Preparation method and application of polymethyl acrylate / epoxy resin composite material

Abstract

The invention discloses a preparation method and application of a polymethyl acrylate / epoxy resin composite material, and belongs to the technical field of epoxy resin. The invention aims to solve the problems of impact resistance and cracking resistance when the traditional epoxy resin is used as an insulator equipment base. The method comprises the following steps: purifying methyl acrylate, adding into epoxy resin, heating and stirring to be uniform, adding an initiator, and continuously stirring to be uniform; then adding a curing agent, continuously stirring until the solution is clear, then dropwise adding an accelerant, and carrying out ultrasonic defoaming; and then pouring the mixture into a mold, and carrying out stepped heating and curing to obtain the composite material. The composite material is suitable for being used as an insulator base material, and can also be applied to different industries such as electronic appliances and automobiles.

Description

Technical Field

[0001] This invention belongs to the field of epoxy resin technology, specifically, it relates to a method for preparing polymethyl acrylate / epoxy resin composite materials and their applications. Background Technology

[0002] As a crucial component of insulators, the selection of materials for insulator bases typically requires comprehensive consideration of factors such as electrical performance, mechanical strength, weather resistance, and corrosion resistance. With the continuous increase in power transmission voltage levels, especially the promotion of ultra-high voltage and extra-high voltage transmission technologies, more stringent requirements have been placed on the comprehensive performance of insulator bases. They not only need excellent electrical insulation performance but also high mechanical strength to withstand various external loads such as conductor tension and wind force, and good corrosion resistance and aging resistance. Against this industry backdrop, finding a new base material with multiple superior properties has become a crucial need in the power sector. Epoxy resin, with its unique material characteristics, has gradually come into the view of researchers. Epoxy resin itself possesses excellent electrical insulation properties, high breakdown strength, and high volume resistivity, effectively isolating current and meeting the insulation requirements of insulator bases. Furthermore, by adding suitable fillers for modification, its mechanical strength can be further improved, enabling it to cope with various mechanical loads in power systems. However, the traditional method of modifying epoxy resin by adding inorganic fillers has many drawbacks. Although inorganic fillers can improve hardness and rigidity, they often lead to excessively brittle epoxy resin materials. Of particular importance is the weak interfacial bonding between inorganic fillers and the organic matrix, which easily leads to interfacial voids. During material aging, delamination occurs at the interface first, resulting in a decline in the overall performance of the material. This invention introduces polymethyl acrylate (PMMA) into epoxy resin, offering several advantages over traditional modification methods that involve adding inorganic fillers. First, synthesizing PMMA in epoxy resin through in-situ polymerization solves the compatibility problem between the two. Furthermore, introducing flexible molecules improves the mechanical properties of epoxy resin, enhancing its impact and crack resistance, and avoiding the potential for increased brittleness caused by inorganic modification. Moreover, the molecular structure of PMMA contains polar groups such as ester groups, which can form hydrogen bonds or weak chemical interactions with the hydroxyl and epoxy groups in epoxy resin, resulting in stronger interfacial bonding and reducing the likelihood of delamination. Summary of the Invention

[0003] This invention aims to solve the technical problems of impact resistance and crack resistance faced by traditional epoxy resin as insulator bases, and provides a method for preparing polymethyl acrylate / epoxy resin composite material and its application.

[0004] To address the aforementioned technical problems, the present invention adopts the following technical solution: The purpose of this invention is to provide a method for preparing a polymethyl acrylate / epoxy resin composite material, comprising the following steps: Step 1: After purifying methyl acrylate, add it to epoxy resin, heat and stir until uniform (takes about 1-2 hours), then add more and continue stirring until uniform (takes about 10-12 hours). Step 2: Then add the curing agent and continue stirring until the solution is clear. Then add the accelerator drop by drop to reduce the curing time of the epoxy resin and degas it using ultrasound. Step 3: Then pour it into the pretreated mold, and cure it by step heating to obtain the composite material.

[0005] Further specifying, in step 1, purification is carried out by vacuum distillation. The specific purification steps are as follows: Methyl acrylate is added to a distillation flask and purified by vacuum distillation. First, a vacuum pump is used to evacuate the distillation apparatus to reduce the pressure inside the apparatus. Then, the temperature is slowly increased by heating in an oil bath until the liquid begins to boil. The distillate is collected to obtain relatively pure methyl acrylate.

[0006] Further specifying, the epoxy resin used in step 1 is a DGEBA type epoxy resin.

[0007] Further specifying, in step 1, the amount of methyl acrylate added is 2%-8% of the mass fraction of epoxy resin, which can be 2 wt%, 4 wt%, 6 wt% or 8 wt%.

[0008] Further specifying, in step 1, heating and stirring are carried out at 75 ℃-80 ℃.

[0009] Further specifying, in step 1, the mass ratio of methyl acrylate to initiator is (0.5-2):(0.025-0.1).

[0010] Further specifying, in step 1, the initiator is benzoyl peroxide, which needs to be dried in an oven at 60 ℃ for 3 h before use. Further specifying, in step 2, the curing agent is methylhexahydrophthalic anhydride or methyltetrahydrophthalic anhydride.

[0011] Further specifying, in step 2, the accelerator is 2,4,6-tris(dimethylaminomethyl)phenol.

[0012] Further specifying, in step 2, the mass ratio of curing agent to epoxy resin is (20-22):(22.5-25).

[0013] Further specifying, in step 2, the mass ratio of accelerator to epoxy resin is (0.22-0.25):(22.5-25).

[0014] Further specifying, in step 2, the dropping speed is 1-2 drops / second.

[0015] Further specifying step 3, the stepwise temperature curing is as follows: hold at 80℃ for 2 hours, then at 100℃ for 2 hours, and finally at 120℃ for 2 hours.

[0016] Further specifying, in step 3, the pre-treated mold is carried out according to the following steps: the surface of the mold is cleaned with alcohol to remove any impurities, and then the mold is placed in an oven at 80 ℃ to dry and preheat.

[0017] Another object of the present invention is to provide a polymethyl acrylate / epoxy resin composite material prepared by any of the above methods.

[0018] Furthermore, the use of the polymethyl acrylate / epoxy resin composite material prepared by any of the methods described above is also provided, for use as a base material for insulator equipment.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention implements a method for preparing a polymethyl acrylate / epoxy resin composite material. First, untreated methyl acrylate is purified by vacuum distillation to obtain high-purity methyl acrylate. Increasing purity can avoid the influence of other impurities on the performance of epoxy resin materials. The purified methyl acrylate and benzoyl peroxide are added to the epoxy resin and mixed at 75 ℃-80 ℃ to obtain a mixed solution. Under the action of the initiator, methyl acrylate undergoes a free radical polymerization reaction to generate polymethyl acrylate, which plays a toughening role in the epoxy resin system. Then, a curing agent is added and stirred for 30 min. Finally, an accelerator is added and stirred for 2-3 min, followed by ultrasonic degassing. Finally, the mixture is poured into a pretreated mold for curing to obtain the polymethyl acrylate / epoxy resin composite material.

[0020] (2) The polymethyl acrylate / epoxy resin composite material prepared by the method of this invention has good mechanical properties. When methyl acrylate and benzoyl peroxide are added to the epoxy resin matrix, a free radical polymerization reaction occurs at a certain temperature to produce polymethyl acrylate. When the epoxy resin composite material is subjected to external impact or tension, polymethyl acrylate, as a flexible polymer, can absorb some of the external force energy through its molecular chain segments, alleviating stress concentration in the epoxy resin matrix. Furthermore, during crack propagation, it can inhibit crack propagation, causing cracks to branch or deflect, extending the crack propagation path, and ultimately improving the mechanical properties of the epoxy resin material. Its dielectric properties and breakdown strength are also maintained. Therefore, it is very suitable as an insulator base material and can also be applied in various industries such as electronics, electrical appliances, and automobiles. Moreover, the epoxy resin composite material preparation process used in this invention is simple and relatively low-cost, providing a feasible solution for large-scale production applications, and also providing a good strategy for developing new high-toughness epoxy resin composite materials.

[0021] For a deeper understanding of the features and technical content of this invention, please refer to the accompanying detailed description and drawings. It should be noted that the drawings are provided for illustrative purposes only and are not intended to limit the scope of the invention. Attached Figure Description

[0022] Figure 1 Fourier transform infrared (FTIR) spectra of methyl acrylate (ME) and polymethyl acrylate / epoxy resin composites; a represents ME. b represents an epoxy resin composite with 2 wt% ME, c represents an epoxy resin composite with 4 wt% ME, d represents an epoxy resin composite with 6 wt% ME, and e represents an epoxy resin composite with 8 wt% ME.

[0023] Figure 2 Scanning electron microscope (SEM) images of tensile and bending test sections of a composite material consisting of pure epoxy resin and epoxy resin with 4 wt% methyl acrylate added. Figure 2 a)-d) represent the tensile cross-section of pure epoxy resin, the bending cross-section of pure epoxy resin, the tensile cross-section of 4 wt% polymethyl acrylate / epoxy resin composite material, and the bending cross-section of 4 wt% polymethyl acrylate / epoxy resin composite material, respectively.

[0024] Figure 3 X-ray diffraction patterns of pure epoxy resin and epoxy resins with different methyl acrylate mass fractions are shown. a represents pure epoxy resin material without methyl acrylate, b represents epoxy resin composite material with 2 wt% methyl acrylate, c represents epoxy resin composite material with 4 wt% methyl acrylate, d represents epoxy resin composite material with 6 wt% methyl acrylate, and e represents epoxy resin composite material with 8 wt% methyl acrylate.

[0025] Figure 4 The diagram shows the tensile strength test results of pure epoxy resin and epoxy resin composites with different methyl acrylate mass fractions; a represents pure epoxy resin material without methyl acrylate, b represents epoxy resin composite material with 2 wt% methyl acrylate mass fraction, c represents epoxy resin composite material with 4 wt% methyl acrylate mass fraction, d represents epoxy resin composite material with 6 wt% methyl acrylate mass fraction, and e represents epoxy resin composite material with 8 wt% methyl acrylate mass fraction.

[0026] Figure 5The diagram shows the flexural strength test results of pure epoxy resin and epoxy resin composites with different methyl acrylate mass fractions; a represents pure epoxy resin material without methyl acrylate, b represents epoxy resin composite material with 2 wt% methyl acrylate mass fraction, c represents epoxy resin composite material with 4 wt% methyl acrylate mass fraction, d represents epoxy resin composite material with 6 wt% methyl acrylate mass fraction, and e represents epoxy resin composite material with 8 wt% methyl acrylate mass fraction.

[0027] Figure 6 The graph shows the dielectric constant of pure epoxy resin and epoxy resin composites with different methyl acrylate mass fractions; ■ indicates pure epoxy resin material without methyl acrylate, ● indicates epoxy resin composite material with 2 wt% methyl acrylate mass fraction, ▲ indicates epoxy resin composite material with 4 wt% methyl acrylate mass fraction, ▼ indicates epoxy resin composite material with 6 wt% methyl acrylate mass fraction, and ◆ indicates epoxy resin composite material with 8 wt% methyl acrylate mass fraction.

[0028] Figure 7 The graph shows the dielectric loss test results of pure epoxy resin and epoxy resin composites with different methyl acrylate mass fractions; ■ indicates pure epoxy resin material without methyl acrylate, ● indicates epoxy resin composite material with 2 wt% methyl acrylate mass fraction, ▲ indicates epoxy resin composite material with 4 wt% methyl acrylate mass fraction, ▼ indicates epoxy resin composite material with 6 wt% methyl acrylate mass fraction, and ◆ indicates epoxy resin composite material with 8 wt% methyl acrylate mass fraction.

[0029] Figure 8 This diagram shows the breakdown strength test results of pure epoxy resin and epoxy resin composites with different methyl acrylate mass fractions; ■ indicates pure epoxy resin material without methyl acrylate, ● indicates epoxy resin composite material with 2 wt% methyl acrylate mass fraction, ▲ indicates epoxy resin composite material with 4 wt% methyl acrylate mass fraction, ▼ indicates epoxy resin composite material with 6 wt% methyl acrylate mass fraction, and ◆ indicates epoxy resin composite material with 8 wt% methyl acrylate mass fraction. Detailed Implementation

[0030] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0031] Example 1: The preparation method of a polymethyl acrylate / epoxy resin composite material in this example is carried out according to the following steps: Step 1: Purify methyl acrylate: Methyl acrylate was added to a distillation flask, and nitrogen gas was introduced into the flask to purge the air inside. The distillation flask was placed in an oil bath, and a vacuum pump was connected to evacuate the flask to a pressure of about 0.08 MPa. The oil bath temperature was slowly increased until the liquid began to boil, while maintaining a distillate flow rate of 1-2 drops / second. The distillate was collected to obtain high-purity methyl acrylate.

[0032] Step 2: Preparation of methyl acrylate / epoxy resin composite material: Weigh 25 g of DGEBA type epoxy resin, add 0.5 g of methyl acrylate to the epoxy resin and stir at 80 °C until the solution is homogeneous (takes about 3 h). Then add 0.05 g of benzoyl peroxide to the mixed solution and continue stirring until homogeneous (takes about 12 h) to obtain methyl acrylate / epoxy resin solution. Benzoyl peroxide needs to be dried in an oven at 60 °C for 3 h before use.

[0033] Add 21.25 g of methylhexahydrophthalic anhydride to the obtained solution and continue stirring until homogeneous (approximately 0.5-1 h). Then, add 0.25 g of 2,4,6-tris(dimethylaminomethyl)phenol dropwise at a rate of 2 drops / second, stirring for 5 min after the addition is complete. Place the stirred solution in an ultrasonicator and sonicate at 60 ℃ for 1 h to remove air bubbles. Pour the sonicated solution into a mold for curing. Clean the mold surface with alcohol to remove impurities, then place the mold in an oven at 80 ℃ for drying and preheating. During curing, maintain the oven temperature at 80 ℃ for 2 h, then at 100 ℃ for 2 h, and finally at 120 ℃ for 2 h. After curing, remove the mold and allow it to cool before unmolding the sample for subsequent testing.

[0034] Example 2: This example differs from Example 1 in that the mass fraction of methyl acrylate is 4 wt% of the epoxy resin. All other experimental conditions are the same as in Example 1.

[0035] Example 3: This example differs from Example 1 in that the mass fraction of methyl acrylate is 6 wt% of the epoxy resin. All other experimental conditions are the same as in Example 1.

[0036] Example 4: This example differs from Example 1 in that the mass fraction of methyl acrylate is 8 wt% of the epoxy resin. All other experimental conditions are the same as in Example 1.

[0037] Example 5: In this example, step one of Example 1 is not performed, and a mixed solution of epoxy resin and methylhexahydrophthalic anhydride is directly prepared in step two. All other experimental conditions are the same as in Example 1.

[0038] Fourier transform infrared spectra of methyl acrylate and epoxy resin composites with different methyl acrylate mass fractions are shown below. Figure 1 As shown; according to the infrared spectrum, at a wavenumber of 2954 cm⁻¹ -1 The absorption peak corresponds to the characteristic peak of methyl (-CH3) at a wavenumber of 1729 cm⁻¹. -1 The absorption peak corresponds to the carbon-oxygen double bond (C=O), at a wavenumber of 1635 cm⁻¹. -1 The absorption peak corresponds to the characteristic peak of a carbon-carbon double bond (C=C). This indicates that methyl acrylate has been successfully incorporated into the epoxy resin composite material.

[0039] Scanning electron microscope (SEM) images of tensile and flexural sections of a composite material consisting of pure epoxy resin and epoxy resin with 4 wt% methyl acrylate added are shown below. Figure 2 As shown, the tensile and bending fracture surfaces of pure epoxy resin are relatively smooth, with straight crack propagation paths, exhibiting typical brittle fracture characteristics. In contrast, the tensile and bending fracture surfaces of the epoxy resin composite material with 4 wt% methyl acrylate added are significantly rougher, and some micro-shear bands appear. The crack propagation path shows that some cracks branched and deflected during the propagation process.

[0040] X-ray diffraction patterns of pure epoxy resin and epoxy resins with different methyl acrylate mass fractions are shown below. Figure 3 As shown, since both epoxy resin and polymethyl acrylate are amorphous, they cannot form regular crystal plane diffraction patterns. Therefore, the images mainly show diffuse broad peaks, and the in-situ polymerization method does not change the amorphous structure of epoxy resin. Thus, the X-ray diffraction patterns do not show significant changes before and after the addition of methyl acrylate.

[0041] Tensile stress test results for pure epoxy resin and epoxy resin composites with different methyl acrylate mass fractions are shown in the figure. Figure 4 As shown; by Figure 4It can be seen that with the increase of methyl acrylate mass fraction, the tensile strength of epoxy resin composites first increases and then decreases. The tensile strength of pure epoxy resin is 53.38 MPa. When the methyl acrylate mass fraction is 4 wt% of epoxy resin, the tensile strength is the strongest, reaching 71.23 MPa. The polyacrylic acid elastomer produced by free radical polymerization exists in the epoxy resin system in the form of tiny particles. When the amount of methyl acrylate added is low, these particles, as stress concentration points, can be uniformly dispersed in the epoxy resin, effectively inducing shear yielding of the epoxy matrix and forming micro-shear bands. Because this plastic deformation process can absorb a large amount of energy, a higher external force is required to cause the composite material to fracture compared to pure epoxy resin, thus increasing the tensile strength of the epoxy resin composite. However, when the amount of methyl acrylate added is too high, it easily leads to the agglomeration of polymethyl acrylate particles, resulting in these particles being too large and irregularly shaped, thus becoming stress defect points. When an external force is applied to an epoxy resin material, the stress is highly concentrated at the defect point, eventually leading to the formation of cracks and a decrease in the tensile strength of the epoxy resin.

[0042] The flexural strength test results of pure epoxy resin and epoxy resin composites with different methyl acrylate mass fractions are shown in the figure below. Figure 5 As shown; by Figure 5 It can be seen that with the increase of methyl acrylate content, the flexural strength of epoxy resin composites also shows a trend of first increasing and then decreasing. The flexural strength of pure epoxy resin is 98.64 MPa. When the mass fraction of methyl acrylate is 4 wt% of epoxy resin, the flexural strength is the strongest, reaching 143.16 MPa. In the flexural strength test, when one side of the epoxy resin material is subjected to impact and bending, the other side will be subjected to the maximum tensile stress. When the methyl acrylate content is low, the uniformly distributed polyacrylic elastomer particles can effectively induce plastic deformation and absorb energy at the tensile point, delaying the formation of surface cracks. When cracks are formed, the presence of polyacrylic elastomer particles can hinder crack propagation, thus improving the flexural strength of epoxy resin. With the increase of methyl acrylate addition, the introduction of excessive flexible segments into the epoxy resin matrix will reduce the overall modulus of the material, resulting in a decrease in material rigidity. Under the same deformation, the bending resistance of the low modulus is weakened. Furthermore, the increased content of polyacrylic elastomer leads to larger agglomerates in the epoxy resin matrix. When these larger agglomerates appear on the surface, they can easily become the starting point for cracking, ultimately resulting in a decrease in the material's bending resistance.

[0043] The dielectric constant test results for pure epoxy resin and epoxy resin composites with different methyl acrylate mass fractions are shown in the figure below. Figure 6 As shown; by Figure 6It can be seen that the dielectric constant first increases and then decreases with the increase of methyl acrylate mass fraction. The ester groups in methyl acrylate, as strongly polar groups, increase the density of polar groups in the epoxy resin composite material after introduction. Under the action of an external electric field, the polar groups, acting as dipole carriers, undergo dipole orientation polarization. This polarization intensity is greater than atomic and electronic polarization, allowing the epoxy resin composite material to store more charge, thereby increasing the dielectric constant of the composite material. With the increase of methyl acrylate content, the viscosity of the epoxy resin composite system increases, restricting molecular chain movement and making it difficult for the polar groups to be effectively oriented under the action of the electric field, leading to a decrease in the dielectric constant.

[0044] Dielectric loss test graphs of pure epoxy resin and epoxy resin composites with different methyl acrylate mass fractions. Figure 7 As shown; by Figure 7 It can be seen that with the increase of methyl acrylate content, the dielectric loss does not change significantly at low frequencies, but shows a trend of first increasing and then decreasing at high frequencies. When the amount of methyl acrylate added is low, the ester group dipoles can quickly complete the orientation with the change of the high-frequency electric field, the number of effectively relaxable dipoles increases and the relaxation resistance is small, resulting in an increase in dielectric loss at high frequencies. As the amount of methyl acrylate added increases, large polyacrylic acid aggregates appear in the epoxy resin system, with a large number of ester groups encapsulated within them, thus restricting their movement. Under the high-frequency electric field, the relaxation time of the ester group dipoles is longer than the electric field period, and they cannot complete the orientation within the period, resulting in a decrease in the number of effectively relaxable dipoles and a decrease in dielectric loss.

[0045] The breakdown strength test results of pure epoxy resin and epoxy resin composites with different methyl acrylate mass fractions are shown in the figure below. Figure 8 As shown, the breakdown strength of epoxy resin composites first increases and then decreases with increasing methyl acrylate (Macrylate) content. The breakdown strength of pure epoxy resin is 70.64 KV / mm, while it increases to 81.21 KV / mm when the mass fraction of Macrylate is 6 wt%. Introducing Macrylate into epoxy resin introduces charge traps at the interface or in the matrix of the composite material. These traps can capture charge carriers, thereby inhibiting charge migration and accumulation in the material, thus improving the breakdown strength of the epoxy resin.

[0046] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. A method for preparing a polymethyl methacrylate / epoxy resin composite material, characterized in that, Includes the following steps: Step 1: After purifying methyl acrylate, add it to epoxy resin, heat and stir until uniform, then add initiator and continue stirring until uniform; Step 2: Then add the curing agent and continue stirring until the solution is clear. Then add the accelerator drop by drop and degas using ultrasound. Step 3: Then pour it into the pretreated mold, and cure it by step heating to obtain the composite material.

2. The method according to claim 1, characterized in that, Purification was carried out by vacuum distillation, with heating and stirring at 75 °C.

3. The method according to claim 1, characterized in that, The amount of methyl acrylate added is 2%-8% of the mass fraction of epoxy resin, the initiator is benzoyl peroxide, and the mass ratio of methyl acrylate to initiator is (0.5-2):(0.025-0.1).

4. The method according to claim 1, characterized in that, The curing agent is methylhexahydrophthalic anhydride or methyltetrahydrophthalic anhydride.

5. The method according to claim 1, characterized in that, The accelerator is 2,4,6-tris(dimethylaminomethyl)phenol.

6. The method according to claim 1, characterized in that, The mass ratio of curing agent to epoxy resin is (20-22):(22.5-25).

7. The method according to claim 1, characterized in that, The mass ratio of accelerator to epoxy resin is (0.22-0.25):(22.5-25).

8. The method according to claim 1, characterized in that, Stepwise temperature curing: hold at 80℃ for 2 hours, then at 100℃ for 2 hours, and finally at 120℃ for 2 hours.

9. A polymethyl acrylate / epoxy resin composite material prepared by the method according to any one of claims 1-8.

10. A polymethyl methacrylate / epoxy resin composite material prepared by the method of any one of claims 1-8 is used as a base material for insulator equipment.

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