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

Abstract

The invention belongs to the technical field of graphene and functional rubber composite materials, and particularly relates to a simplified preparation process of high-tear-strength graphene modified natural rubber with an interpenetrating double-crosslinking network structure constructed on the basis of double vulcanizing agents. Sulfur quickly forms a carbon-sulfur bond cross-linked network-C-Sx-C-with high cross-linking density in the natural rubber composite material to form a mechanical bearing skeleton between natural rubber main chains, so that the natural rubber composite material is endowed with high tear strength and fatigue resistance; the vulcanization rate of peroxide is relatively slow, the peroxide is slowly decomposed in a relatively low temperature region to generate free radicals, and a stable-C-C-crosslinking bond secondary crosslinking network between tail end chain segments of a carbon-sulfur bond main network is constructed outside a sulfur vulcanization skeleton network, so that the three-dimensional structural integrity of the vulcanization network is improved, and the loss modulus of rubber is reduced; and thus, heat generated during dynamic compression of the rubber is reduced. The tear strength of the natural rubber vulcanized rubber is effectively improved based on the synergy of nanofiller enhancement and an interpenetrating double-crosslinking network structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of graphene and functional rubber composites, and specifically relates to a streamlined preparation process of high tear strength graphene-modified natural rubber with an interpenetrating double cross-linked network structure constructed based on a double vulcanizing agent. Background Art

[0002] As a strategic polymer material, the high elasticity, high abrasion resistance and dynamic fatigue performance of natural rubber (NR) make it dominant in key fields such as tire treads, industrial conveyor belts and heavy equipment seals. However, with the extreme and lightweight development of modern equipment, the tear strength of traditional NR composites gradually fails to meet the requirements. For example, under high-speed dynamic loads of tires, the proportion of tear failures caused by the expansion of tread cracks along stress concentration areas exceeds 60%; while the longitudinal tear problem of mine conveyor belts directly leads to shutdown accidents, causing significant economic losses. The core of these problems lies in: the limited tear strength of the NR matrix itself, and the single cross-linked network formed by traditional vulcanization is prone to induce micro-crack proliferation due to local stress concentration, ultimately leading to macroscopic tearing.

[0003] Currently, improving the tear strength of rubber mainly starts from two aspects: preventing crack propagation and reducing the generation of crack sources. Preventing crack propagation generally adopts the strategy of nano-filler reinforcement. Nano-fillers (such as graphene oxide (GO), carbon nanotubes (CNT), etc.) have a large specific surface area and abundant surface active groups. When rubber molecular chains come into contact with them, they can be adsorbed on the surface of the filler through physical interactions such as van der Waals forces and hydrogen bonds. This adsorption makes the rubber molecular chains form a certain restraint on the surface of the filler, forming a tangled structure, which hinders the crack propagation path and thus prevents crack propagation. However, there are the following bottlenecks in practical applications: ⑴ The fillers are unevenly dispersed and become crack sources; ⑵ The cross-linking density and distribution range of a single vulcanization system are limited, and it is difficult to construct a multi-level energy dissipation mechanism to resist tear propagation.

[0004] The interpenetrating double cross-linked network structure is a polymer material design strategy, and its core feature is that two or more polymer networks penetrate each other and form a synergistic enhancement effect through multiple cross-linking mechanisms. The interpenetrating property means that two or more independently cross-linked polymer networks are intertwined at the molecular scale to form a three-dimensional interpenetrating topological structure. The double cross-linking method combines physical cross-links (such as hydrogen bonds, van der Waals forces, crystal domains) and chemical cross-links (covalent bonds, dynamic bonds) or a combination of different chemical cross-linking systems inside the network. The performance advantages mainly include: ⑴ Mechanical properties: high strength and high toughness are achieved through energy dissipation mechanisms (such as dynamic bond breakage and recombination) and network synergy. ⑵ Functional tunability: By regulating the cross-linking density, network ratio and cross-linking type, the material can be endowed with self-healing, recyclable or environment-responsive properties, etc.

[0005] Reducing crack sources through the synergy of different types of crosslinked networks has also become an important method for improving the tear strength of rubber composites. That is, the different crosslinking reaction rates of two or more vulcanizing agents can be utilized to preferentially form a crosslinked network in natural rubber composites, which serves as the mechanical load-bearing framework between the main chains of natural rubber. Subsequently, the crosslinked network of another vulcanizing agent constructs a secondary crosslinked network outside the previously formed crosslinked network, filling the defects of the previous crosslinked network, such as unreacted sites on the main chain, and forming more crosslinking points at the branched chains. Finally, by improving the uniformity of the crosslinked network, crack sources and their propagation are reduced, forming a multi-level anti-tear barrier, thereby effectively improving the tear strength of rubber composites and extending their service life.

[0006] NR usually needs to be vulcanized during the processing to improve stability and durability. Peroxide vulcanization is a commonly used vulcanization method. The principle is to add peroxide as a vulcanizing agent to the rubber. After heating, the peroxide releases active oxygen, promoting the formation of a stable carbon-carbon bond crosslinked network between rubber molecular chains, thereby achieving the purpose of vulcanization. The advantages of peroxide vulcanizates include: (1) excellent high-temperature resistance and good thermal stability; (2) small compression set and low creep; (3) outstanding anti-reversion property, suitable for long-term vulcanization processes. The disadvantages include: (1) the mechanical strength (such as tear resistance) is usually lower than that of the sulfur vulcanization system; (2) the processing safety is poor, and the temperature needs to be strictly controlled to prevent early decomposition. Therefore, although peroxide plays a certain role in the vulcanization process of NR, due to its slow reaction rate and limited use, traditional vulcanizing agents such as sulfur or thioether are still mainly used in practical applications. Summary of the Invention

[0007] In order to improve the tear strength of NR vulcanizates, the present invention is based on the efficient synergy of nano-filler reinforcement and interpenetrating double crosslinked network structure, and improves the tear strength of NR vulcanizates from two aspects of preventing crack propagation and reducing crack source generation, breaking through the physical limit of traditional reinforcement strategies, and being able to provide a new solution path for the next generation of high tear strength rubber composites. [[ID=H10]]

[0008] The present invention is realized through the following technical solutions: A simplified preparation process of high tear strength graphene-modified natural rubber based on an interpenetrating double crosslinked network structure constructed by a double vulcanizing agent, comprising the following steps:

[0009] (1) At temperature T1, a certain amount of deionized water is added to natural latex, and then a certain amount of graphene oxide aqueous dispersion is added. Mechanical stirring is carried out for time t1 at stirring speed v1, and then a flocculant is added to flocculate the latex; the obtained raw rubber is washed and dehydrated multiple times, and then dried to constant weight at temperature T2 to obtain graphene oxide-modified natural rubber masterbatch;

[0010] (2) Place the graphene oxide modified natural rubber masterbatch obtained in step (1) into a mixer. After kneading for time t2 at temperature T3, discharge the rubber compound, and add rubber additives and reinforcing fillers during this period. Cool the discharged rubber compound to room temperature, and then use a two-roll mill to knead for time t3 at temperature T4. During this period, add vulcanizing agent sulfur and peroxide in sequence. After mixing evenly, reduce the roll gap to thin the rubber compound until there are no air bubbles to obtain a mixed rubber compound.

[0011] (3) Place the mixed rubber compound at temperature T5 for time t4, and then vulcanize for time t5 at temperature T6 and a certain pressure P1 in a mold. During the vulcanization process, the vulcanizing agent sulfur rapidly forms a high cross-linking density carbon-sulfur bond cross-linking network -C-Sx-C- in the natural rubber composite material, constituting the mechanical load-bearing skeleton between the main chains of natural rubber and endowing high tear strength and fatigue resistance. The vulcanization rate of the peroxide is relatively slow, and it slowly decomposes to generate free radicals in the lower temperature region, constructing a stable -C-C- cross-linking bond secondary cross-linking network between the end segments of the carbon-sulfur bond main network outside the sulfur vulcanization skeleton network, improving the three-dimensional structure integrity of the vulcanization network, reducing the loss modulus of the rubber, and thus reducing the heat generation during dynamic compression of the rubber. Obtain high tear strength graphene modified natural rubber based on the interpenetrating double cross-linking network structure constructed by a double vulcanizing agent.

[0012] As a further improvement of 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 of the technical solution of the present invention, in step (1), temperature T1 is room temperature; the addition amount of deionized water is such that the concentration of the prepared natural rubber latex emulsion is 15 - 35 wt%; the stirring time t1 is 10 - 60 min, and the stirring speed v1 is 100 - 1000 rad / min; the drying temperature T2 of the raw rubber is 40 - 80 °C.

[0014] As a further improvement of 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 solutions, 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 of the technical solution of the present invention, in step (2), the kneading temperature T3 = 100 - 120 °C, and the kneading time t2 = 10 - 16 min; the two-roll mill temperature T4 = 50 - 70 °C, and the two-roll mill time t3 = 10 - 15 min.

[0016] As a further improvement of the technical solution of the present invention, in step (2), the rubber auxiliaries are composed of an antioxidant, an antioxidant, 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 of the technical solution of the present invention, the vulcanization accelerator is at least one of N-tert-butyl-2-benzothiazole sulfenamide, N-cyclohexyl-2-benzothiazole sulfenamide, and N-(diethylenedioxy)-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-mercaptobenzothiazole; the antioxidant is at least one of N-(1-methylisoamyl)-N'-phenyl-p-phenylenediamine and p-phenylaniline or dilauryl sulfide propionate; 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; the reinforcing filler is at least one of carbon black N110, N220, N330, N339, N375, N550, N660, and silica.

[0018] As a further improvement of the technical solution of the present invention, in step (2), the mass ratio of natural rubber to rubber auxiliaries 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 of the technical solution of the present invention, in step (3), T5 = room temperature, the standing time t4 of the mixed rubber is 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.

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

[0021] (1) Through the adsorption effect between the functional groups on the surface of the graphene oxide nano-filler and the rubber molecular chain, the present invention forms a tangling structure, blocks the crack propagation path, and improves the tear strength.

[0022] (2) The present invention forms an interpenetrating double cross-linked network structure through two vulcanizing agents: sulfur has a relatively fast vulcanization rate and preferentially forms a high cross-linking density carbon-sulfur bond cross-linked network -C-Sx-C- in the natural rubber composite material, constituting the mechanical load-bearing skeleton between the main chains of natural rubber and endowing high tear strength and fatigue resistance; the peroxide has a relatively slow vulcanization rate and slowly decomposes to generate free radicals in the lower temperature region, constructing a stable -C-C- cross-linked bond secondary cross-linked network between the end 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.

[0023] (3) The present invention enhances the high-efficiency synergy between nano-fillers and the interpenetrating double cross-linked network structure, and improves the tear strength of NR vulcanizate from two aspects of preventing crack propagation and reducing the generation of crack sources, breaking through the physical limit of traditional reinforcement strategies, and providing a new solution path for the next generation of rubber composites with high tear strength.

[0024] (4) The preparation process of the present invention is simple and has no strict requirements. All the equipment involved is conventional equipment, which is easy to industrialize production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings here are incorporated into the specification and constitute a part of this specification, showing the embodiments in line with the present invention, and are used together with the specification to explain the principles of the present invention.

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

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

[0028] Figure 2 It is the vulcanization curves of GO / NR prepared in Examples 1-5 and Comparative Examples 1-3 of the present invention.

[0029] Figure 3 It is the schematic diagram of the mechanical behavior of GO / NR prepared in Examples 1-5 and Comparative Examples 1-3 of the present invention under tear action. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the solution of the present invention will be further described below. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0031] In the following description, many specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0032] The present invention provides a specific embodiment of a simplified preparation process of high tear strength graphene-modified natural rubber based on an interpenetrating double cross-linked network structure constructed by a double vulcanizing agent, including the following steps:

[0033] (1) Add a certain amount of deionized water to natural latex at temperature T1, and then add a certain amount of graphene oxide aqueous dispersion. Mechanically stir for time t1 at stirring speed v1, and then add a flocculant to flocculate the latex; the obtained raw rubber is washed with water and dehydrated multiple times, and then dried to constant weight at temperature T2 to obtain graphene oxide-modified natural rubber masterbatch.

[0034] (2) Place the graphene oxide-modified natural rubber masterbatch obtained in step (1) in an internal mixer. After kneading for time t2 at temperature T3, discharge the rubber compound, and add rubber additives and reinforcing fillers during this period; cool the discharged rubber compound to room temperature, and then use a two-roll mill to roll for time t3 at temperature T4. During this period, successively add vulcanizing agent sulfur and peroxide, mix evenly, and then reduce the roll gap to thin the rubber compound until there are no bubbles to obtain a mixed rubber compound.

[0035] (3) Place the mixed rubber compound at temperature T5 for time t4, and then vulcanize for time t5 at temperature T6 and a certain pressure P1 in a mold; during the vulcanization process, the vulcanizing agent sulfur rapidly forms a high cross-linking density carbon-sulfur bond cross-linked network -C-Sx-C- in the natural rubber composite material, constituting the mechanical load-bearing skeleton between the main chains of natural rubber, endowing high tear strength and fatigue resistance; the vulcanization rate of the peroxide is relatively slow, and it slowly decomposes to generate free radicals in a lower temperature region, constructing a stable -C-C- cross-linked bond secondary cross-linked network between the end chain segments of the carbon-sulfur bond main network outside the sulfur vulcanization skeleton network, improving the three-dimensional structure integrity of the vulcanization network, reducing the loss modulus of the rubber, and thus reducing the heat generation during dynamic compression of the rubber; obtain high tear strength graphene-modified natural rubber based on an interpenetrating double cross-linked network structure constructed by a double vulcanizing agent.

[0036] In an 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 addition amount of deionized water is such that the concentration of the prepared natural rubber latex emulsion is 15 - 35 wt%; the stirring time t1 is 10 - 60 min, and the stirring speed v1 is 100 - 1000 rad / min; the drying temperature T2 of the raw rubber is 40 - 80 °C.

[0038] In an example provided by 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.

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

[0040] In an example provided by the present invention, in step (2), the rubber additives are composed of an antioxidant, an antioxidant, a vulcanization accelerator, an activator, and a softener according to 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-(oxydiethylene)-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-mercaptobenzothiazole; the antioxidant is at least one of N-(1-methylisoamyl)-N'-phenyl-p-phenylenediamine and p-phenylenediamine or dilauryl thiodipropionate; 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; the reinforcing filler is at least one of carbon black N110, N220, N330, N339, N375, N550, N660, and silica.

[0042] In an 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 standing time t4 of the mixed rubber is 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.

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

[0045] Example 1:

[0046] A high tear strength GO / NR with an interpenetrating double cross-linked network structure constructed based on a double vulcanizing agent and a streamlined preparation process specifically include the following steps:

[0047] ① At room temperature (25 °C), deionized water is added to the natural rubber latex emulsion, and the concentration is controlled to be 30 wt%; a 2.5 mg / mL GO aqueous dispersion is added and mechanically stirred for 30 min at a stirring speed of 500 rad / min; a 10 wt% calcium chloride solution is added to flocculate the latex, where the volume ratio of the natural rubber latex emulsion: GO aqueous dispersion: calcium chloride solution is 167:100:30; the obtained raw rubber is washed with water and dehydrated multiple times, and then dried to a constant weight at 60 °C to obtain a modified NR masterbatch with a natural rubber: graphene oxide mass ratio of 100:0.5, that is, the GO / NR masterbatch.

[0048] ② The GO / NR masterbatch prepared in step ① with 100 phr of NR content is added to an internal mixer at 110 °C and kneaded for 4 min, then 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) are added. After kneading for 4 min, 5 phr of activator zinc oxide and 2 phr of softener stearic acid are added and kneaded for 4 min. Subsequently, 35 phr of N330 carbon black is added and the rubber compound is discharged; after the discharged rubber compound is cooled to room temperature, it is kneaded on a two-roll mill at 60 °C for 10 min. During this period, 1.5 phr of sulfur and 1 phr of benzoyl peroxide (BPO) are added in sequence, and after mixing evenly, it is passed through the rolls until there are no bubbles in the rubber compound to obtain the mixed rubber.

[0049] ③ After the mixed rubber is placed at room temperature for 24 h, it is put into a mold and vulcanized at 15 MPa and 150 °C for 6 min (t c90 vulcanization for 6 min (t c90Determined by a rubber processing analyzer); during vulcanization, the vulcanizing agent sulfur rapidly forms a carbon-sulfur bond crosslinking network -C-Sx-C- with a high crosslinking density in the natural rubber composite, constituting the mechanical load-bearing skeleton between the main chains of natural rubber and endowing high tear strength and fatigue resistance; the vulcanization rate of the peroxide is relatively slow, and it slowly decomposes to generate free radicals in the lower temperature region, constructing a stable -C-C- crosslinking bond secondary crosslinking network between the end 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 further reducing the heat generation during dynamic compression of the rubber; a high tear strength GO / NR with an interpenetrating double crosslinking network structure based on a double vulcanizing agent is obtained.

[0050] Example 2:

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

[0052] Example 3:

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

[0054] Example 4:

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

[0056] Example 5:

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

[0058] Comparative Example 1:

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

[0060] Comparative Example 2:

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

[0062] Comparative Example 3:

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

[0064] The GO / NR composites obtained in Examples 1-5 and Comparative Examples 1-3 were subjected to performance tests. The test standard for tensile properties was GB / T 528-2009, and the tensile rate was 500 mm / min. The test standard for tear properties was GB / T 529-2008. The test standard for hardness was GB / T 531.1-2008. The test standard for crosslink density was GB / T 533-2008. The test standard for heat generation performance was GB / T 1687.1-2016.

[0065] It can be seen from Figure 1 that for the GO / NR composites with an interpenetrating double crosslink network structure prepared in Examples 1-5, the characteristic absorption peak at 836-838 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 be used as an important indicator of the degree of double bond reaction. For the GO / NR with a single sulfur crosslinking system in Comparative Examples 1-3, the crosslinking reaction mainly involves the -C=C- double bond in the isoprene unit. Through the FT-IR spectra, it was observed that as the sulfur addition amount increased from 1 phr to 2 phr, the intensity of the -C=C- characteristic peak at 836 cm -1 showed a gradient decay, indicating that sulfur radicals preferentially attack the double bond structure, thus preferentially forming a crosslink network of sulfur bonds (-C-S X -C-). In addition, for Examples 1-5, after adding BPO as a crosslinking agent, the peak intensity at 836 cm -1 remained stable, indicating that the reaction of BPO with double bonds is relatively limited. After BPO participates in the vulcanization reaction, benzoic acid is generated, and the C=O characteristic peak of benzoic acid was detected at 1699 cm -1 , further confirming that BPO can participate in the crosslinking reaction. Therefore, a GO / NR composite with an interpenetrating double crosslink network structure can be obtained by simultaneously adding sulfur and BPO (S / BPO).

[0066] It can be seen from Figure 2 that compared with Comparative Examples 1-3, the crosslink density of the rubber composites prepared in Examples 1-5 of the present invention increased, but the increase was not significant, indicating that the C-C bonds formed by BPO crosslinking mainly supplemented the carbon-sulfur crosslink network; in addition, compared with Comparative Examples 1-3, the vulcanization curve of Examples 1-5 became slower during the rapid vulcanization period, indicating that the crosslinking rate of BPO was slower and mainly played a supplementary role in the carbon-sulfur crosslink network.

[0067] Figure 3 FIG. is a schematic diagram of the mechanical behavior of the GO / NR composites prepared in Examples 1-5 and Comparative Examples 1-3 under tear action. These figures were drawn on the basis of a reasonable speculation on the improvement of tear properties to further clarify the mechanism of the interpenetrating double crosslink network structure in enhancing tear properties.

[0068] According to the above test and analysis results ( Figures 1 - 3 ), it can be seen that from the perspective of vulcanization mechanism, for the GO / NR composite prepared with S / BPO double 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; meanwhile, the -C-C- crosslinking bonds initiated by BPO and the -C-Sx-C- crosslinking formed by sulfur are highly synergistic, optimizing the interaction between rubber molecular chains, enabling the material to transfer stress more effectively during the stretching and tearing processes, thus significantly improving the tear strength of the material, indicating that the double crosslinking system of the present invention has significant advantages in improving the tear resistance of NR and can effectively inhibit crack propagation and improve the toughness of the rubber. In addition, it is further proved that based on the efficient synergy of nano-filler reinforcement and interpenetrating double crosslinking network structure, the present invention indeed achieves the purpose of significantly improving the tear strength of NR vulcanizate from both aspects of preventing crack propagation and reducing the generation of crack sources.

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

[0070]

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

[0072]

[0073] As can be seen from Table 2, compared with the GO / NR composites with a single sulfur vulcanization system in Comparative Examples 1-3, the tensile strength, tear strength, hardness, dynamic compression fatigue heat generation performance, and crosslink density of the graphene-modified natural rubber with an interpenetrating double crosslink network structure constructed based on a double vulcanizing agent in the present invention (Examples 1-5) have all been improved. In particular, for Comparative Example 2, the tear strength of Example 2 increased by 63.5%, and the improvement effect was significant. In addition, compared with Comparative Examples 1-3, the crosslinking rate of Examples 1-5 decreased, indicating again that: sulfur in the double vulcanizing agent has a fast vulcanization rate and preferentially forms a high crosslink density carbon-sulfur bond crosslink network -C-Sx-C- in the natural rubber composite quickly; BPO has a slow vulcanization rate, selectively fills the defects in the sulfur vulcanization network (such as unreacted sites in the main chain), and forms stable -C-C- crosslink bonds at the branched chains, improving the structural integrity of the crosslink network. In addition, compared with the GO / NR with a single sulfur vulcanization in Comparative Example 2, the crosslink densities of the GO / NR in Examples 1-3 with an interpenetrating double crosslink network structure with the same sulfur addition amount increased by 6.8%, 9.0%, and 12.2% respectively, the tear strengths 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. It is further proved that based on the efficient synergy of nano-filler reinforcement and interpenetrating double crosslink network structure, the present invention has indeed achieved the purpose of significantly improving the tear strength of NR vulcanizates from both aspects of preventing crack propagation and reducing the generation of crack sources. In addition, the heat generation value during dynamic compression of the rubber has been reduced.

[0074] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Although the foregoing embodiments have been described in detail, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements 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 by the protection scope of the claims.

Claims

1. A streamlined preparation process of graphene-modified natural rubber with an interpenetrating double cross-linked network structure constructed based on double vulcanizing agents, characterized in that, It includes the following steps: (1) Add a certain amount of deionized water to natural latex at temperature T1, then add a certain amount of graphene oxide aqueous dispersion, mechanically stir for time t1 at stirring speed v1, and then add a flocculant to flocculate the latex; after the obtained raw rubber is washed and dewatered multiple times, it is dried to constant weight at temperature T2 to obtain graphene oxide modified natural rubber masterbatch; (2) Place the graphene oxide modified natural rubber masterbatch obtained in step (1) in an internal mixer, discharge the rubber compound after kneading for time t2 at temperature T3, and add rubber additives and reinforcing fillers during this period; cool the discharged rubber compound to room temperature, and then roll it on an open mill for time t3 at temperature T4. During this period, sulfur and peroxide as vulcanizing agents are added in sequence, and after mixing evenly, reduce the roll gap to thin the rubber compound until there are no bubbles to obtain a mixed rubber; (3) Place the mixed rubber at temperature T5 for time t4, and then vulcanize it for time t5 at temperature T6 and a certain pressure P1 in a mold; during the vulcanization process, the vulcanizing agent sulfur rapidly forms a high cross-linking density carbon-sulfur bond cross-linking network -C-Sx-C- in the natural rubber composite, constituting the mechanical load-bearing skeleton between the main chains of natural rubber, endowing high tear strength and fatigue resistance; the vulcanization rate of the peroxide is relatively slow, and it slowly decomposes to generate free radicals in the lower temperature region, constructing a stable -C-C- cross-linking bond secondary cross-linking network between the end chain segments of the carbon-sulfur bond main network outside the sulfur vulcanization skeleton network, improving the three-dimensional structure integrity of the vulcanization network, reducing the loss modulus of the rubber, and thus reducing the heat generation during dynamic compression of the rubber; obtain high tear strength graphene modified natural rubber based on an interpenetrating double cross-linking network structure constructed by a double vulcanizing agent.

2. The simplified preparation process of a graphene-modified natural rubber with a high tear strength and an interpenetrating double cross-linked network structure constructed based on a double vulcanizing agent, characterized in that, The peroxide is selected from at least one of benzoyl peroxide, di-tert-butyl peroxide, tert-butyl perbenzoate, and diisopropylbenzene peroxide.

3. The simplified preparation process of a graphene-modified natural rubber with a high tear strength and an interpenetrating double cross-linked network structure constructed based on a double vulcanizing agent, characterized in that, In step (1), temperature T1 is room temperature; the addition amount of deionized water is such that the concentration of the prepared natural latex emulsion is 15 - 35 wt%; the stirring time t1 is 10 - 60 min, the stirring speed v1 is 100 - 1000 rad / min; the drying temperature T2 of the raw rubber is 40 - 80 °C.

4. The simplified preparation process of a graphene-modified natural rubber with a high tear strength and an interpenetrating double cross-linked network structure constructed based on a double vulcanizing agent, 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.

5. The simplified preparation process of a graphene-modified natural rubber with a high tear strength and an interpenetrating double cross-linked network structure constructed based on a double vulcanizing agent, characterized in that, In step (2), the kneading temperature T3 = 100 - 120 °C, the kneading time t2 = 10 - 16 min; the rolling temperature T4 = 50 - 70 °C, the rolling time t3 = 10 - 15 min.

6. The streamlined preparation process of a graphene-modified natural rubber with a high tear strength and an interpenetrating double crosslinked network structure constructed based on a double vulcanizing agent, characterized in that, In step (2), the rubber additives are composed of an antioxidant, an antioxidant, a vulcanization accelerator, an activator, and a softener according to a mass ratio of 2:2:2:5:2; the mass ratio of natural rubber to the reinforcing filler in the graphene oxide modified natural rubber masterbatch is 100:

35.

7. The simplified preparation process of a graphene-modified natural rubber with a high tear strength and an interpenetrating double cross-linked network structure constructed based on a double vulcanizing agent, characterized in that, The vulcanization accelerator is at least one of N-tert-butyl-2-benzothiazole sulfenamide, N-cyclohexyl-2-benzothiazole sulfenamide, and N-(diethyleneglycol)-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-mercaptobenzothiazole; the antioxidant is at least one of N-(1-methylisoamyl)-N'-phenyl-p-phenylenediamine and p-phenylenediamine or dilauryl thiodipropionate; 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; the reinforcing filler is at least one of carbon black N110, N220, N330, N339, N375, N550, N660, and silica.

8. The streamlined preparation process of a graphene-modified natural rubber with a high tear strength and an interpenetrating double cross-linked network structure constructed based on a double vulcanizing agent, 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 to 15; the mass ratio of natural rubber to sulfur and peroxide in the graphene oxide modified natural rubber masterbatch is 100:0.5 to 4:0.5 to 4.

9. The streamlined preparation process of a graphene-modified natural rubber with a high tear strength and an interpenetrating double cross-linked network structure constructed based on a double vulcanizing agent, characterized in that, In step (3), T5 = room temperature, the standing time t4 of the mixed rubber is 20 to 30 h; the vulcanization temperature T6 = 140 to 160 °C, the vulcanization pressure P1 = 10 to 20 MPa, and the vulcanization time t5 = 5 to 15 min.

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