Rigid suspension group modified epoxy resin material as well as preparation method and application thereof

Abstract

The invention provides a rigid suspension group modified epoxy resin material as well as a preparation method and application thereof, and belongs to the field of advanced materials. The epoxy compound shown in the formula I is prepared by introducing a rigid suspension group into an epoxy resin system, so that the free volume of the further cured epoxy resin material is effectively regulated and controlled, and the compactness of a network is remarkably improved. The glass transition temperature, the mechanical property and the thermal stability of the epoxy resin prepared by the method are remarkably improved. The invention provides a new strategy for optimizing the performance of the epoxy resin, and lays a theoretical foundation for designing a high-performance polymer material. # imgabs0 #

Description

Technical Field

[0001] The present invention belongs to the field of advanced materials, and particularly relates to an epoxy resin material modified by a rigid pendant group, a preparation method thereof, and uses thereof. Background Art

[0002] Epoxy resins generally refer to organic polymers containing two or more epoxy groups in the molecule and belong to thermosetting polymers. Due to their excellent mechanical properties, adhesion, electrical insulation, and chemical stability, epoxy resins have been widely used in fields such as aerospace, electronic packaging, and high-performance composite materials. The properties of such thermosetting polymers largely depend on the three-dimensional cross-linked network structure formed after curing. However, due to the uneven arrangement of molecular chains and the free volume in the curing network during the curing process, epoxy resins usually exhibit a relatively high coefficient of thermal expansion and a relatively low glass transition temperature, which may lead to performance degradation and dimensional stability problems in practical applications. Therefore, how to effectively regulate the microstructure and free volume of the epoxy resin curing network has become the key to improving its comprehensive performance.

[0003] Studies have found that optimization can be carried out in various ways. For example, the network structure of the curing system can be regulated by changing the curing agent or introducing a rigid structure. Designing curing agents with special topological structures or functional groups can achieve the optimization and balance of network density, and improve the mechanical properties and thermal stability of the material. By introducing dynamic reversible bonds or fine design of molecular chains, the free volume of the curing network can be effectively reduced, the packing efficiency of molecular chain segments can be improved, and thus the compactness and durability of the material can be enhanced. In addition, by modifying the side groups and promoting the conformational conversion of the cross-linked network in combination with conformational evolution, the modulus, strength, and deformation ability of thermosetting materials can be improved in multi-component resins with a low side group concentration.

[0004] The literature (DOI: 10.1016 / j.polymdegradstab.2004.01.016) reported an epoxy monomer containing a biphenyl group and used 4,4-diaminodiphenylmethane (DDM) for curing to form a new structure epoxy resin, but its glass transition temperature is relatively low and needs to be further improved. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide an epoxy resin material modified by a rigid pendant group, a preparation method thereof, and uses thereof.

[0006] The present invention provides an epoxy compound, and the structure of the epoxy resin is shown in Formula I:

[0007]

[0008] Among them, R is selected from a thiophene ring, a pyridine ring, a furan ring, benzothiazole, benzoxazine, phenanthrene, perylene, a benzene ring, biphenyl, naphthalene, anthracene or pyrene.

[0009] Further, R is preferably a benzene ring, biphenyl, naphthalene, anthracene or pyrene.

[0010] Further, the epoxy resin is selected from one of the following compounds:

[0011]

[0012] The present invention also provides a method for preparing the above epoxide, and the method comprises the following steps:

[0013]

[0014] (1) React 2,4-dihydroxybenzaldehyde with R-NH2 to obtain an intermediate;

[0015] (2) React the intermediate with epichlorohydrin to obtain the epoxide.

[0016] Further, in step (1), the molar ratio of 2,4-dihydroxybenzaldehyde to R-NH2 is 1 to 1.2: 0.05 to 0.15; the solvent for the reaction is an organic solvent; the reaction temperature is 10 to 90 °C, and the time is 1 to 5 h;

[0017] In step (2), the molar ratio of the hydroxyl group in the intermediate to epichlorohydrin is 1: 10 to 20; the reaction is carried out under the action of a catalyst and a base, and the mass ratio of the catalyst to the intermediate is 0.5 to 1.5: 100; the base is an inorganic base; the molar ratio of the base to the intermediate is 2 to 3: 1; the reaction conditions are: first react at 80 to 120 °C for 4 to 8 h, and then add the base at 20 to 60 °C and react for 2 to 6 h.

[0018] Further, in step (1), the molar ratio of 2,4-dihydroxybenzaldehyde to R-NH2 is 1.05: 0.1; the solvent for the reaction is ethyl L-lactate or absolute ethanol; the reaction temperature is 15 to 80 °C, and the time is 3 to 6 h;

[0019] In step (2), the molar ratio of the hydroxyl group in the intermediate to epichlorohydrin is 1: 15; the catalyst is tetrabutylammonium bromide; the mass ratio of the catalyst to the intermediate is 1: 100; the base is sodium hydroxide; the molar ratio of the base to the intermediate is 2.25: 1; the reaction conditions are: first react at 100 °C for 6, and then add the base stepwise at 40 °C and react for 4 h.

[0020] The present invention also provides an epoxy resin system, which is a product prepared from the above-mentioned epoxide compound, epoxy resin and curing agent, and the molar ratio of the epoxide compound, epoxy resin and curing agent is 1:1-9:0.05-5.

[0021] Further, the epoxy resin is selected from glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, alicyclic epoxy resins or linear aliphatic epoxy resins.

[0022] Further, the glycidyl ether type epoxy resin is selected from bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins or phenolic epoxy resins, and preferably bisphenol A diglycidyl ether.

[0023] Further, the curing agent is selected from amine curing agents, acid anhydride curing agents or phenolic curing agents.

[0024] Further, the curing agent is an amine curing agent, and preferably 4,4-diaminodiphenylmethane.

[0025] The present invention also provides a method for preparing the above-mentioned epoxy resin system, and the method includes the following steps: mixing the epoxide compound, epoxy resin and curing agent, curing, and cooling to obtain the product.

[0026] Further, the curing conditions are: curing at 80-120°C for 1-3 h, then curing at 120-160°C for 2-4 h, and finally curing at 160-200°C for 2-4 h.

[0027] Further, the curing conditions are: curing at 100°C for 2 h, then curing at 140°C for 3 h, and finally curing at 180°C for 3 h.

[0028] The present invention also provides the uses of the above-mentioned epoxide compound and the above-mentioned epoxy resin system in the preparation of aerospace materials, electronic packaging materials, automotive manufacturing materials, engineering building materials, coating materials and carbon fiber composites.

[0029] The present invention has achieved the following beneficial effects:

[0030] By introducing rigid pendant groups into the epoxy resin system, the present invention realizes the effective regulation of the free volume of the epoxy resin material after further curing, and significantly improves the densification of the network. The glass transition temperature (Tg), mechanical properties and thermal stability of the epoxy resin prepared by the present invention are significantly improved. The present invention provides a new strategy for optimizing the properties of epoxy resins and lays a theoretical foundation for the design of high-performance polymer materials.

[0031] Compared with the epoxy resin reported in the literature (DOI: 10.1016 / j.polymdegradstab.2004.01.016), the glass transition temperature of the epoxy resin of the present invention has been significantly improved, and its glass transition temperature can reach up to 204 °C; while the glass transition temperature of the epoxy resin in the literature (DOI: 10.1016 / j.polymdegradstab.2004.01.016) is only 128-177 °C.

[0032] Obviously, based on the above content of the present invention, according to the common general technical knowledge and customary means in the art, without departing from the above basic technical idea of the present invention, various other forms of modifications, substitutions or changes can also be made.

[0033] The following is a further detailed description of the above content of the present invention through specific embodiments in the form of examples. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above content of the present invention fall within the scope of the present invention. Brief Description of the Drawings

[0034] Figure 1 Nuclear magnetic resonance spectroscopy data for (a) RA, (b) RAE, (c) RAB, and (d) RABE.

[0035] Figure 2 (a) Flexural strength; (b) flexural modulus for different compound curing systems.

[0036] Figure 3 Thermomechanical curves for DMA testing of different compound curing systems: (a) Temperature dependence curve of Tanδ; (b) Temperature dependence curve of E'; (c) TGA and (d) DTG curves under N2 atmosphere.

[0037] Figure 4 (a) Thermal expansion curve; (b) Curve of thermal expansion coefficient vs. temperature for different compound curing systems. Detailed Description of the Invention

[0038] The raw materials and equipment used in the present invention are all known products, obtained by purchasing commercially available products.

[0039] "Room temperature" referred to in the present invention means 25 ± 10 °C.

[0040] The 2,4-dihydroxybenzaldehyde, 4-aminobiphenyl, aniline, ethyl L-lactate and epichlorohydrin used in the present invention are provided by adamas company; anhydrous ethanol (AR), bisphenol A diglycidyl ether (E51) are provided by Shanghai Huayi Co., Ltd., and 4,4-diaminodiphenylmethane (DDM) is provided by Aladdin Reagent Co., Ltd.

[0041] Example 1. Synthesis of the Epoxy Compound RAE of the Present Invention

[0042]

[0043] 1. Synthesis of RA

[0044] Dissolve 9.3 g of aniline (0.1 mol) in 50 mL of 90% ethyl L-lactate, add 14.5 g of 2,4-dihydroxybenzaldehyde (1.05 mol), stir at room temperature for 3 h to obtain an orange-red solution. Add an excess of water, collect the reddish-brown precipitate, dry it to obtain (2,4-dihydroxyphenyl)methanimine (denoted as RA) (yield: 88.43%). Figure 1 The structural characterization data of RA shown in (a) are as follows: 1 H NMR (400 MHz, DMSO, RA) δ 13.55 (s, 1H), δ 10.27 (s, 1H), δ 8.81 (s, 1H), δ 7.45 - 7.41 (m, 3H), δ 7.35 - 7.32 (d, 2H), δ 7.28 - 7.24 (td, 1H), δ 6.42 - 6.39 (m, 1H), δ 6.30 - 6.29 (d, 1H).

[0045] 2. Synthesis of RAE

[0046] Add the hydroxyl group in RA and epichlorohydrin to a round-bottom flask according to a molar ratio of 1:15, select tetrabutylammonium bromide as the catalyst, and the addition amount is 1% of the mass of RA. After reacting at 100 °C for 6 h, add NaOH step by step at 40 °C for ring closure, and the addition amount is 2.25 times the molar number of RA. Stir, cool and filter. Extract the catalyst and salts in the solution with deionized water, let it stand for layering, and then rotary evaporate and concentrate epichlorohydrin to obtain a resin product, denoted as RAE. Figure 1 The structural characterization data of RAE shown in (b) are as follows: 1 H NMR (400 MHz, DMSO, RAE) δ 8.76 (s, 1H), δ 8.00 - 7.97 (d, 1H), δ 7.42 - 7.38 (td, 2H), δ 7.23 - 7.16 (m, 2H), δ 7.09 - 7.05 (m, 1H), δ 6.78 - 6.69 (m, 2H), δ 4.51 - 4.42 (m, 2H), δ 4.03 - 3.90 (m, 2H), δ 3.43 - 3.15 (m, 2H), δ 2.90 - 2.73 (m, 4H).

[0047] Example 2. Synthesis of the Epoxy Compound RABE of the Present Invention

[0048]

[0049] 1. Synthesis of RAB

[0050] Dissolve 16.9 g of 4-aminobiphenyl (0.1 mol) and 14.5 g of 2,4-dihydroxybenzaldehyde (1.05 mol) in 100 mL of absolute ethanol, stir at 80 °C for 6 h, collect the pale yellow precipitate, and dry it to obtain N-(4-Phenylphenyl)methanimine (denoted as RAB) (yield: 85.63%). Figure 1 The structural characterization data of RAB shown in (c) are as follows: 1 H NMR (400 MHz, DMSO, RAB) δ 13.57 (s, 1H), δ 10.29 (s, 1H), δ 8.88 (s, 1H), δ 7.75 - 7.69 (m, 4H), δ 7.50 - 7.44 (m, 5H), δ 7.38 - 7.35 (td, 1H), δ 6.44 - 6.41 (m, 1H), δ 6.33 - 6.31 (d, 1H).

[0051] 2. Synthesis of RABE

[0052] Refer to the synthesis method of RAE in Example 1, with the only difference being that RA is replaced by RAB to obtain a resin product denoted as RABE. Figure 1 The structural characterization data of RABE shown in (d) are as follows: 1 HNMR (400 MHz, DMSO, RABE) δ 8.82 (s, 1H), δ 8.02 - 8.00 (d, 1H), δ 7.75 - 7.68 (td, 2H), δ 7.55 - 7.34 (m, 5H), δ 7.29 - 7.27 (d, 2H), δ 6.77 - 6.71 (m, 2H), δ 4.51 - 4.43 (m, 2H), δ 4.03 - 3.87 (m, 2H), δ 3.57 - 3.20 (m, 2H), δ 2.89 - 2.69 (m, 4H).

[0053] Example 3. Preparation of the epoxy resin composite system of the present invention

[0054] According to the formulation in Table 1, bisphenol A diglycidyl ether (E51) and RAE are compounded and used, and 4,4-diaminodiphenylmethane (DDM) is selected as the curing agent. The specific preparation method is as follows: Use the casting method for molding and bend the spline. The curing conditions are 100 °C for 2 h, 140 °C for 3 h, and 180 °C for 3 h. After completion, annealing is carried out at room temperature. The prepared epoxy resin is denoted as RAE-E51-3-7-DDM.

[0055] Example 4. Preparation of the epoxy resin composite system of the present invention

[0056] Referring to the method of Reference Example 3, according to the formulation in Table 1, E51 and RAE were compounded and used, and DDM was selected as the curing agent. The prepared epoxy resin was denoted as RAE-E51-5-5-DDM.

[0057] Example 5. Preparation of the epoxy resin compounding system of the present invention

[0058] Referring to the method of Reference Example 3, according to the formulation in Table 1, E51 and RABE were compounded and used, and DDM was selected as the curing agent. The prepared epoxy resin was denoted as RABE-E51-3-7-DDM.

[0059] Example 6. Preparation of the epoxy resin compounding system of the present invention

[0060] Referring to the method of Reference Example 3, according to the formulation in Table 1, E51 and RABE were compounded and used, and DDM was selected as the curing agent. The prepared epoxy resin was denoted as RABE-E51-5-5-DDM.

[0061] The following is the preparation of control samples through comparative examples.

[0062] Comparative Example 1. Preparation of epoxy resin

[0063] Referring to the method of Reference Example 3, according to the formulation in Table 1, E51 and DDM were directly reacted to prepare the epoxy resin E51-DDM.

[0064] Table 1 Formulation table of epoxy resin compounding system

[0065] Sample Name E51 RAE / RABE DDM E51-DDM 80.0wt%(1mol) - 20.0wt%(0.5mol) RAE-E51-3-7-DDM 57.3wt%(2.3mol) 24.6wt%(1mol) 18.1wt%(1.65mol) RAE-E51-5-5-DDM 40.9wt%(1mol) 40.9wt%(1mol) 18.2wt%(1mol) RABE-E51-3-7-DDM 56.2wt%(2.3mol) 24.1wt%(1mol) 19.7wt%(1.65mol) RABE-E51-5-5-DDM 40.7wt%(1mol) 40.7wt%(1mol) 18.6wt%(1mol)

[0066] The following demonstrates the beneficial effects of the present invention through experimental examples.

[0067] Experimental Example 1. Characterization and performance testing of epoxy resin compounding system

[0068] 1. Experimental method

[0069] (1) Structural characterization

[0070] Nuclear magnetic resonance spectroscopy (NMR) was carried out on a Bruker AVIII HD 400 MHz, using DMSO-d6 as the solvent.

[0071] (3) Performance testing

[0072] According to ASTM D7264 standard, a three-point bending test was carried out on an 80×10×4 mm sample using a three-point bending fixture of an Instron 5567 universal tensile testing machine. The span was 64 mm and the rate was 2 mm / min. A nanoindentation system of MTS100BA-1C equipped with a Berkovich diamond indenter was used to study the mechanical properties of the sample by means of a classical load-hold-unload cycle, and the load was 10 nN. A dynamic mechanical analysis (DMA) test was carried out on the sample in a three-point bending mode using TA Q800, with a frequency of 1.0 Hz and an amplitude fixed at 15.0 μm. The conditions were a temperature range of 30 - 250 °C and a heating rate of 10 K / min. A TMA test was carried out in a tensile mode using a TA Q400EM instrument (TA, USA) under N2 atmosphere. The thermogravimetric curve (TGA) was obtained by a thermogravimetric analyzer (2019BE5D, Mettler Company), where the heating rate was 10 K / min.

[0073] 2. Experimental Results

[0074] 2.1 Structural Characterization

[0075] Nuclear magnetic resonance spectroscopy data ( Figure 1 ) indicate that RA, RAE, RAB, and RABE have been successfully prepared in this invention.

[0076] 2.2 Performance Tests

[0077] (1) Mechanical Properties

[0078] Figure 2 The (a) flexural strength and (b) flexural modulus of different components were analyzed, and the specific data are shown in Table 2. The results show that with the addition of RAE and RABE, the flexural modulus of the compound resin system shows an upward trend, corresponding to the test results of nanoindentation, and the Young's modulus and hardness also show an upward trend. The mechanical properties of the epoxy resin compound system (RAE system) introducing benzene ring groups are better than those of the epoxy resin compound system (RABE system) introducing biphenyl groups. Moreover, when RAE and E51 are compounded at a mass ratio of 1:1, the strength can reach 156 MPa and the modulus is 3.9 GPa, which are 1.31 and 1.35 times that of the E51-DDM system respectively. The improvement of the strength of the epoxy resin compound system (RABE system) introducing biphenyl groups is not obvious.

[0079] Table 2 Flexural Strength and Flexural Modulus of Different Compound Curing Systems

[0080] Sample Name Flexural Strength (MPa) Flexural Modulus (MPa) E51-DDM 119.6±2.2 2918.6±67.5 RAE-E51-3-7-DDM 137.4±5.8 3424.5±61.2 RAE-E51-5-5-DDM 156.9±0.6 3948.4±118.0 RABE-E51-3-7-DDM 122.3±4.0 3558.7±23.3 RABE-E51-5-5-DDM 115.3±9.6 4137.1±152.8

[0081] (2) Thermomechanical Properties

[0082] Figure 3(a) and (b) show the temperature-dependent curves of the loss tangent (Tanδ) and storage modulus (E’) of different curing systems. The glass transition temperature of the E51-DDM system is around 180 °C. With the addition of RAE and RABE, the rigidity of the curing network is enhanced, and the glass transition temperatures of the RAE-DDM system and RABE-DDM system show an upward trend. Among them, the glass transition temperature of RAE-E51-5-5-DDM can reach 204 °C. However, the improvement effect of the glass transition temperature of RABE is less than that of RAE. At the same time, the peak value of Tanδ is closely related to the molecular chain segment movement and energy dissipation ability of the material. The peak value of Tanδ of the RAE-DDM system with the addition of RAE is lower than that of the E51-DDM system, reducing the segmental mobility and energy dissipation. The addition of RABE requires higher energy dissipation.

[0083] Figure 3 (c) and (d) show the TGA and DTG results of different curing systems under N2 atmosphere. The addition amounts of RAE and RABE are negatively correlated with the maximum thermal degradation rate of the resin matrix. When heated to 800 °C, the R of E51-DDM 800 is 13.85%, while those of RAE-E51-5-5-DDM and RABE-E51-5-5-DDM are 22.31% and 20.71% respectively, showing an increase of 61% and 49% respectively, indicating that RAE and RABE can promote the formation of carbon layers during the decomposition process and make significant contributions to the carbonization ability at high temperatures.

[0084] Figure 4 (a) and (b) analyze the coefficient of thermal expansion (CTE) of the materials. In the initial heating stage, the overall resin curing system is in a glassy state, and the CTE value is relatively high. After adding RAE and RABE to the system, the CTE value decreases. As the temperature further increases, the CTE value increases significantly. However, the systems with the addition of RAE and RABE still have a smaller CTE value compared to E51-DDM. Therefore, they show excellent dimensional stability at high temperatures.

[0085] Table 4 Thermal property data of different compound curing systems

[0086]

[0087] The above results indicate that the rigid pendant groups can improve the glass transition temperature (Tg), mechanical properties, and thermal stability. When RAE and E51 are compounded at a mass ratio of 1:1, the improvement effect on the flexural strength and flexural modulus is the strongest; the benzene ring group (RAE system) has a better effect on increasing the glass transition temperature than the biphenyl group (RABE system), and the glass transition temperature of RAE-E51-5-5-DDM can reach 204 °C, achieving an unexpected technical effect.

[0088] In summary, the present invention provides a rigid pendant group-modified epoxy resin material, its preparation method, and uses. By introducing rigid pendant groups into the epoxy resin system, the present invention realizes the effective regulation of the free volume of the epoxy resin material after further curing, significantly improving the denseness of the network. The glass transition temperature (Tg), mechanical properties, and thermal stability of the epoxy resin prepared by the present invention are significantly improved. The present invention provides a new strategy for optimizing the properties of epoxy resins and lays a theoretical foundation for the design of high-performance polymer materials.

Claims

1. An epoxy compound, characterized in that The structure of the epoxy resin is shown in Formula I: Wherein, R is selected from a thiophene ring, a pyridine ring, a furan ring, benzothiazole, benzoxazine, phenanthrene, perylene, a benzene ring, biphenyl, naphthalene, anthracene or pyrene.

2. The epoxy compound according to claim 1, characterized in that The epoxy resin is selected from one of the following compounds:

3. A method for preparing the epoxy compound according to claim 1 or 2, characterized in that: The method comprises the following steps: (1) reacting 2,4-dihydroxybenzaldehyde and R-NH2 to obtain an intermediate; (2) The intermediate is reacted with epichlorohydrin to obtain an epoxy compound.

4. An epoxy resin system, characterized in that The invention is a product prepared by taking the epoxy compound, epoxy resin and curing agent as raw materials according to claim 1 or 2, wherein the molar ratio of the epoxy compound, epoxy resin and curing agent is 1:1-9:0.05-5.

5. The epoxy resin system according to claim 4, characterized in that The epoxy resin is selected from glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, alicyclic epoxy resin or linear aliphatic epoxy resin.

6. The epoxy resin system according to claim 5, characterized in that The glycidyl ether epoxy resin is selected from bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin or novolac epoxy resin, and is preferably bisphenol A diglycidyl ether.

7. The epoxy resin system according to claim 4, characterized in that The curing agent is selected from amine curing agents, acid anhydride curing agents or phenolic curing agents.

8. The epoxy resin system according to claim 7, characterized in that The curing agent is an amine curing agent, preferably 4,4-diaminodiphenylmethane.

9. A method for preparing the epoxy resin system according to any one of claims 4 to 8, characterized in that: The method comprises the following steps: mixing an epoxy compound, an epoxy resin and a curing agent, curing, and cooling to obtain the product.

10. The method according to claim 9, characterized in that The curing conditions are: curing at 80-120° C. for 1-3 hours, then curing at 120-160° C. for 2-4 hours, and finally curing at 160-200° C. for 2-4 hours.

11. Use of the epoxy compound according to claim 1 or 2, or the epoxy resin system according to any one of claims 4 to 8 in the preparation of aerospace materials, electronic packaging materials, automobile manufacturing materials, engineering construction materials, coating materials and carbon fiber composites.

Images