Self-repairing reinforced rubber composite material based on dynamic covalent bond interface and preparation method thereof

Abstract

The invention provides a self-repairing reinforced rubber composite material based on a dynamic covalent bond interface and a preparation method of the self-repairing reinforced rubber composite material, and relates to the technical field of high polymer materials and nano composite materials. The preparation method comprises the following steps: (1) carrying out surface pretreatment on nano calcium carbonate; (2) preparation of a functionalized nano filler; (3) chemically modifying the rubber matrix; and (4) composite vulcanization and dynamic interface construction. The self-repairing reinforced rubber composite material prepared by the method disclosed by the invention has better toughness, fatigue resistance and interface self-repairing capability, can be recycled, reprocessed and utilized, and has a better application prospect.

Description

Technical Field

[0001] This invention belongs to the technical field of polymer materials and nanocomposite materials, specifically relating to a self-healing reinforced rubber composite material based on a dynamic covalent bond interface and its preparation method. Background Technology

[0002] Nano-calcium carbonate (nano-CaCO3) is a highly promising functional filler in the rubber industry due to its low cost and abundant reserves. However, a natural interfacial incompatibility exists between the hydrophilic inorganic surface of nano-calcium carbonate and the hydrophobic organic rubber matrix, leading to its easy aggregation within the matrix and hindering its effective reinforcing effect. Existing technologies mainly address this issue through surface modification. For example, physical coating with fatty acids such as stearic acid is a simple process, but it results in weak interfacial bonding and limited improvement in mechanical properties. To enhance interfacial bonding, silane or titanate coupling agents are used to form covalent "molecular bridges" at the interface. However, the lack of sufficient active hydroxyl groups on the calcium carbonate surface leads to low grafting efficiency of silane coupling agents, resulting in very limited modification effects.

[0003] Whether through physical adsorption or traditional covalent coupling, the resulting filler-matrix interface is essentially static. When the composite material is subjected to stress, once debonding or chemical bond breakage occurs at the interface, the damage is permanent and irreversible. This rigid interface connection often comes at the cost of material toughness, becoming a source of material fatigue and failure. Therefore, to address the shortcomings of existing technologies, it is urgent to develop a novel interface design strategy to overcome the inherent rigidity and brittleness of traditional interfaces. Summary of the Invention

[0004] The purpose of this invention is to provide a self-healing reinforced rubber composite material based on a dynamic covalent bond interface and its preparation method, which effectively overcomes the defects of traditional interfaces such as rigidity and brittleness, inability to repair the filler-matrix interface after damage, and resulting in a decline in material properties.

[0005] To achieve the above or other objectives, the present invention is implemented through the following technical solutions.

[0006] A method for preparing a self-healing reinforced rubber composite material based on a dynamic covalent bond interface includes the following steps: (1) surface pretreatment of nano-calcium carbonate; (2) preparation of functionalized nanofillers; (3) chemical modification of the rubber matrix; and (4) composite vulcanization and dynamic interface construction.

[0007] In the preparation method disclosed in this invention, step (1) of surface pretreatment of nano-calcium carbonate involves surface treatment of nano-calcium carbonate to construct an anchoring layer containing active functional groups on its surface, thereby obtaining pretreated nano-calcium carbonate. Preferably, the average particle size of the nano-calcium carbonate is 20~100 nm.

[0008] In step (2), the preparation of functionalized nanofillers involves reacting the pretreated nano-calcium carbonate obtained in step (1) with a modifier containing a first reactive functional group. The first reactive functional group in the modifier is covalently grafted onto the anchoring layer surface of the pretreated nano-calcium carbonate to obtain functionalized nanofillers, thus giving the surface of the functionalized nanofillers the first reactive functional group. The first reactive functional group is a maleimide functional group or a furan functional group.

[0009] Step (3) chemical modification of the rubber matrix involves modifying the rubber matrix using a modifying monomer containing a second reactive functional group to obtain a modified rubber matrix, thereby introducing a second reactive functional group onto the rubber molecular chain. Preferably, the rubber matrix is ​​selected from one or more of natural rubber (NR), styrene-butadiene rubber (SBR), cis-butadiene rubber (BR), nitrile rubber (NBR), or ethylene propylene diene monomer (EPDM). The second reactive functional group is a maleimide functional group or a furan functional group.

[0010] The first reactive functional groups grafted onto the surface of the functionalized nanofiller are complementary to the second reactive functional groups on the surface of the modified rubber matrix, enabling a Diels-Alder reversible reaction. In step (4), the composite vulcanization and dynamic interface construction involve mixing and vulcanizing the functionalized nanofiller with the modified rubber matrix, causing a DA reversible reaction between the first reactive functional groups on the surface of the functionalized nanofiller and the second reactive functional groups on the modified rubber matrix, forming a dense reversible covalent bond network at the interface. When the material is subjected to thermal stimulation (heating), a reverse-DA reaction can be triggered, causing the covalent bonds at the interface to break (e.g., in the initial stage of the repair process); after cooling, the DA reaction occurs again, regenerating covalent bonds, thereby repairing the interface connection.

[0011] Furthermore, the preparation method of self-healing reinforced rubber composite material based on dynamic covalent bond interface includes the following steps: (1) Surface pretreatment of nano-calcium carbonate: Disperse nano-calcium carbonate in a weakly alkaline buffer solution with a pH of 8.0~9.0, add dopamine or dopamine hydrochloride, and react under stirring. After the reaction is completed, centrifuge, wash and dry to obtain pretreated nano-calcium carbonate with a polydopamine (PDA) anchoring layer formed on the surface of nano-calcium carbonate. (2) Preparation of functionalized nanofillers: Pretreated nano-calcium carbonate with a polydopamine anchoring layer on the surface is dispersed in a solvent and ultrasonically dispersed until uniformly dispersed. A first modifier containing the first reactive functional group is added and the reaction is carried out at 40~80℃ for 6~24 h under stirring. After the reaction is completed, post-treatment is carried out to obtain functionalized nanofillers containing the first reactive functional group. (3) Chemical modification of rubber matrix: The rubber matrix is ​​modified by using a melt-mixing grafting method or a solution grafting method, and a modified monomer containing a second reactive functional group is used to obtain a modified rubber matrix, thereby introducing a second reactive functional group into the rubber molecular chain. (4) Composite vulcanization and dynamic interface construction: The modified rubber matrix obtained in step (3) is plasticized at 40~50℃ for 2~5 min, and the functionalized nanofiller and additives prepared in step (2) are added in sequence. The mixture is mixed until it is evenly dispersed, and then vulcanized. After vulcanization, it is cooled to obtain a self-healing reinforced rubber composite material based on dynamic covalent bond interface. In step (4), the first reactive functional group in the functionalized nanofiller and the second reactive functional group in the modified rubber matrix can undergo a reversible Diels-Alder reaction.

[0012] Preferably, the weakly alkaline solution can be selected from Tris buffer. Preferably, the mass-to-volume ratio (g / mL) of the nano-calcium carbonate to the weakly alkaline buffer solution is 1:(20~100).

[0013] Preferably, the mass ratio of dopamine or dopamine hydrochloride to nano-calcium carbonate is 1:(5~20).

[0014] Preferably, the reaction temperature after adding dopamine or dopamine hydrochloride is 25~50℃, and the reaction time is 12~48 h.

[0015] Preferably, the thickness of the polydopamine (PDA) anchoring layer is 2~10 nm.

[0016] Preferably, in step (2), the first modifier is selected from maleimide derivatives or furan derivatives. The first reactive functional group is a maleimide functional group or a furan functional group.

[0017] More preferably, the maleimide derivative is selected from one of N-(2-aminoethyl)maleimide, N-hydroxymaleimide, and 4-maleimide butyric acid.

[0018] The furan derivative is selected from one of furfurylamine, furfuryl alcohol, and furoic acid.

[0019] Preferably, the solvent is selected from DMF or ethanol. The amount of solvent used is sufficient to ensure uniform dispersion of the pretreated nano-calcium carbonate. Preferably, the amount of solvent used satisfies a solid-liquid ratio (g / mL) of 1:(10~50).

[0020] Preferably, the mass ratio of pretreated nano-calcium carbonate to the first modifier is 5:1 to 20:1.

[0021] Preferably, post-treatment includes, but is not limited to, centrifugation, washing, and drying. More preferably, the product is washed 3-5 times alternately with ethanol and deionized water to remove unreacted monomers. The product is then vacuum dried at 50-70°C.

[0022] Further, the second reactive functional group is a maleimide functional group or a furan functional group. Preferably, the modified monomer in step (3) is selected from one of furfuryl mercaptan, N-phenylmaleimide, N-(2-aminoethyl)maleimide, and 4-maleimide butyric acid.

[0023] Furthermore, in step (4), the first reactive functional group in the functionalized nanofiller and the second reactive functional group in the modified rubber matrix can undergo a reversible Diels-Alder reaction, that is: when the second reactive functional group on the surface of the modified rubber matrix is ​​a maleimide functional group, then the first reactive functional group on the surface of the functionalized nanofiller is a furan functional group; when the second reactive functional group on the surface of the modified rubber matrix is ​​a furan functional group, then the first reactive functional group on the surface of the functionalized nanofiller is a maleimide functional group.

[0024] Furthermore, the preparation method of the self-healing reinforced rubber composite material based on the dynamic covalent bond interface of the present invention may further include the following steps: (1) Surface pretreatment of nano-calcium carbonate: a) Place nano-calcium carbonate in an atomic layer deposition reactor, evacuate to 10~100 Pa, heat the reaction chamber to 100~200℃, and keep it at that temperature for 0.5~2 h; b) Introduce the metal precursor into the reaction chamber for 0.1~2.0 s, and purge with inert gas for 5~30 s to remove reaction byproducts and residual metal precursor; c) Introduce the oxidant precursor into the reaction chamber for 0.1~2.0 s, and purge with inert gas for 5~30 s to remove reaction byproducts and residual oxidant precursor; d) Repeat steps b) and c) until the thickness of the metal oxide anchoring layer formed on the surface of the nano-calcium carbonate meets the requirements, and obtain pretreated nano-calcium carbonate with a metal oxide anchoring layer formed on the surface of the nano-calcium carbonate; (2) Preparation of functionalized nanofillers: Pretreated nano-calcium carbonate with metal oxide anchoring layer on surface is dispersed in anhydrous organic solvent and ultrasonically dispersed until uniformly dispersed. Silane coupling agent modifier containing the first reactive functional group is added and stirred under inert gas protection. After the reaction is completed, functionalized nanofillers containing the first reactive functional group are obtained through treatment. (3) Chemical modification of rubber matrix: The rubber matrix is ​​modified by using a melt-mixing grafting method or a solution grafting method, and a modified monomer containing a second reactive functional group is used to obtain a modified rubber matrix, thereby introducing a second reactive functional group into the rubber molecular chain. (4) Composite vulcanization and dynamic interface construction: The modified rubber matrix obtained in step (3) is plasticized at 40~50℃ for 2~5 min, and the functionalized nanofiller and additives prepared in step (2) are added in sequence. The mixture is mixed until it is evenly dispersed, and then vulcanized. After vulcanization, it is cooled to obtain a self-healing reinforced rubber composite material based on dynamic covalent bond interface. In step (4), the first reactive functional group in the functionalized nanofiller and the second reactive functional group in the modified rubber matrix can undergo a reversible Diels-Alder reaction.

[0025] Preferably, the metal precursor is selected from trimethylaluminum, titanium tetrachloride, or diethylzinc. The oxidant precursor is selected from deionized water or ozone.

[0026] In this invention, atomic layer deposition (ALD) is used to process nano-calcium carbonate, forming a uniform and dense metal oxide anchoring layer on its surface. The metal oxide anchoring layer varies depending on the selected metal precursor. The metal oxide anchoring layer formed in this invention is an Al₂O₃ anchoring layer, a TiO₂ anchoring layer, or a ZnO anchoring layer.

[0027] Preferably, the thickness of the metal oxide anchoring layer is 1~5 nm.

[0028] Preferably, the silane coupling agent modifier is selected from silane coupling agents containing maleimide or furan end groups. More preferably, the silane coupling agent modifier is selected from 3-(2-furanyl)propyl-trimethoxysilane, N-(3-triethoxysilylpropyl)maleimide, and N-[3-(triethoxysilyl)propyl]-2-furancarboxamide.

[0029] More preferably, the anhydrous organic solvent in step (2) can be toluene. Preferably, the mass-to-volume ratio (g / mL) of the anhydrous organic solvent to the pretreated nano-calcium carbonate is 1:(10~50).

[0030] More preferably, the mass ratio of pretreated nano-calcium carbonate to silane coupling agent modifier is 10:1 to 40:1.

[0031] More preferably, the reaction time in step (2) under an inert gas is 4 to 12 h and the reaction temperature is 60 to 110 °C.

[0032] More preferably, after the reaction is complete, the solid is centrifuged, washed, and dried. The solid is collected by centrifugation, washed 3 to 5 times with toluene or ethanol to remove physically adsorbed silane, and then dried under vacuum at 80 to 100°C.

[0033] In this invention, step (3) chemical modification of the rubber matrix can be performed by melt mixing grafting or solution grafting.

[0034] Preferably, the chemical modification of the rubber matrix in step (3) is performed using a melt-blending grafting method, which includes the following steps: The rubber matrix is ​​plasticized at 60~100℃ for 2~5 min, then the modified monomer and initiator are added, and the mixing reaction is continued for 10~30 min to obtain a modified rubber matrix containing a second reactive functional group.

[0035] Preferably, the chemical modification of the rubber matrix in step (3) is performed using a solution grafting method, including the following steps: The rubber matrix is ​​dissolved in an organic solvent to prepare a rubber liquid with a mass fraction of 5-15%. Under nitrogen protection, the modified monomer and initiator are added, and the mixture is stirred at 60-90°C for 4-12 hours. After the reaction is completed, the rubber liquid is poured into ethanol to precipitate. After washing and vacuum drying at 40-60°C, a modified rubber matrix containing a second reactive functional group is obtained.

[0036] Preferably, the modified monomer in step (3) is selected from one of furfuryl mercaptan, N-phenylmaleimide, N-(2-aminoethyl)maleimide, and 4-maleimide butyric acid. The second reaction functional group is a maleimide functional group or a furan functional group.

[0037] Preferably, the initiator is selected from AIBN or BPO.

[0038] More preferably, in the melt-blending grafting method, the mass ratio of modified monomer, initiator and rubber matrix is ​​(1~5):(0.1~1.0):100.

[0039] Preferably, in the solution grafting method, the mass ratio of the modified monomer to the rubber matrix is ​​2~10:100, and the mass ratio of the initiator to the rubber matrix is ​​(0.2~2.0):100.

[0040] Preferably, the initiator is selected from AIBN or BPO.

[0041] Preferably, the organic solvent is selected from toluene or xylene.

[0042] Furthermore, the additives in step (4) include zinc oxide, stearic acid, antioxidant, softener, sulfur, and accelerator.

[0043] Preferably, the mass ratio of modified rubber matrix, functionalized nanofiller, zinc oxide, stearic acid, antioxidant, softener, sulfur, and accelerator is 100 : (5~30) : (3~5) : (1~2) : (1~2) : (1~5) : (1~2.5) : (0.5~1.5).

[0044] Preferably, the rubber compound is subjected to triangular wrapping or thin-pass treatment to ensure uniform texture. After triangular wrapping or thin-pass treatment, it is left to stand at 25°C for 12-24 hours to eliminate internal stress.

[0045] Preferably, the vulcanization pressure is 10~15 MPa, the vulcanization temperature is 140~170℃, and the vulcanization time is 10~30 min.

[0046] Preferably, after vulcanization, the material is naturally cooled to 25°C. During the cooling process, the first reactive functional group on the surface of the functionalized nanofiller and the second reactive functional group on the modified rubber matrix recognize each other and undergo chemical bonding, thereby constructing a thermally reversible dense dynamic covalent bond network between the nano-calcium carbonate filler and the rubber matrix in situ. Further, in step (4), the first reactive functional group in the functionalized nanofiller and the second reactive functional group in the modified rubber matrix can undergo a reversible Diels-Alder reaction, that is: when the second reactive functional group on the surface of the modified rubber matrix is ​​a maleimide functional group, then the first reactive functional group on the surface of the functionalized nanofiller is a furan functional group; when the second reactive functional group on the surface of the modified rubber matrix is ​​a furan functional group, then the first reactive functional group on the surface of the functionalized nanofiller is a maleimide functional group.

[0047] A second aspect of this invention protects a self-healing reinforced rubber composite material based on a dynamic covalent bond interface prepared by the above-described preparation method. The self-healing reinforced rubber composite material of this invention achieves self-healing capability and high toughness by constructing a dynamic, reversible covalent bond network at the interface between the filler and the rubber matrix, which is responsive to external stimuli (heat).

[0048] In summary, the preparation method provided by this invention is simple to operate. The self-healing reinforced rubber composite material based on a dynamic covalent bond interface prepared by this invention involves modifying the nanofiller by grafting a first reactive functional group onto its surface to obtain a functionalized nanofiller; modifying the rubber matrix by grafting a second reactive functional group to obtain a modified rubber matrix with the second reactive functional group grafted onto its surface. When the functionalized nanofiller and the modified rubber matrix are mixed and vulcanized to prepare the reinforced rubber composite material, the first reactive functional group and the second reactive functional group undergo a Diels-Alder reaction to construct a covalent bond interface. This interface is thermally reversible. When damage occurs, heating triggers a retro-Diels-Alder reaction to dissociate the local chemical bonds, and then a Diels-Alder reaction occurs again during cooling to re-bond, thereby achieving self-repair of the interface damage.

[0049] The self-healing reinforced rubber composite material based on a dynamic covalent bond interface prepared in this invention has the following advantages: 1. Enhanced toughness and fatigue resistance: When the self-healing reinforced rubber composite is subjected to stress, the DA bonds at the interface can break and recombine through a reversible reverse reaction, effectively absorbing and dissipating energy and inhibiting the propagation of microcracks. 2. Interface self-healing ability: When the self-healing reinforced rubber composite material is damaged, heating it to a specific temperature (such as 110-130℃) can trigger the reverse-DA reaction, which breaks the covalent bonds at the damaged interface; then cooling it at a lower temperature (such as below 80℃) will cause the DA reaction to occur again, repairing the interface connection and restoring the mechanical properties of the material. 3. Recycling and reprocessing potential: By controlling the connection and disconnection of interfacial bonds through heat, new possibilities are provided for the recycling and reprocessing of thermosetting rubber composites. Attached Figure Description

[0050] Figure 1 Transmission electron microscope (TEM) images of the functionalized nano-calcium carbonate prepared in Example 1 of the present invention and the untreated nano-calcium carbonate in Comparative Example 1.

[0051] Figure 2 Fourier transform infrared (FTIR) spectra of the functionalized nano-calcium carbonate prepared in Example 1 of the present invention and the functionalized failed nano-calcium carbonate in Comparative Example 1.

[0052] Figure 3 The thermogravimetric analysis (TGA) spectra of the packings in Examples 1, 3 and Comparative Example 1 of this invention are shown. Detailed Implementation

[0053] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0054] It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. It should also be understood that the terminology used in the embodiments of this invention is for describing specific implementations and not for limiting the scope of protection of this invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0055] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" used in this specification are only for clarity of description and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as part of the scope of the invention.

[0056] Example 1

[0057] A method for preparing a composite material based on a PDA anchoring layer and a natural rubber matrix: (1) Batching and pretreatment: 10 g of nano-calcium carbonate with an average particle size of 60 nm was dispersed in 500 mL of Tris buffer solution (10 mM, pH 8.5). 1 g of dopamine hydrochloride was added, and the mixture was magnetically stirred at 25 °C for 24 hours to allow dopamine to undergo an oxidative self-polymerization reaction on the surface of the nano-calcium carbonate. After the reaction was completed, the product was collected by centrifugation and repeatedly washed with deionized water and ethanol. Then, it was vacuum dried at 60 °C to obtain nano-calcium carbonate (nano-CaCO3@PDA) with a polydopamine anchoring layer on the surface. The thickness of the polydopamine anchoring layer was 2~10 nm.

[0058] (2) Functionalized nanofiller: 5 g of nano-CaCO3@PDA was dispersed in 50 mL of N,N-dimethylformamide (DMF) and sonicated for 15 minutes to ensure uniform dispersion. 1 g of N-(2-aminoethyl)maleimide was added, and the mixture was reacted at 60 °C for 12 hours under nitrogen protection to graft maleimide functional groups onto the surface of the polydopamine anchoring layer. After the reaction was completed, the mixture was centrifuged, washed with toluene or ethanol, and dried to obtain maleimide-functionalized nano-calcium carbonate (nano-CaCO3@PDA-Mal).

[0059] (3) Modification of rubber matrix: 100 g of natural rubber was plasticized at 60 °C for 5 minutes in a torque rheometer. 2 g of furfuryl mercaptan and 0.5 g of azobisisobutyronitrile (AIBN) were added, and the mixture was continued to be mixed for 15 minutes. Under this temperature and shear action, the initiator decomposed and initiated a free radical reaction, grafting furfuryl mercaptan onto the natural rubber molecular chain to obtain modified natural rubber with furan functional groups on the side chain.

[0060] (4) Compounding and vulcanization: The modified natural rubber obtained in step (3) is rolled on a two-roll mill, and 10 g of nano-CaCO3@PDA-Mal filler obtained in step (2), 1 g of antioxidant 4010NA, 1 g of accelerator CZ and 2 g of sulfur are added in sequence. After passing through the mill 5 times, the mixture is sheeted out and left at room temperature for 24 hours. The compound is placed in a mold and vulcanized on a flat vulcanizing machine at 150°C and 10 MPa pressure for 20 minutes. After vulcanization, the sample is taken out and cooled naturally to room temperature so that the maleimide functional groups on the filler surface and the furan functional groups in the rubber matrix can complete chemical cross-linking, and a self-healing reinforced rubber composite material with dynamic covalent bond interface is obtained.

[0061] Example 2

[0062] A method for preparing a composite material based on an ALD anchoring layer and a styrene-butadiene rubber matrix: (1) Batching and pretreatment: 10 g of nano-calcium carbonate powder with an average particle size of 100 nm was placed in a fluidized bed atomic layer deposition reactor. At 200 °C, trimethylaluminum (TMA) was introduced into the reaction chamber for 1.0 s, and inert gas was introduced for 10 s to remove the reaction byproducts and residual trimethylaluminum (TMA); water vapor was introduced into the reaction chamber for 2.0 s, and inert gas was introduced for 20 s to remove the reaction byproducts and residual water vapor; the above steps were repeated 20 times to obtain nano-calcium carbonate with an alumina (Al2O3) anchoring layer with a thickness of 2 nm on the surface, and pretreated nano-calcium carbonate nano-CaCO3@Al2O3 was obtained.

[0063] (2) Functionalized nanofiller: 5 g of nano-CaCO3@Al2O3 powder was subjected to vacuum heat treatment in toluene to remove physically adsorbed water on the surface. Then, 0.25 g of 3-(2-furanyl)propyl-trimethoxysilane was added, and the mixture was refluxed at 80 °C for 8 hours. The silane end groups reacted with the hydroxyl groups on the Al2O3 surface, covalently grafting furan functional groups onto the filler surface. After the reaction was completed, the filler was centrifuged, washed with toluene or ethanol, and vacuum dried at 100 °C to obtain furan-functionalized nano-calcium carbonate (nano-CaCO3@Al2O3-Furan).

[0064] (3) Rubber matrix modification: 100 g of styrene-butadiene rubber (SBR) was dissolved in toluene to prepare a rubber liquid with a mass fraction of 5~15%. 2 g of N-phenylmaleimide and 0.5 g of benzoyl peroxide (BPO) initiator were added and reacted at 80 °C for 6 hours to graft maleimide functional groups onto the SBR molecular chain to obtain the modified rubber matrix - maleimide functionalized styrene-butadiene rubber.

[0065] (4) Compounding and vulcanization: The maleimide-functionalized styrene-butadiene rubber obtained in step (3) is mixed with 10g of furan-functionalized nano-calcium carbonate (nano-CaCO3@Al2O3-Furan) obtained in step (2), 4g of zinc oxide, 1.5g of stearic acid, 1.5g of antioxidant 4010NA, 1.8g of sulfur, and 1.2g of accelerator CBS. After being mixed evenly on a two-roll mill, it is molded and vulcanized at 160°C for 25 minutes.

[0066] Example 3

[0067] A method for preparing a composite material based on a PDA anchoring layer and a nitrile rubber matrix: (1) Ingredient preparation and pretreatment: Same as step (1) in Example 1, to obtain nano-CaCO3@PDA.

[0068] (2) Functionalized nanofiller: Same as step (2) in Example 1, to obtain nano-CaCO3@PDA-Mal.

[0069] (3) Rubber matrix modification: 100g of nitrile butadiene rubber (NBR) was plasticized on a two-roll mill, 2g of furfuryl mercaptan and 0.5g of AIBN were added, and the mixture was mixed at 70°C for 20 minutes to graft furan functional groups onto the NBR molecular chain.

[0070] (4) Compounding and vulcanization: The furan-functionalized nitrile rubber obtained in step (3) is compounded and vulcanized with 10 grams of nano-CaCO3@PDA-Mal obtained in step (2) according to the method in Example 1.

[0071] Example 4

[0072] The preparation method of this embodiment is the same as that of Example 1. The difference between this embodiment and Example 1 is that the first modifier in step (2) is furfurylamine, and the modifying monomer in step (3) is N-(2-aminoethyl)maleimide.

[0073] Example 5

[0074] The preparation method of this embodiment is the same as that of Example 2. The difference between this embodiment and Example 2 is that the first modifier in step (2) is N-(3-triethoxysilylpropyl)maleimide, and the modifier monomer in step (3) is furfuryl mercaptan.

[0075] Comparative Example 1 This comparative example is intended to illustrate the necessity of the surface pretreatment step (as a control of Example 2).

[0076] (1) Functionalization attempt: Take 5g of raw nano calcium carbonate without any pretreatment (same batch as in Example 1 and Example 2), and react it directly with 0.25g of 3-(2-furanyl)propyl-trimethoxysilane in toluene under reflux at 80°C for 8 hours. After the reaction, the control filler is obtained by centrifugation, washing and drying.

[0077] (2) Preparation of composite material: 100g of styrene-butadiene rubber (same as in Example 2) was grafted and modified in the same way (grafted with N-phenylmaleimide), and then 10g of the control filler obtained in step (1) above was added. The mixture was then mixed and vulcanized according to the same vulcanizing aid and process as in Example 2.

[0078] Comparative Example 2 This comparative example aims to illustrate the importance of the "dynamically reversible" feature of interface keys.

[0079] (1) Preparation of static interface: The nano-CaCO3@Al2O3 intermediate was prepared using the same atomic layer deposition process as in step (1) of Example 2. 5 g of nano-CaCO3@Al2O3 was dispersed in toluene and ultrasonically dispersed until uniform. 1 g of a conventional silane coupling agent without reversible functional groups, such as 3-aminopropyltriethoxysilane (APTES), was added, and the mixture was refluxed at 80 °C for 8 hours. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain amino-functionalized nano-calcium carbonate.

[0080] (2) Compounding and vulcanization: 100g of unmodified styrene-butadiene rubber (SBR) was plasticized on a two-roll mill. Then, 10g of the above-mentioned amino-functionalized filler, as well as zinc oxide, stearic acid, antioxidant, sulfur and accelerator (the same amount as in Example 2) were added and mixed evenly. The compound was then molded and vulcanized at 160°C for 25 minutes.

[0081] Results analysis: In this system, although the amino groups on the filler surface can undergo certain physical adsorption or hydrogen bonding with the rubber matrix or other additives, they cannot form thermally reversible covalent bonds like DA bonds (i.e., a static interface is constructed).

[0082] Performance Characterization 1. The functionalized nano-calcium carbonate prepared in Example 1—maleimide-functionalized nano-calcium carbonate—and the untreated nano-calcium carbonate used in Comparative Example 1 were subjected to TEM testing. The results are as follows: Figure 1As shown in the figure, the PDA-pretreated nano-calcium carbonate particles in Example 1 have a uniformly thick anchoring layer on their surface. In contrast, the untreated nano-calcium carbonate particles in Comparative Example 1 have a smooth surface without any coating layer.

[0083] 2. The furan-functionalized nano-calcium carbonate (nano-CaCO3@Al2O3-Furan) prepared in Example 2 and the control filler (raw calcium carbonate directly treated with silane) obtained in step (1) of Comparative Example 1 were subjected to Fourier transform infrared (FTIR) tests. The obtained spectra are as follows. Figure 2 As shown in the figure. It can be seen from the figure that the FTIR spectrum of Example 2 is at 1500 cm⁻¹. -1 and 740cm -1 A distinct furan ring characteristic absorption peak appeared nearby; while in the spectrum of Comparative Example 1, no characteristic absorption peaks related to furan functional groups appeared or only very weak ones appeared, indicating that without the Al2O3 anchoring layer to provide abundant hydroxyl groups, silane coupling agents are difficult to effectively graft onto the calcium carbonate surface.

[0084] 3. Thermogravimetric analysis (TGA) was performed on the furan-functionalized nano-calcium carbonate (nano-CaCO3@Al2O3-Furan) prepared in Example 2 and the control packing material (directly silane-treated raw calcium carbonate) obtained in step (1) of Comparative Example 1. The results are as follows: Figure 3 As shown in the figure, the TGA curve of the product of Comparative Example 1 shows that its thermal weight loss rate is less than 5 wt.%, which is much lower than that of the product of Example 2. This further confirms that the grafting efficiency of the silane coupling agent is extremely low due to the lack of sufficient active hydroxyl groups on the surface of the original calcium carbonate; while the calcium carbonate pretreated by ALD (Example 2) successfully grafted a large amount of furan silane, which has the basis for constructing a sufficient amount of dynamic covalent bonds with the rubber matrix.

[0085] 4. Tensile tests were conducted on the rubber composite materials obtained in Examples 1, 2, and 3, as well as Comparative Examples 1 and 2 (referring to GB / T528 standard). A self-healing test was also performed. The test method was as follows: the dumbbell-shaped rubber composite material specimen was completely cut, the cut surfaces were tightly fitted together, and the specimen was heated in a 120℃ oven for 1 hour, then kept at 70℃ for 2 hours to complete the repair. Tensile tests were then performed again, and the mechanical properties before and after repair were compared to evaluate the self-healing efficiency. Specific data are shown in Table 1.

[0086] Table 1: Comparison of mechanical properties and repair efficiency of different rubber composite materials

[0087] As can be seen from the data in Table 1, the self-healing reinforced rubber composites of Examples 1, 2, and 3 prepared using the method of this invention, due to the successful construction of a high-density dynamic interface, not only exhibit excellent initial mechanical properties, but also demonstrate significant self-healing capabilities, with tensile strength recovery efficiency exceeding 75% after undergoing a fracture-repair cycle. In contrast, Comparative Example 1, lacking a pretreatment layer, suffered from failed coupling agent grafting, resulting in extremely weak interfacial bonding, low strength, and no repair capability (relying solely on minimal thermal diffusion of rubber molecules, leading to extremely low efficiency). Comparative Example 2 exhibited better initial strength (due to static coupling), but the interfacial bonds were irreversible, unable to reassemble once broken, thus resulting in extremely low repair efficiency. This fully demonstrates the synergistic necessity of the "pretreatment anchoring layer" and the "dynamically reversible" characteristics of the interfacial bonds.

[0088] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a self-healing reinforced rubber composite material based on a dynamic covalent bond interface, characterized in that, Includes the following steps: (1) Surface pretreatment of nano-calcium carbonate; (2) Preparation of functionalized nanofillers; (3) Chemical modification of rubber matrix; (4) Composite vulcanization and dynamic interface construction.

2. The preparation method according to claim 1, characterized in that, Includes the following steps: (1) Surface pretreatment of nano-calcium carbonate: Disperse nano-calcium carbonate in a weakly alkaline buffer solution with a pH of 8.0~9.0, add dopamine or dopamine hydrochloride, and react under stirring. After the reaction is completed, centrifuge, wash and dry to obtain pretreated nano-calcium carbonate with a polydopamine anchoring layer formed on the surface of nano-calcium carbonate. (2) Preparation of functionalized nanofillers: Pretreated nano-calcium carbonate with a polydopamine anchoring layer on the surface is dispersed in a solvent and ultrasonically dispersed until uniformly dispersed. A first modifier containing the first reactive functional group is added and the reaction is carried out at 40~80℃ for 6~24 h under stirring. After the reaction is completed, post-treatment is carried out to obtain functionalized nanofillers containing the first reactive functional group. (3) Chemical modification of rubber matrix: The rubber matrix is ​​modified by using a melt-mixing grafting method or a solution grafting method, and a modified monomer containing a second reactive functional group is used to obtain a modified rubber matrix, thereby introducing a second reactive functional group into the rubber molecular chain. (4) Composite vulcanization and dynamic interface construction: The modified rubber matrix obtained in step (3) is plasticized at 40~50℃ for 2~5 min, and the functionalized nanofiller and additives prepared in step (2) are added in sequence. The mixture is mixed until it is evenly dispersed, and then vulcanized. After vulcanization, it is cooled to obtain a self-healing reinforced rubber composite material based on dynamic covalent bond interface. In step (4), the first reactive functional group in the functionalized nanofiller and the second reactive functional group in the modified rubber matrix can undergo a reversible Diels-Alder reaction.

3. The preparation method according to claim 2, characterized in that, In step (2), the first modifier is selected from maleimide derivatives or furan derivatives; the first reactive functional group is a maleimide functional group or a furan functional group.

4. The preparation method according to claim 2, characterized in that, In step (3), the modified monomer is selected from one of furfuryl mercaptan, N-phenylmaleimide, N-(2-aminoethyl)maleimide, and 4-maleimide butyric acid; the second reaction functional group is a maleimide functional group or a furan functional group.

5. The preparation method according to claim 1, characterized in that, Includes the following steps: (1) Surface pretreatment of nano-calcium carbonate: a) Place nano-calcium carbonate in an atomic layer deposition reactor, evacuate to 10~100 Pa, heat the reaction chamber to 100~200℃, and keep it at that temperature for 0.5~2 h; b) Introduce the metal precursor into the reaction chamber for 0.1~2.0 s, and purge with inert gas for 5~30 s to remove reaction byproducts and residual metal precursor; c) Introduce the oxidant precursor into the reaction chamber for 0.1~2.0 s, and purge with inert gas for 5~30 s to remove reaction byproducts and residual oxidant precursor; d) Repeat steps b) and c) until the thickness of the metal oxide anchoring layer formed on the surface of the nano-calcium carbonate meets the requirements, and obtain pretreated nano-calcium carbonate with a metal oxide anchoring layer formed on the surface of the nano-calcium carbonate; (2) Preparation of functionalized nanofillers: Pretreated nano-calcium carbonate with metal oxide anchoring layer on surface is dispersed in anhydrous organic solvent and ultrasonically dispersed until uniformly dispersed. Silane coupling agent modifier containing the first reactive functional group is added and stirred under inert gas protection. After the reaction is completed, functionalized nanofillers containing the first reactive functional group are obtained through treatment. (3) Chemical modification of rubber matrix: The rubber matrix is ​​modified by using a melt-mixing grafting method or a solution grafting method, and a modified monomer containing a second reactive functional group is used to obtain a modified rubber matrix, thereby introducing a second reactive functional group into the rubber molecular chain. (4) Composite vulcanization and dynamic interface construction: The modified rubber matrix obtained in step (3) is plasticized at 40~50℃ for 2~5 min, and the functionalized nanofiller and additives prepared in step (2) are added in sequence. The mixture is mixed until it is evenly dispersed, and then vulcanized. After vulcanization, it is cooled to obtain a self-healing reinforced rubber composite material based on dynamic covalent bond interface. In step (4), the first reactive functional group in the functionalized nanofiller and the second reactive functional group in the modified rubber matrix can undergo a reversible Diels-Alder reaction.

6. The preparation method according to claim 5, characterized in that, In step (2), the silane coupling agent modifier is selected from silane coupling agents containing maleimide end groups or furan end groups, and the first reactive functional group is a maleimide functional group or a furan functional group.

7. The preparation method according to claim 5, characterized in that, In step (3), the modified monomer is selected from one of furfuryl mercaptan, N-phenylmaleimide, N-(2-aminoethyl)maleimide, and 4-maleimide butyric acid; the second reaction functional group is a maleimide functional group or a furan functional group.

8. The preparation method according to claim 2 or 5, characterized in that, Step (3) Chemical modification of the rubber matrix includes the following steps: the rubber matrix is ​​plasticized at 60~100℃ for 2~5 min, then the modified monomer and initiator are added, and the mixing reaction is continued for 10~30 min to obtain a modified rubber matrix containing a second reactive functional group.

9. The preparation method according to claim 2 or 5, characterized in that, Step (3) Chemical modification of the rubber matrix includes the following steps: dissolving the rubber matrix in an organic solvent to prepare a rubber liquid with a mass fraction of 5-15%, adding the modifying monomer and initiator under nitrogen protection, stirring and reacting at 60-90℃ for 4-12 hours, after the reaction is completed, pouring the rubber liquid into ethanol to precipitate, washing, and vacuum drying at 40-60℃ to obtain a modified rubber matrix containing a second reactive functional group.

10. The self-healing reinforced rubber composite material based on a dynamic covalent bond interface prepared by the preparation method according to any one of claims 1 to 9.

Images