Preparation method of ODH synergistic GO modified cellulose fiber / rubber composite material

Abstract

The invention relates to the technical field of rubber production, and discloses a preparation method of an ODH synergistic GO modified cellulose fiber / rubber composite material. The preparation method comprises the following steps: (1) treating cellulose fibers with acetone to remove impurities, and drying for later use; (2) adding the dried cellulose fibers into the graphene oxide aqueous dispersion to prepare CFG; (3) adding CFG into the ODH / ethanol solution, adding a condensing agent, and reacting to obtain ODH and GO modified cellulose fibers; and (4) mixing the ODH and GO modified cellulose fibers with natural rubber to prepare the composite material. The chemical coupling effect of ODH enhances the interface bonding of cellulose and GO, and more importantly, chemical bond connection is established between a rubber matrix and a cellulose / GO reinforced phase, so that the interface slippage is greatly reduced, and the stress transfer efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of rubber production technology, specifically to a method for preparing ODH-synergistic GO-modified cellulose fiber / rubber composite material. Background Technology

[0002] Natural rubber (NR) plays an important role in industries such as tires and seals due to its excellent elasticity, abrasion resistance, and processability. However, unreinforced natural rubber has low mechanical strength, and although traditional reinforcing fillers such as carbon black can improve performance, their non-renewable nature and the high pollution of the production process restrict sustainable development.

[0003] Cellulose fiber (CF), as a green and renewable resource, possesses high specific strength and biodegradability, making it an ideal alternative to traditional fillers. The addition of CF can significantly improve the tensile strength and modulus of natural rubber, giving it better load-bearing capacity and resistance to deformation. However, the abundant hydroxyl groups on the CF surface lead to poor dispersibility and weak interfacial bonding in non-polar rubber matrices, making it prone to aggregation and severely limiting its reinforcing effect. Therefore, developing efficient modification technologies to improve the interfacial properties of CF / NR composites is of great significance for promoting the green transformation of the rubber industry. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for preparing ODH-synergistic GO-modified cellulose fiber / rubber composite material.

[0005] To achieve the above objectives, the technical solution of the present invention is: a method for preparing ODH-synergistic GO-modified cellulose fiber / rubber composite material, comprising the following steps:

[0006] (1) Remove impurities from cellulose fibers by treating them with acetone and then dry them for later use;

[0007] (2) The dried cellulose fibers from step (1) were added to an aqueous dispersion of graphene oxide at pH 11. After being kept in a constant temperature oil bath at 60-80°C for 1-3 hours, the cellulose fibers were removed, rinsed with water, and then vacuum dried at 60-80°C to obtain graphene oxide modified cellulose fibers, which were named CFG.

[0008] (3) Prepare an ODH / ethanol solution by mixing ODH and anhydrous ethanol, then add the CFG prepared in step (2) to the ODH / ethanol solution and add a condensing agent, stir and modify the reaction, filter with deionized water after the reaction, and then dry at 60-80℃ to obtain ODH-synergistic graphene oxide modified cellulose fiber.

[0009] (4) Preparation of composite material: Add the ODH-co-modified cellulose fiber with graphene oxide obtained in step (3) to a mixer and mix with natural rubber. Then add ZnO, SAD, antioxidant and half of the carbon black, press down the top plug and mix. Then add the remaining carbon black and mix. Lift the plug to release the air, press down the top plug to maintain pressure and mix. Discharge the mixed rubber. Pass the mixed rubber through a two-roll mill. After the rubber compound is wrapped around the roller, add S and accelerator NS. Cut with left and right cutter 3 times, make triangular wrap 3 times, and roll 3 times. Cut into sheets to obtain ODH-co-modified cellulose fiber / rubber composite material, named ODH-CFG.

[0010] Further; in step (1), cellulose fibers are added to a 50% mass concentration acetone solution at a volume ratio of 1:10, ultrasonically cleaned for 0.5 to 1 hour at an ultrasonic frequency of 60 to 80 Hz to remove impurities from the surface of the cellulose fibers, and then filtered three times with deionized water and vacuum dried at 60 to 80 ℃ for later use.

[0011] Further; in step (2), the mass concentration of the graphene oxide aqueous dispersion is 0.5-5 g / L, and the mass-volume ratio of the cellulose fiber to the graphene oxide aqueous dispersion is (20-30) g: 100 mL.

[0012] Further; in step (3), ODH and anhydrous ethanol are mixed at a mass-volume ratio of (2.5-15) g: 500 mL, and ultrasonically emulsified for 20 min at a frequency of 72 Hz to prepare an ODH / ethanol solution.

[0013] Further; in step (3), the mass ratio of the graphene oxide modified cellulose fiber to ODH and condensing agent is 5:5:1.

[0014] Further; in step (3), the stirring modification reaction temperature is 40℃, the time is 240min, and the stirring speed is 60r / min.

[0015] Further; step (4) specifically involves: setting the temperature of the three zones of the internal mixer to 90℃ and the rotor speed to 80r / min, adding the ODH-synergistic graphene oxide modified cellulose fiber and natural rubber obtained in step (3) to the internal mixer, mixing for 1 min, then adding ZnO, SAD, antioxidant and half of the carbon black N234, pressing down the top plug and mixing for 1 min 30s, then adding the remaining carbon black N234 and mixing for 1 min, lifting the plug to exhaust the air, pressing down the top plug to maintain pressure until the total internal mixing time is 6 min 30s and the material temperature is 135℃, discharging the mixed rubber, passing the mixed rubber through the open mill, after the rubber compound is wrapped around the roller, adding S and accelerator NS, cutting left and right blades 3 times, making triangular wraps 3 times, and rolling 3 times, and then sheeting to obtain the ODH-synergistic GO modified cellulose fiber / rubber composite material, named ODH-CFG.

[0016] Furthermore, the antioxidant is selected from antioxidant RD and antioxidant 4020.

[0017] Furthermore, the mass ratio of the natural rubber, carbon black N234, ODH synergistic graphene oxide modified cellulose fiber, ZnO, SAD, antioxidant RD, antioxidant 4020, S, and accelerator NS is 100∶30∶5∶5∶1∶3∶1.5∶0.55∶1.5.

[0018] The beneficial effects of this invention are as follows: Graphene oxide (GO) achieves physical adsorption and interfacial bonding by forming multiple hydrogen bonds with the hydroxyl groups of cellulose fibers through its abundant oxygen-containing functional groups (such as hydroxyl, carboxyl, and epoxy groups). This process does not require chemical cross-linking and mainly relies on the polarity matching between the two-dimensional sheet structure of GO and the surface of cellulose fibers to form a stable physical adsorption layer. Subsequently, the grafting of oxalohydrazide (ODH) is completed through the condensation reaction between the active amino groups at the ends of its molecules and the carboxyl groups on the surface of GO: under the catalysis of the condensing agent, the carboxyl groups of GO are activated to form an active ester intermediate, which undergoes a nucleophilic substitution reaction with the amino groups of ODH to generate amide bonds, thereby covalently grafting ODH onto the surface of GO-modified cellulose fibers. Since cellulose itself lacks aldehyde groups, the grafting sites of ODH depend on the carboxyl groups of GO, which requires that the degree of oxidation of GO be sufficiently high to provide sufficient reaction sites. The free hydrazide group at the other end of the grafted ODH molecule serves as an active site, playing a crucial role in the subsequent composite process with natural rubber (NR). The aldehyde group at the end of the NR molecular chain and the hydrazide group of ODH form a stable hydrazone bond (-NH-N=CH-) through a Schiff base reaction, thereby constructing a covalent bridging network between the cellulose / GO composite and the rubber matrix. The introduction of GO enhances the rigidity of cellulose through its high specific surface area and mechanical strength; its two-dimensional structure creates a physical barrier effect in the rubber matrix, inhibiting crack propagation. The chemical coupling effect of ODH not only strengthens the interfacial bonding between cellulose and GO, but more importantly, establishes chemical bonds between the rubber matrix and the cellulose / GO reinforcing phase, significantly reducing interfacial slip and improving stress transfer efficiency. The thermal conductivity of GO helps disperse heat accumulation in the composite material during dynamic deformation, while the flexible segments of ODH alleviate interfacial stress concentration. Attached Figure Description

[0019] Figure 1 These are cross-sectional scanning electron microscope images. (a) CF, (c) ODH-CF1, (e) ODH-CF2, (g) ODH-CF3, (i) ODH-CF4, (k) ODH-CFG, and (b), (d), (f), (h), (j), and (l) are high-magnification images of (a), (c), (e), (g), (i), and (k), respectively.

[0020] Figure 2 These are the infrared spectra of CF, ODH-CF1, and ODH-CFG;

[0021] Figure 3 These are Payne effect diagrams, (a) loss modulus-strain curves, and (b) comparison of loss modulus differences.

[0022] Figure 4 The physical and mechanical properties are (a) tensile strength and hardness, (b) stress at a given elongation and reinforcing factor, (c) elongation at break and tensile product, and (d) springback.

[0023] Figure 5 It is a graph of the friction coefficient;

[0024] Figure 6 It shows the three-dimensional morphology of the surface before and after wear;

[0025] Figure 7 It is the change in wear volume;

[0026] Figure 8 The dynamic mechanical properties are shown in the following diagrams: (a) DMA curve, (b) magnified view of tanδ peak value, (c) magnified view of 0℃ region, and (d) magnified view of 60℃ region. Detailed Implementation

[0027] Example 1:

[0028] A method for preparing ODH-synergistic GO-modified cellulose fiber / rubber composite material includes the following steps:

[0029] (1) Add cellulose fibers to a 50% mass concentration acetone solution at a volume ratio of 1:10, ultrasonically clean for 0.5 h at an ultrasonic frequency of 72 Hz to remove impurities from the surface of the cellulose fibers, then filter with deionized water 3 times, and place in a vacuum drying oven at 80 ℃ for later use.

[0030] (2) Add 20g of the dried cellulose fiber from step (1) to 100mL of graphene oxide aqueous dispersion with a mass concentration of 5g / L (adjust the pH to 11 with NaOH), and after 2h in a constant temperature oil bath at 60℃, take out the cellulose fiber, rinse it with water, and then vacuum dry it at 60℃ to obtain graphene oxide modified cellulose fiber, named CFG.

[0031] (3) Mix 15g ODH with 500mL anhydrous ethanol and sonicate for 20min at a frequency of 72Hz to prepare an ODH / ethanol solution. Then, according to the mass ratio of CFG to ODH and condensing agent of 5:5:1, add the CFG prepared in step (2) to the ODH / ethanol solution and add the condensing agent. Stir and modify the reaction at a temperature of 40℃ for 240min and a stirring speed of 60r / min. After the reaction, filter the solution repeatedly with deionized water 3 times and then dry it at 80℃ to obtain ODH-synergistic graphene oxide modified cellulose fiber.

[0032] (4) Internal mixing: Set the temperature of the three zones of the internal mixer to 90℃ and the rotor speed to 80r / min. Add 5phr of ODH-synergistic graphene oxide modified cellulose fiber and 100phr of natural rubber obtained in step (3) to the internal mixer and mix for 1min. Then add 5phr of ZnO, 1phr of stearic acid SAD, 3phr of antioxidant RD, 1.5phr of antioxidant 4020 and 15phr of carbon black N234. Press down the top plug and mix for 1min 30s. Then add 15phr of carbon black N234 and mix for 1min. Lift the plug to exhaust the air and press down the top plug to maintain the pressure until the total internal mixing time is 6min 30s and the material temperature is 135℃. Discharge the mixed rubber and cool it to room temperature.

[0033] (5) Open milling: The open mill temperature is set to 45℃, the speed to 60r / min, and the roll gap to 0.5mm. The compound is passed through a thin stream until the surface is smooth and the rolls are wrapped around the rubber. At this point, 0.55phr of sulfur S and 1.5phr of accelerator NS are added. The mixture is then compounded on the open mill by cutting the rubber compound three times to the left and right, forming a triangular wrap three times, and rolling it three times to complete the vulcanization system mixing.

[0034] Set the open mill temperature to room temperature, speed to 60 r / min, and roll gap to 0.1 mm. Feed the compound into the thin-walled mill, passing it through the mill in the same direction each time to ensure that all CF fibers are oriented axially. Gradually increase the roll gap with each pass until the roll gap is 3 mm, then unload the sheet to obtain an axially oriented compound (ODH synergistic GO modified cellulose fiber / rubber composite material), named ODH-CFG.

[0035] Comparative Example 1:

[0036] A method for preparing an ODH-modified cellulose fiber / rubber composite material includes the following steps:

[0037] (1) Same as step (1) in Example 1.

[0038] (2) Mix 2.5g ODH with 500mL anhydrous ethanol and sonicate for 20min at 72Hz to prepare an ODH / ethanol solution. Then, add 5g of the dried cellulose fiber from step (1) to the ODH / ethanol solution and mix well. Then, place the mixture in an oil bath for constant temperature stirring at 60r / min, 80℃, and 90min. Filter the modified CF repeatedly with deionized water three times to ensure that unreacted ODH is washed away. Place the filtered ODH-modified CF in a tray and dry it in an 80℃ oven for later use.

[0039] (3) Intensive mixing: The difference from step (4) in Example 1 is that the ODH-co-modified cellulose fiber is replaced with the ODH-modified CF dried and prepared in step (2) above.

[0040] (4) Open milling: Same as step (5) in Example 1, to obtain ODH-modified cellulose fiber / rubber composite material, named ODH-CF1. Comparative Example 2:

[0041] A method for preparing an ODH-modified cellulose fiber / rubber composite material, differing from Comparative Example 1 in that the amount of ODH added in step (2) is 5g. The resulting ODH-modified cellulose fiber / rubber composite material was named ODH-CF2. Comparative Example 3:

[0042] A method for preparing an ODH-modified cellulose fiber / rubber composite material, differing from Comparative Example 1 in that the amount of ODH added in step (2) is 10g. The resulting ODH-modified cellulose fiber / rubber composite material was named ODH-CF3. Comparative Example 4:

[0043] A method for preparing an ODH-modified cellulose fiber / rubber composite material, differing from Comparative Example 1 in that the amount of ODH added in step (2) is 15g. The resulting ODH-modified cellulose fiber / rubber composite material was named ODH-CF4. Comparative Example 5:

[0044] A method for preparing a cellulose fiber / rubber composite material,

[0045] (1) Same as step (1) in Example 1.

[0046] (2) Intensive mixing: The difference from step (4) in Example 1 is that the ODH-synergistic graphene oxide modified cellulose fiber is replaced with the dried cellulose fiber in step (1).

[0047] (3) Opening: Same as step (5) in Example 1, to obtain cellulose fiber / rubber composite material, named 5phrCF.

[0048] The performance of ODH-CFG, ODH-CF1, ODH-CF2, ODH-CF3, ODH-CF4, and 5phrCF vulcanized samples prepared in Example 1 and Comparative Examples 1 to 5 was measured.

[0049] Vulcanization: The composite material sample was allowed to stand for 12 hours to relieve stress. The positive vulcanization time t of the vulcanized rubber was measured using a rotorless rheometer at a temperature of 150℃ for 60 minutes. 90 To ensure the anisotropy of the fibers in the rubber matrix, an automatic slicing machine was used to cut the fibers along their orientation direction, minimizing secondary orientation during vulcanization. The vulcanizing machine temperature was set to 150℃, the pressure to 10MPa, and the vulcanization time to 1.3 × t. 90 .

[0050] Fourier transform infrared spectroscopy (FTIR) was performed on cellulose fibers ground and compressed using potassium bromide. The FTIR spectrometer was a Thermo-Fisher-Scientific IS-500 model operating at 400 to 4000 cm⁻¹. -1 The samples were tested within the wavenumber range.

[0051] Payne effect test: Using the RPA2000 rubber dynamic processing analyzer from Alpha Corporation (USA), under the condition of keeping the test frequency and temperature constant, the strain amplitude was changed to test the change of the dynamic properties of the rubber with shear rate. This was used to characterize the interaction between the filler and rubber inside the composite material and the degree of filler network structure, reflecting the degree of filler dispersion in the composite material. Approximately 6g of sample was taken, and the test conditions were set as follows: test temperature 60℃, test frequency 0.01Hz, strain range 0.28%-40%, and the change in storage modulus ΔG′ was calculated.

[0052] Mechanical property testing: Mechanical properties were tested using an Instron 3365 universal testing machine according to GB / T 528-2009 and GB / T 529-2008. Dumbbell-shaped tensile specimens and right-angled tear specimens were used. Data such as tensile modulus at a given elongation at break, tensile strength, and tear strength were measured.

[0053] Hardness test: The hardness of the sample was tested using a Shore Hardmeter (H17A) manufactured by Wallace Ltd., UK, in accordance with standard GB / T 231.1-2008.

[0054] Rebound test: The rubber rebound tester (SS-8350ED) manufactured by Taiwan Songshu Testing Instruments Co., Ltd. was used to conduct the test in accordance with the national standard GB / T 1681-1991. The rebound coefficient was taken as the average value of three tests.

[0055] DIN Abrasion Test: The abrasion resistance of the samples was tested according to GB / T 9867-2008 using a 5643-D roller abrasion tester from Taiwan Songshu Testing Instruments Co., Ltd. Approximately 3g of sample was placed in a vulcanization mold to form a cylindrical test specimen. The test conditions were set as follows: roller speed 40r / min.

[0056] Olympus 3D morphology analysis test: Before and after the test, the sample adhesive surface was laser scanned using the LEXTOLS5000 Olympus 3D scanner, and the surface morphology, volume change and roughness change of the sample were analyzed.

[0057] Anton Paar Multifunctional Friction Coefficient Test: Sheet-like rubber samples were cut into circular specimens with a diameter of approximately 100 mm. Before the experiment, the CSM friction and wear testing machine was calibrated, and then the parameters were set. The experimental temperature was set to room temperature (25℃), the pressure to 2 N, the rotation speed to 40 r / min, the friction time to 40 min, and the friction wear radius to 26 mm. For each test group, the grinding metal heads were made of the same type of stainless steel. The frequency for acquiring the friction coefficient was set to 1 Hz. During the experiment, the testing machine could acquire instantaneous friction speed and generate a friction coefficient curve.

[0058] DMA Dynamic Mechanical Property Testing: A GABO GABOMETER-150 dynamic thermomechanical analyzer (Germany) was used in tensile mode to test the stress-strain relationship changes of the sample rubber compound under conditions such as temperature variations. Test specimens were cut using a cutting tool, and the test conditions were set as follows: test frequency 10Hz, static strain 5%, static stress 70N, dynamic strain 0.25%, dynamic stress 60N, test temperature range -65℃ to 65℃, and heating rate 2℃ / min.

[0059] Scanning electron microscopy (SEM) testing: Using a JSM-7500F scanning electron microscope manufactured by Nippon Electronics Corporation, a suitable sample of vulcanized rubber sheet was cut and subjected to low-temperature brittle fracture in liquid nitrogen. The sample was then attached to the sample stage and sputtered with gold. The cross-sectional morphology of the fractured vulcanized rubber sheet was observed and photographed. Based on the microscopic photographs of different vulcanized rubbers, the dispersion state of the filler in the vulcanized rubber was analyzed.

[0060] Micromorphology

[0061] Figure 1Images (a) through (j) are electron microscope (EM) images of the cross-sectional structures of cellulose fibers (CF) and NR composites reinforced with CF and different proportions of ODH, respectively. From the low-magnification images (a), (c), (e), (g), and (i), it can be seen that as the proportion of ODH gradually increases, the dispersion of CF in the NR matrix gradually improves. The cross-section of the NR composite shows fewer voids at the CF-matrix interface, a rough fiber surface, and a thin layer of rubber coating, indicating that ODH enhances the CF-NR interfacial compatibility. From the high-magnification images… Figure 4-2 As can be seen from 5(b)(d)(f)(h)(j), an ODH coating gradually forms on the surface of CF. As the proportion of ODH increases, a glue-coating phenomenon appears on the fiber surface. This is because the hydroxyl groups on the CF surface undergo a covalent grafting reaction with the hydrazide groups of ADH. This not only reduces the polarity of the fiber surface and weakens the hydrogen bond aggregation effect, allowing CF to be uniformly dispersed in the rubber matrix in the form of single fibers, but also forms covalent crosslinks with the NR molecular chains through the active groups (such as amino groups) at the ends of the ODH molecules. Figure 1 Figures (k) and (l) are cross-sectional views of GO-co-ODH modified CF / NR composites. In the cross-section after co-modification, CF is uniformly dispersed and has a rough surface. GO sheets are tightly wrapped around the fiber surface or embedded in the matrix in a wrinkled manner. The fiber-NR matrix interface is blurred and there are no signs of debonding. This indicates that ODH improves CNF dispersion and interfacial compatibility through covalent bonds, while GO enhances the interfacial mechanical interlocking through high specific surface area and two-dimensional structure.

[0062] Infrared spectroscopy

[0063] Depend on Figure 2 It can be observed that at 1030cm -1 At this point, the broad peak of CF transforms into a sharp, strong peak with a width of 922 cm. -1 up to 1110cm -1 This indicates that ODH undergoes a condensation reaction with the hydroxyl group in CF via the hydrazide group (-NH-NH2) to generate an amide group (-CO-NH-), which leads to a local change in the CF molecular chain. Simultaneously, the vibration of the CN bond in ODH expands the absorption range. The new peak at 1377 cm⁻¹ is attributed to the stretching vibration of the CN bond in ODH and the stretching vibration of the -CH2 group in CF; the peak at 1531 cm⁻¹... -1 and 1638cm -1 The new peaks appearing at 2960 cm⁻¹ represent the C=O stretching vibrations of the amide II and amide I bands, respectively, proving the successful construction of the amide bond between ODH and CF. Furthermore, the peak at 2960 cm⁻¹... -1 and 2930cm -1 The CH stretching vibration peak at 3000 cm⁻¹ is significantly enhanced, indicating that the grafting of ODH disrupts the crystallization region of CF; simultaneously, the introduction of alkyl chains in ODH also enhances the CH peak intensity. -1 ~3500cm-1 Within the range, 3315cm -1 A sharp, strong peak appeared at that point, along with 3200cm on both sides. -1 and 3442cm -1 The broad peak. Among them, 3315cm... -1 The main peak at this location corresponds to the strong hydrogen bonding vibration of NH, indicating that the hydrazide group forms a stable covalent bond with the hydroxyl group of CF through the hydrazide bond. The peaks at 3200 cm⁻¹ on both sides... -1 and 3442cm -1 The broadened shoulder peaks correspond to strong hydrogen bond / chemically bonded NH and weak hydrogen bond / free NH, respectively, revealing the formation of the hydrogen bond network of NH in the modified interface.

[0064] Payne effect

[0065] Depend on Figure 3 It can be observed that the ΔG' of the unmodified 5phrCF group is 205.9 kPa, significantly higher than other groups, indicating a significant network effect of the filler. CF is prone to agglomeration and physical cross-linking points due to the hydrogen bonding of polar hydroxyl groups. With the increase of ODH ratio, ΔG' decreases sequentially to 170.63, 162.38, 124.24, and 113.78 kPa, showing a clear linear decreasing trend. This is because the hydrazide group in ODH undergoes a condensation reaction with the hydroxyl groups of CF to form amide bonds. The introduction of amide bonds not only reduces the polarity of the CF surface but also introduces flexible ODH long chains. Its steric hindrance effect effectively inhibits the physical entanglement between CFs, thereby improving dispersibility. When the ratio of ODH to CF reaches 3:1, ΔG' reaches the lowest value of 113.78 kPa, indicating that the high-density ODH forms a coating layer on the CF surface, further weakening the filler-filler interaction.

[0066] When the ODH-GO synergistic modification system was adopted, the ΔG' of ODH-CFG reached 121.85 kPa. Although the value of ΔG' increased, it was due to... Figure 3 (a) It can be observed that the storage modulus curve of ODH-CFG shifts upward overall and has the smallest slope. This phenomenon can be explained by the fact that the two-dimensional layered structure of GO forms a physical coating layer on the CF surface through hydrogen bonding; at the same time, the oxygen-containing functional groups on the GO surface undergo a secondary condensation reaction with the hydrazide groups of ODH, which improves the interfacial bonding performance and also enhances the rigidity of the composite material through GO, thus constructing a CF-GO-ODH ternary interfacial structure. From... Figure 3 (a) It can be observed that although the curve of ODH-CFG did not reach the low modulus level of ODH-CF4, its smoothness was significantly better than all pure ODH modified systems, and its modulus value was higher than that of ODH-CF3, achieving a balance between dispersibility and rigidity.

[0067] Physical and mechanical properties

[0068] Table 1 Physical and mechanical properties of CF-filled NR composites modified with ODH and GO at different proportions

[0069]

[0070] Depend on Figure 4 As shown in Table 1, the tensile strength of the unmodified 5phrCF was 24.69 MPa. However, as the ratio of ODH to CF increased to 1:1, the tensile strength increased to 29.18 MPa, an increase of 18.2% compared to the 5phrCF group. This indicates that ODH significantly optimized the interfacial bonding between CF and the NR matrix through chemical grafting. The hydrazide groups in the ODH molecule react with the hydroxyl groups on the cellulose surface to form a stable covalent bond network, which not only reduces fiber aggregation and improves dispersion but also enhances the rigidity of the composite material through interfacial stress transfer. With the addition of a higher proportion of ODH, the tensile strengths of ODH-CF3 and ODH-CF4 decreased to 28.32 MPa and 27.01 MPa, respectively. This may be because excessive ODH caused excessive cross-linking on the fiber surface, resulting in excessively high interfacial rigidity and sacrificing flexibility. Meanwhile, the 100% elongation stress and 300% elongation stress of ODH-CF2 were 2.57 MPa and 11.20 MPa, respectively, while the elongation stress of ODH-CF4 was significantly reduced, further illustrating that excessive crosslinking leads to a decrease in the material's ability to resist deformation under large strain. When GO and ODH were synergistically modified into CF, the tensile strength of ODH-CFG reached 30.26 MPa, an increase of 22.6% compared to 5 phr CF, while the 300% elongation increased to 11.83 MPa, and the springback rate increased from 64.2% of 5 phr CF to 78.7%. This is because the hydrazide group of ODH reacts chemically with the carboxyl groups on the GO surface to construct a CF-GO-ODH network. This synergistic modification inhibits the aggregation tendency of GO and CF and enhances the interfacial bonding strength between CF and the NR matrix. Although the elongation at break of ODH-CFG is lower than that of ODH-CF4, its tensile product, which characterizes toughness, is 16016.7, which is close to that of ODH-CF3. This means that the introduction of GO achieves optimization of comprehensive mechanical properties by significantly improving tensile strength while slightly sacrificing the elongation at break.

[0071] Friction coefficient

[0072] Various samples were tested in an aqueous medium using a zirconia grinding head on a CSM tribometer. The resulting friction curves, after approaching stability, are as follows: Figure 5 As shown in Table 2, the average friction coefficient is obtained by averaging the stabilized friction coefficient curves.

[0073] Table 2 Average friction coefficient of ODH synergistic GO modified CF / NR composite material

[0074]

[0075] Combination Figure 5 It can be seen that with the increase of ODH, the average friction coefficient of the CF / NR composite material decreases overall. After ODH modification, the hydroxyl groups on the surface of cellulose fibers chemically bond with the hydrazide groups in the ODH molecule, forming a stable interfacial transition layer. This strong interfacial bonding can inhibit the tendency of fiber to peel off from the matrix during friction, reduce the propagation of microcracks caused by interfacial debonding, and thus reduce the probability of curling wear. When the ratio of ODH to CF is 1:1, the average friction coefficient reaches the lowest value, while beyond this ratio, the average friction coefficient shows a slight upward trend. When GO is used in conjunction with ODH to modify CF, the ODH-CFG group reaches the lowest value of 0.1135. This is attributed to the relative slippage generated by the two-dimensional lamellar structure of GO under stress and the synergistic effect with the interfacial chemical bonds, which enables the fiber to effectively block the adhesive slippage of the rubber molecular chains. At the same time, the rigid skeleton shares the radial load, thereby transforming the cracks caused by curling wear into a form dominated by slight abrasive wear.

[0076] Surface wear

[0077] Depend on Figure 6 and Figure 7 It can be seen that the wear amount of the unmodified group 5phrCF is 3211692.5μm. 3 The three-dimensional morphology of the worn surface showed deep and continuous furrows and microcracks, indicating weak bonding between the fiber and rubber interface. Under frictional stress, the fibers were prone to peeling off from the matrix, forming defects that led to stress concentration and crack propagation. After ODH modification, the hydroxyl groups on the cellulose fiber surface formed chemical bonds with ODH, enhancing the fiber-rubber interface bonding. The wear amount of ODH-CF1 was 1378303.2 μm. 3 The wear amount of ODH-CF2 is 1,161,499.5 μm. 3 The presence of shallow furrows and dispersed microcracks indicates that the modified fibers form a more uniform three-dimensional skeletal structure within the matrix. When the ODH modification ratio is increased to 2:1, the wear amount of ODH-CF3 is 1132956.9 μm. 3 The worn surface tends to be smooth with only a few shallow scratches, indicating that the fiber skeleton network has reached the optimal density and the fibers form a continuous interlocking structure in the matrix. This structure can both limit the excessive deformation of the rubber macromolecular chains through rigid support and prevent fiber sliding displacement through strong interfacial bonding.

[0078] wear resistance

[0079] Table 3. Wear resistance properties of CF-filled NR composites with different proportions of ODH synergistic with GO modification.

[0080]

[0081] Table 3 shows that the DIN abrasion of unmodified 5phrCF is 0.1255 and the Akron abrasion is 0.2415, while the abrasion of CF modified by ODH gradually decreases, with ODH-CF3 achieving the best DIN and Akron abrasion levels. The GO and ODH synergistic modification group ODH-CFG further reduced the DIN and Akron abrasion to 0.0738 and 0.1273, respectively. This phenomenon indicates that unmodified CF, due to its high surface polarity, is unevenly dispersed in the NR matrix, and its interface is easily peeled off during friction, resulting in increased wear. ODH, through the chemical grafting of hydrazide groups with cellulose hydroxyl groups, reduces the fiber surface polarity, improves its compatibility with rubber, and simultaneously enhances the interfacial bonding force through covalent bonds, enabling the fiber to be uniformly dispersed in the rubber and form a continuous three-dimensional skeletal network. When the ODH ratio increases from 2:1 (ODH-CF1) to 1:2 (ODH-CF3), fiber dispersion and interfacial bonding are gradually optimized, and the support of the skeleton structure for the rubber matrix is ​​enhanced, which can more effectively resist shear force and tensile stress during the wear process and delay crack propagation. The synergistic modification of CF by ODH and GO enhances the wear resistance of the NR matrix through physical adsorption and chemical grafting. The high specific surface area and rigid structure of GO nanosheets strengthen the mechanical interlocking between the fiber and the rubber. The reaction of the hydrazide groups of ODH with the carboxyl groups on the GO surface enhances the interfacial bonding performance, allowing the fibers to form a more ordered skeleton structure when radially oriented (perpendicular to the grinding wheel). This reduces abrasive embedding through rigid support and also inhibits the initiation and propagation of fatigue cracks through interfacial slip.

[0082] Dynamic mechanical properties

[0083] pass Figure 8 As shown in (a) and 8(b), the unmodified 5phrCF group has poor filler dispersibility due to hydrogen bond aggregation initiated by surface hydroxyl groups, with a tanδ peak value of 1.2078, which limits the reinforcing effect. However, as the ODH ratio increases from 2:1 in the ODH-CF1 group to 1:2 in the ODH-CF3 group, the tanδ peak value gradually increases to 1.39684. This is because the hydrazide group in the ODH molecule and the hydroxyl group on the CF surface undergo a grafting reaction, which effectively reduces the fiber polarity and inhibits hydrogen bond aggregation. When the ODH to CF ratio reaches 2:1, the reaction on the CF surface approaches saturation. At this time, ODH constructs a chemical cross-linking network at the fiber-rubber interface, reducing the loss modulus caused by interfacial friction.

[0084] When CF was synergistically modified with ODH and GO, the highest tanδ peak value was observed, reaching 1.58125. This is because the two-dimensional structure and high specific surface area of ​​GO not only prevent the formation of hydrogen bonds between CF molecules, but also facilitate chemical grafting of amino groups and rubber molecular chains from ODH, resulting in a more uniform stress distribution in the CF / NR matrix. After CF was synergistically modified with ODH and GO, the tanδ value at 60℃ of the ODH-CFG group was reduced by 62.5% compared to the unmodified 5phr group, indicating that the nano-barrier effect of GO and the chemical coupling of ODH synergistically achieved lower heat generation.

[0085] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

[0086] In the description of this invention, it should be understood that the terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings and are only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

Claims

1. A method for preparing an ODH-synergistic GO-modified cellulose fiber / rubber composite material, characterized in that, Includes the following steps: (1) Remove impurities from cellulose fibers by treating them with acetone and then dry them for later use; (2) The dried cellulose fibers from step (1) were added to an aqueous dispersion of graphene oxide at pH 11. After being kept in a constant temperature oil bath at 60-80°C for 1-3 hours, the cellulose fibers were removed, rinsed with water, and then vacuum dried at 60-80°C to obtain graphene oxide modified cellulose fibers, which were named CFG. (3) Prepare an ODH / ethanol solution by mixing ODH and anhydrous ethanol, then add the CFG prepared in step (2) to the ODH / ethanol solution and add a condensing agent, stir and modify the reaction, filter with deionized water after the reaction, and then dry at 60-80℃ to obtain ODH-synergistic graphene oxide modified cellulose fiber. (4) Preparation of composite material: Add the ODH-co-modified cellulose fiber with graphene oxide obtained in step (3) to a mixer and mix with natural rubber. Then add ZnO, SAD, antioxidant and half of the carbon black, press down the top plug and mix. Then add the remaining carbon black and mix. Lift the plug to release the air, press down the top plug to maintain pressure and mix. Discharge the mixed rubber. Pass the mixed rubber through a two-roll mill. After the rubber compound is wrapped around the roller, add S and accelerator NS. Cut with left and right cutter 3 times, make triangular wrap 3 times, and roll 3 times. Cut into sheets to obtain ODH-co-modified cellulose fiber / rubber composite material, named ODH-CFG.

2. The method for preparing ODH-synergistic GO-modified cellulose fiber / rubber composite material according to claim 1, characterized in that: In step (1), cellulose fibers are added to a 50% mass concentration acetone solution at a volume ratio of 1:10, and ultrasonically cleaned for 0.5 to 1 hour at an ultrasonic frequency of 60 to 80 Hz to remove impurities from the surface of the cellulose fibers. Then, the fibers are filtered three times with deionized water and vacuum dried at 60 to 80 ℃ for later use.

3. The method for preparing ODH-synergistic GO-modified cellulose fiber / rubber composite material according to claim 1, characterized in that: In step (2), the mass concentration of the graphene oxide aqueous dispersion is 0.5-5 g / L, and the mass-volume ratio of the cellulose fiber to the graphene oxide aqueous dispersion is (20-30) g: 100 mL.

4. The method for preparing ODH-synergistic GO-modified cellulose fiber / rubber composite material according to claim 1, characterized in that: In step (3), ODH and anhydrous ethanol are mixed at a mass-volume ratio of (2.5-15) g: 500 mL, and ultrasonically emulsified for 20 min at a frequency of 72 Hz to prepare an ODH / ethanol solution.

5. The method for preparing ODH-synergistic GO-modified cellulose fiber / rubber composite material according to claim 1, characterized in that: In step (3), the mass ratio of the graphene oxide modified cellulose fiber to ODH and condensing agent is 5:5:

1.

6. The method for preparing ODH-synergistic GO-modified cellulose fiber / rubber composite material according to claim 1, characterized in that: In step (3), the stirring modification reaction temperature is 40℃, the time is 240min, and the stirring speed is 60r / min.

7. The method for preparing ODH-synergistic GO-modified cellulose fiber / rubber composite material according to claim 1, characterized in that: Step (4) is as follows: Set the temperature of the three zones of the internal mixer to 90℃ and the rotor speed to 80r / min. Add the ODH-co-modified cellulose fiber and natural rubber obtained in step (3) to the internal mixer and mix for 1 min. Then add ZnO, SAD, antioxidant and half of the carbon black N234. Press down the top plug and mix for 1 min 30s. Then add the remaining carbon black N234 and mix for 1 min. Lift the plug to exhaust the air. Press down the top plug to maintain the pressure until the total internal mixing time is 6 min 30s and the material temperature is 135℃. Discharge the mixed rubber. Pass the mixed rubber through the open mill. After the rubber compound is wrapped around the roller, add S and accelerator NS. Cut the left and right blades 3 times, make the triangular wrap 3 times, and roll 3 times. Cut the sheet to obtain the ODH-co-modified cellulose fiber / rubber composite material, named ODH-CFG.

8. The method for preparing ODH-synergistic GO-modified cellulose fiber / rubber composite material according to claim 7, characterized in that: The antioxidant is selected from antioxidant RD and antioxidant 4020.

9. The method for preparing ODH-synergistic GO-modified cellulose fiber / rubber composite material according to claim 8, characterized in that: The mass ratio of the natural rubber, carbon black N234, ODH synergistic graphene oxide modified cellulose fiber, ZnO, SAD, antioxidant RD, antioxidant 4020, S, and accelerator NS is 100:30:5:5:1:3:1.5:0.55:1.5.

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