Simplified preparation process of high tear strength graphene modified natural rubber based on interpenetrating double crosslinking network structure constructed by double vulcanizing agent

Abstract

This invention belongs to the technical field of graphene and functional rubber composites, specifically a simplified preparation process for high tear strength graphene-modified natural rubber based on an interpenetrating double crosslinked network structure constructed with two vulcanizing agents. This invention uses two vulcanizing agents: sulfur and peroxide. Sulfur rapidly forms a high-density carbon-sulfur crosslinked network (-C-Sx-C-) in the natural rubber composite, constituting the mechanical load-bearing skeleton between the natural rubber main chains, imparting high tear strength and fatigue resistance. Peroxide has a relatively slow vulcanization rate, and it slowly decomposes at lower temperatures to generate free radicals, constructing a stable -C-C- secondary crosslinked network between the terminal segments of the carbon-sulfur main network outside the sulfur vulcanization skeleton network. This improves the three-dimensional structural integrity of the vulcanization network, reduces the loss modulus of the rubber, and thus reduces heat generation during dynamic compression. This invention effectively improves the tear strength of natural rubber vulcanizates through the synergistic effect of nanofiller reinforcement and the interpenetrating double crosslinked network structure.

Description

Technical Field

[0001] This invention belongs to the technical field of graphene and functional rubber composite materials, specifically a simplified preparation process for high tear strength graphene-modified natural rubber based on an interpenetrating double crosslinked network structure constructed with a dual vulcanizing agent. Background Technology

[0002] As a strategic polymer material, natural rubber (NR) dominates key areas such as tire treads, industrial conveyor belts, and heavy equipment seals due to its high elasticity, high wear resistance, and dynamic fatigue properties. However, with the increasing trend towards extreme and lightweight modern equipment, the tear strength of traditional NR composites is gradually failing to meet requirements. For example, under high-speed dynamic loads on tires, tear failures caused by tread cracks propagating along stress concentration zones account for more than 60%; while longitudinal tearing problems in mining conveyor belts directly lead to downtime accidents and significant economic losses. The core of these problems lies in the limited tear strength of the NR matrix itself, and the fact that the single cross-linked network formed by traditional vulcanization is prone to microcrack proliferation due to local stress concentration, ultimately leading to macroscopic tearing.

[0003] Currently, improving the tear strength of rubber mainly focuses on two aspects: preventing crack propagation and reducing crack initiation. Preventing crack propagation commonly employs nanofiller reinforcement strategies. Nanofillers (such as graphene oxide (GO) and carbon nanotubes (CNTs)) possess large specific surface areas and abundant surface-active groups. When rubber molecular chains come into contact with them, they can be adsorbed onto the filler surface through physical interactions such as van der Waals forces and hydrogen bonds. This adsorption effect causes the rubber molecular chains to form a certain degree of constraint on the filler surface, creating an entangled structure that hinders crack propagation paths, thereby preventing crack propagation. However, in practical applications, the following bottlenecks exist: (1) uneven filler dispersion, which can become crack initiation points; (2) the crosslinking density and distribution range of a single vulcanization system are limited, making it difficult to construct multi-level energy dissipation mechanisms to resist tear propagation.

[0004] Interpenetrating double-crosslinked network structures are a polymer material design strategy. Their core characteristic is the interpenetration of two or more polymer networks through multiple crosslinking mechanisms, resulting in a synergistic reinforcement effect. Interpenetration refers to the interweaving of two or more independently crosslinked polymer networks at the molecular scale, forming a three-dimensional interpenetrating topology. The double crosslinking mechanism combines physical crosslinking (e.g., hydrogen bonds, van der Waals forces, crystalline domains) and chemical crosslinking (covalent bonds, dynamic bonds) or a combination of different chemical crosslinking systems within the network. Performance advantages mainly include: (1) Mechanical properties: High strength and high toughness are achieved through energy dissipation mechanisms (e.g., dynamic bond breaking and recombination) and network synergy. (2) Functional tunability: By controlling the crosslinking density, network ratio, and crosslinking type, materials can be endowed with self-healing, recyclability, or environmental responsiveness.

[0005] Synergistic reduction of crack initiation points through different types of crosslinking networks has become an important method for improving the tear strength of rubber composites. This involves preferentially forming one type of crosslinking network in natural rubber composites by utilizing the different crosslinking reaction rates of two or more vulcanizing agents, which serves as the mechanical support framework between the natural rubber backbone chains. Subsequently, the crosslinking network of another vulcanizing agent constructs a secondary crosslinking network outside the already formed primary network, filling in the defects of the primary network, such as unreacted sites on the backbone, and forming more crosslinking points at the branches. Ultimately, by improving the uniformity of the crosslinking network, crack initiation points and their propagation are reduced, forming a multi-level tear-resistant barrier, thereby effectively improving the tear strength of the rubber composite and extending its service life.

[0006] Natural rubber (NR) typically requires vulcanization during processing to improve stability and durability. Peroxide vulcanization is a commonly used method. The principle involves adding peroxide as a vulcanizing agent to the rubber. Upon heating, the peroxide releases active oxygen, promoting the formation of a stable carbon-carbon cross-linking network between rubber molecular chains, thus achieving vulcanization. Advantages of peroxide vulcanizates include: (1) excellent high-temperature resistance and good thermal stability; (2) low compression set and low creep; (3) outstanding resistance to reversion, suitable for long-term vulcanization processes. Disadvantages include: (1) mechanical strength (e.g., tear resistance) is generally lower than that of sulfur vulcanization systems; (2) poorer processing safety, requiring strict temperature control to prevent premature decomposition. Therefore, although peroxides play a role in the vulcanization process of NR, their slow reaction rate and limited use mean that traditional vulcanizing agents, such as sulfur or thioethers, are still the primary choice in practical applications. Summary of the Invention

[0007] To improve the tear strength of NR vulcanizates, this invention leverages the efficient synergy between nanofiller reinforcement and interpenetrating double crosslinked network structure. It simultaneously enhances the tear strength of NR vulcanizates by both preventing crack propagation and reducing crack initiation, breaking through the physical limits of traditional reinforcement strategies and providing a novel solution for next-generation high tear strength rubber composites.

[0008] This invention is achieved through the following technical solution: a simplified preparation process for high tear strength graphene-modified natural rubber based on an interpenetrating double crosslinked network structure constructed with a dual vulcanizing agent, comprising the following steps:

[0009] (1) A certain amount of deionized water was added to natural rubber latex at temperature T1, followed by a certain amount of graphene oxide aqueous dispersion. The stirring speed was v1 and the mechanical stirring time was t1. Then, a flocculant was added to flocculate the latex. The raw rubber obtained was washed and dehydrated multiple times, and then dried to constant weight at temperature T2 to obtain graphene oxide modified natural rubber masterbatch.

[0010] (2) The graphene oxide modified natural rubber masterbatch obtained in step (1) is placed in a mixer and mixed at a temperature of T3 for a time of t2 before the rubber compound is discharged. During this period, rubber additives and reinforcing fillers are added. The discharged rubber compound is cooled to room temperature and then mixed at a temperature of T4 for a time of t3 using a rolling mill. During this period, sulfur vulcanizing agent and peroxide are added in sequence and mixed evenly. The roller gap is reduced until the rubber compound is free of bubbles to obtain the compound.

[0011] (3) The compound rubber is placed at temperature T5 for time t4, and then vulcanized in a mold at temperature T6 and a certain pressure P1 for time t5. During the vulcanization process, the sulfur vulcanizing agent rapidly forms a carbon-sulfur bond crosslinking network with high crosslinking density -C-Sx-C- in the natural rubber composite material, which constitutes the mechanical load-bearing skeleton between the main chains of natural rubber, giving it high tear strength and fatigue resistance. The vulcanization rate of the peroxide is relatively slow. It slowly decomposes in the lower temperature region to generate free radicals, which build a stable -CC- crosslinking secondary crosslinking network between the end segments of the carbon-sulfur bond main network outside the sulfur vulcanization skeleton network, improve the three-dimensional structural integrity of the vulcanization network, reduce the loss modulus of the rubber, and thus reduce the heat generation during dynamic compression of the rubber. A high tear strength graphene modified natural rubber is obtained based on the interpenetrating double crosslinking network structure constructed by the dual vulcanizing agent.

[0012] As a further improvement to the technical solution of the present invention, the peroxide is selected from at least one of benzoyl peroxide, di-tert-butyl peroxide, tert-butyl perbenzoate, and diisopropyl peroxide.

[0013] As a further improvement to the technical solution of the present invention, in step (1), the temperature T1 is room temperature; the amount of deionized water added is to make the concentration of the prepared natural rubber latex emulsion 15-35 wt%; the stirring time t1 is 10-60 min, the stirring speed v1 is 100-1000 rad / min; and the drying temperature T2 of the raw rubber is 40-80℃.

[0014] As a further improvement to the technical solution of the present invention, in step (1), the concentration of the added graphene oxide dispersion is 1-10 mg / mL; the flocculant is selected from at least one of calcium chloride, formic acid, hydrochloric acid, sodium chloride and potassium chloride solution, and the concentration is 5-20 wt%; the mass ratio of natural rubber to graphene oxide in the obtained graphene oxide modified natural rubber masterbatch is 100:0.2-2.

[0015] As a further improvement to the technical solution of the present invention, in step (2), the mixing temperature T3 = 100-120℃, the mixing time t2 = 10-16min; the initial mixing temperature T4 = 50-70℃, the initial mixing time t3 = 10-15min.

[0016] As a further improvement to the technical solution of the present invention, in step (2), the rubber additive is composed of an antioxidant, an anti-aging agent, a vulcanization accelerator, an activator, and a softener in a mass ratio of 2:2:2:5:2; the mass ratio of natural rubber to reinforcing filler in the graphene oxide modified natural rubber masterbatch is 100:35.

[0017] As a further improvement to the technical solution of the present invention, the vulcanization accelerator is at least one selected from N-tert-butyl-2-benzothiazole sulfenamide, N-cyclohexyl-2-benzothiazole sulfenamide, and N-(diethylidene oxide)-2-benzothiazole sulfenamide; the antioxidant is at least one selected from 2,6-di-tert-butyl-4-methylphenol, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, and 2-thiol-benzoimidazole; and the antioxidant... The active ingredient is at least one of N-(1-methylisopentyl)-N'-phenyl-p-phenylenediamine and p-phenylaniline or dilauryl sulfide; the activator is at least one of zinc gluconate, zinc oxide and magnesium oxide; the softener is at least one of stearic acid, dibutyl titanate and dioctyl adipate; and the reinforcing filler is at least one of carbon black N110, N220, N330, N339, N375, N550, N660 and silica.

[0018] As a further improvement to the technical solution of the present invention, in step (2), the mass ratio of natural rubber to rubber additives in the graphene oxide modified natural rubber masterbatch is 100:8-15; the mass ratio of natural rubber to sulfur and peroxide in the graphene oxide modified natural rubber masterbatch is 100:0.5-4:0.5-4.

[0019] As a further improvement to the technical solution of the present invention, in step (3), T5 = room temperature, the rubber compound placement time t4 = 20-30h; the vulcanization temperature T6 = 140-160℃, the vulcanization pressure P1 = 10-20MPa, and the vulcanization time t5 = 5-15min.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention forms an entangled structure by adsorption between the functional groups on the surface of graphene oxide nanofiller and the rubber molecular chain, thereby preventing the crack propagation path and improving the tear strength.

[0022] (2) The present invention forms an interpenetrating double crosslinked network structure through two vulcanizing agents: sulfur has a relatively fast vulcanization rate and preferentially forms a high crosslinking density carbon-sulfur bond crosslinking network -C-Sx-C- in natural rubber composite material, which constitutes the mechanical load-bearing skeleton between the main chains of natural rubber, giving it high tear strength and fatigue resistance; peroxide has a relatively slow vulcanization rate and slowly decomposes in the lower temperature region to generate free radicals, which construct a stable -CC- crosslinking secondary crosslinking network between the end segments of the carbon-sulfur bond main network outside the sulfur vulcanization skeleton network, improve the three-dimensional structural integrity of the vulcanization network, reduce the loss modulus of rubber, and thus reduce the heat generation during dynamic compression of rubber.

[0023] (3) This invention enhances the tear strength of NR vulcanizate by combining the high efficiency of nanofiller reinforcement with the interpenetrating double cross-linked network structure, thereby improving the tear strength of NR vulcanizate from two aspects: preventing crack propagation and reducing crack source generation. This breaks through the physical limits of traditional reinforcement strategies and can provide a new solution for the next generation of high tear strength rubber composites.

[0024] (4) The preparation process of the present invention is simple, without strict requirements, and involves conventional equipment, making it easy to industrialize. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The Fourier transform infrared (FT-IR) spectra of the graphene-modified natural rubber (GO / NR) prepared in Examples 1-5 and Comparative Examples 1-3 of this invention are shown.

[0028] Figure 2 The vulcanization curves of GO / NR prepared in Examples 1-5 and Comparative Examples 1-3 of this invention are shown.

[0029] Figure 3 This is a schematic diagram of the mechanical behavior of GO / NR prepared in Examples 1-5 and Comparative Examples 1-3 of the present invention under tearing action. Detailed Implementation

[0030] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0031] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0032] This invention provides a specific embodiment of a simplified preparation process for high tear strength graphene-modified natural rubber with an interpenetrating double crosslinked network structure constructed based on a dual vulcanizing agent, comprising the following steps:

[0033] (1) A certain amount of deionized water was added to natural rubber latex at temperature T1, followed by a certain amount of graphene oxide aqueous dispersion. The stirring speed was v1 and the mechanical stirring time was t1. Then, a flocculant was added to flocculate the latex. The raw rubber obtained was washed and dehydrated multiple times, and then dried to constant weight at temperature T2 to obtain graphene oxide modified natural rubber masterbatch.

[0034] (2) The graphene oxide modified natural rubber masterbatch obtained in step (1) is placed in a mixer and mixed at a temperature of T3 for a time of t2 before the rubber compound is discharged. During this period, rubber additives and reinforcing fillers are added. The discharged rubber compound is cooled to room temperature and then mixed at a temperature of T4 for a time of t3 using a rolling mill. During this period, sulfur vulcanizing agent and peroxide are added in sequence and mixed evenly. The roller gap is reduced until the rubber compound is free of bubbles to obtain the compound.

[0035] (3) The compound rubber is placed at temperature T5 for time t4, and then vulcanized in a mold at temperature T6 and a certain pressure P1 for time t5. During the vulcanization process, the sulfur vulcanizing agent rapidly forms a carbon-sulfur bond crosslinking network with high crosslinking density -C-Sx-C- in the natural rubber composite material, which constitutes the mechanical load-bearing skeleton between the main chains of natural rubber, giving it high tear strength and fatigue resistance. The vulcanization rate of the peroxide is relatively slow. It slowly decomposes in the lower temperature region to generate free radicals, which build a stable -CC- crosslinking secondary crosslinking network between the end segments of the carbon-sulfur bond main network outside the sulfur vulcanization skeleton network, improve the three-dimensional structural integrity of the vulcanization network, reduce the loss modulus of the rubber, and thus reduce the heat generation during dynamic compression of the rubber. A high tear strength graphene modified natural rubber is obtained based on the interpenetrating double crosslinking network structure constructed by the dual vulcanizing agent.

[0036] In one example provided by the present invention, the peroxide is selected from at least one of benzoyl peroxide, di-tert-butyl peroxide, tert-butyl perbenzoate, and diisopropyl peroxide.

[0037] In another example provided by the present invention, in step (1), the temperature T1 is room temperature; the amount of deionized water added is to make the concentration of the prepared natural rubber latex emulsion 15-35 wt%; the stirring time t1 is 10-60 min, the stirring speed v1 is 100-1000 rad / min; and the drying temperature T2 of the raw rubber is 40-80℃.

[0038] In one example provided by the present invention, in step (1), the concentration of the added graphene oxide dispersion is 1 to 10 mg / mL; the flocculant is selected from at least one of calcium chloride, formic acid, hydrochloric acid, sodium chloride and potassium chloride solution, and the concentration is 5 to 20 wt%; the mass ratio of natural rubber to graphene oxide in the obtained graphene oxide modified natural rubber masterbatch is 100:0.2 to 2.

[0039] In another example provided by the present invention, in step (2), the mixing temperature T3 = 100-120℃, the mixing time t2 = 10-16min; the initial mixing temperature T4 = 50-70℃, the initial mixing time t3 = 10-15min.

[0040] In one example provided by the present invention, in step (2), the rubber additive is composed of an antioxidant, an anti-aging agent, a vulcanization accelerator, an activator, and a softener in a mass ratio of 2:2:2:5:2; the mass ratio of natural rubber to reinforcing filler in the graphene oxide modified natural rubber masterbatch is 100:35.

[0041] In another example provided by the present invention, the vulcanization accelerator is at least one of N-tert-butyl-2-benzothiazole sulfenamide, N-cyclohexyl-2-benzothiazole sulfenamide, and N-(diethylidene oxide)-2-benzothiazole sulfenamide; the antioxidant is at least one of 2,6-di-tert-butyl-4-methylphenol, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, and 2-thiol-benzoimidazole; the antioxidant is at least one of N-(1-methylisopentyl)-N'-phenyl-p-phenylenediamine and p-phenylaniline or dilauryl sulfide; the activator is at least one of zinc gluconate, zinc oxide, and magnesium oxide; the softener is at least one of stearic acid, dibutyl titanate, and dioctyl adipate; and the reinforcing filler is at least one of carbon black N110, N220, N330, N339, N375, N550, N660, and silica.

[0042] In one example provided by the present invention, in step (2), the mass ratio of natural rubber to rubber additives in the graphene oxide modified natural rubber masterbatch is 100:8-15; the mass ratio of natural rubber to sulfur and peroxide in the graphene oxide modified natural rubber masterbatch is 100:0.5-4:0.5-4.

[0043] In another example provided by the present invention, in step (3), T5 = room temperature, the compound standing time t4 = 20-30h; the vulcanization temperature T6 = 140-160℃, the vulcanization pressure P1 = 10-20MPa, and the vulcanization time t5 = 5-15min.

[0044] The technical solution of the present invention will be described in detail below through specific embodiments.

[0045] Example 1:

[0046] A high tear strength GO / NR structure based on a dual vulcanizing agent and a simplified preparation process, specifically including the following steps:

[0047] ① At room temperature (25℃), deionized water was added to the natural rubber latex, and the concentration was controlled at 30wt%. 2.5mg / mL of GO aqueous dispersion was added and mechanically stirred for 30min at a stirring speed of 500rad / min. 10wt% calcium chloride solution was added to flocculate the latex, wherein the volume ratio of natural rubber latex:GO aqueous dispersion:calcium chloride solution was 167:100:30. After the raw rubber was washed and dehydrated several times, it was dried at 60℃ to constant weight to obtain a modified NR masterbatch with a natural rubber:graphene oxide mass ratio of 100:0.5, namely GO / NR masterbatch.

[0048] ② Add the GO / NR masterbatch prepared in step ① with an NR content of 100 phr to a mixer at 110°C and mix for 4 min. Then add 2 phr of antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (4020), 2 phr of antioxidant 2,2,4-trimethyl-1,2-dihydroquinoline polymer (RD), and 2 phr of vulcanization accelerator N-cyclohexyl-2-benzothiazole sulfenamide (CZ). After mixing for 4 min, add 5 phr of activator zinc oxide and 2 phr of softener stearic acid and mix for 4 min. Then add 35 phr of N330 carbon black and discharge the rubber compound. After the discharged rubber compound is cooled to room temperature, it is mixed on a two-roll mill at 60°C for 10 min. During this time, add 1.5 phr of sulfur and 1 phr of benzoyl peroxide (BPO) in sequence. After mixing evenly, pass through a thin filter until the rubber compound is free of bubbles to obtain the compound.

[0049] ③ After the rubber compound has been left at room temperature for 24 hours, it is placed in a mold and subjected to a pressure of 15 MPa and a temperature of 150°C, according to t c90 Vulcanization 6 min (t) c90(Measured using a rubber processing analyzer); During the vulcanization process, the sulfur vulcanizing agent rapidly forms a high-density carbon-sulfur bond crosslinking network (-C-Sx-C-) in the natural rubber composite material, constituting the mechanical load-bearing skeleton between the main chains of natural rubber, thus imparting high tear strength and fatigue resistance; The peroxide has a relatively slow vulcanization rate, and it slowly decomposes in a lower temperature region to generate free radicals, constructing a stable -CC- crosslinking secondary crosslinking network between the terminal segments of the carbon-sulfur bond main network outside the sulfur vulcanization skeleton network, improving the three-dimensional structural integrity of the vulcanization network, reducing the loss modulus of the rubber, and thus reducing the heat generation during dynamic compression of the rubber; A high tear strength GO / NR is obtained based on the interpenetrating double crosslinking network structure constructed by the two vulcanizing agents.

[0050] Example 2:

[0051] Same as Example 1, except that the amount of BPO added is 2 phr.

[0052] Example 3:

[0053] Same as Example 1, except that the amount of BPO added is 3 phr.

[0054] Example 4:

[0055] Same as Example 1, except that the amount of sulfur added is 1 phr.

[0056] Example 5:

[0057] Same as Example 1, except that the amount of sulfur added is 2 phr.

[0058] Comparative Example 1:

[0059] A simplified preparation process for GO / NR based on a single vulcanizing agent is described. The specific steps are the same as in Example 1, except that BPO is not added and the amount of sulfur added is 1 phr.

[0060] Comparative Example 2:

[0061] Same as Example 1, except that BPO is not added and the amount of sulfur added is 1.5 phr.

[0062] Comparative Example 3:

[0063] Same as Example 1, except that BPO is not added and the amount of sulfur added is 2 phr.

[0064] The GO / NR composite materials obtained in Examples 1-5 and Comparative Examples 1-3 were subjected to performance tests. The tensile properties were tested according to GB / T 528-2009, with a tensile rate of 500 mm / min. The tear properties were tested according to GB / T 529-2008. The hardness was tested according to GB / T 531.1-2008. The crosslinking density was tested according to GB / T 533-2008. The heat generation properties were tested according to GB / T 1687.1-2016.

[0065] Depend on Figure 1 It can be seen that for the GO / NR composite materials with interpenetrating double crosslinked network structure prepared in Examples 1-5, 836-838 cm⁻¹ -1 The characteristic absorption peak at 836 cm⁻¹ corresponds to the out-of-plane bending vibration of the -C=C- bond in the cis-1,4-isoprene structure, and the intensity of this peak can serve as an important indicator of the degree of double bond reaction. For the GO / NR of the single sulfur crosslinking systems in Comparative Examples 1–3, the crosslinking reaction mainly involves the -C=C- double bond in the isoprene unit. FT-IR spectra showed that as the sulfur addition increased from 1 phr to 2 phr, the peak intensity increased. -1 The intensity of the -C=C- characteristic peak at this location exhibits a gradient decrease, indicating that sulfur radicals preferentially attack the double bond structure, thereby preferentially forming sulfur bonds (-CS). X -C-) crosslinked network. Furthermore, for Examples 1-5, after adding BPO as a crosslinking agent, 836 cm⁻¹ -1 The peak intensity remained stable at 1699 cm⁻¹, indicating that BPO's reaction with the double bond is relatively limited. After participating in the sulfidation reaction, BPO produces benzoic acid, whose C=O characteristic peak is at 1699 cm⁻¹. -1 The presence of sulfur and BPO further confirms that BPO can participate in the crosslinking reaction. Therefore, by simultaneously adding sulfur and BPO (S / BPO), a GO / NR composite material with an interpenetrating double crosslinked network structure can be obtained.

[0066] Depend on Figure 2 It can be seen that, compared with Comparative Examples 1 to 3, the crosslinking density of the rubber composite materials prepared in Examples 1 to 5 of the present invention has increased, but the increase is not large, indicating that the CC bonds formed by BPO crosslinking mainly supplement the carbon-sulfur crosslinking network; in addition, compared with Comparative Examples 1 to 3, the vulcanization curves of Examples 1 to 5 show a slower rate during the rapid vulcanization period, indicating that the crosslinking rate of BPO is relatively slow and mainly plays a supplementary role in the carbon-sulfur crosslinking network.

[0067] Figure 3 These figures illustrate the mechanical behavior of the GO / NR composites prepared in Examples 1-5 and Comparative Examples 1-3 under tearing conditions. These figures are drawn based on reasonable assumptions about the improvement in tear performance, to further elucidate the mechanism by which the interpenetrating double crosslinked network structure enhances tear performance.

[0068] Based on the above test and analysis results ( Figure 1-3 As can be seen from the perspective of vulcanization mechanism, for GO / NR composites prepared by S / BPO dual crosslinking agents, BPO can decompose to generate free radicals, further initiating the crosslinking reaction of rubber molecular chains, improving the crosslinking density and the uniformity of the rubber network. Simultaneously, the highly efficient synergy between the -CC- crosslinking bonds initiated by BPO and the -C-Sx-C- crosslinking formed by sulfur optimizes the interaction between rubber molecular chains, enabling the material to more effectively transfer stress during tensile and tearing processes, thereby significantly improving the tear strength of the material. This indicates that the dual crosslinking system of this invention has significant advantages in improving the tear resistance of NR, effectively inhibiting crack propagation and improving the toughness of the rubber. Furthermore, it is further demonstrated that the highly efficient synergy between nanofiller reinforcement and the interpenetrating dual crosslinking network structure of this invention indeed achieves the goal of significantly improving the tear strength of NR vulcanizates from both the aspects of preventing crack propagation and reducing crack initiation.

[0069] Table 1 Formulations of Comparative Examples 1-3 and Examples 1-5

[0070]

[0071] Table 2 Performance of Comparative Examples 1-3 and Examples 1-5

[0072]

[0073] As shown in Table 2, compared with the GO / NR composites of the single sulfur vulcanization system in Comparative Examples 1-3, the tensile strength, tear strength, hardness, dynamic compression fatigue heat generation performance, and crosslinking density of the high tear strength graphene-modified natural rubber based on the interpenetrating double crosslinked network structure constructed by the dual vulcanizing agent in this invention (Examples 1-5) are all improved. In particular, for Comparative Example 2, the tear strength of Example 2 is increased by 63.5%, showing a significant improvement effect. In addition, compared with Comparative Examples 1-3, the crosslinking rate of Examples 1-5 is reduced, which again shows that: the sulfur in the dual vulcanizing agent has a fast vulcanization rate and preferentially forms a high crosslinking density carbon-sulfur bond crosslinking network -C-Sx-C- in the natural rubber composite; the BPO has a slow vulcanization rate and selectively fills the defects in the sulfur vulcanization network (such as unreacted sites in the main chain) and forms stable -CC- crosslinking bonds at the branches, improving the structural integrity of the crosslinking network. Furthermore, compared to the single-sulfur vulcanized GO / NR of Comparative Example 2, the crosslinking density of GO / NR with an interpenetrating double crosslinked network structure in Examples 1-3, with the same sulfur addition, increased by 6.8%, 9.0%, and 12.2%, respectively; the tear strength increased by 10.8%, 63.6%, and 58.9%, respectively; the compression fatigue heat generation performance decreased by 3.4%, 8.2%, and 10.2%, respectively; and the hardness increased by 0%, 3.4%, and 4.2%, respectively. This further demonstrates that the present invention, based on the efficient synergy of nanofiller reinforcement and the interpenetrating double crosslinked network structure, effectively achieves the goal of significantly improving the tear strength of NR vulcanizates from both the perspectives of preventing crack propagation and reducing crack initiation. In addition, it also reduces the heat generation value of the rubber during dynamic compression.

[0074] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A preparation process for graphene-modified natural rubber based on an interpenetrating double crosslinked network structure constructed using a dual vulcanizing agent, characterized in that, Includes the following steps: (1) A certain amount of deionized water was added to natural rubber latex at temperature T1, followed by a certain amount of graphene oxide aqueous dispersion. The stirring speed was v1 and the mechanical stirring time was t1. Then, flocculant was added to make the latex flocculate. The raw rubber obtained was washed and dehydrated multiple times, and then dried to constant weight at temperature T2 to obtain graphene oxide modified natural rubber masterbatch. (2) The graphene oxide modified natural rubber masterbatch obtained in step (1) is placed in a mixer and mixed at a temperature of T3 for a time of t2 before the rubber compound is discharged. During this period, rubber additives and reinforcing fillers are added. The discharged rubber compound is cooled to room temperature and then mixed at a temperature of T4 for a time of t3 using a two-roll mill. During this period, sulfur vulcanizing agent and peroxide are added in sequence and mixed evenly. The roller gap is reduced to thin the rubber compound until there are no air bubbles, and a compound is obtained. The peroxide is benzoyl peroxide. The mass ratio of natural rubber to sulfur and peroxide in the graphene oxide modified natural rubber masterbatch is 100:1.5:2~3. (3) The compound rubber was placed at temperature T5 for time t4, and then vulcanized in a mold at temperature T6 and pressure P1 for time t5; graphene-modified natural rubber with an interpenetrating double crosslinked network structure based on a double vulcanizing agent was obtained.

2. The preparation process of graphene-modified natural rubber based on an interpenetrating double crosslinked network structure constructed with a dual vulcanizing agent according to claim 1, characterized in that, In step (1), the temperature T1 is room temperature; the amount of deionized water added is to make the concentration of the prepared natural rubber latex emulsion 15~35 wt%; the stirring time t1 is 10~60 min, the stirring speed v1 is 100~1000 rad / min; and the drying temperature T2 of the raw rubber is 40~80 °C.

3. The preparation process of graphene-modified natural rubber based on an interpenetrating double crosslinked network structure constructed with a dual vulcanizing agent according to claim 1, characterized in that, In step (1), the concentration of the added graphene oxide dispersion is 1~10 mg / mL; the flocculant is selected from at least one of calcium chloride, formic acid, hydrochloric acid, sodium chloride and potassium chloride solution, and the concentration is 5~20 wt%; the mass ratio of natural rubber to graphene oxide in the obtained graphene oxide modified natural rubber masterbatch is 100:0.2~2.

4. The preparation process of graphene-modified natural rubber based on an interpenetrating double crosslinked network structure constructed with a dual vulcanizing agent according to claim 1, characterized in that, In step (2), the internal mixing temperature T3 = 100~120 °C and the internal mixing time t2 = 10~16 min; the initial mixing temperature T4 = 50~70 °C and the initial mixing time t3 = 10~15 min.

5. The preparation process of graphene-modified natural rubber based on an interpenetrating double crosslinked network structure constructed with a dual vulcanizing agent according to claim 1, characterized in that, In step (2), the rubber additives are composed of antioxidants, anti-oxidants, vulcanization accelerators, activators, and softeners in a mass ratio of 2:2:2:5:2; the mass ratio of natural rubber to reinforcing filler in the graphene oxide modified natural rubber masterbatch is 100:

35.

6. The preparation process of graphene-modified natural rubber based on an interpenetrating double crosslinked network structure constructed with a dual vulcanizing agent according to claim 5, characterized in that, The vulcanization accelerator is at least one of N-tert-butyl-2-benzothiazole sulfenamide, N-cyclohexyl-2-benzothiazole sulfenamide, and N-(diethylidene oxide)-2-benzothiazole sulfenamide; the antioxidant is at least one of 2,6-di-tert-butyl-4-methylphenol, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, and 2-thiol-benzoimidazole; the antioxidant is at least one of N-(1-methylisopentyl)-N'-phenyl-p-phenylenediamine and p-phenylaniline or dilauryl sulfide; the activator is at least one of zinc gluconate, zinc oxide, and magnesium oxide; the softener is at least one of stearic acid, dibutyl titanate, and dioctyl adipate; and the reinforcing filler is at least one of carbon black N110, N220, N330, N339, N375, N550, N660, and silica.

7. The preparation process of graphene-modified natural rubber based on an interpenetrating double crosslinked network structure constructed with a dual vulcanizing agent according to claim 1, characterized in that, In step (2), the mass ratio of natural rubber to rubber additives in the graphene oxide modified natural rubber masterbatch is 100:8~15.

8. The preparation process of graphene-modified natural rubber based on an interpenetrating double crosslinked network structure constructed with a dual vulcanizing agent according to claim 1, characterized in that, In step (3), T5 = room temperature, the compound standing time t4 = 20~30 h; the vulcanization temperature T6 = 140~160 °C, the vulcanization pressure P1 = 10~20 MPa, and the vulcanization time t5 = 5~15 min.

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