A modified graphene oxide-nylon composite material, a preparation method and use thereof

Abstract

The application provides a modified graphene oxide-nylon composite material and a preparation method and application thereof. The application carries out amidation reaction on graphene oxide and a binary amine capped by an amino protecting group to prepare amidated graphene oxide; then removes the amino protecting group to prepare aminated graphene oxide; then carries out reduction treatment on the aminated graphene oxide and ascorbic acid to prepare modified graphene oxide; finally carries out polymerization reaction on the modified graphene oxide and monomers for preparing nylon, avoids crosslinking of an epoxy group or a carboxyl group and a binary amine, solves the problems of poor dispersibility and weak binding force of the modified graphene oxide and a nylon matrix, effectively improves the mechanical properties and conductive properties of the nylon, so that the modified graphene oxide-nylon composite material with high conductivity, good flexibility and stability is prepared, and the use requirements of wearable electronic devices under dynamic conditions such as bending and stretching are met.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a modified graphene oxide-nylon composite material, its preparation method, and its applications. Background Technology

[0002] The rapid development of wearable electronic devices has created an urgent need for flexible conductive materials, which must simultaneously satisfy good conductivity, mechanical flexibility, and biocompatibility. Nylon 66, as an engineering plastic with excellent comprehensive properties, possesses high strength, good flexibility, and processability, making it an ideal choice for preparing flexible substrates. However, Nylon 66 is an insulator and has almost no conductivity when unmodified.

[0003] Graphene possesses excellent electrical and mechanical properties, but its surface lacks reactive sites and it is prone to agglomeration during use. Graphene oxide, on the other hand, contains abundant oxygen-containing functional groups, making surface modification easier. When copolymerized with nylon 66, it can form strong chemical bonds, facilitating stress transfer. However, the oxidation of graphene (i.e., graphene oxide) destroys its inherent conductivity, requiring reduction treatment to obtain graphene and restore its conductivity.

[0004] The study also found that the terminal carboxyl groups on graphene oxide compete with adipic acid for hexamethylenediamine during copolymerization with monomers used to prepare nylon 66, which inhibits the molecular weight of nylon 66 formed during copolymerization. To obtain high molecular weight nylon 66, diamine compounds are usually added to the system of graphene oxide blended or copolymerized with nylon to prepare composite materials. However, the two ends of diamine compounds are more likely to react with the more reactive epoxy groups on graphene oxide to obtain a cross-linked three-dimensional network. This results in no terminal amino groups forming chemical bonds with nylon, and the performance transfer can only rely on hydrogen bonds formed between amino groups and amide groups in nylon. This leads to inherent defects in the blending or copolymerization process, such as weak bonding and low degree of modification (inability to form or only a small amount of amide bonds). Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a modified graphene oxide-nylon composite material, its preparation method, and its applications. This invention involves reacting a diamine with a single-end amino protecting group capped with graphene oxide in a mild and rapid manner to prepare amidated graphene oxide. Then, the amidated graphene oxide is subjected to deamino protecting group treatment and ascorbic acid reduction treatment to prepare modified graphene oxide (specifically, an amidated graphene structure with most oxygen-containing groups removed). The modified graphene oxide is then used as a monomer in the polycondensation reaction of nylon, covalently binding the modified graphene oxide to the main chain and / or side chains of nylon. This avoids crosslinking of the epoxy or carboxyl groups on the graphene oxide surface with the diamine, solving the problems of poor dispersibility and weak bonding between the modified graphene oxide and the nylon matrix. This effectively improves the mechanical and electrical properties of nylon, thus preparing a modified graphene oxide-nylon composite material with high conductivity, good flexibility, and stability, meeting the usage requirements of wearable electronic devices under dynamic conditions such as bending and stretching.

[0006] The objective of this invention is achieved through the following technical solution: A method for preparing a modified graphene oxide-nylon composite material includes the following steps: (1) Graphene oxide, solvent, condensing agent, basic reagent and diamine with amino protecting group single end capping are mixed and reacted under nitrogen atmosphere to prepare amidated graphene oxide. (2) The amidated graphene oxide from step (1) is subjected to deamination treatment to obtain aminated graphene oxide. (3) The aminated graphene oxide from step (2) and ascorbic acid were mixed and reduced to prepare modified graphene oxide. (4) Mix the diamine, dicarboxylic acid and deionized water to form a solution for preparing the monomer salt; (5) The modified graphene oxide from step (3) and the monomer salt solution from step (4) are mixed, and a prepolymerization reaction is carried out first, followed by a polymerization reaction to prepare the modified graphene oxide-nylon composite material.

[0007] According to an embodiment of the present invention, in step (1), the graphene oxide is prepared by a method known in the art or obtained through commercial purchase, and the present invention does not have any particular limitation on this.

[0008] According to an embodiment of the present invention, in step (1), the solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile and N-methylpyrrolidone.

[0009] According to an embodiment of the present invention, in step (1), the condensing agent is selected from at least one of 2-(7-azabenzotriazole-1-yl)-N,N,N',N'-tetramethylurea hexafluorophosphate, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1-hydroxybenzotriazole, O-benzotriazole-tetramethylurea hexafluorophosphate, and dicyclohexylcarbodiimide; preferably, the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1-hydroxybenzotriazole are used in combination.

[0010] According to an embodiment of the present invention, in step (1), the alkaline reagent is selected from N,N-diisopropylethylamine and / or triethylamine.

[0011] According to an embodiment of the present invention, in step (1), the structural formula of the diamine with one end capped by the amino protecting group is shown in Formula 1: RNH-R1-NH2 Equation 1; In Equation 1, R1 is substituted or unsubstituted C 1-12 Alkylene; if substituted, the substituent is C. 1-12 Alkyl group; R is an amino protecting group selected from at least one of benzyloxycarbonyl (Cbz), tert-butoxycarbonyl (Boc), 9-fluorenylmethoxycarbonyl (Fmoc) or allyloxycarbonyl (Alloc).

[0012] Preferably, R1 is substituted or unsubstituted C. 2-8 Alkylene; if substituted, the substituent is C. 1-6 Alkyl; and more preferably, R1 is a substituted or unsubstituted C 2-6 Alkylene; if substituted, the substituent is C. 1-3 alkyl.

[0013] According to an embodiment of the present invention, in step (1), the amino-protecting diamine is selected from at least one of ethylenediamine, propylenediamine, butanediamine, hexamethylenediamine, and octanediamine; the amino protecting group is selected from at least one of benzyloxycarbonyl (Cbz), tert-butyloxycarbonyl (Boc), 9-fluorenylmethoxycarbonyl (Fmoc), and allyloxycarbonyl (Alloc); exemplaryly, the amino-protecting diamine is selected from ethylenediamine with tert-butyloxycarbonyl (Boc) single-end capping.

[0014] According to an embodiment of the present invention, in step (1), the diamine with the amino protecting group single-end capped is prepared by a method known in the art or obtained through commercial purchase, and the present invention does not have any particular limitation on this.

[0015] According to an embodiment of the present invention, in step (1), the equivalent of 1 is calculated based on the carboxyl content in graphene oxide, and the equivalent ratio of graphene oxide to condensing agent is 1:1.2-1.5, for example, 1:1.2, 1:1.3, 1:1.4 or 1:1.5, so as to ensure that all the carboxyl groups in graphene oxide can be reacted.

[0016] According to an embodiment of the present invention, in step (1), the equivalent of graphene oxide is 1 equivalence, and the equivalent ratio of graphene oxide to alkaline reagent is 1:3-5, for example, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5.

[0017] According to an embodiment of the present invention, in step (1), the equivalent of 1 is calculated based on the carboxyl content in graphene oxide, and the equivalent ratio of the graphene oxide to the amino-protected diamine is 1:2-10, for example, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10.

[0018] According to an embodiment of the present invention, in step (1), the mixing may first mix graphene oxide and solvent, and then perform ultrasonic dispersion to obtain graphene oxide dispersion; subsequently, a condensing agent, an alkaline reagent and a diamine with a single-end capped amino protecting group are added to the graphene oxide dispersion.

[0019] According to an embodiment of the present invention, in step (1), the temperature of the reaction is 20-60°C, for example 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C; the reaction time is 12-48 hours, for example 24 hours or 36 hours; the reaction is carried out under stirring conditions.

[0020] According to an embodiment of the present invention, in step (1), during the reaction process, the carboxyl group (-C(=O)-OH) on the surface of graphene oxide undergoes an amidation reaction (-C(=O)-NH-R1-NHR) with a diamine (NH2-R1-NHR) with a single-end capped amino protecting group to prepare amidated graphene oxide.

[0021] According to an embodiment of the present invention, in step (1), after the reaction is completed, post-processing steps such as filtration, washing, and drying are also included.

[0022] According to an embodiment of the present invention, in step (2), the amino protecting group can be removed using a method known in the art for deamination treatment; exemplary, any of the following methods can be used for deamination treatment: (2-1) If the amino protecting group is benzyloxycarbonyl (Cbz), the amidated graphene oxide is dispersed in a polar solvent, a palladium on carbon (Pd / C) catalyst is added, the air in the reaction system is replaced with hydrogen 3-5 times, and the reaction is stirred for 1-12 hours under a hydrogen atmosphere. The mixture is then filtered, washed, and dried to obtain the amidated graphene oxide. The polar solvent is selected from at least one of methanol, ethanol, and N,N-dimethylformamide; the mass-to-volume ratio of the amidated graphene oxide to the polar solvent is 0.5-5 mg / mL; the amount of the palladium on carbon (Pd / C) catalyst is 5wt%-20wt% of the total mass of the amidated graphene oxide, for example, 5wt%, 10wt%, 15wt%, or 20wt%; the stirring temperature is room temperature; and the stirring pressure is greater than 0.1 MPa, for example, 0.12 MPa-0.15 MPa.

[0023] (2-2) If the amino protecting group is tert-butoxycarbonyl (Boc), the amidated graphene oxide is mixed with dichloromethane, and trifluoroacetic acid is added dropwise at room temperature. After the addition is complete, the mixture is stirred at room temperature for 20-60 min, filtered, washed, and dried to obtain aminated graphene oxide. The mass-to-volume ratio of the amidated graphene oxide to dichloromethane is 1-5 mg / mL, for example, 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, or 5 mg / mL; the volume ratio of dichloromethane to trifluoroacetic acid is 0.8-1.2:1, for example, 0.8:1, 0.9:1, 1:1, 1.1:1, or 1.2:1.

[0024] (2-3) If the amino protecting group is 9-fluorenylmethoxycarbonyl (Fmoc), first prepare a mixed solution of piperidine and DMF with a volume fraction of 20%, then add the amidated graphene oxide to it, stir the reaction at room temperature for 5-30 min, filter, wash, and dry to obtain aminated graphene oxide. The mass-to-volume ratio of the amidated graphene oxide to the mixed solution is 0.5-5 mg / mL, for example, 0.5 mg / mL, 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, or 5 mg / mL.

[0025] (2-4) If the amino protecting group is allyloxycarbonyl (Alloc), the amidated graphene oxide is dispersed in dichloromethane; morpholine and tetrakis(triphenylphosphine)palladium [Pd(PPh3)4] catalyst are added, and the reaction is carried out under nitrogen protection at room temperature with stirring for 0.5-5 hours. After filtration, washing, and drying, the amidated graphene oxide is obtained. The mass-to-volume ratio of the amidated graphene oxide to dichloromethane is 1-5 mg / mL, for example, 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, or 5 mg / mL; the mass ratio of the amidated graphene oxide to morpholine is not specifically defined, as long as the amount of morpholine added is in excess; the amount of tetrakis(triphenylphosphine)palladium [Pd(PPh3)4] is 5-10 mol of the molar amount of the amino protecting group in the amidated graphene oxide.

[0026] According to an embodiment of the present invention, in step (2), during the deamination process, the diamine (-C(=O)-NH-R1-NHR) grafted on the surface of graphene oxide undergoes deamination to prepare aminated graphene oxide (-C(=O)-NH-R1-NH2).

[0027] According to an embodiment of the present invention, in step (3), the temperature of the reduction treatment is 80-100°C, for example, 80°C, 85°C, 90°C, 95°C or 100°C; the time of the reduction treatment is 6-24 hours, for example, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours; the mass ratio of ascorbic acid to aminated graphene oxide is 1:1-6:1, for example, 1:1, 2:1, 3:1, 4:1, 5:1 or 6:1.

[0028] According to an embodiment of the present invention, in step (3), the aminated graphene oxide from step (2) is dispersed in deionized water, ascorbic acid is added, and the mixture is reduced at 80-100°C for 6-24 hours. After cooling, the mixture is filtered, washed alternately with deionized water and ethanol, and dried to prepare modified graphene oxide.

[0029] According to an embodiment of the present invention, in step (3), during the ascorbic acid reduction treatment, most of the oxygen-containing groups (such as hydroxyl groups, epoxy groups, etc.) on the surface of the aminated graphene oxide are reduced to carbon-carbon single bonds and / or carbon-carbon double bonds to prepare modified graphene oxide.

[0030] According to an embodiment of the present invention, in step (4), the diamine is selected from diamines that can be copolymerized with dicarboxylic acids to prepare nylon; preferably, the diamine is selected from aliphatic linear diamines with 6-12 carbon atoms; exemplaryly, the diamine is selected from at least one of acediamine, heptanediamine, octanediamine, decanedanediamine, undecanediamine and dodecanediamine.

[0031] According to an embodiment of the present invention, in step (4), the dicarboxylic acid is selected from dicarboxylic acids that can be copolymerized with diamines to prepare nylon; preferably, the dicarboxylic acid is selected from aliphatic linear dicarboxylic acids with 6-12 carbon atoms; exemplaryly, the dicarboxylic acid is selected from at least one of picric acid, heptanic acid, octanoic acid, sebacic acid, undecanoic acid and dodecanoic acid.

[0032] According to an embodiment of the present invention, in step (4), the molar ratio of the diamine and the dicarboxylic acid is 1:1.

[0033] According to an embodiment of the present invention, in step (4), the mixing temperature is 40-50°C, for example 40°C, 45°C or 50°C.

[0034] According to an embodiment of the present invention, in step (4), the sum of the mass of the diamine and the dicarboxylic acid in the preparation of the monomer salt solution accounts for 30-70 wt% of the total mass of the preparation of the monomer salt solution, for example, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt% or 70 wt%.

[0035] According to an embodiment of the present invention, in step (5), the amount of modified graphene oxide added is 0.05-1 wt% of the sum of the mass of the diamine and the dicarboxylic acid, for example, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt% or 1 wt%.

[0036] According to an embodiment of the present invention, in step (5), the temperature of the prepolymerization reaction is 220-240°C, for example, 220°C, 225°C, 230°C, 235°C or 240°C; the time of the prepolymerization reaction is 0.5-1.5 hours; and the pressure of the prepolymerization reaction is 2.3-2.7 MPa, for example, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.6 MPa or 2.7 MPa.

[0037] According to an embodiment of the present invention, in step (5), the temperature of the polymerization reaction is 260-280°C, for example, 260°C, 265°C, 270°C, 275°C or 280°C; the time of the polymerization reaction is 0.5-1.5 hours; and the pressure of the polymerization reaction is -0.04MPa to -0.08MPa.

[0038] According to the embodiment of the present invention, in step (5), after the prepolymerization reaction is completed, the reactor for the prepolymerization reaction is depressurized to atmospheric pressure (water vapor will be discharged during the depressurization process), and then the temperature of the reactor is raised to 260-280°C. Then the vacuum system is turned on and the reactor is evacuated to a pressure of -0.04MPa to -0.08MPa, and the polymerization reaction is continued for 0.5-1.5 hours. After the polymerization reaction is completed, nitrogen is introduced until the pressure inside the reactor reaches 0.1MPa, and the material is discharged.

[0039] According to an embodiment of the present invention, in step (5), after the polymerization reaction is completed, post-processing steps such as discharging, pelletizing, and vacuum drying are also included.

[0040] The present invention also provides a modified graphene oxide-nylon composite material prepared by the above preparation method.

[0041] According to an embodiment of the present invention, the modified graphene oxide-nylon composite material comprises modified graphene oxide and nylon.

[0042] According to an embodiment of the present invention, the modified graphene oxide accounts for 0.05-1 wt% of the total mass of the modified graphene oxide-nylon composite material, for example, 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, 0.5 wt%, 0.55 wt%, 0.6 wt%, 0.65 wt%, 0.7 wt%, 0.75 wt%, 0.8 wt%, 0.85 wt%, 0.9 wt%, 0.95 wt%, or 1 wt%.

[0043] According to an embodiment of the present invention, the nylon accounts for 99-99.95 wt% of the total mass of the modified graphene oxide-nylon composite material, for example, 99 wt%, 99.05 wt%, 99.1 wt%, 99.15 wt%, 99.2 wt%, 99.25 wt%, 99.3 wt%, 99.35 wt%, 99.4 wt%, 99.45 wt%, 99.5 wt%, 99.55 wt%, 99.6 wt%, 99.65 wt%, 99.7 wt%, 99.75 wt%, 99.8 wt%, 99.85 wt%, 99.9 wt%, or 99.95 wt%.

[0044] According to an embodiment of the present invention, the nylon is selected from nylons known in the art; exemplary, the nylon is selected from at least one of nylon 66, nylon 610, nylon 612, nylon 1010, nylon 46, nylon 56 and nylon 510. According to an embodiment of the present invention, the nylon is grafted onto the surface of modified graphene oxide via chemical bonds (such as amide bonds).

[0045] The present invention also provides the use of the above-described modified graphene oxide-nylon composite material in the field of wearable electronic devices.

[0046] The beneficial effects of this invention are: This invention provides a modified graphene oxide-nylon composite material, its preparation method, and its applications. The invention involves an amidation reaction of graphene oxide with a diamine end-capped by an amino protecting group to prepare amidated graphene oxide; then, the amino protecting group is removed to prepare aminated graphene oxide; next, it is mixed with ascorbic acid for reduction treatment to prepare modified graphene oxide; finally, the modified graphene oxide and monomers (diamine and dicarboxylic acid) for preparing nylon are polymerized. During the polymerization reaction, the terminal carboxyl groups of the dicarboxylic acid react with the terminal amino groups on the surface of the modified graphene oxide to prepare a copolymer composite material with the main chain and / or side links branched on the modified graphene oxide sheets.

[0047] Specifically, this invention prepares amidated graphene oxide via a mild and efficient amide condensation process. By introducing an amino protecting group at one end of a diamine, the cross-linking of the diamine with the epoxy or carboxyl groups on the graphene oxide surface, which would otherwise lead to the formation of a self-assembled three-dimensional network, is avoided, thus improving the dispersibility and interfacial interaction between the modified graphene oxide and the nylon matrix. This invention also restores the good conductivity of the aminated graphene oxide to the modified graphene oxide through ascorbic acid reduction. Furthermore, this invention uses in-situ polymerization to connect the modified graphene oxide and nylon via amide bonds. This strong interfacial interaction greatly enhances stress transfer between the two, allowing the good properties of the modified graphene oxide to migrate to the nylon, improving the mechanical strength of the composite material. The resulting composite material exhibits higher impact strength, tensile strength, flexural strength, and superior conductivity; the composite material can be used in wearable electronic devices. This invention significantly improves the mechanical and electrical properties of nylon by adding only a very small amount (0.05-1 wt%) of modified graphene oxide, at a low cost and easy for industrial production. Attached Figure Description

[0048] Figure 1 The present invention is a flow chart illustrating the preparation process of a modified graphene oxide-nylon composite material according to a preferred embodiment of the present invention. Detailed Implementation

[0049] The preparation method of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0050] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0051] Example 1 Step 1): Add 5g of graphene oxide to 5L of N,N-dimethylformamide and sonicate for 2 hours. Add 4.28g of 2-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethylurea hexafluorophosphate in an ice-water bath and stir for 1 hour. Add 5.2mL of triethylamine and stir for 1 hour. Add 4.8g of N-Boc-ethylenediamine (Boc-NH-C2H4-NH2) and stir at 40℃ for 24 hours. Filter, wash, and dry to obtain amidated graphene oxide. Step 2): Add an appropriate amount of dichloromethane to the amidated graphene oxide from Step 1), and sonicate it in an ice-water bath to form a uniform dispersion of 1 mg / mL. Slowly add an equal volume of trifluoroacetic acid to the dichloromethane at room temperature. After the addition is complete, continue stirring at room temperature for 30 min. Filter, wash, and vacuum dry to obtain aminated graphene oxide. Step 3:) Disperse aminated graphene oxide in deionized water, add ascorbic acid (mass ratio of ascorbic acid to aminated graphene oxide is 4:1), carry out reduction reaction at 95℃ for 8 hours, cool and filter, wash and dry alternately with deionized water and ethanol to obtain modified graphene oxide. Step 4): Prepare modified graphene oxide-nylon 66 composite material by salting 1107g of hexamethylenediamine and 1393.3g of adipic acid in 2500.3g of deionized water at 50℃. The sum of the mass concentrations of hexamethylenediamine and adipic acid is 50%. 5g of modified graphene oxide was added to the above salt solution and stirred to obtain a uniformly dispersed liquid. The liquid was then added to a 5L high-temperature and high-pressure reactor. After three positive and three negative pressure nitrogen purgings, the reactor contained 0.04MPa of nitrogen. The reactor was heated to 230℃ and 2.5MPa for prepolymerization for 1 hour. After the prepolymerization reaction, the reactor was depressurized to atmospheric pressure and heated to 280℃. Then, a vacuum was drawn until the reactor pressure was -0.06MPa, and the polymerization reaction continued for 1 hour. After the polymerization reaction, nitrogen was introduced until the reactor pressure reached 0.1MPa. The material was discharged, pelletized, and the pellets were vacuum dried at 120℃ for 12 hours to obtain the modified graphene oxide-nylon composite material.

[0052] Example 2 The only difference from Example 1 is that the N-Boc-ethylenediamine added in step 1) is replaced with N-Boc-butanediamine, and the triethylamine is replaced with N,N-diisopropylethylamine. All other steps are the same as in Example 1.

[0053] Example 3 The only difference from Example 1 is that the N-Boc-ethylenediamine added in step 1) is replaced with N-Boc-hexamethylenediamine; all other steps are the same as in Example 1.

[0054] Example 4 The only difference from Example 1 is that the N-Boc-ethylenediamine added in step 1) is replaced with N-Boc-octanediamine; all other steps are the same as in Example 1.

[0055] Example 5 The only difference from Example 1 is that the N-Boc-ethylenediamine added in step 1) is replaced with N-Boc-butanediamine, and the amount of modified graphene oxide added is 10g. All other steps are the same as in Example 1.

[0056] Example 6 The only difference from Example 1 is that the N-Boc-ethylenediamine added in step 1) is replaced with N-Boc-butanediamine, and the amount of modified graphene oxide added is 15g. All other steps are the same as in Example 1.

[0057] Comparative Example 1 The only difference from Example 1 is that the N-Boc-ethylenediamine added in step 1) is replaced with ethylenediamine, so there is no step 2), and step 3) is performed directly. All other steps are the same as in Example 1.

[0058] Comparative Example 2 The only difference from Example 1 is that the N-Boc-ethylenediamine added in step 1) is replaced with butanediamine, so there is no step 2), and step 3) is performed directly. All other steps are the same as in Example 1.

[0059] Comparative Example 3 The only difference from Example 1 is that the N-Boc-ethylenediamine added in step 1) is replaced with hexamethylenediamine, so there is no step 2), and step 3) is performed directly. All other steps are the same as in Example 1.

[0060] Comparative Example 4 Step 1) Raw material preparation: Before use, Nylon 66 is dried in a vacuum drying oven at 100-110℃ for more than 12 hours until the moisture content is less than 0.2%; Graphene oxide (GO): Use raw graphene oxide without any organic modification, and vacuum dry it at 60℃ for 24 hours before use to remove residual solvent.

[0061] Step 2) Premixing: Weigh 995g of dried nylon 66 granules and 5g of graphene oxide powder, mix them mechanically and then stir them in a high-speed mixer for 5-10 minutes to make the graphene oxide adhere to the surface of the nylon 66 granules as much as possible.

[0062] Step 3) Melt blending: Add the premixed material to a twin-screw extruder for melt blending.

[0063] Step 4) Granulation and Drying: The extruded melt is water-cooled, stretched, and granulated to obtain graphene oxide / nylon 66 composite material granules. The granules are then dried again at 100°C for 8 hours for subsequent testing.

[0064] Table 1 Performance tests of the composite materials prepared in the examples and comparative examples

[0065] 1) Comparing the mechanical properties (tensile strength and flexural strength), we can see that: The comparison of Examples 2, 5 and 6 shows that when the amount of butanediamine-modified graphene oxide added to the composite material is increased from 0.2 wt% to 0.6 wt%, the tensile strength and flexural strength of the composite material first increase and then decrease. When the amount of butanediamine-modified graphene oxide added is 0.4 wt%, the tensile strength and flexural strength of the composite material reach the maximum, indicating that the dispersion of modified graphene oxide in the composite material reaches the best at this time.

[0066] The comparison of Comparative Examples 1, 2, and 3 shows that although the tensile and flexural strengths of the composite materials in Comparative Examples 1-3 are improved compared to pure PA66, the improvement effect is far less than that in Examples 1-3. This is because the diamine added to the composite materials in Comparative Examples 1-3 during the preparation process was not end-group protected. The unprotected diamine formed crosslinks between graphene sheets under the current reaction conditions. Since the crosslinked network aggregates in the matrix of the composite material, the dispersion of graphene oxide is relatively poor, which affects the tensile and flexural strengths of the prepared composite material.

[0067] The comparison of Examples 1, 2, 3 and 4 shows that the larger the number of carbon atoms in the diamine, the better the dispersion of the modified graphene oxide in the composite material. This is because the longer the chain length of the diamine, the more conducive it is to the formation of chain segment entanglement structure and the generation of interfacial strength in the modified graphene oxide in the composite material, which is beneficial to the improvement of the tensile strength and flexural strength of the composite material. Studies have found that the performance of hexamethylenediamine-modified graphene oxide added during the preparation of the composite material of this invention is superior to that of octanediamine-modified graphene oxide. This is mainly because hexamethylenediamine is one of the polymer monomers of nylon 66, and hexamethylenediamine-modified graphene oxide has the strongest chemical compatibility and molecular-level bonding ability with the nylon 66 matrix. After being introduced into the composite material, hexamethylenediamine-modified graphene oxide can achieve the deepest chain segment entanglement structure and generate extremely high interfacial strength, thus achieving the best tensile strength and flexural strength. In contrast, the alkane chain of octanediamine is less similar to that of nylon 66 than that of hexamethylenediamine, and the chain segment entanglement ability and dispersibility of ethylenediamine and butanediamine are weaker than those of hexamethylenediamine and octanediamine. Therefore, the dispersibility of diamine-modified graphene oxide of different chain lengths in the composite material, in descending order, is: hexamethylenediamine (HDA) > octanediamine (DAO) > butanediamine (BDA) > ethylenediamine (EDA).

[0068] 2) Comparing the mechanical properties (elongation at break), it can be seen that long-chain diamines (such as hexamethylenediamine and octanediamine) provide excessively strong and rigid interfacial bonds, restricting the plastic deformation processes such as slippage and orientation of the nylon 66 molecular chains. Short-chain diamines (such as butanediamine and ethylenediamine) have weaker interfacial bonds, thus resulting in higher elongation at break. It is evident that the trend in elongation at break is completely opposite to that of tensile strength and flexural strength.

[0069] 3) Comparison of conductivity properties shows that: From the comparison of Examples 2, 5 and 6, it can be seen that when the amount of butanediamine-modified graphene oxide added to the composite material increases from 0.2wt% to 0.6wt%, the resistivity of the composite material first decreases and then increases. When the amount of butanediamine-modified graphene oxide added is 0.4wt%, the resistivity of the composite material is the lowest, which indicates that the percolation threshold of the composite material is 0.4wt%. This is attributed to the good dispersibility of modified graphene oxide in the composite material.

[0070] The comparison of Comparative Examples 1-3 shows that the resistivity of the obtained composite material is as high as 10. 12 Ω The high resistivity (cm) is due to the fact that the diamines added during the preparation of Comparative Examples 1-3 were not end-protected. Under the current reaction conditions, the unprotected diamines formed crosslinks between the graphene sheets. Because the crosslinked network aggregated in the matrix of the composite material, the formation of conductive pathways in the composite material was blocked, resulting in a resistivity as high as 10⁻⁶. 12 Ω cm.

[0071] The comparison of Examples 1-4 shows that short-chain diamines (such as ethylenediamine and butanediamine) have the advantage of small molecular size and low steric hindrance, which can more effectively prevent graphene sheets from re-stacking during ascorbic acid reduction, resulting in fewer defects and higher sp. 2 Graphene, with its more complete carbon structure repair and higher intrinsic conductivity, and its shorter chains resulting in lower resistance in the conductive pathway between graphene and nylon 66, yields a composite material with lower resistivity. Furthermore, butanediamine-modified graphene oxide exhibits better dispersion in the composite material, resulting in the lowest resistivity. While long-chain diamines (such as hexamethylenediamine and octanediamine) possess excellent dispersibility and compatibility (especially hexamethylenediamine, which shares a similar structure with nylon 66, allows for more uniform and stable dispersion of graphene in the nylon 66 matrix through "like-like compatibility" and "chain segment entanglement" mechanisms), their long chains hinder ascorbic acid reduction, leading to poor intrinsic conductivity. Additionally, long insulating chains significantly increase tunneling resistance, making it difficult for electrons to cross even with good dispersion, resulting in a composite material with higher resistivity.

[0072] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a modified graphene oxide-nylon composite material, wherein, Includes the following steps: (1) Graphene oxide, solvent, condensing agent, basic reagent and diamine with amino protecting group single end capping are mixed and reacted under nitrogen atmosphere to prepare amidated graphene oxide. (2) The amidated graphene oxide from step (1) is subjected to deamination treatment to obtain aminated graphene oxide. (3) The aminated graphene oxide from step (2) and ascorbic acid were mixed and reduced to prepare modified graphene oxide. (4) Mix the diamine, dicarboxylic acid and deionized water to form a solution for preparing the monomer salt; (5) The modified graphene oxide from step (3) and the monomer salt solution from step (4) are mixed, and a prepolymerization reaction is carried out first, followed by a polymerization reaction to prepare the modified graphene oxide-nylon composite material.

2. The preparation method according to claim 1, wherein, In step (1), the condensing agent is selected from at least one of 2-(7-azabenzotriazole-1-yl)-N,N,N',N'-tetramethylurea hexafluorophosphate, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1-hydroxybenzotriazole, O-benzotriazole-tetramethylurea hexafluorophosphate, and dicyclohexylcarbodiimide; And / or, in step (1), the alkaline reagent is selected from N,N-diisopropylethylamine and / or triethylamine; And / or, in step (1), the structural formula of the diamine with the amino protecting group single-end capped is shown in Formula 1: RNH-R1-NH2 Equation 1; In Equation 1, R1 is substituted or unsubstituted C 1-12 Alkylene; if substituted, the substituent is C. 1-12 Alkyl group; R is an amino protecting group selected from at least one of benzyloxycarbonyl (Cbz), tert-butoxycarbonyl (Boc), 9-fluorenylmethoxycarbonyl (Fmoc) or allyloxycarbonyl (Alloc). Preferably, in step (1), the amino-protected diamine is selected from at least one of ethylenediamine, propylenediamine, butanediamine, hexamethylenediamine, and octanediamine; and the amino-protected group is selected from at least one of benzyloxycarbonyl (Cbz), tert-butyloxycarbonyl (Boc), 9-fluorenylmethoxycarbonyl (Fmoc), and allyloxycarbonyl (Alloc).

3. The preparation method according to claim 1 or 2, wherein, In step (1), the equivalent of 1 is calculated based on the carboxyl content in graphene oxide, and the equivalent ratio of graphene oxide to condensing agent is 1:1.2-1.5; And / or, in step (1), the equivalent of 1 is calculated based on the carboxyl content in the graphene oxide, and the equivalent ratio of the graphene oxide to the alkaline reagent is 1:3-5; And / or, in step (1), the equivalent of 1 is calculated based on the carboxyl content in the graphene oxide, and the equivalent ratio of the graphene oxide to the amino-protected single-end capped diamine is 1:2-10. And / or, in step (1), the temperature of the reaction is 20-60°C; the reaction time is 12-48 hours.

4. The preparation method according to any one of claims 1-3, wherein, In step (2), the deamination protecting group treatment is performed using any of the following methods: (2-1) If the amino protecting group is benzyloxycarbonyl (Cbz), the amidated graphene oxide is dispersed in a polar solvent, palladium on carbon (Pd / C) catalyst is added, the air in the reaction system is replaced with hydrogen 3-5 times, the reaction is stirred for 1-12 hours under hydrogen atmosphere, filtered, washed and dried to obtain aminated graphene oxide. (2-2) If the amino protecting group is tert-butoxycarbonyl (Boc), mix the amidated graphene oxide with dichloromethane, add trifluoroacetic acid dropwise at room temperature, and continue stirring at room temperature for 20-60 min after the addition is complete. Filter, wash and dry to obtain aminated graphene oxide. (2-3) If the amino protecting group is 9-fluorenylmethoxycarbonyl (Fmoc), first prepare a mixed solution of piperidine and DMF with a volume fraction of 20%, then add amidated graphene oxide to it, stir the reaction at room temperature for 5-30 min, filter, wash and dry to obtain aminated graphene oxide. (2-4) If the amino protecting group is allyloxycarbonyl (Alloc), the amidated graphene oxide is dispersed in dichloromethane; morpholine and tetrakis(triphenylphosphine)palladium [Pd(PPh3)4] catalyst are added, and the reaction is carried out at room temperature under nitrogen protection for 0.5-5 hours. The mixture is then filtered, washed, and dried to obtain aminated graphene oxide.

5. The preparation method according to any one of claims 1-4, wherein, In step (3), the temperature of the reduction treatment is 80-100℃; the time of the reduction treatment is 6-24 hours; and the mass ratio of ascorbic acid to aminated graphene oxide is 1:1-6:

1.

6. The preparation method according to any one of claims 1-5, wherein, In step (4), the diamine is selected from aliphatic straight-chain diamines with 6-12 carbon atoms; for example, the diamine is selected from at least one of acediamine, heptanediamine, octanediamine, decanedanediamine, undecanediamine and dodecanediamine. And / or, in step (4), the dicarboxylic acid is selected from aliphatic straight-chain dicarboxylic acids having 6-12 carbon atoms; exemplary, the dicarboxylic acid is selected from at least one of anthocyanin, pimelic acid, octanoic acid, sebacic acid, undecanoic acid and dodecanoic acid; And / or, in step (4), the molar ratio of the diamine and the dicarboxylic acid is 1:1; And / or, in step (4), the sum of the masses of the diamine and the dicarboxylic acid in the prepared monomer salt solution accounts for 30-70 wt% of the total mass of the prepared monomer salt solution.

7. The preparation method according to any one of claims 1-6, wherein, In step (5), the amount of modified graphene oxide added is 0.05-1 wt% of the sum of the mass of the diamine and the dicarboxylic acid; And / or, in step (5), the temperature of the prepolymerization reaction is 220-240℃; the time of the prepolymerization reaction is 0.5-1.5 hours; and the pressure of the prepolymerization reaction is 2.3-2.7 MPa. And / or, in step (5), the temperature of the polymerization reaction is 260-280℃; the time of the polymerization reaction is 0.5-1.5 hours; and the pressure of the polymerization reaction is -0.04MPa to -0.08MPa.

8. The modified graphene oxide-nylon composite material prepared by the preparation method according to any one of claims 1-7.

9. The modified graphene oxide-nylon composite material according to claim 8, wherein, The modified graphene oxide-nylon composite material includes modified graphene oxide and nylon. Preferably, the modified graphene oxide accounts for 0.05-1 wt% of the total mass of the modified graphene oxide-nylon composite material, and the nylon accounts for 99-99.95 wt% of the total mass of the modified graphene oxide-nylon composite material. Preferably, the nylon is selected from at least one of nylon 66, nylon 610, nylon 612, nylon 1010, nylon 46, nylon 56 and nylon 510.

10. Use of the modified graphene oxide-nylon composite material according to claim 8 or 9 in the field of wearable electronic devices.

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