CN111303486B

CN111303486B - Amino-terminated modified graphene oxide and epoxy nanocomposite thereof

Info

Publication number: CN111303486B
Application number: CN202010093270.7A
Authority: CN
Inventors: 邹华维; 张雪琴; 梁梅
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2020-02-14
Filing date: 2020-02-14
Publication date: 2021-06-25
Anticipated expiration: 2040-02-14
Also published as: CN111303486A

Abstract

The invention relates to amino-terminated modified graphene oxide and an epoxy nanocomposite thereof. Specifically disclosed is a modified graphene oxide, which is obtained by replacing-OH groups on carboxyl groups on the surface of graphene oxide with A groups, wherein the structure of the A groups is shown as follows; the invention also discloses an epoxy nanocomposite prepared by using the modified graphene oxide as a raw material. The amino-terminated modified graphene oxide prepared by the invention can greatly improve the storage modulus and the glass transition temperature of the epoxy nanocomposite material, improve the rigidity and the heat resistance of the composite material, and obviously improve the mechanical properties, particularly the tensile property, and has excellent comprehensive properties and excellent application prospects.

Description

Amino-terminated modified graphene oxide and epoxy nanocomposite thereof

Technical Field

The invention belongs to the field of polymer composite materials, and particularly relates to amino-terminated modified graphene oxide and an epoxy nanocomposite thereof.

Background

As an important thermosetting resin, the epoxy resin has excellent physical and mechanical properties, electrical insulation, chemical corrosion resistance, heat resistance, adhesive property and molding manufacturability, and is widely applied to the fields of chemical industry, automobiles, electronics, machinery, aerospace and the like. With the rapid development of the modern material science and technology field, higher and higher requirements are put forward on the epoxy resin, and the development trend of the epoxy resin is developed towards multi-functionalization, refinement, high performance and the like. The epoxy resin is one of the most important high-performance composite material matrix resins, has extremely important application value in the field of aerospace, and the high strength, modulus and toughness of the epoxy resin directly influence the performance advantages of the new generation of high-performance fibers, but the high-performance epoxy resin matrix is more and more difficult to obtain by modification methods such as traditional molecular structure design. Therefore, new ideas and methods are needed to obtain a new generation of toughened high-performance epoxy composite matrix material, and develop a higher-performance epoxy resin matrix so as to match with high-performance fibers (carbon fibers, aramid fibers and the like), so that a high-performance resin matrix composite material with excellent comprehensive performance can be prepared.

The biggest weakness of epoxy resin is the three-dimensional cross-linked network structure after curing, which strongly limits the movement of epoxy molecular chains, so that the cured product has high brittleness, poor impact toughness resistance and low stress cracking resistance. Therefore, when used as a resin matrix of a high-performance composite material, it is necessary to improve the toughness of the epoxy resin. However, in general, a method of improving the toughness of a material has a problem of deteriorating the strength, modulus, heat resistance, and the like of the material. Therefore, the high-performance epoxy resin which has high strength, high modulus, high fracture toughness, high heat resistance and excellent processing formability is explored, so that the high-performance epoxy resin is better matched with the high-performance reinforced fiber to prepare the high-performance resin-based composite material, and the high-performance resin-based composite material has important scientific significance and application prospect.

The toughening modification around epoxy resins is mainly achieved by introducing a second phase therein, and a common modification method includes: toughening modification of rubber elastomers and thermoplastic resins, toughening modification of Interpenetrating Polymer Networks (IPNs), toughening modification of Thermotropic Liquid Crystal Polymers (TLCPs), toughening modification of core-shell polymer rubber particles and rigid nanoparticles, and the like. Different strengthening and toughening modification methods have the advantages and inevitable disadvantages, such as: 1. although the rubber elastomer can improve the fracture toughness of the material, the elastic modulus and the heat resistance of the material are inevitably sacrificed, so the rubber elastomer is not suitable for modifying a high-performance epoxy resin matrix; 2. the modulus, heat resistance and the like of the thermoplastic/EP composite system are not obviously reduced, even the modulus, heat resistance and the like are increased to different degrees, but the effect of toughening the epoxy resin is not obvious; 3. the IPNs/EP composite system is mixed at a molecular level, and can inhibit phase separation to the maximum extent, so that the modification effect is obvious, and the improvement mainly shows that the toughness of the modification system is improved, and the tensile strength and the heat resistance of the modification system are not reduced or are slightly improved. However, the preparation process of the method is complex and the process period is long. 4. The TLCP toughened and modified epoxy resin can improve the toughness of a modified system and ensure good mechanical property and heat resistance of the material. However, TLCP is difficult to synthesize, high in production cost, high in heat deformation temperature, difficult to process and poor in matching property with general epoxy resin. 5. Compared with the traditional rubber toughening modification, the CSR particles can improve the toughness of the material while maintaining the heat resistance of the material, but the synthesis and preparation process is complex, and the particle size distribution needs to be controlled more accurately. 6. The rigid nano particles not only can effectively toughen EP, but also can improve the heat resistance of EP due to the unique surface effect and nano size effect. However, nanoparticles have extremely high surface energy and are easily agglomerated, and have poor dispersibility, thereby limiting the application range of the nanoparticles. Therefore, the exploration of a modified epoxy system with high strength, high modulus and high fracture toughness has important application value.

The graphene serving as a novel two-dimensional flaky carbon nano material has extremely high breaking strength and Young modulus; therefore, the composite material is considered as an ideal reinforcement for preparing the polymer-based nano composite material and has wide application prospect in the field of polymer-based nano composite materials. However, as a typical nano reinforcing filler, graphene has a very large specific surface area, so that irreversible agglomeration is very easy to occur in a polymer matrix, and high exfoliation and uniform dispersion are difficult to achieve; secondly, the graphene surface is highly inert and thus has poor interfacial bonding with the polymer resin matrix. In addition, the synthesis and preparation process of graphene is complex, the manufacturing cost is high, and the further application of the graphene in the field of polymer composite materials is limited. Therefore, good dispersion of the nanofiller and proper interfacial interaction between the two phases are of great importance in the preparation of high performance polymer composite resin matrices. The graphene is subjected to efficient surface modification, so that the graphene can be effectively dispersed and stripped, and the advantages of the two-dimensional flaky nano filler are fully exerted. Therefore, the surface of the graphene is modified controllably according to the structural characteristics of the graphene, so that the compatibility between the graphene and an epoxy resin matrix can be improved, the irreversible agglomeration among graphene nanosheets can be reduced, and the stripping degree and the dispersion state of a two-dimensional nano reinforcement in a polymer matrix can be improved. Meanwhile, based on the reactive active sites of the organic matter functional groups grafted on the surface of the graphene, the interaction of two interphase interfaces of the graphene nanosheets and the epoxy resin can be enhanced, and the stress transfer efficiency and the nano-enhancement effect are improved; thereby obviously improving the macroscopic mechanical property of the epoxy resin, preparing a high-performance epoxy nano composite resin matrix with excellent comprehensive performance and further realizing the matching with high-performance fibers.

Therefore, aiming at the molecular structure characteristics of graphene, a reactive group is introduced to the surface of graphene by exploring a high-efficiency graphene surface modification process from the surface structure design of graphene, so that the affinity between graphene and epoxy resin is improved, and the interface bonding strength between the graphene and the epoxy resin is enhanced, so that the high-performance epoxy resin matrix with excellent molding manufacturability and excellent comprehensive performance is prepared, and has important research significance and scientific application value. However, in the prior art, it is difficult to improve the toughness and the mechanical properties and the heat resistance of the modified graphene reinforced epoxy composite material. Therefore, the finding of a simple method for preparing the epoxy composite material with high strength, high modulus, high toughness and high heat resistance and excellent comprehensive performance has very important significance.

Disclosure of Invention

The invention aims to provide amino-terminated modified graphene oxide with excellent comprehensive performance and an epoxy nanocomposite thereof.

The invention provides modified graphene oxide, which is obtained by replacing-OH groups on carboxyl groups on the surface of graphene oxide by A groups; wherein the structure of the A group is:

further, the material is prepared from the following raw materials: graphene oxide4,4 '-diaminodicyclohexylmethane, p-benzene substituted derivatives, 4' -diaminodiphenyl, wherein the ratio of graphene oxide: 4,4' -diaminodicyclohexylmethane: p-benzene substituted derivatives: the ratio of 4,4' -diaminodiphenylmethane was 1 g: (20-40) mmol: (140-160) mmol: (20-40) mmol; the structure of the p-benzene substituted derivative is

R₁、R₂Each independently selected from hydroxy, halogen, preferably hydroxy.

Further, the graphene oxide: 4,4' -diaminodicyclohexylmethane: the proportion of the para-benzene substituted derivative is 1 g: 30mmol: 150 mmol: 30 mmol.

The invention also provides a preparation method of the modified graphene oxide, which comprises the following three steps:

(1) reacting graphene oxide with 4,4' -diaminodicyclohexylmethane to obtain an intermediate product 1;

(2) the intermediate product 1 reacts with a p-benzene substituted derivative to obtain an intermediate product 2;

(3) reacting the intermediate product 2 with 4,4' -diaminodiphenylmethane to obtain modified graphene oxide;

wherein the structure of the intermediate product 1 is obtained by replacing-OH groups on carboxyl groups on the surface of graphene oxide with B groups, and the B groups are

The structure of the intermediate product 2 is obtained by replacing-OH groups on carboxyl groups on the surface of graphene oxide with C groups, wherein the C groups are

Further, in the steps (1), (2) and (3): the raw materials also comprise a catalyst and a dehydrating agent; the method also comprises the following operations after the reaction is finished: carrying out vacuum filtration, and keeping and washing a solid; the reaction temperature is 70-100 ℃; the reaction time is 12-36 hours; the reaction solvent and the washing reagent are respectively and independently selected from one or more of dimethylformamide, dimethylacetamide, tetrahydrofuran and alcohol solvents;

preferably, the catalyst is dimethylaminopyridine, and the dehydrating agent is N, N-dicyclohexylcarbodiimide; the reaction temperature is 90 ℃; the reaction time is 24 hours; the reaction solvent and washing reagent are selected from dimethylformamide.

Further, in the step (1), the mass molar ratio of the graphene oxide to the 4,4' -diaminodicyclohexylmethane, the catalyst and the dehydrating agent is 1 g: (20-40) mmol: (5-15) mmol: (5-15) mmol, preferably 1 g: 30mmol:10mmol:10 mmol;

and/or in the step (2), the mass molar ratio of the graphene oxide to the p-benzene substituted derivative, the catalyst and the dehydrating agent is 1 g: (120-180) mmol: (5-15) mmol: (5-15) mmol, preferably 1 g: 150 mmol:10mmol:10 mmol;

and/or in the step (3), the mass molar ratio of the graphene oxide to the 4,4' -diaminodiphenylmethane, the catalyst and the dehydrating agent is 1 g: (20-40) mmol: (5-15) mmol: (5-15) mmol, preferably 1 g: 30mmol:10mmol:10 mmol.

The invention also provides an epoxy nanocomposite which is prepared from the modified graphene oxide, epoxy resin and a curing agent.

Further, the raw materials comprise the following components in parts by weight: 70 parts of epoxy resin, 29.3 parts of curing agent and 0.0175-0.0875 parts of modified graphene oxide; preferably 70 parts of epoxy resin, 29.3 parts of curing agent and 0.0375-0.0525 parts of modified graphene oxide;

and/or the epoxy resin is alicyclic glycidyl ester epoxy resin; the epoxy value of the alicyclic glycidyl ester epoxy resin is preferably 0.8-0.9, and more preferably 0.85;

and/or the curing agent is an aromatic curing agent, preferably one or two of 4', 4-diaminodiphenylmethane and 3, 5-diethyl-2, 4-toluenediamine, and more preferably an equivalent of a mixed curing agent of 4', 4-diaminodiphenylmethane and 3, 5-diethyl-2, 4-toluenediamine.

The invention also provides a preparation method of the epoxy nanocomposite material, which comprises the following steps:

(a) weighing the modified graphene oxide, ultrasonically dispersing the modified graphene oxide in an organic solvent, adding epoxy resin, and uniformly stirring; then removing the organic solvent;

(b) weighing a curing agent, adding the curing agent into the system obtained in the step (a), uniformly stirring, and then drying in vacuum to remove bubbles;

(c) and (c) pouring the system obtained in the step (b) into a mould, and curing and forming to obtain the composite material.

Further, in step (a), the organic solvent is selected from acetone; the mass volume ratio of the modified graphene oxide to the organic solvent is 1: (0.5-3) mg/mL, preferably 1: 1 mg/mL;

and/or, in step (c), the curing conditions are: 2 hours at (110-130) DEG C, then 3 hours at (140-160) DEG C, and then 1 hour at (170-190) DEG C; preferably: at 120 ℃ for 2h, then at 150 ℃ for 3h, then at 180 ℃ for 1 h.

Experimental results show that the modified graphene oxide C-P-M-GO with rich amino groups on the surface is successfully prepared, and a C-P-M-GO epoxy nanocomposite system is further prepared. The amino-terminated modified graphene oxide prepared by the invention can simultaneously improve the elongation at break, tensile strength, elastic modulus, glass transition temperature and storage modulus of the epoxy nanocomposite material with low addition. Namely, the epoxy nanocomposite material prepared by the invention has the advantages of improved toughness, obviously improved mechanical property, rigidity and heat resistance, excellent comprehensive performance and excellent application prospect. Obviously, many modifications, substitutions, and variations are possible in light of the above teachings of the invention, without departing from the basic technical spirit of the invention, as defined by the following claims.

The present invention will be described in further detail with reference to the following examples. This should not be understood as limiting the scope of the above-described subject matter of the present invention to the following examples. All the technologies realized based on the above contents of the present invention belong to the scope of the present invention.

Drawings

Fig. 1 is an infrared spectrum of modified graphene oxide.

Fig. 2 is a raman spectrum of modified graphene oxide.

Fig. 3 is a thermogravimetric spectrum of modified graphene oxide, in which (a) represents a TGA curve and (b) represents a DTG curve.

FIG. 4 is a microscopic morphology of cross sections of epoxy nanocomposites with different addition amounts, which are respectively magnified 1000 times (I) and 10000 times (II), wherein a is pure epoxy resin, b is 0.05 wt% addition amount, c is 0.075 wt% addition amount, d is 0.1 wt% addition amount, and e is 0.125 wt% addition amount.

FIG. 5 shows the results of mechanical property tests of epoxy nanocomposites with different addition amounts, wherein (a) and (b) are tensile property test results, and (c) and (d) are flexural property test results.

FIG. 6 is a plot of (a) storage modulus (E') and (b) loss factor (Tan. delta.) as a function of temperature for various addition levels of epoxy nanocomposites.

Detailed Description

The raw materials and equipment used in the invention are known products and are obtained by purchasing commercial products.

Example 1 preparation of modified graphene oxide of the invention

(1) Preparation of intermediate 1(C-GO)

Weighing 1g of graphene oxide (GO with a C/O molar ratio (6.9-7.1): 3, purchasing the graphene oxide from Beijing carbon century technology Co., Ltd.), ultrasonically dispersing the cell in 300mL of dried Dimethylformamide (DMF), adding the dispersed GO suspension into a 1000mL three-necked bottle, sequentially adding 4,4' -diaminodicyclohexylmethane (PACM), Dimethylepoxypyridine (DMAP) and N, N-Dicyclohexylcarbodiimide (DCC), and ensuring that m (GO), (PACM) N (DMAP) N (DCC) is 1 g: 30mmol, 10 mmol. The mixed solution reacts for 24 hours at 90 ℃, after the reaction is finished, the mixed solution is cooled to room temperature, a 0.45 mu m polytetrafluoroethylene filter membrane is adopted for decompression and suction filtration, DMF is used for washing for 5 times, and unreacted 4,4' -diaminodicyclohexyl methane and catalyst are washed away, so that an intermediate product 1(C-GO) is obtained.

(2) Preparation of intermediate 2(C-P-GO)

Ultrasonically dispersing the obtained C-GO in 250ml of anhydrous DMF again; weighing 150mmol of terephthalic acid (PTA), dissolving in 50ml of anhydrous DMF at 90 ℃ (0.5h), adding the ultrasonic dispersion, mixing and stirring for 1 h; condensing agents DMAP and DCC were added in such proportions that m (GO) n (DMAP) n (DCC) was 01 g: 10mmol:10 mmol. The mixed solution reacts for 24 hours at 90 ℃, after the reaction is finished, the mixed solution is cooled to room temperature, a 0.45 mu m polytetrafluoroethylene filter membrane is adopted for decompression and suction filtration, DMF is used for washing for 5 times, and unreacted 4,4' -diaminodicyclohexyl methane and catalyst are washed away, so that an intermediate product 2(C-P-GO) is obtained.

(3) Preparation of modified graphene oxide (C-P-M-GO) of the invention

Ultrasonically dispersing the obtained C-P-GO in 250ml of anhydrous DMF again; 4,4' -diaminodiphenylmethane (DDM), Dimethylepoxypyridine (DMAP) and N, N-Dicyclohexylcarbodiimide (DCC) were added in this order, and it was ensured that m (GO), N (DDM), N (DMAP), N (DCC) was 1 g: 30mmol, 10 mmol. The mixed solution reacts for 24 hours at 90 ℃, after the reaction is finished, the mixed solution is cooled to room temperature, a 0.45-micron polytetrafluoroethylene filter membrane is adopted for decompression and suction filtration, DMF is used for washing for 5 times, and unreacted 4,4' -diaminodicyclohexylmethane and catalyst are washed away, so that the modified graphene oxide (C-P-M-GO) is obtained.

Example 2 preparation of modified graphene oxide/epoxy nanocomposite (C-P-M-GO/EP) of the invention

According to the formula shown in table 1, modified graphene oxide C-P-M-GO was weighed at a ratio of 1: ultrasonic dispersion was carried out in an acetone solution at a ratio of 1mg/mL, and 70g of TDE-85 epoxy resin (purchased from Tianjin Kanto chemical composites Co., Ltd.) was added to the solution uniformly dispersed after the ultrasonic dispersion, and the solvent was removed by mechanical stirring at 65 ℃. Weighing a mixed curing agent of 4,4' -diaminodiphenylmethane (DDM) and 3, 5-diethyl-2, 4-toluenediamine (DETDDA), adding the mixed curing agent into the modified graphene oxide/TDE-85 epoxy resin mixed solution, and stirring for 15min at a constant speed by an electric motor to fully mix the curing agent and the resin. The obtained mixed solution is placed in a vacuum drying box and is dried for 30min in vacuum so as to remove air bubbles introduced in the stirring process. And finally, pouring the mixed liquid after vacuum drying into a polytetrafluoroethylene mould of a standard sample strip, and putting the polytetrafluoroethylene mould into an oven for curing and forming, wherein the curing conditions are as follows: 120 ℃ X2 h +150 ℃ X3 h +180 ℃ X1 h.

TABLE 1 formulation of modified graphene oxide/epoxy nanocomposites

The following test examples demonstrate the advantageous effects of the present invention.

Test example 1, Property analysis

1. Infrared characterization

(1) Test method

The C-P-M-GO prepared in the embodiment 1 of the invention is subjected to infrared analysis, and GO is used as a reference.

(2) Test results

The infrared spectrum can effectively represent the change of the functional group types on the surface of the graphene oxide. From the results of the IR spectrum of FIG. 1, it can be seen that 1700cm was observed as the modification proceeded^-1The carboxyl groups on the surface of the graphene oxide disappear; at the same time, the height of the groove is 2930cm^-1And 2850cm^-1A stretching vibration peak of methylene is generated; in addition 1200cm^-1The enhancement of the appearance of the peak of the nearby C-N bond indicates that the amino-terminated modified graphene oxide is successfully prepared by the method.

2. Raman analysis

(1) Test method

Raman spectroscopy is an effective characterization tool for the surface structure of carbon-based materials. Raman analysis is carried out on the C-P-M-GO prepared in the embodiment 1 of the invention, and GO is used as a reference.

(2) Test results

As can be seen from fig. 2 and table 2, with the surface modification of GO, the wave numbers of the D and G bands of the modified graphene oxide are shifted to different degrees due to the chemical reaction of the oxygen-containing functional group, which proves that the species of the functional group on the surface of the graphene oxide is changed. I is_D/I_GIs often used to characterize the size of the defect level in carbon atom crystals, I_D/I_GThe larger the ratio, the more carbon material is presentThe more the defect degree is, the more sp3 hybrid structures exist on the surface, thereby indirectly proving that the modifier is successfully grafted to the surface of the carbon material. Compared with graphene oxide, the D band of the modified graphene oxide is shifted, and I thereof_D/I_GThe values also all show different increases, thereby proving again that the invention successfully prepares the amino-terminated modified graphene oxide.

TABLE 2 Raman analysis results

3. Thermogravimetric analysis

(1) Test method

Thermogravimetric analysis (TGA) can be used to characterize the composition and stability of graphene oxide and modified graphene oxide. The C-P-M-GO prepared in the embodiment 1 of the invention is subjected to thermogravimetric analysis, and GO is used as a reference.

(2) Test results

Fig. 3 and table 3 show the results of thermogravimetric analysis of graphene oxide and modified graphene oxide in a nitrogen atmosphere. It can be seen that, with the modification, the graphene nanosheet is changed by thermal residue at 800 ℃, and a new thermal weight loss peak appears on the DTG curve at the same time, corresponding to the decomposition process of the modification reagent on the graft, thereby proving that the modification reagent is successfully grafted on the surface of the graphene oxide.

TABLE 3 thermogravimetric results

Test example 2 characterization of the microstructure of the composite Material of the present invention

(1) Test method

In order to better study the influence of the micro morphology and the interface property of the composite material on the macroscopic mechanical property of the epoxy nanocomposite material, Scanning Electron Microscope (SEM) tests are respectively carried out on the fracture surfaces of the composite materials with different addition amounts of C-P-M-GO.

(2) Test results

FIG. 4 shows SEM images of cross-sections of various amounts of C-P-M-GO/epoxy nanocomposites after room temperature tensile test. In a low magnification (1000 times) SEM image, it can be observed that some pit-like structures exist in the modified graphene oxide/epoxy nanocomposite material, and aggregates of the modified graphene oxide can be seen in the middle of the pits. And with the increase of the addition amount of the modified graphene oxide, the number of the pit-shaped structures is gradually increased, and the size is gradually increased. From SEM images with high magnification (10000 times), obvious holes or gaps are not observed in the tensile section SEM images of the modified graphene oxide/epoxy nanocomposite, which shows that the compatibility between the C-P-M-GO nanosheet and the epoxy resin is good and the interface bonding strength is high.

Test example 3 characterization of mechanical Properties of the composite Material of the present invention

(1) Test method

In order to better study the influence of the modified graphene oxide C-P-M-GO with different contents on the mechanical property of the TDE-85 epoxy resin. The mechanical properties of the epoxy nanocomposite prepared in example 2 of the present invention were studied using tensile and three-point bending test methods.

(2) Test results

FIG. 5 shows the mechanical property test results of TDE-85 nano epoxy composite material under different addition amounts of pure epoxy resin and C-P-M-GO. From the results of fig. 5(a) and 5(b), it can be seen that the C-P-M-GO epoxy nanocomposite material of the present invention achieves a significant improvement in tensile properties of epoxy resin at a very low addition amount, and as the addition amount of modified graphene oxide increases, the tensile properties of the epoxy nanocomposite material further decrease. As shown in the results of Table 4, the tensile strength of the C-P-M-GO epoxy nanocomposite material reaches the best at the addition of 0.05 wt% of C-P-M-GO, and is improved from 89.235MPa to 108.61MPa, which is 21.71% higher than that of pure epoxy resin. Under the condition that the addition amount of the C-P-M-GO is 0.075 wt%, the sum elongation at break of the C-P-M-GO epoxy nanocomposite material is optimal, the sum elongation is increased from 4.8075% to 5.954%, and the amplification is 23.85%.

FIG. 5(C), FIG. 5(d) and Table 5 are the results of flexural performance testing of C-P-M-GO epoxy nanocomposites. Compared with pure epoxy resin, the bending strength and the bending modulus of the epoxy nanocomposite material are increased firstly and then slightly reduced, under the condition that the addition amount of the C-P-M-GO is 0.05 wt%, the bending strength and the bending modulus of the C-P-M-GO epoxy nanocomposite material are optimal, the bending strength and the bending modulus are respectively increased from 154.85MPa to 176.56MPa and from 4023.13MPa to 4485.14MPa, and the increase of the bending strength and the bending modulus of the epoxy nanocomposite material is respectively 14.02% and 11.49% compared with the pure epoxy resin.

TABLE 4 composite tensile Property test results

TABLE 5 composite bending Performance test results

Experimental results prove that the C-P-M-GO can effectively improve the mechanical property of the epoxy resin, and particularly the improvement range of the tensile property is obvious.

Test example 4 characterization of dynamic mechanical Properties of the composite Material of the invention

(1) Test method

Dynamic thermomechanical analysis (DMA) was used to characterize the viscoelasticity of pure epoxy resins and the modified graphene oxide/TDE-85 epoxy nanoparticles of the present invention.

(2) Test results

Fig. 6 is a graph of loss factor (Tan δ) and storage modulus (E') of pure epoxy resin and modified graphene oxide/epoxy nanocomposite material as a function of temperature. As can be seen from the data in table 6, the storage modulus of the composite material is improved after adding 0.075 wt% of the modified graphene oxide nanoplatelets, which is mainly due to the reinforcing effect of the graphene oxide nanoplatelets.

The glass transition temperature (Tg) is an important mark reflecting the movement capability of a polymer chain segment, and the movement of the polymer chain segment can be obviously influenced by adding the nano-filler into a polymer system. As can be seen from fig. 6 and table 6, after 0.075 wt% of the modified graphene oxide nanosheets are added, Tg of the composite material system is increased, and heat resistance of the material is significantly increased.

TABLE 6 glass transition temperature and storage modulus of the composites

Experimental results prove that the specific addition amount of C-P-M-GO can effectively improve the glass transition temperature and the storage modulus of the composite material and improve the rigidity of the composite material.

In conclusion, the modified graphene oxide C-P-M-GO with rich amino groups on the surface is successfully prepared, and the C-P-M-GO epoxy nanocomposite system is further prepared. The amino-terminated modified graphene oxide prepared by the invention can simultaneously improve the elongation at break, tensile strength, elastic modulus, glass transition temperature and storage modulus of the epoxy nanocomposite material with low addition. Namely, the epoxy nanocomposite material prepared by the invention has the advantages of improved toughness, obviously improved mechanical property, rigidity and heat resistance, excellent comprehensive performance and excellent application prospect.

Claims

1. A modified graphene oxide characterized by: the graphene oxide is obtained by replacing-OH groups on carboxyl on the surface of graphene oxide by A groups; wherein the structure of the A group is:

2. the modified graphene oxide according to claim 1, wherein: the material is prepared from the following raw materials: graphene oxide, 4 '-diaminodicyclohexylmethane, p-benzene substituted derivatives, and 4,4' -diaminodiphenylmethane, wherein the ratio of graphene oxide: 4,4' -diaminodicyclohexylmethane: p-benzene substituted derivatives: the ratio of 4,4' -diaminodiphenylmethane was 1 g: (20-40) mmol: (140-160) mmol: (20-40) mmol; the structure of the p-benzene substituted derivative is

R₁、R₂Each independently selected from hydroxy, halogen.

3. The modified graphene oxide according to claim 2, wherein: r₁、R₂Each independently selected from hydroxyl groups.

4. The modified graphene oxide according to claim 2 or 3, wherein: the graphene oxide: 4,4' -diaminodicyclohexylmethane: the proportion of the para-benzene substituted derivative is 1 g: 30mmol: 150 mmol: 30 mmol.

5. A method for preparing the modified graphene oxide according to any one of claims 1 to 4, wherein: the method comprises the following three steps:

6. The method of claim 5, wherein: in the steps (1), (2) and (3): the raw materials also comprise a catalyst and a dehydrating agent; the method also comprises the following operations after the reaction is finished: carrying out vacuum filtration, and keeping and washing a solid; the reaction temperature is 70-100 ℃; the reaction time is 12-36 hours; the reaction solvent and the washing reagent are respectively and independently selected from one or more of dimethylformamide, dimethylacetamide, tetrahydrofuran and alcohol solvents.

7. The method of claim 6, wherein: the catalyst is dimethylaminopyridine, and the dehydrating agent is N, N-dicyclohexylcarbodiimide; the reaction temperature is 90 ℃; the reaction time is 24 hours; the reaction solvent and washing reagent are selected from dimethylformamide.

8. The method according to claim 6 or 7, characterized in that: in the step (1), the mass molar ratio of the graphene oxide to the 4,4' -diaminodicyclohexylmethane to the catalyst to the dehydrating agent is 1 g: (20-40) mmol: (5-15) mmol: (5-15) mmol;

and/or in the step (2), the mass molar ratio of the graphene oxide to the p-benzene substituted derivative, the catalyst and the dehydrating agent is 1 g: (120-180) mmol: (5-15) mmol: (5-15) mmol;

and/or in the step (3), the mass molar ratio of the graphene oxide to the 4,4' -diaminodiphenylmethane, the catalyst and the dehydrating agent is 1 g: (20-40) mmol: (5-15) mmol: (5-15) mmol.

9. The method of claim 8, wherein: in the step (1), the mass molar ratio of the graphene oxide to the 4,4' -diaminodicyclohexylmethane to the catalyst to the dehydrating agent is 1 g: 30mmol:10mmol:10 mmol;

and/or in the step (2), the mass molar ratio of the graphene oxide to the p-benzene substituted derivative, the catalyst and the dehydrating agent is 1 g: 150 mmol:10mmol:10 mmol;

and/or in the step (3), the mass molar ratio of the graphene oxide to the 4,4' -diaminodiphenylmethane, the catalyst and the dehydrating agent is 1 g: 30mmol:10mmol:10 mmol.

10. An epoxy nanocomposite characterized by: the modified graphene oxide is prepared from the modified graphene oxide, epoxy resin and a curing agent according to any one of claims 1 to 4.

11. The composite material of claim 10, wherein: the weight parts of the raw materials are as follows: 70 parts of epoxy resin, 29.3 parts of curing agent and 0.0175-0.0875 parts of modified graphene oxide;

and/or the epoxy resin is alicyclic glycidyl ester epoxy resin;

and/or the curing agent is an aromatic curing agent.

12. The composite material of claim 11, wherein: the weight parts of the raw materials are as follows: 70 parts of epoxy resin, 29.3 parts of curing agent and 0.0375-0.0525 parts of modified graphene oxide;

and/or the epoxy value of the alicyclic glycidyl ester epoxy resin is 0.8-0.9,

and/or the curing agent is one or two of 4', 4-diaminodiphenylmethane and 3, 5-diethyl-2, 4-toluenediamine.

13. The composite material of claim 12, wherein: the epoxy value of the alicyclic glycidyl ester epoxy resin is 0.85;

and/or the curing agent is a mixed curing agent of 4', 4-diaminodiphenylmethane and 3, 5-diethyl-2, 4-toluenediamine with equivalent weight.

14. A method for preparing the epoxy nanocomposite material according to any one of claims 10 to 13, characterized in that: the method comprises the following steps:

(a) weighing the modified graphene oxide of any one of claims 1 to 4, ultrasonically dispersing in an organic solvent, adding epoxy resin, and uniformly stirring; then removing the organic solvent;

15. The method of claim 14, wherein: in step (a), the organic solvent is selected from acetone; the mass volume ratio of the modified graphene oxide to the organic solvent is 1: (0.5-3) mg/mL;

and/or, in step (c), the curing conditions are: 2 hours at (110-130) DEG C, then 3 hours at (140-160) DEG C, and then 1 hour at (170-190) DEG C.

16. The method of claim 15, wherein: in the step (a), the mass-to-volume ratio of the modified graphene oxide to the organic solvent is 1: 1 mg/mL;

and/or, in step (c), the curing conditions are: at 120 ℃ for 2h, then at 150 ℃ for 3h, then at 180 ℃ for 1 h.