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

Abstract

The invention discloses an insulating epoxy resin based on a plant derived material and a preparation method thereof. The preparation method comprises the following steps: adding resveratrol, tannic acid and epoxidized soybean oil into a solvent, uniformly mixing, stirring and dissolving, heating to remove the solvent, putting into a mold, exhausting air, and curing at high temperature to obtain the insulating epoxy resin. Wherein the mass fraction of the resveratrol is 3.28%-9.80%, the mass fraction of the tannic acid is 20.44%-26.47%, and the mass fraction of the epoxidized soybean oil is 69.76%-70.24%. The insulating epoxy resin based on the plant derived material prepared by the invention has good insulating ability and mechanical properties, and is suitable for preparing electrical insulating materials. The insulating epoxy resin prepared by the one-step synthesis method provided by the invention has the characteristics that the components are completely derived from renewable organisms, the process is simple, the operability is high, and the insulating epoxy resin is suitable for industrial popularization.

Description

Technical Field

[0001] The 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] As electronic components are rapidly developing towards high integration and high power density, more stringent requirements are placed on the insulation and mechanical properties of packaging materials. In this context, epoxy resin has become an ideal choice for power module packaging materials due to its excellent electrical insulation properties, excellent mechanical strength and outstanding high temperature resistance. However, after curing, epoxy resin exhibits insoluble and infusible properties, which significantly limits its degradability and reprocessing performance, and also makes it difficult to effectively recycle waste materials. Therefore, it is particularly important to develop bio-based degradable epoxy resin materials prepared from renewable biomass raw materials.

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

[0004] At present, there have been studies on the use of biomass materials such as resveratrol, starch, and tannic acid to introduce epoxy resin systems. For example, CN116789618A discloses that resveratrol and epichlorohydrin are heated to react to prepare biomass epoxy monomers. Since the epoxy monomer is prepared from resveratrol and epichlorohydrin as raw materials to prepare epoxy resin, on the one hand, its preparation process is complicated and engineering is poor; on the other hand, its scheme involves epichlorohydrin and related solvents and reaction synthesis conditions, which have a great impact on the environment, do not conform to the concept of environmental protection, and run counter to the concept of green material research and development. For example, CN105131253A discloses that tannic acid is added to the epoxy resin formula through a certain reaction to prepare a tannic acid-modified epoxy resin composite material. The entire process uses tannic acid and anhydride to jointly cure ordinary epoxy resin. Both anhydride and epoxy resin are petroleum-based derivative organic matter, which also does not conform to the concept of green environmental protection. CN110229531A discloses a completely bio-based epoxy resin composite material and a preparation method thereof, wherein the composite material is obtained by curing epoxy-modified starch, bio-based epoxy resin and bio-based curing agent. However, on the one hand, the modifier used in the preparation of epoxy-modified starch by the method uses aliphatic hydrocarbons containing halogen terminal groups, which may cause the material to release toxic hydrogen halide gas when burned, violating the original intention of the design of environmentally friendly materials and limiting its application in the fields of electrical materials; on the other hand, epoxy-modified starch requires multi-step synthesis, high quality control difficulty and poor engineering performance.

[0005] In summary, the development of a green epoxy material with high engineering properties, no harmful solvents, and no 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 view of the current situation that the synthesis method of existing epoxy resin involves the addition of harmful solvents and non-bio-based petroleum derivatives, which causes great pressure on resources and the environment, the purpose of the present invention is to provide an insulating epoxy resin based on plant-derived materials and a preparation method thereof. The insulating epoxy resin component of the present invention is completely bio-based, low in price, and has good insulation ability and mechanical properties. It is a green and environmentally friendly material, environmentally friendly, and easy to achieve industrial production.

[0007] The technical solution adopted by the present invention is as follows.

[0008] The present invention provides an insulating epoxy resin based on plant-derived materials, wherein the epoxy resin is obtained by mixing and curing an epoxy resin monomer and a curing agent, wherein 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] The present invention provides a method for preparing an insulating epoxy resin based on plant-derived materials, which adopts a one-step synthesis method. The specific method is as follows: 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 cured at high temperature to obtain the insulating epoxy resin based on plant-derived materials.

[0012] Furthermore, the molar ratio of resveratrol to tannic acid is (1-3):(7-9).

[0013] More preferably, the molar ratio of resveratrol to tannic acid is 1:9.

[0014] Furthermore, the solvent is one of acetone, methanol and isopropanol.

[0015] Furthermore, the stirring and dissolving temperature is room temperature, and the stirring and dissolving time is 5-10 minutes.

[0016] Furthermore, the heating method is oil bath heating, the heating temperature is 75-80° C., and the heating time is 90-120 minutes.

[0017] Furthermore, the pumping is performed under vacuum conditions for 120-150 minutes.

[0018] Furthermore, the conditions for high temperature curing 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.

[0019] Furthermore, the sample formed by high temperature curing is cooled to room temperature to obtain the target product.

[0020] 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 insulating materials, including electronic device packaging materials and electrical equipment insulating materials.

[0021] Tannic acid is a harmless compound with anti-allergic, anti-atherosclerotic and antibacterial properties; resveratrol is a natural polyphenol compound with low molecular weight and regular structure. The molecules of these two plant derivatives have high aromatic content and a large number of phenolic hydroxyl groups. The high aromaticity provides excellent mechanical properties and stability for epoxy resin, and can cross-link with epoxy soybean oil at multiple sites, increase the cross-linking density of epoxy resin, and help improve polymer performance.

[0022] The present invention uses resveratrol and tannic acid as epoxy resin curing agents, and investigates the influence of the use ratio of resveratrol and tannic acid on the mechanical properties and insulation properties of epoxy resin composite materials after curing. The mechanical properties and insulation properties of epoxy resin samples obtained when the molar ratio of resveratrol to tannic acid is 1:9; 2:8; 3:7; 4:6; 5:5; 6:4 are tested respectively. The results show that when the molar ratio of resveratrol to tannic acid is 1:9; 2:8; 3:7, the mechanical properties and insulation properties of the epoxy resin are significantly improved compared with the epoxy resin synthesized when the molar ratio of resveratrol to tannic acid is 4:6; 5:5; 6:4. When the molar ratio of resveratrol to tannic acid is 1:9, the synthesized epoxy resin has the best insulation performance, and its resistivity is 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.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects: (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 is fully in line with the concept of green and environmentally friendly plastic research and development.

[0024] (2) The all-biobased insulating epoxy resin prepared by the method of the present invention has good insulating ability and mechanical properties, thereby effectively protecting the 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

[0025] Figure 1 The schematic diagram of the synthesis principle of the insulating epoxy resin based on plant-derived materials in one step of the present invention is shown.

[0026] Figure 2(a) to Figure 2(d) Fourier transform infrared spectra (FT-IR) of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3.

[0027] Figure 3 Scanning electron microscope (SEM) images of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3.

[0028] Figure 4 The differential scanning calorimetry (DSC) diagrams of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3 are shown.

[0029] FIG. 5( a ) and FIG. 5( b ) are respectively a broadband dielectric constant diagram and a dielectric loss tangent diagram of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3. FIG.

[0030] Figure 6 The graphs are breakdown strength graphs of the epoxy resins prepared in Examples 1-3 and Comparative Examples 1-3, wherein (a) is a breakdown strength function graph, and (b) is a graph showing the relationship between shape parameters and breakdown strength.

[0031] 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

[0032] The specific implementation of the present invention is further described below in conjunction with examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are processes that are not particularly described in detail 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.

[0033] The resveratrol (RES) used in the following examples or comparative examples was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a concentration of 99%.

[0034] The tannic acid (Gallotannic acid, referred to as TA) used in the following examples or comparative examples was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a concentration of 99%.

[0035] The epoxidized soybean oil (ESO) used in the following examples or comparative examples was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a concentration of 99%.

[0036] Figure 1 The schematic diagram of the synthesis principle of the insulating epoxy resin based on plant-derived materials in one step of the present invention is as follows: epoxy soybean oil as an epoxy resin monomer and tannic acid and resveratrol as epoxy resin curing agents are fully mixed, stirred for reaction, and subjected to high-temperature curing after vacuum degassing; due to the large amount of phenolic hydroxyl groups contained in resveratrol and tannic acid molecules, the phenolic hydroxyl groups of resveratrol and tannic acid are respectively released from epoxy groups at high temperatures, and respectively form highly cross-linked polyether structures with the epoxy soybean oil, and finally form a three-dimensional cross-linked network.

[0037] Example 1 An insulating epoxy resin based on plant-derived materials, the specific preparation steps are as follows: 30 ml of acetone was used as solvent, and 0.3804 g of resveratrol powder, 3.0618 g of tannic acid powder, and 8.126 g of epoxidized soybean oil were added in sequence, mixed evenly, and stirred to dissolve, to obtain a light yellow transparent mixed solution, which was heated in an 80°C oil bath for 90 minutes to completely evaporate the acetone in the mixed solution, poured into a metal mold, and vacuum-evacuated for 120 minutes before high-temperature curing. The conditions for high-temperature curing were: first, curing at 120°C for 60 minutes, then curing at 150°C for 120 minutes, then curing at 180°C for 120 minutes, and finally curing at 210°C for 60 minutes. After curing, the sample was taken out and cooled to room temperature, and the obtained epoxy resin sample was recorded as ESO-TA-RES09 (where 09 means that the molar ratio of resveratrol to tannic acid is 1:9).

[0038] Example 2 An insulating epoxy resin based on plant-derived materials, which is different 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 are added and mixed evenly, and the remaining operation steps and conditions are the same as those of Example 1. The obtained epoxy resin sample is recorded as ESO-TA-RES08 (where 08 indicates that the molar ratio of resveratrol to tannic acid is 2:8).

[0039] Example 3 An insulating epoxy resin based on plant-derived materials, which is different 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 are added and mixed evenly, and the remaining operation steps and conditions are the same as those of Example 1. The obtained epoxy resin sample is recorded as ESO-TA-RES07 (where 07 indicates that the molar ratio of resveratrol to tannic acid is 3:7).

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that 1.5216 g of resveratrol powder, 2.0412 g of tannic acid powder, and 8.126 g of epoxidized soybean oil are added and mixed evenly, and the remaining operation steps and conditions are the same as those of Example 1. The obtained epoxy resin sample is recorded as ESO-TA-RES06 (where 06 indicates that the molar ratio of resveratrol to tannic acid is 4:6).

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that 1.9020 g of resveratrol powder, 1.7010 g of tannic acid powder, and 8.126 g of epoxidized soybean oil are added and mixed evenly, and the remaining operation steps and conditions are the same as those of Example 1. The obtained epoxy resin sample is recorded as ESO-TA-RES05 (where 05 indicates that the molar ratio of resveratrol to tannic acid is 5:5).

[0042] Comparative Example 3 The difference between this comparative example and Example 1 is that 2.2824 g of resveratrol powder, 1.3608 g of tannic acid powder, and 8.126 g of epoxidized soybean oil are added and mixed evenly, and the remaining operation steps and conditions are the same as those of Example 1. The obtained epoxy resin sample is recorded as ESO-TA-RES04 (where 04 indicates that the molar ratio of resveratrol to tannic acid is 6:4).

[0043] Performance Testing 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 -1The 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 above data, indicating the successful synthesis of the target product.

[0044] 2. The 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 Example 1-3 is relatively rough. This is because when the content of RES is increased to a certain level, the molecular chain structure of RES is relatively rigid, which hinders the full reaction between ESO and TA, resulting in a large number of TA insoluble particles on the surface of Comparative Example 1-3, and severe phase separation occurred during the curing process (the compatibility between TA particles and the epoxy resin matrix is ​​poor). During the curing process, these components cannot be evenly dispersed in the resin matrix, but form independent phases and precipitate, which makes the epoxy resin incompletely cross-linked.

[0045] 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 4 As shown. DSC (Differential Scanning Calorimetry) is a thermal analysis technique that analyzes the thermal effect of a material during a temperature change by measuring the heat difference between the sample and the reference. The core principle is to keep the sample and reference temperatures consistent, monitor the difference in heat flow required to maintain the temperature balance 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). 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.

[0046] 4. The broadband dielectric constant diagram and dielectric loss tangent diagram of the epoxy resin prepared in Examples 1-3 and Comparative Examples 1-3 are shown in Figures 5(a) and 5(b), respectively. TA is a very polar molecule, and in Comparative Examples 1-3, due to the presence of a large number of phenolic hydroxyl groups in a large number of undissolved TA particles (especially Comparative Example 3), the overall polarity of the polymer is higher than that of other samples, showing the highest dielectric constant (as shown in Figure 5(a)). In addition, insufficient cross-linking will lead to an increase in stray capacitance between polymer molecules, which is also the reason why the dielectric constant of the samples in Comparative Examples 1-3 is higher than that of Examples 1-3.

[0047] Comparative Example 3 has the highest tanδ, followed by Comparative Example 2, and the tanδ of other samples are close. This is also because when the content of resveratrol in the mixture increases to a certain level, it hinders the full reaction between ESO and TA, the undissolved TA particles have high conductivity, and the interface loss between the polymer and TA particles will also increase the energy loss of the epoxy resin material (as shown in Figure 5(b)). In addition, due to the strong polarity of TA molecules, the samples show high polarization loss at high frequencies.

[0048] 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 (Formula 1) was used to calculate the breakdown strength of different samples.

[0049] p=1-exp[-(E / E0) β ], E>0 (Formula 1) In Formula 1, p represents the failure probability of the breakdown strength; E is the breakdown strength of different epoxy resin (EP) systems obtained from the test; β is the shape parameter, which represents the distribution of the breakdown field strength; E0 is the breakdown strength when P = 63.2%, which is regarded as the intrinsic breakdown strength of each sample.

[0050] like Figure 6As 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 V, 32.90 kV / mm, 30.76 kV / mm, and 26.58 kV / mm, respectively, which are all greater than the breakdown strength of ordinary epoxy resin (about 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 a low free volume, resulting in a significant improvement in the breakdown strength compared to ordinary epoxy. Among them, the breakdown strength of Example 1 is the highest, reaching 36.06 kV / mm, which is about 30% higher than that of ordinary epoxy resin. The undissolved TA particles in Comparative Examples 1-3 cause severe phase separation, resulting in serious sample defects and decreased breakdown strength. In addition, due to the different results of crosslinking density and free volume defects 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.

[0051] 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) in the figure, 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.

[0052] Combining the results of the above SEM with the dielectric constant and dielectric loss, it can be seen that the epoxy resins prepared in Examples 1-3 have no obvious particles, basically no phase separation, and a large volume resistivity. The samples all meet the insulation conditions, and Example 1 is the best. Under the condition of good polymer homogeneity, the current will not be transmitted along the surface at the interface and gap in the polymer; at the same time, it is noted that the high cross-linking degree brought to the entire polymer by tannic acid with multiple cross-linking sites and resveratrol with a rigid structure triphenolic hydroxyl as a curing agent affects the transport of charge in the material, resulting in the highest volume resistivity. The undissolved TA particles in Comparative Examples 1-3 cause severe phase separation, which seriously reduces the volume resistivity of the epoxy resins prepared in Comparative Examples 1-3, resulting in 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%.

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, heated to remove the solvent, placed in a mold, evacuated, and cured at high temperature to obtain the insulating epoxy resin based on plant-derived materials.

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 (1-3):(7-9).

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

9.

5. 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.

6. 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.

7. The method for preparing an insulating epoxy resin based on plant-derived materials according to claim 2, characterized in that: The heating method is oil bath heating, the heating temperature is 75-80° C., and the heating time is 90-120 minutes.

8. 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.

9. 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.

10. Use of the insulating epoxy resin based on plant-derived materials as claimed in claim 1 in the preparation of electrical insulating materials.

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