Three-section vulcanization process for rubber composite material

Abstract

The invention provides a three-stage vulcanization process for a rubber composite material, and belongs to the technical field of rubber vulcanization. According to the three-section vulcanization process provided by the invention, the temperature and pressure are controlled in stages, so that the anisotropic filler is uniformly dispersed in the rubber blank, a directional magnetic field is applied in the pre-vulcanization and main vulcanization stages, the proper strength and direction of the magnetic field are regulated and controlled, the filler is directionally arranged, and the creep resistance and fatigue resistance of the rubber material are strengthened.

Description

Technical Field

[0001] This application belongs to the field of rubber vulcanization technology, and in particular relates to a three-stage vulcanization process for rubber composite materials. Background Technology

[0002] Rubber materials, due to their unique high elasticity and damping properties, are widely used in industrial fields such as vibration damping, sealing, and tires. High-performance equipment, especially in aerospace, precision instruments, and high-end automobiles, places extremely high demands on the mechanical properties, dynamic fatigue durability, and stability of rubber vibration damping components under different environments.

[0003] To improve the overall performance of rubber materials, traditional methods mainly rely on adding various reinforcing fillers, such as carbon black and silica, to the rubber matrix. In recent years, nanofillers, such as graphene and carbon nanotubes (CNTs), have been considered ideal reinforcements for preparing next-generation high-performance rubber composites due to their superior mechanical, electrical, and thermal properties. However, these nanofillers are prone to agglomeration in the rubber matrix, making uniform dispersion difficult and severely limiting their reinforcing effect. Furthermore, the weak interfacial bonding between the filler and the rubber molecular chains often becomes a weak point for stress concentration, leading to premature material failure under dynamic loads.

[0004] Vulcanization is a key process in rubber product manufacturing, determining the cross-linked network structure of rubber molecular chains and ultimately affecting the physical and mechanical properties of the product. Current vulcanization processes typically employ one-stage or two-stage isothermal and isobaric vulcanization methods. While this process is sufficient for producing conventional rubber products, it reveals significant limitations when handling complex systems containing high-performance nanofillers: traditional vulcanization processes cannot effectively control the orientation of nanofillers, resulting in their disordered distribution within the matrix and the inability to form an effective reinforcing network. Consequently, the superior directional properties of anisotropic fillers (such as graphene and carbon nanotubes) cannot be fully utilized. Furthermore, one-stage vulcanization makes it difficult to precisely control the cross-linking reaction rate, easily generating significant internal stress within the material. This internal stress can lead to deformation and cracking during later use, significantly reducing the product's dynamic fatigue life.

[0005] Therefore, the present invention provides a three-stage vulcanization process for rubber composites, which effectively promotes the uniform dispersion and directional arrangement of nanofillers in the rubber matrix, strengthens the interfacial bonding between the filler and the matrix, and optimizes the crosslinking network structure to eliminate internal stress, thereby preparing a rubber composite material with small creep and excellent dynamic durability. Summary of the Invention

[0006] To address the technical problems existing in the prior art, the primary objective of this invention is to provide a three-stage vulcanization process for rubber composite materials that reduces creep and enhances dynamic durability.

[0007] Another object of the present invention is to provide a rubber composite material made by the above-mentioned three-stage vulcanization process.

[0008] Another object of the present invention is to provide a shock-absorbing article made of the above-mentioned rubber composite material.

[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: This invention protects a three-stage vulcanization process for rubber composites, comprising the following steps: placing a rubber blank containing anisotropic fillers in a vulcanization device and sequentially performing the following three stages of hot-press vulcanization treatment. Pre-vulcanization: Vulcanization is carried out at 150~165℃ and 3~8MPa, while an external magnetic field is applied; Main vulcanization: Vulcanization is carried out at 165~180℃ and 8~15 MPa, while an external magnetic field is applied; Post-curing: Curing is carried out at 170~190℃ and 3~8 MPa; The magnetic field strength of the external magnetic field is 0.6~5T, and the strength and direction of the two external magnetic fields are the same. The angle α between the direction of the external magnetic field and the direction of the main load on the rubber is less than 22.5°.

[0010] The three-stage vulcanization process controls temperature and pressure in stages to ensure uniform dispersion of anisotropic fillers in the rubber matrix, forming a strong interfacial bond between the fillers and rubber molecular chains. This improves the material's durability and fatigue resistance. The post-vulcanization stage eliminates internal stress, preventing deformation or cracking during use. Combined with magnetic field orientation technology, the anisotropic fillers align along specific directions to form a reinforcing network, significantly improving the material's mechanical and dynamic properties.

[0011] The direction of the main load on the rubber is the direction corresponding to the maximum force that the automotive engineering components (such as shock absorbers, gaskets, automotive suspensions, springs, tires, anti-torsion tie rods, etc.) made of the aforementioned rubber composite material need to withstand during operation.

[0012] When rubber composite materials are made into shock-absorbing pads or sealing pads, the direction of the main load on the rubber is perpendicular to the direction of the largest cross-section of the shock-absorbing pad or sealing pad.

[0013] When rubber composite materials are used to make car suspensions, the direction of the main load on the rubber is perpendicular to the ground.

[0014] When rubber composite materials are made into anti-torsion tie rods, the direction of the main load on the rubber is the direction of the car's forward braking.

[0015] When rubber composites are made into springs, the main load directions of the rubber are the compression and tension directions.

[0016] When rubber composite materials are used to make tires, the direction of the main load on the rubber is perpendicular to the ground.

[0017] The purpose of applying a magnetic field in this invention is to make the anisotropic filler parallel to the main load direction or form a small angle of less than 22.5° with the main load direction, so as to enhance the creep resistance and fatigue resistance of automotive engineering parts made of rubber composite materials when subjected to the corresponding main load direction.

[0018] Magnetic fields can orient non-magnetic fillers such as graphene and carbon nanotubes within rubber. The core principle is based on the synergistic effect of induced magnetic anisotropy and magnetic torque. Although these fillers are not magnetic themselves, their one-dimensional or two-dimensional geometry (such as rods or sheets) induces a weak magnetic moment in an applied magnetic field, forming a "preferred direction" with the lowest energy (e.g., the long axis parallel to the magnetic field). Subsequently, the magnetic torque generated by the magnetic field drives the filler to rotate until its preferred direction is perfectly aligned with the magnetic field direction. This ordered arrangement is permanently fixed when the rubber matrix cures during the orienting process. By controlling the direction of the magnetic field, the mechanical or functional properties of composite materials in specific dimensions can be enhanced. Therefore, setting the external magnetic field direction to have an angle α less than 22.5° with the main load direction of the rubber can enhance the creep resistance and fatigue resistance of the rubber material in the load direction.

[0019] Preferably, the direction of the main load on the rubber is perpendicular to the ground.

[0020] Preferably, the magnetic field strength of the external magnetic field is 1~3T.

[0021] Preferably, the rubber matrix of the rubber composite material is ethylene propylene diene monomer (EPDM) rubber.

[0022] Preferably, the angle α between the direction of the external magnetic field and the direction of the rubber main load is 90°.

[0023] Preferably, the pre-vulcanization time is 3-8 minutes, the main vulcanization time is 8-15 minutes, and the post-vulcanization time is 3-8 minutes.

[0024] Preferably, the anisotropic filler includes at least one of carbon nanotubes, graphene, and boron nitride nanosheets.

[0025] Preferably, the vulcanizing device is an electric heating-oil pressure flat vulcanizing machine.

[0026] This invention also protects a rubber composite material made by the above-described three-stage vulcanization process.

[0027] The present invention also protects an automotive shock absorber made from the above-mentioned rubber composite material.

[0028] Preferably, the automotive shock absorber includes one or more of the following: shock absorber pads, sealing gaskets, automotive suspension components, springs, tires, and anti-torsion tie rods.

[0029] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a three-stage vulcanization process for rubber composites. By controlling temperature and pressure in stages, anisotropic fillers are ensured to be uniformly dispersed in the rubber blank. A directional magnetic field is applied in the pre-vulcanization and main vulcanization stages, and the strength and direction of the magnetic field are adjusted to make the fillers oriented, thereby enhancing the creep resistance and fatigue resistance of the rubber material. Attached Figure Description

[0030] Figure 1 This is a schematic diagram showing the angle α between the direction of the external magnetic field and the direction of the main load on the rubber being 0°.

[0031] Figure 2 The diagram shows the angle α between the direction of the external magnetic field and the direction of the main load on the rubber, which is 22.5°.

[0032] Figure 3 The diagram shows the angle α between the direction of the external magnetic field and the direction of the main load on the rubber, which is 45°.

[0033] Figure 4 The diagram shows the angle α between the direction of the external magnetic field and the direction of the main load on the rubber, which is 67.5°.

[0034] Figure 5 This is a schematic diagram showing the angle α between the direction of the external magnetic field and the direction of the main load on the rubber, which is 90°. Detailed Implementation

[0035] The present invention is further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.

[0036] I. The reagents used in the various embodiments and comparative examples of this invention are described below: Rubber composite material #1: EPDM rubber, with anisotropic filler of carbon nanotubes; Table 1 Component 1 of Rubber Composite Material

[0037] Preparation method: In an internal mixer at 80℃, first add rubber and plasticizer, premix for 30s; add filler, activator and flame retardant from Table 1, mix for 8min; finally add DCP and sulfur, mix for another 2min, for a total mixing time of 12min; the sheet thickness is 2mm, cool to room temperature, and cut into φ100mm round blanks; cool naturally to ≤40℃, and remove flash.

[0038] Rubber composite material #2: EPDM rubber, with graphene as the anisotropic filler; Table 2 Component #2 of Rubber Composite Material

[0039] The preparation method is the same as that for rubber composite material 1#.

[0040] Rubber composite material #3: EPDM rubber, with boron nitride nanosheets as the anisotropic filler; Table 3 Component 3 of Rubber Composite Material

[0041] The preparation method is the same as that for rubber composite material 1#.

[0042] II. Experimental Scheme Example 1 Rubber main load direction: The mold positioning pin determines the load direction of the rubber part. The rubber part prepared in Example 1 is an automobile suspension, and the rubber main load direction is perpendicular to the ground. The rubber composite material No. 1 blank is melted and mixed, then added to a flat vulcanizing machine for the following vulcanization steps: Pre-vulcanization: Vulcanization is carried out at 160℃ and 5MPa for 5 minutes, while an external magnetic field of 1T is applied. The angle α between the direction of the external magnetic field and the direction of the main load on the rubber is 0°, that is, the direction of the external magnetic field is parallel to the direction of the main load on the rubber. Main vulcanization: Vulcanization is carried out at 170℃ and 10 MPa for 10 minutes, and an external magnetic field of 1T is applied. The angle α between the direction of the external magnetic field and the direction of the main load on the rubber is 0°, that is, the direction of the external magnetic field is parallel to the direction of the main load on the rubber. Post-curing: Curing is carried out at 180℃ and 5MPa for 5 minutes without an external magnetic field.

[0043] Table 4 Comparison of parameters in Examples 1-6

[0044] Table 5 Comparison of parameters in Examples 7-14

[0045] Example 15 The experimental method is the same as in Example 1, except that the angle α between the direction of the external magnetic field applied during the pre-curing and main curing stages and the direction of the main load on the rubber is 22.5°. Figure 2 As shown.

[0046] Table 6 Comparison of parameters in Comparative Examples 1-8

[0047] Comparative Example 9 The experimental method is the same as in Example 1, except that the angle α between the direction of the external magnetic field applied during the pre-vulcanization and main vulcanization stages and the direction of the main load on the rubber is 45°. Figure 3 As shown.

[0048] Comparative Example 10 The experimental method is the same as in Example 1, except that the angle α between the direction of the external magnetic field applied during the pre-vulcanization and main vulcanization stages and the direction of the main load on the rubber is less than 67.5°. Figure 4 As shown.

[0049] Comparative Example 11 The experimental method is the same as in Example 1, except that the angle α between the direction of the external magnetic field applied during the pre-curing and main curing stages and the direction of the main rubber load is 90°, that is, the direction of the external magnetic field is perpendicular to the direction of the main rubber load. Figure 5 As shown.

[0050] III. Test Indicators (1) Creep: 150℃×200h compression permanent deformation, test standard GB / T 7759.1-2015, equipment: high temperature creep chamber (Instron 3119-407), the creep qualification standard is below 7%; (2) Fatigue life: Fatigue life of 90℃ test bench × 10 4 The test standard was GB / T 4337-2015, and the equipment was an electro-hydraulic servo fatigue tester (MTS 810). The fatigue life qualification standard was 3.5 × 10⁻⁶. 4 More than once.

[0051] IV. Test Results Table 7 Test Results of Examples / Comparative Examples

[0052] Examples 1-15 provide a series of vulcanized rubber materials that simultaneously meet the requirements for creep and fatigue life.

[0053] Comparative Example 1 had no post-curing stage, only pre-curing and main curing. The post-curing stage plays an important role in eliminating internal stress and stabilizing the cross-linked structure. The absence of post-curing led to a significant decrease in creep and fatigue performance. In Comparative Example 2, no magnetic field was applied during pre-curing, resulting in ineffective directional alignment of the filler, weak interfacial bonding, and decreased performance; both creep and fatigue performance were unsatisfactory. In Comparative Example 3, no magnetic field was applied during main curing; without a magnetic field in the main curing stage, the filler failed to undergo further orientation under high temperature and pressure, resulting in unsatisfactory creep and fatigue performance. The magnetic field strength of Comparative Example 4 was... 0.5T: Insufficient magnetic field strength, weak filler orientation, decreased creep and fatigue performance, unqualified; Comparative Example 5: Post-vulcanization temperature 160℃, too low, insufficient internal stress relief, high creep, reduced fatigue performance; Comparative Example 6: Post-vulcanization temperature 200℃, high temperature may accelerate aging, although creep is low, fatigue life is only slightly above the qualified line; Comparative Example 7: Post-vulcanization pressure 2MPa, too low pressure, insufficient structure compaction, residual internal stress, both creep and fatigue performance unqualified; Comparative Example 8: Post-vulcanization pressure 10... MPa, excessive pressure may introduce new stress, resulting in unqualified fatigue life; Comparative Example 9 has an angle α of 45° between the direction of the external magnetic field and the direction of the main rubber load; Comparative Example 10 has an angle α of 67.5° between the direction of the external magnetic field and the direction of the main rubber load; Comparative Example 11 has an angle α of 90° between the direction of the external magnetic field and the direction of the main rubber load. Comparative Examples 9 to 11 show that if the angle between the direction of the external magnetic field and the direction of the main rubber load exceeds 22.5°, the effect of the filler on the creep resistance and fatigue resistance of the rubber load will be greatly reduced.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A three-stage vulcanization process for rubber composite materials, characterized in that, Includes the following steps: The rubber blank containing anisotropic filler is placed in a vulcanization device and subjected to the following three stages of hot-press vulcanization treatment in sequence. Pre-vulcanization: Vulcanization is carried out at 150~165℃ and 3~8MPa, while an external magnetic field is applied; Main vulcanization: Vulcanization is carried out at 165~180℃ and 8~15 MPa, while an external magnetic field is applied; Post-curing: Curing is carried out at 170~190℃ and 3~8 MPa; The magnetic field strength of the external magnetic field is 0.6~5T, and the strength and direction of the external magnetic field are the same in both applications. The angle α between the direction of the external magnetic field and the direction of the main load on the rubber is less than 22.5°.

2. The three-stage vulcanization process according to claim 1, characterized in that, The magnetic field strength of the external magnetic field is 1~3T.

3. The three-stage vulcanization process according to claim 1, characterized in that, The rubber matrix of the rubber composite material is ethylene propylene diene monomer (EPDM) rubber.

4. The three-stage vulcanization process according to claim 1, characterized in that, The angle α between the direction of the external magnetic field and the direction of the rubber main load is 90°.

5. The three-stage vulcanization process according to claim 1, characterized in that, The pre-vulcanization time is 3-8 minutes, the main vulcanization time is 8-15 minutes, and the post-vulcanization time is 3-8 minutes.

6. The three-stage vulcanization process according to claim 1, characterized in that, The anisotropic filler includes at least one of carbon nanotubes, graphene, and boron nitride nanosheets.

7. The three-stage vulcanization process according to claim 1, characterized in that, The vulcanizing device is an electric heating-oil pressure flat vulcanizing machine.

8. A rubber composite material, characterized in that, It is produced by the three-stage vulcanization process described in any one of claims 1 to 7.

9. A type of automotive shock absorber, characterized in that, It is prepared from the rubber composite material described in claim 8.

10. The automotive shock absorber according to claim 9, characterized in that, This includes one or more of the following: shock absorbers, gaskets, automotive mounts, springs, tires, and anti-torsion rods.

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