methyl side groups. Its dynamic viscosity at 25°C is 100 mPa·s to 300 mPa·s. This type of medium-viscosity dimethyl silicone oil has excellent thermal stability. Its flash point is greater than 300°C, and it does not undergo significant volatilization or oxidative decomposition side reactions below 200°C. Its CAS number is 63148-62-9.

[0048] Unmodified ethylene propylene diene monomer (EPDM) rubber: a high molecular weight polymer formed by random copolymerization of ethylene, propylene, and the third monomer 5-ethylidene-2-norbornene in a mass ratio of 11.5:4:1. Its Mooney viscosity (ML(1+4)) at 125°C is 60 to 80, and its density is 0.86 g / cm³. 3 Up to 0.88 g / cm 3 The CAS number is 25038-36-2.

[0049] In this embodiment, the unit of measurement for the amount of each material and solvent is uniformly referred to as parts by weight.

[0050] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing maleic anhydride-grafted EPDM rubber, including the following steps: 120 parts by weight of EPDM rubber, 2.5 parts by weight of maleic anhydride, and 0.15 parts by weight of dicumyl peroxide were added to a high-speed mixer and mixed at 500 rpm for 5 minutes at room temperature to ensure uniform mixing. The mixture was then fed into a co-rotating twin-screw extruder with a length-to-diameter ratio of 40:1. The extruder feeding section temperature was set to 160°C, the melt grafting reaction section temperature to 185°C, the exhaust section was opened and the exhaust vacuum was set to -0.09 MPa, the metering section temperature was set to 180°C, the die head temperature was set to 175°C, the screw speed was set to 150 rpm, and the average residence time of the material in the barrel was set to 2 minutes. The material was extruded through a die, granulated by a water ring, and then the granules were dried in an oven at 80°C for 4 hours to obtain maleic anhydride-grafted EPDM rubber, hereinafter referred to as maleic anhydride-grafted EPDM rubber A.

[0051] Preparation Example 2: This preparation example provides a method for preparing maleic anhydride-grafted EPDM rubber, including the following steps: 100 parts by weight of EPDM rubber, 2.0 parts by weight of maleic anhydride, and 0.1 parts by weight of dicumyl peroxide were added to a high-speed mixer and mixed at 400 rpm for 4 minutes at room temperature to ensure uniform mixing. The mixture was then fed into a co-rotating twin-screw extruder with a length-to-diameter ratio of 40:1. The extruder feeding section temperature was set to 155°C, the melt grafting reaction section temperature to 178°C, the exhaust section was opened and the exhaust vacuum was set to -0.08 MPa, the metering section temperature was set to 178°C, the die head temperature was set to 173°C, the screw speed was set to 135 rpm, and the average residence time of the material in the barrel was set to 3 minutes. The material was extruded through a die, granulated by a water ring, and then the granules were dried in an oven at 75°C for 5 hours to obtain maleic anhydride-grafted EPDM rubber, hereinafter referred to as maleic anhydride-grafted EPDM rubber B.

[0052] Preparation Example 3: This preparation example provides a method for preparing maleic anhydride-grafted EPDM rubber, including the following steps: 80 parts by weight of EPDM rubber, 1.5 parts by weight of maleic anhydride, and 0.05 parts by weight of dicumyl peroxide were added to a high-speed mixer and mixed at 300 rpm for 3 minutes at room temperature to ensure uniform mixing. The mixture was then fed into a co-rotating twin-screw extruder with a length-to-diameter ratio of 40:1. The extruder feeding section temperature was set to 150°C, the melt grafting reaction section temperature to 170°C, the exhaust section was opened and the exhaust vacuum was set to -0.07 MPa, the metering section temperature was set to 175°C, the die head temperature was set to 170°C, the screw speed was set to 120 rpm, and the average residence time of the material in the barrel was set to 4 minutes. The material was extruded through a die, granulated by a water ring, and then the granules were dried in an oven at 70°C for 6 hours to obtain maleic anhydride-grafted EPDM rubber, hereinafter referred to as maleic anhydride-grafted EPDM rubber C.

[0053] Examples 1-5: Example 1: This embodiment provides a manufacturing process for a high-performance rubber-plastic composite sealing strip for new energy vehicles, including the following steps: S1. 120 parts of unmodified EPDM rubber, 15 parts of maleic anhydride-grafted EPDM rubber A, 60 parts of fast-extrusion furnace black, 60 parts of aluminum hydroxide, 20 parts of ammonium polyphosphate, 10 parts of melamine cyanurate, 3 parts of vinyltriethoxysilane, 50 parts of hydrogenated petroleum heavy alkane fraction, 6 parts of zinc oxide, and 2 parts of stearic acid are added to a mixing mill and mixed at a speed of 50 r / min. The discharge temperature is set to 140℃. Then, the rubber compound is transferred to a two-roll mill with a roll temperature set to 50℃. 2 parts of sulfur, 2.5 parts of N-cyclohexyl-2-benzothiazole sulfenamide, and 1.5 parts of tetramethylthiuram disulfide are added and repeatedly tumbled and rolled to mix evenly. After sheeting, the mixture is kept at 25℃ for 24 hours to obtain a dense rubber compound. S2. 120 parts of the second unmodified EPDM rubber, 40 parts of the second fast-extrusion furnace black, 20 parts of high abrasion-resistant furnace black, 5 parts of polyethylene glycol, 60 parts of the second hydrogenated petroleum heavy alkane fraction, 6 parts of the second zinc oxide, and 2 parts of the second stearic acid were added to a mixer and mixed at a speed of 50 r / min. The discharge temperature was set to 140℃. The rubber compound was then transferred to a two-roll mill with a roll temperature set to 50℃. 4 parts of 4,4'-oxobis(benzenesulfonyl)hydrazine, 2 parts of azodicarbonamide, 1.5 parts of the second sulfur, 2 parts of N-tert-butyl-2-benzothiazolium sulfenamide, and 1.5 parts of bis(pentamethylene)thiuram tetrasulfide were added and repeatedly tumbled and rolled to mix evenly. After sheeting, the mixture was kept at a constant temperature of 25℃ for 24 hours to obtain the sponge rubber compound. S3. The dense rubber compound and the sponge rubber compound are fed into the two extrusion heads of the composite extruder for plasticization. Under the conditions of an extruder barrel temperature of 70°C, a die temperature of 90°C, and an extrusion line speed of 15m / min, the two rubber materials are fed into the composite die head and bonded together. They are then co-extruded through the die to form a composite sealing strip semi-finished product with a predetermined cross-sectional shape. Subsequently, the composite sealing strip semi-finished product is fed into a microwave vulcanization section with a microwave frequency of 2450MHz and a microwave power of 8kW, and then into a hot air drying tunnel with a drying tunnel temperature of 230°C to complete the vulcanization and foaming process, thereby obtaining a continuous composite sealing strip. S4. Apply silicone oil evenly to the surface of the composite sealing strip continuous body after S3 treatment, put it into the infrared drying tunnel and bake it at 150°C for 20 seconds to form a surface friction-reducing layer. After being pulled and cooled to 25°C by air cooling, it is cut off to obtain the high-performance rubber and plastic composite sealing strip for new energy vehicles.

[0054] Example 2: This embodiment provides a manufacturing process for a high-performance rubber-plastic composite sealing strip for new energy vehicles, including the following steps: S1. 100 parts of unmodified EPDM rubber, 10 parts of maleic anhydride-grafted EPDM rubber B, 50 parts of fast-extrusion furnace black, 50 parts of aluminum hydroxide, 15 parts of ammonium polyphosphate, 7.5 parts of melamine cyanurate, 2 parts of vinyltriethoxysilane, 40 parts of hydrogenated petroleum heavy alkane fraction, 5 parts of zinc oxide, and 1.5 parts of stearic acid are added to a mixing mill and mixed at a speed of 45 r / min. The discharge temperature is set to 135℃. Then, the rubber compound is transferred to a two-roll mill with a roll temperature set to 55℃. 1.5 parts of sulfur, 2 parts of N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of tetramethylthiuram disulfide are added and repeatedly tumbled and rolled to mix evenly. After sheeting, the compound is kept at 25℃ for 20 hours to obtain a dense rubber compound. S2. 100 parts of the second unmodified EPDM rubber, 30 parts of the second fast-extrusion furnace black, 15 parts of high abrasion-resistant furnace black, 3.5 parts of polyethylene glycol, 50 parts of the second hydrogenated petroleum heavy alkane fraction, 5 parts of the second zinc oxide, and 1.5 parts of the second stearic acid were added to a mixer and mixed at a speed of 45 r / min. The discharge temperature was set to 135℃. The rubber compound was then transferred to a two-roll mill with a roll temperature set to 55℃. 3 parts of 4,4'-oxobis(benzenesulfonyl)hydrazine, 1.5 parts of azodicarbonamide, 1.25 parts of the second sulfur, 1.5 parts of N-tert-butyl-2-benzothiazolium sulfenamide, and 1.25 parts of bis(pentamethylene)thiuram tetrasulfide were added and repeatedly tumbled and rolled to mix evenly. After sheeting, the mixture was kept at a constant temperature of 25℃ for 20 hours to obtain the sponge rubber compound. S3. The dense rubber compound and the sponge rubber compound are fed into the two extrusion heads of the composite extruder for plasticization. Under the conditions of an extruder barrel temperature of 65°C, a die temperature of 85°C, and an extrusion line speed of 12.5 m / min, the two rubber materials are fed into the composite die head and bonded together. They are then co-extruded through the die to form a composite sealing strip semi-finished product with a predetermined cross-sectional shape. Subsequently, the composite sealing strip semi-finished product is fed into a microwave vulcanization section with a microwave frequency of 2450 MHz and a microwave power of 6 kW, and then into a hot air drying tunnel with a drying tunnel temperature of 215°C to complete the vulcanization and foaming process, resulting in a continuous composite sealing strip. S4. Apply silicone oil evenly to the surface of the composite sealing strip continuous body after S3 treatment, put it into the infrared drying tunnel and bake it at 135℃ for 30 seconds to form a surface friction-reducing layer. After being pulled and cooled to 25℃ by air cooling, it is cut off to obtain the high-performance rubber and plastic composite sealing strip for new energy vehicles.

[0055] Example 3: This embodiment provides a manufacturing process for a high-performance rubber-plastic composite sealing strip for new energy vehicles, including the following steps: S1. 80 parts of unmodified EPDM rubber, 5 parts of maleic anhydride-grafted EPDM rubber C, 40 parts of fast-extrusion furnace black, 40 parts of aluminum hydroxide, 10 parts of ammonium polyphosphate, 5 parts of melamine cyanurate, 1 part of vinyltriethoxysilane, 30 parts of hydrogenated petroleum heavy alkane fraction, 4 parts of zinc oxide, and 1 part of stearic acid are added to a mixing mill and mixed at a speed of 40 r / min. The discharge temperature is set to 130℃. Then, the rubber compound is transferred to a two-roll mill with a roll temperature set to 60℃. 1 part of sulfur, 1.5 parts of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.5 parts of tetramethylthiuram disulfide are added and repeatedly tumbled and rolled to mix evenly. After sheeting, the compound is kept at 25℃ for 16 hours to obtain a dense rubber compound. S2. Add 80 parts of the second unmodified EPDM rubber, 20 parts of the second fast-extrusion furnace black, 10 parts of high abrasion-resistant furnace black, 2 parts of polyethylene glycol, 40 parts of the second hydrogenated petroleum heavy alkane fraction, 4 parts of the second zinc oxide, and 1 part of the second stearic acid to a mixer and mix at a speed of 40 r / min. Set the discharge temperature to 130℃. Then transfer the rubber compound to a two-roll mill with the roll temperature set to 60℃. Add 2 parts of 4,4'-oxobis(benzenesulfonyl)hydrazine, 1 part of azodicarbonamide, 1 part of the second sulfur, 1 part of N-tert-butyl-2-benzothiazolium sulfenamide, and 1 part of bis(pentamethylene thiuram) tetrasulfide. Mix the compound evenly by repeated turning and rolling. After sheeting, keep it at 25℃ for 16 hours to obtain the sponge rubber compound. S3. The dense rubber compound and the sponge rubber compound are fed into the two extrusion heads of the composite extruder for plasticization. Under the conditions of an extruder barrel temperature of 60°C, a die temperature of 80°C, and a controlled extrusion speed of 10m / min, the two rubber materials are fed into the composite die head and bonded together. They are then co-extruded through the die to form a composite sealing strip semi-finished product with a predetermined cross-sectional shape. Subsequently, the composite sealing strip semi-finished product is fed into a microwave vulcanization section with a microwave frequency of 2450MHz and a microwave power of 4kW, and then into a hot air drying tunnel with a drying tunnel temperature of 200°C to complete the vulcanization and foaming process, thereby obtaining a continuous composite sealing strip. S4. Apply silicone oil evenly to the surface of the composite sealing strip after S3 treatment, put it into the infrared drying tunnel and bake it at 120°C for 40 seconds to form a surface friction-reducing layer. After being pulled and cooled to 25°C by air cooling, it is cut off to obtain a high-performance rubber and plastic composite sealing strip for new energy vehicles.

[0056] Example 4: This embodiment provides a manufacturing process for a high-performance rubber-plastic composite sealing strip for new energy vehicles, including the following steps: S1. 110 parts of unmodified EPDM rubber, 12 parts of maleic anhydride-grafted EPDM rubber A, 55 parts of fast-extrusion black, 55 parts of aluminum hydroxide, 18 parts of ammonium polyphosphate, 9 parts of melamine cyanurate, 2.5 parts of vinyltriethoxysilane, 45 parts of hydrogenated petroleum heavy alkane fraction, 5.5 parts of zinc oxide, and 1.8 parts of stearic acid are added to a mixing mill and mixed at a speed of 48 r / min. The discharge temperature is set to 138℃. Then, the rubber compound is transferred to a two-roll mill with a roll temperature set to 52℃. 1.8 parts of sulfur, 2.2 parts of N-cyclohexyl-2-benzothiazole sulfenamide, and 1.2 parts of tetramethylthiuram disulfide are added and repeatedly tumbled and rolled to mix evenly. After sheeting, the compound is kept at 25℃ for 22 hours to obtain a dense rubber compound. S2. 90 parts of unmodified EPDM rubber, 25 parts of fast-extrusion furnace black, 12 parts of high-abrasion furnace black, 3 parts of polyethylene glycol, 45 parts of hydrogenated petroleum heavy alkane fraction, 4.5 parts of zinc oxide, and 1.2 parts of stearic acid were added to a mixing mill and mixed at a speed of 48 r / min. The discharge temperature was set at 132℃. The rubber compound was then transferred to a two-roll mill with a roll temperature set at 52℃. 2.5 parts of 4,4'-oxobis(benzenesulfonyl)hydrazine, 1.2 parts of azodicarbonamide, 1.1 parts of second sulfur, 1.2 parts of N-tert-butyl-2-benzothiazolium sulfenamide, and 1.1 parts of bis(pentamethylene thiuram) tetrasulfide were added and repeatedly tumbled and rolled to mix evenly. After sheeting, the mixture was kept at 25℃ for 22 hours to obtain the sponge rubber compound. S3. The dense rubber compound and the sponge rubber compound are fed into the two extrusion heads of the composite extruder for plasticization. Under the conditions of extruder barrel temperature of 68℃, die head temperature of 88℃, and extrusion line speed of 14m / min, the two rubber materials are fed into the composite die head and bonded together. They are then co-extruded through the die to form a composite sealing strip semi-finished product with a predetermined cross-sectional shape. Subsequently, the composite sealing strip semi-finished product is fed into a microwave vulcanization section with a microwave frequency of 2450MHz and a microwave power of 7kW, and then into a hot air drying tunnel with a drying tunnel temperature of 225℃ to complete the vulcanization and foaming process, thereby obtaining a continuous composite sealing strip. S4. Apply silicone oil evenly to the surface of the composite sealing strip after S3 treatment, bake it in an infrared oven at 145°C for 25 seconds to form a surface friction-reducing layer, pull it and cool it to 25°C by air cooling before cutting it to obtain a high-performance rubber-plastic composite sealing strip for new energy vehicles.

[0057] Example 5: This embodiment provides a manufacturing process for a high-performance rubber-plastic composite sealing strip for new energy vehicles, including the following steps: S1. 90 parts of unmodified EPDM rubber, 8 parts of maleic anhydride-grafted EPDM rubber C, 45 parts of fast-extrusion black, 45 parts of aluminum hydroxide, 12 parts of ammonium polyphosphate, 6 parts of melamine cyanurate, 1.5 parts of vinyltriethoxysilane, 35 parts of hydrogenated petroleum heavy alkane fraction, 4.5 parts of zinc oxide, and 1.2 parts of stearic acid are added to a mixer and mixed at a speed of 42 r / min. The discharge temperature is set to 132℃. Then, the rubber compound is transferred to a two-roll mill with a roll temperature set to 58℃. 1.2 parts of sulfur, 1.8 parts of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.8 parts of tetramethylthiuram disulfide are added and repeatedly tumbled and rolled to mix evenly. After sheeting, the compound is kept at 25℃ for 18 hours to obtain a dense rubber compound. S2. 110 parts of the second unmodified EPDM rubber, 35 parts of the second fast-extrusion furnace black, 18 parts of high abrasion-resistant furnace black, 4.5 parts of polyethylene glycol, 55 parts of the second hydrogenated petroleum heavy alkane fraction, 5.5 parts of the second zinc oxide, and 1.8 parts of the second stearic acid were added to a mixer and mixed at a speed of 42 r / min. The discharge temperature was set to 138℃. The rubber compound was then transferred to a two-roll mill with the roll temperature set to 58℃. 3.5 parts of 4,4'-oxobis(benzenesulfonyl)hydrazine, 1.8 parts of azodicarbonamide, 1.4 parts of the second sulfur, 1.8 parts of N-tert-butyl-2-benzothiazolium sulfenamide, and 1.4 parts of bis(pentamethylene thiuram) tetrasulfide were added and repeatedly tumbled and rolled to mix evenly. After sheeting, the mixture was kept at 25℃ for 18 hours to obtain the sponge rubber compound. S3. The dense rubber compound and the sponge rubber compound are fed into the two extrusion heads of the composite extruder for plasticization. Under the conditions of an extruder barrel temperature of 62°C, a die temperature of 82°C, and an extrusion line speed of 11m / min, the two rubber materials are fed into the composite die head and bonded together. They are then co-extruded through the die to form a composite sealing strip semi-finished product with a predetermined cross-sectional shape. Subsequently, the composite sealing strip semi-finished product is fed into a microwave vulcanization section with a microwave frequency of 2450MHz and a microwave power of 5kW, and then into a hot air drying tunnel with a drying tunnel temperature of 205°C to complete the vulcanization and foaming process, thereby obtaining a continuous composite sealing strip. S4. Apply silicone oil evenly to the surface of the composite sealing strip after S3 treatment, put it into the infrared drying tunnel and bake it at 125°C for 35 seconds to form a surface friction-reducing layer. After being pulled and cooled to 25°C by air cooling, it is cut off to obtain a high-performance rubber and plastic composite sealing strip for new energy vehicles.

[0058] Comparative Examples 1-6: Comparative Example 1: The difference from Example 1 is that maleic anhydride-grafted EPDM rubber A and vinyltriethoxysilane were not added; otherwise, they are the same.

[0059] Comparative Example 2: Compared with Example 1, the difference is that the internal mixer discharge temperature is changed from 140°C to 105°C, and all other conditions are the same.

[0060] Comparative Example 3: Compared with Example 1, the difference is that ammonium polyphosphate and melamine cyanurate were not added, and the amount of aluminum hydroxide was increased from 60 parts to 90 parts, while the rest were the same.

[0061] Comparative Example 4: The difference from Example 1 is that polyethylene glycol was not added, and the high abrasion-resistant furnace black was replaced with an equal amount of the second fast extrusion furnace black; all other aspects are the same.

[0062] Comparative Example 5: The difference from Example 1 is that the delayed-acting accelerator N-tert-butyl-2-benzothiazole sulfenamide is replaced with an equal amount of diphenylguanidine, while the rest are the same.

[0063] Comparative Example 6: Compared to Example 1, the difference is that only 6 parts of azodicarbonamide were used as the foaming agent, and 4,4'-oxobisbenzenesulfonylhydrazine was not added; all other aspects were the same.

[0064] Comparative Example 7: The difference from Example 1 is that maleic anhydride-grafted EPDM rubber A was not added, but vinyltriethoxysilane was retained; otherwise, they are the same.

[0065] Comparative Example 8: The difference from Example 1 is that vinyltriethoxysilane was not added, but maleic anhydride-grafted EPDM rubber A was retained; otherwise, they are the same.

[0066] Test Example 1: Take the dense rubber compound prepared in Example 1, the sponge rubber compound prepared in Example 1, and the sponge rubber compound prepared in Comparative Example 4, place the rubber compound on a flat vulcanizing machine, and lightly press and shape it at 90°C to prepare round test samples with a thickness of 1.9-2.1 mm and a diameter of 9.8-10.2 mm, and leave them at room temperature for 24 hours to eliminate residual internal stress.

[0067] The dielectric properties of the samples were tested using a high-frequency impedance analyzer and a dielectric material testing fixture. Before testing, the fixture was calibrated for open and short circuits using a standard polytetrafluoroethylene block. The sample was placed between the electrodes and a constant clamping force was applied. The scanning frequency range was set to 2000MHz to 3000MHz, and the ambient temperature was maintained at 25℃. The dielectric loss factor values ​​of each sample near the 2450MHz test point were recorded.

[0068] Considering that the co-extruded semi-finished product is in an uncured state when it enters the microwave vulcanization section, in order to truly reflect the activation efficiency of the electromagnetic field on the rubber compound in industrial production, this test example uses uncured compound rubber as the test object.

[0069] In addition, to simulate the energy absorption behavior of actual extruded strip structures in a microwave field and avoid the electromagnetic field edge effect error generated by the disc sample, the above three strip-shaped unvulcanized rubber samples with the same cross-sectional size were prepared. The length of a single strip was set to 150 mm. The samples were placed parallel to each other on the conveyor belt insulated tray of the industrial microwave heating equipment. The microwave source frequency was set to 2450 MHz and the output power was 3.0 kW. The hot air circulation system was turned off.

[0070] Microwave radiation was turned on, and a multi-channel fiber optic temperature measurement system pre-arranged in the center and surface area of ​​the sample was used to monitor the temperature change inside the rubber in real time. The microwave source was turned on as the starting point for timing, and radiation was continued for 120 seconds. Real-time temperature data was recorded every 20 seconds. After the test, the arithmetic mean of the data of three parallel samples in the same group was taken.

[0071] The test results are shown in Tables 1 and 2.

[0072] Table 1: Dielectric loss factor test results of various rubber compound samples at 2450MHz frequency Table 2: Temperature rise (°C) records for each rubber compound sample during microwave irradiation. From Table 1 and Table 2 and Figure 1 and Figure 2 We can obtain: The dielectric loss factor of the sponge rubber compound in Example 1 is similar to that of the solid rubber in the 2450MHz microwave band. The introduction of polyethylene glycol and high abrasion-resistant furnace black in the formulation modulates the dielectric properties of the sponge rubber matrix and improves the microwave heating efficiency. Under the same microwave radiation environment, the heating curves of the two rubber compounds basically overlap, with a small temperature difference. The polymer macromolecular chain segments at the interface can be activated within the same temperature range. The matching thermodynamic conditions promote the cross-interfacial crosslinking of the two phase materials.

[0073] Comparative Example 4, by removing polyethylene glycol and high abrasion-resistant furnace black, showed a significant decrease in the dielectric loss factor of its sponge adhesive. The reduced microwave absorption efficiency caused the heating of the sponge adhesive in Comparative Example 4 to lag far behind that of the solid adhesive. When heated to 60 seconds, the temperature difference between the two exceeded 60°C. This thermal imbalance caused the solid layer on the high-temperature side to solidify prematurely, while the sponge layer on the low-temperature side had not yet reached the activation temperature. The data show that by controlling the dielectric constant to match the composite microwave vulcanization characteristics, a high-strength co-extrusion interface bond can be effectively established.

[0074] Test Example 2: The sponge rubber compound prepared in Example 1, Comparative Example 5 and Comparative Example 6 were used as test objects. A disc-shaped sample with a volume of 5 cubic centimeters was cut from the rubber sheet after it was placed at a constant temperature. The mass of a single sample was controlled within the range of 5.3-5.7g by an electronic balance with an accuracy of 0.01g.

[0075] A rotorless vulcanizing apparatus equipped with a foaming pressure sensor was used to conduct dual reaction kinetic tests. The apparatus was turned on and the test temperature of the upper and lower mold cavities was set to 180°C. The rotor swing angle was set to 0.5° and the swing frequency was controlled to 1.7Hz.

[0076] Place the weighed rubber sample in the center of the lower mold cavity of the vulcanizer, close the mold cavity and start the instrument's data acquisition system at the same time. During operation, the testing device synchronously records the torque value of the rubber and the pressure change value in the mold cavity caused by the decomposition of the foaming agent.

[0077] The continuous test time is set to 15 minutes. After the test, the system automatically outputs the torque-time curve and the foaming pressure-time curve, extracts the key node data in the reaction process, and records the torque start time (T10, minutes), positive vulcanization time (T90, minutes), foaming start time (P10, minutes) and foaming pressure peak time (Pmax, minutes).

[0078] The test results are shown in Table 3.

[0079] Table 3: Key node test data of vulcanization and foaming kinetics of sponge rubber compound at 180℃ From Table 3 and Figure 3 We can obtain: In Example 1, the torque start time T10 is earlier than the foaming start time P10, and the peak foaming pressure Pmax is before the positive vulcanization time T90. This indicates that the polymer matrix has established an initial cross-linking network before foaming, which restricts gas escape and pore merging, and completes network solidification at the peak foaming pressure to form a regular closed-cell structure.

[0080] In Comparative Example 5, after replacing the accelerator, T10 decreased to 0.65 min, indicating that crosslinking occurred before foaming. The sharp increase in matrix modulus suppressed the gas production expansion of the foaming agent, resulting in a decrease in the peak foaming pressure, which was macroscopically manifested as insufficient foaming rate. In Comparative Example 6, using a single foaming agent, P10 was extended to 3.45 min, and the peak foaming pressure Pmax was extended to 5.89 min. At this time, the degree of crosslinking of the matrix was close to T90. The high rigidity of the network structure allowed the gas released in the later stage to break through the pore walls and form interconnected pores, which in turn led to an increase in the material's compression permanent deformation rate. The data verified that the time matching between the stepped gas production system and the delayed vulcanization network is crucial for ensuring the foaming quality of the sponge rubber.

[0081] Test Example 3: The dense rubber compounds prepared in Examples 1, 1, 2, 7, and 8 were used as test objects. The rubber compounds were calendered into sheets with a thickness of about 1.5 mm after being left to stand using a two-roll mill. A portion of the rubber sheets was cut into particles with a side length of no more than 2 mm for solvent extraction testing of the binder content. Another portion of the intact rubber sheets was punched into disc samples with a diameter of 40 mm for dynamic rheological property testing of the uncured rubber compounds.

[0082] Weigh 1.0g of crushed rubber sample, wrap it in a 300-mesh stainless steel wire mesh of known mass, tie it tightly and record the total mass. Place the wrapped sample in a wide-mouth bottle containing 250mL of room temperature toluene solvent and let it stand in the dark for 72 hours. Replace the toluene solvent with fresh solvent every 24 hours to extract free rubber molecular chains that have not been bound to the filler. After soaking, remove the wire mesh package and place it in a vacuum drying oven at 60℃ to dry it to constant weight. Weigh and calculate the mass of the residue. After deducting the theoretical mass of the insoluble filler in the formulation, calculate the percentage of the bound rubber in the total rubber component of the system.

[0083] The dynamic rheological properties of the rubber compound were determined using a rubber processing analyzer to characterize the Payne effect within the system. The test chamber temperature was set to 100℃ and the test frequency to 1Hz. The mold cavity was closed and preheated for 2 minutes to ensure uniform temperature within the rubber compound. The strain scanning program was then started, and the dynamic strain was gradually increased from 1% to 100%. The system recorded the storage modulus values ​​at different strain nodes in real time.

[0084] The test results are shown in Tables 4 and 5.

[0085] Table 4: Binder Extraction Test Data of Dense Rubber Compound Table 5: Storage Modulus Recordings under Dynamic Strain Scanning by Rubber Processing Analyzer From Tables 4 and 5 and Figure 4 We can obtain: In Example 1, 43.7% of the bound rubber was retained after extraction, and the decrease in storage modulus with increasing strain was small, indicating a weakened Payne effect. This suggests that the maleic anhydride-grafted EPDM rubber reacts with the vinyl silane coupling agent at a discharge temperature of 140°C, causing the aluminum hydroxide filler to be chemically bonded to the EPDM rubber. The filler surface is encapsulated, reducing particle aggregation, lowering the rigidity of the filler network, and improving the binding force against solvent extraction.

[0086] Comparative Example 1 removed the coupling component, reducing the binder content to 14.2%, and its storage modulus decreased sharply with strain, exhibiting a strong Payne effect. The aluminum hydroxide particles agglomerated in the matrix, and the resulting structure was prone to slippage and disintegration under stress. Comparative Example 2 reduced the binder discharge temperature to 105℃, failing to effectively activate silanization and grafting reactions, resulting in insufficient covalent bonding between the filler and the rubber. Its rheological and extraction data were only slightly better than those of Comparative Example 1.

[0087] Comparative Example 7 only added silane, which could couple the powder surface, but lacked grafted macromolecular chains as a bridge, so the powder could not be effectively anchored to the rubber backbone. Comparative Example 8 only added grafted adhesive, but lacked silane mediation, so the grafted groups could not directly break the surface polarity barrier of the inorganic powder. The adhesive content of the two was only 20.3% and 22.4%, respectively, and the storage modulus was still high under low strain, with a significant Payne effect.

[0088] The above evidence shows that grafted adhesive and silane must coexist in order to construct a complete covalent bond bridging network between inorganic powder and rubber matrix. Tests have shown that the combination of in-situ coupling system and specific high-temperature conditions can effectively improve the dispersibility of fillers and enhance interfacial bonding strength.

[0089] Test Example 4: The solid rubber vulcanized sheets prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were used as test objects. The vulcanized sheets that had been left to stand for more than 16 hours were placed on a cutting machine, and standard type 1 dumbbell-shaped samples and right-angled tear-resistant samples without cuts were cut along the calendering direction. Samples with burrs on the edges or thickness tolerances exceeding ±0.05 mm were removed to ensure the dimensional consistency of each group of test samples.

[0090] Mechanical properties were evaluated using a microcomputer-controlled electronic universal testing machine equipped with a high-precision extensometer. The specimens were symmetrically clamped in the upper and lower fixtures, and the tensile rate was set to a constant 500 mm / min. The ambient temperature was controlled between 21-25℃. The system automatically recorded the maximum force value during the specimen's breakage process, calculated the tensile strength based on the cross-sectional area, and extracted the maximum load when the right-angle specimen was torn to calculate the tear strength. Five parallel specimens were tested for each formulation, and the arithmetic mean was taken.

[0091] According to the horizontal combustion test standard, a solid rubber strip sample with dimensions of 356mm×100mm×2mm was cut. The sample was horizontally installed on the U-shaped bracket of the combustion test chamber. In the fume hood, a Bunsen burner flame of calibrated height was applied to the free end of the sample for 15 seconds and then the flame was removed. The time it took for the flame tip to spread to the first and second markings was recorded. The combustion rate was calculated and the melting dripping phenomenon was observed.

[0092] The test results are shown in Tables 6 and 7.

[0093] Table 6: Room Temperature Tensile and Tear Strength Test Data of Dense Rubber Samples Table 7: Horizontal Combustion Test Data of Dense Adhesive Samples From Tables 6 and 7 and Figure 5 and 6 We can obtain: In Examples 1 to 5, while the burning rate was controlled below 15.1 mm / min, the tensile strength reached above 10.1 MPa and the tear strength remained above 32.6 kN / m. The interfacial chemical bonds constructed by maleic anhydride-grafted EPDM rubber and silane coupling agent enabled the inorganic flame retardant powder to be effectively dispersed and combined in the continuous polymer phase. The filler interface was transformed into nodes that could withstand external loads, thus achieving physical reinforcement.

[0094] Comparative Examples 1 and 2 altered the coupling state, resulting in a significant decrease in mechanical properties. The tensile strength of Comparative Example 1 dropped to 6.78 MPa. Due to the lack of effective coating, aluminum hydroxide particles agglomerated, making them prone to microcracks under stress. In Comparative Example 3, the composite flame retardant was removed while the amount of aluminum hydroxide was increased to 90 parts. The combustion rate actually increased to 65.4 mm / min, and the tensile and tear strengths were reduced to the lowest levels. After combustion, the single hydroxide lacked a dense carbon layer for heat insulation and oxygen barrier. Excessive inorganic powder also disrupted the continuity of the matrix. The results indicate that the synergistic flame retardant design can maintain good overall mechanical and flame retardant properties of the material while reducing the total amount of flame retardant.

[0095] Test Example 5: The finished composite sealing strips prepared in Examples 1 to 5 and Comparative Example 4 were used as test objects. The sealing strip samples with a length of 148-152 mm were randomly cut from the continuous microwave vulcanization extrusion production line and left at room temperature for 24 hours to ensure the relaxation of residual stress inside the colloid. A pre-peeling cut with a length of 30 mm was cut at one end of the sample along the co-extrusion interface of the solid colloid and the sponge colloid. During the cutting process, it is necessary to avoid damaging the matrix material on both sides. This separated section is used as the clamping end of the tension jig.

[0096] The interface dynamic peel test is performed using a microcomputer-controlled electronic universal testing machine equipped with a pneumatic flat-push clamp. The pre-separated solid adhesive end and sponge adhesive end are fixed in the upper and lower clamps of the testing machine, respectively. The initial spacing of the clamps is adjusted so that the unpeeled part of the sample is in a natural vertical state without pre-tension. The ambient temperature during the test is controlled within the range of 21-25℃.

[0097] Start the testing machine control program and set the relative separation speed of the upper and lower clamps to a constant 50 mm / min. During the tensile process, the testing machine system records the peel force value captured by the load sensor and the clamp displacement data in real time. The peeling action continues until the sample is completely separated along the co-extrusion interface or the colloid body on one side breaks.

[0098] After the test, the average tensile force data after the peeling entered the stable stage was extracted from the load-displacement curve exported by the system. The cross section of the separated specimen was observed by the naked eye, and the failure mode of the interface was recorded. Five parallel specimens were selected from each formulation to repeat the above tensile process, and the arithmetic mean of the tensile force was calculated.

[0099] The test results are shown in Table 8.

[0100] Table 8: Test data on co-extrusion interfacial bonding strength and failure mode of composite sealing strips From Table 8 and Figure 7 and Figure 8 We can obtain: The average tensile strength of the composite samples in Examples 1 to 5 remained between 183.6 N and 195.8 N. The fracture of the samples under stress all occurred inside the rubber matrix, exhibiting bulk tearing failure. This indicates that the chemical bonding force at the co-extrusion interface exceeded the cohesive force of the polymer. The addition of polyethylene glycol and high abrasion-resistant furnace black improved the dielectric constant matching between the sponge rubber and the dense rubber, allowing the two phases of rubber to simultaneously heat up to the vulcanization activation temperature during microwave heating. The consistency of the thermodynamic state provided sufficient time for the diffusion of molecular chain segments on both sides of the interface and the formation of covalent bonds, thus achieving co-vulcanization of the interface.

[0101] Comparative Example 4, with the removal of dielectric modulator components, showed an average tensile strength reduced to 112.3 N. The failure mode was smooth interface peeling with complete separation of the two phases. Due to the different microwave absorption rates, the dense rubber compound reached the activation temperature and cured earlier, blocking the diffusion path of molecular chains across the interface. The sponge rubber compound with delayed heating could not undergo co-vulcanization reaction with the cured dense rubber compound. The test results showed that the synchronicity of dielectric response played a decisive role in improving the co-extrusion interfacial bonding force of multilayer composite products.

[0102] Test Example 6: Cut the finished composite sealing strips of Examples 1 to 5, Comparative Examples 5 and 6, and use a slicing device to peel the sponge adhesive part from the solid adhesive skeleton, remove the area with skin and residual adhesive, grind the test surface flat, and prepare a cuboid sponge sample with a thickness of not less than 6 mm. The sample is placed in a standard laboratory environment for 24 hours to eliminate residual stress in the preparation process.

[0103] According to the standard for testing the compression set of sponge rubber, the initial thickness of the central region of the sample was measured using a thickness gauge. The sample was then placed in a compression limiter consisting of two parallel steel plates. The sample thickness was compressed to 50% of the initial value by a metal limit block. The clamp in the compressed state was then moved into a forced convection aging chamber preheated to 90°C and kept at a constant temperature for 70 hours. The clamp was then removed and the compression was released. The sample was transferred to an insulating board and allowed to recover freely at room temperature for 2 hours. The final thickness was measured and the compression set rate was calculated.

[0104] Sponge samples prepared under the same conditions were extracted and subjected to vacuum water absorption characterization to quantify the connectivity and sealing of the internal pores. The initial dry weight of the samples was weighed on an analytical balance. The samples were then immersed in a vacuum desiccator filled with distilled water and a stainless steel mesh was used to weigh the samples to prevent them from detaching from the liquid surface.

[0105] The vacuum system was activated to evacuate the air pressure inside the desiccator to below 10 kPa and maintain this pressure for 10 minutes. This removed the air from the surface of the sample and the inside of the openings. The vacuum was then released to restore the normal pressure environment, and the sample was allowed to stand and soak for 3 minutes. The sample was then removed, and the free moisture on the surface was wiped off with lint-free filter paper. The sample was then placed in a sealed weighing bottle to measure its wet weight. The percentage of the absorbed water mass relative to the initial dry weight was calculated. Three samples were tested in parallel for each group of experiments, and the arithmetic mean was taken.

[0106] The test results are shown in Tables 9 and 10.

[0107] Table 9: High-Temperature Compression Permanent Deformation Test Data of Sponge Samples at 90℃×70h Table 10: Internal pore structure characteristics and vacuum water absorption rate measurement results of sponge adhesive samples From Table 9, Table 10 and Figure 9 We can obtain: The compression set of Examples 1 to 5 is less than 23.3%, the vacuum water absorption rate is no more than 3.0%, and the sponge matrix maintains a uniform and dense closed-cell structure. When compressed, the regular closed-cell network can disperse stress, and the static pressure of the gas in the closed pores and the elasticity of the rubber molecular chains together promote the material to recover its deformation, thus exhibiting excellent compression resistance.

[0108] Comparative Example 5 showed a compression set rate of 41.9% and a water absorption rate of 3.6%. Its cross-linking network was established too early, and the high-modulus matrix inhibited gas expansion, resulting in a low foaming rate and thick bubble walls. Under high-temperature compression, the structure underwent irreversible plastic deformation, reducing its elastic recovery ability. Comparative Example 6 showed a water absorption rate as high as 75.8% and a compression set rate of 69.2%. This was because the gas generation process in the later stage tore apart the solidified cross-linked skeleton, forming a large number of interconnected pores. The bubble walls lost their load-bearing capacity and underwent mechanical collapse. The results verified that the timing of vulcanization and gas generation processes is the key to constructing a stable closed-cell structure and reducing high-temperature compression set.

[0109] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-performance rubber-plastic composite sealing strip for new energy vehicles, characterized in that, The sealing strip is composed of co-extruded and bonded dense rubber compound and sponge rubber compound; The dense rubber compound is made from the following raw materials in parts by weight: 80-120 parts of unmodified EPDM rubber, 5-15 parts of maleic anhydride-grafted EPDM rubber, 40-60 parts of fast-extrusion furnace black, 40-60 parts of aluminum hydroxide, 10-20 parts of ammonium polyphosphate, 5-10 parts of melamine cyanurate, 1-3 parts of vinyltriethoxysilane, 30-50 parts of hydrogenated petroleum heavy alkane fraction, 4-6 parts of zinc oxide, 1-2 parts of stearic acid, 1-2 parts of sulfur, 1.5-2.5 parts of N-cyclohexyl-2-benzothiazole sulfenamide, and 0.5-1.5 parts of tetramethylthiuram disulfide. The sponge rubber compound is made from the following raw materials in parts by weight: 80-120 parts of unmodified EPDM rubber, 20-40 parts of fast-extrusion furnace black, 10-20 parts of high-abrasion furnace black, 2-5 parts of polyethylene glycol, 40-60 parts of hydrogenated petroleum heavy alkane fraction, 4-6 parts of zinc oxide, 1-2 parts of stearic acid, 2-4 parts of 4,4'-oxobisbenzenesulfonyl hydrazine, 1-2 parts of azodicarbonamide, 1-1.5 parts of sulfur, 1-2 parts of N-tert-butyl-2-benzothiazole sulfenamide, and 1-1.5 parts of bispentamethylene thiuram tetrasulfide. The raw materials for solid rubber are mixed and discharged in an internal mixer, then transferred to a two-roll mill to add a vulcanization system and mix evenly in triangular bundles. The resulting solid rubber compound is then sheeted and left to stand. The raw materials for sponge rubber are mixed and discharged in an internal mixer, then transferred to a two-roll mill to add a foaming agent and a vulcanization system and mix evenly in triangular bundles. The resulting sponge rubber compound is sheeted and left to stand, and discharged at a set discharge temperature of 130-140℃.

2. The high-performance rubber-plastic composite sealing strip for new energy vehicles according to claim 1, characterized in that, The ammonium polyphosphate has a degree of polymerization of 1000 to 3000, a crystal form of type II, a phosphorus mass fraction of 31% to 33%, and a nitrogen mass fraction of 14% to 16%.

3. The high-performance rubber-plastic composite sealing strip for new energy vehicles according to claim 1, characterized in that, The kinematic viscosity at 40°C for both the first and second hydrogenated petroleum heavy alkane fractions is 90 mmHg. 2 / s to 120mm 2 / s, flash point is 200℃ to 260℃.

4. The high-performance rubber-plastic composite sealing strip for new energy vehicles according to claim 1, characterized in that, The polyethylene glycol has a number-average molecular weight of 3800 to 4200 and a hydroxyl value of 26 to 32 mgKOH / g.

5. A manufacturing process for high-performance rubber-plastic composite sealing strips for new energy vehicles, characterized in that, The method for preparing the high-performance rubber-plastic composite sealing strip for new energy vehicles according to any one of claims 1-4 includes the following steps: S1. Add the raw materials of the dense rubber to the internal mixer for mixing and discharge, then transfer to the open mill, add the vulcanization system, mix evenly in triangular bags, and then sheet and let stand to obtain the dense rubber compound. S2. Add the relevant raw materials of sponge rubber to the internal mixer for mixing and discharge, then transfer to the open mill, add foaming agent and vulcanization system, mix evenly in triangular bags, and then sheet out and let stand to obtain sponge rubber compound. S3. The dense rubber compound and the sponge rubber compound are fed into the composite extruder for co-extrusion to form a composite sealing strip semi-finished product; then they are sequentially fed into the microwave vulcanization section and the hot air drying tunnel to complete the vulcanization and foaming process, and a continuous composite sealing strip is obtained. S4. Apply silicone oil to the surface of the composite sealing strip continuous body and bake it in an infrared drying tunnel to achieve leveling. After cooling, cut it to obtain a high-performance rubber and plastic composite sealing strip for new energy vehicles.

6. The preparation process of the high-performance rubber-plastic composite sealing strip for new energy vehicles according to claim 5, characterized in that, In S1, the step of preparing the dense rubber compound includes: The first unmodified EPDM rubber, maleic anhydride-grafted EPDM rubber, first fast-extrusion furnace black, aluminum hydroxide, ammonium polyphosphate, melamine cyanurate, vinyltriethoxysilane, first hydrogenated petroleum heavy alkane fraction, first zinc oxide and first stearic acid are added to a mixer and mixed at a speed of 40-50 r / min, and discharged at a set discharge temperature of 130-140℃. The rubber compound after desizing is then transferred to a two-roll mill with the roller temperature set at 50-60℃. First sulfur, N-cyclohexyl-2-benzothiazole sulfenamide and tetramethylthiuram disulfide are added and mixed evenly in a triangular bag. After sheeting, the mixture is kept at a constant temperature of 25°C for 16-24 hours to obtain the dense rubber compound.

7. The preparation process of the high-performance rubber-plastic composite sealing strip for new energy vehicles according to claim 5, characterized in that, In S2, the step of preparing the sponge rubber compound includes: The second unmodified EPDM rubber, the second fast-extrusion furnace black, the high abrasion-resistant furnace black, polyethylene glycol, the second hydrogenated petroleum heavy alkane fraction, the second zinc oxide, and the second stearic acid are added to the internal mixer and mixed at a speed of 40-50 r / min. The rubber is then discharged at a set discharge temperature of 130-140℃. The rubber compound after desizing is then transferred to a two-roll mill with the roller temperature set at 50-60℃. 4,4'-oxobisbenzenesulfonylhydrazine, azodicarbonamide, second sulfur, N-tert-butyl-2-benzothiazole sulfenamide and bispentamethylene thiuram tetrasulfide are added and mixed evenly in a triangular bag. After sheeting, the mixture is kept at a constant temperature of 25°C for 16-24 hours to obtain the sponge rubber compound.

8. The preparation process of the high-performance rubber-plastic composite sealing strip for new energy vehicles according to claim 5, characterized in that, In S3, the co-extrusion step includes: After being left to stand, the dense rubber compound and the sponge rubber compound are fed into the two extrusion main units of the composite extruder for plasticization. Under the conditions of an extruder barrel temperature of 60-70℃, a die temperature of 80-90℃, and an extrusion line speed of 10-15m / min, the two rubber materials are allowed to enter the compounding head together and be bonded. The composite sealing strip semi-finished product with a predetermined cross-sectional shape is formed by co-extrusion through a die.

9. The preparation process of the high-performance rubber-plastic composite sealing strip for new energy vehicles according to claim 5, characterized in that, In S3, the microwave foaming vulcanization step includes: The co-extruded composite sealing strip semi-finished product is then placed in a microwave vulcanization section with a microwave frequency of 2450MHz and a microwave power of 4-8kW for radiation activation. Then it enters a hot air drying tunnel with a temperature of 200-230℃ to complete the vulcanization and foaming process; In this process, by controlling the heating conditions, the torque start time T10 of the sponge adhesive is made earlier than the foaming start time P10, and the peak foaming pressure Pmax is before the positive vulcanization time T90, so as to establish a cross-linking network and form a closed-cell structure.

10. The preparation process of the high-performance rubber-plastic composite sealing strip for new energy vehicles according to claim 5, characterized in that, In S4, the surface spraying and heat setting steps include: Silicone oil with a main chain composed of siloxane bonds and a dynamic viscosity of 100-300 mPa·s at 25°C was uniformly sprayed onto the surface of the composite sealing strip continuous after S3 treatment. The surface is placed in an infrared drying tunnel and baked at 120-150℃ for 20-40 seconds to form a surface anti-friction layer. After being pulled and cooled to 25°C by air cooling, it is cut off to obtain the high-performance rubber-plastic composite sealing strip for new energy vehicles.

Images