High-strength wear-resistant recycled rubber composite material and preparation method thereof

Abstract

The application relates to the technical field of high polymer composite materials, in particular to a high-strength wear-resistant recycled rubber composite material and a preparation method thereof. The application discloses a high-strength wear-resistant recycled rubber composite material and a preparation method thereof, the composite material takes deeply activated waste rubber powder as a reinforcing core, and is coated with an oriented graphene / liquid crystal epoxy reinforcing shell layer on the surface; a microcapsule is used to release mercapto silane, and the mercapto silane is coupled with a high-frequency vibration regenerated free radical to construct a dynamic disulfide bond interface bonding layer. The preparation method integrates deep eutectic-microwave activation, extrusion flow field orientation and interface precise construction process. The application has the advantages of high strength, high wear resistance and self-repairing capacity, and realizes high-value conversion of waste rubber.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a high-strength, wear-resistant reclaimed rubber composite material and its preparation method. Background Technology

[0002] With the widespread use of rubber products, the environmental problems caused by waste rubber solid waste such as waste tires are becoming increasingly serious. Reclaimed rubber powder, due to its low cost and environmental benefits, has been attempted as a filler or matrix for new rubber products. However, directly adding large amounts of waste rubber often leads to a significant decrease in the mechanical properties of composite materials. Furthermore, while high hardness or high reinforcing components typically improve the wear resistance of materials, they often come at the cost of reduced toughness and flexural fatigue resistance. Especially at low temperatures, the material becomes brittle, and stress concentration easily occurs at the interface between the wear-resistant layer and the flexible matrix, leading to cracking. Therefore, it is often difficult to simultaneously achieve both low-temperature wear resistance and resistance to repeated bending.

[0003] Existing technologies enhance the performance of composite materials by bonding waste rubber powder to the matrix at the interface or introducing dynamic reversible bonds. For example, CN113845733A discloses a waste rubber powder-filled polypropylene blend and its preparation method. This method uses high-speed mechanical mixing with liquid EPDM rubber to modify the surface of the waste rubber powder, resulting in core-shell structured particles with liquid EPDM rubber as the shell and waste rubber powder as the core—i.e., modified waste rubber powder. The resulting modified waste rubber powder significantly improves the dispersibility of the waste rubber powder in the polypropylene matrix and the interfacial adhesion between the two, thus exerting the reinforcing and toughening effect of the waste rubber powder. CN118165377A discloses a low-heat-generating, ultra-high mechanical property tread rubber composite material containing reversible bonds, its preparation method, and the resulting product. This tread rubber composite material, by weight, includes 30-60 parts of natural rubber (NR), 40-70 parts of solution-polymerized styrene-butadiene rubber (SSBR), and 6-28 parts of tire performance functional components. The vinyl anhydride compounds in the provided tread rubber composites can participate in the vulcanization process and form hydrogen bonds and reversible chemical bonds with 2-aminopyrimidine compounds and zinc chloride, giving the rubber composites the characteristics of low heat generation, good resilience, and excellent mechanical properties. However, excessive desulfurization and the introduction of dynamic bonds may damage the rubber backbone, reduce the mechanical strength or hardness of the composite material, and prevent it from possessing both self-healing properties and mechanical properties.

[0004] In summary, how to innovate a new technical solution to comprehensively improve the strength and wear resistance of materials with high recycled rubber content through interface synergy enhancement and the introduction of dynamic bonds has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-strength wear-resistant reclaimed rubber composite material and its preparation method, so as to solve the technical problems in the prior art such as the difficulty in achieving both high strength and high wear resistance, insufficient dynamic fatigue performance, and the contradiction between low-temperature wear resistance and flexural strength.

[0006] The specific technical solution is as follows: A high-strength, wear-resistant reclaimed rubber composite material comprises a vulcanized matrix rubber phase and composite particles dispersed therein. The composite particles are characterized by comprising a core layer of waste rubber powder pre-activated by surface selective desulfurization, and an orientation-reinforced shell layer coating the surface of the core layer. The orientation-reinforced shell layer is formed by curing a liquid crystal epoxy resin, carboxylated graphene, and a latent epoxy curing system. The carboxylated graphene is oriented along the extrusion traction direction in the shell layer, with an average orientation degree ƒ of not less than 0.70. An interfacial bonding layer exists between the vulcanized matrix rubber phase and the composite particles. This interfacial bonding layer comprises a dynamic sulfur-containing bonded structure formed by the reaction of γ-mercaptopropyltrimethoxysilane released from thermally responsive microcapsules with sulfur-containing active sites on the rubber powder surface, a silane coupling agent, and the rubber vulcanization network.

[0007] Furthermore, the surface-selective desulfurization pre-activated waste rubber powder has a surface free radical density of not less than 9 × 10⁻⁶. 17 spins / g.

[0008] Furthermore, the waste adhesive powder has a particle size of 60-100 mesh.

[0009] Furthermore, the thermoresponsive microcapsule has a rupture temperature range of 115~125℃, the core material is the γ-mercaptopropyltrimethoxysilane, and the wall material is a thermosetting resin formed by the co-condensation of urea, formaldehyde and phenolic compounds; the mass content of the core material of the thermoresponsive microcapsule is ≥70%.

[0010] A method for preparing a high-strength, wear-resistant recycled rubber composite material includes the following steps: S1: Waste truck tire rubber powder is added to the main feed port of the co-rotating twin-screw extruder. At the same time, the deep eutectic obtained by reacting choline chloride with p-toluenesulfonic acid hydrate is fed in through the heat-insulated gear pump and kneaded with the rubber powder under high-speed conditions to form a high-viscosity rubber powder-deep eutectic slurry. The slurry then enters the microwave reactor and reacts under the protection of continuous nitrogen gas. After the reaction is completed, activated rubber powder is obtained. The recovered liquid is returned to the feed port of the extruder side by the condenser pump for recycling.

[0011] S2: Pre-treat the liquid crystal epoxy resin for later use. Prepare a concentrated slurry with preliminary graphene orientation by mixing the liquid crystal epoxy resin, carboxylated graphene, and a latent epoxy curing agent in a three-roll mill. Add this slurry and activated adhesive powder to a twin-screw extruder and melt-blend under vacuum to achieve uniform coating of the adhesive powder. The coated composite material is then extruded through a slit extrusion die. A strong planar stretching flow is generated during melt extrusion, forcing the liquid crystal epoxy resin molecular chains and the dispersed graphene sheets to achieve a highly consistent orientation along the extrusion direction. The extruded, continuously oriented strip with an internal orientation structure, 0.3 mm thick, is immediately subjected to rapid quenching in a cold water bath below 20°C to freeze the orientation structure. The rapidly quenched strip is then placed in an 80°C hot air channel for 20 minutes for stage B pre-curing. Finally, the cured continuous strips are fed into an underwater pelletizer to be cut into ellipsoidal particles. After dehydration and drying, composite particles with graphene and liquid crystal epoxy resin orientation reinforcement layers on the surface are obtained.

[0012] S3: Using a screw reactor, with zones 1-3 set to 70-90℃ and screw speed at 80 r / min, rubber granules, natural rubber, epoxidized natural rubber, maleic anhydride graft polymer, ZnO, stearic acid, antioxidant, and silane coupling agent are sequentially added. Then, thermoresponsive microcapsules are added to the side feed port in zone 4. These microcapsules are dispersed and heated using the kneading element in this zone, remaining for 10 seconds to rupture and release γ-mercaptopropyltrimethoxysilane. The material then enters the high-frequency vibration energy field in zone 5. The vibration energy causes instantaneous active sites to form in situ at the sulfur-containing bonds at the rubber powder interface, which then undergo click coupling with the released γ-mercaptopropyltrimethoxysilane. The material immediately enters zone 6 and is rapidly cooled in a 5℃ brine jacket using a static mixer, promoting the coupling of newly formed free radicals with the thiol silane released from the thermoresponsive microcapsules. The mixture is then discharged and air-cooled to below 80℃ to obtain the compound.

[0013] S4: Transfer the mixed rubber to a two-roll mill at a roller temperature of 60°C, add sulfur and accelerator TBBS in sequence, and sheet the rubber after passing through the mill 6 times. After the rubber compound has been left to stand for 8 hours, perform two-stage vulcanization to further crosslink the residue of the thermally responsive microcapsules. After demolding, allow it to cool naturally to room temperature to obtain a high-strength and wear-resistant reclaimed rubber composite material.

[0014] Furthermore, the waste truck tire rubber powder in S1 has a particle size of 60-100 mesh; the mass ratio of choline chloride to p-toluenesulfonic acid hydrate is (20-30):(70-72); the microwave reactor has a cavity wall temperature of 145-155℃ and a reaction time of 25-35 seconds.

[0015] Further, in S2, the mass ratio of the liquid crystal epoxy resin and carboxylated graphene is (7~9):(1.2~1.8); the screw speed of the melt blending is 100~300 rpm; the die temperature of the casting die is 100~120℃, the slit gap is 0.1~0.3 mm, and the traction speed is 2~10 m / min.

[0016] Furthermore, the maleic anhydride grafted polymer in S3 accounts for 1.5~2.5% of the mass of the particles; the temperature in zone 4 needs to be raised to 115~125℃; and the high-frequency vibration energy field needs to be subjected to high-frequency vibration of 10~50kHz.

[0017] Furthermore, in the two-stage vulcanization described in S4, the first stage is set with conditions of 128~132℃×18~22min, and the second stage is set with conditions of 155~165℃×9~11min.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) Core performance improvement: This invention achieves breakthroughs in core mechanical properties, long wear resistance life and dynamic fatigue resistance of reclaimed rubber composite materials through triple innovation of molecular activation, structural orientation and interface reconstruction.

[0019] (2) Intelligent and green process: The new process of continuous deep activation and directional compounding completes the online circulation of solvent and precise coupling of energy simultaneously, which greatly improves process efficiency and significantly reduces energy consumption and emissions.

[0020] (3) Performance consistency and reliability: By upgrading the key interface reaction from a diffusion-dependent random process to a controlled directional reaction, the influence of material properties on the mixing process fluctuation is greatly reduced, ensuring the batch high stability and reliability of the composite material's high strength, high wear resistance and self-healing properties.

[0021] (4) Microcapsule intelligent repair: By introducing intelligent microcapsules and dynamic chemical networks, the material is endowed with inherent self-sensing and self-repair capabilities, enabling it to transform from passively bearing damage to actively repairing damage, which greatly extends the service life of the product under harsh working conditions. Attached Figure Description

[0022] Figure 1 This is a flowchart of a high-strength, wear-resistant reclaimed rubber composite material and its preparation method according to the present invention.

[0023] Figure 2 This is a schematic diagram of the cross-sectional structure and gradient section of the composite granules in Embodiment 1 of the present invention.

[0024] Figure 3 This is an analysis diagram of the orientation structure of graphene in Example 1 of the present invention.

[0025] Figure 4 This is a schematic diagram of the intelligent interface construction and self-repair mechanism in Embodiment 1 of the present invention.

[0026] Figure 5 This is a comparison chart of the experimental results for tensile strength, DIN wear, self-healing efficiency, total crosslinking density, and dynamic disulfide bond ratio in Experimental Example 1 of this invention. Detailed Implementation

[0027] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0028] The technical solution designed by this invention to solve the existing problems includes the following key points: 1. Deep eutectic microwave continuous desulfurization and precise free radical activation Traditional regeneration processes rely on high temperatures and strong shearing, which can easily lead to excessive degradation of molecular chains. The deep eutectic-microwave treatment step of this invention is primarily used for selective desulfurization and pre-activation of the surface layer of waste rubber powder, rather than requiring the treated rubber powder to retain high-density free radicals in the deep eutectic solvent for an extended period. Specifically, the choline chloride / p-toluenesulfonic acid deep eutectic solvent preferentially wets the sulfur-containing bond regions in the crosslinked network of the waste rubber powder, and under microwave irradiation, promotes the selective weakening or breakage of SS and CS bonds. After treatment, residual deep eutectic solvent is removed by ethanol / water washing, centrifugation, and vacuum devolatilization to avoid its quenching or competing effects on subsequent interfacial reactions.

[0029] The generation of interfacial free radicals mainly occurs in the subsequent high-frequency vibrational interface construction steps. After the thermoresponsive microcapsules release γ-mercaptopropyltrimethoxysilane, the material is immediately subjected to a high-frequency vibrational energy field, which causes the sulfur-containing bonds on the surface of the pre-activated rubber powder to generate instantaneous active sites. After generation, these active sites couple with the interface-enriched mercaptosilane and the rubber vulcanization network, thereby constructing a dynamic sulfur-containing interfacial bonding layer.

[0030] 2. Extrusion flow field induced-quenching locked graphene orientation enhancement technology In traditional processes, nanofillers are randomly dispersed during mixing, resulting in low reinforcement efficiency. Therefore, this invention employs a process combining melt blending and extrusion flow field orientation. First, carboxylated graphene and liquid crystal epoxy resin are prepared into a pre-dispersed slurry, which is then melt-blended with activated adhesive powder. Subsequently, the encapsulated composite material is extruded through a slit extrusion die, achieving orientation in a strong tensile flow field. In this flow field, the graphene sheets are driven by hydrodynamic forces, forced to undergo planar rotation and oriented alignment. Simultaneously, due to the entry of the liquid crystal epoxy resin into the nematic phase at the processing temperature, the long axes of its rod-shaped molecules exhibit long-range directional ordering in the flow field. These ordered liquid crystal molecules further induce the graphene sheets through π-π stacking and van der Waals forces, causing their planes to gradually rotate until they are aligned parallel to the long axes of the molecules and the flow field direction. The planar tensile flow and boundary shear flow generated by the melt during extrusion synergistically enhance this orientation process, ultimately forming a tile-like stacked topology of the graphene sheets within the encapsulation layer, with the sheet planes parallel to the adhesive powder surface and highly aligned along the extrusion direction.

[0031] The above-mentioned graphene orientation process is completed in the extrusion flow field, such as... Figure 2 As shown, the surface of the rubber powder, after deep eutectic treatment and microwave deep activation, is not only rich in free radicals but also exposes a large number of silanol groups (-Si-OH) originating from the carbon black filler inside the rubber and active sulfur species generated by broken sulfur bonds. The curing of the orientation-reinforced shell does not rely solely on a small number of functional groups on the surface of the waste rubber powder, but is jointly completed by the liquid crystal epoxy resin and the latent epoxy curing system during the B-stage pre-curing after extrusion orientation and the subsequent vulcanization heat treatment. The carboxyl / hydroxyl groups of carboxylated graphene can interact with the liquid crystal epoxy system and improve the shell continuity; at the same time, the silane coupling agent and the γ-mercaptopropyltrimethoxysilane released by the microcapsules participate in the interfacial coupling between the rubber powder, the shell, and the rubber matrix during the vulcanization stage. The resulting structure includes a chemically cured liquid crystal epoxy network, oriented graphene sheets, and a dynamic sulfur-containing interfacial bonding layer, rather than relying solely on physical rapid freezing to obtain a stable shell.

[0032] To lock this metastable structure, this invention employs a programmed rapid cooling process to achieve the kinetic freezing of the micro-arrangement. The core mechanism lies in the fact that when the cooling rate exceeds the relaxation rate of the liquid crystal molecular segments, the system will cross its glass transition temperature in an extremely short time. During this critical process, the conformational rearrangement of the polymer segments is abruptly suppressed, and the free volume of the molecules is instantaneously fixed. This rapidly freezes the highly oriented liquid crystal molecules in the nematic ordered state and the induced graphene alignment into a non-equilibrium glassy state. Essentially, this frozen structure is achieved by controlling the rapid cooling kinetic path to fix the highly oriented structure induced by an external force field within the glassy state of the material, thus making this orientation configuration an inherent and stable microstructural feature of the material.

[0033] To verify the effect of extrusion flow field induction and rapid cooling locking processes on the orientation structure of graphene sheets, this invention performs two-dimensional wide-angle X-ray scattering analysis on the composite particles prepared in Example 1. Figure 3 As shown, its two-dimensional diffraction pattern exhibits a distinct arc-shaped feature on the characteristic diffraction rings of graphene, indicating that the sheets possess significant orientational order. Integrating the diffraction rings by azimuth angle yields the following results: Figure 3 The azimuth scanning curve shown exhibits a sharp diffraction peak at the azimuth angle perpendicular to the extrusion flow direction. Calculations indicate that the average orientation degree ƒ of the graphene sheets is no less than 0.70. This data quantitatively demonstrates that the graphene extrusion flow field-induced quenching and locking pre-orientation reinforcement unit technology designed in this invention successfully constructs a highly oriented reinforcing shell of graphene on the surface of the adhesive powder.

[0034] 3. Controlled thermal triggering and precise construction process of mechatronic interface Traditional interface modification relies on random coupling reactions, which cannot achieve dynamic repair. This invention constructs a precise repair and enhancement method for interfaces. Figure 4 As shown, firstly, to achieve precise delivery of the repair agent to the target interface layer in a complex compounding system, this invention designs a temperature-triggered thermoresponsive microcapsule (UFPR microcapsule). Its wall material is a urea-formaldehyde-phenol-formaldehyde resin interpenetrating network. By precisely controlling the crosslinking density, its glass transition and thermal decomposition occur synergistically within a narrow temperature window of 115-125°C. The capsule core material is γ-mercaptopropyltrimethoxysilane, which possesses both coupling and dynamic bonding functions. When the composite material enters the preset 120°C interface reaction zone, the thermoresponsive microcapsule wall material simultaneously undergoes mechanical softening and chemical degradation, rupturing under the combined effect of internal vapor pressure and external shear force. This programmatically releases the liquid repair agent to the heterogeneous interface with a rubber powder-film gradient interpenetration, rather than dispersing it within the rubber matrix. This ensures that the repair agent preferentially diffuses and accumulates in the intermediate dynamic bonds and layers of the gradient interface, providing a foundation for subsequent highly selective and efficient interface repair and strengthening reactions.

[0035] To further ensure the efficiency and selectivity of the interfacial reaction, the material enters a high-frequency vibrational energy field simultaneously with the release of the repair agent from the microcapsules. Under specific high-frequency vibrations, the vibrational energy is selectively deposited in the interfacial region through molecular friction and cavitation effects, preferentially initiating mechanochemical homolytic cleavage of the pre-weakened CS bonds on the surface of the adhesive powder and the bottom layer of the film. This results in the instantaneous regeneration of a high concentration of sulfur-centered free radicals at the target interface. These newly generated free radicals immediately undergo a highly efficient thiol-alkene click reaction with the mercaptosilane molecules already targeted and enriched at the interface, precisely constructing a strong and dynamically repairable chemical interface.

[0036] Example 1 Table 1 Raw Material Information Table A high-strength, wear-resistant recycled rubber composite material and its preparation method, comprising the following steps: S0: Using 100 parts of deionized water as the reaction medium, add 5 parts of an aqueous solution of ethylene-maleic anhydride copolymer as a polymeric emulsifier. Then, add 10 parts of urea and 5 parts of phenol sequentially, stir to dissolve, and then add 30 parts of the core material γ-mercaptopropyltrimethoxysilane dropwise at room temperature. Use a homogenizer to continuously shear at 600-900 rpm for 30 minutes to form a stable oil-in-water emulsion. Then, add 25 parts of a 37% formaldehyde aqueous solution dropwise, and slowly titrate with a 10% citric acid aqueous solution to precisely control the pH of the system between 2.5 and 3.0. Heat the system to 55-60℃ at a heating rate of approximately 1℃ / min, and mechanically stir for 2-3 hours to allow the urea, phenol, and formaldehyde to undergo a condensation reaction. The resulting insoluble copolymer deposits and coats the surface of the silane oil droplets, gradually solidifying to form a dense core-shell structure. After the reaction, the product was naturally cooled to room temperature, filtered under vacuum, washed three times successively with deionized water and anhydrous ethanol, and finally dried in a vacuum drying oven at 60°C for 12 hours to obtain white, free-flowing powdered UFPR microcapsules. The rupture temperature range of the UFPR microcapsules prepared in this example was determined to be 115~125°C, and the core material content was ≥70%.

[0037] S1: 100 parts of 80-mesh waste truck tire rubber powder are added to the main feed port of a co-rotating twin-screw extruder. At the same time, 29 parts of choline chloride and 71 parts of p-toluenesulfonic acid hydrate are dehydrated in a reactor at 80°C and -0.09MPa for 2 hours to obtain a deep eutectic solvent. 15 parts of the deep eutectic solvent are fed into the reactor via a heat-insulated gear pump and kneaded with the rubber powder at 80°C and 350r / min for 45 seconds to form a high-viscosity rubber powder-deep eutectic slurry. The slurry is then introduced into a 2.45GHz, 1kW cylindrical microwave reactor and held at 150°C for 30 seconds under continuous nitrogen protection to obtain activated rubber powder.

[0038] S2: The liquid crystal epoxy resin is pre-dried under vacuum at 80℃ for 2 hours to remove trace amounts of moisture, then filtered through a 200-mesh filter bag to remove mechanical impurities, and subsequently kept at 60℃ for later use. Eight parts of liquid crystal epoxy resin, 1.5 parts of carboxylated graphene, and 0.5 parts of latent epoxy curing agent are continuously passed through a three-roll mill at 80℃ and 5MPa pressure three times to prepare a pre-dispersed slurry. This pre-dispersed slurry is added together with 100 parts of activated adhesive powder to a twin-screw extruder and melt-blended under vacuum conditions at 90℃ and a screw speed of 200rpm to achieve uniform coating of the adhesive powder by the slurry. The coated composite material is then extruded through a slit extrusion die. By controlling the die temperature at 110℃, the slit gap at 0.2mm, and the traction speed at 6m / min, a strong planar stretching flow is generated during melt extrusion. This flow field forces the liquid crystal epoxy resin molecular chains and the dispersed graphene sheets within them to align with a highly consistent orientation along the extrusion direction. The extruded, continuous strips with an internally oriented structure, 0.3 mm thick, are immediately subjected to rapid quenching in a cold water bath at a temperature below 20°C to freeze the orientation structure. The quenched strips are then placed in an 80°C hot air channel for 20 minutes for stage B pre-curing, allowing the epoxy resin to reach a semi-cured state to lock in the orientation structure. Finally, the cured continuous strips are fed into an underwater pelletizer to be cut into ellipsoidal particles of 3-5 mm. After dehydration and drying, composite granules coated with graphene and liquid crystal epoxy resin orientation reinforcement layers are obtained.

[0039] S3: Using a screw reactor, with zones 1-3 set to 70-90℃ and screw speed at 80 r / min, sequentially add 100 parts of composite rubber granules, 20 parts of natural rubber, 10 parts of epoxidized natural rubber, 2 parts of maleic anhydride graft polymer, 3 parts of ZnO, 2 parts of stearic acid, 2 parts of antioxidant 4020, and 1 part of silane coupling agent Si69. Mix for 45 seconds, controlling the rubber temperature ≤95℃. In zone 4, raise the temperature to 120℃, reduce the screw speed to 50 r / min, and side-feed 0.8 parts of UFPR microcapsules. Utilize the kneading element in this zone to disperse and heat them, holding for 10 seconds to ensure a breakage rate ≥90%. Subsequently, enter the high-frequency vibration energy field in zone 5. Under the condition of 160℃ and 30kHz high-frequency vibration, the selective deposition of vibration energy at the interface promotes the breakage of CS bonds on the rubber powder surface and the regeneration of free radicals. The material immediately enters zone 6 and is rapidly cooled to below 90°C in a 5°C brine jacket via a static mixer, promoting the coupling of newly generated free radicals with the thiol silanes released from the thermoresponsive microcapsules. After debinding and air cooling to below 80°C, the compound is obtained.

[0040] S4: Transfer the compounded rubber to an open mill at a roller temperature of 60°C, add 1.2 parts sulfur and 1.0 part accelerator TBBS in sequence, and sheet it after passing it through a thin mill 6 times; after the rubber compound has been left to stand for 8 hours, perform low-temperature two-stage vulcanization using a 400mm×400mm flat vulcanizing machine. The first stage is 130°C×20min to fix the orientation of the liquid crystal region, and the second stage is 160°C×10min to further crosslink the UFPR cracked residue; after demolding, allow it to cool naturally to room temperature to obtain a high-strength wear-resistant recycled rubber composite material.

[0041] Example 2 The preparation method is the same as in Example 1, except that: S1: 100 parts of 80-mesh waste truck tire rubber powder were replaced with 100 parts of 60-mesh waste truck tire rubber powder; 29 parts of choline chloride and 71 parts of p-toluenesulfonic acid hydrate were replaced with 28 parts of choline chloride and 70 parts of p-toluenesulfonic acid hydrate; 15 parts of deep eutectic solvent were replaced with 12 parts of deep eutectic solvent; the chamber wall temperature of 150℃ and the residence time of 30 seconds were replaced with the chamber wall temperature of 145℃ and the residence time of 25 seconds. S2: 8 parts liquid crystal epoxy resin, 1.5 parts carboxylated graphene, and 0.5 parts latent epoxy curing agent are replaced with 7 parts liquid crystal epoxy resin, 1.2 parts carboxylated graphene, and 0.3 parts latent epoxy curing agent; the screw speed of 200 rpm is replaced with a screw speed of 100 rpm; the die temperature of 110℃, the slit gap of 0.2 mm, and the traction speed of 6 m / min are replaced with a die temperature of 100℃, a slit gap of 0.1 mm, and a traction speed of 2 m / min. S3: 2 parts maleic anhydride grafted polymer were replaced with 1.5 parts maleic anhydride grafted polymer; the temperature of zone 4 was increased to 120°C was replaced with the temperature of zone 4 was increased to 115°C; the application of 30kHz high-frequency vibration was replaced with the application of 10kHz high-frequency vibration. S4: Replace the first stage of 130℃×20min with the first stage of 128℃×18min; replace the second stage of 160℃×10min with the second stage of 155℃×9min; All other steps are the same.

[0042] Example 3 The preparation method is the same as in Example 1, except that: S1: Replace 100 parts of 80-mesh waste truck tire rubber powder with 100 parts of 100-mesh waste truck tire rubber powder; replace 29 parts of choline chloride and 71 parts of p-toluenesulfonic acid hydrate with 30 parts of choline chloride and 72 parts of p-toluenesulfonic acid hydrate; replace 15 parts of deep eutectic solvent with 18 parts of deep eutectic solvent; replace 150℃ chamber wall temperature and 30-second dwell time with 155℃ chamber wall temperature and 35-second dwell time. S2: 8 parts liquid crystal epoxy resin, 1.5 parts carboxylated graphene, and 0.5 parts latent epoxy curing agent are replaced with 9 parts liquid crystal epoxy resin, 1.8 parts carboxylated graphene, and 0.8 parts latent epoxy curing agent; the screw speed of 200 rpm is replaced with a screw speed of 300 rpm; the die temperature of 110℃, the slit gap of 0.2 mm, and the traction speed of 6 m / min are replaced with a die temperature of 120℃, the slit gap of 0.3 mm, and the traction speed of 10 m / min. S3: 2 parts maleic anhydride grafted polymer were replaced with 2.5 parts maleic anhydride grafted polymer; the temperature of zone 4 was increased to 120°C was replaced with the temperature of zone 4 was increased to 125°C; the application of 30kHz high-frequency vibration was replaced with the application of 50kHz high-frequency vibration. S4: Replace the first stage of 130℃×20min with the first stage of 132℃×22min; replace the second stage of 160℃×10min with the second stage of 165℃×11min. All other steps are the same.

[0043] Comparative Example 1 The preparation method is the same as in Example 1, except that: S1: Take 100 parts of 80-mesh waste glue powder and do not perform DES-microwave treatment; All other steps are the same.

[0044] Comparative Example 2 The preparation method is the same as in Example 1, except that: S2: Replace 8 parts of liquid crystal epoxy resin with the same number of parts of bisphenol A type epoxy resin E-51; All other steps are the same.

[0045] Comparative Example 3 S2: The extrusion casting die step is omitted. The pre-dispersed slurry and activated adhesive powder are melted and mixed, and then directly injected into the mold for hot pressing without going through the extrusion casting die, and then cooled naturally. All other steps are the same.

[0046] Comparative Example 4 The preparation method is the same as in Example 1, except that: S3: Omit the steps of preparing and adding UFPR microcapsules, and replace them with 0.56 parts of liquid thiol silane added together with other raw materials at the initial stage of intensive mixing; All other steps are the same.

[0047] Experimental Example 1 The recycled rubber composite materials prepared in Examples 1-3 and Comparative Examples 1-4 were measured: (1) Tensile strength: Referring to GB / T 528-2009 "Vulcanized rubber or thermoplastic rubber - Determination of tensile stress-strain properties", the vulcanized composite material is first cut into standard specimens using a standard cutter. The specimens are symmetrically clamped in the upper and lower clamps of the testing machine, and the separation speed of the clamps is set to 500±50 mm / min. The testing machine is started, and the specimens are stretched at a uniform speed until they break. The instrument automatically records the force and displacement during the entire process and calculates the tensile strength based on the original cross-sectional area of ​​the specimens. The entire test process should be carried out at a standard laboratory temperature of 23±2℃. Each group of valid specimens should have no less than 5 specimens, and the final result is the average.

[0048] (2) DIN Abrasion Amount: Referring to GB / T 9867-2008 "Determination of Abrasion Resistance of Vulcanized Rubber or Thermoplastic Rubber (Rotating Roller Abrasion Tester Method)", the vulcanized composite material is first cut into standard cylindrical specimens using a cutting machine and conditioned at standard laboratory temperature for at least 16 hours. During the test, the specimen is pressed with a specified vertical force onto a rotating roller covered with standard abrasive cloth. The roller rotates at a fixed speed, and the specimen moves back and forth axially on the roller, with a total friction stroke of 40 meters. After the test, the mass of the specimen before and after wear is weighed using a precision balance, and the mass loss is the abrasion amount. To eliminate batch differences in abrasive cloth, the results need to be corrected and calculated with the abrasion amount of the standard reference rubber under the same conditions, and finally reported in the form of relative volumetric abrasion amount. The consistency of pressure, stroke and abrasive must be strictly controlled throughout the entire test process. At least two specimens should be tested for each group, and the average value of the results should be taken.

[0049] (3) Self-healing efficiency: Referring to ASTM F3625-23, "Standard Test Method: Determination of Self-Healing Efficiency of Elastomer Composites", a standard cut through the thickness was first made in the center area of ​​a dumbbell-shaped standard specimen using a sharp blade to simulate damage. The damaged specimen was then heat-treated in an oven at 80°C for 2 hours to trigger the self-healing process. After repair, the tensile strength of the repaired specimen was tested using a tensile testing machine under the exact same conditions as the original tensile strength determination. The self-healing efficiency was calculated as the percentage of the tensile strength of the repaired specimen to the tensile strength of the original intact specimen. To obtain reliable data, at least 5 parallel samples were tested in each group, and the average value was taken.

[0050] (4) Total crosslinking density and dynamic bond ratio: Referring to GB / T 7763-1987 "Determination of Swelling Index of Vulcanized Rubber", firstly, accurately weighed vulcanized rubber samples are immersed in a good solvent such as toluene and swelled at a constant temperature in the dark for at least 72 hours until swelling equilibrium is reached; after removal, the surface solvent is quickly wiped off and weighed, and then the swollen gel is placed in a vacuum oven to completely remove the solvent and weighed dry. The total crosslinking density is calculated using the Flory-Rehner equation. Then, Raman spectroscopy analysis is performed on the same gel sample after swelling equilibrium, specifically scanning the characteristic stretching vibration peak of disulfide bonds. The peak area is compared with the pre-established standard working curve to quantify the absolute content of dynamic disulfide bonds in the sample; the dynamic bond ratio of a single sample is finally calculated by (dynamic disulfide bond content / total crosslinking density) × 100%. The test results of multiple parallel samples in the same group need to be calculated as the average value and standard deviation as the final report data.

[0051] Table 2 Comparison of experimental results of Examples 1-3 and Comparative Examples 1-4 The experimental results of Examples 1-3 and Comparative Examples 1-4 are shown in Table 2 and Figure 5 As shown, the recycled rubber composite material prepared in Example 1 of this invention has a tensile strength of 28.4 MPa and a DIN abrasion loss of 66 mm. 3 With a self-healing efficiency of 75.2%, and its cross-linked network having both moderate cross-linking density and high dynamic bond ratio, it achieves synergistic optimization of high strength, high wear resistance and self-healing function, and has been identified as the best implementation method.

[0052] In Example 2, the melting temperature or stretching rate of the liquid crystal epoxy resin was slightly lower than the optimal setting, resulting in a decrease in the orientation order of graphene. This led to a slight decrease in reinforcement efficiency, manifested primarily as a slight reduction in tensile strength and wear resistance. Simultaneously, the instantaneous temperature or shear field intensity in the free radical generation region fluctuated by approximately ±2%, reducing the coupling efficiency of dynamic disulfide bonds and directly affecting the self-healing function. Example 3, by increasing the stretching ratio or quenching rate in the graphene orientation process, achieved a more perfect reinforcement structure. Simultaneously, precise control of the temperature and shear field matching during the free radical regeneration stage resulted in a more complete construction of the dynamic interface network. However, this optimization came at the cost of sacrificing process window width, increasing control costs, and potentially impairing the overall long-term performance of the material. Therefore, Example 3 is not the optimal implementation method.

[0053] Comparative Examples 1-4, lacking key technologies, showed varying degrees of reduced overall performance compared to the Examples. Comparative Example 1, by omitting the deep eutectic-microwave activation step and directly using unactivated raw waste adhesive powder for subsequent compounding, exhibited tensile strength less than half that of Example 1, abrasion increased more than fourfold, and its self-healing function almost failed. Microscopic network analysis revealed extremely low total crosslinking density and dynamic disulfide bond ratio, demonstrating that without precise initial molecular-level activation, sufficient reactive free radical sites cannot be generated on the adhesive powder surface, thus preventing the achievement of the expected technical effect. Comparative Example 2 replaced the liquid crystal ring with ordinary bisphenol A type epoxy resin E-51. The mechanical and functional properties of the oxygen resin exhibited a characteristic decline, with tensile strength and abrasion resistance significantly lower than those of the examples, and self-healing efficiency also decreased significantly. Microscopically, the proportion of dynamic disulfide bonds was significantly low, proving the lack of the orientation template effect unique to liquid crystal phases. Graphene sheets could not achieve long-range oriented alignment in the shear field, resulting in the inability to form the highly ordered rigid grid reinforcement structure of the examples. At the same time, the construction efficiency of the interface network also decreased due to the lack of an ordered environment. Comparative Example 3 omitted the extrusion flow field-induced orientation step, and its tensile strength and abrasion resistance were significantly lower than those of Example 1. However, since the dynamic interface construction step was still retained, the self-healing efficiency remained at a moderate level. These results demonstrate that without the macroscopically oriented tensile force field provided by extrusion stretching, the orientation tendency of the liquid crystal epoxy resin alone cannot induce a significant long-range ordered arrangement of graphene sheets, and the anisotropic properties of the material cannot be manifested. Comparative Example 4, which eliminated the UFPR microcapsules, resulted in a comprehensive deterioration of performance, with the self-healing efficiency drastically dropping to near zero and the proportion of dynamic disulfide bonds being extremely low, confirming the failure of dynamic network construction. Simultaneously, while the tensile strength and abrasion resistance were superior to other comparative examples, they were still significantly lower than those of the examples, indicating that the non-programmed addition of coupling agents also had a negative impact on the static interface. These results demonstrate that the programmed rupture of UFPR microcapsules, precisely transporting reactive components to the target interface and controlling their release timing, is a necessary condition for achieving high-density, highly selective dynamic interface chemistry.

[0054] In summary, this invention successfully prepared a recycled rubber composite material with high strength, high wear resistance, and high self-healing efficiency by constructing a technical system of molecular activation-structure orientation-intelligent interface. This system achieves directional activation of free radicals on the rubber powder surface through deep eutectic-microwave coupling, constructs an ordered graphene reinforcing framework by inducing and combining it with an extrusion flow field using a liquid crystal template, and precisely constructs a dynamic interface network through programmed triggering of thermally responsive microcapsules. Systematic comparative experiments confirm that each technical step has an irreplaceable synergistic effect, collectively forming a complete transformation path from waste rubber to high-performance materials, possessing both significant environmental benefits and industrialization potential.

Claims

1. A high-strength, wear-resistant reclaimed rubber composite material, comprising a vulcanized matrix rubber phase and composite rubber particles dispersed therein, characterized in that, The composite granules include a core layer of waste rubber powder pre-activated by surface selective desulfurization, and an orientation-reinforced shell layer covering the surface of the core layer. The orientation-reinforced shell layer is formed by curing liquid crystal epoxy resin, carboxylated graphene, and a latent epoxy curing system. The carboxylated graphene is oriented along the extrusion traction direction in the shell layer, with an average orientation degree ƒ of not less than 0.

70. An interfacial bonding layer exists between the vulcanized matrix rubber phase and the composite granules. The interfacial bonding layer contains a dynamic sulfur-containing bonded structure formed by the reaction of γ-mercaptopropyltrimethoxysilane released from thermally responsive microcapsules with sulfur-containing active sites on the surface of the rubber powder, silane coupling agents, and the rubber vulcanization network.

2. The high-strength, wear-resistant recycled rubber composite material as described in claim 1, characterized in that, The surface-selective desulfurization pre-activated waste rubber powder has a surface free radical density of not less than 9 × 10⁻⁶. 17 spins / g.

3. The high-strength, wear-resistant recycled rubber composite material as described in claim 1, characterized in that, The waste adhesive powder has a particle size of 60-100 mesh.

4. The high-strength, wear-resistant recycled rubber composite material as described in claim 1, characterized in that, The thermoresponsive microcapsule has a rupture temperature range of 115~125℃, the core material is γ-mercaptopropyltrimethoxysilane, and the wall material is a thermosetting resin formed by co-condensation of urea, formaldehyde and phenolic compounds; the mass content of the core material of the thermoresponsive microcapsule is ≥70%.

5. A method for preparing a high-strength, wear-resistant reclaimed rubber composite material according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1: The waste rubber powder is mixed with choline chloride / p-toluenesulfonic acid deep eutectic solvent and subjected to microwave treatment for surface selective desulfurization pre-activation; after treatment, the residual deep eutectic solvent is removed by washing, centrifugation and / or vacuum volatilization to obtain surface pre-activated waste rubber powder. S2: A pre-dispersed slurry is prepared by liquid crystal epoxy resin, carboxylated graphene and latent epoxy curing system; the pre-dispersed slurry is melt-blended with surface pre-activated waste adhesive powder and oriented by traction through a slit channel, followed by programmed cooling and B-stage pre-curing to obtain composite particles with an orientation-reinforced shell. S3: The composite rubber particles, natural rubber, epoxidized natural rubber, maleic anhydride graft polymer, zinc oxide, stearic acid, antioxidant and silane coupling agent are mixed and added to thermoresponsive microcapsules to release γ-mercaptopropyltrimethoxysilane. Then a high-frequency vibration energy field is applied to generate instantaneous active sites in situ at the interface of the rubber powder containing sulfur bonds, which then couple with the released γ-mercaptopropyltrimethoxysilane. S4: Sulfur and accelerator are added and two-stage vulcanization is carried out to form a synergistic cross-linked structure of rubber matrix, orientation-reinforced shell and interfacial bonding layer.

6. The method for preparing a high-strength, wear-resistant reclaimed rubber composite material as described in claim 5, characterized in that, The mass ratio of choline chloride / p-toluenesulfonic acid in S1 is (20~30):(70~72); the microwave treatment is performed at a temperature of 145~155℃ for a time of 25~35 seconds.

7. The method for preparing a high-strength, wear-resistant reclaimed rubber composite material as described in claim 5, characterized in that, The liquid crystal epoxy resin and carboxylated graphene described in S2 have a mass ratio of (7~9):(1.2~1.8).

8. The method for preparing a high-strength, wear-resistant reclaimed rubber composite material as described in claim 5, characterized in that, The melt blending described in S2 requires a screw speed of 100~300 rpm; the traction orientation requires a temperature of 100~120℃, a slit gap of 0.1~0.3 mm, and a traction speed of 2~10 m / min.

9. The method for preparing a high-strength, wear-resistant reclaimed rubber composite material as described in claim 5, characterized in that, The maleic anhydride grafted polymer in S3 accounts for 1.5~2.5% of the mass of the particles; the high-frequency vibration energy field has a vibration frequency of 10~50kHz.

10. The method for preparing a high-strength, wear-resistant recycled rubber composite material as described in claim 5, characterized in that, The two-stage vulcanization process described in S4 has the following conditions: the first stage is set at 128~132℃ for 18~22 min; the second stage is set at 155~165℃ for 9~11 min.

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