High and low temperature resistant EPDM rubber material, and preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a high and low temperature resistant EPDM (Ethylene-Propylene-Diene Monomer) rubber material as well as a preparation method and application thereof, and the high and low temperature resistant EPDM rubber material comprises the following components in parts by mass: 44.4-64.9 parts of ethylene propylene diene monomer; 6.7 to 26.0 parts of vinyl-terminated polydimethylsiloxane; 13.3 to 39.0 parts of gas phase method nano silicon dioxide; 0.9 to 3.9 parts of a flexible long-chain molecular bridge coupling agent; 0.4 to 3.2 parts of an ionic network construction auxiliary agent; 1.8 to 5.2 parts of a peroxide vulcanizing agent; 0.4 to 1.9 parts of an assistant cross-linking agent; and 0.4 to 1.9 parts of an antioxidant. By constructing a triple interpenetrating network and a flexible interface and adopting a step-by-step construction process, the low-temperature flexibility, high-temperature stability and mechanical strength of the material are synergistically improved, meanwhile, excellent processing safety is ensured, and the bottleneck that comprehensive performance is difficult to consider in the prior art is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a high and low temperature resistant EPDM compound and a preparation method and application thereof. BACKGROUND

[0002] Ethylene propylene diene rubber (EPDM) has excellent weather resistance, ozone resistance and chemical resistance due to its saturated main chain structure, and has been widely and successfully applied in the fields of automobile sealing, wire and cable, building waterproofing, etc. However, with the increasingly stringent requirements of modern industry on material performance, especially when dealing with complex conditions such as high and low temperature alternation and dynamic load, the inherent shortcomings of traditional EPDM materials are increasingly prominent.

[0003] The intrinsic characteristics of its molecular chain determine that its low temperature compliance is poor, and it is difficult to meet the stringent requirements of high-end equipment to remain flexible in extremely cold environments. In order to improve its mechanical properties to adapt to higher strength application scenarios, nano-silica and other inorganic fillers are usually added to the EPDM matrix for reinforcement. However, this enhancement method often relies on the "hard" connection formed by traditional rigid coupling agents between the filler and the rubber matrix, which, although to some extent, improves the strength and modulus of the material, often at the expense of its toughness and elongation at break, and may further deteriorate its low temperature performance, leading to a brittle material and reduced reliability during long-term service.

[0004] In addition, the existing preparation process also has significant limitations. Traditional blending methods often fail to accurately control the complex reactions of various chemical additives at different temperatures, easily leading to insufficient filler-matrix interface interaction and suboptimal network structure formation. Especially when introducing high-efficiency peroxide vulcanization systems, the high temperature during processing can easily cause early vulcanization of the compound, i.e., "scorching", which not only seriously affects the performance uniformity of the final product, but also poses a significant safety hazard and process control problem for stable industrial production.

[0005] Therefore, the present application proposes a high and low temperature resistant EPDM compound and a preparation method and application thereof to solve the problems of the prior art. SUMMARY

[0006] The purpose of the present application is to provide a high and low temperature resistant EPDM compound and a preparation method and application thereof, which solves the problem that ethylene propylene diene rubber materials are difficult to simultaneously broaden the service temperature range, improve mechanical strength and ensure processing safety.

[0007] To achieve the above purpose, the present application is implemented by the following technical scheme: a high and low temperature resistant EPDM compound, comprising the following components in mass fraction: EPDM: 44.4-64.9 parts; end-vinyl polydimethylsiloxane: 6.7-26.0 parts; fumed nano-silica: 13.3-39.0 parts; flexible long-chain molecular bridge coupling agent: 0.9-3.9 parts; ionic network building assistant: 0.4-3.2 parts; peroxide curing agent: 1.8-5.2 parts; co-crosslinking agent: 0.4-1.9 parts; antioxidant: 0.4-1.9 parts.

[0008] The high and low temperature resistant EPDM compound is composed of EPDM, end-vinyl polydimethylsiloxane, fumed nano-silica, flexible long-chain molecular bridge coupling agent, ionic network building assistant, peroxide curing agent, co-crosslinking agent and antioxidant, etc. By controlling the coupling of chemical properties of each component and preparation process, a multiple interpenetrating network system coexisting physical entanglement and chemical crosslinking is formed in the EPDM matrix. In this system, the stable covalent network formed by EPDM is the skeleton of the material, which ensures the basic mechanical strength and chemical stability; while the introduced flexible long-chain silicone network acts as a kind of "molecular spring", which significantly improves the low temperature flexibility of the material; at the same time, the dynamic and reversible ionic network acts as an energy dissipation and stress relaxation mechanism under high stress or high temperature, which improves the high temperature stability and toughness of the material. The EPDM preferably has a specific ethylene content and a brand with ethylidenenorbornene (ENB) as the third monomer. Higher ethylene content helps to improve the mechanical properties and filling capacity of the material, while ENB as the third monomer, its unsaturated double bond is located in the side group, and the main chain remains saturated, which endows EPDM with excellent heat resistance, weather resistance and ozone resistance, and provides active reaction points for subsequent peroxide vulcanization. The end-vinyl polydimethylsiloxane (VMQ) as the building unit of flexible network, its terminal vinyl group can co-crosslink with the EPDM network during the vulcanization stage, while its own flexible Si-O-Si main chain constitutes the basis for the material to have excellent low temperature performance. Fumed nano-silica as the key reinforcing filler, its high specific surface area and surface activity provide an ideal platform for subsequent surface grafting modification, and is an important node for building a reinforced network; The flexible long-chain molecular bridge coupling agent, such as a vinyl polyoxyethylene ether group trialkoxysilane, is the key to realizing the efficient combination of inorganic fillers and organic matrix. The alkoxysilane group at one end can hydrolyze and condense with the hydroxyl group on the surface of the silica, firmly "anchoring" itself on the surface of the filler; the vinyl group at the other end can participate in subsequent peroxide vulcanization and become part of the crosslinked network. More importantly, the flexible polyoxyethylene ether segment contained in its molecular chain builds a "flexible bridge" between the filler and the rubber matrix, effectively relieving the interface stress concentration, improving the dispersion of the filler, and playing a crucial role in improving the dynamic performance and low temperature performance of the material. Ionic network building aids, such as zinc stearate or zinc acrylate, form dynamic ionic clusters in the matrix. These ionic bonds act as physical crosslinking points at room temperature, improving material strength; at high temperatures or high stresses, they will dissociate and recombine, preventing crack propagation through sliding and energy dissipation, thereby imparting unique high-temperature stability and toughness to the material. The synergistic effect of peroxide vulcanizing agent and co-crosslinking agent (such as triallyl isocyanurate) ensures that a dense and stable EPDM covalent crosslinked network is formed during the vulcanization stage. The antioxidant system composed of hindered phenol and phosphite can provide all-round thermal-oxidative aging protection, ensuring the performance stability of the compound during long-term use.

[0009] Preferably, the ethylene content of the terpolymer is 55-70%, the third monomer of the terpolymer is ethylidene norbornene; the dynamic viscosity of the end-vinyl polydimethylsiloxane is 500-2000 mPa·s; the specific surface area of the fumed nano-silica is 180-220 m 2 / g.

[0010] Preferably, the flexible long-chain molecular bridge coupling agent is a vinyl polyoxyethylene ether group trialkoxysilane; the ionic network building aid is zinc stearate or zinc acrylate; the peroxide vulcanizing agent is di-2-tert-butyl peroxyisopropyl-benzene peroxide.

[0011] Preferably, the co-crosslinking agent is triallyl isocyanurate; the antioxidant is a composite of hindered phenolic antioxidant and phosphite antioxidant.

[0012] The application also provides a preparation method of the high and low temperature resistant EPDM compound, and the preparation method comprises the following steps: S1, mixing the terpolymer, fumed nano-silica and flexible long-chain molecular bridge coupling agent under a first high temperature condition to obtain a first mixture; S2, after cooling the first mixture, adding end-vinyl polydimethylsiloxane, ionic network building aid and antioxidant and mixing under a second high temperature condition lower than the first high temperature condition to obtain a second mixture; S3, mixing the second mixture with a peroxide vulcanizing agent and a co-crosslinking agent under conditions below the decomposition temperature of the peroxide vulcanizing agent; S4, molding the final mixture at a vulcanization temperature.

[0013] Preferably, step S1 comprises mixing in an internal mixer, setting the rotor speed at 40-60 rpm; the mixing process comprises plasticizing EPDM, then dispersing the fumed nano-silica, and finally reactive mixing the flexible long-chain molecular bridge coupling agent; and controlling the discharge temperature at 150-160°C at the end of mixing to obtain the first mixture.

[0014] In step S1, by setting a higher mixing temperature and a specific feeding sequence, the main purpose is to promote the in-situ chemical grafting of the flexible long-chain molecular bridge coupling agent on the surface of the fumed nano-silica. First, EPDM is plasticized, then silica is added for preliminary dispersion, and finally the coupling agent is added. Under the action of high temperature and strong shear force at 150-160°C, the coupling agent can efficiently react with the hydroxyl groups on the surface of the silica to form stable chemical bonds.

[0015] Preferably, step S2 comprises mixing in an internal mixer, setting the rotor speed at 30-50 rpm, and mixing the obtained first mixture with the end-vinyl polydimethylsiloxane, ionic network building aid, and antioxidant at a temperature of 120-130°C to obtain a uniformly dispersed second mixture.

[0016] In step S2, after cooling the first mixture, the end-vinyl polydimethylsiloxane, ionic network building aid, and antioxidant are added. The purpose of this step is to uniformly disperse the precursors of the flexible network and ionic network into the filler / EPDM matrix that has been surface modified. By selecting a moderate temperature of 120-130°C, the system can have a relatively low viscosity to facilitate uniform mixing, and it is also far below the decomposition temperature of the peroxide vulcanizing agent, thereby avoiding premature crosslinking and ensuring good processing flowability of the second mixture.

[0017] Preferably, step S3 comprises mixing on an open mill, setting the roller surface temperature at 40-60°C; mixing the second mixture with the peroxide vulcanizing agent and the co-crosslinking agent at the temperature, and controlling the total mixing time within 3-5 minutes.

[0018] In step S3, the peroxide vulcanizing agent and the co-crosslinking agent are mixed in the open mill at low temperature (e.g., below 90℃). This step requires extremely high process control, and the core purpose is to safely and uniformly mix the active components that initiate the main network crosslinking into the system. The open environment and lower roller temperature of the open mill can effectively prevent local overheating and avoid premature decomposition of the vulcanizing agent, thus ensuring that the final mixture has sufficient storage stability and processing safety before being molded.

[0019] Preferably, step S4 includes: molding and vulcanizing the final mixture at a pressure of 15-20 MPa and a temperature of 170-180℃ for 10-15 minutes; and after the molding and vulcanization, a secondary vulcanization process is further included, and the conditions of the secondary vulcanization process are a temperature of 150-160℃ and a treatment time of 2-4 hours.

[0020] In step S4, the final curing and molding are achieved through high-temperature and high-pressure molding and vulcanization. At a vulcanization temperature of 170-180℃, the peroxide decomposes to generate active free radicals, which initiate crosslinking reactions of the unsaturated double bonds on the EPDM, the end-vinyl polydimethylsiloxane, the coupling agent, and the co-crosslinking agent, forming a stable EPDM-silicone covalent crosslinking network throughout the entire system. The subsequent secondary vulcanization process helps to further improve the crosslinking network, eliminate internal stress, and remove the by-products of the vulcanization reaction, so that the various properties of the material reach a final stable state.

[0021] The application also provides a use of the high and low temperature resistant EPDM rubber compound, and the use of the high and low temperature resistant EPDM rubber compound in preparing an automobile engine compartment sealing element, a new energy automobile battery pack sealing ring, or a petroleum drilling equipment sealing element.

[0022] In summary, the application includes at least one of the following beneficial technical effects: 1. The application weaves a flexible silicone network and a dynamic ionic network into a ternary covalent network of ethylene propylene diene rubber (EPDM), ultimately constructing a unique triple interpenetrating network structure. This gives the rubber compound excellent wide-temperature-range service capability, making it have excellent low-temperature flexibility and high-temperature stability. Compared with the prior art, which can only single-handedly improve the high-temperature resistance or low-temperature resistance, the application solves the technical bottleneck that traditional EPDM materials are difficult to simultaneously consider high-temperature and low-temperature performance.

[0023] 2. The application innovatively uses a flexible long-chain molecular bridge coupling agent to construct a flexible interface layer between the rigid nanofiller and the flexible rubber matrix. The introduction of this "flexible bridge" improves the overall strength and toughness of the material, especially the tear resistance and durability. This overcomes the inherent defects of traditional rigid coupling agents, which are prone to brittleness and poor reliability due to interface stress concentration.

[0024] 3. The preparation method of the present application comprises a special high-temperature in-situ grafting process. This step ensures that the flexible long-chain molecular bridge coupling agent can fully chemically bond on the surface of the nanofiller, thereby forming a stable and high-quality interface. It is the key to obtaining excellent material performance and long-term thermal stability. It effectively solves the problem of large performance fluctuations between batches and insufficient reliability caused by insufficient reaction and unstable interface bonding in traditional step mixing.

[0025] 4. The present application adopts a new preparation concept of "step-by-step construction and process decoupling", which effectively separates the formation of different network systems in time and temperature. The low-temperature safe vulcanization step completely separates the introduction and activation of the vulcanization system. This method not only realizes the precise control of the microstructure of the material, but also gives the rubber compound excellent processing safety. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The present application is a preparation method flowchart. DETAILED DESCRIPTION

[0027] The following will be described in detail in conjunction with the accompanying Figure 1 The present application will be further described in detail.

[0028] The raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0029] Example 1: The combined formula (mass fraction) is: 55 parts of ethylene-propylene-diene rubber; 16 parts of end-vinyl polydimethylsiloxane; 26 parts of fumed nano-silicon dioxide; 2.5 parts of flexible long-chain molecular bridge coupling agent; 1.8 parts of ionic network construction aid; 3.5 parts of peroxide vulcanizing agent; 1.2 parts of co-crosslinking agent; and 1.2 parts of antioxidant.

[0030] The preparation method is as follows: (1) In the internal mixer, set the rotor speed to 50 rpm and the upper plunger pressure to 0.6 MPa. First, add the ethylene-propylene-diene rubber and plasticize for 2 minutes, then add the fumed nano-silicon dioxide and mix for 5 minutes, and finally add the flexible long-chain molecular bridge coupling agent and continue to mix, controlling the discharge temperature at the end of mixing to be 155°C, to obtain a first mixture.

[0031] (2) After cooling the first mixture to room temperature, put it into the internal mixer again, set the rotor speed to 40 rpm and the upper plunger pressure to 0.5 MPa. At a temperature of 125°C, add the end-vinyl polydimethylsiloxane, ionic network construction aid and antioxidant, and mix for 6 minutes to obtain a second mixture with uniform dispersion.

[0032] (3) The second mixture was transferred to an open mill, and the roller surface temperature was set to 50°C and the roll gap was set to 1 mm. The peroxide vulcanizing agent and the co-crosslinking agent were added, and the roll wrapping and triangular wrapping operations were performed, and the mixing was performed for 4 minutes to uniformly mix the various additives, to obtain a final mixture.

[0033] (4) The final mixture was placed in a flat vulcanizing machine mold, and the mold pressing vulcanization was performed at a pressure of 17.5 MPa and a temperature of 175°C for 12 minutes. After demolding, the product was placed in an oven at 155°C for secondary vulcanization, and the treatment was performed for 3 hours to obtain a final product.

[0034] Example 2: The combined formula (mass parts) is as follows: ethylene-propylene-diene rubber: 44.4 parts; end-vinyl polydimethylsiloxane: 6.7 parts; fumed nano-silica: 13.3 parts; flexible long-chain molecular bridge coupling agent: 0.9 parts; ionic network construction aid: 0.4 parts; peroxide vulcanizing agent: 1.8 parts; co-crosslinking agent: 0.4 parts; antioxidant: 0.4 parts.

[0035] The preparation method is as follows: (1) In a Banbury mixer, the rotor speed was set to 40 rpm, and the upper plunger pressure was set to 0.5 MPa. First, the ethylene-propylene-diene rubber was plasticized, then the fumed nano-silica was mixed, and finally the flexible long-chain molecular bridge coupling agent was continuously mixed, and the discharge temperature at the end of the mixing was controlled to be 150°C, to obtain a first mixture.

[0036] (2) After the first mixture was cooled, it was again put into the Banbury mixer, and the rotor speed was set to 30 rpm and the upper plunger pressure was set to 0.4 MPa. The end-vinyl polydimethylsiloxane, the ionic network construction aid, and the antioxidant were added and mixed at a temperature of 120°C to obtain a second mixture.

[0037] (3) The second mixture was transferred to an open mill, and the roller surface temperature was set to 40°C. The peroxide vulcanizing agent and the co-crosslinking agent were added, and the mixing was performed for 3 minutes to obtain a final mixture.

[0038] (4) The final mixture was placed in a flat vulcanizing machine mold, and the mold pressing vulcanization was performed at a pressure of 15 MPa and a temperature of 170°C for 10 minutes. After demolding, the product was placed in an oven at 150°C for secondary vulcanization, and the treatment was performed for 2 hours to obtain a final product.

[0039] Example 3: The combined formula (mass fraction) is: ethylene-propylene-diene rubber: 64.9 parts; end-vinyl polydimethylsiloxane: 26.0 parts; fumed nano-silica: 39.0 parts; flexible long-chain molecular bridge coupling agent: 3.9 parts; ionic network construction aid: 3.2 parts; peroxide vulcanizing agent: 5.2 parts; co-crosslinking agent: 1.9 parts; antioxidant: 1.9 parts.

[0040] The preparation method is as follows: (1) In the internal mixer, the rotor speed is set to 60 rpm, and the upper plunger pressure is 0.7 MPa. First, the ethylene-propylene-diene rubber is plasticized, then the fumed nano-silica is mixed, and finally the flexible long-chain molecular bridge coupling agent is continuously mixed. The discharge temperature at the end of mixing is controlled to be 160°C, and a first mixture is obtained.

[0041] (2) After the first mixture is cooled, it is again put into the internal mixer, and the rotor speed is set to 50 rpm and the upper plunger pressure is 0.6 MPa. At a temperature of 130°C, end-vinyl polydimethylsiloxane, ionic network construction aid and antioxidant are added and mixed to obtain a second mixture.

[0042] (3) The second mixture is transferred to an open mill, and the roller surface temperature is set to 60°C. The peroxide vulcanizing agent and the co-crosslinking agent are added and mixed for 5 minutes to obtain a final mixture.

[0043] (4) The final mixture is placed in a flat vulcanizing machine mold and subjected to mold vulcanization at a pressure of 20 MPa and a temperature of 180°C for 15 minutes. After demolding, the product is placed in an oven at 160°C for secondary vulcanization for 4 hours to obtain a final product.

[0044] Comparative Example 1: Compared with Example 1, the difference is that the end-vinyl polydimethylsiloxane is not included in the formula, and the rest of the components and the preparation method are the same.

[0045] Comparative Example 2: Compared with Example 1, the difference is that the ionic network construction aid is not included in the formula, and the rest of the components and the preparation method are the same.

[0046] Comparative Example 3: Compared with Example 1, the difference is that the flexible long-chain molecular bridge coupling agent is not included in the formula, and the rest of the components and the preparation method are the same.

[0047] Comparative Example 4: Compared with Example 1, the difference is that the flexible long-chain molecular bridge coupling agent in the formula is replaced by an equal mass fraction of a traditional rigid coupling agent, vinyltrimethoxysilane, and the rest of the components and the preparation method are the same.

[0048] Comparative Example 5: The formulation is the same as Example 1, but the preparation method is different: the discharge temperature in step (1) is reduced from 155°C to 125°C, i.e. without a special high-temperature reactive mixing stage, and the remaining steps are the same.

[0049] Comparative Example 6: The formulation is the same as Example 1, but the preparation method is different: step (3) is cancelled, and the peroxide vulcanizing agent and co-crosslinking agent are added to the internal mixer in the last stage of step (2) and blended with other components at 125°C, and the remaining steps are the same.

[0050] Test Example 1: Purpose of the experiment: The purpose of this experiment is to verify the key synergistic effect of the flexible silicone network and the dynamic ionic network on improving the comprehensive performance of the material at high and low temperatures by comparing the physical properties of Example 1, Comparative Example 1 and Comparative Example 2. Specifically, by removing the flexible silicone network (Comparative Example 1) and the dynamic ionic network (Comparative Example 2), the influence of the two on the low-temperature flexibility and high-temperature compression resilience of the material is investigated.

[0051] Experimental materials and instruments: Experimental materials: rubber sheets (2mm thick) prepared and vulcanized according to the formulations and methods of Example 1, Comparative Example 1 and Comparative Example 2.

[0052] Main instruments: electronic tensile testing machine, compression set testing device (including compressor, gasket), constant-temperature air drying oven (oven), low-temperature brittleness temperature tester.

[0053] The experimental steps are as follows: Sample preparation: From the vulcanized rubber sheets of Example 1, Comparative Example 1 and Comparative Example 2, use a standard cutting knife to cut the required samples.

[0054] Mechanical property testing: cut dumbbell-shaped tensile samples according to GB / T-528 standard, and cut 5 effective samples for each sample. Cut right-angle-shaped tear samples according to GB / T-529 standard, and cut 5 effective samples for each sample.

[0055] High-temperature compression set testing: cut circular samples with a diameter of 29.0mm according to GB / T-7759.1 standard, and prepare 3 samples for each sample.

[0056] Low-temperature brittleness temperature testing: cut long strip-shaped samples according to GB / T-1682 standard, and cut 10 samples for each sample.

[0057] All test specimens were conditioned for at least 16 hours in a standard laboratory environment (temperature 23 ± 2°C, relative humidity 50 ± 5%) prior to testing.

[0058] Mechanical property testing: The dumbbell-shaped specimens were clamped in an electronic tensile testing machine, and tensile test was performed at a tensile speed of 500 mm / min, and the tensile strength and elongation at break were recorded.

[0059] The right-angle-shaped specimens were clamped in an electronic tensile testing machine, and tear test was performed at a tensile speed of 500 mm / min, and the tear strength was recorded.

[0060] The arithmetic mean of 5 test results for each sample was taken.

[0061] High temperature compression set test: The original thickness of each circular specimen was measured; The specimen was placed in the compressor, and a constant compression strain of 25% was applied; The compressor with the specimen was placed in an oven preheated to 150°C, and the timer was set for 72 hours; After the aging was completed, the compressor was taken out of the oven, the specimen was removed within 30 minutes, and was placed in a standard laboratory environment for recovery for 30 minutes; The final thickness of the recovered specimen was measured, and the compression set rate was calculated according to the formula.

[0062] Low temperature brittleness temperature test: The cold bath temperature of the low temperature brittleness temperature tester was set at a higher estimated temperature (for example, -30°C); A group of 10 specimens were clamped on the instrument clamps, and were cooled in the cold bath for 3 minutes; The impact hammer was started to impact the specimen at a specified speed; Whether the specimen was broken, cracked or cracked was checked, and the number of damaged specimens was recorded; The cold bath temperature was lowered by 5°C or 2°C as a step, and the above cooling and impact steps were repeated until all the specimens were damaged; According to the damage rate at different temperatures, the temperature at which 50% of the specimens were damaged was calculated and determined, which was the low temperature brittleness temperature of the material.

[0063] Experimental data is shown in Table 1: Table 1: Performance comparison data of Example 1 and Comparative Examples 1-2 Experimental summary: From the experimental data shown in Table 1, it can be seen that the material prepared by the technical scheme (Example 1) provided by the application has excellent tensile strength, elongation at break and tear strength, and exhibits excellent high-low temperature comprehensive performance. The balanced and unified performance is due to the unique "covalent crosslinking network-flexible silicone network-dynamic ionic network" triple interpenetrating network structure successfully constructed in the EPDM matrix.

[0064] By comparing Example 1 with Comparative Example 1, it can be found that the low-temperature brittleness temperature of the material is significantly increased from -58℃ to -41℃ after the absence of the end-vinyl polydimethylsiloxane component. This clearly reveals the key role of the flexible silicone network. In the system of the application, the end-vinyl polydimethylsiloxane participates in the vulcanization reaction through its terminal vinyl group, and weaves the flexible Si-O-Si main chain with extremely low glass transition temperature into the EPDM network in a chemical bond manner, forming a molecular-level "flexible spring" network. The presence of the network greatly improves the movement ability of the polymer chain at low temperature, thereby giving the material excellent low-temperature flexibility, and confirming the indispensability of the flexible network in the application.

[0065] Further comparing the results of Example 1 and Comparative Example 2, after removing the ionic network construction aid in the formula, the high-temperature compression set of the material is sharply deteriorated from 18.3% to 45.7%, and the mechanical strength also decreases obviously. This powerfully confirms the key contribution of the dynamic ionic network. In the design of the application, the ionic network construction aid forms physical ionic cluster crosslinking points in the matrix. The network has the characteristics of dynamic reversibility. At high temperature, these ionic bonds can dissociate and recombine, effectively relaxing stress and dissipating energy to resist permanent deformation, thereby giving the material excellent high-temperature resilience and sealing reliability. The experimental data fully show that the presence of this dynamic energy dissipation network enables the material of the application to withstand severe high-temperature tests.

[0066] Test Example 2: Experimental purpose: The experiment aims to verify the superiority of the application of the flexible long-chain molecular bridge coupling agent (i.e. constructing a "flexible bridge" interface) compared with not using a coupling agent or using a traditional rigid coupling agent by comparing the performance differences of Example 1, Comparative Example 3 and Comparative Example 4. The experiment will focus on the effects of different interface treatment methods on the mechanical properties, dynamic mechanical properties and wear resistance of the material.

[0067] Experimental materials and instruments: Experimental materials: The vulcanized rubber sheets (thickness 2 mm) and blocks prepared according to the formulations and methods of Example 1, Comparative Example 3 and Comparative Example 4.

[0068] Main instruments: Electronic tensile testing machine, Dynamic mechanical analyzer (DMA), DIN abrasion testing machine.

[0069] Experimental procedure is as follows: Sample preparation: From the vulcanized rubber sheets or blocks of Example 1, Comparative Example 3 and Comparative Example 4, use standard cutting knife or mold to prepare the required samples.

[0070] Mechanical property testing: Cut dumbbell-shaped tensile samples according to GB / T-528, and cut angle-shaped tear samples according to GB / T-529, 5 samples for each sample.

[0071] Dynamic mechanical property analysis: Cut long strip-shaped samples with size of 30 mm x 6 mm x 2 mm, 3 samples for each sample.

[0072] Abrasion resistance testing: Drill cylindrical samples with diameter of 16 mm and thickness of at least 6 mm from the vulcanized rubber blocks according to GB / T-9867, 3 samples for each sample.

[0073] All samples are stored in standard laboratory environment (temperature 23 ± 2℃, relative humidity 50 ± 5%) for at least 16 hours before testing.

[0074] Mechanical property testing: According to the same steps and parameters in Test Example 1, test the tensile strength, elongation at break and tear strength of each group of samples, and take the arithmetic mean value; Dynamic mechanical property analysis: Clamp the long strip-shaped samples on the tensile mode clamp of the DMA instrument; Set the test program: the scanning temperature range is -80℃ to 50℃, the temperature rising rate is 3℃ / min, the test frequency is 1Hz, and the strain is 0.1%; During the test, the instrument automatically records the changes of storage modulus (E ， ) and loss factor (tan δ) with temperature; Determine the glass transition temperature (Tg) of the material from the temperature corresponding to the peak value of the loss factor (tan δ), and record the peak height of tan δ; Abrasion resistance testing: Weigh the initial mass of each cylindrical sample; Clamp the sample on the rotating clamp of the DIN abrasion testing machine and apply a normal load of 10N; Start the instrument and move the sample over a 40 m abrasion path on the specified type of sandpaper; After the test, remove the sample and clean the surface with a brush to remove the surface glue scraps, then weigh the final mass again, calculate the mass loss; according to the density of the sample, convert the mass loss into the abrasion volume loss.

[0075] The experimental data are shown in Table 2: Table 2: Performance comparison data of Example 1 and Comparative Examples 3-4 Experimental summary: The experimental data in Table 2 powerfully demonstrate the significant superiority of the adopted "flexible bridge" interface technology. Compared with Comparative Example 3 without any coupling agent and Comparative Example 4 using a traditional rigid coupling agent, Example 1 using a flexible long-chain molecular bridge coupling agent shows overall leadership in key performance indicators such as tensile strength, elongation at break, tear strength, and wear resistance. The results clearly show that building a high-quality filler-matrix interface, especially using the flexible interface proposed in the present application, is the core of realizing high performance of materials.

[0076] Comparing Example 1 with Comparative Example 3, the performance difference is huge. In the absence of a coupling agent, there is a lack of effective chemical connection between the fumed nano-silica and the EPDM rubber matrix, and the interfacial bonding force is extremely weak, resulting in ineffective stress transmission. This makes the reinforcing effect of the filler unable to be exerted, and instead it may become a defect point of stress concentration, ultimately resulting in a sharp decline in mechanical properties and serious deterioration of wear resistance. This confirms that effective bonding between the filler and the matrix is a basic prerequisite for the enhancement effect of nano-fillers.

[0077] More critically, the comparison between Example 1 and Comparative Example 4 directly reveals the innovative value of the "flexible bridge" concept of the present application. Compared with the "hard" connection formed by traditional rigid coupling agents, the flexible long-chain molecular bridge coupling agent used in the present application builds a unique flexible transition layer between the rigid nano-filler and the flexible rubber matrix. When the material is stressed, this flexible interface layer can deform in coordination with the matrix, effectively buffering and dissipating the stress concentration from the surface of the rigid filler, thereby preventing the generation and propagation of micro-cracks. This endows the material with higher toughness (reflected in significantly higher elongation at break and tear strength) and more excellent wear resistance. At the same time, the higher tan δ peak of Example 1 also confirms that this flexible interface has stronger internal friction and energy dissipation capacity, which is the microscopic mechanical manifestation of the improvement of material toughness.

[0078] Test Example 3: Experimental purpose: The experiment aims to verify the necessity and advancement of the "step-by-step construction, process decoupling" preparation process designed by the application by comparing the processing and physical properties of Example 1, Comparative Example 5 and Comparative Example 6. The experiment will focus on the influence of the high-temperature in-situ grafting step on the final material properties, and the decisive role of the low-temperature safe curing step on the processing safety of the rubber compound.

[0079] Experimental materials and instruments: Experimental materials: unvulcanized compounds prepared according to the formulations and methods of Example 1, Comparative Example 5 and Comparative Example 6; rubber sheets (2mm thick) vulcanized from the compounds of Example 1 and Comparative Example 5. (Note: the compound of Comparative Example 6 is expected to have scorch during the mixing stage, and cannot be used for subsequent vulcanization and testing.) Main instruments: Mooney viscometer, electronic tensile testing machine, constant temperature air drying oven (hot air aging oven).

[0080] The experimental steps are as follows: Sample preparation: Processing safety performance test: directly sample from the unvulcanized compounds prepared in Example 1, Comparative Example 5 and Comparative Example 6.

[0081] Mechanical properties and aging performance test: vulcanize the unvulcanized compounds of Example 1 and Comparative Example 5 on a flat vulcanizing machine to form 2mm thick rubber sheets. Then, according to GB / T-528 standard, cut dumbbell-shaped tensile samples, and cut enough number (at least 10) of samples for each sample.

[0082] All samples are placed in a standard laboratory environment (temperature 23±2℃, relative humidity 50±5%) for at least 16 hours before testing.

[0083] Processing safety performance test: Put the unvulcanized compound samples of each group into the Mooney viscometer which has been preheated to 125℃.

[0084] After preheating for 1 minute, start the rotor and record the change of Mooney viscosity value with time.

[0085] Determine and record the time required for the Mooney viscosity value to rise by 5 units from the minimum value, i.e. the Mooney scorch time (t5). This index directly reflects the early vulcanization resistance and operation safety of the compound during processing.

[0086] Mechanical property test: Take 5 dumbbell-shaped samples from the vulcanized rubber sheets of Example 1 and Comparative Example 5.

[0087] According to the same steps and parameters in Test Example 1, test the tensile strength and elongation at break on the electronic tensile testing machine, and take the arithmetic mean.

[0088] Hot air aging performance test: Another 5 dumbbell samples from the vulcanized rubber sheets of Example 1 and Comparative Example 5 were taken, and recorded as pre-aging samples.

[0089] The pre-aging samples were placed in a constant temperature blast drying oven preheated to 150°C, and subjected to a 168-hour hot air aging treatment.

[0090] After the aging was completed, the samples were taken out, cooled and rested in a standard laboratory environment for at least 16 hours.

[0091] The tensile strength and elongation at break of the aged samples were tested.

[0092] According to the test results before and after aging, the retention rates of tensile strength and elongation at break were calculated.

[0093] The experimental data are shown in Table 3: Table 3: Performance comparison data of Example 1 and Comparative Examples 5-6 Experimental summary: The experimental data in Table 3 reveal the absolute necessity and advancement of the "step-by-step construction, process decoupling" preparation process designed in the present application. By precisely separating the temperature and equipment for different chemical reaction stages, the process successfully solves the contradiction between processing safety and final performance commonly existing in the preparation of high-performance composites, and is the fundamental guarantee for realizing the material structure and performance designed in the present application.

[0094] The results of Comparative Example 6 intuitively show the decisive significance of the low-temperature safe sulfurization step in the present application. Since it blends the peroxide vulcanizing agent with other components in the mixer at 125°C, the vulcanizing agent decomposes prematurely at this temperature, causing severe early crosslinking (scorching). The extremely short Mooney scorch time (1.8 minutes) completely eliminates the subsequent molding ability. In sharp contrast, Example 1 completely separates the introduction and activation stages of the vulcanizing system through the innovative low-temperature mixer sulfurization step, ensuring sufficient processing safety time for the rubber compound, and proving the key role of the process design in ensuring the feasibility of industrial production.

[0095] The performance difference between Example 1 and Comparative Example 5 strongly proves the necessity of the high-temperature in-situ grafting step. Comparative Example 5, due to the lack of a special high-temperature reactive mixing stage, the chemical grafting reaction between the flexible long-chain molecular bridge coupling agent and the fumed nano-silica is extremely insufficient, resulting in insufficient interfacial bonding strength. This is not only directly reflected in the significant reduction of the initial mechanical properties (tensile strength and elongation at break), but more seriously, this weak interface becomes a "soft spot" during the heat aging process, which is easily damaged at high temperature, thus causing a sharp decline in the retention rate of mechanical properties after aging. The high-temperature mixing process used in Example 1, however, ensures the complete construction of the "flexible bridge" interface, forming a stable and firm chemical bonding.

[0096] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are only by way of example and that changes, modifications, substitutions and alterations can be made thereto without departing from the spirit and scope of the application as defined in the following claims, and their equivalents.

Claims

1. A high and low temperature resistant EPDM compound, characterized in that, The components include the following mass fractions: Ethylene-propylene-diene rubber: 44.4-64.9 parts; end-vinyl polydimethylsiloxane: 6.7-26.0 parts; fumed nanosilica: 13.3-39.0 parts; flexible long-chain molecular bridge coupling agent: 0.9-3.9 parts; ionic network building aid: 0.4-3.2 parts; peroxide vulcanizing agent: 1.8-5.2 parts; co-crosslinking agent: 0.4-1.9 parts; antioxidant: 0.4-1.9 parts.

2. A high and low temperature resistant EPDM compound according to claim 1, characterized in that, The ethylene content of the ethylene-propylene-diene rubber is 55-70%, the third monomer of the ethylene-propylene-diene rubber is ethylidene norbornene; the dynamic viscosity of the end-vinyl polydimethylsiloxane is 500-2000 mPa·s; the specific surface area of the fumed nano-silica is 180-220 m 2 / g.

3. The high and low temperature resistant EPDM compound according to claim 1, characterized in that, The flexible long-chain molecular bridge coupling agent is a vinyl polyoxyethylene ether-based trialkoxysilane; the ionic network building aid is zinc stearate or zinc acrylate; and the peroxide vulcanizing agent is di-2-tert-butyl peroxyisopropyl-benzene peroxide.

4. The high and low temperature resistant EPDM compound according to claim 1, characterized in that, The co-crosslinking agent is triallyl isocyanurate; and the antioxidant is a composite of a hindered phenolic antioxidant and a phosphite antioxidant.

5. A process for the preparation of a high and low temperature resistant EPDM compound, for the preparation of a high and low temperature resistant EPDM compound according to any one of claims 1 to 4, characterized in that, The preparation method comprises: S1. Mixing ethylene-propylene-diene rubber, fumed nanosilica, and a flexible long-chain molecular bridge coupling agent under a first high-temperature condition to obtain a first mixture; S2. After cooling the first mixture, adding end-vinyl polydimethylsiloxane, an ionic network building aid, and an antioxidant under a second high-temperature condition lower than the first high-temperature condition to mix to obtain a second mixture; S3. Adding a peroxide vulcanizing agent and a co-crosslinking agent to the second mixture under a condition lower than the decomposition temperature of the peroxide vulcanizing agent to mix; S4. Molding the finally obtained mixture under a vulcanization temperature.

6. A process for preparing a high and low temperature resistant EPDM compound according to claim 5, characterized in that, Step S1 comprises mixing in a Banbury mixer, setting the rotor speed to 40-60 rpm, sequentially plasticating the ethylene-propylene-diene rubber, dispersing the fumed nanosilica, and finally reactive mixing the flexible long-chain molecular bridge coupling agent, and controlling the discharge temperature at the end of mixing to be 150-160°C to obtain the first mixture.

7. A process for preparing a high and low temperature resistant EPDM compound as claimed in claim 5, characterized by, Step S2 comprises mixing in a Banbury mixer, setting the rotor speed to 30-50 rpm, and mixing the obtained first mixture with end-vinyl polydimethylsiloxane, an ionic network building aid, and an antioxidant under a temperature condition of 120-130°C to obtain a second mixture with uniform dispersion.

8. A process for preparing a high and low temperature resistant EPDM compound as claimed in claim 5, characterized by, Step S3 comprises mixing on an open mill, setting the roll surface temperature to 40-60°C, and mixing the second mixture with a peroxide vulcanizing agent and a co-crosslinking agent under the temperature condition, with the total mixing time controlled within 3-5 minutes.

9. A process for preparing a high and low temperature resistant EPDM compound as claimed in claim 5, characterized by, Step S4 comprises molding the finally obtained mixture under a pressure of 15-20 MPa and a temperature of 170-180°C for 10-15 minutes, and further comprising a secondary vulcanization process after the molding vulcanization, with the secondary vulcanization process being performed at a temperature of 150-160°C for 2-4 hours.

10. The use of a high and low temperature resistant EPDM compound according to any one of claims 1 to 4, characterized in that The application of the high-low temperature resistant EPDM compound in preparing automobile engine compartment sealing elements, new energy automobile battery pack sealing rings, or petroleum drilling equipment sealing elements.

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