Self-healing and recyclable vulcanized rubber, its preparation method and application

Abstract

This disclosure provides a vulcanized rubber with self-healing and recyclable properties, its preparation method, and its applications, belonging to the field of rubber materials technology. The vulcanized rubber provided in this disclosure has the following weight proportions: 100 parts rubber, 1-10 parts a copolymer obtained by copolymerization of sulfur and a sulfur-containing disulfide in the presence of a first catalyst, 1-3 parts a second catalyst, 1-3 parts zinc oxide, 1-2 parts an antioxidant, and 10-50 parts carbon black. This disclosure achieves the self-healing and recyclable functions of the vulcanized rubber. The vulcanized rubber material prepared by this disclosure is simple and readily available, which is beneficial for extending the shelf life of rubber products and protecting the environment.

Description

Technical Field

[0001] This disclosure relates to the field of rubber materials technology, specifically to a vulcanized rubber with self-healing and recyclable properties, its preparation method, and its application. Background Technology

[0002] Rubber is one of the most widely used engineering materials. The vulcanization and cross-linking of rubber is a prerequisite for its excellent mechanical properties; however, the irreversible chemical bonds between rubber segments hinder the reprocessing and recycling of rubber materials. Due to the scarcity and rising prices of chemical resources, as well as increasing environmental awareness, waste management has become a significant issue in today's society. Finding effective self-healing and recycling methods for rubber is necessary and of industrial significance.

[0003] Self-healing rubber materials can be divided into two types according to the type of damage repair: exogenous and intrinsic. In exogenous self-healing materials, the repair agent is encapsulated within microcapsules, which are then placed within a rubber matrix. When damage occurs, the repair agent is consumed in the repair reaction. The repair agent refers to discrete particles (capsules) embedded in the rubber matrix. Therefore, for a given repair site, the repair agent is limited to a single use. Intrinsic self-healing materials utilize the material's own chemical structure properties, relying on reversible covalent and non-covalent chemical reactions for self-repair. The formation of these reversible dynamic bonds not only helps repair mechanical damage but also opens new avenues for the remodeling and recycling of cross-linked polymer products. Currently, concepts using different reversible dynamic groups, such as hydrogen bonds, disulfides, Diels-Alder reactions, and organometallic ligands, are attracting increasing attention in the field of intrinsic self-healing. However, these self-healing rubber materials generally suffer from low cross-linking degrees and poor mechanical properties, making them unsuitable for practical engineering applications of rubber materials.

[0004] Currently, sulfur remains the most widely used crosslinking agent in the rubber industry. However, although vulcanized rubber possesses excellent mechanical properties, the irreversibility of its three-dimensional crosslinked network makes it difficult to reprocess and recycle, placing a serious burden on the environment. Summary of the Invention

[0005] To address the aforementioned technical problems, this disclosure provides a vulcanized rubber with self-healing and recyclable properties, a method for its preparation, and its applications, aiming to at least partially solve at least one of the aforementioned technical problems.

[0006] As one aspect of this disclosure, a vulcanized rubber with self-healing and recyclable properties is provided, comprising the following proportions by weight: 100 parts rubber, 1-10 parts copolymer of sulfur and sulfur-containing disulfide obtained by copolymerization reaction in the presence of a first catalyst, 1-3 parts second catalyst, 1-3 parts zinc oxide, 1-2 parts antioxidant, and 10-50 parts carbon black.

[0007] As another aspect of this disclosure, a method for preparing vulcanized rubber with self-healing and recyclable properties is provided, comprising the following steps:

[0008] Rubber is added to an internal mixer and mixed at a first preset temperature.

[0009] The copolymer obtained by copolymerizing sulfur and sulfur-containing disulfide in the presence of a first catalyst and the second catalyst are added to a mixer and mixed at a first preset temperature.

[0010] Zinc oxide and antioxidant are added sequentially to a mixer and mixed at a first preset temperature to obtain a rubber preform.

[0011] The above rubber preform is placed on a two-roll mill and subjected to a thin-pass treatment at a second preset temperature to obtain a compound rubber;

[0012] The above-mentioned rubber compound is placed on a vulcanizing machine and vulcanized at a third preset temperature to obtain vulcanized rubber with self-healing and recyclable properties.

[0013] As another aspect of this disclosure, an application of the above-described vulcanized rubber is provided, the vulcanized rubber being the vulcanized rubber in the above embodiments, the application including self-healing and recycling.

[0014] Based on the above technical solution, the vulcanized rubber with self-healing and recyclable properties, its preparation method, and its application provided in this disclosure have one of the following beneficial effects:

[0015] (1) In the embodiments of this disclosure, sulfur undergoes ring-opening in the presence of a nucleophilic catalyst (first catalyst), while the sulfur-sulfur bonds in the disulfide are opened by heating, generating a copolymer of sulfur and a sulfur-containing disulfide via a free radical reaction. This copolymer forms ion pairs under the action of a nucleophilic catalyst (second catalyst) and generates sulfur free radicals. These sulfur free radicals are used to vulcanize the rubber, generating a vulcanized rubber with a three-dimensional network structure. This vulcanized rubber exhibits high crosslinking density and high tensile strength. Furthermore, the sulfur free radicals can be captured by carbon black, causing the carbon black to form covalent bonds on the rubber backbone, enhancing the dispersion of carbon black in the rubber matrix, thereby contributing to obtaining a vulcanized rubber with high crosslinking degree and high mechanical properties. Meanwhile, the zinc oxide used in the vulcanization process provided in this disclosure mainly serves as a filler to enhance the mechanical properties of the vulcanized rubber and does not participate in the vulcanization reaction. In other words, this disclosure does not use traditional vulcanizing agents and avoids the use of toxic rubber accelerators, making it an environmentally friendly vulcanized rubber processing technology.

[0016] (2) In the embodiments of this disclosure, the sulfur-sulfur bond exchange reaction within the vulcanized rubber provided by this disclosure is dynamically reversible. When the cross-sections of the vulcanized rubber come into contact with each other, and are heated in air, the sulfur-sulfur bonds within the rubber can undergo an exchange reaction under the action of a second catalyst. This causes the network structure at the rubber cross-section to be broken, molecules to diffuse, re-entangle, and cross-link to form a new dynamic network structure. This dynamic network structure rejoins the cross-sections together, thus allowing the broken vulcanized rubber to be repaired and recycled. Therefore, the vulcanized rubber prepared using the formulation provided by this disclosure has multiple repair and recycling properties, which can effectively extend the service life of industrial vulcanized rubber and solve the pollution problem of vulcanized rubber waste. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the mechanism by which disulfides containing sulfur bonds and sulfur undergo copolymerization to form copolymers in the embodiments of this disclosure;

[0018] Figure 2 This is a schematic diagram of the vulcanization mechanism for forming vulcanized rubber with self-healing and recyclable properties in the embodiments of this disclosure;

[0019] Figure 3 This is a schematic diagram of the repair mechanism of vulcanized rubber with self-healing and recyclable properties in the embodiments of this disclosure. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0021] Currently, although vulcanized rubber possesses excellent mechanical properties, the irreversibility of its three-dimensional cross-linked network makes reprocessing and recycling extremely difficult, while also causing environmental pollution. Vulcanization and cross-linking are prerequisites for achieving excellent mechanical properties in rubber; however, this also implies irreversible chemical bonds between rubber segments, further hindering the reprocessing and recycling of rubber materials.

[0022] In related technologies, intrinsically self-healing materials utilize the dynamic bonds inherent in the material itself to achieve a repair effect. In this case, the repair reaction can be carried out effectively multiple times. The formation of this reversible dynamic bond not only helps repair mechanical damage but also opens up new avenues for the remodeling and recycling of cross-linked polymer products. For example, by adding a metal salt catalyst to a vulcanized rubber system to catalyze the dynamic reversible exchange reaction of disulfide bonds, the rubber can acquire self-healing capabilities. The reaction mechanism mainly manifests as follows: utilizing the lone pair electrons of sulfur atoms in disulfides, the disulfide and the metal salt catalyst immediately form a complex after mixing. Subsequently, by adjusting the bond angle and bond length between the disulfide and the metal salt catalyst, the spatial conformation of the complex intermediate is optimized, forming a transition state. Finally, the electron rearrangement and localization of disulfide bonds cause the disulfide bonds to break, providing metathesis products for the recombination of two different sulfur atoms. Although the vulcanized rubber in the above-mentioned related technologies has a certain self-healing function, it still mainly relies on the addition of toxic and harmful substances such as vulcanizing agents, accelerators, or antioxidants to prepare vulcanized rubber, and the vulcanized rubber prepared by this method still poses environmental pollution problems.

[0023] Therefore, the industry urgently needs a suitable vulcanized rubber that can be self-healing and recyclable, and achieve the goals of being environmentally friendly and having a long shelf life, thereby resolving the contradictions in crosslinking strength, quality stability and environmental safety of vulcanized rubber.

[0024] Therefore, this disclosure proposes a vulcanized rubber with self-healing and recyclable properties, its preparation method and application. In the presence of a nucleophilic catalyst, sulfur undergoes ring-opening and copolymerization with certain sulfur-containing disulfides to form a copolymer. The free groups in the copolymer can promote the vulcanization of the rubber and effectively improve the crosslinking degree and mechanical properties of the rubber, especially in the presence of carbon black.

[0025] According to some embodiments of this disclosure, a vulcanized rubber with self-healing and recyclable properties is provided, with the following weight proportions: 100 parts of rubber, 1-10 parts of a copolymer obtained by copolymerization of sulfur and a sulfur-containing disulfide in the presence of a first catalyst, 1-3 parts of a second catalyst, 1-3 parts of zinc oxide, 1-2 parts of an antioxidant, and 10-50 parts of carbon black.

[0026] Figure 1This is a schematic diagram illustrating the mechanism by which sulfur-containing disulfides and sulfur undergo copolymerization to form copolymers, as described in the embodiments of this disclosure. Figure 2 This is a schematic diagram of the vulcanization reaction mechanism for forming a vulcanized rubber with self-healing and recyclable properties in an embodiment of this disclosure. In the disulfide containing sulfur-sulfur bonds, R can be at least one of propyl, phenyl, salicylic acid group, and tetraethylthiuram.

[0027] The following combination Figure 1 and Figure 2 The formation mechanism of vulcanized rubber disclosed herein is explained in detail.

[0028] like Figure 1 As shown, the first catalyst is a nucleophile (Nu). Under the action of the first catalyst, the sulfur-sulfur bonds in sulfur open, and the ring-opened sulfur forms an ion pair with the nucleophilic first catalyst, providing lone pairs of electrons. At the same time, the disulfide containing sulfur-sulfur bonds undergoes ring-opening under heating, simultaneously forming lone pairs of electrons. Then, the two react via free radicals to form a copolymer of sulfur and the disulfide containing sulfur-sulfur bonds. The copolymer formed by the copolymerization reaction of sulfur and the disulfide containing sulfur-sulfur bonds, rubber, the second catalyst (nucleophile (Nu)), zinc oxide, antioxidant, and carbon black are mixed and vulcanized to form vulcanized rubber. In this process, under the action of a second catalyst, the sulfur-sulfur bonds in the copolymer undergo ring-opening upon heating (at a temperature of 135-150℃), forming ion pairs and generating sulfur free radicals. These sulfur free radicals are used to vulcanize the rubber. Simultaneously, the sulfur free radicals are captured by carbon black, causing the carbon black to form covalent bonds on the rubber backbone, enhancing the dispersion of carbon black in the rubber matrix. This contributes to obtaining vulcanized rubber with high crosslinking degree and high mechanical properties. Zinc oxide is added to this system as a filler, which does not participate in the vulcanization reaction. It can further enhance the mechanical properties of the vulcanized rubber and is very environmentally friendly. In addition, the vulcanized rubber provided in this disclosure reduces the use of activators and accelerators such as zinc oxide and stearic acid, making it an environmentally friendly vulcanized rubber.

[0029] In the embodiments of this disclosure, the copolymer obtained by copolymerizing sulfur and disulfide containing sulfur bonds is 1-10 parts, preferably 5 parts. If it is less than 1 part, the crosslinking density of the rubber is low and the tensile strength of the vulcanized rubber is low. If it is more than 10 parts, the crosslinking density of the rubber is high, which will lead to the elongation at break of the rubber being too low, which is not conducive to the further use and application of the vulcanized rubber.

[0030] Preferably, the mass ratio of sulfur, sulfur-containing disulfide, and the first catalyst is 30%-70%:10%-50%:1%-10%, wherein the total mass of sulfur, sulfur-containing disulfide, and the first catalyst is 100%. The amount of sulfur used should be at least twice that of the disulfide. If the amount of sulfur is too small, the sulfur-sulfide bonds cannot be fully opened, and therefore sufficient sulfur free radicals cannot be generated for the vulcanization of the rubber, further affecting the crosslinking effect of the vulcanized rubber. The preparation process of the copolymer of sulfur and sulfur-containing disulfide is simple, and the raw materials are readily available.

[0031] Preferably, the disulfide containing sulfur-sulfur bonds described above has the structural formula shown in formula (I):

[0032]

[0033] In the disulfide containing a sulfur-sulfur bond, R can be at least one of propyl, phenyl, salicylic acid, and tetraethylthiuram, and the disulfide containing a sulfur-sulfur bond can be at least one of dipropyl disulfide, diphenyl disulfide, cystine, lipoic acid, dithiosalicylic acid, and tetraethylthiuram disulfide; wherein R can be at least one of propyl, phenyl, salicylic acid, and tetraethylthiuram.

[0034] In the embodiments of this disclosure, the first catalyst and the second catalyst may be the same or different, and may be independently selected from at least one of 4-dimethylaminopyridine, 1,8-diazobisspirocyclo[5.4.0]undec-7-ene, 1,5,7-triazidobiscyclo(4.4.0)dec-5-ene, N-methylimidazolium, and aniline.

[0035] In the embodiments of this disclosure, the sulfur-sulfur bond exchange reaction within the vulcanized rubber is dynamically reversible. Under the catalysis of a first catalyst, sulfur undergoes ring-opening, and simultaneously, the sulfur-sulfur bonds in the disulfide open upon heating, forming lone pairs of electrons, which then react via free radicals to generate a copolymer of sulfur and disulfide. Under the catalysis of a second catalyst, the copolymer forms ion pairs and generates sulfur free radicals. These sulfur free radicals react with the rubber through double bond reactions, thereby generating a cross-linked rubber with a three-dimensional network structure. This results in a vulcanized rubber with high cross-linking density and high tensile strength.

[0036] Preferably, the carbon black is at least one of carbon black N234, carbon black N330, and carbon black N660. During the preparation of vulcanized rubber, the carbon black captures sulfur free radicals and forms them on the main chain via covalent bonds, enhancing the dispersion of carbon black in the rubber matrix and contributing to further improvement of the mechanical properties of the vulcanized rubber.

[0037] Preferably, the rubber is at least one of natural rubber, polyisoprene rubber, polybutadiene rubber, and styrene-butadiene rubber.

[0038] Preferably, the antioxidant is at least one selected from 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N,N'-diphenyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine. The addition of the antioxidant can improve the stability of the rubber, delay rubber aging, and extend the service life of the rubber.

[0039] According to some embodiments of this disclosure, a method for preparing the vulcanized rubber as described above is also provided, comprising the following steps:

[0040] Rubber is added to an internal mixer and mixed at a first preset temperature.

[0041] A copolymer obtained by copolymerization of sulfur and sulfur-containing disulfide in the presence of a first catalyst and a second catalyst are added to an internal mixer and the mixture is internally mixed at a first preset temperature.

[0042] Zinc oxide and antioxidant are added sequentially to a mixer and mixed at a first preset temperature to obtain a rubber preform.

[0043] The above rubber preform is placed on a two-roll mill and subjected to a thin-pass treatment at a second preset temperature to obtain a compound rubber;

[0044] The above-mentioned rubber compound is placed on a vulcanizing machine and vulcanized at a third preset temperature to obtain vulcanized rubber with self-healing and recyclable properties.

[0045] In the embodiments of this disclosure, a copolymer is obtained by reacting sulfur, which is most commonly used in vulcanization rubber processes, with a sulfur-containing disulfide. Using this copolymer as a crosslinking agent for vulcanized rubber enables the prepared vulcanized rubber to have a high crosslinking density and high tensile strength. Furthermore, the preparation process of this disulfide-sulfur copolymer is simple, and the resulting vulcanized rubber has broad industrial application prospects. The vulcanization process of this disclosure reduces the use of the rubber activator zinc oxide and avoids the use of traditional toxic rubber accelerators, making it an environmentally friendly vulcanization rubber processing technology.

[0046] Preferably, the preparation temperature of the vulcanized rubber can be, for example:

[0047] The first preset temperature is 65℃-75℃, such as 68℃, 72℃, etc.

[0048] The second preset temperature is 55℃-65℃, such as 58℃, 62℃, etc.

[0049] The third preset temperature is 135℃-150℃, such as 138℃, 142℃, 145℃, etc.

[0050] According to some embodiments of this disclosure, an application of the vulcanized rubber described above in the fields of self-healing and recycling is also provided.

[0051] Figure 3 This is a schematic diagram of the repair mechanism of vulcanized rubber with self-healing and recyclable properties in the embodiments of this disclosure.

[0052] like Figure 3 As shown, when the two cross-sections of the vulcanized rubber come into contact with each other under the action of the second catalyst, the sulfur-sulfur bonds at the cross-sections are opened, broken and metathesis reaction occurs when heated at 80℃-140℃. The opened sulfur-sulfur bonds can cause the polymer network structure to unwrap and recombine at the interface, thereby forming a new dynamic network structure that rejoins the cross-sections together, thus achieving crack repair and sample recycling.

[0053] Preferably, the self-healing method includes: contacting the cross-sections of the above-mentioned vulcanized rubber in air at 80℃-140℃ for 1-24 hours to repair them; the recycling method includes: crushing and sieving the above-mentioned vulcanized rubber, and molding it at 80℃-140℃ for 1-24 hours.

[0054] In the embodiments of this disclosure, the vulcanized rubber prepared by utilizing the dynamic reversibility of the sulfur-sulfur bond exchange reaction within the vulcanized rubber has multiple repair and recycling properties, thereby effectively extending the service life of industrial vulcanized rubber and solving the pollution problem of vulcanized rubber waste.

[0055] The present disclosure is further illustrated below through comparative examples, embodiments, and related test experiments. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict.

[0056] Example 1

[0057] The preparation method of the copolymer of diphenyl disulfide and sulfur includes the following steps:

[0058] 8g of sulfur was heated to 130℃ to melt it, and then 2g of diphenyl disulfide and 0.1g of 4-dimethylaminopyridine were added and reacted for 3 hours to obtain a copolymer of diphenyl disulfide and sulfur as shown in formula (I1).

[0059]

[0060] In Example 1 of this disclosure, the raw material mixing formula of the vulcanized rubber composite material with intrinsic self-healing and recyclability is composed of the following parts by weight: 100 parts of polyisoprene rubber, 5 parts of copolymer of diphenyl disulfide and sulfur, 2 parts of 4-dimethylaminopyridine, 2 parts of zinc oxide, 1 part of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, and 50 parts of carbon black.

[0061] The specific process for preparing vulcanized rubber composite materials with intrinsic self-healing and recyclability is as follows:

[0062] Weigh the raw materials according to the above mixing formula. Set the internal mixer temperature to 70℃ and the speed to 60 rpm. Then add the polyisoprene rubber to the internal mixer and mix for 3 minutes. Add the copolymer of diphenyl disulfide and sulfur and 4-dimethylaminopyridine and mix for 3 minutes. Add zinc oxide and 2,2,4-trimethyl-1,2-dihydroquinoline polymer in sequence and mix for 5 minutes. Add carbon black and mix for 8 minutes to obtain the final rubber compound. Finally, pass the compound through a two-roll mill at 60℃ several times and sheet it. Let it stand at room temperature for more than 24 hours. Vulcanize the compound on a flat vulcanizing machine at a vulcanizing temperature of 145℃ and a vulcanizing pressure of 10 MPa. After standing at room temperature for 24 hours, polyisoprene vulcanized rubber (original vulcanized rubber) is obtained.

[0063] In the embodiments of this disclosure, the mechanical properties of the obtained vulcanized rubber after self-healing and recycling, as well as the crosslinking density of the vulcanized rubber, are tested. The specific testing process is as follows:

[0064] The mechanical properties of the material are determined by tensile testing. After the tensile specimen breaks, the two cross-sections are brought into full contact and repaired in air at 100°C for 10 hours. The tensile properties of the material are then tested again.

[0065] Furthermore, the vulcanized rubber composite material is cut into small pieces, then mechanically pulverized under liquid nitrogen freezing, and sieved to obtain 60-100 mesh rubber microparticles. The rubber microparticles are then molded at 100℃ and 10MPa pressure for 5 hours to perform tensile property tests.

[0066] The crosslinking density test method includes the following steps: Take 0.3g of polyisoprene vulcanized rubber from Example 1, add 10ml of toluene and soak for 72h. After filtration, wipe off the solvent residue on the rubber surface with filter paper and weigh it. Then, put it into a vacuum drying oven to dry until constant weight, weigh it again, and then use the crosslinking density calculation formula to measure the crosslinking density.

[0067] The calculation process for crosslinking density is as follows:

[0068] Volume fraction:

[0069]

[0070] In the formula, m0 is the mass of the sample before swelling; m1 is the mass of the sample before drying; m2 is the mass of the sample after drying; Φ is the mass fraction of raw rubber in the vulcanized rubber; α is the mass loss of raw rubber during the swelling process; ρ r ρ is the density of rubber. s ρ is the density of the solvent.

[0071] Crosslinking density:

[0072]

[0073] In the formula, X is the interaction parameter of polyisoprene vulcanized rubber-toluene, which is 0.393; Vs is the molar volume of the solvent, which is 105.7 mL / mol.

[0074] The mechanical properties of the original vulcanizate, the self-healing vulcanizate, and the recycled vulcanizate, as well as the crosslinking density of the original vulcanizate, are shown in Table 1 in this embodiment.

[0075] Example 2

[0076] A method for preparing a copolymer of cystine and sulfur includes the following steps:

[0077] 8g of sulfur was heated to 130℃ to melt it, and then 2g of cystine and 0.1g of 1,8-diazobisspirocyclic[5.4.0]undecyl-7-ene were added and reacted for 3 hours to obtain a copolymer of cystine and sulfur as shown in formula (I2).

[0078]

[0079] In Example 2 of this disclosure, the raw material mixing formula of the vulcanized rubber composite material with intrinsic self-healing and recyclability is composed of the following parts by weight: 100 parts of polyisoprene rubber, 10 parts of copolymer of cystine and sulfur, 1 part of 1,8-diazobisspirocyclic[5.4.0]undec-7-ene, 2 parts of zinc oxide, 1 part of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, and 50 parts of carbon black.

[0080] The specific process for preparing vulcanized rubber composite materials with intrinsic self-healing and recyclability is as follows:

[0081] Weigh the raw materials according to the above compounding formula. Set the internal mixer temperature to 70℃ and the speed to 60 rpm. Then add the polyisoprene rubber to the internal mixer and mix for 3 minutes. Add the copolymer of cystine and sulfur and 1,8-diazobisspirocyclic [5.4.0]undec-7-ene and mix for 3 minutes. Add zinc oxide and 2,2,4-trimethyl-1,2-dihydroquinoline polymer in sequence and mix for 5 minutes. Add carbon black and mix for 8 minutes to obtain the final compound. Finally, pass the compound through a two-roll mill at 60℃ several times and sheet it. Let it stand at room temperature for more than 24 hours. Vulcanize the compound on a flat vulcanizing machine at a vulcanizing temperature of 145℃ and a vulcanizing pressure of 10 MPa. After standing at room temperature for 24 hours, the original vulcanized rubber is obtained.

[0082] In the embodiments of this disclosure, the mechanical properties of the obtained vulcanized rubber after self-healing and recycling, as well as the crosslinking density of the vulcanized rubber, are tested. The specific testing process is as follows:

[0083] The mechanical properties of the material are determined by tensile testing. After the tensile specimen breaks, the two cross-sections are brought into full contact and repaired in air at 100°C for 10 hours. The tensile properties of the material are then tested again.

[0084] Furthermore, the vulcanized rubber composite material is cut into small pieces, then mechanically pulverized under liquid nitrogen freezing, and sieved to obtain 60-100 mesh rubber microparticles. The rubber microparticles are then molded at 100℃ and 10MPa pressure for 5 hours to perform tensile property tests.

[0085] The crosslinking density test method includes the following steps: Take 0.3g of vulcanized rubber from Example 2, add 10ml of toluene and soak for 72h. After filtration, wipe off the solvent residue on the surface of the rubber with filter paper and weigh it. Then, put it into a vacuum drying oven to dry until constant weight and weigh it again. Then, the crosslinking density can be measured using the crosslinking density calculation formula (as shown in Example 1).

[0086] The mechanical properties of the original vulcanizate, the self-healing vulcanizate, and the recycled vulcanizate, as well as the crosslinking density of the original vulcanizate, are shown in Table 1 in this embodiment.

[0087] Example 3

[0088] The preparation method of the copolymer of lipoic acid and sulfur includes the following steps:

[0089] 9g of sulfur was heated to 130℃ to melt it, and then 1g of thioctic acid and 0.15g of 1,5,7-triazidobis(4.4.0)dec-5-ene were added and reacted for 3 hours to obtain a copolymer of thioctic acid and sulfur as shown in formula (13).

[0090]

[0091] In Example 3 of this disclosure, the raw material mixing formula of the vulcanized rubber composite material with intrinsic self-healing and recyclability is composed of the following parts by weight: 100 parts of polyisoprene rubber, 5 parts of copolymer of thioctic acid and sulfur, 1 part of 1,5,7-triazidobicyclo(4.4.0)dec-5-ene, 3 parts of zinc oxide, 1 part of 22,4-trimethyl-1,2-dihydroquinoline polymer, and 50 parts of carbon black.

[0092] The specific process for preparing vulcanized rubber composite materials with intrinsic self-healing and recyclability is as follows:

[0093] Weigh the raw materials according to the above compounding formula. Set the internal mixer temperature to 70℃ and the speed to 60 rpm. Then add the polyisoprene rubber to the internal mixer and mix for 3 minutes. Add the copolymer of thioctic acid and sulfur and 1,5,7-triazidobicyclo(4.4.0)dec-5-ene and mix for 3 minutes. Add zinc oxide and 2,2,4-trimethyl-1,2-dihydroquinoline polymer in sequence and mix for 5 minutes. Then add carbon black and mix for 8 minutes to obtain the final compound. Finally, pass the compound through a two-roll mill at 60℃ several times and sheet it. Let it stand at room temperature for more than 24 hours. Vulcanize the compound on a flat vulcanizing machine at a vulcanizing temperature of 145℃ and a vulcanizing pressure of 10 MPa. After standing at room temperature for 24 hours, the original vulcanized rubber is obtained.

[0094] In the embodiments of this disclosure, the mechanical properties of the obtained vulcanized rubber after self-healing and recycling, as well as the crosslinking density of the vulcanized rubber, are tested. The specific testing process is as follows:

[0095] The mechanical properties of the material are determined by tensile testing. After the tensile specimen breaks, the two cross-sections are brought into full contact and repaired in air at 100°C for 10 hours before the tensile properties of the material are tested again.

[0096] Furthermore, the vulcanized rubber composite material is cut into small pieces, then mechanically pulverized under liquid nitrogen freezing, and sieved to obtain 60-100 mesh rubber microparticles. The rubber microparticles are then molded at 100℃ and 10MPa pressure for 5 hours to perform tensile property tests.

[0097] The crosslinking density test method includes the following steps: Take 0.3g of vulcanized rubber from Example 3, add 10ml of toluene and soak for 72h. After filtration, wipe off the solvent residue on the surface of the rubber with filter paper and weigh it. Then, put it into a vacuum drying oven to dry until constant weight and weigh it again. Then, the crosslinking density can be measured using the crosslinking density calculation formula (as shown in Example 1).

[0098] The mechanical properties of the original vulcanizate, the self-healing vulcanizate, and the recycled vulcanizate, as well as the crosslinking density of the original vulcanizate, are shown in Table 1 in this embodiment.

[0099] Example 4

[0100] The preparation method of the copolymer of dithiosalicylic acid and sulfur includes the following steps:

[0101] 7g of sulfur was heated to 130℃ to melt it, and then 3g of dithiosalicylic acid and 0.15g of 1,5,7-triazidobiscyclo(4.4.0)dec-5-ene were added and reacted for 3 hours to obtain a copolymer of dithiosalicylic acid and sulfur as shown in formula (I4).

[0102]

[0103] In Example 4 of this disclosure, the raw material mixing formula of the vulcanized rubber composite material with intrinsic self-healing and recyclability is composed of the following parts by weight: 100 parts of polyisoprene rubber, 5 parts of copolymer of dithiosalicylic acid and sulfur, 2 parts of 1,5,7-triazidobicyclo(4.4.0)dec-5-ene, 2 parts of zinc oxide, 1 part of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, and 50 parts of carbon black.

[0104] The specific process for preparing vulcanized rubber composite materials with intrinsic self-healing and recyclability is as follows:

[0105] Weigh the raw materials according to the above compounding formula. Set the internal mixer temperature to 70℃ and the speed to 60 rpm. Then, add the polyisoprene rubber to the internal mixer and mix for 3 minutes. Add the copolymer of dithiosalicylic acid and sulfur and 1,5,7-triazidobicyclo(4.4.0)dec-5-ene and mix for 3 minutes. Then, add zinc oxide and 2,2,4-trimethyl-1,2-dihydroquinoline polymer and mix for 5 minutes. Finally, add carbon black and mix for 8 minutes to obtain the final compound. Finally, pass the compound through a two-roll mill at 60℃ several times and sheet it. Let it stand at room temperature for more than 24 hours. Vulcanize the compound on a flat vulcanizing machine at a vulcanizing temperature of 145℃ and a vulcanizing pressure of 10 MPa. After standing at room temperature for 24 hours, the original vulcanized rubber is obtained.

[0106] In the embodiments of this disclosure, the mechanical properties of the obtained vulcanized rubber after self-healing and recycling, as well as the crosslinking density of the vulcanized rubber, are tested. The specific testing process is as follows:

[0107] The mechanical properties of the material are determined by tensile testing. After the tensile specimen breaks, the two cross-sections are brought into full contact and repaired in air at 100°C for 10 hours. The tensile properties of the material are then tested again.

[0108] Furthermore, the vulcanized rubber composite material is cut into small pieces, then mechanically pulverized under liquid nitrogen freezing, and sieved to obtain 60-100 mesh rubber microparticles. The rubber microparticles are then molded at 100℃ and 10MPa pressure for 5 hours to perform tensile property tests.

[0109] The crosslinking density test method includes the following steps: Take 0.3g of vulcanized rubber from Example 4, add 10ml of toluene and soak for 72h. After filtration, wipe the solvent residue on the surface of the rubber with filter paper and weigh it. Then, put it into a vacuum drying oven to dry until constant weight and weigh it again. Then, the crosslinking density can be measured using the crosslinking density calculation formula (as shown in Example 1).

[0110] The mechanical properties of the original vulcanizate, the self-healing vulcanizate, and the recycled vulcanizate, as well as the crosslinking density of the original vulcanizate, are shown in Table 1 in this embodiment.

[0111] Example 5

[0112] The preparation method of the copolymer of dipropyl disulfide and sulfur includes the following steps:

[0113] 7g of sulfur was heated to 130℃ to melt it, and then 3g of dipropyl disulfide and 0.2g of N-methylimidazole were added and reacted for 3 hours to obtain a copolymer of dipropyl disulfide and sulfur as shown in formula (I5).

[0114]

[0115] In Embodiment 5 of this disclosure, the raw material mixing formula of the vulcanized rubber composite material with intrinsic self-healing and recyclability is composed of the following parts by weight: 100 parts of polyisoprene rubber, 5 parts of a copolymer of dipropyl disulfide and sulfur, 3 parts of N-methylimidazolium, 3 parts of zinc oxide, 1 part of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, and 50 parts of carbon black.

[0116] The specific process for preparing vulcanized rubber composite materials with intrinsic self-healing and recyclability is as follows:

[0117] Weigh the raw materials according to the above mixing formula. Set the internal mixer temperature to 70℃ and the speed to 60 rpm. Then, add the polyisoprene rubber to the internal mixer and mix for 3 minutes. Add the copolymer of dipropyl disulfide and sulfur and N-methylimidazol and mix for 3 minutes. Then, add zinc oxide and 2,2,4-trimethyl-1,2-dihydroquinoline polymer and mix for 5 minutes. Finally, add carbon black and mix for 8 minutes to obtain the final rubber compound. Finally, pass the compound through a two-roll mill at 60℃ several times and sheet it. Let it stand at room temperature for at least 24 hours. Vulcanize the compound on a flat vulcanizing machine at a vulcanizing temperature of 145℃ and a vulcanizing pressure of 10 MPa. After standing at room temperature for 24 hours, the raw vulcanized rubber is obtained.

[0118] In the embodiments of this disclosure, the mechanical properties of the obtained vulcanized rubber after self-healing and recycling, as well as the crosslinking density of the vulcanized rubber, are tested. The specific testing process is as follows:

[0119] The mechanical properties of the material are determined by tensile testing. After the tensile specimen breaks, the two cross-sections are brought into full contact and repaired in air at 100°C for 10 hours. The tensile properties of the material are then tested again.

[0120] Furthermore, the vulcanized rubber composite material is cut into small pieces, then mechanically pulverized under liquid nitrogen freezing, and sieved to obtain 60-100 mesh rubber microparticles. The rubber microparticles are then molded at 100℃ and 10MPa pressure for 5 hours to perform tensile property tests.

[0121] The crosslinking density test method includes the following steps: Take 0.3g of vulcanized rubber from Example 5, add 10ml of toluene and soak for 72h. After filtration, wipe off the solvent residue on the surface of the rubber with filter paper and weigh it. Then, put it into a vacuum drying oven to dry until constant weight and weigh it again. Then, the crosslinking density can be measured using the crosslinking density calculation formula (as shown in Example 1).

[0122] The mechanical properties of the original vulcanizate, the self-healing vulcanizate, and the recycled vulcanizate, as well as the crosslinking density of the original vulcanizate, are shown in Table 1 in this embodiment.

[0123] Example 6

[0124] The preparation method of the copolymer of lipoic acid and sulfur includes the following steps:

[0125] 8g of sulfur was heated to 130℃ to melt it, and then 2g of thioctic acid and 0.15g of 4-dimethylaminopyridine were added and reacted for 3 hours to obtain a copolymer of thioctic acid and sulfur as shown in formula (I6).

[0126]

[0127] In Embodiment 6 of this disclosure, the raw material mixing formula of the vulcanized rubber composite material with intrinsic self-healing and recyclability is composed of the following parts by weight: 100 parts of polyisoprene rubber, 5 parts of copolymer of thioctic acid and sulfur, 2 parts of 4-dimethylaminopyridine, 2 parts of zinc oxide, 1 part of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, and 50 parts of carbon black.

[0128] The specific process for preparing vulcanized rubber composite materials with intrinsic self-healing and recyclability is as follows:

[0129] Weigh the raw materials according to the above compounding formula. Set the internal mixer temperature to 70℃ and the speed to 60 rpm. Then, add the polyisoprene rubber to the internal mixer and mix for 3 minutes. Add the copolymer of thioctic acid and sulfur and 4-dimethylaminopyridine and mix for 3 minutes. Then, add zinc oxide and 224-trimethyl-1,2-dihydroquinoline polymer and mix for 5 minutes. Finally, add carbon black and mix for 8 minutes to obtain the final compound. Finally, pass the compound through a two-roll mill at 60℃ several times and sheet it. Let it stand at room temperature for at least 24 hours. Vulcanize the compound on a flat vulcanizing machine at a vulcanizing temperature of 145℃ and a vulcanizing pressure of 10 MPa. After standing at room temperature for 24 hours, the original vulcanized rubber is obtained.

[0130] In the embodiments of this disclosure, the mechanical properties of the obtained vulcanized rubber after self-healing and recycling, as well as the crosslinking density of the vulcanized rubber, are tested. The specific testing process is as follows:

[0131] The mechanical properties of the material are determined by tensile testing. After the tensile specimen breaks, the two cross-sections are brought into full contact and repaired in air at 100°C for 10 hours. The tensile properties of the material are then tested again.

[0132] Furthermore, the vulcanized rubber composite material is cut into small pieces, then mechanically pulverized under liquid nitrogen freezing, and sieved to obtain 60-100 mesh rubber microparticles. The rubber microparticles are then molded at 100℃ and 10MPa pressure for 5 hours to perform tensile property tests.

[0133] The crosslinking density test method includes the following steps: Take 0.3g of vulcanized rubber from Example 6, add 10ml of toluene and soak for 72h. After filtration, wipe the solvent residue on the surface of the rubber with filter paper and weigh it. Then, put it into a vacuum drying oven to dry until constant weight and weigh it again. Then, the crosslinking density can be measured using the crosslinking density calculation formula (as shown in Example 1).

[0134] The mechanical properties of the original vulcanizate, the self-healing vulcanizate, and the recycled vulcanizate, as well as the crosslinking density of the original vulcanizate, are shown in Table 1 in this embodiment.

[0135] Example 7

[0136] The preparation method of the copolymer of lipoic acid and sulfur includes the following steps:

[0137] 8g of sulfur was heated to 130°C to melt it, and then 2g of lipoic acid and 0.15g of 4-dimethylaminopyridine were added and reacted for 3 hours to obtain a copolymer of lipoic acid and sulfur with the structure shown in formula (I6) in Example 6.

[0138] In Embodiment 7 of this disclosure, the raw material mixing formula of the vulcanized rubber composite material with intrinsic self-healing and recyclability is composed of the following parts by weight: 100 parts of polyisoprene rubber, 10 parts of copolymer of thioctic acid and sulfur, 2 parts of 4-dimethylaminopyridine, 2 parts of zinc oxide, 1 part of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, and 50 parts of carbon black.

[0139] The specific process for preparing vulcanized rubber composite materials with intrinsic self-healing and recyclability is as follows:

[0140] Weigh the raw materials according to the above compounding formula. Set the internal mixer temperature to 70℃ and the speed to 60 rpm. Then add the polyisoprene rubber to the internal mixer and mix for 3 minutes. Add the copolymer of thioctic acid and sulfur and 4-dimethylaminopyridine and mix for 3 minutes. Then add zinc oxide and 2,2,4-trimethyl-1,2-dihydroquinoline polymer and mix for 5 minutes. Add carbon black and mix for 8 minutes to obtain the final compound. Finally, pass the compound through a two-roll mill at 60℃ several times and sheet it. Let it stand at room temperature for more than 24 hours. Vulcanize the compound on a flat vulcanizing machine at a vulcanizing temperature of 145℃ and a vulcanizing pressure of 10 MPa. After standing at room temperature for 24 hours, the original vulcanized rubber is obtained.

[0141] In the embodiments of this disclosure, the mechanical properties of the obtained vulcanized rubber after self-healing and recycling, as well as the crosslinking density of the vulcanized rubber, are tested. The specific testing process is as follows:

[0142] The mechanical properties of the material are determined by tensile testing. After the tensile specimen breaks, the two cross-sections are brought into full contact and repaired in air at 100°C for 10 hours. The tensile properties of the material are then tested again.

[0143] Furthermore, the vulcanized rubber composite material is cut into small pieces, then mechanically pulverized under liquid nitrogen freezing, and sieved to obtain 60-100 mesh rubber microparticles. The rubber microparticles are then molded at 100℃ and 10MPa pressure for 5 hours to perform tensile property tests.

[0144] The crosslinking density test method includes the following steps: Take 0.3g of vulcanized rubber from Example 7, add 10ml of toluene and soak for 72h. After filtration, wipe off the solvent residue on the surface of the rubber with filter paper and weigh it. Then, put it into a vacuum drying oven to dry until constant weight and weigh it again. Then, the crosslinking density can be measured using the crosslinking density calculation formula (as shown in Example 1).

[0145] The mechanical properties of the original vulcanizate, the self-healing vulcanizate, and the recycled vulcanizate, as well as the crosslinking density of the original vulcanizate, are shown in Table 1 in this embodiment.

[0146] Comparative Example 1

[0147] The raw material formula is composed of the following parts by weight: 100 parts polyisoprene rubber, 2 parts stearic acid, 5 parts zinc oxide, 1 part 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 0.7 parts N-tert-butyl-2-benzothiazole sulfenamide, 2.5 parts sulfur, and 50 parts carbon black.

[0148] The traditional vulcanization process for preparing vulcanized rubber includes the following steps:

[0149] Weigh out each component raw material according to the mixing formula. Set the internal mixer temperature to 70℃ and the speed to 60 rpm, then add polyisoprene rubber to the internal mixer and mix for 3 minutes; add stearic acid and mix for 3 minutes, then add zinc oxide, 224-trimethyl-1,2-dihydroquinoline polymer, sulfur, and N-tert-butyl-2-benzothiazole sulfenamide sequentially and mix for 5 minutes; then add carbon black and mix for 8 minutes to obtain the final rubber compound. Finally, pass the compound through a two-roll mill at 60℃ several times and sheet it out, then let it stand at room temperature for at least 24 hours. Vulcanize the compound on a flat vulcanizing machine at a vulcanizing temperature of 145℃ and a vulcanizing pressure of 10 MPa, and let it stand at room temperature for 24 hours to obtain the original vulcanized rubber.

[0150] In the comparative examples disclosed herein, the mechanical properties of the obtained vulcanized rubber after self-healing and recycling, as well as the crosslinking density of the vulcanized rubber, were tested. The specific testing procedures are as follows:

[0151] The mechanical properties of the material are determined by tensile testing. After the tensile specimen breaks, the two cross-sections are brought into full contact and repaired in air at 100°C for 10 hours. The tensile properties of the material are then tested again.

[0152] Furthermore, the vulcanized rubber composite material is cut into small pieces, then mechanically pulverized under liquid nitrogen freezing, and sieved to obtain 60-100 mesh rubber microparticles. The rubber microparticles are then molded at 100℃ and 10MPa pressure for 5 hours to perform tensile property tests.

[0153] The crosslinking density test method includes the following steps: Take 0.3g of vulcanized rubber from Comparative Example 1, add 10ml of toluene and soak for 72h. After filtration, wipe off the solvent residue on the rubber surface with filter paper and weigh it. Then, place it in a vacuum drying oven to dry until constant weight and weigh it again. The crosslinking density can be measured using the crosslinking density calculation formula (as shown in Example 1).

[0154] The mechanical properties of the original vulcanizate, the self-healing vulcanizate, and the recycled vulcanizate in this comparative example, as well as the crosslinking density of the original vulcanizate, are shown in Table 1.

[0155] Table 1. Performance comparison of original vulcanizates, self-healing vulcanizates, and recycled vulcanizates in the examples and comparative examples.

[0156]

[0157]

[0158] As shown in Table 1, the vulcanized rubber prepared by the conventional vulcanization method in Comparative Example 1 lacks self-healing and recyclability, has a lower crosslinking density, and exhibits inferior mechanical properties compared to Examples 1-7. In Examples 1-7, the use of different disulfides and catalysts significantly improved the mechanical properties, self-healing properties, and recyclability of the vulcanized rubber compared to Comparative Example 1. In particular, compared to Example 6, Example 7 incorporated 10 parts of a copolymer of sulfur and a sulfur-containing disulfide, resulting in improved tensile strength, 300% elongation at break, and crosslinking density, while reducing elongation at break.

[0159] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A vulcanized rubber with self-healing and recyclable properties, characterized in that, The vulcanized rubber is formulated in the following proportions by weight: 100 parts of rubber; Sulfur and sulfur-containing disulfides in the presence of a first catalyst, 1-10 parts of copolymer obtained by copolymerization reaction; 1-3 parts of the second catalyst; 1-3 parts zinc oxide; Anti-aging agent 1-2 parts; 10-50 parts carbon black; The sulfur-containing disulfide includes at least one of the following: Dipropyl disulfide, diphenyl disulfide, cystine, lipoic acid, dithiosalicylic acid, tetraethylthiuram disulfide; The first catalyst and the second catalyst are the same or different nucleophilic catalysts, each independently selected from at least one of the following: 4-Dimethylaminopyridine, 1,8-diazobisspirocyclic [5.4.0]undec-7-ene, 1,5,7-triazidobiscyclo(4.4.0)dec-5-ene, N-methylimidazolium, aniline.

2. The vulcanized rubber according to claim 1, characterized in that, The mass ratio of sulfur, sulfur-containing disulfide, and the first catalyst is 30%~70%: 10%~50%: 1%~10%, and the total mass of sulfur, sulfur-containing disulfide, and the first catalyst is 100%.

3. The vulcanized rubber according to claim 1, characterized in that, The rubber includes at least one of the following: Natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber.

4. The vulcanized rubber according to claim 1, characterized in that, The antioxidant includes at least one of the following: 2,2,4-Trimethyl-1,2-dihydroquinoline polymer, N,N'-diphenyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine.

5. The vulcanized rubber according to claim 1, characterized in that, The carbon black includes at least one of the following: Carbon black N234, carbon black N330, carbon black N660.

6. A method for preparing vulcanized rubber according to any one of claims 1-5, characterized in that, include: Rubber is added to an internal mixer and mixed at a first preset temperature. A copolymer obtained by copolymerization of sulfur and sulfur-containing disulfide in the presence of a first catalyst and a second catalyst are added to an internal mixer and internally mixed at a first preset temperature. Zinc oxide and antioxidant are added to a mixer in sequence and mixed at a first preset temperature. Then carbon black is added and mixed again to obtain a rubber preform. The rubber preform is placed on a two-roll mill and subjected to a thin-pass treatment at a second preset temperature to obtain a compound rubber; The compound is placed on a vulcanizing machine and vulcanized at a third preset temperature to obtain vulcanized rubber with self-healing and recyclable properties.

7. The method according to claim 6, characterized in that, The first preset temperature is 65℃-75℃; The second preset temperature is 55℃-65℃; The third preset temperature is 135℃-150℃.

8. A self-healing method for vulcanized rubber according to any one of claims 1-5, characterized in that, The self-healing method is as follows: in air, at a temperature of 80℃-140℃, the cross-sections of the vulcanized rubber are brought into contact and repaired for 1-24 hours.

9. A method for recycling and reusing vulcanized rubber according to any one of claims 1-5, characterized in that, The recycling method is as follows: the vulcanized rubber is crushed, sieved, and molded at 80℃-140℃ for 1-24 hours.

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