Modifier, preparation method thereof and application of modifier in release of curing stress of epoxy composite material

Abstract

The invention discloses a modifier and a preparation method and application thereof in releasing curing stress of an epoxy composite material, the modifier comprises a modified curing agent and a curing corrosion inhibitor, the modified curing agent comprises a ketone-based curing agent and a flexible compound, and the flexible compound is a long-chain compound with at least one hydroxyl group or amino group; the curing corrosion inhibitor is a boron trifluoride amine complex. The ketone-based curing agent is modified by a long-chain compound, so that the stress in the curing process of the epoxy resin can be dissipated by a long chain. And by adopting the curing slow-release agent, the reaction rate of the epoxy resin and the curing agent is slowed down, so that the epoxy resin and the curing agent can be cured in a more suitable configuration, and the stress accumulation in the epoxy composite material is greatly reduced. Therefore, the prepared epoxy composite material is small in internal stress and better in mechanical property, and can be effectively applied to pouring work of large equipment such as insulators, sleeves and transformers.

Description

Technical Field

[0001] The invention relates to a modifier and a preparation method thereof and application in releasing curing stress of epoxy composite materials, belonging to the technical field of composite materials. Background Art

[0002] Epoxy composites have been widely used in aerospace, automotive, construction, electronics and other fields due to their excellent mechanical properties, chemical corrosion resistance and good bonding properties. However, during the curing process of epoxy composites, significant curing stress will be generated due to the chemical reaction between epoxy resin and curing agent. This stress will not only cause microcracks inside the material, reducing the mechanical properties and durability of the material, but may also cause cracking and failure of the material during subsequent use.

[0003] In order to solve this problem, researchers have tried a variety of methods to release or reduce the curing stress of epoxy composites. Common methods include introducing flexible segments, using toughening agents, and using self-healing materials. In addition, the use of rubber toughening and organosilicon compound toughening can also improve the toughness of epoxy composites to a certain extent, but these methods often have some defects. For example, rubber toughening can lead to high viscosity and difficulty in dispersion of epoxy resin composites.

[0004] Although there are many methods for reducing the curing stress of epoxy composites, the existing technologies still have some shortcomings in practical applications. For example, some toughening agents have poor compatibility, high prices, and are easily decomposed at high temperatures, affecting the long-term stability of the material.

[0005] Therefore, developing a new type of modifier to effectively release the curing stress of epoxy composites while maintaining the excellent properties of the material has important research significance and application value. Summary of the invention

[0006] The purpose of the present invention is to provide a modifier and a preparation method thereof and use thereof in releasing the curing stress of epoxy composite materials. The provided modifier can effectively release the curing stress of epoxy composite materials.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A modifier comprises a modified curing agent and a curing corrosion inhibitor, wherein the modified curing agent comprises a ketone curing agent and a flexible compound, wherein the flexible compound is a long-chain compound having at least one hydroxyl group or amino group; and the curing corrosion inhibitor is a boron trifluoride amine complex.

[0009] Preferably, the mass ratio of the modified curing agent to the curing corrosion inhibitor is (10-12):(1-10);

[0010] The molar ratio of the ketone curing agent to the flexible compound is (0.43-0.47):(0.24-0.3).

[0011] Preferably, the ketone-based curing agent is one or more of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,4-diaminobenzophenone, 3,4-diamino-4-fluorobenzophenone and 4,4'-diaminobenzophenone.

[0012] Preferably, the flexible compound is one or more of linalool, tetrahydrolinalool, 10-undecenal, decanediamine and 1,12-diaminododecane.

[0013] Preferably, the boron trifluoride amine complex is one or more of a boron trifluoride monoethylamine complex, a boron trifluoride diethylamine complex and a boron trifluoride triethylamine complex.

[0014] The preparation method of any of the above-mentioned modifiers is to drop a solution containing a flexible compound into a solution containing a ketone-based curing agent to carry out a cross-linking reaction, and then dry to obtain a modified curing agent, and then place the modified curing agent and a curing corrosion inhibitor in a solvent, stir and dissolve, and then dry to obtain the modifier.

[0015] Preferably, the molar ratio of the ketone curing agent to the flexible compound is (0.43-0.47):(0.24-0.3); the conditions for the cross-linking reaction are: 200-250 r / min, 55-65° C., 1-3 h; the drying conditions are 100-120° C., 10-12 h;

[0016] The mass ratio of the modified curing agent to the curing corrosion inhibitor is (10-12):(1-10), the stirring and dissolving conditions are: 250-350r / min, 20-30min; the drying conditions are: 100-120℃, 10-12h.

[0017] The use of any of the above modifiers in releasing the curing stress of epoxy composite materials is to add any of the above modifiers when preparing the epoxy composite materials;

[0018] The epoxy composite material comprises the following components in parts by weight: 80-100 parts of epoxy resin, 100-130 parts of modifier, and 1-10 parts of accelerator, wherein the modifier comprises 100-120 parts of modified curing agent and 1-10 parts of curing sustained-release agent.

[0019] Preferably, the epoxy resin comprises at least one of bisphenol A diglycidyl ether and 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate; and the accelerator is N,N-dimethylbenzylamine and / or 2,4,6-tris(dimethylaminomethyl)phenol.

[0020] Preferably, the preparation method of the epoxy composite material is:

[0021] The epoxy resin and the modifier are mixed at 80-100° C. and a stirring rate of 300-400 r / min for 30-50 min to obtain an epoxy resin precast material;

[0022] Then add the accelerator to the epoxy resin precast material, and react in vacuum at 80-120°C and 300-400r / min for 30-50min;

[0023] Pour the reacted material into a mold, cure at 100-120°C for 4-6 hours, and then cure at 150-170°C for 12-16 hours;

[0024] Demoulding to obtain the epoxy composite material.

[0025] The beneficial effects of the present invention are:

[0026] The ketone curing agent is modified with a long-chain compound so that the stress in the epoxy resin curing process can be dissipated by the long chain. The curing slow-release agent is used to slow down the reaction rate of the epoxy resin and the curing agent, so that the epoxy resin and the curing agent can be cured in a more suitable configuration, greatly reducing the stress accumulation in the epoxy composite material. Therefore, the prepared epoxy composite material has less internal stress and better mechanical properties, and can be effectively applied to the casting of large equipment such as insulators, bushings and transformers.

[0027] The results show that the epoxy composite material prepared by adding modified curing agent has excellent heat resistance, bending strength and tensile strength, and its interfacial stress with metal is greatly reduced compared with conventional epoxy composites. DETAILED DESCRIPTION

[0028] The invention provides a modifier and a preparation method thereof. The obtained modifier is used for preparing epoxy resin materials to release curing stress of epoxy composite materials.

[0029] Among them, the modifier is obtained by mixing a modified curing agent and a curing slow-release agent; the modified curing agent is obtained by cross-linking a ketone curing agent and a flexible modifier; the flexible modifier is a long-chain compound with a single or multiple hydroxyl or amino groups, and the number of hydroxyl or amino groups is preferably 2 to 4.

[0030] The ketone-based curing agent includes one or more of 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 3,4-diaminobenzophenone, 3,4-diamino-4-fluorobenzophenone and 4,4'-diaminobenzophenone, and more preferably 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride. The ketone group in the ketone-based curing agent used reacts with the active group of the long-chain compound to adjust the flexibility of the modified curing agent. There is no special limitation on the source of the ketone-based curing agent, and conventional commercially available products can be used.

[0031] The flexible compound includes one or more of linalool, tetrahydrolinalool, 10-undecenal, decanediamine and 1,12-diaminododecane, and more preferably decanediamine and 1,12-diaminododecane. The flexible compound has a long chain structure and can effectively reduce the stress generated during the curing process of the epoxy composite material. There is no special limitation on the source of the flexible compound, and conventional commercially available products can be used.

[0032] The molar ratio of the ketone curing agent to the flexible compound is (0.43-0.47):(0.24-0.3). Controlling the molar ratio of the ketone curing agent to the flexible compound within the above range enables the ketone curing agent and the flexible compound to react fully.

[0033] The preparation method of the modified curing agent is to mix a ketone curing agent and a flexible compound solution, and perform a cross-linking reaction to obtain the modified curing agent, which specifically includes the following steps:

[0034] 1. Place the ketone-based curing agent and flexible compound in a drying oven and dry them at a temperature of 60 to 80°C for 5 to 6 hours;

[0035] 2. Dissolve the ketone-based curing agent and the flexible compound in N,N-dimethylformamide solution respectively and stir them thoroughly. The amount of solvent used for each 1g of ketone-based curing agent or flexible compound is 10-15ml. Dissolve them at room temperature. The stirring rate during dissolution is 250-350r / min and the stirring time is 20-30min.

[0036] 3. Add anhydrous magnesium sulfate desiccant to the ketone-based curing agent solution, place the mixture in a four-necked flask, heat and stir, and slowly add the flexible compound solution to the ketone-based curing agent solution by dropping. The dropping rate of the flexible compound solution is 8-10 ml / min. The heating temperature for dissolving the ketone-based curing agent is 60-65°C, the stirring rate is 200-250 r / min, and the reaction time is 1-3 hours;

[0037] 4. After the reaction is completed, the anhydrous magnesium sulfate is filtered by vacuum filtration to obtain a solution containing the modified curing agent after the reaction;

[0038] 5. Put the solution containing the modified curing agent into a drying oven for drying to finally obtain the modified curing agent. The drying temperature is 100-120°C and the drying time is 10-12 hours.

[0039] The preparation method of the modifier comprises the following steps:

[0040] 1. Place the modified curing agent and curing slow-release agent prepared above in a drying oven for drying at a temperature of 60 to 100°C for 4 to 5 hours;

[0041] 2. Dissolve the modified curing agent and the curing sustained-release agent in N,N-dimethylformamide solution in a mass ratio of (10-12):(1-10) and stir thoroughly. The amount of solution used for each 1g of the mixed reagent is 10-15ml. Dissolve at room temperature. The stirring rate during dissolution is 250-350r / min, and the stirring time is 20-30min.

[0042] 3. Put the solution containing the modifier into a drying oven for drying to finally obtain the modifier. The drying temperature is 100-120°C and the drying time is 10-12h.

[0043] The present invention also provides an epoxy composite material, whose raw materials include the following components: 80-100 parts of epoxy resin, 100-130 parts of modifier, and 1-10 parts of accelerator; wherein the epoxy resin includes one or more of bisphenol A diglycidyl ether and 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate; the modifier is the modifier prepared as described above; and the accelerator is one of N,N-dimethylbenzylamine and 2,4,6-tris(dimethylaminomethyl)phenol.

[0044] The preparation method of the epoxy composite material comprises the following steps:

[0045] 1. Place the epoxy resin, modifier and accelerator in a drying oven for drying at a temperature of 60 to 100°C for 4 to 5 hours;

[0046] 2. Heat and stir the epoxy resin and the modifier to obtain epoxy resin precast material. The heating temperature is 80-100°C, the stirring speed is 300-400r / min, and the stirring time is 30-50min;

[0047] 3. Add the accelerator to the epoxy resin precast material, and heat and stir in vacuum. The reaction environment is vacuum treated, the heating temperature is 80-120°C, the stirring rate is 300-400r / min, and the stirring time is 30-50min;

[0048] 4. Pour the epoxy resin precast material into the mold and cure it to obtain the epoxy resin composite sample. The curing is divided into pre-curing and post-curing. The pre-curing time is 4 to 6 hours and the curing temperature is 100 to 120°C; the post-curing time is 12 to 16 hours and the post-curing temperature is 150 to 170°C;

[0049] 5. After curing, demould to obtain the epoxy composite sample.

[0050] The present invention is further explained below in conjunction with embodiments and comparative examples.

[0051] Specifically, the purchasing sources of the reagents in the embodiments and comparative examples are shown in Table 1:

[0052] Table 1 Sources of reagents used in the preparation of epoxy composites

[0053] Reagent name Source of purchasing unit Bisphenol A diglycidyl ether Beijing Bailingwei Technology Co., Ltd. 3,3',4,4'-Benzophenonetetracarboxylic dianhydride Shanghai Huayuan Century Trading Co., Ltd. polysebacic anhydride Shanghai MacLean Biochemical Technology Co., Ltd. Decanediamine Shanghai MacLean Biochemical Technology Co., Ltd. Linalool Shanghai MacLean Biochemical Technology Co., Ltd. 1,2-phenylenediamine Shanghai MacLean Biochemical Technology Co., Ltd. Boron trifluoride monoethylamine complex Shanghai MacLean Biochemical Technology Co., Ltd. N,N-Dimethylbenzylamine Shanghai MacLean Biochemical Technology Co., Ltd.

[0054] Table 2 shows the material formulas of the epoxy composites prepared in Examples 1-4 and Comparative Examples 1-3, in which the components and amounts of the materials obtained in different Examples and Comparative Examples are clearly stated.

[0055] Table 2 Epoxy compound formula (by mass)

[0056]

[0057]

[0058] The preparation method of the epoxy composite material of the above embodiment and comparative example comprises the following steps:

[0059] 1. Place the ketone-based curing agent and flexible compound in a drying oven and dry them at a temperature of 80°C for 5 hours;

[0060] 2. Dissolve the ketone-based curing agent and the flexible compound in N,N-dimethylformamide solution respectively and stir them thoroughly. The amount of the dissolving solution is 15 ml for every 1 g of the ketone-based curing agent or the flexible compound. Dissolve them at room temperature. The stirring rate is 250 r / min and the stirring time is 30 min.

[0061] 3. Add anhydrous magnesium sulfate desiccant to the ketone-based curing agent solution, place the mixture in a four-necked flask, heat and stir, and slowly add the flexible compound solution to the ketone-based curing agent solution using a dropwise addition method. The dropwise addition rate of the flexible compound solution is 10 ml / min. The curing agent dissolving heating temperature is 65°C, the stirring rate is 250 r / min, and the reaction is carried out for 2 hours;

[0062] 4. After the reaction is completed, the anhydrous magnesium sulfate is filtered by vacuum filtration to obtain a solution containing the modified curing agent after the reaction;

[0063] 5. Put the solution containing the modified curing agent into a drying oven for drying to finally obtain the modified curing agent. The drying temperature is 120°C and the drying time is 12 hours;

[0064] 6. Dissolve the modified curing agent and curing slow-release agent (if not added) in N, N-dimethylformamide solution and stir thoroughly. The amount of solvent used for every 1g of reagent is 15ml. Dissolve at room temperature. The stirring rate during dissolution is 350r / min. The stirring time is 30min to obtain a solution containing the modifier.

[0065] 7. Put the solution containing the modifier into a drying oven for drying to finally obtain the modifier. The drying temperature is 100°C and the drying time is 12 hours;

[0066] 8. Place the epoxy resin, modifier and accelerator in a drying oven for drying at 80°C for 5 hours;

[0067] 9. Heat and stir the epoxy resin and the modifier to obtain epoxy resin precast material. The heating temperature is 80°C, the stirring speed is 350r / min, and the stirring time is 30min;

[0068] 10. Add the accelerator to the epoxy resin precast material, and heat and stir in vacuum. The reaction environment is vacuum treated, the heating temperature is 80°C, the stirring rate is 350r / min, and the stirring time is 30min;

[0069] 11. Pour the epoxy resin precast material into the specified mold and cure it to obtain the epoxy resin composite sample. The curing is divided into pre-curing and post-curing. The pre-curing time is 4 hours and the curing temperature is 100°C; the post-curing time is 12 hours and the post-curing temperature is 160°C;

[0070] 12. After curing, demould to obtain the epoxy composite sample.

[0071] The mechanical properties and thermal properties of the epoxy composite samples obtained in the above Examples 1-4 and Comparative Examples 1-3 were tested, and the standards for each test are as follows:

[0072] Bending strength: GB / T 2570-1995 Test method for bending properties of resin castings;

[0073] Tensile strength: GB / T 2571-1995 Impact test method for resin castings;

[0074] Glass transition temperature: GB / T 19466.2-2004 Plastics Differential Scanning Calorimetry (DSC) Part 2, Determination of glass transition temperature.

[0075] 1. Mechanical properties of epoxy composite samples obtained in Examples 1-4 and Comparative Examples 1-3 were tested, and their bending strength and impact strength were tested. The test results are shown in Table 3.

[0076] Table 3 Mechanical properties of epoxy composites

[0077] Bending strength(MPa) <![CDATA[Tensile strength (KJ / m 2 )]]> Example 1 64 121 Example 2 68 124 Example 3 69 122 Example 4 72 126 Comparative Example 1 40 118 Comparative Example 2 37 115 Comparative Example 3 28 121

[0078] It can be seen from the test results that the bending strength and tensile strength of Examples 1-4 are all good test results, while the test results of Comparative Examples 1-3 are all decreased to varying degrees. Compared with Example 1, Example 2 adds a curing slow-release agent, which further slows down the curing rate of the epoxy composite, releases the curing stress inside the epoxy composite, and increases its mechanical properties. Compared with Example 1, Comparative Example 1 does not adopt the toughening modification of the modified curing agent synthesized by the flexible compound, and directly uses a rigid curing agent to cure the epoxy resin, which makes the cured epoxy composite have a large internal curing stress, reducing its bending strength and impact strength. Comparative Example 2 uses 1,2-phenylenediamine with a rigid benzene ring in the molecular structure as a modifier to modify the curing agent, further enhancing the curing stress of the modified curing agent and the epoxy composite, thereby reducing its bending strength and impact strength. Comparative Example 3 only uses a long-chain flexible curing agent, polysebacic anhydride. Under the action of polysebacic anhydride, the toughness of the epoxy composite is further improved, but its too low rigidity cannot support the bending strength.

[0079] 2. The epoxy composite samples obtained in Examples 1-4 and Comparative Examples 1-3 were subjected to thermogravimetric analysis and differential scanning calorimetry analysis, and their thermal decomposition temperature (T5%), maximum temperature of thermal degradation rate (Tmax) and glass transition temperature (Tg) were tested. The test results are shown in Table 4.

[0080] Table 4 Heat resistance of epoxy composite materials

[0081] T5％(℃) Tmax(℃) Tg(℃) Example 1 367 437 151.42 Example 2 372 442 148.45 Example 3 371 440 149.75 Example 4 375 444 152.12 Comparative Example 1 361 429 143.78 Comparative Example 2 362 430 145.57 Comparative Example 3 328 410 117.85

[0082] It can be seen from the test results that the heat resistance of the epoxy composites in Examples 1-4 is reduced compared to that in Comparative Examples 1-3. This is because different modifiers are used in Examples 1-4, which slow down the curing rate of the epoxy composites, resulting in the epoxy resin being cross-linked with more curing agents, the degree of cross-linking is increased, and the heat resistance of the epoxy composite is increased. In Comparative Examples 1-2, rigid curing agents and rigid modifiers are used, so the heat resistance is not significantly reduced. Comparative Example 3 uses long-chain flexible polysebacic anhydride as a curing agent, which makes its molecular segments more easily displaced under high temperature, so the heat resistance of the epoxy composite in Comparative Example 3 is significantly reduced.

[0083] 3. The maximum curing stress of the epoxy composite samples obtained in Examples 1-4 and Comparative Examples 1-3 and the metal interface was tested, and the test results are shown in Table 4. The metal is a cylinder with a diameter of 10 cm, and the epoxy composite is cured around it to form a 10 cm thick cylinder.

[0084] Table 5 Maximum interface stress between epoxy composites and metals

[0085] Maximum interface stress (MPa) Example 1 22 Example 2 18 Example 3 17 Example 4 17 Comparative Example 1 29 Comparative Example 2 33 Comparative Example 3 25

[0086] The test results show that compared with the maximum curing stress of the epoxy composite and the metal interface in Examples 1-4, the curing stress obtained in the comparative examples 1-3 is significantly increased. This is because the curing rate is fast, and the cross-linking rate of the epoxy resin and the curing agent is too fast, resulting in a large amount of stress accumulation inside the epoxy composite, thereby generating a greater interface stress at the metal interface. Different modifiers are used in Examples 1-4 to slow down the curing rate of the epoxy composite, better disperse the stress on the interface, and thus reduce the maximum interface stress.

[0087] In summary, the modifier-cured epoxy composite provided in the present application can effectively disperse the curing stress formed during the curing process of the epoxy composite, thereby increasing the mechanical properties and heat resistance of the epoxy composite, and reducing the stress at the interface between the epoxy composite and the metal, providing reliable and effective support for the insulation packaging of large power equipment such as insulators, bushings and transformers.

[0088] The above is only a preferred implementation of the patent of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the patent of the present invention. These improvements and modifications should also be regarded as the scope of protection of the patent of the present invention.

Claims

1. A modifier, characterized in that: The invention comprises a modified curing agent and a curing corrosion inhibitor, wherein the modified curing agent comprises a ketone curing agent and a flexible compound, wherein the flexible compound is a long-chain compound having at least one hydroxyl group or amino group; and the curing corrosion inhibitor is a boron trifluoride amine complex.

2. The modifier according to claim 1, characterized in that The mass ratio of the modified curing agent to the curing corrosion inhibitor is (10-12):(1-10); The molar ratio of the ketone curing agent to the flexible compound is (0.43-0.47):(0.24-0.3).

3. The modifier according to claim 1, characterized in that The ketone-based curing agent is one or more of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,4-diaminobenzophenone, 3,4-diamino-4-fluorobenzophenone and 4,4'-diaminobenzophenone.

4. The modifier according to claim 1, characterized in that The flexible compound is linalool, tetrahydrolinalool, One or more of 10-undecenal, decanediamine and 1,12-diaminododecane.

5. The modifier according to claim 1, characterized in that The boron trifluoride amine complex is one or more of a boron trifluoride monoethylamine complex, a boron trifluoride diethylamine complex and a boron trifluoride triethylamine complex.

6. The method for preparing the modifying agent according to any one of claims 1 to 5, characterized in that: The method comprises dropping a solution containing a flexible compound into a solution containing a ketone-based curing agent to carry out a cross-linking reaction, and then drying to obtain a modified curing agent. The modified curing agent and a curing corrosion inhibitor are then placed in a solvent, stirred and dissolved, and then dried to obtain a modifier.

7. The method for preparing the modifying agent according to claim 6, characterized in that: The molar ratio of the ketone curing agent to the flexible compound is (0.43-0.47):(0.24-0.3); the conditions of the cross-linking reaction are: 200-250r / min, 55-65°C, 1-3h; Drying conditions are 100-120°C, 10-12h; The mass ratio of the modified curing agent to the curing corrosion inhibitor is (10-12):(1-10), the stirring and dissolving conditions are: 250-350r / min, 20-30min; the drying conditions are: 100-120℃, 10-12h.

8. Use of the modifier according to any one of claims 1 to 5 in releasing the curing stress of epoxy composite materials, characterized in that: The modifier described in any one of claims 1 to 5 is added during the preparation of the epoxy composite material; The epoxy composite material comprises the following components in parts by weight: 80-100 parts of epoxy resin, 100-130 parts of modifier, and 1-10 parts of accelerator, wherein the modifier comprises 100-120 parts of modified curing agent and 1-10 parts of curing sustained-release agent.

9. Use of the modified curing agent according to claim 8 in releasing curing stress of epoxy composite materials, characterized in that: The epoxy resin comprises at least one of bisphenol A diglycidyl ether and 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate; the accelerator is N,N-dimethylbenzylamine and / or 2,4,6-tris(dimethylaminomethyl)phenol.

10. Use of the modified curing agent according to claim 8 in releasing curing stress of epoxy composite materials, characterized in that: The preparation method of the epoxy composite material is: The epoxy resin and the modifier are mixed at 80-100° C. and a stirring rate of 300-400 r / min for 30-50 min to obtain an epoxy resin precast material; Then add the accelerator to the epoxy resin precast material, and react in vacuum at 80-120°C and 300-400r / min for 30-50min; Pour the reacted material into a mold, cure at 100-120°C for 4-6 hours, and then cure at 150-170°C for 12-16 hours; Demoulding to obtain the epoxy composite.

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