CN114891281B - Simplified method for simultaneously optimizing mechanical property, low heat generation and wear resistance of graphene modified natural rubber vulcanized rubber - Google Patents
Simplified method for simultaneously optimizing mechanical property, low heat generation and wear resistance of graphene modified natural rubber vulcanized rubber Download PDFInfo
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Abstract
The invention relates to the field of graphene and functional rubber composite materials thereof, in particular to a simplified method for simultaneously optimizing the mechanical property, low heat generation and wear resistance of graphene modified natural rubber vulcanized rubber; firstly, reducing the number of oxygen-containing functional groups on the surface of a graphene oxide sheet layer through a simplified modification process which is easy for industrial production, and then preparing graphene modified natural rubber vulcanized rubber with optimized mechanical, low heat generation and wear resistance performance by utilizing a water phase collaborative coagulation process and a mechanical blending method; the aqueous phase synergistic coagulation process and the mechanical blending method can uniformly disperse the modified graphene oxide with the reduced number of the surface oxygen-containing functional groups in the natural rubber vulcanized rubber, and the modified graphene oxide with the reduced number of the surface oxygen-containing functional groups can increase the crosslinking density of the natural rubber vulcanized rubber and improve the crosslinking network, so that the graphene modified natural rubber vulcanized rubber with optimized mechanical, low heat generation and wear resistance properties is obtained. The invention has important significance for pushing the application of the graphene in the field of high-performance rubber.
Description
Technical Field
The invention relates to the field of graphene and functional rubber composite materials thereof, in particular to a simplified method for simultaneously optimizing the mechanical property, low heat generation and wear resistance of graphene modified natural rubber vulcanized rubber.
Background
Natural Rubber (NR) has excellent mechanical properties, tear resistance, elasticity, etc., and is widely used in the fields of automobile tires, wires, cables, etc. However, natural rubber requires the addition of fillers to achieve its various functions, including high modulus, high tear resistance, and high thermal conductivity. In addition, in order to manufacture a rubber composite material having excellent comprehensive properties, nanoparticles having characteristics of small size, large surface area, etc. are ideal choices for reinforcing fillers of rubber matrix, wherein representative materials mainly include nano carbon black, carbon nanotubes, nano montmorillonite, graphene, etc.
Graphene is a kind of graphene with sp 2 The new material with the hybridized connection carbon atoms closely stacked into a single-layer two-dimensional honeycomb lattice structure has excellent optical, electrical and mechanical properties, has important application prospects in the fields of materials, micro-nano processing, energy sources, biomedicine, drug delivery and the like, and is considered as a revolutionary material in the future. Graphene Oxide (GO) is a two-dimensional (2D) material with various oxygen-containing functional groups, which is obtained by oxidizing graphite by means of physicochemical and the like, and is an economic way for mass production of graphene. Graphene and its derivatives have excellent mechanical strength, electrical conductivity and thermal conductivity, and are widely used for reinforcing modified rubber, so that the prepared rubber composite material has better mechanical strength, toughness and thermal conductivity.
The mechanical properties are a direct reflection of the rubber cross-linked network construction and filler dispersion conditions. The compression heat build-up of rubber composites is related to the destruction and reconstitution of their filler network, friction between rubber molecular chains, and destruction and rearrangement of the crosslinked network structure. Under the action of dynamic load, the stronger cross-linked network can limit the filler and prevent the macromolecular rubber chains from sliding off the surface of the filler. Abrasion of rubber is related to its own resistance, mechanical properties, filler network structure and cross-linked network structure. Thus, the construction of a more complete crosslinked network is critical to achieving improved rubber properties. The composite material with excellent mechanical properties can expand the application range of rubber, the excellent heat generating property can reduce heat accumulation in the use process of the rubber, and the excellent wear resistance can improve the service life of the rubber.
In many processes for preparing filler/natural rubber, the emulsion blending method has remarkable advantages, not only can improve the dispersibility of the filler, but also is convenient for realizing continuous mixing, and in addition, the mixing time can be shortened, the mixing energy consumption can be reduced, the dust pollution can be reduced, and the like.
Disclosure of Invention
The invention aims to provide a simplified method for simultaneously optimizing the mechanical property, low heat generation and wear resistance of graphene modified natural rubber vulcanized rubber.
In order to solve the technical problems, the invention adopts the following technical scheme: the simplified method for simultaneously optimizing the mechanical, low-heat-generation and wear-resistant properties of the graphene modified natural rubber vulcanized rubber comprises the steps of firstly reducing the number of oxygen-containing functional groups on the surface of a graphene oxide sheet layer through a simplified modification process which is easy for industrial production, and then preparing the graphene modified natural rubber vulcanized rubber with simultaneously optimized mechanical, low-heat-generation and wear-resistant properties by utilizing a water phase synergistic coagulation process and a mechanical blending method; the aqueous phase synergistic coagulation process and the mechanical blending method can uniformly disperse the modified graphene oxide with the reduced surface oxygen-containing functional groups in the natural rubber vulcanized rubber, and the modified graphene oxide with the reduced surface oxygen-containing functional groups can effectively reduce the adsorption of the graphene on the vulcanization aid in the natural rubber composite material system, so that the crosslinking rate and the vulcanization rate of the natural rubber composite material can be improved, the crosslinking density of the vulcanized natural rubber vulcanized rubber is increased, the crosslinking network is more perfect, and the graphene modified natural rubber vulcanized rubber with simultaneously optimized mechanical, low heat generation and wear resistance performance is obtained.
A simplifying method for simultaneously optimizing the mechanical property, low heat generation and wear resistance of graphene modified natural rubber vulcanized rubber specifically comprises the following steps:
(1) adding a reducing agent into water, fully dissolving, adding graphene oxide aqueous dispersion, and reacting for a certain time at a certain temperature to obtain modified graphene oxide aqueous dispersion with effectively reduced surface oxygen-containing functional groups;
(2) preparing modified graphene oxide/natural rubber masterbatch by a water phase synergetic coagulation process: adding deionized water into natural latex, adding modified graphene oxide aqueous dispersion, and fully stirring and mixing to obtain uniformly dispersed mixed emulsion; adding flocculant, the modified graphene oxide particles and rubber particles in natural latex can be mutually adsorbed by pi-pi acting force, and orderly gather in water phase and are co-precipitated to obtain crude rubber; washing the obtained raw rubber with water, removing water and drying to obtain modified graphene oxide/natural rubber masterbatch;
(3) preparation of graphene modified natural rubber vulcanized rubber with optimized mechanical, low heat generation and wear resistance performance: sequentially adding an anti-aging agent, an antioxidant, an activating agent and a softening agent into the modified graphene oxide/natural rubber masterbatch prepared in the step (2), banburying, and uniformly dispersing to obtain a rubber compound; adding a vulcanization accelerator and a vulcanizing agent into the rubber compound, then carrying out open mixing, after mixing uniformly, thinly introducing the rubber compound until the rubber compound is bubble-free, standing the rubber compound for a certain time, placing the rubber compound in a mold, and vulcanizing the rubber compound for a certain time at a certain temperature and under a certain pressure to obtain the graphene modified natural rubber vulcanized rubber with simultaneously optimized mechanical, low heat generation and wear resistance properties.
As a further improvement of the technical scheme of the invention, the raw materials are used in the following proportions: 100 parts of natural rubber, 0.1-5 parts of modified graphene oxide particles and 11-13 parts of rubber auxiliary agents.
As a further improvement of the technical scheme of the invention, in the step (1), the reducing agent is at least one of hydrazine hydrate, ascorbic acid, lithium aluminum hydride, iodine and sodium bisulphite; the reaction temperature is 60-120 ℃ and the reaction time is 2-6h; the concentration of the obtained modified graphene oxide aqueous dispersion liquid is 0.5-10 mg.mL -1 。
As a further improvement of the technical scheme of the invention, in the step (2), the flocculating agent is at least one of a calcium chloride solution, a sodium chloride solution, a potassium chloride solution, a sodium sulfate solution, a hydrochloric acid solution and a formic acid solution.
As a further improvement of the technical scheme of the invention, in the step (2), deionized water is added to the natural latex to ensure that the concentration of the natural latex emulsion is 10-40 wt percent; the concentration of the flocculant is 10wt percent, and the mass ratio of the flocculant to the natural rubber is 2-6:100.
As a further improvement of the technical scheme of the invention, in the step (3), the mass ratio of the anti-aging agent, the antioxidant, the activating agent, the softening agent, the vulcanization accelerator and the vulcanizing agent is 1:1:5:2:2:2.
As a further improvement of the technical scheme of the invention, in the step (3), the vulcanization accelerator is N-tertiary butyl-2-benzothiazole sulfenamide, N-cyclohexyl-2-benzothiazole sulfenamide or N- (diethyl oxide) -2-benzothiazole sulfenamide; the vulcanizing agent is sulfur or sulfur monochloride; the anti-aging agent is 2, 6-di-tert-butyl-4-methylphenol, 2, 4-trimethyl-1, 2-dihydroquinoline polymer or 2-thiol benzimidazole; the antioxidant is N-isopropyl-N' -phenyl p-phenylenediamine, p-phenylaniline or dilauryl sulfurate; the activator is zinc gluconate, zinc oxide or magnesium oxide; the softening agent is stearic acid, dibutyl titanate or dioctyl adipate.
As a further improvement of the technical scheme of the invention, in the step (3), the mixing temperature of the internal mixer is 105-120 ℃ and the mixing time is 3-5min; the open mill temperature is 50-70 ℃ and the open mill time is 8-12min; the parking time of the rubber compound is 18-36h; the vulcanization temperature is 135-170 ℃, the vulcanization pressure is 10-30MPa, and the vulcanization time is 10-25min.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the invention, the number of oxygen-containing functional groups on the surface of the graphene oxide sheet layer is reduced by utilizing a simplified modification process which is easy for industrial production, so that the adsorption of modified graphene oxide to a vulcanization aid in a composite material system is weakened, the crosslinking rate and vulcanization rate of a natural rubber composite material are improved, the crosslinking density of the natural rubber vulcanized rubber is increased, the crosslinking network is more perfect, and the interface interaction between the modified graphene oxide sheet and the base natural rubber is improved, so that the natural rubber vulcanized rubber with optimized mechanical, low heat generation and wear resistance properties is finally obtained.
(2) The oxygen-containing functional groups on the surface of the graphene oxide sheet layer have an important influence on the dispersibility of graphene in the natural rubber latex and further the dispersibility of graphene in the finally prepared natural rubber vulcanized rubber, and the larger the number of the oxygen-containing functional groups is, the better the dispersibility of graphene in the natural rubber latex and further the dispersibility of graphene in the finally prepared natural rubber vulcanized rubber is; according to the invention, through a water phase synergistic coagulation process and a mechanical blending method, the problem that modified graphene oxide is difficult to disperse uniformly in natural rubber latex and then in the finally prepared natural rubber vulcanized rubber due to the reduction of the number of oxygen-containing functional groups on the surface of a sheet layer is effectively solved, and in addition, the modified graphene oxide with the reduced number of oxygen-containing functional groups on the surface can increase the crosslinking density and improve the crosslinking network of the natural rubber vulcanized rubber, so that the natural rubber vulcanized rubber with simultaneously optimized mechanical, low heat generation and wear resistance properties is obtained.
(3) The preparation process disclosed by the invention is simple, environment-friendly and free of any harsh requirements, and conventional equipment is involved, so that the preparation process is easy for industrial production, and has important significance for promoting the application of graphene in the field of high-performance rubber.
Drawings
FIG. 1 XPS spectra of graphene oxide prepared in examples 1-3 and comparative example 2. Wherein (a) is a full spectrum, and (b) - (e) are fitted curves of C1s spectra.
FIG. 2 the mechanical, low heat build-up and abrasion resistance properties of the prepared natural rubber vulcanizates of examples 1-3 and comparative examples 1-2 are simultaneously optimized for vulcanization curves, and Table 1 summarizes the vulcanization characteristics of the rGO/NR composites of modified graphene oxides rGO with different numbers of oxygen-containing functional groups.
FIG. 3 relaxation time curves of mechanical, low heat build-up and abrasion resistance simultaneously optimized natural rubber vulcanizates prepared in examples 1-3 and comparative examples 1-2.
FIG. 4 the mechanical, low heat build-up and abrasion resistance properties of the natural rubber vulcanizates prepared in examples 1-3 and comparative examples 1-2 were simultaneously optimized for crosslink density.
FIG. 5 DSC curves of mechanical, low heat build-up and abrasion resistance properties of the natural rubber vulcanizates prepared in examples 1-3 and comparative examples 1-2 while optimizing.
FIG. 6 (a) stress-strain curve and (b) Mooney-Rivlin curve of the mechanical, low heat build-up and abrasion resistance properties of the natural rubber vulcanizates prepared in examples 1-3 and comparative examples 1-2 were simultaneously optimized.
Detailed Description
The invention is further illustrated below with reference to specific examples.
Examples 1 to 3
A simplifying method for simultaneously optimizing the mechanical property, low heat generation and wear resistance of graphene modified natural rubber vulcanized rubber comprises the following specific steps of:
(1) the graphene oxide simplified modification process effectively reduces the number of oxygen-containing functional groups on the surface: 1g, 2g and 3g of reducing agent ascorbic acid are added into water respectively, stirred for 10min, fully mixed, and added with graphene oxide dispersion liquid (200 mL,5 mg.mL) -1 ) Stirring and reacting for 3 hours at 95 ℃ to obtain modified graphene oxide aqueous dispersion liquid with different oxygen-containing functional groups on the surface, wherein the modified graphene oxide obtained in the example 1 with the addition amount of a reducing agent is represented by rGO-1, the modified graphene oxide obtained in the example 2 with the addition amount of a reducing agent is represented by rGO-2, and the modified graphene oxide obtained in the example 3 with the addition amount of a reducing agent is represented by rGO-3;
(2) preparing modified graphene oxide/natural rubber masterbatch by a water phase synergetic coagulation process: a certain amount of deionized water is added into natural latex (167 g,60 wt.%) and stirred until uniform, so as to obtain natural latex emulsion with the concentration of 20wt.%, and then the modified graphene oxide aqueous dispersion prepared in the step (1) is added (200 mL,5 mg.mL) -1 ) Fully stirring and mixing to obtain uniformly dispersed mixed emulsion; 10wt.% CaCl was added with flocculant 2 25g of solution, so that the modified graphene oxide particles and the rubber particles are orderly gathered and co-precipitated in the water phase; washing the obtained raw rubber with water, removing water, and drying in a drying oven at 65 ℃ to constant weight, thereby obtaining modified graphene oxide/natural rubber masterbatch;
(3) preparation of natural rubber vulcanized rubber with mechanical, low heat generation and wear resistance performance optimized simultaneously: 100g of modified graphene oxide/natural rubber masterbatch is placed in an internal mixer and mixed at 110 ℃ and 40rpm, 1g of antioxidant 4010NA, 1g of antioxidant RD,5g of activator ZnO and 2g of softener SA are added three times during mixing, and the mixture is discharged. After the sizing material is cooled to room temperature, transferring the sizing material to an open mill, carrying out open mill at 60 ℃, adding 2g of vulcanization accelerator NOBS and 1g of sulfur after uniform dispersion, and carrying out thin-pass until the sizing material has no bubbles after uniform mixing. After stopping the rubber for 24 hours, the rubber compound is vulcanized for a certain time (t) at 150 ℃ and 15MPa by a vulcanizing machine C90 ) Obtaining the multi-performance simultaneously optimized natural rubber vulcanized rubber, wherein t is as follows C90 Measured by a Rubber Processing Analyzer (RPA). The multi-performance, simultaneously optimized natural rubber vulcanizates obtained in examples 1,2, 3 are denoted rGO-1/NR, rGO-2/NR, and rGO-3/NR, respectively. The formulation of each example is shown in Table 1.
Comparative example 1: (Natural rubber vulcanized rubber)
The specific steps in comparative example 1 are:
(1) the method is free;
(2) preparing a natural rubber masterbatch: adding a certain amount of deionized water into natural latex (167 g,60 wt.%) and stirring until the deionized water is uniformly dispersed to obtain a latex solution with the concentration of 20 wt.%; 10 wt% CaCl flocculant was added 2 25g of solution; washing the obtained crude rubber with water, removing water, and drying in a drying oven at 65 ℃ to constant weight to obtain natural rubber masterbatch;
(3) the same as in examples 1 to 3. The formulation is shown in Table 1.
Comparative example 2: (graphene oxide/Natural rubber vulcanized rubber)
The specific steps in comparative example 2 are:
(2) preparation of graphene oxide/natural rubber composite material: step (2) of examples 1 to 3 is the same as step (2) except that the modified graphene oxide particles in step (2) of examples 1 to 3 are replaced with graphene oxide particles.
(3) The same as in examples 1 to 3. The formulation is shown in Table 1.
Table 1 formulation of examples 1 to 3 and comparative examples 1 to 2
FIG. 1 is XPS spectra of the modified graphene oxide prepared in examples 1-3 and the graphene oxide prepared in comparative example 2. As can be seen from FIG. 1 (a), the intensity of the O1s peak decreases continuously with increasing reduction, indicating a steady decrease in the oxygen content. In fig. 1 (b) - (e), the main peak at 284.7 eV is assigned to the C-C bond, 285.5 eV is assigned to the C-O bond, 286.8 eV is assigned to the c=o bond, 288.8 eV is assigned to the O-c=o bond. It can be seen that as the degree of reduction increases, the relative intensity of the peak corresponding to the oxygen-containing group of the modified graphene oxide is significantly lower than the relative intensity of the C peak, particularly the peaks of c=o and C-O. The O/C ratio is extracted from XPS spectrum, the unmodified graphene oxide GO prepared in comparative example 2 is 0.44, the modified graphene oxide rGO-1 prepared in example 1 is 0.24, the modified graphene oxide rGO-2 prepared in example 2 is 0.19, and the modified graphene oxide rGO-3 prepared in example 3 is 0.18, which shows that the modified graphene oxide rGO with different oxygen-containing functional groups is successfully prepared.
Fig. 2 shows the vulcanization curves of the natural rubber composites, and table 2 summarizes the vulcanization characteristics of the natural rubber composites. The addition of unmodified graphene oxide prepared in comparative example 2 prolonged scorch time (t s2 ) And vulcanization time (t) c90 ) The vulcanization reaction is delayed, and the vulcanization of the rubber is suppressed. However, the scorch time and vulcanization time of the natural rubber vulcanizate were reduced by the incorporation of the modified graphene oxide rGO prepared in examples 1-3, indicating that the modified graphene oxide rGO prepared in examples 1-3 is capable of promoting vulcanization of the natural rubber vulcanizate. The reason is that: unmodified graphene oxide GO prepared in comparative example 2 shows weak acidity on surface, and natural rubber sulfurThe activators and accelerators in the rubber-melting system are adsorbed by the polar oxygen-containing groups abundant on their surface, resulting in reduced chemical crosslinking of the prepared natural rubber composite GO/NR. The modified graphene oxide rGO prepared in the embodiment 1-3 can be used as a reaction point for physical crosslinking of the natural rubber, so that the crosslinking rate of the natural rubber vulcanized rubber can be improved. In the crosslinking reaction, the faster crosslinking speed and higher vulcanization rate index (CRI) can enable the rubber phase to adsorb the vulcanization aid through various mechanisms such as acid-base action, hydrogen bond or charge transfer, and a stronger crosslinking network is formed. In Table 2, the maximum torque (M H ) The value increases with the addition of rGO with a higher degree of reduction. After further analysis, it was found that the minimum torque and the maximum torque (M H -M L ) The torque difference between them also increases significantly with increasing reduction of added rGO. These all indicate that the modified graphene oxide with effectively regulated and controlled surface oxygen-containing functional groups can lead to the increase of the crosslinking density of the natural rubber composite material and the further development of a crosslinking network.
TABLE 2 vulcanization characteristics of Natural rubber composite of examples and comparative examples
FIG. 3 is a relaxation time curve of a prepared natural rubber vulcanizate with optimized mechanical, low heat generation, and abrasion resistance properties. By LF-NMR test, a relaxation hysteresis curve of H atom vibration in an organic molecular chain can be obtained first. The relaxation time and the content of the soft and hard segments in the rubber can be obtained by data inversion. Since in the hard segments the rubber is more limited by the cross-linked network and the relaxation time is shorter, the relaxation time of the soft segments of rubber is larger and their sum of peak areas is 100%. With the addition of rGO with increased reduction degree prepared in examples 1-3, the relaxation time corresponding to the hard rubber segment is continuously reduced, the peak area ratio is continuously increased, and the interface effect between the filler and the rubber is continuously enhanced, so that the crosslinked network is continuously perfected.
FIG. 4 is a cross-linking density of the prepared natural rubber vulcanizate with mechanical, low heat generation and wear resistance properties optimized simultaneously. Compared with comparative examples 1 and 2, the crosslinking density of the composite materials prepared in examples 1-3 is obviously improved, and the crosslinking density of the rubber composite material is increased and the crosslinking network is more perfect along with the increase of the rGO reduction degree, namely the decrease of the number of oxygen-containing functional groups on the surface of the modified graphene oxide.
FIG. 5 is a DSC curve of a prepared natural rubber vulcanizate with optimized mechanical, low heat generation, and abrasion resistance properties. DSC testing can determine the interaction formed between the natural rubber matrix and the GO filler, as the presence of the filler typically results in a change in the glass transition temperature of the elastomeric compound. The multi-properties prepared in examples 1-3 while optimizing the natural rubber vulcanizates had slightly increased glass transition temperature values compared to comparative examples 1 and 2 due to the increased interactions between the filler and the natural rubber macromolecular chains and the increase in the crosslinked network limiting the movement of the rubber segments. This is the same as the tendency of the crosslink density to increase.
Fig. 6 (a) shows a typical stress-strain curve of a natural rubber vulcanizate with mechanical, low heat generation and wear resistance properties optimized simultaneously. In comparative example 1, when the strain is lower than 700%, the stress of the pure natural rubber is slowly increased; but when the strain reaches 700%, its stress increases sharply until the specimen cracks. This is due to strain induced crystallization of the pure natural rubber chains in the direction of stress during stretching. In comparative example 2 and examples 1 to 3, as the filler is added to the natural rubber, the strain inducing crystallization is shifted to a low strain direction. In example 3, when 1 part of the prepared modified graphene oxide rGO-3 was added, the induced crystallization strain of rGO-3/NR was 550%. This is mainly due to the high interfacial interactions between rGO and NR caused by the strongly crosslinked network, which weaken the entanglement between NR molecular chains, allowing the molecular chains to orient and crystallize in the stretched state.
To better analyze the interaction between the filler and the matrix, the Mooney-Rivlin equation was used to evaluate the multi-properties while optimizing the stress-strain curve of the natural rubber vulcanizate. It is represented by equation (1).
Wherein: delta is the tensile strength during measurement divided by the stress of the undeformed sample cross section, lambda is the elongation of the deformed sample divided by the length of the undeformed sample, C 1 And C 2 Is a constant of two materials, independent of lambda. The resulting curves are shown to be "U" shaped, with the upward shift of the Mooney-Rivlin curve indicating enhanced interaction between the filler and the rubber matrix, useful for assessing limited extensibility of the rubber chain and interfacial adhesion between the filler and the matrix. FIG. 6 (b) shows that with the addition of the prepared modified graphene oxide rGO with higher reduction degree, the inflection point of the curve rises to a larger lambda -1 The multi-performance prepared in examples 1-3 is illustrated, and the interface effect between the filler and the rubber in the natural rubber vulcanized rubber is optimized.
The natural rubber vulcanizates obtained in examples and comparative examples were tested for heat generation, abrasion, and mechanical properties. The heat generating performance test standard is GB/T1687.1-2016, the abrasion performance test standard is GB/T9867-2008, the mechanical performance test standard is ISO 37-2005, and the stretching rate is 500 mm/min. The results of the performance test are shown in Table 3.
TABLE 3 mechanical, heat generating and abrasion resistance test results of Natural rubber vulcanizates prepared in examples 1-3 and comparative examples 1-2
As can be seen from Table 3, the natural rubber vulcanized rubber prepared by the invention has the characteristics of low abrasion, small compression heat generation and excellent mechanical properties, and has the mechanical properties, low heat generation and wear resistance.
Claims (6)
1. The simple method for simultaneously optimizing the mechanical property, low heat generation and wear resistance of the graphene modified natural rubber vulcanized rubber is characterized in that firstly, the number of oxygen-containing functional groups on the surface of a graphene oxide sheet layer is reduced through a simple modification process which is easy for industrial production, and then the graphene modified natural rubber vulcanized rubber with simultaneously optimized mechanical property, low heat generation and wear resistance is prepared by utilizing a water phase synergistic coagulation process and a mechanical blending method; the aqueous phase synergistic coagulation process and the mechanical blending method can uniformly disperse the modified graphene oxide with the reduced number of the surface oxygen-containing functional groups in the natural rubber vulcanized rubber, and the modified graphene oxide with the reduced number of the surface oxygen-containing functional groups can effectively reduce the adsorption of the graphene on the vulcanization aid in the natural rubber composite material system, so that the crosslinking rate and the vulcanization rate of the natural rubber composite material can be improved, the crosslinking density of the natural rubber vulcanized rubber is increased, the crosslinking network is more perfect, and the graphene modified natural rubber vulcanized rubber with simultaneously optimized mechanical, low heat generation and wear resistance properties is obtained;
the method comprises the following steps:
(1) adding a reducing agent into water, fully dissolving, adding graphene oxide aqueous dispersion, and reacting for a certain time at a certain temperature to obtain modified graphene oxide aqueous dispersion with effectively reduced surface oxygen-containing functional groups;
(2) preparing modified graphene oxide/natural rubber masterbatch by a water phase synergetic coagulation process: adding deionized water into natural latex, adding modified graphene oxide aqueous dispersion, and fully mixing to obtain uniformly dispersed mixed emulsion; adding flocculant, the modified graphene oxide particles and rubber particles in natural latex can be mutually adsorbed by pi-pi acting force, so that raw rubber is obtained by orderly gathering and co-precipitation in a water phase; washing the obtained raw rubber with water, removing water and drying to obtain modified graphene oxide/natural rubber masterbatch;
(3) preparation of graphene modified natural rubber vulcanized rubber with optimized mechanical, low heat generation and wear resistance performance: sequentially adding an anti-aging agent, an antioxidant, an activating agent and a softening agent into the modified graphene oxide/natural rubber masterbatch prepared in the step (2), banburying, and uniformly dispersing to obtain a rubber compound; adding a vulcanization accelerator and a vulcanizing agent into the rubber compound, then carrying out open mixing, after mixing uniformly, thinning until the rubber compound is bubble-free, standing for a certain time, placing the rubber compound in a mold, and vulcanizing for a certain time at a certain temperature and a certain pressure to obtain graphene modified natural rubber vulcanized rubber with simultaneously optimized mechanical, low heat generation and wear resistance properties;
the proportion of the raw materials is as follows: 100 parts by mass of natural rubber, 0.1-5 parts by mass of modified graphene oxide particles and 11-13 parts by mass of rubber auxiliary agent;
in the step (1), the reducing agent is at least one of hydrazine hydrate, ascorbic acid, lithium aluminum hydride, iodine and sodium bisulphite; the reaction temperature is 60-120 ℃ and the reaction time is 2-6h; the concentration of the obtained modified graphene oxide aqueous dispersion liquid is 0.5-10 mg.mL -1 。
2. The method according to claim 1, wherein in the step (2), the flocculant is at least one of a calcium chloride solution, a sodium chloride solution, a potassium chloride solution, a sodium sulfate solution, a hydrochloric acid solution, and a formic acid solution.
3. The method according to claim 1, wherein deionized water is added to the natural latex in the step (2) to make the concentration of the natural latex emulsion 10-40 wt%, the concentration of the flocculant is 10 wt% and the mass ratio of the flocculant to the natural rubber is 2-6:100.
4. The method for simplifying the mechanical properties, low heat generation and wear resistance of a graphene modified natural rubber vulcanized rubber simultaneously according to claim 1, wherein in the step (3), the mass ratio of the anti-aging agent, the antioxidant, the activator, the softener, the vulcanization accelerator and the vulcanizing agent is 1:1:5:2:2:2.
5. The method for simplifying the mechanical properties, low heat generation and wear resistance of a graphene modified natural rubber vulcanizate according to claim 1, wherein in step (3), the vulcanization accelerator is N-tert-butyl-2-benzothiazole sulfenamide, N-cyclohexyl-2-benzothiazole sulfenamide or N- (ethylene oxide) -2-benzothiazole sulfenamide; the vulcanizing agent is sulfur or sulfur monochloride; the anti-aging agent is 2, 6-di-tert-butyl-4-methylphenol, 2, 4-trimethyl-1, 2-dihydroquinoline polymer or 2-thiol benzimidazole; the antioxidant is N-isopropyl-N' -phenyl p-phenylenediamine, p-phenylaniline or dilauryl sulfurate; the activator is zinc gluconate, zinc oxide or magnesium oxide; the softening agent is stearic acid, dibutyl titanate or dioctyl adipate.
6. The method for simplifying the mechanical property, low heat generation and wear resistance of the graphene modified natural rubber vulcanized rubber simultaneously and optimally according to claim 1, wherein in the step (3), the mixing temperature of an internal mixer is 105-120 ℃, and the mixing time is 3-5min; the open mill temperature is 50-70 ℃ and the open mill time is 8-12min; the parking time of the rubber compound is 18-36h; the vulcanization temperature is 135-170 ℃, the vulcanization pressure is 10-30MPa, and the vulcanization time is 10-25min.
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