Magnetic rubber composition, preparation method thereof and sealing strip

Abstract

The invention discloses a magnetic rubber composition, a preparation method thereof and a sealing strip, and belongs to the field of rubber materials. The composition takes ethylene propylene diene monomer as a matrix, and comprises 100-600 parts of modified samarium iron nitrogen, 15 parts of a silane coupling agent Si69, 0.7-1 part of a vulcanizing agent and 5-15 parts of a foaming agent, and 1-10 parts of epoxy grafted modified beta-CD can also be added. The modified samarium-iron-nitrogen is loaded and grafted, and then the sealing strip is prepared through the working procedures of mixing, vulcanizing, magnetizing and the like. According to the sealing strip, carbon black is replaced with the magnetic powder, the VOC release amount and the odor level are reduced, the mechanical property is improved, magnetic attraction force is given, and the problem of rebound deterioration of a traditional sealing strip is solved through surface modification of the magnetic powder.

Description

Technical Field

[0001] The present application relates to the field of rubber composition formulations, and in particular to a magnetic rubber composition, a preparation method thereof, and a sealing strip. Background Art

[0002] Traditional rubber sealing strips play a vital role in key areas such as automobiles and construction, where their performance directly impacts product safety, comfort, and durability. However, existing technologies face significant challenges in meeting growing environmental requirements and improving functionality.

[0003] In traditional sealing strip formulations, carbon black is widely used as the primary reinforcing agent. However, the carbon black production process (combustion and cracking of coal tar) results in high levels of residual volatile organic compounds (VOCs), particularly pentylene trialdehyde, which is accompanied by a pungent odor. During rubber product manufacturing, these VOCs are difficult to fully volatilize, resulting in excessive VOC emissions and substandard odor levels in the final product, posing a potential threat to the environment and human health. Furthermore, carbon black is bound to the EPDM matrix only through physical adsorption, resulting in limited interfacial compatibility. High filler loading can easily lead to agglomeration, which not only causes fluctuations in the material's mechanical properties but also causes stress concentration due to uneven filler dispersion, exacerbating compression set. Long-term use can lead to seal failure and deterioration in rebound performance, directly impacting the vehicle's NVH (noise, vibration, and harshness) performance.

[0004] Furthermore, traditional sealing strips are made of non-magnetic materials, which can deteriorate in resilience after prolonged compression, leading to seal failure and, in turn, increased NVH performance in vehicles. These seals fail to meet the stringent requirements of the modern automotive industry for high-quality, long-life seals. While some research has attempted to incorporate magnetic powders (such as ferrite), their poor compatibility with the rubber matrix and uneven dispersion have led to a significant decrease in mechanical properties (tensile strength dropping below 1 MPa), making them difficult to meet practical application requirements.

[0005] For magnetic attraction, the impact of uneven mixing is more direct and significant. The magnetic properties of magnetic powders depend on the uniform dispersion of particles in the matrix and their effective orientation under the action of an external magnetic field. After the unmodified powders are agglomerated, the directions of the magnetic domains within the aggregates cancel each other out due to the disordered accumulation of particles, forming a "magnetic domain disorder zone", which makes the magnetism of this part of the powder unable to contribute to the overall magnetic field; at the same time, the gaps between the agglomerates will increase the magnetic resistance, hindering the conduction of magnetic flux, causing the magnetic field strength on the surface of the material to be greatly attenuated, and even the appearance of local non-magnetic areas, completely losing the stable adsorption capacity required for the seal, and unable to meet the requirements for magnetic attraction uniformity and durability in practical applications.

[0006] To address these technical challenges, this invention aims to develop a new, high-performance magnetic sealing strip. The core goal is to fundamentally address VOC and odor issues by innovatively introducing magnetic powder to replace traditional carbon black. This approach also provides the product with a unique magnetic attraction and significantly improves its long-term rebound performance and overall mechanical properties, meeting market demand for high-performance, environmentally friendly sealing materials. Summary of the Invention

[0007] This invention addresses existing issues such as uneven mixing of magnetic powders, which can lead to weak mechanical and magnetic properties, or the impact of large-scale carbon black use on VOC levels in sealing strips. By introducing magnetic powders to replace traditional carbon black, this invention fundamentally addresses VOC and odor issues. A unique modification method also imparts enhanced magnetic attraction, thereby improving the long-term resilience and overall mechanical properties of the sealing strip. A related preparation method has been developed, and the resulting sealing strip is produced.

[0008] A magnetic rubber composition, characterized in that, in parts by mass, it comprises: EPDM rubber, 100 parts; Modified samarium iron nitrogen (Sm2Fe 17 N3), 100-600 copies; Silane coupling agent (Si69), 15 parts; Sulfur, 0.7-2 parts; Foaming agent (OBSH), 5-15 parts.

[0009] Specifically, the modified samarium iron nitrogen is: Sm2Fe 17 N3@D-NH2.

[0010] Specifically, the Sm2Fe 17 The preparation method of N3@D-NH2 includes: Sm2Fe 17 N3 was ultrasonically dispersed in water and added into the amino-terminated polyamidoamine solution, and then ultrasonically treated at 60°C for 6 hours to obtain the obtained product.

[0011] Specifically, the modified samarium iron nitrogen is: Si69-Sm2Fe 17 N3@D-NH2.

[0012] Specifically, the Si69-Sm2Fe 17 The preparation method of N3@D-NH2 includes: 17 N3@D-NH2 particles and coupling agent Si69 were fully dispersed in anhydrous ethanol in an ultrasonic bath at 45 °C for 4-5 h before preparation.

[0013] Specifically, 1-10 parts of epoxy grafted modified β-CD are further added to the composition.

[0014] Specifically, the epoxy compound for epoxy-grafted modified β-CD is: .

[0015] Specifically, the preparation method of the epoxy-grafted modified β-CD includes: adding β-CD to a mixed solvent of water / DMF (volume ratio of 5:5), adding NaOH to adjust the pH, stirring evenly, heating to 60-80°C, then slowly adding an epoxy compound dropwise and keeping the temperature for reaction for 16-24 hours, and adjusting the pH to 6-7 with acid after the reaction is completed.

[0016] A method for preparing a magnetic rubber composition comprises the steps of mixing, vulcanizing and magnetizing the magnetic rubber composition.

[0017] A sealing strip is prepared by subjecting the magnetic rubber composition to the processes of mixing, extruding, vulcanizing and magnetizing. Beneficial effects

[0018] 1. Conventional sealing strip formulations use carbon black for reinforcement. Carbon black is produced by the combustion and cracking of coal tar. This combustion is incomplete, resulting in a high content of VOC (pentanaldehyde) and a pungent odor. During the rubber manufacturing process, this easily evaporates, causing VOC odor to substandard. The sealing strips in this application are reinforced with magnetic powder, which has excellent physical properties and no pentanaldehyde odor. The manufacturing process also eliminates carbon black, eliminating the residual carbon black raw material and improving the VOC odor problem.

[0019] 2. The product of this application is a magnetic sealing strip made by adding samarium iron nitrogen magnetic powder to EPDM rubber, and then undergoing mixing, vulcanization, magnetization and other processes. The suction force has achieved an innovative breakthrough from scratch compared to traditional products, avoiding the problem of deterioration of the sealing strip's rebound performance due to long-term extrusion, which further leads to increased NVH in the car, and can better meet actual application requirements.

[0020] 3. In order to overcome the disadvantage of magnetic powder being easily aggregated in rubber and maximize its reinforcement effect, the present invention introduces a new surface modification strategy. 17 N3 powder is loaded on amino-terminated polyamidoamine (D-NH2), which reduces the Sm2Fe 17 The agglomeration of N3 powder provides a uniformly dispersed particle surface for subsequent coupling agent modification. Then the coupling agent Si69 is used to modify Sm2Fe 17 N3@D-NH2, the coupling agent is chemically bonded to the Sm2Fe 17 The hydroxyl groups on the surface of N3@D-NH2 are connected to further enhance the Sm2Fe 17 The dispersion effect of N3@D-NH2 greatly enhances the interfacial bonding strength between magnetic powder and rubber matrix.

[0021] 4. Cyclodextrin is added to the rubber as a physical adsorbent for VOCs. In order to improve the surface hydrophilicity of cyclodextrin, the present invention adopts epoxy grafting modification to improve the surface hydrophilicity of cyclodextrin, thereby dispersing cyclodextrin in the rubber matrix, thereby achieving the goal of reducing VOCs and improving the mechanical properties of the sealing strip.

[0022] 5. After the rubber materials are evenly blended, Si69-Sm2Fe 17 The free silyl groups avoided by N3@D-NH2 can be grafted onto the remaining hydroxyl groups on the surface of the epoxy-grafted β-CD, further enhancing the dispersion of the epoxy-grafted β-CD. Driven by hydrophobic forces, hydrogen bonds, and van der Waals forces, the amino-terminated polyamidoamine molecular chains penetrate the cavities of multiple cyclodextrin molecules, thereby locking the modified cyclodextrin onto the "branches" of the amino-terminated polyamidoamine.

[0023] 6. After the rubber compound of this application is extruded, during the vulcanization stage, Si69-Sm2Fe 17 The S4 bonds on the surface of N3@D-NH2 are unevenly cracked into disulfides and polysulfides at high temperatures. The sulfides can cross-link with the double bonds on the EPDM side chains to form a vulcanization network, and the polysulfides can react with the double bonds of the epoxy compounds on the surface of the epoxy-grafted modified β-CD to link the epoxy-grafted modified β-CD and the rubber molecular chain, thereby improving the vulcanization effect of the rubber. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope image of Comparative Example 2.

[0025] Figure 2 This is a scanning electron microscope image of Comparative Example 7.

[0026] Figure 3 This is a scanning electron microscope image of Example 10.

[0027] Figure 4 This is a scanning electron microscope image of Example 13.

[0028] Figure 5 This is a product photo of the sample of Example 7 after the compression permanent deformation test (the concave deformation is obvious).

[0029] Figure 6 This is a product photograph of the sample of Example 13 after the compression permanent deformation test (almost no concave deformation). DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] Sm2Fe 17 Preparation of N3@D-NH2: 2.50 kg Sm2Fe 17 N3 powder was placed in 50 kg of deionized water and fully dispersed in an ultrasonic bath at 80 ° C for 20 minutes. The suspension was then slowly added to 7.0 L of amino-terminated polyamide-amine solution dissolved in 10 kg of deionized water and ultrasonicated again at 60 ° C for 6 hours. Sm2Fe was separated from the solution by magnetic separation. 17 The N3@D-NH2 particles were washed repeatedly with ethanol and deionized water and finally dried at 50 °C under vacuum for 6 h.

[0032] The amino-terminated polyamidoamine is a 5.0 generation amino-terminated polyamidoamine.

[0033] Si69-Sm2Fe 17 Preparation of N3@D-NH2: 1.2 kg of Sm2Fe 17 N3@D-NH2 particles and 1.2 kg of coupling agent Si69 were fully dispersed in 5 kg of anhydrous ethanol in a 45 ° C ultrasonic bath for 4-5 hours. After cooling to room temperature naturally, Si69-Sm2Fe was separated from the solution by magnetic separation. 17 N3@D-NH2 particles were repeatedly washed with ethanol and deionized water and dried to obtain Si69-Sm2Fe 17 N3@D-NH2.

[0034] Preparation of epoxy-grafted modified β-CD: 1 kg of β-CD is placed in a three-necked flask containing 10 L of a water / DMF (volume ratio 5:5) mixed solvent. 1 L of a 0.1 mol NaOH aqueous solution is slowly added, stirred evenly, and then heated to 60-80°C. Subsequently, 1.5-2.0 kg of an epoxy compound is slowly added dropwise. After completion, the reaction is incubated for 16-24 hours. After completion of the reaction, the pH is adjusted to 6-7 with an acid, and then the mixture is washed with water at least twice and dried to obtain the epoxy-grafted modified β-CD.

[0035] The structure of the epoxy compound described in this application is as follows. The compound was prepared by referring to the method described in Example 2 of WO2015133840A2.

[0036] Formula of magnetic EPDM sealing strip: in parts by mass (all parts are by mass unless otherwise specified in this application), EPDM rubber, 100 parts; modified samarium iron nitrogen, 300-600 parts; silane coupling agent (Si69), 15 parts; foaming agent (OBSH), 7 parts; paraffin oil (plasticizer), 20 parts; calcium carbonate (reinforcement agent), 50-80 parts; zinc oxide (vulcanization activator), 5; stearic acid (vulcanization activator), 1 part; antioxidant (MB), 1-2 parts; nitrosamine-free accelerator ZBPD-50, 3-4 parts, ZBEC-70, 1-2 parts; sulfur, 0.7-2 parts.

[0037] The formula of traditional EPDM sealing strip: EPDM, 100 parts; carbon black, 120 parts; calcium carbonate, 80 parts; zinc oxide, 5~9 parts; stearic acid, 1 part; PEG4000, 2~4 parts; foaming agent OBSH, 4~10 parts; accelerator M, 1~1.2 parts; accelerator ZDBC-80, 1~2 parts; accelerator ZDEC-75, 0.5~1 parts; accelerator DPTT-70, 0.5~1 parts; sulfur, 0.8~2 parts.

[0038] The magnetic formulation used in this application utilizes a nitrosamine-free accelerator (a combination of ZBPD-50 and ZBEC-70). Conventional formulations use accelerators like ZDBC-80 and ZDEC-75, which contain thiocarbamates. These accelerators can decompose during vulcanization to produce carcinogenic nitrosamines, posing health risks. Nitrosamine-free accelerators completely eliminate this issue and meet stringent environmental standards, including EU REACH and China's GB 4806.

[0039] Furthermore, traditional formulas contain a large amount of carbon black, resulting in products that are limited to black, failing to meet requirements for light or colorful appearances. However, the magnetic formula in this application contains no carbon black and primarily consists of light-colored modified samarium iron nitrogen and calcium carbonate as fillers. By adding masterbatches, colors can be flexibly adjusted, adapting to diverse appearance designs and expanding application scenarios.

[0040] Due to the process requirements of this application, a sulfur + vulcanization accelerator formulation is recommended over a peroxide vulcanization system. This is because during hot air vulcanization and microwave vulcanization, the temperature / rate mismatch between OBSH foaming and peroxide crosslinking occurs. Furthermore, chemical interference and the presence of an aerobic environment lead to insufficient crosslinking. OBSH decomposes and foams at relatively low temperatures (150-160°C), before the peroxide has significantly decomposed (the internal temperature may not even reach 170°C), and the rubber crosslink network has yet to develop sufficient strength. Gas expansion can break through the weak, uncrosslinked rubber, causing cell rupture, merging, or structural collapse. Ultimately, the foamed product will develop holes and uneven density.

[0041] The process of magnetic EPDM sealing strip: through mixing, vulcanization, magnetization and other processes, optimize the pre-vulcanization time and temperature to ensure uniform pore structure and intact magnetic function.

[0042] Mixing: put all raw materials into the internal mixer at the same time according to the formula ratio for mixing. The mixing temperature is gradually increased from 130℃ to 160±5℃. The upper plug is vented 3 times. The upper plug pressure is 48±5MPA. The mixing time is 4±1 minutes. After the mixing is completed, the glue is discharged and the mixer is cooled to ≤30℃.

[0043] Vulcanization: The sealing strips are produced using an extrusion vulcanization process. The rubber compound is extruded through an extruder and sequentially undergoes high-temperature vulcanization, microwave vulcanization, and hot air vulcanization, followed by air cooling. High-temperature vulcanization is performed in a 3-meter-long high-temperature chamber at a temperature of 370-380°C; microwave vulcanization is performed in a 9-meter-long microwave chamber at a temperature of 230-240°C; and hot air vulcanization is performed in a three-section hot air chamber, each 9 meters long, at a temperature of 270-280°C. The extruded rubber compound passes through the high-temperature chamber, microwave chamber, and hot air chamber at a speed of 8-10 meters per minute. This continuous vulcanization process allows for the full reaction of the various accelerators and vulcanizers. Finally, the compound passes through an 18-meter-long air cooling chamber for cooling and dissipation, resulting in a lower VOC odor. After cooling, the product is cut to length to produce the sealing strips, which are then hung and baked for dissipation. Specifically, the cut sealing strips are hung on the vehicle frame and baked in an oven at a temperature of 70-80°C for 3.5-4.5 hours. The air is exhausted every hour to fully dissipate the odor of the strips, thereby obtaining low-VOC rubber sealing strips.

[0044] The test specimens were vulcanized using a compression molding process at a temperature of 180°C for 5 minutes using a 20cm x 20cm die. After vulcanization, the specimens were cut to suit the test standards.

[0045] Magnetization: Magnetization is carried out on a single-pole or multi-pole magnetizer.

[0046] Sample conditioning: After standing for a period of time in the rubber testing environment specified in GB / T 2941-2006, the following parameters are tested according to relevant standards. The units of each parameter are attached: Magnetic attraction force / N: Fix a 100 mm magnetic strip to a non-magnetic bracket. Place an ST12 cold-rolled steel plate (size: 100 mm × 50 mm × 1 mm) in contact with the surface of the magnetic strip. Use an electronic push-pull force gauge (accuracy ±0.01 N) to slowly separate the strips vertically and record the maximum pulling force.

[0047] VOC emission (μg / m³): Test temperature: Sampling bag temperature 40±2°C, holding time 4.5h±5min. Sampling tube capture conditions: Volatile organic compound TENAX tube, sampling rate 0.2L / min, sampling time 15min, sampling volume 3L; Aldehyde and ketone adsorption tube DNPH tube, sampling rate 0.8L / min, sampling time 30min, sampling volume 24L.

[0048] Odor Rating / Grade: Place the sample in a test container without adding water. Securely cap the container and place in a preheated electric constant-temperature forced-air drying oven. Heat to (80±2)°C for (2 hours ± 10 minutes). Then remove the container from the oven and cool it back to (60±5)°C before evaluating. During evaluation, place your nose against the edge of the open bottle, with the edge between your nose and lips, and your nose approximately 2-3 cm from the bottle opening. The bottle cap should be opened for no more than 10 seconds, and the evaluator should inhale normally. Odor Rating Method: Grade 1: No odor; Grade 2: Slight odor, but not disturbing; Grade 3: Noticeable odor, but not disturbing; Grade 4: Disturbing odor; Grade 5: Strong, disturbing odor; Grade 6: Unbearable odor. Data is accurate to one decimal place. Five evaluators will evaluate the sample and provide their individual comments.

[0049] Compression set (70℃*96h) / %: Refer to GB / T7759.1-2015.

[0050] Tensile strength / MPa, elongation / %: refer to GB / T528-2009.

[0051] Tear strength / (kN / m): Refer to GB / T529-2008.

[0052] Simulated door opening and closing test: Refer to QC / T 323-2007 for opening and closing durability test.

[0053] Comparative Example 1: EPDM, 100 parts; carbon black, 120 parts; calcium carbonate, 80 parts; zinc oxide, 5 parts; stearic acid, 1 part; PEG4000, 2 parts; blowing agent OBSH, 7 parts; accelerator M, 1 part; accelerator ZDBC-80, 1 part; accelerator ZDEC-75, 0.5 part; accelerator DPTT-70, 0.5 part; sulfur S-80, 1 part. Specimens were prepared through mixing and vulcanization processes. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0054] Comparative Example 2: EPDM, 100 parts; carbon black, 220 parts; calcium carbonate, 80 parts; zinc oxide, 9 parts; stearic acid, 1 part; PEG4000, 4 parts; blowing agent OBSH, 10 parts; accelerator M, 1.2 parts; accelerator ZDBC-80, 2 parts; accelerator ZDEC-75, 1 part; accelerator DPTT-70, 1 part; sulfur S-80, 2 parts. Specimens were prepared through mixing and vulcanization processes. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0055] Comparative Example 3: EPDM, 100 parts; carbon black, 120 parts; calcium carbonate, 80 parts; zinc oxide, 9 parts; stearic acid, 1 part; PEG4000, 4 parts; blowing agent OBSH, 10 parts; accelerator M, 1.2 parts; accelerator ZDBC-80, 2 parts; accelerator ZDEC-75, 1 part; accelerator DPTT-70, 1 part; sulfur S-80, 2 parts. Specimens were prepared through mixing and vulcanization processes. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0056] Comparative Example 4: EPDM, 100 parts; carbon black, 120 parts; calcium carbonate, 80 parts; zinc oxide, 5 parts; stearic acid, 1 part; PEG4000, 2 parts; OBSH, 7 parts; BIBP, 0.7 parts; MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. Specimens were prepared through mixing and vulcanization, with optimized pre-vulcanization time and temperature to ensure uniform cell structure.

[0057] Comparative Example 5: EPDM, 100 parts; carbon black, 120 parts; calcium carbonate, 80 parts; zinc oxide, 5 parts; stearic acid, 1 part; PEG4000, 2 parts; blowing agent OBSH, 7 parts; peroxide curing agent BIBP, 2 parts; antioxidant (MB), 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. Specimens were produced through mixing and vulcanization processes, with optimized pre-vulcanization time and temperature to ensure a uniform cell structure.

[0058] Comparative Example 6: EPDM, 100 parts; carbon black, 120 parts; calcium carbonate, 80 parts; silane coupling agent Si69, 15 parts; zinc oxide, 5 parts; stearic acid, 1 part; PEG4000, 2 parts; blowing agent OBSH, 7 parts; sulfur S-80, 2 parts and 1 part; antioxidant (MB), 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. Specimens were produced through mixing and vulcanization processes. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0059] Comparative Example 7: EPDM, 100 parts; carbon black, 120 parts; calcium carbonate, 80 parts; silane coupling agent Si69, 15 parts; zinc oxide, 5 parts; stearic acid, 1 part; PEG4000, 2 parts; blowing agent OBSH, 7 parts; sulfur S-80, 2 parts; antioxidant (MB), 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. During preparation, the silane coupling agent Si69 and carbon black were first mixed in a high-speed disperser and then kneaded. The strips were then vulcanized to produce the desired profile. The pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0060] Example 1: EPDM rubber, 100 parts; SmFeN, 300 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. A sample bar was prepared through mixing, vulcanization, and magnetization. The pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0061] Example 2: EPDM rubber, 100 parts; SmFeN, 100 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. A sample bar was prepared through mixing, vulcanization, and magnetization. The pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0062] Example 3: EPDM rubber, 100 parts; SmFeN, 600 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. A sample bar was prepared through mixing, vulcanization, and magnetization. The pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0063] Example 4: EPDM rubber, 100 parts; Sm2Fe 17 N3@D-NH2, 300 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0064] Example 5: EPDM rubber, 100 parts; Sm2Fe 17 N3@D-NH2, 100 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0065] Example 6: EPDM rubber, 100 parts; Sm2Fe 17 N3@D-NH2, 600 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0066] Example 7: EPDM rubber, 100 parts; Sm2Fe 17 N3, 300 parts; amino-terminated polyamidoamine, 20L; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. Samples were prepared through mixing, vulcanization, and magnetization. The pre-vulcanization time and temperature were optimized to ensure a uniform cell structure (in this example, 1 part by mass = 1 kg).

[0067] Example 8: EPDM rubber, 100 parts; Sm2Fe 17 N3, 300 parts; amino-terminated polyamidoamine, 40L; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. Samples were prepared through mixing, vulcanization, and magnetization. The pre-vulcanization time and temperature were optimized to ensure a uniform cell structure (in this example, 1 part by mass = 1 kg).

[0068] Example 9: EPDM rubber, 100 parts; Sm2Fe 17N3, 600 parts; amino-terminated polyamidoamine, 40L; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. Specimens were prepared through mixing, vulcanization, and magnetization. The pre-vulcanization time and temperature were optimized to ensure a uniform cell structure (in this example, 1 part by mass = 1 kg).

[0069] Example 10: EPDM rubber, 100 parts; Si69-Sm2Fe 17 N3@D-NH2, 300 parts; sulfur S-80, 2 parts; OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0070] Example 11: EPDM rubber, 100 parts; Si69-Sm2Fe 17 N3@D-NH2, 100 parts; sulfur S-80, 2 parts; OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0071] Example 12: EPDM rubber, 100 parts; Si69-Sm2Fe 17 N3@D-NH2, 600 parts; sulfur S-80, 2 parts; OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0072] Example 13: EPDM rubber, 100 parts; Si69-Sm2Fe 17 N3@D-NH2, 300 parts; epoxy-grafted β-CD, 5 parts; sulfur S-80, 2 parts; OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0073] Example 14: EPDM rubber, 100 parts; Si69-Sm2Fe 17 N3@D-NH2, 300 parts; epoxy-grafted β-CD, 1 part; sulfur S-80, 2 parts; OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0074] Example 15: EPDM rubber, 100 parts; Si69-Sm2Fe 17 N3@D-NH2, 600 parts; epoxy-grafted modified β-CD, 5 parts; sulfur S-80, 2 parts; OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0075] Example 16: EPDM rubber, 100 parts; Sm2Fe 17 N3@D-NH2, 300 parts; epoxy-grafted modified β-CD, 5 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0076] Example 17: EPDM rubber, 100 parts; Sm2Fe 17 N3, 300 parts; amino-terminated polyamidoamine, 30L; epoxy-grafted modified β-CD, 5 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. Samples were prepared through mixing, vulcanization, and magnetization. The pre-vulcanization time and temperature were optimized to ensure a uniform cell structure (in this example, 1 part by mass = 1 kg).

[0077] Example 18: EPDM rubber, 100 parts; Sm2Fe 17N3, 300 parts; amino-terminated polyamide-amine, 30L; epoxy grafted modified β-CD, 5 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; foaming agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. When preparing, first use a high-speed disperser to mix the silane coupling agent Si69 and Sm2Fe 17 After N3 is mixed, the sample strips are prepared through mixing, vulcanization, magnetization and other processes, and the pre-vulcanization time and temperature are optimized to ensure uniform pore structure (in this embodiment, 1 mass part = 1 kg).

[0078] Example 19: EPDM rubber, 100 parts; Si69-Sm2Fe 17 N3@D-NH2, 300 parts; β-CD, 5 parts; sulfur S-80, 2 parts; OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0079] Example 20: EPDM rubber, 100 parts; Si69-Sm2Fe 17 N3@D-NH2, 300 parts; β-CD, 1 part; sulfur S-80, 2 parts; OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0080] Example 21: EPDM rubber, 100 parts; Si69-Sm2Fe 17 N3@D-NH2, 600 parts; β-CD, 5 parts; sulfur S-80, 2 parts; OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. Specimens were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0081] Example 22: EPDM rubber, 100 parts; Sm2Fe 17N3@D-NH2, 300 parts; β-CD, 5 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; and ZBEC-70, 2 parts. The bars were produced through mixing, vulcanization, and magnetization. Pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0082] Example 23: EPDM rubber, 100 parts; Sm2Fe 17 N3, 300 parts; amino-terminated polyamidoamine, 30L; β-CD, 5 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. Samples were prepared through mixing, vulcanization, and magnetization. The pre-vulcanization time and temperature were optimized to ensure a uniform cell structure (in this example, 1 part by mass = 1 kg).

[0083] Example 24: EPDM rubber, 100 parts; Sm2Fe 17 N3, 300 parts; amino-terminated polyamide-amine, 30L; β-CD, 5 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; foaming agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. When preparing, first use a high-speed disperser to mix the silane coupling agent Si69 and Sm2Fe 17 After N3 is mixed, the sample strips are prepared through mixing, vulcanization, magnetization and other processes, and the pre-vulcanization time and temperature are optimized to ensure uniform pore structure (in this embodiment, 1 mass part = 1 kg).

[0084] Example 25: EPDM rubber, 100 parts; Sm2Fe 17 N3, 300 parts; amino-terminated polyamide-amine, 30L; β-CD, 5 parts; epoxy compound 8 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; foaming agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. When preparing, first use a high-speed disperser to mix the silane coupling agent Si69 and Sm2Fe 17 After N3, β-CD and epoxy compound are mixed respectively, the sample strips are prepared through mixing, vulcanization, magnetization and other processes. The pre-vulcanization time and temperature are optimized to ensure a uniform pore structure (in this embodiment, 1 part by mass = 1 kg).

[0085] Example 26: EPDM rubber, 100 parts; Sm2Fe 17 N3, 300 parts; β-CD, 5 parts; epoxy compound 8 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; foaming agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. When preparing, first use a high-speed disperser to mix the silane coupling agent Si69 and Sm2Fe 17 After N3, β-CD and epoxy compound are mixed respectively, the sample strips are prepared through mixing, vulcanization, magnetization and other processes. The pre-vulcanization time and temperature are optimized to ensure a uniform pore structure (in this embodiment, 1 part by mass = 1 kg).

[0086] Example 27: EPDM rubber, 100 parts; barium ferrite magnetic powder, 400 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. A sample bar was prepared through mixing, vulcanization, and magnetization. The pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0087] Example 28: EPDM rubber, 100 parts; strontium ferrite magnetic powder, 500 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. A sample bar was prepared through mixing, vulcanization, and magnetization. The pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0088] Example 29: EPDM rubber, 100 parts; cobalt-nickel ferrite magnetic powder, 430 parts; silane coupling agent Si69, 15 parts; sulfur S-80, 2 parts; blowing agent OBSH, 7 parts; paraffin oil, 20 parts; calcium carbonate, 60 parts; zinc oxide, 5 parts; stearic acid, 1 part; antioxidant MB, 2 parts; ZBPD-50, 4 parts; ZBEC-70, 2 parts. A sample bar was prepared through mixing, vulcanization, and magnetization. The pre-vulcanization time and temperature were optimized to ensure a uniform cell structure.

[0089] The spline related data are recorded in the following table:

[0090] The key differences between Comparative Examples 1-3 lie in the carbon black dosage (120 phr for Comparative Examples 1 and 3, 220 phr for Comparative Example 2) and the ratio of vulcanization accelerators. Sulfur vulcanization, through accelerators (such as M and ZDBC), triggers sulfur ring cleavage, forming polysulfide crosslinks (-Sx-, where x = 2-6) with double bonds in the EPDM molecular chain. These crosslinks have low bond energies (approximately 270 kJ / mol) and poor thermal stability. They are prone to breakage and rearrangement under dynamic stress or high temperatures, resulting in high compression set (46% for Comparative Examples 1 and 3, 58% for Comparative Example 2). At the filler-matrix interface, the bond between carbon black and EPDM is primarily driven by van der Waals forces, resulting in weak interfacial bonding energies (approximately 8-10 mJ / m²). When the carbon black dosage is increased to 220 phr (Comparative Example 2), the maximum inclusion threshold of EPDM is far exceeded, and the interparticle distance decreases to below the critical agglomeration distance, forming numerous micron-sized aggregates. These agglomerates act as stress concentration points, not only causing the tensile strength to drop to 0.89 MPa, but also destroying the continuity of the rubber matrix, causing the elongation to drop sharply to 43%. At the same time, due to the high proportion of carbon black filling and the gaps between the agglomerates, the VOC volatilization channels are increased, resulting in the VOC release of Comparative Example 2 reaching 205, confirming the deteriorating effect of poor dispersion under high filling on the overall performance.

[0091] Comparative Examples 4-5 switch to a peroxide vulcanization system (BIPB). The core reason for its insufficient performance is mainly due to the inherent contradiction between this system and the OBSH foaming agent. First, the benzenesulfonamide by-products produced during the decomposition of OBSH will undergo a quenching reaction with the free radicals produced by the decomposition of BIBP, consuming a large number of effective free radicals and significantly reducing the crosslinking efficiency. Among them, there are only 0.7 parts of BIBP in Comparative Example 4, which is insufficient in dosage itself. After the free radical quenching, the crosslinking density is extremely low. Although the increase of BIBP to 2 parts in Comparative Example 5 can partially offset the effect, the continuous interference of by-products still makes the crosslinking efficiency far lower than the theoretical value; secondly, the decomposition temperatures of the two do not match. OBSH can release a large amount of gas at 150-160°C, while the effective vulcanization temperature of BIBP is about 175°C. During hot air vulcanization, the internal temperature of the rubber rises lags, resulting in BIBP not yet being greatly heated when OBSH foams. The amount of BIBP decomposes rapidly, the cross-linking network strength is insufficient, and the gas easily breaks through the inadequately cross-linked rubber, causing problems such as bubble rupture and collapse. Even if the amount of BIBP is increased in Comparative Example 5, the time difference of "foaming before cross-linking" cannot be solved. When BIBP decomposes rapidly at high temperature, OBSH has completed most of the foaming. Violent cross-linking may squeeze the bubbles and cause structural defects. In addition, the peroxide system lacks an adaptive vulcanization regulation mechanism. ZBEC-70 cannot play a role in the peroxide system and may even aggravate free radical quenching. It cannot coordinately adjust the vulcanization rhythm to match the foaming process through multiple accelerators like the sulfur system. At the same time, the amount of BIBP used in Comparative Example 4 is too little, resulting in insufficient cross-linking. The excessive amount in Comparative Example 5 triggers a sudden rise in local temperature, causing explosive foaming of OBSH and even leading to rupture of EPDM molecular chains, further deteriorating the bubble structure and mechanical properties of the product.

[0092] The experimental data of Comparative Examples 6-7 show that the addition of silane coupling agent Si69 significantly improves the mechanical properties of carbon black reinforced EPDM. Compared with Comparative Examples 4 and 5, the tensile strength, elongation and tear strength of Comparative Example 6 are all improved, and the compression permanent deformation is reduced. This is attributed to the fact that Si69 promotes the interfacial bonding between carbon black and the rubber matrix. In Comparative Example 7, Si69 and carbon black are pre-mixed in a high-speed disperser before mixing. Its tensile strength, elongation and tear strength all reach the highest values ​​in the comparative example group, and the compression permanent deformation is also the lowest. This shows that the effective effect of the silane coupling agent depends on its sufficient contact and reaction with the filler. Pretreatment can significantly improve the dispersion and interfacial bonding of the filler, thereby maximizing the reinforcement effect. Although the VOC emission and odor level decreased after replacing the nitrosamine-free vulcanization accelerator, they still remained at a high level, once again emphasizing the characteristics of carbon black as the source of the fundamental problem.

[0093] Next, we comprehensively analyze Examples 1-3. Through data comparison, we can clearly see that before surface modification, the addition of SmFeN magnetic powder gives the sealing strip a certain magnetic attraction, realizing a function that traditional sealing strips do not have. The magnetic attraction increases with the increase of magnetic powder content. However, too high a magnetic powder content (600 parts in Example 3) has a negative impact on the mechanical properties, resulting in a decrease in tensile strength, elongation and tear strength, and an increase in compression permanent set. This indicates that the unmodified magnetic powder has agglomeration problem in the rubber, and a high filling amount will destroy the continuity of the rubber matrix and reduce its mechanical properties. The VOC emission and odor level are significantly improved compared with the traditional carbon black reinforcement system, but are still at a high level, which shows that simply replacing carbon black cannot completely solve the VOC problem and further strategies are needed.

[0094] Next, we examine Examples 27-29. Compared to SmFeN powder, the sealing strips prepared with barium ferrite, strontium ferrite, and cobalt-nickel ferrite powders, at similar or higher loadings, generally exhibit lower magnetic attraction (1.64-1.85) and no significant mechanical performance advantage. This confirms the superiority of SmFeN powder in providing high magnetic performance. Furthermore, the VOC and odor levels of these powders are similar to those of unmodified SmFeN powder, reaffirming that while the powders themselves do not contain pentyltrialdehyde, their VOC adsorption capacity is limited.

[0095] Next, we see Examples 4-6, where we disperse Sm2Fe 17 N3 is loaded on D-NH2 (Sm2Fe 17 After the addition of D-NH2 (N3@D-NH2), all performance properties of the sealing strip were significantly improved. Compared with Examples 1-3 (unmodified magnetic powder), Examples 4-6 showed significant increases in tensile strength, elongation, and tear strength, a significant decrease in compression set, and a significant improvement in magnetic attraction. For example, the tensile strength of Example 4 (300 parts modified magnetic powder) reached 2.31, significantly higher than the 1.27 of Example 1 (300 parts unmodified magnetic powder). This indicates that D-NH2 modification effectively reduced magnetic powder agglomeration and improved its dispersion in the rubber matrix, thereby enhancing the reinforcement effect and the effective utilization of the magnetic powder. VOC emissions and odor levels remained at similar levels compared to Examples 1-3 (unmodified magnetic powder), indicating that D-NH2 modification primarily focused on improving mechanical properties and magnetic attraction, with limited direct adsorption of VOCs.

[0096] Further analysis of Examples 7-9 shows that although the addition of D-NH2 during the mixing process improves the magnetic attraction (1.98N in Example 7 is higher than 1.65N in Example 1), its mechanical properties are far inferior to those of the magnetic powder pre-loaded with D-NH2 (Examples 4-6). In addition, the tear strength of Example 7 is 9.4, which is much lower than 18.6 in Example 4. This highlights the importance of ultrasonic dispersion pretreatment of Sm2Fe 17 The importance of N3 and D-NH2 is demonstrated. This step ensures a more even dispersion of the magnetic powder on the D-NH2 "branches," resulting in superior dispersion and reinforcement. VOC and odor levels remained at similar levels compared to Examples 1-3.

[0097] Examples 10-12 are based on the D-NH2 modification (Examples 4-6), and further use Si69 to modify Sm2Fe 17 N3@D-NH2 modified (Si69-Sm2Fe 17 N3@D-NH2), the performance of the sealing strip was significantly improved. Compared with Examples 4-6 (modified with D-NH2 alone), Examples 10-12 achieved higher tensile strength, elongation, and tear strength, further reduced compression set, and significantly enhanced magnetic attraction. Example 10 achieved a tensile strength of 2.85 MPa, an elongation of 214%, a tear strength of 28.5 kN / m, and a magnetic attraction of 3.44 N. These values ​​far exceeded those of all carbon black control examples and Examples 4-6 (modified with D-NH2 alone). Example 11, with a magnetic powder content of only 100 parts per million, exhibited inferior mechanical and magnetic properties to those of Examples 10 and 12, demonstrating that insufficient filler content has limited impact on rubber performance. In Example 12, when the magnetic powder content was 600 parts, the magnetic attraction force reached 3.65N, indicating that the magnetic attraction force showed a certain positive correlation with the overall filling amount of samarium iron nitrogen magnetic powder. However, the obvious decline in mechanical properties may be because a large amount of magnetic powder filling "diluted" the molecular chain of the rubber, resulting in excessive filling, thereby worsening the mechanical properties of the rubber. This shows that Si69 further improved the dispersion effect of the magnetic powder and the interfacial bonding force with the rubber matrix through chemical bonding, forming a stronger rubber network. At the same time, the VOC emission was also greatly reduced to 85-91, and the odor level dropped from 4.5 to 4, which may be because Si69 has a strong effect on Sm2Fe 17 The alcohol generated during N3@D-NH2 modification has been released and will no longer be brought into the rubber matrix, thereby reducing the overall VOC of the sealing strip.

[0098] Examples 13-15 are Si69-Sm2Fe 17On the basis of N3@D-NH2, after adding epoxy grafted modified β-CD, the VOC emission and odor level of the sealing strip are better improved. The VOC emission of Example 13 is as low as 38, and the odor level reaches 3, which is much lower than all other examples and comparison examples. This fully demonstrates the excellent effect of epoxy grafted modified β-CD as a VOC physical adsorbent. At the same time, the mechanical properties are also further improved. The tensile strength of Example 13 reaches 2.95MPa, the elongation is 241%, the tear strength is 30.4kN / m, and the compression permanent deformation is as low as 27%, which are the best performances among all experimental groups. When the magnetic powder content of Example 15 is 600 parts, the magnetic attraction force reaches 4.21N and the tear strength is 23.4kN / m, which shows the synergistic improvement of the magnetic attraction force and tear strength of epoxy grafted modified β-CD at high magnetic powder content, but it has a negative impact on the mechanical properties of the material.

[0099] The unique molecular structure of cyclodextrin (β-CD), namely the hydrophobic inner cavity and the hydrophilic outer surface, makes it an ideal VOC molecular adsorbent, which can effectively capture and reduce the release of volatile organic compounds through a subtle inclusion effect. The surface hydrophilicity of β-CD is significantly improved through epoxy grafting modification, thereby greatly enhancing its compatibility and affinity with the EPDM rubber matrix, ensuring that cyclodextrin is more evenly and stably dispersed in the polymer network, and effectively exerts its adsorption function and participates in the vulcanization cross-linking network, thereby synergistically improving the overall mechanical properties of the sealing strip. During the rubber compound blending process, Si69-Sm2Fe 17 The unreacted free silyl groups on the surface of N3@D-NH2 can undergo grafting reaction with the remaining hydroxyl groups on the surface of epoxy-grafted modified β-CD, promoting the uniform dispersion of epoxy-grafted modified β-CD. At the same time, driven by multiple forces such as hydrophobic force, hydrogen bond and van der Waals force, the molecular chain of the amino-terminated polyamide-amine cleverly shuttles through and "locks" the cavities of multiple cyclodextrin molecules, forming a unique "dendritic" structure, thereby stably anchoring the modified cyclodextrin in the polymer system, further optimizing its dispersion effect and adsorption efficiency. In addition, in the subsequent vulcanization stage, Si69-Sm2Fe 17 N3@DN H2 Under high temperatures, the surface S4 bonds undergo uneven cleavage, generating active disulfides and polysulfides. These sulfides not only cross-link with double bonds on the EPDM molecular chains to build a vulcanization network, but the polysulfides also chemically bond with the double bonds of the epoxy compounds on the surface of the epoxy-grafted β-CD, tightly connecting the modified cyclodextrin to the rubber molecular chains. This significantly improves the vulcanization efficiency of the rubber and the mechanical properties of the final product. Experimental data (such as Example 13) fully demonstrates that when the epoxy-grafted β-CD is used at a dosage of 5 phr, it exhibits the most significant synergistic effect in both VOC reduction and mechanical property improvement.

[0100] The formula of Example 16 is prepared by adding D-NH2 modified magnetic powder, epoxy grafted modified β-CD and silane coupling agent Si69 respectively. Compared with Example 13 in which the magnetic powder is pre-modified with Si69, Example 16 shows almost the same level of magnetic attraction and the tear strength is also relatively close. However, in terms of overall mechanical properties, especially tensile strength and elongation, the data of Example 16 is slightly lower than that of Example 13. The reason may be that the introduction method of silane coupling agent Si69 affects the dispersion of magnetic powder and the efficiency of interface bonding. In Example 13, Si69 is pre-modified with Sm2Fe 17 N3@D-NH2 magnetic powder was modified for the second time to form Si69-Sm2Fe 17 N3@D-NH2 composite material is then added to the rubber matrix. This pre-grafting modification method allows Si69 to have sufficient time and a more ideal environment to fully react with the surface of the magnetic powder to form a stable and uniform chemical bonding layer. This not only effectively reduces the agglomeration of the magnetic powder and ensures its better dispersion in the rubber, but also maximizes the interfacial bonding force between the magnetic powder and the rubber molecular chain, thereby constructing a stronger and more uniform vulcanization network, significantly improving the tensile strength and elongation of the material. Example 16 uses Sm2Fe 17 N3@D-NH2 magnetic powder and Si69 were added in situ during the mixing process. Although Si69 is intended to promote the interaction between fillers and rubber, in the high viscosity and complex rubber mixing environment, Si69 may not be able to fully hydrolyze and form chemical bonds with the magnetic powder surface as it would in pre-modified conditions.

[0101] The formula components of Examples 17 and 18 are the same. The difference between the two lies in the preparation process: Before mixing, in Example 18, silane coupling agent Si69 and Sm2Fe 17N3 magnetic powder was pre-mixed. From the perspective of mechanical properties, the tensile strength of Example 18 is significantly higher than that of Example 17, the elongation is also higher than that of Example 17, the tear strength is far higher than that of Example 17, and the compression permanent deformation is also slightly improved. This clearly shows that the pre-mixing treatment of the silane coupling agent Si69 and the magnetic powder greatly improves the dispersion effect of the magnetic powder in the rubber matrix and the interfacial bonding force with the rubber molecular chain. Through pretreatment, Si69 can react more fully with the surface of the magnetic powder to form a stable siloxane bond, thereby more effectively exerting its coupling effect and enhancing the overall strength and toughness of the composite material. From the perspective of magnetic attraction, the magnetic attraction of Example 18 is slightly higher than that of Example 17, which further confirms that better magnetic powder dispersion contributes to the development of magnetic properties, and the magnetic attraction of Examples 17 and 18 is much higher than that of Examples 7 and 8. This may be because the introduction of epoxy grafted modified β-CD improves the dispersion of the overall system, indirectly improving the effective arrangement and magnetic properties of the magnetic powder. From the perspective of VOC emissions, Example 18 emits less VOC than Example 17, indicating that premixing Si69 with magnetic powder not only significantly improves mechanical properties and magnetic attraction, but also results in lower VOC emissions. This suggests that optimizing filler dispersion and interfacial bonding can more effectively encapsulate or reduce the release of volatile substances, thereby achieving better environmental performance.

[0102] Continuing to analyze Examples 19-22, we found that unmodified β-CD was significantly less effective in reducing VOC emissions than epoxy-grafted β-CD. Examples 19-21 exhibited significantly higher VOC emissions than Examples 13-15, and their mechanical properties were generally lower. For example, the tear strength of Example 19 was 18.2 kN / m, significantly lower than the 30.4 kN / m of Example 13, although the magnetic attraction remained high at 3.48 N. Example 21 achieved a magnetic attraction of 4.11 N at 600 phr of magnetic powder, but its tear strength was only 17 kN / m, significantly lower than the 23.4 kN / m of Example 15. This demonstrates that epoxy-grafted modification is crucial for improving the dispersibility of β-CD in rubber, enhancing its hydrophilicity, and strengthening its interaction with the rubber matrix. The hydrophilicity of unmodified β-CD may result in poor dispersion in hydrophobic rubber, limiting its adsorption capacity and contribution to mechanical properties.

[0103] Examples 25 and 26 mainly analyze the effects of the in-situ reaction of epoxy compounds with β-CD. These examples attempt to achieve in-situ modification by adding epoxy compounds and β-CD separately during the mixing process. Although the VOC emission is reduced, it is still higher than the example using pre-epoxy grafted modified β-CD. The mechanical properties also do not reach the optimal level. The magnetic attraction of Examples 25 and 26 is between 3.42-3.44N. Although the magnetic attraction is good, the tear strength is still lower than that of the best example. This shows that pre-epoxy grafting modification can ensure a better modification degree and dispersion effect of cyclodextrin, thereby maximizing its adsorption capacity for VOCs and the synergistic improvement of rubber properties.

[0104] Scanning electron microscopy (SEM) images show that Figure 1 (Comparative Example 2) utilizes a sulfur-cured system with 220 phr of highly filled carbon black. The SEM images reveal a large number of unevenly sized, scattered large pores on the material surface, as well as significant carbon black agglomeration, resulting in significant stress concentration areas. This is because the carbon black and EPDM matrix bond solely through physical adsorption. The surface energy differential under high filling levels exacerbates agglomeration, disrupting matrix continuity. Furthermore, the polysulfide bonds in sulfur-cured materials exhibit poor thermal stability and are prone to fracture under dynamic stress, further inducing matrix defects and deteriorating material mechanical properties (low tensile strength, high compression set) and VOC emissions (inter-agglomerate gaps serve as volatilization channels).

[0105] Figure 2 (Comparative Example 7) introduces the silane coupling agent Si69, and a high-speed disperser is used to pre-disperse the Si69 and carbon black. SEM images show that the density of the continuous phase of the material matrix has been further improved, the pore size is relatively uniform, and carbon black agglomeration has been significantly improved compared to Comparative Example 2, although traces of minor agglomeration remain. The high-speed disperser should have been able to more evenly coat the carbon black surface with Si69 through strong shear forces, theoretically promoting the condensation of siloxy groups with carbon black hydroxyl groups and the participation of sulfide bonds in the vulcanization reaction, thus strengthening the interfacial bonding. However, due to the inherent differences between the polarity of carbon black and the non-polar EPDM matrix, even after pre-dispersion, interfacial interactions were not completely eliminated, and the coupling agent modification effect in some areas was less than ideal. This resulted in improved properties such as tensile strength and compression set, but not ultimate optimization, resulting in a transitional micromorphology that suggests progress in interfacial modification but still room for improvement.

[0106] Figure 3 (Example 10) demonstrates the use of Si69 pre-grafted modified samarium iron nitrogen to construct a chemically cross-linked "rubber-coupling agent-magnetic powder" network. The SEM image shows uniform dispersion of the magnetic powder, with small-sized dispersed phases densely distributed throughout the matrix. The pores are fine and regularly distributed, and the particle-matrix interface is tightly bonded. Si69 pre-grafting functionalizes the magnetic powder surface, improving compatibility with EPDM. The pre-dispersion process allows the coupling agent to uniformly coat the magnetic powder, strengthening interfacial chemical bridging. This increases cross-link density and magnetic domain orientation, optimizing properties such as tensile strength and magnetic attraction. The micromorphology accurately reflects the advantages of the "deep interface modification + process synergy" formula.

[0107] Figure 4 (Example 13) shows the introduction of epoxy-grafted β-CD, synergizing magnetic powder with the EPDM matrix. The SEM image shows extremely uniform filler dispersion, a dense matrix continuous phase with no obvious defects, good connectivity of fine pores, and tight, gapless interfacial bonding. The epoxy-grafted β-CD, through its host-guest interaction in the cavity, adsorbs VOCs, reducing emissions. Furthermore, the epoxy groups react with the double bonds of the EPDM to form additional crosslinks, strengthening network integrity. Microscopically, the synergistic effect of the functional additives optimizes dispersion and interfacial bonding, demonstrating the profound optimization of both microstructure and macroscopic properties achieved through the multi-additive synergistic modification of the formulation.

[0108] Figure 5 and Figure 6 Front door opening sealing strips made from the formulations of Comparative Example 7 and Example 13 (same structure, only different formulations) were installed on the vehicle and subjected to a simulated door opening and closing test using a robotic arm (referring to QC / T 323-2007). After the test was repeated 40,000 times (20,000 times each for inward and outward opening), the strips were removed for observation. It was clearly seen that the strips of Comparative Example 7 showed obvious compression depression, while the strips of Example 13 showed almost no depression.

[0109] We speculate that this may be because Comparative Example 7 uses carbon black as the primary filler. While Si69 coupling improves the carbon black-EPDM interface, the high carbon black filling easily leads to agglomeration, forming "hard agglomerate zones." Under cyclic stress, the agglomerate zones are prone to debonding from the matrix interface, inducing microcracks. Furthermore, the carbon black network is primarily based on physical adsorption, and molecular chains easily slip from the carbon black surface during repeated deformation, accelerating molecular chain breakage and cell collapse. Fatigue failure manifests as "progressive network destruction combined with cell structure collapse."

[0110] In Example 13, magnetic hybrid fillers and epoxy grafted β-CD were introduced to construct a multi-level reinforcement network. 17 In N3@D-NH2, one end of Si69 reacts with the EPDM double bond or epoxy double bond (sulfurization synergy), and the other end reacts with Sm2Fe through the D-NH2 functional group. 17The N3 magnetic phase is bonded to the interface, while the epoxy-grafted β-CD reacts with D-NH2 via the epoxy group to form a three-dimensional interpenetrating network of "magnetic particles-coupling agent-matrix-cyclodextrin". In this network, the magnetic particles act as "rigid nodes" to disperse stress, and the supramolecular inclusion complex of cyclodextrin (β-CD cavity) can "bind" the molecular chain and inhibit slippage. During the frequent opening and closing of the door, Sm2Fe 17 The magnetic domain reversal of the N3 magnetic particles temporarily stores mechanical energy (hysteresis effect). When stress is removed, the magnetic moments reorder, releasing energy and aiding elastic recovery. Simultaneously, the hybrid network's "supramolecular bonding + chemical crosslinking" synergizes the entropic elasticity of the molecular chain (EPDM backbone), supramolecular interactions (β-CD inclusion complexes), and magnetoelastic properties to disperse energy dissipation. Furthermore, the multi-level network enhances the support of the cell walls, making the OBSH foamed cells more susceptible to "elastic compression-recovery" during cyclic deformation, reducing irreversible energy loss due to cell rupture. Paraffin oil softens the matrix and synergizes with the cell structure, enabling dual recovery during cyclic deformation through cell and network elasticity, minimizing permanent deformation.

[0111] Overall, the present invention innovatively uses samarium iron nitrogen magnetic powder to replace traditional carbon black as a reinforcing agent, fundamentally eliminating the high VOC emissions and pungent odor problems caused by carbon black. Experimental data clearly shows that compared with the high VOC and high odor levels of carbon black reinforced sealing strips in the control group, the magnetic sealing strips of the present invention show significant improvements in VOC and odor, with the lowest VOC reaching 38μg / m 3 , odor level 3.

[0112] Secondly, through multi-stage surface modification of the magnetic powder, including ultrasonic dispersion of amino-terminated polyamidoamine (D-NH2) and secondary modification with the silane coupling agent Si69, the dispersion of the magnetic powder in the EPDM matrix and the interfacial bonding strength with the rubber are greatly improved. This series of modifications significantly enhances the mechanical properties of the sealing strip, such as tensile strength, elongation, tear strength, and compression set, and significantly increases magnetic attraction, achieving innovative functions not found in traditional sealing strips.

[0113] Finally, the introduction of epoxy-grafted β-CD is key to this invention's remarkable environmental performance. As a highly effective VOC physical adsorbent, the modified cyclodextrin reduces the sealing strip's VOC emissions to 38-49 and its odor level to 3-3.5, meeting industry-leading environmental standards. Furthermore, the epoxy-grafted β-CD further enhances the strip's overall mechanical properties through its improved dispersibility and cross-linking with rubber chains.

[0114] These data surpass all comparative examples and examples that did not fully implement the innovative solution, fully demonstrating the technical advantages and innovative breakthroughs of this invention in addressing VOC and odor issues, improving product rebound performance, reducing NVH, and imparting magnetic attraction. The magnetic sealing strip developed by this invention not only meets increasingly stringent environmental regulations but also, with its superior overall performance, provides a new solution for high-performance sealing materials in the automotive industry.

[0115] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A magnetic rubber composition, characterized in that: Calculated by mass, including: EPDM rubber, 100 parts; Modified samarium iron nitrogen (Sm2Fe 17 N3), 100-600 copies; Silane coupling agent (Si69), 15 parts; Sulfur, 0.7-2 parts; Foaming agent (OBSH), 5-15 parts.

2. A magnetic rubber composition according to claim 1, characterized in that: The modified samarium iron nitrogen is: Sm2Fe 17 N3@D-NH2.

3. A magnetic rubber composition according to claim 2, characterized in that: The Sm2Fe 17 The preparation method of N3@D-NH2 includes: Sm2Fe 17 N3 was ultrasonically dispersed in water and added into the amino-terminated polyamidoamine solution, and then ultrasonically treated at 60°C for 6 hours to obtain the obtained product.

4. The magnetic rubber composition according to claim 1, characterized in that: The modified samarium iron nitrogen is: Si69-Sm2Fe 17 N3@D-NH2.

5. The magnetic rubber composition according to claim 4, characterized in that: The Si69-Sm2Fe 17 The preparation method of N3@D-NH2 includes: 17 N3@D-NH2 particles and coupling agent Si69 were fully dispersed in anhydrous ethanol in an ultrasonic bath at 45 °C for 4-5 h before preparation.

6. The magnetic rubber composition according to claim 1, characterized in that: 1-10 parts of epoxy grafted modified β-CD are also added into the composition.

7. The magnetic rubber composition according to claim 6, characterized in that: The epoxy compound of the epoxy-grafted modified β-CD is: .

8. The magnetic rubber composition according to claim 7, characterized in that: The preparation method of the epoxy-grafted modified β-CD comprises: adding β-CD into a mixed solvent of water / DMF (volume ratio of 5:5), adding NaOH to adjust the pH, stirring evenly, heating to 60-80° C., then slowly adding an epoxy compound dropwise and keeping the temperature to react for 16-24 hours, and adjusting the pH to 6-7 with an acid after the reaction is completed.

9. A method for preparing a magnetic rubber composition, characterized in that: The magnetic rubber composition according to any one of claims 1 to 8 is prepared through mixing, vulcanization and magnetization processes.

10. A sealing strip, characterized in that: The magnetic rubber composition according to any one of claims 1 to 8 is prepared through mixing, extrusion, vulcanization and magnetization processes.

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