A high-toughness and high-strength rubber composite material and its preparation method

Abstract

This invention discloses a high-toughness, high-strength rubber composite material and its preparation method. The material is prepared by hot-pressing and vulcanizing a rubber matrix, a dithiol-containing imidazolium aprotic ionic liquid, silica, a silane coupling agent, stearic acid, zinc oxide, a vulcanizing agent, an accelerator, and paraffin wax, all mixed uniformly. The dithiol-containing imidazolium aprotic ionic liquid in this invention is grafted onto the rubber side chains via click chemistry to increase the crosslinking density of the rubber composite material. Under external force, it can improve the toughness of the rubber composite material. During the rubber vulcanization process, it can shorten the vulcanization time and improve the interaction between the organic and inorganic interfaces. Furthermore, it can improve the dispersion of silica in the rubber matrix. The resulting high-toughness, high-strength rubber composite material exhibits excellent mechanical properties and fatigue resistance, has a wide range of applications, and can be industrially produced.

Description

Technical Field

[0001] This invention belongs to the field of rubber composite material technology, specifically relating to a high-toughness, high-strength rubber composite material and its preparation method. Background Technology

[0002] Since the discovery in 1893 that sulfur could vulcanize and crosslink rubber to form a stable material, vulcanized rubber has been widely used in production and daily life, such as in rubber tires, seals, damping systems, soft robots, wearable electronic devices, and flexible sensors. However, while the three-dimensional network system formed by vulcanization improves the mechanical strength of rubber to some extent, it still cannot meet the requirements of most engineering rubber products, and over-vulcanization can lead to a significant decrease in rubber toughness. Therefore, in industry, rubber properties are usually enhanced by compounding it with nanofillers such as carbon black, silica, and clay.

[0003] Silica is an inorganic nanomaterial with excellent rigidity, stability, and flame retardancy. When added to rubber materials, it can significantly enhance their mechanical properties, thermal stability, and resistance to acid and alkali corrosion. Typically, silica is used in combination with silane coupling agents to improve its dispersion compatibility in rubber, thereby improving the mechanical properties of rubber products. This has been documented in numerous reports and has demonstrated significant application value in production practice. However, with the rapid development of modern industry, higher demands are being placed on the performance of rubber composite materials. Currently, there are three aspects of the rubber / silica / silane coupling agent system that need optimization and improvement:

[0004] 1. Long vulcanization time: Long-term high-temperature vulcanization not only consumes a lot of energy resources, but may also trigger oxidative degradation or structural reactions, which can reduce the strength of rubber or cause it to lose its elasticity.

[0005] 2. Poor toughness: Toughness and strength are usually contradictory in materials. Although the introduction of rigid inorganic nanoparticles can significantly enhance the mechanical strength of rubber composites, it will sacrifice the excellent elasticity of rubber itself.

[0006] 3. Stability needs to be improved: Although the combination of silica and silane coupling agent significantly improves the mechanical properties of rubber composites, under long-term external force, the mechanical properties and stability of rubber composites mainly depend on the magnitude of the interfacial interaction force between rubber and filler.

[0007] Therefore, in order to optimize the existing problems in the rubber / fumed silica / silane coupling agent system and further improve the mechanical properties and stability of rubber composites, it is urgent to develop high-toughness and high-strength rubber composites. Summary of the Invention

[0008] The purpose of this invention is to overcome the defects of the prior art and provide a high-toughness and high-strength rubber composite material.

[0009] Another object of the present invention is to provide a method for preparing the above-mentioned high-toughness and high-strength rubber composite material.

[0010] The technical solution of the present invention is as follows:

[0011] A high-toughness, high-strength rubber composite material is prepared by hot-pressing and vulcanizing a uniformly mixed rubber matrix, a dithiol-containing imidazolium aprotic ionic liquid, silica, a silane coupling agent, stearic acid, zinc oxide, a vulcanizing agent, an accelerator, and paraffin wax. The structural formula of the dithiol-containing imidazolium aprotic ionic liquid is as follows:

[0012]

[0013] R1 is selected from sulfonate anion motifs and carboxylate anion motifs, with the following structures: n = 1 - 11,

[0014] R2 is a C1–12 aliphatic alkane chain or alkoxy chain.

[0015] R3 is a C1-12 aliphatic alkane chain or alkoxy chain.

[0016] In a preferred embodiment of the present invention, the rubber matrix is ​​selected from natural rubber, styrene-butadiene rubber, epoxy rubber and silicone rubber.

[0017] In a preferred embodiment of the present invention, the method for preparing a dithiol-containing diimidazole aprotic ionic liquid includes the following steps:

[0018] a. Alkylation reaction, the reaction route is as follows:

[0019]

[0020] b. The two-step anion exchange reaction has the following reaction route:

[0021]

[0022] In a preferred embodiment of the present invention, the silane coupling agent is selected from mercapto silane coupling agents and vinyl silane coupling agents.

[0023] In a preferred embodiment of the present invention, the silane coupling agent is bis-[γ-(triethoxysilane)propyl]tetrasulfide.

[0024] In a preferred embodiment of the invention, the vulcanizing agent is sulfur.

[0025] In a preferred embodiment of the present invention, the accelerator is N-cyclohexyl-2-benzothiazole sulfenamide.

[0026] In a preferred embodiment of the present invention, the rubber substrate is natural rubber or styrene-butadiene rubber, the silane coupling agent is bis-[γ-(triethoxysilyl)propyl]tetrasulfide, the vulcanizing agent is sulfur, the accelerator is N-cyclohexyl-2-benzothiazole sulfenamide, and the structural formula of the dithiol-containing imidazolium aprotic ionic liquid is as follows:

[0027]

[0028] In a preferred embodiment of the present invention, the mass ratio of the rubber matrix, the dithiol-containing imidazolium aprotic ionic liquid, silica, silane coupling agent, stearic acid, zinc oxide, vulcanizing agent, accelerator and paraffin is 60-100:1-20:10-80:1-20:1-3:2-4:1-4:1-3:1-3.

[0029] The preparation method of the above-mentioned high-toughness and high-strength rubber composite material includes: mixing the rubber matrix, a dithiol-containing imidazolium aprotic ionic liquid, silica, silane coupling agent, stearic acid, zinc oxide, vulcanizing agent, accelerator and paraffin wax in an internal mixer for 7-9 minutes, then extruding the mixture through an open mill to obtain a rubber prepolymer, determining the positive vulcanization time to be 5-20 minutes using a rotorless vulcanizing apparatus, and hot pressing the mixture at 14-16 MPa pressure and 145-155℃ for 5-20 minutes using a flatbed hot press to obtain the high-toughness and high-strength rubber composite material.

[0030] The beneficial effects of this invention are:

[0031] 1. The dithiol-containing imidazolium aprotic ionic liquid of the present invention can undergo a thiol-double bond click chemical reaction with the unsaturated double bonds in rubber. Since an ionic liquid molecule contains two thiol groups, it can covalently crosslink different rubber molecular chains, thereby increasing the crosslinking density of the rubber composite material and thus improving its mechanical strength.

[0032] 2. In this invention, ionic bonds are formed between the anions and cations in the dithiol-containing imidazolium aprotic ionic liquid. These ionic bonds are characterized by strong forces and no directionality. Under the action of external forces, these ionic bonds can dynamically and efficiently dissociate and associate, producing an energy dissipation effect, thereby improving the toughness of the rubber composite material.

[0033] 3. The dithiol-containing imidazolium aprotic ionic liquid of the present invention can catalyze the silanization reaction between silane coupling agent and silica under high temperature conditions, effectively shortening the vulcanization time. At the same time, it can also improve the problem of silica agglomeration in rubber matrix due to thermodynamic incompatibility, realize the uniform dispersion of silica at the nanoscale in rubber matrix, significantly enhance the interaction between organic and inorganic components, and thus improve the mechanical strength and stability of rubber composite material during use.

[0034] 4. The dithiol-containing imidazolium aprotic ionic liquid in this invention is fixed on the rubber side chain by covalent grafting, which has excellent stability and durability, and effectively avoids the occurrence of phenomena such as migration or volatilization of ionic liquid from rubber under conditions such as high temperature, liquid environment, and low pressure.

[0035] 5. The dithiol-containing bisimidazole aprotic ionic liquid in this invention has hydrogen bonds and ion-dipole interactions with silica, which can further improve the dispersibility and compatibility of silica in the rubber matrix, thereby enabling the rubber composite material to obtain excellent mechanical properties.

[0036] 5. The rubber composite material of the present invention has obvious modification effect, its preparation process is simple, the preparation conditions are mild, the cost is low, and it has good potential for industrial production. Attached Figure Description

[0037] Figure 1 The ionic liquid Br-IL in Example 1 of this invention 1 H NMR spectrum.

[0038] Figure 2 The dithiol-containing imidazolium aprotic ionic liquid in Example 1 of this invention 1 H NMR spectrum.

[0039] Figure 3 This is an optical photograph of the high-toughness, high-strength rubber composite material in Example 1 of the present invention.

[0040] Figure 4 The ionic liquid Br-IL in Example 2 of this invention 1 H NMR spectrum.

[0041] Figure 5 The dithiol-containing imidazolium aprotic ionic liquid in Example 2 of this invention 1 H NMR spectrum.

[0042] Figure 6 These are cross-sectional SEM images of the high-toughness, high-strength rubber composite material in Example 1 of the present invention and the comparative rubber composite material in Comparative Example 1. Detailed Implementation

[0043] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0044] Example 1

[0045] a. Alkylation reaction:

[0046] 1.43 g (13.2 mmol) of bromoethane and 1 g (5.3 mmol) of diimidazole butane were dissolved in 15 mL of acetonitrile. The mixture was stirred at 80 °C for 24 h under a nitrogen atmosphere. After removing the solvent by rotary evaporation, 10 mL of anhydrous diethyl ether was added, and the mixture was washed by shaking. After filtration and drying, the intermediate ionic liquid Br-IL was obtained, with the following structural formula:

[0047]

[0048] Its physical property characterization data are as follows: 1 ¹H NMR (500MHz, DMSO-d⁶) δ = 9.34 (d, J = 1.7Hz, 2H, CH), 7.84 (dt, J = 6.4, 1.9Hz, 4H, CH), 4.28–4.18 (m, 8H, CH₂), 1.81 (quint, J = 3.3Hz, 4H, CH₂), 1.43 (t, J = 7.3Hz, 6H, CH₃). This indicates the product is an ionic liquid, Br-IL. 1 H NMR spectrum as shown Figure 1 As shown;

[0049] b. Two-step anion exchange reaction:

[0050] The Br-IL (1 g, 2.5 mmol) obtained in step a was dissolved in 5 mL of ethanol. Potassium hydroxide (0.28 g, 5 mmol) was dissolved in 300 μL of deionized water. After mixing the two solutions, a large amount of white precipitate KBr was produced. The mixture was filtered, and the filtrate was collected to obtain the intermediate ionic liquid OH-IL. 3-Mercaptopropionic acid (0.52 g, 5 mmol) was dissolved in 1 mL of ethanol and slowly added dropwise to OH-IL. After shaking for 1 min, the ethanol was removed by rotary evaporation, and the mixture was freeze-dried for 12 h to remove water, yielding the target product, a diimidazolium aprotic ionic liquid containing a dithiol group. Its structural formula is as follows:

[0051]

[0052] Its characterization data are as follows: 1¹H NMR (500MHz, DMSO-d⁶) δ=9.66(s,2H,CH),7.83(dt,J=6.8,1.9Hz,4H,CH),4.26(t,J=6.2Hz,4H,CH₂),4.21(q,J=7.3Hz,4H,CH₂),2.53(t,J=7.0Hz,4H,CH₂),2.20(t,J=7.0Hz,4H,CH₂),1.80(quint,J=6.4Hz,4H,CH₂),1.43(t,J=7.3Hz,6H,CH₃). This indicates that the product is a diimidazolium aprotic ionic liquid containing a dithiol group. 1 H NMR spectrum as shown Figure 2 As shown.

[0053] By weight, 100 parts of natural rubber, 6 parts of the above-mentioned dithiol-containing imidazolium aprotic ionic liquid, 60 parts of silica, 6 parts of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 2 parts of stearic acid, 3 parts of zinc oxide, 2.5 parts of sulfur, 1 part of N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin wax were mixed in an internal mixer for 8 minutes, and then sheeted out through a two-roll mill to obtain a rubber prepolymer. The optimal vulcanization time was determined to be 9.3 minutes using a rotorless vulcanizing apparatus. The prepolymer was then hot-pressed at 15 MPa and 150°C for 9.3 minutes using a flatbed hot press to obtain the desired product. Figure 3 The high-toughness, high-strength rubber composite material shown.

[0054] Example 2

[0055] The difference between this embodiment and Example 1 lies in the chemical structural formula of the prepared dithiol-containing imidazolium aprotic ionic liquid. This embodiment is detailed below:

[0056] a. Alkylation reaction:

[0057] 1-Bromododecane (3.27 g, 13.1 mmol) and diimidazole butane (1 g, 5.3 mmol) were dissolved in 15 mL of acetonitrile. The mixture was stirred at 80 °C for 24 h under a nitrogen atmosphere. After removing the solvent using a rotary evaporator, 10 mL of anhydrous diethyl ether was added, followed by shaking and washing. The mixture was then filtered and dried to obtain the intermediate ionic liquid Br-IL, whose structural formula is as follows:

[0058]

[0059] Its physical property characterization data are as follows: 1¹H NMR (500MHz, DMSO-d⁶) δ = 9.38 (d, J = 1.7Hz, 2H, CH), 7.85 (dt, J = 7.4, 2.0Hz, 4H, CH), 4.26 (d, J = 6.2Hz, 4H, CH₂), 4.18 (t, J = 7.2Hz, 4H, CH₂), 1.80 (m, 8H, CH₂), 1.24 (s, 36H, CH₂), 0.86 (t, J = 6.8Hz, 6H, CH₃). This indicates the product is an ionic liquid, Br-IL. 1 HNMR spectrum as follows Figure 4 As shown;

[0060] b. Two-step anion exchange reaction:

[0061] The Br-IL (1 g, 1.45 mmol) obtained in step a was dissolved in 5 mL of ethanol. Potassium hydroxide (0.16 g, 2.9 mmol) was dissolved in 150 μL of deionized water. The two solutions were mixed, producing a large amount of white precipitate KBr. The mixture was filtered, and the filtrate was collected to obtain the intermediate ionic liquid OH-IL. 3-Mercaptopropionic acid (0.31 g, 2.9 mmol) was dissolved in 1 mL of ethanol and slowly added dropwise to OH-IL. After shaking for 1 min, the ethanol was removed by rotary evaporation, and the mixture was freeze-dried for 12 h to remove water, yielding the target product, a diimidazolium aprotic ionic liquid containing a dithiol group. Its structural formula is as follows:

[0062]

[0063] Its characterization data are as follows: 1 ¹H NMR (500MHz, DMSO-d⁶) δ=9.80(s,2H,CH),7.84(dt,J=21.7,1.8Hz,4H,CH),4.28(d,J=6.4Hz,4H,CH₂),4.17(t,J=7.2Hz,4H,CH₂),2.55(t,J=7.0Hz,4H,CH₂),2.26(t,J=7.0Hz,4H,CH₂),1.80(m,8H,CH₂),1.23(s,36H,CH₂),0.85(t,J=6.9Hz,6H,CH₃). This indicates that the product is a diimidazolium aprotic ionic liquid containing a dithiol group. 1 H NMR spectrum as shown Figure 5 As shown.

[0064] By weight, 100 parts of natural rubber, 6 parts of dithiol-containing imidazolium aprotic ionic liquid, 60 parts of silica, 6 parts of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 2 parts of stearic acid, 3 parts of zinc oxide, 2.5 parts of sulfur, 1 part of N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin are mixed in an internal mixer for 8 minutes, and then sheeted out through an open mill to obtain the rubber prepolymer.

[0065] The remaining steps are the same as in Example 1, to obtain the high-toughness and high-strength rubber composite material.

[0066] Example 3

[0067] The difference between this embodiment and Example 1 is that the chemical structural formula of the prepared dithiol-containing imidazolium aprotic ionic liquid is different, while the alkylation reaction in step a is exactly the same. This embodiment is detailed below:

[0068] The Br-IL (1 g, 2.5 mmol) obtained in step a was dissolved in 5 mL of ethanol; sodium 3-mercapto-1-propanesulfonate (0.90 g, 5 mmol) was dissolved in 300 μL of deionized water and slowly added dropwise to the Br-IL. After shaking for 1 min, the two were mixed to produce a large amount of white precipitate NaBr. The filtrate was filtered and collected. Ethanol was removed by rotary evaporation, and water was removed by freeze-drying for 12 h to obtain the target product, a dithiol-containing imidazolium aprotic ionic liquid, with the following structural formula:

[0069]

[0070] By weight, 100 parts of natural rubber, 6 parts of dithiol-containing imidazolium aprotic ionic liquid, 60 parts of silica, 6 parts of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 2 parts of stearic acid, 3 parts of zinc oxide, 2.5 parts of sulfur, 1 part of N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin are mixed in an internal mixer for 8 minutes, and then sheeted out through an open mill to obtain the rubber prepolymer.

[0071] The remaining steps are the same as in Example 1, to obtain the high-toughness and high-strength rubber composite material.

[0072] Example 4

[0073] The difference between this embodiment and Example 1 is that natural rubber is replaced with styrene-butadiene rubber. By weight, 100 parts of styrene-butadiene rubber, 6 parts of a dithiol-containing imidazolium aprotic ionic liquid, 60 parts of silica, 6 parts of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 2 parts of stearic acid, 3 parts of zinc oxide, 2.5 parts of sulfur, 1 part of N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin wax are mixed in an internal mixer for 8 minutes, and then sheeted out through a two-roll mill to obtain the rubber prepolymer.

[0074] The remaining steps are the same as in Example 1, to obtain the high-toughness and high-strength rubber composite material.

[0075] Comparative Example 1

[0076] The difference between this comparative example and Example 1 is that no diimidazolium aprotic ionic liquid containing dithiol is added. By weight, 100 parts natural rubber, 60 parts silica, 6 parts bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 2 parts stearic acid, 3 parts zinc oxide, 2.5 parts sulfur, 1 part N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part paraffin wax were mixed in an internal mixer for 8 minutes, and then sheeted out through a two-roll mill to obtain the rubber prepolymer.

[0077] The remaining steps are the same as in Example 1, and a comparative rubber composite material is obtained.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 1 is that the ionic liquid is an amino-containing diimidazole aprotic ionic liquid. Specifically, Br-IL (1 g, 1.45 mmol) was dissolved in 5 mL of ethanol, and potassium hydroxide (0.16 g, 2.9 mmol) was dissolved in 150 μL of deionized water. After mixing the two, a large amount of white precipitate KBr was produced. The mixture was filtered and the filtrate was collected to obtain the intermediate ionic liquid OH-IL. 3-aminopropionic acid (0.26 g, 2.9 mmol) was dissolved in 1 mL of ethanol and slowly added dropwise to OH-IL. After shaking for 1 min, the ethanol was removed by rotary evaporation, and the mixture was freeze-dried for 12 h to remove water, yielding the target product, an amino-containing diimidazole aprotic ionic liquid, with the following structural formula:

[0080]

[0081] By weight, 100 parts of natural rubber, 6 parts of diamino-containing imidazolium aprotic ionic liquid, 60 parts of silica, 6 parts of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 2 parts of stearic acid, 3 parts of zinc oxide, 2.5 parts of sulfur, 1 part of N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin are mixed in an internal mixer for 8 minutes, and then sheeted out through an open mill to obtain the rubber prepolymer.

[0082] The remaining steps are the same as in Example 1, and a comparative rubber composite material is obtained.

[0083] Comparative Example 3

[0084] The difference between this comparative example and Example 1 is that the ionic liquid is a thiol-containing monoimidazolium aprotic ionic liquid. Specifically, 1-butyl-3-methylimidazolium bromide (1 g, 4.6 mmol) was dissolved in 5 mL of ethanol, and potassium hydroxide (0.26 g, 4.6 mmol) was dissolved in 300 μL of deionized water. After mixing the two, a large amount of white precipitate KBr was produced. The mixture was filtered and the filtrate was collected. 3-mercaptopropionic acid (0.49 g, 4.6 mmol) was dissolved in 1 mL of ethanol and slowly added dropwise to the filtrate. After shaking for 1 min, the ethanol was removed by rotary evaporation, and the mixture was freeze-dried for 12 h to remove water, yielding the target product, a thiol-containing monoimidazolium aprotic ionic liquid, with the following structural formula:

[0085]

[0086] By weight, 100 parts of natural rubber, 6 parts of mercapto-containing monoimidazolium aprotic ionic liquid, 60 parts of silica, 6 parts of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 2 parts of stearic acid, 3 parts of zinc oxide, 2.5 parts of sulfur, 1 part of N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin are mixed in an internal mixer for 8 minutes, and then sheeted out through an open mill to obtain the rubber prepolymer.

[0087] The remaining steps are the same as in Example 1, and a comparative rubber composite material is obtained.

[0088] Comparative Example 4

[0089] The difference between this comparative example and Example 1 is that the ionic liquid is a thiol-containing diimidazolium proton-type ionic liquid. Specifically, 3-mercaptopropionic acid (1 g, 9.4 mmol) and diimidazolium butane (0.9 g, 4.7 mmol) were dissolved in 5 mL of ethanol, and the mixture was stirred at room temperature for 4 h under a nitrogen atmosphere. After removing the solvent using a rotary evaporator, the target product, a thiol-containing diimidazolium proton-type ionic liquid, was obtained, with the following structural formula:

[0090]

[0091] By weight, 100 parts of natural rubber, 6 parts of thiol-containing diimidazolium proton ionic liquid, 60 parts of silica, 6 parts of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 2 parts of stearic acid, 3 parts of zinc oxide, 2.5 parts of sulfur, 1 part of N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin are mixed in an internal mixer for 8 minutes, and then sheeted out through an open mill to obtain the rubber prepolymer.

[0092] The remaining steps are the same as in Example 1, and a comparative rubber composite material is obtained.

[0093] Example 4

[0094] The following tests were conducted on the performance of Examples 1-4 and Comparative Examples 1-4 of the present invention. The test items and methods are as follows:

[0095] Ionic liquid structure characterization: The synthesized ionic liquid was characterized using an AVANCE III HD 500MHz nuclear magnetic resonance spectrometer. 1 For H NMR characterization, 5 mg of sample was dissolved in 600 μL of DMSO-d6 and then tested, with 16 scans performed.

[0096] Determination of vulcanization curve: The vulcanization curve of the rubber composite material prepared above was tested using a BL-6190 rotorless vulcanizer (Baisheng Machinery Equipment Factory). According to GB / T 9869-2014 standard, the temperature was set to 150℃ and the time was set to 30min. The vulcanization curve of the compound was measured, and the positive vulcanization time T was determined. 90 .

[0097] Stress-strain performance test: According to the method specified in GB / T 528-2009, the 100% constant elongation stress, 300% constant elongation stress, tensile strength and elongation at break of the rubber composite material prepared as described above are determined.

[0098] Rubber toughness: The area of ​​the closed curve between the stress-strain curve and the X-axis in the stress-strain performance test of the sample.

[0099] Rubber crosslinking density: The crosslinking density of vulcanized rubber was determined using the equilibrium swelling method. Specifically, 1 g of vulcanized rubber was immersed in 30 mL of toluene for three days, with the toluene being replaced every 24 hours. After immersion, the solvent on the sample surface was quickly absorbed with a paper towel, and the sample weight (m1) was measured. Then, the sample was vacuum dried at 60 °C in a vacuum oven until constant weight, and the sample weight (m2) was recorded. The crosslinking density V of the sample was determined. c Calculated according to the Flory-Rehner equation:

[0100]

[0101] In the formula, M c The molecular weight between cross-linking points is calculated using the following formula:

[0102]

[0103] In the formula, ρ p The density of NR is 0.912 g / cm³. 3 V s The molar volume of toluene is 106.3 cm³. 3 / mol), χ is the interaction parameter between NR and toluene, V r V represents the volume fraction of the swollen sample.r Calculated using the following formula:

[0104]

[0105] In the formula, m f ρ represents the mass of the filler material in the sample. s The density of toluene is 0.866 g / cm³. 3 ).

[0106] All test results are shown in Tables 1 and 2 below.

[0107] Table 1. Experimental characterization results of samples 1–4

[0108]

[0109] Table 2. Experimental characterization results of comparative samples 1–4

[0110]

[0111]

[0112] Experimental data analysis:

[0113] The cross sections of the rubber composite materials prepared in Example 1 and Comparative Example 1 were characterized by scanning electron microscopy (SEM). Figure 6 Comparative Example 1 showed a large number of silica agglomerates, indicating poor dispersion compatibility in rubber. Example 1 showed a smooth cross-section and no silica agglomeration was observed inside. This indicates that the addition of a dithiol-containing imidazolium aprotic ionic liquid improved the agglomeration of silica in the rubber matrix due to thermodynamic incompatibility, achieving nanoscale dispersion in the rubber matrix.

[0114] The test data for Examples 1-4 and Comparative Examples 1-4 are shown in Tables 1 and 2 above. The test results show that Example 1 has a 100% constant elongation stress of 3.5 MPa, a 300% constant elongation stress of 12.5 MPa, a tensile strength of 29.1 MPa, and an elongation at break of 540%. Compared to Comparative Example 1, which did not contain the dithiol-containing imidazolium aprotic ionic liquid, its mechanical properties are significantly improved. The vulcanization time (T) of Example 1... 90The curing time of Example 1 was 9.3 min, while that of Comparative Example 1 was more than twice as long (19.9 min). This indicates that the dithiol-containing bisimidazole aprotic ionic liquid can catalyze the silanization reaction between the silane coupling agent and silica at high temperatures, shortening the curing time, improving the dispersion compatibility of silica in the rubber matrix, and significantly enhancing the interaction between organic and inorganic components, thereby improving the mechanical properties of the rubber composite material. Rubber composite materials prepared by changing the cationic structure of the dithiol-containing bisimidazole aprotic ionic liquid (Examples 2 and 3) and changing the type of rubber (Example 4) all maintained excellent mechanical properties, demonstrating the universality of adding the dithiol-containing bisimidazole aprotic ionic liquid to this rubber composite material system.

[0115] Compared to Example 1, the mechanical properties of the rubber composites prepared by replacing the terminal active functional groups of the dithiol-containing bisimidazole aprotic ionic liquid with amino groups (Comparative Example 2) and the thiol-containing monoimidazole aprotic ionic liquid (Comparative Example 3) both showed a significant decrease. The crosslinking density of the samples was tested using the equilibrium swelling method; in Example 1, it was 2.6 × 10⁻⁶. -4 mol / cm 3 The values ​​for Comparative Examples 2 and 3 were only 1.8 × 10⁻⁶. -4 mol / cm 3 and 2.1×10 -4 mol / cm 3 This is because amino groups cannot chemically couple with the double bonds on the rubber chain. Therefore, the amino-containing bisimidazole aprotic ionic liquid in Comparative Example 2 can only catalyze the silanization reaction between silica and Si69, and cannot further increase its chemical crosslinking density. On the other hand, the mercapto-containing monoimidazole aprotic ionic liquid can only undergo a click chemical reaction with the double bonds on the rubber molecular chain at one end, and cannot crosslink different rubber molecular chains. Therefore, it cannot increase its crosslinking density, resulting in limited improvement in the mechanical properties of the rubber composite material.

[0116] The toughness of Example 1 is 82.7 MJ / m. 3 The toughness of Comparative Example 3 is 70.6 MJ / m. 3 This is because the two ends of the dithiol-containing bisimidazole aprotic ionic liquid are chemically coupled to the rubber molecular chain. Under external force, the extension and movement of the rubber molecular chain leads to continuous dissociation and association between the cations and anions, dissipating a large amount of energy, thus resulting in higher toughness. Furthermore, the effect of the type of ionic liquid (protonated and aprotic) on the toughness of the rubber composite was compared. The rubber composite prepared by adding the dithiol-containing bisimidazole protonated ionic liquid (Comparative Example 4) had a toughness of 76.4 MJ / m. 3This indicates that adding a dithiol-containing imidazolium aprotic ionic liquid can improve the toughness of rubber composites. This is because the Coulomb force between the cations and anions in protic ionic liquids is weaker than that in aprotic ionic liquids, resulting in lower energy dissipation.

[0117] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A high-toughness, high-strength rubber composite material, characterized in that: The product is prepared by hot-pressing and vulcanizing a uniform mixture of a rubber matrix, a dithiol-containing imidazolium aprotic ionic liquid, silica, silane coupling agent, stearic acid, zinc oxide, vulcanizing agent, accelerator, and paraffin wax. The mass ratio of the rubber matrix, the dithiol-containing imidazolium aprotic ionic liquid, silica, silane coupling agent, stearic acid, zinc oxide, vulcanizing agent, accelerator, and paraffin wax is 60-100:1-20:10-80:1-20:1-3:2-4:1-4:1-3:1-3. The structural formula of the dithiol-containing imidazolium aprotic ionic liquid is: R1 is selected from sulfonate anion motifs and carboxylate anion motifs, with the following structures: R2 is a C1–12 aliphatic alkane chain or alkoxy chain. R3 is a C1-12 aliphatic alkane chain or alkoxy chain.

2. The high-toughness, high-strength rubber composite material as described in claim 1, characterized in that: The rubber matrix is ​​selected from natural rubber, styrene-butadiene rubber, epoxy rubber and silicone rubber.

3. The high-toughness, high-strength rubber composite material as described in claim 1, characterized in that: The preparation method of dithiol-containing imidazolium aprotic ionic liquid includes the following steps: a. Alkylation reaction, the reaction route is as follows: b. The two-step anion exchange reaction has the following reaction route:

4. The high-toughness, high-strength rubber composite material as described in claim 1, characterized in that: The silane coupling agent is selected from mercapto-based silane coupling agents and vinyl-based silane coupling agents.

5. The high-toughness, high-strength rubber composite material as described in claim 4, characterized in that: The silane coupling agent is bis-[γ-(triethoxysilane)propyl]tetrasulfide.

6. The high-toughness, high-strength rubber composite material as described in claim 1, characterized in that: The vulcanizing agent is sulfur.

7. The high-toughness, high-strength rubber composite material as described in claim 1, characterized in that: The accelerator is N-cyclohexyl-2-benzothiazole sulfenamide.

8. The high-toughness, high-strength rubber composite material as described in claim 1, characterized in that: The rubber matrix is ​​natural rubber or styrene-butadiene rubber, the silane coupling agent is bis-[γ-(triethoxysilyl)propyl]tetrasulfide, the vulcanizing agent is sulfur, the accelerator is N-cyclohexyl-2-benzothiazole sulfenamide, and the structural formula of the di-thiol-containing imidazole aprotic ionic liquid is as follows:

9. A method for preparing a high-toughness, high-strength rubber composite material according to any one of claims 1 to 8, characterized in that: include: The rubber matrix, a dithiol-containing imidazolium aprotic ionic liquid, silica, silane coupling agent, stearic acid, zinc oxide, vulcanizing agent, accelerator, and paraffin wax are mixed in an internal mixer for 7-9 minutes, and then sheeted out through an open mill to obtain a rubber prepolymer. The positive vulcanization time is determined to be 5-20 minutes by a rotorless vulcanizing apparatus. The high-toughness and high-strength rubber composite material is obtained by hot pressing in a flat plate hot press at 14-16 MPa pressure and 145-155℃ for 5-20 minutes.

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