Preparation method and application of high-heat-resistance and high-insulation composite material

Abstract

The invention discloses a preparation method and application of a high-heat-resistance and high-insulation composite material, and belongs to the technical field of preparation of high-heat-resistance and high-insulation composite materials. The invention aims to solve the problems that the existing epoxy resin composite material is low in heat resistance and poor in insulating property, the preparation process of the composite material is complicated, and the environment is polluted. The epoxy resin composite material with high heat resistance and excellent insulating property is obtained by designing the molecular structure of the curing agent and regulating and controlling the content of curing agents with different functions. The molecular structure and content regulation of the curing agent designed by the invention can obviously improve the heat resistance and insulating property of epoxy resin, and the curing agent is expected to be used as a heat-resistant insulating material for winding insulation. In addition, the high-heat-resistance and high-insulation epoxy resin composite material provided by the invention is relatively low in preparation process cost, relatively easy to implement and good in environmental protection property, required instruments are simple, convenient and safe to operate, and an effective method is provided for solving the problem of incompatibility of insulation and heat resistance of epoxy resin for winding insulation.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing high heat-resistant and high insulating composites, and particularly relates to a preparation method and application of a high heat-resistant and high insulating composite material. Background Art

[0002] The hot spot temperature of a transformer winding is an important factor for measuring the quality of the transformer winding design. If the transformer operates at a relatively high temperature for a long time, it will accelerate the thermal aging of the insulation system. The operating temperature threshold of the transformer mainly depends on the heat resistance grade of the insulation material of the transformer. Therefore, the selection and optimization research of the insulation material of dry-type transformers are of great significance to the safe and stable performance of dry-type transformers. The insulation material and the insulation structure composed of it are the basic guarantee for the stable operation of dry-type transformers. The heat resistance of the insulation of dry-type transformers determines their operating life and also limits the improvement of their voltage level and capacity. According to relevant standards, the safe operating temperature of commonly used F-grade epoxy resin is 155°C, and the expensive H-grade epoxy resin has a safe operating temperature of only 180°C. Traditional epoxy resins have poor heat resistance. When the temperature is too high, it is easy to cause the insulation aging of epoxy resins, and the mechanical properties decrease sharply, resulting in their inapplicability to work at high temperatures.

[0003] In view of this phenomenon, it is necessary to develop an epoxy resin composite material with both high heat resistance and excellent insulation performance. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems of low heat resistance, poor insulation performance of existing epoxy resin composites, complexity of the composite material preparation process, and environmental pollution, and to provide a preparation method of a high heat-resistant and high insulating composite material.

[0005] The present invention prepares a high heat-resistant and high insulating composite material through the molecular structure design of the curing agent and the content regulation of different functional curing agents.

[0006] A preparation method of a high heat-resistant and high insulating composite material is specifically completed according to the following steps:

[0007] I. Weighing materials:

[0008] Weigh epoxy resin and a curing agent;

[0009] The curing agent described in step I is 4,4'-diaminodiphenyl sulfone and 2,2'-bis(trifluoromethyl)diaminobiphenyl;

[0010] II. Add the curing agent weighed in step I to the epoxy resin, then put it into a vacuum stirring oven and stir for a certain time at a certain temperature;

[0011] III. Use a flat vulcanizing machine or an oven at a certain temperature to cure the epoxy resin to obtain a high heat-resistant and high insulating composite material.

[0012] A high heat-resistant and high-insulating composite material is used as a heat-resistant and insulating material for power electronic device packaging.

[0013] The present invention has the following beneficial effects:

[0014] (1) The present invention uses epoxy resin as the matrix, and its filling items mainly use a high heat-resistant curing agent 4,4'-diaminodiphenyl sulfone (DDS) containing a sulfone group, and 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) with excellent dielectric properties containing a trifluoromethyl group. By comparing several composite materials obtained according to the above test scheme, it is found that when the doping ratio of TFDB to DDS is 1:1, the glass transition temperature of the epoxy resin composite material prepared by the above method is 265 °C, which is 12 °C higher than that of the composite material prepared by epoxy resin and pure TFDB (253 °C); at the same time, this material also has a relatively low dielectric constant, which remains between 3.0 - 3.4 in the range of 10 0 -10 6 Hz, slightly lower than that of the composite material prepared by epoxy resin and pure DDS (3.5 - 3.8). And it has a relatively high AC breakdown field strength. The breakdown field strength of this material is 129.8 kV / mm, which is 17.5 kV / mm higher than that of the composite material prepared by epoxy resin and pure DDS (112.3 kV / mm);

[0015] (2) The preparation method of the high heat-resistant and high-insulating epoxy resin composite material provided by the present invention has a relatively low cost, is easy to implement, has good environmental protection, and the operation of the required instruments is simple and safe, providing an effective solution to the problem of incompatibility between the insulation and heat resistance of epoxy resin for winding insulation. Description of the Drawings

[0016] Figure 1 DSC test results of TFDB and epoxy resin AG80 at different heating rates before curing;

[0017] Figure 2 Optimal curing temperature obtained by DSC non-isothermal curing kinetics extrapolation method for TFDB and epoxy resin AG80;

[0018] Figure 3 For DDS and epoxy resin AG80 at different heating rates before curing;

[0019] Figure 4 Optimal curing temperature obtained by DSC non-isothermal curing kinetics extrapolation method according to DDS and epoxy resin AG80;

[0020] Figure 5Thermogravimetric curve comparison chart of high heat-resistant and high-insulating epoxy resin composites prepared for different embodiments;

[0021] Figure 6 Thermal decomposition rate comparison chart of high heat-resistant and high-insulating epoxy resin composites prepared for different embodiments;

[0022] Figure 7 Variation curve of relative dielectric constant with frequency of high heat-resistant and high-insulating epoxy resin composites prepared for different embodiments;

[0023] Figure 8 Variation curve of dielectric loss with frequency of high heat-resistant and high-insulating epoxy resin composites prepared for different embodiments;

[0024] Figure 9 DMA curve of glass transition temperature of high heat-resistant and high-insulating epoxy resin composites prepared for different embodiments;

[0025] Figure 10 AC breakdown field strength comparison chart of high heat-resistant and high-insulating epoxy resin composites prepared for different embodiments at power frequency. Detailed implementation manners

[0026] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art unless otherwise specified, and those skilled in the art can obtain them through commercial channels.

[0028] Detailed implementation manner one: A preparation method of a high heat-resistant and high-insulating composite material in this implementation manner is specifically completed according to the following steps:

[0029] 1. Weighing materials:

[0030] Weigh epoxy resin and curing agent;

[0031] The curing agent described in step 1 is 4,4'-diaminodiphenyl sulfone and 2,2'-bis(trifluoromethyl)diaminobiphenyl;

[0032] 2. Add the curing agent weighed in step 1 to the epoxy resin, then put it into a vacuum stirring oven and stir for a certain time at a certain temperature;

[0033] III. Use a flat vulcanizing machine or oven at a certain temperature to cure the epoxy resin, obtaining a high heat-resistant and high-insulation composite material.

[0034] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the epoxy resin described in Step 1 is AG80. Other steps are the same as those in Specific Embodiment 1.

[0035] Specific Embodiment 3: The difference between this embodiment and either Specific Embodiment 1 or 2 is that the mass ratio of 4,4'-diaminodiphenyl sulfone and 2,2'-bis(trifluoromethyl)benzidine in Step 1 is (1 - 9):(9 - 1). Other steps are the same as those in Specific Embodiment 1 or 2.

[0036] Specific Embodiment 4: The difference between this embodiment and any one of Specific Embodiments 1 to 3 is that the mass ratio of 4,4'-diaminodiphenyl sulfone and 2,2'-bis(trifluoromethyl)benzidine in Step 1 is 5:5. Other steps are the same as those in Specific Embodiments 1 to 3.

[0037] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that the mass ratio of the epoxy resin to the curing agent in Step 1 is 100:(53 - 67). Other steps are the same as those in Specific Embodiments 1 to 4.

[0038] Specific Embodiment 6: The difference between this embodiment and any one of Specific Embodiments 1 to 5 is that the temperature of the vacuum stirring oven in Step 2 is 50°C - 60°C. Other steps are the same as those in Specific Embodiments 1 to 5.

[0039] Specific Embodiment 7: The difference between this embodiment and any one of Specific Embodiments 1 to 6 is that the stirring time in Step 2 is 1h - 2h. Other steps are the same as those in Specific Embodiments 1 to 6.

[0040] Specific Embodiment 8: The difference between this embodiment and any one of Specific Embodiments 1 to 7 is that the curing process in Step 3 is as follows: First, maintain at 130°C - 140°C for 1h - 1.5h, then maintain at 200°C - 210°C for 1h - 1.5h, and finally maintain at 260°C - 265°C for 1h - 1.5h. Other steps are the same as those in Specific Embodiments 1 to 7.

[0041] Specific Embodiment 9: The difference between this embodiment and any one of Specific Embodiments 1 to 8 is that the thickness of the high heat-resistant and high-insulation composite material for winding encapsulation in Step 3 is 70μm - 80μm. Other steps are the same as those in Specific Embodiments 1 to 8.

[0042] Specific Embodiment 10: This embodiment is a high heat-resistant and high-insulation composite material used as a heat-resistant and insulating material for power electronic device encapsulation.

[0043] The beneficial effects of the present invention are verified by the following examples:

[0044] Example 1: A method for preparing a high heat-resistant and high-insulating composite material (T:D 5:5) is specifically completed according to the following steps:

[0045] I. Weighing materials:

[0046] Weigh epoxy resin and curing agent;

[0047] The epoxy resin described in step I is AG80;

[0048] The curing agent described in step I is 4,4'-diaminodiphenyl sulfone (DDS) and 2,2'-bis(trifluoromethyl)benzidine (TFDB);

[0049] The mass ratio of 2,2'-bis(trifluoromethyl)benzidine (TFDB) to 4,4'-diaminodiphenyl sulfone (DDS) described in step I is 5:5;

[0050] The mass ratio of the epoxy resin to the curing agent described in step I is 100:60;

[0051] II. Add the curing agent weighed in step I to the epoxy resin, then put it into a vacuum stirring oven and stir at 60°C for 1 h;

[0052] III. Use a flat vulcanizing machine or oven at a certain temperature to cure the epoxy resin to obtain a high heat-resistant and high-insulating composite material, denoted as T:D 5:5;

[0053] The curing process described in step III is as follows: First, maintain at 140°C for 1 h, then maintain at 200°C for 1 h, and finally maintain at 260°C for 1 h;

[0054] The thickness of the high heat-resistant and high-insulating composite material for winding encapsulation described in step III is 75 μm.

[0055] Example 2: The difference between this example and Example 1 is that: the mass ratio of 2,2'-bis(trifluoromethyl)benzidine (TFDB) to 4,4'-diaminodiphenyl sulfone (DDS) described in step I is 3:7; a high heat-resistant and high-insulating composite material is obtained in step III, denoted as T:D 3:7. Other steps and parameters are the same as those in Example 1.

[0056] Example 3: The difference between this example and Example 1 is that: the mass ratio of 2,2'-bis(trifluoromethyl)benzidine (TFDB) to 4,4'-diaminodiphenyl sulfone (DDS) described in step I is 7:3; a high heat-resistant and high-insulating composite material is obtained in step III, denoted as T:D 7:3. Other steps and parameters are the same as those in Example 1.

[0057] Comparative Example 1: The difference between this example and Example 1 is that: in Step 1, the mass ratio of 2,2'-bis(trifluoromethyl)benzidine (TFDB) and 4,4'-diaminodiphenylsulfone (DDS) is 1:0, that is, the curing agent is only 2,2'-bis(trifluoromethyl)benzidine (TFDB); in Step 3, a high heat-resistant and high-insulating composite material is obtained, denoted as TFDB. Other steps and parameters are the same as those in Example 1.

[0058] Comparative Example 2: The difference between this example and Example 1 is that: in Step 1, the mass ratio of 2,2'-bis(trifluoromethyl)benzidine (TFDB) and 4,4'-diaminodiphenylsulfone (DDS) is 0:1, that is, the curing agent is only 4,4'-diaminodiphenylsulfone (DDS); in Step 3, a high heat-resistant and high-insulating composite material is obtained, denoted as DDS. Other steps and parameters are the same as those in Example 1.

[0059] (1) DSC non-isothermal curing kinetics tests were carried out on the epoxy resin composite material prepared from TFDB and epoxy resin AG80, and the results are as Figure 1 shown. It can be seen that the DSC curves with different heating rates show a curing exothermic peak, which means only one curing exothermic peak. Curing reactions occur in the system, and no other reactions occur. As the heating rate increases, the initial temperature (T i ), peak temperature (T p ), and termination temperature (T f ) of the curing reaction shift to higher temperatures, a reaction heat lag phenomenon appears in the system, and the exothermic rate and exothermic amount of the curing reaction increase. Therefore, gradient heating is usually adopted in the actual curing reaction process.

[0060] (2) Analyzing the DSC non-isothermal curing kinetics test of the epoxy resin composite material prepared from TFDB and epoxy resin AG80, it can be obtained that Figure 2 , through the extrapolation method, the relationships between T i , T p , and T f values and the heating rate are all linearly fitted. The intercept of the T-β fitting line with the Y-axis corresponds to a heating rate of 0 and can be used as the curing temperature for gradient heating. Figure 2 The results of the linear fitting of temperature and heating rate are shown. The theoretical initial curing temperature, that is, the pretreatment temperature is 140 °C, the theoretical peak curing temperature is 200 °C, and the theoretical curing termination temperature is 260 °C, that is, the post-treatment temperature is 260 °C. According to the above results, the curing temperatures in the present invention are determined to be 140 °C / 1 h, 200 °C / 1 h, and 260 °C / 1 h.

[0061] (3) The DSC non-isothermal curing kinetics test was carried out on the epoxy resin composite prepared from DDS and epoxy resin AG80, and the results are as Figure 3 shown. It can be seen that the DSC curves with different heating rates show a curing exothermic peak, which means only one curing exothermic peak. The curing reaction occurs in the system, and no other reactions occur. As the heating rate increases, the initial temperature (T i ), peak temperature (T p ), and termination temperature (T f ) of the curing reaction shift to higher temperatures, a reaction heat lag phenomenon appears in the system, and the exothermic rate and exothermic amount of the curing reaction increase. Therefore, gradient heating is usually adopted in the actual curing reaction process.

[0062] (4) Analyzing the DSC non-isothermal curing kinetics test of the epoxy resin composite prepared from DDS and epoxy resin AG80, we can obtain Figure 4 , and by the extrapolation method, the relationships between the values of T i , T p , and T f and the heating rate are all linearly fitted. The intercept of the T-β fitting line with the Y-axis corresponds to a heating rate of 0, which can be used as the curing temperature for gradient heating. Figure 4 The results of the linear fitting of temperature and heating rate are shown. The theoretical initial curing temperature, that is, the pretreatment temperature is 130 °C, the theoretical peak curing temperature is 200 °C, and the theoretical curing termination temperature, that is, the post-treatment temperature is 260 °C. According to the above results and combined with the results in (2), since the pretreatment temperatures of the two curing agents are not much different, in order to avoid the problem of different curing temperatures for the subsequent doped curing agents, the curing temperatures in the present invention are determined to be 140 °C / 1 h, 200 °C / 1 h, and 260 °C / 1 h.

[0063] (5) The thermogravimetric test was carried out on the epoxy resin composites obtained from different examples, and the results are as Figure 5 shown. It can be seen that the thermal decomposition temperature when the epoxy resin composite loses 5% of its mass increases with the doping ratio of the DDS curing agent. Among them, the thermal decomposition temperature of the composite formed by curing epoxy resin when the ratio of DDS to TFDB is 5:5 and loses 5% is 352.3 °C, and the thermal decomposition temperature of the composite formed by curing TFDB and epoxy resin when it loses 5% is the lowest at 331.2 °C. Combining the theory, the reason can be analyzed. The sulfone-based linkage in DDS will decompose when heated to form sulfate compounds, and these sulfate compounds can significantly delay thermal decomposition. When the sulfate (or sulfonate) compounds are formed, the sulfone groups in the epoxy resin provide a "shielding effect". Therefore, the sulfate (or sulfonate) compounds in the epoxy resin composite doped with DDS delay the decomposition of the epoxy compound.

[0064] (6) The epoxy resin composites obtained from different embodiments were tested for thermal decomposition rate, and the results are as Figure 6 shown. It can be seen that the thermal decomposition rates of all epoxy resin composites first increase and then decrease with the increase of temperature. Among them, the maximum thermal decomposition rate of the composite obtained by curing DDS and epoxy resin can reach 1.275% mass loss per degree Celsius of the material at 388 °C, and the epoxy resin composite with the highest temperature required to reach the maximum decomposition rate is the epoxy resin composite obtained when the blending ratio of DDS and TFDB is 5:5, and its maximum decomposition rate is 1.22% mass loss per degree Celsius, and the corresponding decomposition temperature is 396 °C.

[0065] (7) The epoxy resin composites obtained from different embodiments were tested by DMA, and the results are as Figure 7 shown. The glass transition temperature of the epoxy resin composite can be obtained from the temperature peak of the temperature curve in Figure 7 . It can be seen from Figure 7 that with the increase of the content of the curing agent DDS, the glass transition temperature of the composite gradually increases. Among them, the glass transition temperature of the composite formed by curing DDS and TFDB with a ratio of 5:5 with epoxy resin is 265.4 °C, while the glass transition temperature of the composite formed by curing TFDB and epoxy resin is 253 °C.

[0066] (8) The AC breakdown field strength of the epoxy resin composites obtained from different embodiments was tested, and the changes in the breakdown strengths of different components are as Figure 8 shown. It can be seen that the breakdown field strength increases with the increase of the TFDB curing agent. Among them, the breakdown field strength of the composite formed by curing DDS and TFDB with a ratio of 5:5 with epoxy resin can reach 129.8 kV / mm at power frequency, while the breakdown field strength of the composite formed by curing DDS and epoxy resin is only 112.3 kV / mm at the lowest at power frequency. Compared with the epoxy resin composite formed by curing with DDS, the AC breakdown field strength of the epoxy resin composite cured by TFDB is increased by 15%.

[0067] (9) The dielectric properties of the epoxy resin composites obtained from different embodiments were characterized, and the change of the relative dielectric constant with frequency is as Figure 9 shown. It can be seen that the dielectric constant of the composite decreases slightly with the increase of frequency, and the dielectric constant of the material gradually decreases with the increase of the TFDB curing agent. The dielectric constant of the composite formed by curing DDS and TFDB with a ratio of 5:5 with epoxy resin remains between 3.0 - 3.4 in the range of 10 0 -10 6 Hz. The change of the dielectric loss with frequency is as Figure 10As shown, it can be seen that the dielectric loss first decreases and then increases with the increase of frequency, and gradually increases with the increase of the content of TFDB curing agent. When the ratio of DDS to TFDB is 5:5, the dielectric loss of the composite material formed by curing with epoxy resin is maintained at 0.007 - 0.015 within the range of 10 0 -10 6 Hz.

[0068] The above are only the preferred embodiments of the present invention. In view of the fact that those skilled in the art to which the present invention pertains can make appropriate changes and modifications to the above-mentioned embodiments, therefore, the present invention is not limited to the specific embodiments described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a high heat-resistant and high insulation composite material, characterized in that The preparation method is specifically completed according to the following steps:

1. Weighing materials: Weigh epoxy resin and curing agent; The curing agent described in step 1 is 4,4'-diaminodiphenyl sulfone and 2,2'-bis(trifluoromethyl)diaminobiphenyl; 2. Add the curing agent weighed in step 1 to the epoxy resin, then put it into a vacuum stirring oven, and stir it at a certain temperature for a certain time; 3. Use a flat vulcanizer or oven at a certain temperature to cure the epoxy resin to obtain a highly heat-resistant and highly insulating composite material.

2. The method for preparing a high heat-resistant and high insulation composite material according to claim 1, characterized in that The epoxy resin described in step 1 is AG80.

3. The method for preparing a high heat-resistant and high insulation composite material according to claim 1, characterized in that The mass ratio of 4,4'-diaminodiphenyl sulfone and 2,2'-bis(trifluoromethyl)diaminobiphenyl described in step 1 is (1-9):(9-1).

4. The method for preparing a high heat-resistant and high insulation composite material according to claim 3, characterized in that The mass ratio of 4,4'-diaminodiphenyl sulfone and 2,2'-bis(trifluoromethyl)diaminobiphenyl described in step 1 is 5:

5.

5. The method for preparing a high heat-resistant and high insulation composite material according to claim 1, characterized in that The mass ratio of the epoxy resin to the curing agent described in step 1 is 100:(53-67).

6. The method for preparing a high heat-resistant and high insulation composite material according to claim 1, characterized in that The temperature of the vacuum stirring oven described in step 2 is 50°C to 60°C.

7. The method for preparing a high heat-resistant and high insulation composite material according to claim 1, characterized in that The stirring time in step 2 is 1 h to 2 h.

8. The method for preparing a high heat-resistant and high insulation composite material according to claim 1, characterized in that The curing process described in step three is: first keep at 130°C to 140°C for 1h to 1.5h, then keep at 200°C to 210°C for 1h to 1.5h, and finally keep at 260°C to 265°C for 1h to 1.5h.

9. The method for preparing a high heat-resistant and high insulation composite material according to claim 1, characterized in that The thickness of the high heat-resistant and high insulation composite material for winding encapsulation described in step three is 70 μm to 80 μm.

10. Application of a high heat-resistant and high insulation composite material prepared by the preparation method according to claim 1, characterized in that A high heat-resistant and high-insulation composite material is used as a heat-resistant insulating material for packaging power electronic devices.

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