Samarium-iron-nitrogen magnetic EPDM foamed rubber composite material and preparation method thereof

Abstract

The invention relates to the field of functional polymer materials, and discloses a samarium-iron-nitrogen magnetic EPDM (Ethylene-Propylene-Diene Monomer) foamed rubber composite material and a preparation method thereof.The preparation method comprises the following steps: firstly, uniformly dispersing samarium-iron-nitrogen magnetic powder in an EPDM (Ethylene-Propylene-Diene Monomer) matrix by adopting a mechanical blending method, and forming a foamed rubber matrix with an open-pore or closed-pore structure by adopting a two-stage vulcanization process; and finally, magnetizing by adopting a single-sided multi-stage magnetizing device to obtain the magnetic EPDM foamed rubber composite material. According to the preparation method provided by the invention, the samarium-iron-nitrogen magnetic EPDM foamed rubber composite material with excellent magnetic property, good mechanical property and relatively high foaming ratio can be obtained, the sealing property can be improved by utilizing the excellent magnetic property, and the samarium-iron-nitrogen magnetic EPDM foamed rubber composite material has a good application prospect in the field of magnetic sealing.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional polymer material preparation, and particularly relates to a samarium-iron-nitrogen magnetic EPDM foamed rubber composite material and a preparation method thereof. BACKGROUND

[0002] In automobile manufacturing, door sealing strips, as an important sealing component, are widely used between the door and the body to prevent water, dust, noise and air penetration, thereby ensuring a comfortable driving experience inside the car. Although traditional rubber door sealing strips have good elasticity and sealing performance, their sealing effect is often limited by problems such as compression permanent deformation, aging and low-temperature embrittlement. For example, as the use time of the automobile is prolonged, the rubber material gradually loses elasticity, resulting in uneven contact between the sealing strip and the door, thereby affecting the sealing effect and increasing wind noise, rainwater penetration and other problems.

[0003] In order to improve the sealing effect of the sealing system, in recent years, researchers have tried to combine magnetic materials with rubber matrix to develop magnetic sponge rubber. This kind of material improves the stability and sealing performance of the door sealing strip by introducing magnetic powder into the rubber matrix. Generally, the magnetic materials introduced in the magnetic rubber mainly include barium ferrite, neodymium iron boron, samarium iron nitrogen and other common magnetic powders. Among them, samarium iron nitrogen (Sm2Fe 17 N3) permanent magnetic powder has high coercive force, good stability and easy orientation and bonding forming, and is very suitable for high-performance magnetic rubber. However, the interfacial compatibility and bonding strength between the magnetic powder and the EPDM rubber matrix are difficult to reach a satisfactory level. How to combine samarium iron nitrogen with rubber foaming material to obtain a composite material with good magnetic performance and excellent mechanical properties, especially in the magnetic foamed rubber material, how to ensure high foaming ratio while the composite material still has good mechanical properties, and at the same time avoid the problems of magnetic powder agglomeration and interface debonding in traditional magnetic foamed rubber, is still a technical problem.

[0004] CN104231448A discloses a kind of magnetic EPDM rubber, belongs to automobile parts processing technical field.The raw material composition of the rubber is: EPDM raw rubber 80~120 parts by weight, the ethylene content in the EPDM raw rubber is 57~77wt%;Carbon black 41~50 parts by weight;Paraffin oil 14~18 parts by weight;Magnetic powder 400~500 parts by weight;Surfactant 1~4 parts by weight.The magnetic EPDM rubber disclosed in the application has high filling amount, large residual magnetism and good processing performance, and can be used to make automobile sealing strip etc.The application solves the problem that the magnetic rubber in the prior art has small magnetism and poor processing performance, which cannot meet the needs of production and life, and further provides a kind of residual magnetism and good processing performance and its preparation method.But its magnetic powder type is traditional ferrite material, and the magnetic energy product is low, which leads to insufficient magnetic attraction of the obtained material.

[0005] CN118609981A relates to a flexible samarium-iron-nitrogen magnet and its preparation method and application, the preparation method of the flexible samarium-iron-nitrogen magnet includes the following steps: the samarium-iron-nitrogen magnetic powder is sequentially subjected to first coating treatment and second coating treatment, the obtained coated magnetic powder and the binder are sequentially subjected to mixing, crushing and calendering to obtain a samarium-iron-nitrogen magnetic sheet; the obtained samarium-iron-nitrogen magnetic sheet is magnetized to obtain the flexible samarium-iron-nitrogen magnet. The flexible samarium-iron-nitrogen magnet prepared by the application has excellent magnetic and mechanical properties, and the magnetic powder is not easy to fall off, which can meet the high performance requirements as a flexible magnet. However, this preparation method is mainly based on the binder system and the calendering process, and the obtained magnetic sheet has high hardness and limited flexibility, which does not have the ductility and elasticity required for rubber foaming.

[0006] The existing magnetic rubber foaming material still has great challenges in the balance of foaming ratio, magnetic performance and mechanical properties, especially in the field requiring high sealing performance, and there is still a lack of a magnetic foaming material that can effectively improve the sealing performance and comprehensive performance. SUMMARY

[0007] To solve the above problems, one of the main purposes of the present application is to provide a kind of samarium-iron-nitrogen magnetic EPDM foamed rubber composite material, which has excellent magnetic properties and good mechanical properties, and has high foaming ratio to improve the sealing performance.

[0008] To achieve the above purpose, the present application provides a kind of samarium-iron-nitrogen magnetic EPDM foamed rubber composite material, the magnetic rubber composite material includes the following raw materials by weight: 100 parts of EPDM raw rubber, 300-600 parts of magnetic filler, 10-20 parts of reinforcing filler, 10-30 parts of paraffin oil, 1-3 parts of sulfur, 3-7 parts of accelerator, 2-3 parts of stearic acid, 5-7 parts of zinc oxide, 3-9 parts of foaming agent, 10-60 parts of coupling agent.

[0009] The amount of the magnetic filler is preferably 300-500 parts by weight based on 100 parts by weight of the raw EPDM rubber. In some embodiments of the present application, the amount of the magnetic filler is 400 parts by weight based on 100 parts by weight of the raw EPDM rubber. The obtained Sm-Fe-N magnetic EPDM foamed rubber composite material has excellent magnetic properties and good mechanical properties.

[0010] Preferably, the raw EPDM rubber has a Mooney viscosity (ML(1+8) 150℃) of 60-70, an ethylene content of 40-50 wt%, and a third monomer (ENB) content of 6-10 wt%.

[0011] Preferably, the magnetic filler is Sm-Fe-N permanent magnetic powder, and the average particle size of the Sm-Fe-N permanent magnetic powder is 1-10 μm. The mass ratio of the magnetic filler to the coupling agent is preferably 100:2-9, and more preferably 100:3-5.

[0012] Preferably, the reinforcing filler is at least one of carbon black N550 and carbon black N774.

[0013] Preferably, the accelerator is selected from one or more of thiazole accelerators, thiuram accelerators, and dithiocarbamate accelerators.

[0014] Preferably, the foaming agent is at least one of azodicarbonamide, 4,4'-oxybisbenzenesulfonylhydrazide, and sodium bicarbonate.

[0015] Preferably, the coupling agent is at least one of bis-[gamma-(triethoxysilyl)propyl]tetrasulfide (Si69), vinyltriethoxysilane (A151), and isopropyl tri(dioctylpyrophosphato) titanate (KR-TTS).

[0016] The second object of the present application is to provide a preparation method of a Sm-Fe-N magnetic EPDM foamed rubber composite material, which comprises: S1 Plastication: placing the raw EPDM rubber into a kneader and performing kneading plastication under a closed condition; S2 Mixing: mixing half of the paraffin oil and the carbon black uniformly, and then feeding into the kneader to perform high-temperature kneading mixing under a closed condition, the mixing temperature is 100-130℃, and the mixing time is 3-8 minutes, then adding zinc oxide and stearic acid and continuing mixing for 3-8 minutes to obtain a uniform masterbatch; S3 secondary mixing: the masterbatch is transferred to an open mill for secondary mixing, the roller temperature is controlled at 50-80 DEG C, the samarium iron nitrogen magnetic filler modified by the coupling agent is mixed with the remaining half of the paraffin oil, then is slowly added into the masterbatch in 5-10 times, to ensure that the magnetic filler is uniformly dispersed, then the foaming agent, the vulcanizing agent and the accelerator are sequentially added, and mixing is carried out for 5-15 minutes until the mixture is uniformly obtained to obtain the mixed rubber; S4 pre-vulcanization: the mixed rubber sheet is placed in a mold, and one-stage vulcanization is carried out in a flat vulcanization machine, the temperature is 110-140 DEG C, the pressure is 10-15 MPa, and the time is 1-6 minutes; S5 two-stage foaming vulcanization: the pre-vulcanized sheet is transferred to a larger mold for foaming vulcanization, the temperature is 160-190 DEG C, and the time is 1-25 minutes; S6 magnetization: the foamed rubber after vulcanization is magnetized by using a single-sided multi-stage magnetizing device to obtain a samarium iron nitrogen magnetic EPDM foamed rubber composite.

[0017] The modified magnetic filler in S3 is prepared by the following method: coupling agent and anhydrous ethanol are mixed and hydrolyzed for 30 min, a certain amount of magnetic filler is poured into the mixed solution, mechanical stirring is carried out at room temperature for 2 h, and drying is carried out at a temperature of 40-70 DEG C for 12 h to obtain the modified magnetic filler.

[0018] The magnetic field strength of the single-sided multi-stage magnetizing device in S6 is 30000 GS.

[0019] The third object of the present application is to provide an application of the samarium iron nitrogen magnetic EPDM foamed rubber composite in the field of magnetic sealing. In the present application, the sealing system can be applied to the magnetic sealing structure of automobile doors, windows, building door and window seals and the like.

[0020] Compared with the prior art, the present application has the following beneficial effects: (1) The present application uses samarium iron nitrogen magnetic powder as the filler, and the magnetic powder is modified by a coupling agent through a wet surface modification method, which effectively improves the interfacial compatibility and bonding strength between the magnetic powder and the EPDM rubber matrix. Under the premise of ensuring a high foaming ratio, the composite material still has good mechanical properties, and the problems of magnetic powder agglomeration and interfacial debonding in traditional magnetic foamed rubber are improved.

[0021] (2) By introducing the modified samarium iron nitrogen magnetic powder into the EPDM foamed rubber, the composite material has high residual magnetic strength and coercive force, so that a stable magnetic attraction force of more than 2 N can be generated between the magnetic rubber and the metal part, and the self-adsorption capacity and sealing performance of the sealing system are enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The present application is a schematic diagram for testing the magnetic attraction force. DETAILED DESCRIPTION

[0023] The embodiments of the present application will be further described with reference to the following examples. However, the present application is not limited to this embodiment, and some non-essential improvements and adjustments made by those skilled in the art according to the content of the present application are still within the protection scope of the present application.

[0024] In the following examples and comparative examples, the accelerator 2-mercaptobenzothiazole (MBT) is simply referred to as accelerator M-80, the accelerator dipentamethylene thuram disulfide (DPTT) is simply referred to as accelerator DPTT-70, the accelerator zinc dibutyl dithiocarbamate (ZDBC) is simply referred to as ZDBC-80, the coupling agent bis-[gamma-(triethoxysilyl)propyl]tetrasulfide (Si69) is simply referred to as Si69, the coupling agent vinyltriethoxysilane (A151) is simply referred to as A151, the coupling agent isopropyl tri(dioctyl pyrophosphato) titanate (KR-TTS) is simply referred to as KR-TTS, and the foaming agent 4,4'-oxybisbenzenesulfonylhydrazide (OBSH) is simply referred to as OBSH-50. Example 1

[0025] A preparation method of a samarium iron nitride magnetic EPDM foamed rubber composite material, first, a modified magnetic filler is prepared: the coupling agent and anhydrous ethanol are mixed and hydrolyzed for 30 min, the samarium iron nitride is poured into the mixed solution, mechanical stirring at room temperature for 2 h, and drying at 60℃ for 12 h to obtain the modified magnetic filler.

[0026] The preparation method of the samarium iron nitride magnetic EPDM foamed rubber composite material specifically includes the following steps: S1 plastication: the raw EPDM rubber is put into a kneader for kneading plastication under closed conditions; S2 mixing: half of the paraffin oil is mixed with the carbon black, and then put into the kneader for high-temperature kneading mixing under closed conditions, the mixing temperature is 100℃, and the time is 6 minutes, then zinc oxide and stearic acid are added and continue to mix for 6 minutes to obtain a uniform masterbatch; S3 secondary mixing: the masterbatch is transferred to an open type rubber mixer for secondary mixing, the roller temperature is controlled at 60℃, the modified samarium iron nitride magnetic filler modified by the coupling agent is mixed with the remaining half of the paraffin oil, and then slowly added into the masterbatch in 10 times, to ensure that the magnetic filler is uniformly dispersed, then the foaming agent, the vulcanizing agent and the accelerator are added in sequence, each mixing for 8 minutes until the mixture is uniformly obtained to obtain a mixed rubber; S4 pre-vulcanization: the mixed rubber sheet is put into a mold for one-stage vulcanization in a flat vulcanizing machine, the temperature is 120℃, the pressure is 15 MPa, and the time is 1 minute; S5 two-stage foaming vulcanization: the pre-vulcanized rubber sheet is transferred to a larger mold for foaming vulcanization, the temperature is 170℃, and the time is 14 minutes. S6 Magnetization: A single-sided multi-stage magnetization device is used to magnetize the vulcanized foamed rubber to obtain a samarium iron nitrogen magnetic EPDM foamed rubber composite material. The magnetic field strength of the single-sided multi-stage magnetization device is 30000GS.

[0027] The raw materials include the following parts by weight: 100g of EPDM raw rubber; 1.3g of sulfur; 1.3g of accelerator MBT-80; 1g of accelerator DPTT-70; 1.1g of accelerator ZDBC-80; 7g of foaming agent OBSH-50; 15g of carbon black N550; 12.5g of paraffin oil; 7g of zinc oxide; 2g of stearic acid; 12g of coupling agent Si69; and 400g of samarium iron nitrogen. Example 2

[0028] Following the preparation method of Example 1, the materials underwent magnetic powder modification, mixing, secondary mixing, pre-vulcanization, and secondary foaming vulcanization. The difference in this example is that the amount of vulcanization system used is increased by 50%.

[0029] The raw materials include the following parts by weight: 100g of EPDM raw rubber; 2.0g of sulfur; 2.0g of accelerator MBT-80; 1.5g of accelerator DPTT-70; 1.7g of accelerator ZDBC-80; 7g of foaming agent OBSH-50; 15g of carbon black N550; 12.5g of paraffin oil; 7g of zinc oxide; 2g of stearic acid; 12g of coupling agent Si69; and 400g of samarium iron nitrogen. Example 3

[0030] The difference between this embodiment and Embodiment 2 is that the coupling agent used is A151.

[0031] The raw materials include the following parts by weight: 100g of EPDM raw rubber; 2.0g of sulfur; 2.0g of accelerator MBT-80; 1.5g of accelerator DPTT-70; 1.7g of accelerator ZDBC-80; 7g of foaming agent OBSH-50; 15g of carbon black N550; 12.5g of paraffin oil; 7g of zinc oxide; 2g of stearic acid; 12g of coupling agent A151; and 400g of samarium iron nitrogen. Example 4

[0032] The difference between this embodiment and Embodiment 1 is that the amount of samarium iron nitrogen magnetic powder is 300g.

[0033] The raw materials include the following parts by weight: 100g of EPDM raw rubber; 1.3g of sulfur; 1.3g of accelerator MBT-80; 1g of accelerator DPTT-70; 1.1g of accelerator ZDBC-80; 7g of foaming agent OBSH-50; 15g of carbon black N550; 12.5g of paraffin oil; 7g of zinc oxide; 2g of stearic acid; 12g of coupling agent Si69; and 300g of samarium iron nitrogen. Example 5

[0034] The difference between this embodiment and embodiment 3 is that the pre-vulcanization temperature is set to 110°C and the secondary vulcanization temperature is set to 170°C.

[0035] The raw materials include the following parts by weight: 100g of EPDM raw rubber; 2.0g of sulfur; 2.0g of accelerator MBT-80; 1.5g of accelerator DPTT-70; 1.7g of accelerator ZDBC-80; 7g of foaming agent OBSH-50; 15g of carbon black N550; 12.5g of paraffin oil; 7g of zinc oxide; 2g of stearic acid; 12g of coupling agent A151; and 400g of samarium iron nitrogen.

[0036] Comparative Example 1 The difference between this comparative example and Example 1 is that the mass of the magnetic filler samarium iron nitrogen used is increased to 500g.

[0037] The raw materials include the following parts by weight: 100g of EPDM raw rubber; 1.3g of sulfur; 1.3g of accelerator MBT-80; 1g of accelerator DPTT-70; 1.1g of accelerator ZDBC-80; 7g of foaming agent OBSH-50; 15g of carbon black N550; 12.5g of paraffin oil; 7g of zinc oxide; 2g of stearic acid; 12g of coupling agent Si69; and 500g of samarium iron nitrogen.

[0038] Comparative Example 2 The difference between this comparative example and Example 2 is that the amount of vulcanization system added in this comparative example is reduced by 25%.

[0039] The raw materials include the following parts by weight: 100g of EPDM raw rubber; 1.6g of sulfur; 1.6g of accelerator MBT-80; 1.3g of accelerator DPTT-70; 1.4g of accelerator ZDBC-80; 7g of foaming agent OBSH-50; 15g of carbon black N550; 12.5g of paraffin oil; 7g of zinc oxide; 2g of stearic acid; 12g of coupling agent Si69; and 400g of samarium iron nitrogen.

[0040] Comparative Example 3 The difference between this comparative example and Example 2 is that the amount of vulcanization system added to this comparative example is increased by 25%.

[0041] The raw materials include the following parts by weight: 100g of EPDM raw rubber; 2.3g of sulfur; 2.3g of accelerator MBT-80; 1.8g of accelerator DPTT-70; 1.9g of accelerator ZDBC-80; 7g of foaming agent OBSH-50; 15g of carbon black N550; 12.5g of paraffin oil; 7g of zinc oxide; 2g of stearic acid; 12g of coupling agent Si69; and 400g of samarium iron nitrogen.

[0042] Comparative Example 4 The difference between this comparative example and Example 3 is that the coupling agent added in this comparative example is replaced with KR-TTS.

[0043] The raw materials include the following parts by weight: 100g of EPDM raw rubber; 2.0g of sulfur; 2.0g of accelerator MBT-80; 1.5g of accelerator DPTT-70; 1.7g of accelerator ZDBC-80; 7g of foaming agent OBSH-50; 15g of carbon black N550; 12.5g of paraffin oil; 7g of zinc oxide; 2g of stearic acid; 12g of coupling agent KR-TTS; and 400g of samarium iron nitrogen.

[0044] Comparative Example 5 The difference between this comparative example and Example 2 is that no coupling agent is added to this comparative example.

[0045] The raw materials include the following parts by weight: 100g of EPDM raw rubber; 2.0g of sulfur; 2.0g of accelerator MBT-80; 1.5g of accelerator DPTT-70; 1.7g of accelerator ZDBC-80; 7g of foaming agent OBSH-50; 15g of carbon black N550; 12.5g of paraffin oil; 7g of zinc oxide; 2g of stearic acid; and 400g of samarium iron nitrogen.

[0046] Comparative Example 6 The difference between this comparative example and Example 5 is that the pre-vulcanization temperature of this comparative example is 110°C and the secondary vulcanization temperature is 160°C.

[0047] The raw materials include the following parts by weight: 100g of EPDM raw rubber; 2.0g of sulfur; 2.0g of accelerator MBT-80; 1.5g of accelerator DPTT-70; 1.7g of accelerator ZDBC-80; 7g of foaming agent OBSH-50; 15g of carbon black N550; 12.5g of paraffin oil; 7g of zinc oxide; 2g of stearic acid; 12g of coupling agent A151; and 400g of samarium iron nitrogen.

[0048] In S1, plasticizing is the first step in rubber processing. Its main purpose is to reduce the initial entanglement between rubber molecular chains and improve its plasticity and processing fluidity. Applying shear force under closed conditions can cause partial breakage and untangling of EPDM rubber molecular chains, making the rubber compound easier to mix with subsequent fillers, oils, etc., thereby improving mixing efficiency and uniformity.

[0049] Pre-treating the surface of samarium iron nitrogen magnetic fillers and coupling agents has a dual effect: firstly, it reduces the tendency of filler particles to agglomerate by forming chemical bonds between the coupling agent molecules on the filler surface; secondly, it improves the interfacial compatibility between the filler and the rubber matrix. Tests showed that the bonding between the pre-treated filler and the rubber matrix was significantly improved, indicating a substantial improvement in the compatibility between the filler and the rubber matrix.

[0050] In S3, the silane coupling agent-modified samarium iron nitrogen magnetic filler is premixed with the remaining paraffin oil and then added to the rubber compound in small, multiple batches to avoid instantaneous concentration that could cause filler agglomeration or poor dispersion. The coupling agent, after modifying the surface of the magnetic powder, significantly improves its interfacial compatibility with the rubber matrix, effectively promoting the uniform dispersion of magnetic particles in the rubber matrix.

[0051] Step S4 employs a pre-vulcanization process to initially establish a cross-linked structure between rubber molecules before the foaming agent decomposes. A 1-minute vulcanization treatment at 120°C and 15 MPa allows the rubber to form a certain degree of spatial network structure. This pre-cross-linked structure effectively limits the impact of the large amount of gas generated by the rapid decomposition of the foaming agent on the rubber matrix during subsequent foaming, thereby preventing material deformation or structural collapse and promoting the uniform formation of the cell structure.

[0052] The foaming and vulcanization process in step S5 is carried out at 170°C for 15–25 minutes, which allows for the complete decomposition of the foaming agent and the simultaneous cross-linking of the three-dimensional network structure of the rubber. This temperature range achieves a synergistic reaction between rubber cross-linking and the thermal decomposition of the foaming agent, ensuring that the cells are effectively supported by the colloidal network during the formation process, inhibiting cell merging and rupture, and resulting in a uniform and dense cell structure in the final product.

[0053] In step S6, a single-sided multi-stage magnetization device is used to magnetize the foamed and vulcanized material. The applied magnetic field strength is 30000 GS, which allows the samarium iron nitrogen particles inside the material to be fully oriented and aligned, thus forming a stable magnetic structure with high remanence. Multi-stage magnetization helps to improve the overall magnetic attraction performance of the material, while the single-sided magnetization design is more suitable for the application scenarios of magnetic seals, making the adsorption surface concentrated and efficient. The magnetized composite material exhibits good magnetic retention, and its adsorption force with metal parts can reach more than 2N.

[0054] The magnetic EPDM foamed rubber composites prepared in Examples 1-5 and Comparative Examples 1-6 were tested.

[0055] The testing method is as follows: Density: According to GB / T 533-2008, prepare two samples with a mass of at least 2.5 g each, and measure the mass m1 of the sample in air and the mass m2 of the sample in water. Density (d) is calculated using the formula.

[0056] ρ is the density of water. The measurement result is the average of two samples, and the measurement result is the density of the sample.

[0057] Expansion ratio: The ratio of the volume of the sample after foaming to the volume before foaming, calculated by the following formula:

[0058] Where: ρ0: bulk density of the sample before foaming, g / cm³ 3 ρ1: Bulk density of the sample after foaming, g / cm³ 3 .

[0059] Hardness: According to GB / T 531.1-2008, the hardness of vulcanized rubber shall be measured using a Shore A hardness tester. The thickness of the sample shall be at least 6 mm, and the thickness of the sample may be composed of 3 layers of vulcanized sample stacked together. The Shore A test position shall be at least 12 mm away from any edge. The standard spring test force shall be held for 3 seconds, and 5 measurements shall be taken at different positions on the sample and the median value shall be taken.

[0060] Tensile strength and elongation at break: According to GB / T 528-2009, dumbbell-shaped Type 1 standard specimens were cut using a cutting tool. Stress-strain tests were performed on the dumbbell-shaped specimens to obtain stress-strain curves and a series of data including tensile strength, elongation at break, and permanent deformation at break. Five specimens were measured, and the median of each performance data point was taken.

[0061] Tear strength: According to GB / T 529-2008, right-angle tear test specimens are cut using a cutting tool, and the tear strength is obtained by testing the right-angle tear test specimens. Five specimens are measured, and the median value is taken as the result.

[0062] Magnetic attraction: such as Figure 1As shown, two rectangular iron sheets are selected. A rectangular area is drawn in the center of the surface of one of the iron sheets as the test position for the rubber sample. During the test, two fixed-length threads are used, one end connected to a weight, and the other end fixed to the two ends of the iron sheet. One of the rectangular iron sheets is fixed horizontally, and the rubber sample to be tested is placed in the center of the iron sheet. The other iron sheet is attached to the underside of the test surface of the rubber sample, and the weight is suspended from the end of the thread. At this time, the total weight borne by the iron sheet and the weight is the measured value of the magnetic attraction force. The magnetic attraction force is calculated by the following formula:

[0063] in, The weight of the iron sheet. Let g be the weight of the weight, and g be the acceleration due to gravity.

[0064] The test results are shown in Tables 1 and 2. In Tables 1 and 2, "-" indicates that no test was conducted.

[0065]

[0066]

[0067] Based on the material performance data of Examples 1-5 in Table 1 and the material performance data of Comparative Examples 1-6 in Table 2, it can be concluded that: The performance comparison analysis between Example 1 and Comparative Example 1 shows that the magnetic attraction force of the material increases with the increase of the amount of samarium iron nitrogen magnetic powder added. In Comparative Example 1, the amount of magnetic powder used was 500 parts, and its magnetic attraction force reached 5.4 N, which is significantly improved compared to Example 1 (400 parts added, magnetic attraction force 3.6 N). However, excessive magnetic filler has an adverse effect on the mechanical properties of the material. Specifically, the tensile strength of Comparative Example 1 is only 0.6 MPa, and the elongation at break is 203%, both significantly lower than the 1.3 MPa and 483% of Example 1, respectively. Simultaneously, the foaming ratio of Comparative Example 1 also decreased to 1.34, far lower than the 1.42 of Example 1. This phenomenon is mainly attributed to the tendency of high-filling-content magnetic powder to agglomerate in the rubber matrix, disrupting the continuous phase structure of the matrix, causing stress concentration, and thus reducing the flexibility and ductility of the composite material. Furthermore, the excessive filling of magnetic powder particles restricts the uniform diffusion of the foaming agent in the rubber matrix and the stable formation of bubbles, leading to a decrease in the foaming ratio. Therefore, considering the overall performance, selecting an appropriate amount of magnetic filler can ensure that the material maintains high magnetic attraction while having good mechanical properties.

[0068] Analysis of the data from Example 2 and Comparative Examples 2 and 3 shows that the tensile strength of the material increases with the increase of the vulcanization system dosage, while the vulcanization speed significantly accelerates. An optimal matching relationship exists between the vulcanization speed and the foaming speed; Example 2 exhibits a good match between the vulcanization speed and the foaming speed, resulting in a higher foaming ratio. As the foaming ratio increases, the density of the magnetic powder per unit material volume decreases accordingly, leading to a slight decrease in magnetic attraction. However, due to the high magnetic properties of the samarium iron nitride magnetic powder, even under high foaming ratio conditions, the magnetic attraction of the material can still maintain a relatively high level of 2.6 N.

[0069] In Examples 2, 3, and Comparative Example 4, coupling agents Si69, A151, and KR-TTS were used, respectively. Comparative performance data analysis shows that silane coupling agents Si69 and A151 both act as bridges between the samarium iron nitrogen (SFI) magnetic powder and the rubber matrix, organically combining SFI with the EPDM rubber matrix. In Example 3, the composite material with added silane coupling agent A151 exhibited higher tensile strength, tear strength, and lower permanent deformation at break, indicating that A151 had a better modification effect on SFI and effectively improved its dispersibility in the rubber matrix. Compared to Example 2, the foaming ratio in Example 3 was slightly reduced because the strong bond between SFI and the rubber matrix constrained cell growth.

[0070] Analysis of Comparative Examples 2, 4 and 5 shows that, compared to Comparative Example 5 which did not add a coupling agent, Examples 2 and 4 both added the coupling agent Si69, resulting in a higher foaming ratio. This is because the coupling agent acts as a small molecule plasticizer in the matrix, reducing the matrix viscosity and facilitating cell formation and growth.

[0071] Analysis comparing Example 5 and Comparative Example 6 reveals that the tensile permanent deformation of Example 5 is lower than that of Comparative Example 6, with Example 5 showing only 8% and Comparative Example 6 showing as high as 15%, indicating a more significant permanent deformation. This suggests that appropriately increasing the secondary vulcanization temperature facilitates a more complete cross-linking reaction between rubber molecules, thereby forming a denser and more stable three-dimensional network structure. This helps to enhance the support force and deformation resistance of the foam cells, indirectly affecting the stability of the foam structure of the material.

[0072] In summary, the samarium iron nitrogen magnetic EPDM foamed rubber composite material prepared by this invention has excellent magnetic attraction and good mechanical properties, and has important application prospects in the field of magnetic sealing.

[0073] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A samarium iron nitrogen magnetic EPDM foamed rubber composite material, characterized in that... The raw materials include the following parts by weight: 100 parts of EPDM raw rubber, 300-600 parts of magnetic filler, 10-20 parts of reinforcing filler, 10-30 parts of paraffin oil, 1-3 parts of sulfur, 3-7 parts of accelerator, 2-3 parts of stearic acid, 5-7 parts of zinc oxide, 3-9 parts of foaming agent, and 3-30 parts of coupling agent, wherein the magnetic filler is samarium iron nitrogen permanent magnet powder, modified with the coupling agent.

2. The magnetic EPDM foamed rubber composite material according to claim 1, characterized in that, The Mooney viscosity (ML(1+8) 150℃) of the EPDM raw rubber is 40-70, the ethylene content is 40-60wt%, and the third monomer (ENB) content is 3-10wt%.

3. The magnetic EPDM foamed rubber composite material according to claim 1, characterized in that, The average particle size of the samarium iron nitrogen permanent magnet powder is 1-10 μm; the mass ratio of the magnetic filler to the coupling agent is 100:1~5.

4. The magnetic EPDM foamed rubber composite material according to claim 1, characterized in that, The reinforcing filler is at least one of carbon black N550 and carbon black N774, and the mass ratio of the magnetic filler to the coupling agent is 100:2~5.

5. The magnetic EPDM foamed rubber composite material according to claim 1, characterized in that, The accelerator is selected from one or more of thiazole accelerators, thiuram accelerators, and dithiocarbamate accelerators.

6. The magnetic EPDM foamed rubber composite material according to claim 1, characterized in that, The foaming agent is selected from at least one of azodicarbonamide, 4,4'-oxobisbenzenesulfonyl hydrazine, and sodium bicarbonate.

7. The magnetic EPDM foamed rubber composite material according to claim 1, characterized in that, The coupling agent is at least one of bis-[γ-(triethoxysilyl)propyl]tetrasulfide (Si69), vinyltriethoxysilane (A151), and isopropyltris(dioctylpyrophosphoryloxy)titanate (KR-TTS).

8. The method for preparing the samarium iron nitrogen magnetic EPDM foamed rubber composite material according to any one of claims 1-7, characterized in that, The preparation method includes: S1 Plasticizing: Raw EPDM rubber is placed in a kneader and kneaded and plasticized under closed conditions. S2 Mixing: Mix half of the paraffin oil with the reinforcing filler evenly, then put it into a kneader and knead it at high temperature under closed conditions. The kneading temperature is 100-130℃ and the time is 3-8 minutes. Then add zinc oxide and stearic acid and continue to knead for 3-8 minutes to obtain a uniform masterbatch. S3 Secondary Mixing: Transfer the masterbatch to an open mixing mill for secondary mixing. Control the roller temperature at 50-80℃. Mix the coupling agent-modified samarium iron nitrogen magnetic filler with the remaining half of the paraffin oil evenly. Then, slowly add the magnetic filler to the masterbatch in 5-10 portions to ensure uniform dispersion. Subsequently, add the foaming agent, vulcanizing agent, and accelerator in sequence and mix for 5-15 minutes until the mixture is uniform and the compound is obtained. S4 Pre-vulcanization: Place the compounded rubber sheet into the mold and vulcanize it in a flat vulcanizing machine at a temperature of 110~140℃, a pressure of 10~15MPa, and a time of 1~6 minutes. S5 Two-Stage Foaming Vulcanization: The pre-vulcanized film is transferred to a larger mold for foaming vulcanization at a temperature of 160~190℃ for 1~25 minutes. S6 Magnetization: Magnetize the vulcanized foamed rubber to obtain a samarium iron nitrogen magnetic EPDM foamed rubber composite material.

9. The preparation method according to claim 8, characterized in that, The coupling agent-modified samarium iron nitrogen magnetic filler was prepared by the following method: the coupling agent and anhydrous ethanol were mixed and hydrolyzed for 30 min, the magnetic filler was poured into the mixture, mechanically stirred at room temperature for 2 h, and dried at 40~70℃ for 12 h to obtain the coupling agent-modified samarium iron nitrogen magnetic filler; the magnetization was carried out using a single-sided multi-stage magnetization device with a magnetic field strength of 30000GS.

10. The application of the samarium iron nitrogen magnetic EPDM foamed rubber composite material according to any one of claims 1 to 7 in the field of magnetic sealing.

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