Insulating epoxy resin based on plant-derived materials and preparation method thereof

Abstract

The present invention discloses an insulating epoxy resin based on plant-derived materials and a preparation method thereof. Resveratrol, tannic acid, and epoxy soybean oil are added to a solvent, mixed evenly and stirred to dissolve, heated to remove the solvent, placed in a mold, evacuated, and high-temperature cured to obtain the insulating epoxy resin. Wherein, the mass fraction of resveratrol is 3.28%-9.80%, the mass fraction of tannic acid is 20.44%-26.47%, and the mass fraction of epoxy soybean oil is 69.76%-70.24%. The insulating epoxy resin based on plant-derived materials prepared by the present invention has good insulating ability and mechanical properties, and is suitable for the preparation of electrical insulating materials. The one-step synthesis method provided by the present invention is used to prepare an insulating epoxy resin, which has the characteristics that the components are completely derived from renewable organisms, the process is simple, and the operability is strong, and it is suitable for industrial promotion.

Description

Technical Field

[0001] The present invention relates to the technical field of bio-based epoxy resin composite materials, and in particular to an insulating epoxy resin based on plant-derived materials and a preparation method thereof. Background Art

[0002] The rapid development of electronic components toward higher integration and higher power density places increasingly stringent demands on the insulation and mechanical properties of packaging materials. In this context, epoxy resin, with its superior electrical insulation properties, excellent mechanical strength, and outstanding high-temperature resistance, has become an ideal choice for power module packaging materials. However, after curing, epoxy resin exhibits insoluble and infusible properties, significantly limiting its degradability and reprocessability, and making it difficult to effectively recycle waste materials. Therefore, the development of biodegradable epoxy resin materials made from renewable biomass feedstocks is particularly important.

[0003] Research on bio-based epoxy resins based on renewable resources offers innovative solutions to the environmental challenges of traditional epoxy resins. By incorporating biomass materials such as plant fibers and starch into epoxy resin systems, new materials with excellent electrical and mechanical properties can be developed.

[0004] Current research has explored the use of biomass materials such as resveratrol, starch, and tannic acid in epoxy resin systems. For example, CN116789618A discloses a biomass epoxy monomer prepared by heating resveratrol and epichlorohydrin. However, since this epoxy monomer is prepared from resveratrol and epichlorohydrin, the epoxy resin is complicated and has poor engineering properties. Furthermore, the use of epichlorohydrin and related solvents, as well as the reaction and synthesis conditions, significantly impacts the environment, contradicting environmental principles and the development of green materials. For example, CN105131253A discloses a tannic acid-modified epoxy resin composite material prepared by adding tannic acid to an epoxy resin formula through a specific reaction. The entire process utilizes tannic acid and anhydride to cure conventional epoxy resin. Both the anhydride and epoxy resin are petroleum-derived organic compounds, similarly contradicting green principles. CN110229531A discloses a completely bio-based epoxy resin composite material and its preparation method. The composite material is obtained by curing epoxy-modified starch, a bio-based epoxy resin, and a bio-based curing agent. However, on the one hand, the modifier used in this method to prepare epoxy-modified starch uses an aliphatic hydrocarbon containing a halogen terminal group, which may cause the material to release toxic hydrogen halide gas when burned, violating the original design principle of environmentally friendly materials and limiting its application in fields such as electrical materials. On the other hand, epoxy-modified starch requires multiple steps to synthesize, which is difficult to control the quality and has poor engineering properties.

[0005] In summary, the development of a green epoxy material with high engineering properties, no harmful solvents, and no involvement of other petroleum-based derivatives is of great significance for the research and development of the next generation of green and environmentally friendly thermosetting plastics. Summary of the Invention

[0006] In response to the current situation in which existing epoxy resin synthesis methods involve the addition of harmful solvents and non-biobased petroleum derivatives, which places significant pressure on resources and the environment, the present invention aims to provide an insulating epoxy resin based on plant-derived materials and a method for its preparation. The insulating epoxy resin of the present invention is entirely bio-based, inexpensive, and exhibits excellent insulation and mechanical properties. It is a green, environmentally friendly material that is easily scalable and readily commercializable.

[0007] The technical solutions adopted by the present invention are as follows.

[0008] The present invention provides an insulating epoxy resin based on plant-derived materials. The epoxy resin is obtained by curing an epoxy resin monomer and a curing agent. The epoxy resin monomer is epoxidized soybean oil, and the curing agent is a bio-based epoxy resin curing agent composed of resveratrol and tannic acid.

[0009] In the insulating epoxy resin based on plant-derived materials, the mass fraction of resveratrol is 3.28%-9.80%, the mass fraction of tannic acid is 20.44%-26.47%, and the mass fraction of epoxidized soybean oil is 69.76%-70.24%.

[0010] Furthermore, the structural formulas of resveratrol, tannic acid, and epoxidized soybean oil are as follows:

[0011]

[0012] The present invention provides a method for preparing an insulating epoxy resin based on plant-derived materials, using a one-step synthesis method. The specific method is as follows:

[0013] Resveratrol, tannic acid, and epoxy soybean oil are added to a solvent, mixed evenly, and stirred to dissolve. After heating to remove the solvent, the mixture is placed in a mold, evacuated, and cured at high temperature to obtain the insulating epoxy resin based on plant-derived materials.

[0014] Furthermore, the molar ratio of resveratrol to tannic acid is (1-3):(7-9).

[0015] More preferably, the molar ratio of resveratrol to tannic acid is 1:9.

[0016] Furthermore, the solvent is one of acetone, methanol and isopropanol.

[0017] Furthermore, the stirring and dissolving temperature is room temperature, and the stirring and dissolving time is 5-10 minutes.

[0018] Furthermore, the heating method is oil bath heating, the heating temperature is 75-80° C., and the heating time is 90-120 minutes.

[0019] Furthermore, the pumping is carried out under vacuum conditions for 120-150 minutes.

[0020] Furthermore, the high temperature curing conditions are: first curing at 120° C. for 60 min, then curing at 150° C. for 120 min, then curing at 180° C. for 120 min, and finally curing at 210° C. for 60 min.

[0021] Furthermore, the sample formed by high-temperature curing is cooled to room temperature to obtain the target product.

[0022] The insulating epoxy resin based on plant-derived materials obtained by the one-step synthesis method has high dielectric breakdown performance and therefore has good application prospects in the preparation of electrical insulation materials, including electronic device packaging materials and electrical equipment insulation materials.

[0023] Tannic acid is a harmless compound with anti-allergic, anti-atherosclerotic, and antibacterial properties; resveratrol is a natural polyphenolic compound with a low molecular weight and a regular structure. These two plant derivatives have high aromatic content and numerous phenolic hydroxyl groups. This high aromaticity provides epoxy resin with excellent mechanical properties and stability. They also crosslink with epoxidized soybean oil at multiple sites, increasing the crosslink density of the epoxy resin and improving polymer performance.

[0024] The present invention utilizes resveratrol and tannic acid as epoxy resin curing agents and investigates the effect of the ratio of resveratrol to tannic acid on the mechanical and insulating properties of epoxy resin composites after curing. The mechanical and insulating properties of epoxy resin samples obtained with resveratrol:tannic acid molar ratios of 1:9, 2:8, 3:7, 4:6, 5:5, and 6:4 were tested. The results show that when the resveratrol:tannic acid molar ratio is 1:9, 2:8, and 3:7, the mechanical and insulating properties of the epoxy resin are significantly improved compared to those synthesized with the resveratrol:tannic acid molar ratio of 4:6, 5:5, and 6:4. When the resveratrol:tannic acid molar ratio is 1:9, the epoxy resin synthesized has the best insulating properties, with a resistivity of 5.38×10 12 (Ω·m), breakdown strength is 36.06kV / mm, dielectric constant ε is 3.18, and dielectric loss tangent tanδ is 0.009.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] (1) The present invention adopts a one-step method to synthesize a fully bio-based insulating epoxy resin based on plant-derived materials. Resveratrol, tannic acid, and epoxidized soybean oil are directly mixed and cured in proportion to obtain the resin. This one-step synthesis does not involve other multi-step chemical synthesis reactions. It has high engineering properties, does not add harmful solvents, and does not involve other petroleum-based derivatives. It fully complies with the concept of green and environmentally friendly plastic research and development.

[0027] (2) The all-biobased insulating epoxy resin prepared by the method of the present invention has good insulation ability and mechanical properties, thereby effectively protecting equipment from the hazards of high-voltage breakdown and partial discharge, and providing a new perspective and development direction for electronic device packaging materials and electrical equipment insulation materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the synthesis principle of the one-step synthesis of insulating epoxy resin based on plant-derived materials according to the present invention.

[0029] Figure 2(a) to Figure 2(d) Fourier transform infrared (FT-IR) spectra of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3.

[0030] Figure 3 Scanning electron microscope (SEM) images of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3.

[0031] Figure 4 The differential scanning calorimetry (DSC) graphs of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3 are shown.

[0032] FIG5(a) and FIG5(b) are respectively the broadband dielectric constant graph and the dielectric loss tangent graph of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3.

[0033] Figure 6 Graphs showing the breakdown strength of epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3, wherein (a) is a graph showing the breakdown strength function, and (b) is a graph showing the relationship between shape parameters and breakdown strength.

[0034] Figure 7 The volt-ampere characteristic curves and volume resistivity diagrams of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3, wherein (a) is the volt-ampere characteristic curve and (b) is the volume resistivity diagram. DETAILED DESCRIPTION

[0035] The following examples further illustrate the specific implementation of the present invention, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are any processes not specifically described below, they can be implemented or understood by those skilled in the art with reference to the prior art. If the manufacturer of the reagents or instruments used is not indicated, they are deemed to be conventional products that can be purchased commercially.

[0036] Resveratrol (RES) used in the following examples or comparative examples was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a concentration of 99%.

[0037] Tannic acid (Gallotannic acid, abbreviated as TA) used in the following examples or comparative examples was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a concentration of 99%.

[0038] The epoxidized soybean oil (ESO) used in the following examples and comparative examples was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a concentration of 99%.

[0039] Figure 1 This is a schematic diagram of the synthesis principle of the one-step synthesis of an insulating epoxy resin based on plant-derived materials according to the present invention. Epoxidized soybean oil, which serves as an epoxy resin monomer, and tannic acid and resveratrol, which serve as epoxy resin curing agents, are thoroughly mixed and stirred for reaction. After vacuum degassing, the mixture is then cured at high temperature. Due to the large number of phenolic hydroxyl groups contained in the resveratrol and tannic acid molecules, the phenolic hydroxyl groups of resveratrol and tannic acid respectively release the epoxy groups at high temperatures and form highly cross-linked polyether structures with the epoxidized soybean oil, ultimately forming a three-dimensional cross-linked network.

[0040] Example 1

[0041] An insulating epoxy resin based on plant-derived materials, the specific preparation steps are as follows:

[0042] To 30 ml of acetone as the solvent, 0.3804 g of resveratrol powder, 3.0618 g of tannic acid powder, and 8.126 g of epoxidized soybean oil were added, mixed thoroughly, and stirred to dissolve. This resulted in a pale yellow, transparent mixed solution. The solution was then heated in an 80°C oil bath for 90 minutes to completely evaporate the acetone. The solution was then poured into a metal mold and vacuum-evacuated for 120 minutes before high-temperature curing. The high-temperature curing conditions were: first, 120°C for 60 minutes, then 150°C for 120 minutes, then 180°C for 120 minutes, and finally 210°C for 60 minutes. After curing, the sample was removed and cooled to room temperature. The resulting epoxy resin sample was designated ESO-TA-RES09 (where 09 indicates a 1:9 molar ratio of resveratrol to tannic acid).

[0043] Example 2

[0044] An insulating epoxy resin based on plant-derived materials was prepared, differing from Example 1 in that 0.7608 g of resveratrol powder, 2.7216 g of tannic acid powder, and 8.126 g of epoxidized soybean oil were added and mixed uniformly. The remaining steps and conditions were the same as in Example 1. The resulting epoxy resin sample was designated ESO-TA-RES08 (where 08 indicates a molar ratio of resveratrol to tannic acid of 2:8).

[0045] Example 3

[0046] An insulating epoxy resin based on plant-derived materials was prepared, differing from Example 1 in that 1.1412 g of resveratrol powder, 2.3814 g of tannic acid powder, and 8.126 g of epoxidized soybean oil were added and mixed uniformly. The remaining steps and conditions were the same as in Example 1. The resulting epoxy resin sample was designated ESO-TA-RES07 (where 07 indicates a molar ratio of resveratrol to tannic acid of 3:7).

[0047] Comparative Example 1

[0048] This comparative example differs from Example 1 in that 1.5216 g of resveratrol powder, 2.0412 g of tannic acid powder, and 8.126 g of epoxidized soybean oil were added and mixed uniformly. The remaining steps and conditions were the same as in Example 1. The resulting epoxy resin sample was designated ESO-TA-RES06 (where 06 indicates a molar ratio of resveratrol to tannic acid of 4:6).

[0049] Comparative Example 2

[0050] This comparative example differs from Example 1 in that 1.9020 g of resveratrol powder, 1.7010 g of tannic acid powder, and 8.126 g of epoxidized soybean oil were added and mixed uniformly. The remaining steps and conditions were the same as in Example 1. The resulting epoxy resin sample was designated ESO-TA-RES05 (where 05 indicates a 5:5 molar ratio of resveratrol to tannic acid).

[0051] Comparative Example 3

[0052] This comparative example differs from Example 1 in that 2.2824 g of resveratrol powder, 1.3608 g of tannic acid powder, and 8.126 g of epoxidized soybean oil were added and mixed uniformly. The remaining steps and conditions were the same as in Example 1. The resulting epoxy resin sample was designated ESO-TA-RES04 (where 04 indicates a molar ratio of resveratrol to tannic acid of 6:4).

[0053] Performance Testing

[0054] 1. The Fourier transform infrared spectra (FT-IR) of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3 are as follows: Figure 2(a) to Figure 2(d) As shown in Figure 2(a), about 885 cm -1 The absorption peak at about 1360 cm -1 The CH-characteristic peak appears at about 1740 cm -1 The C=O characteristic peak representing the ester bond of RES and TA appears at about 1600 cm -1 Due to the aromatic benzene rings of TA and RES, C=C characteristic peaks appeared. Due to the polyphenol structure of TA and RES, the peaks at 3200-3600 cm -1 In addition, as shown in Figure 2(b), with the increase of ESO content, the peak of about 1440 cm representing the aliphatic CH stretching vibration -1 It is worth noting that, as shown in Figure 2(c), the CO stretching vibration (1120 cm -1 ) and the CCO stretching vibration of RES (1145 cm -1 In addition, as shown in Figure 2(d), about 2850 cm -1 and 2925 cm -1 The characteristic peaks representing the symmetric stretching vibration of methylene (-CH2-) and the asymmetric stretching vibration of methylene (-CH2-) appeared at the 400 nm wavelength, respectively. The above data indicate that the target product was successfully synthesized.

[0055] 2. Scanning electron microscope (SEM) images of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3 are as follows: Figure 3 As shown. No obvious insoluble particles appeared in the cross section of the epoxy resin prepared in Example 1-3. The cross section of the epoxy resin prepared in Comparative Examples 1-3 was relatively rough. This is because when the content of RES was increased to a certain level, the molecular chain structure of RES was relatively rigid, which hindered the full reaction between ESO and TA, resulting in a large number of TA insoluble particles on the surface of Comparative Examples 1-3. Severe phase separation occurred during the curing process (the compatibility between TA particles and the epoxy resin matrix was poor). During the curing process, these components could not be evenly dispersed in the resin matrix, but formed independent phases and precipitated, which made the epoxy resin incompletely cross-linked.

[0056] 3. The differential scanning calorimetry (DSC) graphs of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3 are as follows: Figure 4As shown. DSC (Differential Scanning Calorimetry) is a thermal analysis technique that analyzes the thermal effect of a material during temperature changes by measuring the heat difference between the sample and the reference. Its core principle is to keep the sample and reference temperatures consistent, monitor the difference in heat flow required to maintain temperature equilibrium between the two, and thus identify endothermic or exothermic processes. DSC can detect the glass transition temperature of a polymer (the temperature at which a polymer changes from a glassy state to a highly elastic state, and the DSC curve shows a step-like change in baseline offset). As shown Figure 4 As shown, the glass transition temperatures of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3 are 147.3°C, 145.5°C, 148.1°C, 147.9°C, 149.0°C, and 146.9°C, respectively.

[0057] 4. The broadband dielectric constant and dielectric loss tangent plots of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3 are shown in Figures 5(a) and 5(b), respectively. TA is a highly polar molecule, and due to the presence of numerous phenolic hydroxyl groups in the large number of undissolved TA particles in Comparative Examples 1-3 (especially Comparative Example 3), the overall polarity of the polymers is higher than that of the other samples, resulting in the highest dielectric constant (as shown in Figure 5(a)). Furthermore, insufficient cross-linking can increase the stray capacitance between polymer molecules, which contributes to the higher dielectric constants of the samples in Comparative Examples 1-3 than in Examples 1-3.

[0058] Comparative Example 3 has the highest tanδ, followed by Comparative Example 2. The tanδ values ​​of the other samples are similar. This is because increasing the resveratrol content in the mixture to a certain level hinders the full reaction between ESO and TA. Undissolved TA particles have high conductivity, and interfacial losses between the polymer and TA particles also increase energy loss in the epoxy resin material (as shown in Figure 5(b)). Furthermore, due to the strong polarity of TA molecules, the samples exhibit high polarization losses at high frequencies.

[0059] 5. The breakdown strength of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3 is shown in FIG. Figure 6 To further evaluate the insulation performance of the epoxy resin system, an electrical breakdown test was performed. The two-parameter Weibull distribution (Equation 1) was used to calculate the breakdown strength of different samples.

[0060] p=1-exp[-(E / E0) β ], E>0 (Formula 1)

[0061] In Equation 1, p represents the failure probability of breakdown strength; E is the breakdown strength of different epoxy resin (EP) systems obtained from the tests; β is the shape parameter, which represents the distribution of the breakdown field strength; and E0 is the breakdown strength at P = 63.2%, which is considered to be the intrinsic breakdown strength of each sample.

[0062] like Figure 6 As shown in (a), the breakdown strengths of Examples 1-3 and Comparative Examples 1-3 are 36.06 kV / mm, 35.41 kV / mm, 33.26 kV, 32.90 kV / mm, 30.76 kV / mm, and 26.58 kV / mm, respectively, all exceeding the breakdown strength of ordinary epoxy resin (approximately 25 kV / mm). This is because the macromolecular structure of tannic acid as a curing agent and the rigid structure of resveratrol give the entire epoxy polymer a high degree of crosslinking and low free volume, resulting in a significant improvement in breakdown strength compared to ordinary epoxy. Among them, Example 1 has the highest breakdown strength, reaching 36.06 kV / mm, which is approximately 30% higher than that of ordinary epoxy resin. The undissolved TA particles in Comparative Examples 1-3 cause severe phase separation, resulting in severe sample defects and a decrease in breakdown strength. In addition, due to the different crosslinking density and free volume defect results of different samples, their breakdown strength gradually decreases. In addition, the magnitude of the breakdown strength is also related to the shape parameter β, which can reflect the distribution of defects inside the polymer, because the breakdown damage usually starts from the micropores in the polymer material. Figure 6 As shown in (b), as the interface defects decrease, the defect density inside the sample decreases, resulting in a decrease in the shape parameter β from Comparative Example 3 to Example 1, thereby improving the breakdown strength.

[0063] 6. The volt-ampere characteristic curves and volume resistivity of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3 are shown in FIG. Figure 7 As shown. Figure 7 As can be seen from (a) in the figure, as the tannic acid content decreases, the current increases, indicating that the volume resistivity gradually decreases. Figure 7 As can be seen from (b), the volume resistivity of Examples 1-3 and Comparative Examples 1-3 is 5.38×10 12 Ω·m、5.073×10 12 Ω·m、4.048×10 12 Ω·m、3.232×10 12 Ω·m、2.512×10 12 Ω·m, 2.369×10 12 Ω·m.

[0064] Combining the above SEM results with the dielectric constant and dielectric loss results shows that the epoxy resins prepared in Examples 1-3 showed no obvious particles, essentially no phase separation, and high volume resistivity. All samples met insulation requirements, with Example 1 being the most optimal. Given the good polymer homogeneity, current does not propagate along the polymer interface or interstices. It is also noted that the high degree of crosslinking provided by the multi-crosslinking sites of tannic acid and the rigid triphenolic hydroxyl group of resveratrol as a curing agent affects charge transport within the material, resulting in the highest volume resistivity. Undissolved TA particles in Comparative Examples 1-3 caused severe phase separation, significantly reducing the volume resistivity of the epoxy resins prepared in Comparative Examples 1-3 and leading to poor insulation performance.

Claims

1. An insulating epoxy resin based on plant-derived materials, characterized in that The epoxy resin is obtained by mixing and curing an epoxy resin monomer and a curing agent; the epoxy resin monomer is epoxidized soybean oil, and the curing agent is a bio-based epoxy resin curing agent composed of resveratrol and tannic acid; In the insulating epoxy resin based on plant-derived materials, the mass fraction of resveratrol is 3.28%-9.80%, the mass fraction of tannic acid is 20.44%-26.47%, and the mass fraction of epoxidized soybean oil is 69.76%-70.24%; the molar ratio of resveratrol to tannic acid is (1-3):(7-9).

2. The method for preparing an insulating epoxy resin based on plant-derived materials according to claim 1, characterized in that: The following steps are involved: Resveratrol, tannic acid, and epoxy soybean oil are added to a solvent, mixed evenly, and stirred to dissolve. After heating to remove the solvent, the mixture is placed in a mold, evacuated, and cured at high temperature to obtain the insulating epoxy resin based on plant-derived materials. The heating method is oil bath heating, the heating temperature is 75-80°C, and the heating time is 90-120 minutes.

3. The method for preparing an insulating epoxy resin based on plant-derived materials according to claim 2, characterized in that: The molar ratio of resveratrol to tannic acid is 1:

9.

4. The method for preparing an insulating epoxy resin based on plant-derived materials according to claim 2, characterized in that: The solvent is one of acetone, methanol and isopropanol.

5. The method for preparing an insulating epoxy resin based on plant-derived materials according to claim 2, characterized in that: The temperature for stirring and dissolving is room temperature, and the time for stirring and dissolving is 5-10 minutes.

6. The method for preparing an insulating epoxy resin based on plant-derived materials according to claim 2, characterized in that: The pumping is carried out under vacuum conditions for 120-150 minutes.

7. The method for preparing an insulating epoxy resin based on plant-derived materials according to claim 2, characterized in that: The high temperature curing conditions are: first curing at 120° C. for 60 min, then curing at 150° C. for 120 min, then curing at 180° C. for 120 min, and finally curing at 210° C. for 60 min.

8. Use of the insulating epoxy resin based on plant-derived materials according to claim 1 in the preparation of electrical insulating materials.

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