Recyclable and repairable epoxy resin based on DA bond and preparation method thereof
By introducing a monoepoxy diluent and furfuramine into the epoxy resin, it forms a linear resin and melts in vacuum after crushing with bismaleimide, the problem of difficult to repair and recycling of traditional thermosetting materials is solved, and multiple repairs have been achieved and the performance after recycling is stable, avoiding self-aggregation.
Patent Information
- Application Number
- CN202411417989.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-11
- Publication Date
- 2024-12-06
AI Technical Summary
Traditional thermosetting materials are difficult to repair and recycle, resulting in waste of resources and environmental pollution. Materials introduced in the prior art that have deteriorated their performance after multiple repairs, especially the self-polymerization of bismaleimide leads to a decrease in crosslink density. , loses repairable and recyclable capabilities.
By introducing a monoepoxy diluent and furfuryamine into the epoxy resin, a linear resin with a furyl group in the side chain is formed, and then pulverized with bismaleimide and melted in a vacuum state to avoid polar solvent intervention. Control the molecular chain length and crosslink density to ensure stable performance for multiple repairs and recovery.
A number of repairable and recyclable epoxy resins have been achieved, with repairs of more than 11 times. After recycling, the mechanical properties remain above 90%. The color of the resin has not changed, which avoids the self-polymerization of bismaleimide and maintains the Crosslinking density.
Smart Images
Figure CN119081068A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of organic materials, and in particular relates to a recyclable and repairable epoxy resin based on DA bonds and a preparation method thereof. Background Art
[0002] Traditional polymer materials are mainly divided into two categories: thermoplastics and thermosetting materials. Among them, thermoplastic materials can be processed and recycled by solution or melting methods because their molecules are mainly bonded by non-covalent bonds such as van der Waals forces and hydrogen bonds. However, they have poor chemical resistance and relatively low mechanical strength. Thermosetting materials have a cross-linked network structure formed by covalent bonds between their molecules, so they have higher physical and mechanical properties, chemical resistance, heat resistance, etc., but due to their cross-linked network structure, they are difficult to repair and recycle. Once they fail, they cannot be used again, which undoubtedly causes waste of resources and environmental pollution. How to repair and recycle thermosetting materials has become a research hotspot in the past decade.
[0003] At present, dynamic covalent bonds (such as ester bonds, disulfide bonds, etc.) are introduced into thermosetting materials. The characteristics of "breaking" and "reorganization" of dynamic covalent bonds under different external stimuli (such as light, heat, PH, etc.) are utilized to achieve the transformation of polymer thermoplasticity and thermosetting properties. The prepared polymer has a cross-linked network structure in the thermosetting state, with uniform structure and excellent mechanical properties. It can be repaired and reprocessed in the thermoplastic state, becoming a new type of polymer material that will replace traditional thermosetting resins in the future.
[0004] In recent years, people have prepared a series of new cross-linked epoxy resins with thermal repair and reprocessing capabilities by introducing Diels-Alder (DA) bonds into epoxy resin systems. The mode of constructing DA bonds by most researchers is to introduce furan groups as side groups into epoxy resin chains to form long-chain molecules with furan side groups (FA-EP), use bismaleimide (BMI) as a bridge for cross-linking structures, and use the carbon-carbon double bonds on BMI and furan groups to construct DA bonds. At the same time, in order to make BMI and EP mix evenly, polar substances such as DMF are often used as solvents. However, in this process, the resin often turns red after repair, the number of repairs is limited, and the performance decreases significantly after multiple repairs. These phenomena are mostly attributed to the self-polymerization of BMI. The self-polymerization of BMI will cause the cross-linking density of the cured product to decrease and the strength to decrease significantly after one or several repairs; high BMI cross-linking will even transform the system into a thermosetting bismaleimide resin, thereby losing its repairability and recyclability. Summary of the invention
[0005] In order to solve the above problems existing in the prior art, the present invention provides a recyclable and repairable epoxy resin based on DA bonds and a preparation method thereof. The technical problem to be solved by the present invention is achieved by the following technical solutions:
[0006] The embodiment of the present invention provides a method for preparing a recyclable and repairable epoxy resin based on DA bonds, comprising the steps of:
[0007] S1, heating the epoxy resin, furfurylamine and monoepoxy diluent under stirring and keeping the temperature to react, and then adding a preset volume of furfurylamine to the reaction product to allow the monoepoxy diluent to react completely, thereby obtaining a linear resin having a furan group in the side chain;
[0008] S2, mixing and crushing the linear resin and bismaleimide to obtain a mixed powder;
[0009] S3, melting the mixed powder under vacuum, so that the linear resin dissolves the bismaleimide to obtain a blend;
[0010] S4, crushing the blend and then melting it to discharge bubbles in the melt, and then heat-treating the melt so that the linear resin and the bismaleimide are cross-linked and cured to obtain an epoxy resin based on DA bonds.
[0011] In one embodiment of the present invention, step S1 comprises:
[0012] Weigh epoxy resin, furfurylamine and monoepoxy diluent in proportion, raise the temperature to 75-85° C. under stirring, keep the temperature for 25-35 minutes, then raise the temperature to 110-120° C., keep the temperature for 1-2 hours, and react the epoxy resin, furfurylamine and monoepoxy diluent to obtain a reaction product;
[0013] 1-3 ml of furfurylamine is added dropwise to the reaction product to allow the monoepoxy diluent to react completely. At the same time, the reaction system is heated to 145-155° C. and then reacted at a constant temperature for 25-35 minutes to volatilize excess furfurylamine, thereby obtaining the linear resin having a furan group on the side chain.
[0014] In one embodiment of the present invention, the epoxy resin includes one or more of E-51, E-44, and F-51;
[0015] The monoepoxy diluent includes one or more of phenyl glycidyl ether, alkylene glycidyl ether, and benzyl glycidyl ether;
[0016] The bismaleimide includes one or more of bismaleimide diphenylmethane and phenylene bismaleimide;
[0017] The linear resin has a rotational viscosity at 120° C. less than or equal to 4000 mPa·s.
[0018] In one embodiment of the present invention, step S2 comprises:
[0019] Calculate the mass of bismaleimide according to the molar number of furan groups in the linear resin and weigh it;
[0020] crushing the linear resin;
[0021] The crushed linear resin and the weighed bismaleimide are added to a grinder and crushed to obtain a mixed powder.
[0022] In one embodiment of the present invention, the molar ratio of the furan group in the linear resin to the bismaleimide is 2:1;
[0023] The average particle size of the mixed powder is ≤200 μm.
[0024] In one embodiment of the present invention, step S3 includes:
[0025] The mixed powder is spread flat in a container, placed in a vacuum box at 145-155° C. for preheating for 10-15 minutes, and then evacuated, and maintained at a first preset vacuum degree for a first preset time to obtain the blend.
[0026] In one embodiment of the present invention, the first preset vacuum degree is less than or equal to 0.02 MPa, and the first preset time is 10-15 min.
[0027] In one embodiment of the present invention, step S4 includes:
[0028] The blend is crushed and placed in a mold, and the mold is placed in a vacuum box that reaches the recovery temperature and kept warm for 25-35 minutes, then the vacuum box is evacuated and maintained at a second preset vacuum degree for a second preset time, and then the mold is transferred to an oven at 65-75°C for curing for 20-28 hours, and the DA bond-based epoxy resin is obtained after cooling.
[0029] In one embodiment of the present invention, the recovery temperature is 110°C-130°C;
[0030] The second preset vacuum degree is less than or equal to 0.01 MPa, and the second preset time is 10-20 minutes.
[0031] Another embodiment of the present invention provides a recyclable and repairable epoxy resin based on DA bonds, which is prepared by the preparation method described in the above embodiment.
[0032] Compared with the prior art, the present invention has the following beneficial effects:
[0033] 1. The preparation method of the present invention introduces a monoepoxy diluent when synthesizing a synthetic linear resin having a furan group in the side chain, thereby avoiding the promoting effect of the polarity induction of the epoxy group on the self-polymerization of the bismaleimide group, and effectively preventing the self-polymerization reaction of BMI. At the same time, the addition of the monoepoxy diluent can end the molecular chain and adjust the molecular chain length, thereby effectively controlling the viscosity of the reactants and improving their efficiency during repair and recovery; at the same time, a preset volume of furfurylamine is added dropwise at the end of the reaction, effectively allowing the residual epoxy groups in the system to participate in the reaction, thereby substantially preventing the promoting effect of the epoxy groups on the self-polymerization of the bismaleimide group;
[0034] 2. The preparation method of the present invention prepares a powder mixture of a linear resin and bismaleimide, thereby increasing the contact area between the two, and then melts the mixed powder under a vacuum state. Under the combined action of vacuum and temperature, a homogeneous blend of the linear resin and bismaleimide is prepared, thereby avoiding the intervention of a polar solvent, thereby avoiding the promotion of the polar solvent to the self-polymerization of the bismaleimide group;
[0035] 3. The epoxy resin prepared by the present invention is a multi-repairable and recyclable resin. The number of repairs can reach more than 11 times. After recycling 5 times, its mechanical properties can still be maintained at more than 90%. After repair and recycling, the color of the resin does not change significantly, indicating that in addition to participating in the DA bond reaction, bismaleimide does not self-polymerize, and the cross-linking density of the epoxy resin based on the DA bond is well maintained. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Figure 1 A schematic flow chart of a method for preparing a recyclable and repairable epoxy resin based on DA bonds provided in an embodiment of the present invention;
[0037] Figure 2 A schematic diagram of a process for preparing a recyclable and repairable epoxy resin based on DA bonds provided in an embodiment of the present invention;
[0038] Figure 3a-Figure 3b A color comparison chart of BMI and FA-EP mixed with or without solvent provided in an embodiment of the present invention;
[0039] Figure 4 Comparison pictures before and after repair of multiple repairability tests provided for Example 1;
[0040] Figure 5 A graph showing the relationship between the number of repairs and the repair time provided for Example 1;
[0041] Figure 6a-6b The macroscopic morphology of the resin before and after multiple recycling provided for Example 1;
[0042] Figure 7A graph of the flexural strength versus the number of repairs provided for Example 1. DETAILED DESCRIPTION
[0043] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.
[0044] Embodiment 1
[0045] Studies have shown that epoxy groups promote the self-polymerization of bismaleimide groups, which is attributed to the polar induction effect of epoxy groups. It is speculated that polar solvents and trace residual epoxy groups in FA-EP can also promote the self-polymerization of bismaleimide.
[0046] In order to solve the problem of bismaleimide self-polymerization in the DA-EP system, the present invention starts from the perspective of epoxy matrix formula design, and adds a monoepoxy diluent on the basis of preparing a linear epoxy resin containing a furan group in the side chain from epoxy resin and furfurylamine. The addition of the monoepoxy diluent can control the reaction chain length on the one hand, so that the resin can show good fluidity at the repair and recovery temperature, improve the repair efficiency, reduce the time of its treatment at high temperature, and limit the self-polymerization reaction of bismaleimide at high temperature; on the other hand, the linear epoxy can be capped to reduce the content of the epoxy end group, thereby reducing or even eliminating the catalytic polymerization of the epoxy group on the bismaleimide; then, by dripping furfurylamine, the epoxy group is completely reacted, and by increasing the temperature, the excess furfurylamine is volatilized. In addition, FA-EP and BMI are prepared into a powder blend with low particle size through a co-crushing process, which increases the contact area between the two, and then a FA-EP / BMI homogeneous blend is prepared under the action of vacuum and high temperature, avoiding the intervention of polar solvents.
[0047] See also Figure 1 , Figure 1 A schematic flow chart of a method for preparing a recyclable and repairable epoxy resin based on a DA bond provided in an embodiment of the present invention. The method for preparing a recyclable and repairable epoxy resin based on a DA bond comprises the following steps:
[0048] S1. The epoxy resin, furfurylamine and monoepoxy diluent are heated and kept warm under stirring to react, and then a preset volume of furfurylamine is added to the reaction product to allow the monoepoxy diluent to react completely, thereby obtaining a linear resin having a furan group in the side chain.
[0049] Specifically, first, epoxy resin, furfurylamine FA and monoepoxy diluent are weighed in proportion, placed in a beaker, slowly heated to 75-85°C under stirring, the heating time is 25-35min, and kept warm for 25-35min, then heated to 110-120°C, kept warm for 1-2h, to react epoxy resin, furfurylamine and monoepoxy diluent to obtain a reaction product. Then, a small amount (1-3ml) of furfurylamine is added dropwise to the reaction product to completely react the monoepoxy diluent, and the reaction system is heated to 145-155°C and then kept at a constant temperature for 25-35min to volatilize the excess furfurylamine, to obtain a linear resin with a furan group on the side chain. The linear resin is a light yellow transparent substance that is liquid at high temperature and solid at room temperature, and is recorded as FA-EP.
[0050] In a specific embodiment, the epoxy resin includes one or more of E-51, E-44, and F-51; the monoepoxy diluent includes one or more of phenyl glycidyl ether, alkylene glycidyl ether, and benzyl glycidyl ether; and the bismaleimide includes one or more of bismaleimide diphenylmethane and phenylene bismaleimide.
[0051] Furthermore, the FA-EP prepared by using different proportions of epoxy resin and monoepoxy diluent has different rotational viscosities, and the amount of furfurylamine added is added according to the number of epoxy groups. This embodiment requires that the rotational viscosity of the FA-EP prepared by the reaction is ≤4000mPa·s at 120°C, and the ratio of epoxy resin, furfurylamine and monoepoxy diluent meets the rotational viscosity requirement.
[0052] S2. Mix and crush the linear resin and bismaleimide to obtain a mixed powder.
[0053] Specifically, the linear resin FA-EP is crushed and then added to a grinder. The mass of the bismaleimide BMI is calculated and weighed according to the molar number of furan groups in the linear resin FA-EP. Finally, the weighed bismaleimide BMI is added to a grinder and mixed with the linear resin FA-EP, and the grinder is turned on for crushing. Exemplarily, the crushing time is 30s to 60s to obtain a mixed powder of the linear resin FA-EP and the bismaleimide BMI.
[0054] Specifically, the molar ratio of furan group to bismaleimide BMI in the linear resin FA-EP is 2:1.
[0055] Specifically, the linear resin FA-EP and bismaleimide BMI are required to have uniform color and an average particle size of ≤200 μm after being crushed. The lower the particle size, the shorter the blending time in the subsequent step S3 and the better the blending effect.
[0056] S3. Melting the mixed powder under vacuum to make the linear resin dissolve the bismaleimide to obtain a blend.
[0057] Specifically, the prepared FA-EP and BMI mixed powders are spread in a container, placed in a vacuum box at 145-155°C for preheating for 10-15 minutes, and then evacuated, and maintained at a first preset vacuum degree for a first preset time to obtain a FA-EP and BMI blend, which is a light yellow transparent solid. The first preset vacuum degree is less than or equal to 0.02Mpa, and the first preset time is 10-15 minutes. The lower the first preset vacuum degree, the better the blending effect.
[0058] S4, crushing the blend and then melting it to expel bubbles in the melt, and then heat-treating the melt so that the linear resin and bismaleimide are cross-linked and cured to obtain an epoxy resin based on DA bonds.
[0059] Specifically, the prepared FA-EP and BMI blend is crushed and placed in a mold, and the mold is placed in a vacuum box that reaches the recovery temperature and kept warm for 25-35 minutes, then the vacuum box is evacuated, and maintained at a second preset vacuum degree for a second preset time to discharge bubbles in the melt, and then the mold is transferred to an oven at 65-75°C for curing for 20-28 hours, and after cooling, an epoxy resin based on DA bonds is obtained, which is recorded as DA-EP.
[0060] Specifically, the recovery temperature is 110°C-150°C. The higher the temperature, the faster the repair speed. However, the temperature should not exceed 150°C, otherwise BMI copolymerization will occur, causing the resin to turn red, performance degradation, and reduced repair and recovery capabilities. Preferably, the recovery temperature is 110°C-130°C. Within this range, BMI is not prone to copolymerization, and the repair and recovery performance is good.
[0061] Specifically, the second preset vacuum degree is less than or equal to 0.01 Mpa, and the second preset time is 10-20 min. The lower the second preset vacuum degree, the fewer residual bubbles, and the better the uniformity of the prepared sample.
[0062] The preparation method of this embodiment introduces a monoepoxy diluent when synthesizing a synthetic linear resin having a furan group in the side chain, thereby avoiding the polarity-induced promotion of the epoxy group on the self-polymerization of the bismaleimide group, and effectively preventing the self-polymerization reaction of BMI. At the same time, the addition of the monoepoxy diluent can end the molecular chain and adjust the molecular chain length, thereby effectively controlling the viscosity of the reactants and improving their efficiency during repair and recovery; at the same time, a preset volume of furfurylamine is added dropwise at the end of the reaction, so that the residual epoxy groups in the system are effectively involved in the reaction, thereby basically preventing the promotion of the epoxy groups on the self-polymerization of the bismaleimide group.
[0063] The preparation method of this embodiment prepares a powder mixture of linear resin and bismaleimide, increases the contact area between the two, and then melts the mixed powder under vacuum. Under the combined action of vacuum and temperature, a homogeneous blend of linear resin and bismaleimide is prepared, avoiding the intervention of polar solvents, thereby avoiding the promotion of polar solvents on the self-polymerization of bismaleimide.
[0064] The preparation process of this embodiment is simple and easy to promote.
[0065] Embodiment 2
[0066] Based on Example 1, see Figure 2 , Figure 2 A process diagram of a method for preparing a recyclable and repairable epoxy resin based on DA bonds provided by an embodiment of the present invention. This embodiment further illustrates the method for preparing a recyclable and repairable epoxy resin based on DA bonds through the following examples.
[0067] Example 1
[0068] A method for preparing a recyclable and repairable epoxy resin based on DA bonds, comprising the steps of:
[0069] S1. The epoxy resin, furfurylamine and monoepoxy diluent are heated and kept warm under stirring to react, and then a preset volume of furfurylamine is added to the reaction product to allow the monoepoxy diluent to react completely, thereby obtaining a linear resin having a furan group in the side chain.
[0070] Specifically, epoxy resin, furfurylamine (FA), and monoepoxy diluent are weighed in proportion and placed in a beaker, and the temperature is slowly raised to 80°C within 30 minutes under stirring, and kept warm for 30 minutes, and then raised to 110°C, and kept warm for 1.5 hours, and then a small amount of FA (4 to 6 drops, the volume is 1-3ml, not included in the total amount of FA) is added dropwise, and the temperature is raised to 150°C and kept at a constant temperature for 30 minutes to obtain a light yellow transparent substance that is liquid at high temperature and solid at room temperature, that is, a linear resin FA-EP with a furan group on the side chain. Among them, the epoxy resin is E-51, the content is 50.6wt%; the monoepoxy diluent is glycidyl phenyl ether GPE, the content is 21.7wt%; the FA content is 20.2wt%; the rotational viscosity of the prepared FA-EP at 120°C is 2849mPa·s.
[0071] The chemical formula for the complete chemical reaction of the above epoxy resin, furfurylamine and monoepoxy diluent is:
[0072]
[0073] S2. Mix and crush the linear resin and bismaleimide to obtain a mixed powder.
[0074] Specifically, FA-EP is broken into pieces, FA-EP and BMI are weighed in proportion, and put into a grinder, which is turned on and ground for 30 seconds to obtain a mixed powder. The FA-EP content is 71wt%; BMI is bismaleimide diphenylmethane, and the content is 29wt%; the average particle size of the prepared mixed powder is 157μm.
[0075] S3. Melting the mixed powder under vacuum to make the linear resin dissolve the bismaleimide to obtain a blend.
[0076] Specifically, the prepared mixed powder is evenly spread in a container with release paper, placed in a 150°C vacuum box for treatment for 10-15 minutes, then evacuated, maintained in a vacuum state of 0.01 MPa for 10-15 minutes, the vacuum box is closed, taken out and cooled to obtain a homogeneous blend of FA-EP and BMI, which is a light yellow transparent solid.
[0077] See also Figure 3a-Figure 3b , Figure 3a-Figure 3b The color comparison diagram of BMI and FA-EP mixed with or without solvent provided in the embodiment of the present invention is as follows: Figure 3a The homogeneous blend of FA-EP and BMI prepared in the embodiment of the present invention without the participation of solvent is a light yellow transparent solid. Figure 3b This is a mixed solution of FA-EP and BMI in the presence of DMF in the prior art. The color of the mixed solution is reddish, indicating that BMI has copolymerized. Figure 3a and Figure 3b It can be seen that the method of this embodiment can effectively avoid BMI copolymerization.
[0078] S4, crushing the blend and then melting it to expel bubbles in the melt, and then heat-treating the melt so that the linear resin and bismaleimide are cross-linked and cured to obtain an epoxy resin based on DA bonds.
[0079] Specifically, the prepared FA-EP and BMI homogeneous blend is broken into pieces and put into a mold, filling the mold as much as possible, and the mold is placed after the temperature of the vacuum box reaches the recovery temperature of 130°C and kept warm for 30 minutes. Subsequently, the vacuum box is evacuated and maintained at a vacuum state of 0.005 MPa for 15 minutes. Subsequently, the mold is transferred to a 70°C oven for treatment for 24 hours. After cooling to room temperature with the furnace, the sample is taken out, which is the multiply repairable and recyclable epoxy resin DA-EP based on DA reaction.
[0080] Specifically, the reaction formula for cross-linking and curing of the linear resin and bismaleimide is:
[0081]
[0082] The repair test process of the epoxy resin DA-EP prepared above is as follows: take a small amount of DA-EP sample and place it on a PTFE plate, treat it at 120℃ for 15 minutes, and then treat it in a 70℃ oven for 24 hours, take it out and cool it to room temperature, then use a blade to scratch a scratch on its surface, then place it in a 120℃ oven and time it, visually observe the scratch repair every 3 minutes, take the time when the scratch is completely repaired as the repair time, treat the repaired sample in a 70℃ oven for 24 hours, use a blade to scratch a scratch again, then place it in a 120℃ oven and time it, record the repair time, and repeat this process. See the repair status for details. Figure 4 , Figure 4 The comparison chart before and after repair for multiple repairable tests provided for Example 1. The relationship between repair time and number of repairs is shown in Figure 5 , Figure 5 The relationship between the number of repairs and the repair time provided for Example 1. Figure 4 and Figure 5 As shown in the figure, during the process of up to 11 repairs, the repair time was basically maintained at about 14 minutes, and the resin color basically did not change after multiple repairs.
[0083] The repairability test process for the epoxy resin DA-EP prepared above is as follows: pour the homogeneous mixture in step S3 into a mold preheated to 120°C while hot, and place the excess mixed liquid in an enamel tray covered with release paper, and place the mold and the enamel tray in a 120°C vacuum box for 15 minutes, and finally place them in a 70°C oven for 24 hours, and then take them out for testing after cooling to room temperature with the furnace. This sample is the initial sample (i.e., the DA-EP obtained in step S4), and the sample is recovered after the test; embed the recovered sample into the preheated mold, and add part of the sample in the enamel tray to make up for the test loss, and place the mold and the enamel tray in a 120°C vacuum box for 15 minutes, and then place them in a 70°C oven for 24 hours, and then take them out for testing after cooling to room temperature with the furnace. This sample is a one-time recovered sample, and the sample is recovered after the test, and so on. The macroscopic morphology of the resin after multiple recovery can be seen in Figure 6a-6b , Figure 6a-6b The macroscopic morphology of the resin before and after multiple recycling provided for Example 1, Figure 6a Before recycling, Figure 6b After recycling, the relationship between recycling times and bending strength is shown in Figure 7 , Figure 7 The bending strength of Example 1 is shown as a function of the number of repairs. Figure 6a-6b As shown in the figure, after the sample was recycled and solidified, it changed from fragments to a uniform substance, with no obvious defects and no color change, indicating that BMI did not self-aggregate. Figure 7As shown, during the recycling process up to 5 times, the bending performance of the resin basically remained at around 35MPa, and the repair efficiency was above 90%.
[0084] Example 2
[0085] A method for preparing a recyclable and repairable epoxy resin based on DA bonds, with the steps referring to Example 1. When performing step S1, the epoxy resin is E-51, with a content of 58.1wt%; the monoepoxy diluent is glycidyl phenyl ether, with a content of 20.2wt%; the FA content is 21.7wt%; the rotational viscosity of FA-EP prepared in step S1 at 120°C is 3027mPa·s. When performing step S2, the FA-EP content is 71wt%; BMI is bismaleimide diphenylmethane, with a content of 29wt%; the average particle size of the mixed powder obtained in step S2 is 187μm.
[0086] The prepared DA-EP, during up to 8 repair processes, maintained a repair time of about 23 minutes, and the color of the resin did not change after multiple repairs; during up to 4 recycling processes, the bending properties of the resin remained basically at about 43 MPa, and the repair efficiency was above 90%.
[0087] Example 3
[0088] A method for preparing a recyclable and repairable epoxy resin based on DA bonds, with the steps referring to Example 1. When performing step S1, the epoxy resin is F-51, with a content of 50.7wt%; the monoepoxy diluent is benzyl glycidyl ether, with a content of 28.3wt%; the FA content is 21wt%; the rotational viscosity of the FA-EP prepared in step S1 at 120°C is 3487mPa·s. When performing step S2, the FA-EP content is 72.2wt%; BMI is bismaleimide diphenylmethane, with a content of 27.8wt%; the average particle size of the mixed powder obtained in step S2 is 176μm.
[0089] The prepared DA-EP, during up to 8 repair processes, maintained a repair time of about 23 minutes, and the color of the resin did not change after multiple repairs; during up to 4 recycling processes, the bending properties of the resin remained basically at about 43 MPa, and the repair efficiency was above 90%.
[0090] Example 4
[0091] A method for preparing a recyclable and repairable epoxy resin based on DA bonds, with the steps referring to Example 1. When performing step S1, the epoxy resin is E-51, with a content of 59.7wt%; the monoepoxy diluent is n-butyl glycidyl ether, with a content of 18.0wt%; the FA content is 22.3wt%; the rotational viscosity of the FA-EP prepared in step S1 at 120°C is 2622mPa·s. When performing step S2, the FA-EP content is 76.4wt%; BMI is bismaleimide diphenylmethane, with a content of 23.6wt%; the average particle size of the mixed powder obtained in step S2 is 157μm.
[0092] The prepared DA-EP, during up to 10 repair processes, maintained a repair time of about 18 minutes. After multiple repairs, the color of the resin turned slightly red, which may be due to the small steric hindrance of the n-butyl group and the exposure of the terminal ether bond, resulting in trace BMI self-polymerization. During up to 4 recycling processes, the bending properties of the resin remained basically at about 47 MPa, and the repair efficiency was above 90%.
[0093] Embodiment 3
[0094] On the basis of Example 1 and Example 2, this embodiment provides a recyclable and repairable epoxy resin based on DA bonds. The epoxy resin is prepared by the preparation method of Example 1 and is a multi-time repairable and recyclable resin. The number of repairs can reach more than 11 times. After recycling 5 times, its mechanical properties can still be maintained at more than 90%, and the color of the resin does not change significantly after repair and recycling, indicating that in addition to participating in the DA bond reaction, bismaleimide does not self-polymerize, and the cross-linking density of the epoxy resin based on the DA bond is well maintained.
[0095] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.
Claims
1. A method for preparing a recyclable and repairable epoxy resin based on DA bonds, characterized in that: Includes steps: S1, heating the epoxy resin, furfurylamine and monoepoxy diluent under stirring and keeping the temperature to react, and then adding a preset volume of furfurylamine to the reaction product to allow the monoepoxy diluent to react completely, thereby obtaining a linear resin having a furan group in the side chain; S2, mixing and crushing the linear resin and bismaleimide to obtain a mixed powder; S3, melting the mixed powder under vacuum, so that the linear resin dissolves the bismaleimide to obtain a blend; S4, crushing the blend and then melting it to discharge bubbles in the melt, and then heat-treating the melt so that the linear resin and the bismaleimide are cross-linked and cured to obtain an epoxy resin based on DA bonds.
2. The method for preparing a recyclable and repairable epoxy resin based on DA bonds according to claim 1, characterized in that: Step S1 includes: Weigh epoxy resin, furfurylamine and monoepoxy diluent in proportion, raise the temperature to 75-85° C. under stirring, keep the temperature for 25-35 minutes, then raise the temperature to 110-120° C., keep the temperature for 1-2 hours, and react the epoxy resin, furfurylamine and monoepoxy diluent to obtain a reaction product; 1-3 ml of furfurylamine is added dropwise to the reaction product to allow the monoepoxy diluent to react completely. At the same time, the reaction system is heated to 145-155° C. and then reacted at a constant temperature for 25-35 minutes to volatilize excess furfurylamine, thereby obtaining the linear resin having a furan group on the side chain.
3. The method for preparing a recyclable and repairable epoxy resin based on DA bonds according to claim 2, characterized in that: The epoxy resin includes one or more of E-51, E-44, and F-51; The monoepoxy diluent includes one or more of phenyl glycidyl ether, alkylene glycidyl ether, and benzyl glycidyl ether; The bismaleimide includes one or more of bismaleimide diphenylmethane and phenylene bismaleimide; The linear resin has a rotational viscosity at 120° C. less than or equal to 4000 mPa·s.
4. The method for preparing a recyclable and repairable epoxy resin based on DA bonds according to claim 1, characterized in that: Step S2 includes: Calculate the mass of bismaleimide according to the molar number of furan groups in the linear resin and weigh it; crushing the linear resin; The crushed linear resin and the weighed bismaleimide are added to a grinder and crushed to obtain a mixed powder.
5. The method for preparing a recyclable and repairable epoxy resin based on DA bonds according to claim 4, characterized in that: The molar ratio of the furan group in the linear resin to the bismaleimide is 2:1; The average particle size of the mixed powder is ≤200 μm.
6. The method for preparing a recyclable and repairable epoxy resin based on DA bonds according to claim 1, characterized in that: Step S3 includes: The mixed powder is spread flat in a container, placed in a vacuum box at 145-155° C. for preheating for 10-15 minutes, and then evacuated, and maintained at a first preset vacuum degree for a first preset time to obtain the blend.
7. The method for preparing a recyclable and repairable epoxy resin based on DA bonds according to claim 6, characterized in that: The first preset vacuum degree is less than or equal to 0.02Mpa, and the first preset time is 10-15min.
8. The method for preparing a recyclable and repairable epoxy resin based on DA bonds according to claim 1, characterized in that: Step S4 includes: The blend is crushed and placed in a mold, and the mold is placed in a vacuum box that reaches the recovery temperature and kept warm for 25-35 minutes, then the vacuum box is evacuated and maintained at a second preset vacuum degree for a second preset time, and then the mold is transferred to an oven at 65-75°C for curing for 20-28 hours, and the DA bond-based epoxy resin is obtained after cooling.
9. The method for preparing a recyclable and repairable epoxy resin based on DA bonds according to claim 8, characterized in that: The recovery temperature is 110°C-130°C; The second preset vacuum degree is less than or equal to 0.01 MPa, and the second preset time is 10-20 minutes.
10. A recyclable and repairable epoxy resin based on DA bonds, characterized in that: The method is prepared according to any one of claims 1 to 9.