A composite material based on fluorine-containing resin and preparation method thereof

Abstract

The present invention relates to the technical field of epoxy resins, and discloses a composite material based on fluorine-containing resin and a preparation method thereof, including 100 parts by weight of epoxy resin, 10-25 parts by weight of fluorine-containing polyimide resin, 7-8 parts by weight of curing agent, and 0.5-0.8 parts by weight of defoamer; the fluorine-containing polyimide resin of the present invention has excellent solubility, can be well dissolved and dispersed in epoxy resin composite materials, and forms a uniform and stable composite system after curing, which can improve the mechanical strength of the material, and the fluorine-containing polyimide resin contains a flexible alkyl long chain, which has a good toughening effect on the epoxy resin, and significantly improves the elongation at break and impact toughness of the material. And the water absorption rate of the material can be reduced, and the water resistance can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of epoxy resins, in particular to a composite material based on fluorine-containing resin and a preparation method thereof. Background Art

[0002] Polyimide is a high-performance synthetic resin with the advantages of high mechanical strength, good water resistance, high temperature resistance, and high insulation performance. It is widely used. Blending polyimide with epoxy resin, polyetheretherketone, polytetrafluoroethylene and other materials can obtain composite materials with better performance. Introducing fluorine-containing groups, ether bonds, etc. into the polyimide molecular chain can give it good organic solvent solubility and expand its application field.

[0003] Epoxy resin has good curing characteristics, strong film adhesion, excellent chemical resistance, good heat resistance, and is widely used in coatings, adhesives, casting materials, etc. However, epoxy resin has a high cross-linking density of the cured product, which makes the cured material brittle, with poor impact resistance and heat resistance. This makes epoxy resin perform poorly in some applications that need to withstand large shocks or vibrations, that is, epoxy resin does not perform well in terms of toughness. Summary of the invention

[0004] The purpose of the present invention is to provide a composite material based on fluorine-containing resin and a preparation method thereof, which solves the problem of poor mechanical properties of epoxy resin.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A composite material based on fluorine-containing resin comprises 100 parts by weight of epoxy resin, 10-25 parts by weight of fluorine-containing polyimide resin, 7-8 parts by weight of curing agent and 0.5-0.8 parts by weight of defoaming agent.

[0007] The preparation method of fluorinated polyimide resin is as follows:

[0008] Nitrogen is introduced into the container, and N,N-dimethylformamide, dianhydride monomer, and fluorinated diamine monomer are added, and the reaction is stirred at room temperature for 10-15 hours. Then the solution is coated on the surface of a clean glass plate, and placed in an oven for thermal imidization treatment to obtain a fluorinated polyimide resin.

[0009] The fluorinated diamine monomer has the following structural formula I: ; In formula Ⅰ, a is any integer between 8 and 16.

[0010] Preferably, the dianhydride monomer includes pyromellitic anhydride, 4,4'-biphenyl ether dianhydride or 3,3',4,4'-biphenyltetracarboxylic anhydride.

[0011] Preferably, the curing agent includes 2-ethyl-4-methylimidazole; and the defoaming agent includes an organosilicon defoaming agent.

[0012] Preferably, the usage ratio of the dianhydride monomer, the fluorine-containing diamine monomer and N,N-dimethylformamide is 1 mol: 1-1.05 mol: 3.5-4.5 mL.

[0013] Preferably, the thermal imidization treatment is carried out in sequence at 100° C. for 1 hour, at 150° C. for 1 hour, at 200° C. for 2 hours, at 240° C. for 2 hours, and at 280° C. for 1 hour.

[0014] Preferably, the preparation method of the fluorinated diamine monomer is:

[0015] S1. Add 10-15 mL of toluene or xylene solvent, 3-nitro-4-trifluoromethylbenzoic acid, alkyl glycol, and p-toluenesulfonic acid in a molar ratio of 2.4-3:1:0.13-0.16 to a container equipped with a condenser reflux tube, heat to 100-120°C, react for 12-18 hours, concentrate under reduced pressure, wash with petroleum ether, and recrystallize the product in dichloromethane to obtain a fluorinated dinitro monomer. The reaction formula is:

[0016] ;

[0017] S2. Add 14-16 mL of ethanol, fluorinated dinitro monomer, and palladium-carbon catalyst to a container equipped with a condenser reflux tube, heat to 70-80°C, and dropwise add 80% mass fraction of hydrazine hydrate solution, wherein the mass ratio of fluorinated dinitro monomer, palladium-carbon catalyst, and hydrazine hydrate solution is 1:0.12-0.15:6-8; stir and react for 6-12 hours, filter and concentrate the filtrate under reduced pressure, and recrystallize the product in dichloromethane to obtain a fluorinated diamine monomer. The reaction formula is:

[0018] ;

[0019] Preferably, the structural formula of the alkyl glycol is , a is any integer between 8 and 16.

[0020] Preferably, the preparation method of the composite material based on fluorine-containing resin is: add tetrahydrofuran and fluorine-containing polyimide resin into a container, stir and dissolve, then add epoxy resin, curing agent, defoaming agent, mix well, and obtain the composite material based on fluorine-containing resin.

[0021] The technical effect of the present invention is as follows: the present invention uses 3-nitro-4-trifluoromethylbenzoic acid and alkyl glycol as reactants, undergoes esterification and nitro reduction reactions, obtains a novel fluorinated diamine monomer containing an alkyl long chain, and then undergoes polymerization reaction with dianhydride monomers such as pyromellitic anhydride. The obtained fluorinated polyimide has good solubility and exhibits good solubility in solvents such as tetrahydrofuran, N,N-dimethylformamide, N-methylpyrrolidone, and chloroform, which is convenient for subsequent preparation of solvent-based epoxy resin composite materials.

[0022] The invention uses cheap and easily available tetrahydrofuran with a low boiling point as a solvent, an epoxy resin as a matrix, and a fluorinated polyimide resin as a toughening agent. The fluorinated polyimide resin has excellent solubility and can be well dissolved and dispersed in the epoxy resin composite material. The polyimide has excellent mechanical properties and is evenly dispersed in the epoxy resin material to form a uniform and stable composite system after curing, which can improve the mechanical strength of the material. The main chain of the fluorinated polyimide resin contains a flexible long alkyl chain, which has a good toughening effect on the epoxy resin and significantly improves the elongation at break and the impact toughness of the material.

[0023] The fluorine-containing polyimide resin of the present invention contains a hydrophobic alkyl long chain and a fluorine-containing group, and is uniformly dispersed in the epoxy resin composite material, which is beneficial to reducing the water absorption rate of the material and improving the water resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0025] Figure 1 This is an infrared spectrum test chart of the fluorine-containing polyimide resin prepared by the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Example 1

[0027] (1) Add 25 mL of toluene solvent, 48 mmol of 3-nitro-4-trifluoromethylbenzoic acid, 20 mmol of 1,10-decanediol, and 3 mmol of p-toluenesulfonic acid into a container equipped with a condenser reflux tube, heat to 100°C, react for 12 hours, concentrate under reduced pressure, wash with petroleum ether, and recrystallize the product in dichloromethane to obtain a fluorinated dinitro monomer.

[0028] (2) Add 70 mL of ethanol, 5 g of fluorinated dinitro monomer, and 0.68 g of palladium-carbon catalyst to a container equipped with a condenser reflux tube, heat to 80°C, dropwise add 30 g of 80% by mass hydrazine hydrate solution, stir and react for 6 h, filter and concentrate the filtrate under reduced pressure, and recrystallize the product in dichloromethane to obtain a fluorinated diamine monomer.

[0029] (3) Nitrogen is introduced into the container, and 140 mL of N,N-dimethylformamide, 40 mmol of pyromellitic anhydride, and 40 mmol of fluorinated diamine monomer are added. The reaction is stirred at room temperature for 12 h, and then the solution is coated on the surface of a clean glass plate and placed in an oven for thermal imidization treatment. The heat treatment is sequentially maintained at 100°C for 1 h, 150°C for 1 h, 200°C for 2 h, 240°C for 2 h, and 280°C for 1 h to obtain a fluorinated polyimide resin.

[0030] (4) Add 120 mL of tetrahydrofuran and 10 g of fluorinated polyimide resin into a container, stir to dissolve, then add 100 g of epoxy resin E51, 7.3 g of curing agent 2-ethyl-4-methylimidazole, and 0.5 g of silicone defoamer BYK-A 525, mix well, and obtain a composite material based on fluorinated resin. Example 2

[0031] (1) Add 20 mL of xylene solvent, 60 mmol of 3-nitro-4-trifluoromethylbenzoic acid, 20 mmol of 1,12-dodecanediol, and 2.6 mmol of p-toluenesulfonic acid into a container equipped with a condenser reflux tube, heat to 120°C, react for 12 hours, concentrate under reduced pressure, wash with petroleum ether, and recrystallize the product in dichloromethane to obtain a fluorinated dinitro monomer.

[0032] (2) Add 80 mL of ethanol, 5 g of fluorinated dinitro monomer, and 0.6 g of palladium-carbon catalyst to a container equipped with a condenser reflux tube, heat to 75°C, dropwise add 40 g of 80% by mass hydrazine hydrate solution, stir to react for 12 h, filter, and concentrate the filtrate under reduced pressure. The product is recrystallized in dichloromethane to obtain a fluorinated diamine monomer.

[0033] (3) Nitrogen was introduced into the container, and 180 mL of N,N-dimethylformamide, 40 mmol of 4,4'-biphenyl ether dianhydride, and 42 mmol of fluorinated diamine monomer were added. The mixture was stirred and reacted at room temperature for 10 h. The solution was then coated on the surface of a clean glass plate and placed in an oven for thermal imidization. The mixture was kept at 100°C for 1 h, 150°C for 1 h, 200°C for 2 h, 240°C for 2 h, and 280°C for 1 h, to obtain a fluorinated polyimide resin.

[0034] (4) Add 150 mL of tetrahydrofuran and 15 g of fluorinated polyimide resin into a container, stir to dissolve, then add 100 g of epoxy resin E51, 8 g of curing agent 2-ethyl-4-methylimidazole, and 0.7 g of silicone defoamer BYK-A 525, mix well, and obtain a composite material based on fluorinated resin. Example 3

[0035] (1) Add 20 mL of toluene solvent, 48 mmol of 3-nitro-4-trifluoromethylbenzoic acid, 20 mmol of 1,16-hexadecanediol, and 2.6 mmol of p-toluenesulfonic acid into a container equipped with a condenser reflux tube, heat to 100°C, react for 18 hours, concentrate under reduced pressure, wash with petroleum ether, and recrystallize the product in dichloromethane to obtain a fluorinated dinitro monomer.

[0036] (2) Add 80 mL of ethanol, 5 g of fluorinated dinitro monomer, and 0.6 g of palladium-carbon catalyst to a container equipped with a condenser reflux tube, heat to 80°C, dropwise add 35 g of 80% by mass hydrazine hydrate solution, stir to react for 12 h, filter, and concentrate the filtrate under reduced pressure. The product is recrystallized in dichloromethane to obtain a fluorinated diamine monomer.

[0037] (3) Nitrogen was introduced into the container, and 150 mL of N,N-dimethylformamide, 40 mmol of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, and 40 mmol of fluorinated diamine monomer were added. The mixture was stirred and reacted at room temperature for 15 h. The solution was then coated on the surface of a clean glass plate and placed in an oven for thermal imidization treatment. The mixture was kept at 100°C for 1 h, 150°C for 1 h, 200°C for 2 h, 240°C for 2 h, and 280°C for 1 h, to obtain a fluorinated polyimide resin.

[0038] (4) Add 180 mL of tetrahydrofuran and 20 g of fluorinated polyimide resin into a container, stir to dissolve, then add 100 g of epoxy resin E51, 7 g of curing agent 2-ethyl-4-methylimidazole, and 0.7 g of silicone defoamer BYK-A 525, mix well, and obtain a composite material based on fluorinated resin. Example 4

[0039] (1) Add 30 mL of xylene solvent, 52 mmol of 3-nitro-4-trifluoromethylbenzoic acid, 20 mmol of 1.8-octanediol, and 3.2 mmol of p-toluenesulfonic acid to a container equipped with a condenser reflux tube, heat to 100°C, react for 12 hours, concentrate under reduced pressure, wash with petroleum ether, and recrystallize the product in dichloromethane to obtain a fluorinated dinitro monomer.

[0040] (2) Add 80 mL of ethanol, 5 g of fluorinated dinitro monomer, and 0.75 g of palladium-carbon catalyst to a container equipped with a condenser reflux tube, heat to 70°C, dropwise add 40 g of 80% by mass hydrazine hydrate solution, stir and react for 6 h, filter and concentrate the filtrate under reduced pressure, and recrystallize the product in dichloromethane to obtain a fluorinated diamine monomer.

[0041] (3) Nitrogen is introduced into the container, and 150 mL of N,N-dimethylformamide, 40 mmol of pyromellitic anhydride, and 40 mmol of fluorinated diamine monomer are added. The reaction is stirred at room temperature for 12 h, and then the solution is coated on the surface of a clean glass plate and placed in an oven for thermal imidization treatment. The heat is maintained at 100°C for 1 h, 150°C for 1 h, 200°C for 2 h, 240°C for 2 h, and 280°C for 1 h, respectively, to obtain a fluorinated polyimide resin.

[0042] (4) Add 180 mL of tetrahydrofuran and 25 g of fluorinated polyimide resin into a container, stir to dissolve, then add 100 g of epoxy resin E51, 7.3 g of curing agent 2-ethyl-4-methylimidazole, and 0.8 g of silicone defoamer BYK-A 525, mix well, and obtain a composite material based on fluorinated resin.

[0043] Analysis Example: The fluorinated polyimide resin prepared in Example 1 was analyzed by infrared spectroscopy using a Nicolet 6700 Fourier transform infrared spectrometer produced by Thermo Corporation of the United States. Figure 1 As shown in the infrared spectrum, 3398cm -1 The peak at 1240 cm is the stretching vibration peak of N—H in amide. -1 is CN stretching vibration, 1785 cm -1 and 1727cm -1 The characteristic peaks correspond to the symmetric and antisymmetric coupling vibrations of the carbonyl group of the imide ring at 1598 cm -1 The benzene ring skeleton vibration peak appears, from which it can be inferred that the corresponding fluorinated polyimide is obtained by the reaction of dianhydride and diamine.

[0044] Comparative Example 1

[0045] (1) Add 120 mL of tetrahydrofuran, 100 g of epoxy resin E51, 7.3 g of curing agent 2-ethyl-4-methylimidazole, and 0.5 g of silicone defoamer BYK-A 525 into a container and mix well to obtain a composite material based on a fluorine-containing resin.

[0046] Comparative Example 2

[0047] (1) Nitrogen was introduced into the container, and 140 mL of N,N-dimethylformamide, 40 mmol of pyromellitic anhydride, and 40 mmol of p-phenylenediamine were added. The mixture was stirred at room temperature for 12 h. The solution was then coated on the surface of a clean glass plate and placed in an oven for thermal imidization. The mixture was kept at 100°C for 1 h, 150°C for 1 h, 200°C for 2 h, 240°C for 2 h, and 280°C for 1 h, to obtain a polyimide resin.

[0048] (2) Add 120 mL of tetrahydrofuran and 10 g of polyimide resin into a container, stir, add 100 g of epoxy resin E51, 7.3 g of curing agent 2-ethyl-4-methylimidazole, and 0.5 g of silicone defoaming agent BYK-A 525, and mix well to obtain a composite material based on fluorine-containing resin.

[0049] Comparative Example 3

[0050] (1) Nitrogen was introduced into the container, and 140 mL of N,N-dimethylformamide, 40 mmol of pyromellitic anhydride, and 40 mmol of 2,2-bis(trifluoromethyl)diaminobiphenyl (structural formula: , CAS number is 341-58-2), the reaction is stirred at room temperature for 12 hours, and then the solution is coated on the surface of a clean glass plate, placed in an oven for thermal imidization treatment, and kept at 100°C for 1 hour, 150°C for 1 hour, 200°C for 2 hours, 240°C for 2 hours, and 280°C for 1 hour in sequence to obtain a fluorinated polyimide resin.

[0051] (4) Add 120 mL of tetrahydrofuran and 10 g of fluorinated polyimide resin into a container, stir to dissolve, then add 100 g of epoxy resin E51, 7.3 g of curing agent 2-ethyl-4-methylimidazole, and 0.5 g of silicone defoamer BYK-A 525, mix well, and obtain a composite material based on fluorinated resin.

[0052] Solubility test of fluorinated polyimide resin: add 120 mL of solvent and 10 g of fluorinated polyimide resin (Comparative Example 2 is polyimide resin) into a container, stir for 24 hours, and observe the solubility of polyimide.

[0053] Table 1

[0054] ;

[0055] After testing, Examples 1-4 use fluorinated diamine monomers and dianhydride monomers such as pyromellitic anhydride to carry out polymerization reactions, and the obtained fluorinated polyimide has good solubility in solvents such as tetrahydrofuran, N,N-dimethylformamide, N-methylpyrrolidone, and chloroform, which is convenient for the subsequent preparation of solvent-based epoxy resin composite materials.

[0056] Observation of the solution state of the fluorine-containing resin-based composite material.

[0057] Mechanical properties test of fluorine-containing resin based composite materials: The fluorine-containing resin based composite materials were cured at 60°C for 2h and at 100°C for 4h, respectively, to make casting specimens, and the mechanical properties were tested according to the GB / T 2567-2021 method.

[0058] The casting sample was made into a sample of 8cm×8cm×2cm, dried, weighed, and then placed in water at 25°C and soaked for 120h. The sample was taken out, the surface moisture was wiped off, weighed, and the water absorption rate was calculated.

[0059] Water absorption rate = (mass after water absorption - mass before water absorption) ÷ mass before water absorption × 100%.

[0060] Table 2

[0061] ;

[0062] Each embodiment adds a fluorinated polyimide resin, which has good solubility in tetrahydrofuran solvent, and the obtained composite material is transparent and precipitated, so that the fluorinated polyimide resin can be evenly dispersed in the tetrahydrofuran solution of the epoxy resin composite material. The polyimide has excellent mechanical properties and is evenly dispersed in the epoxy resin, which can improve the mechanical strength of the material. The fluorinated polyimide resin contains a flexible alkyl long chain, which can be used as a toughening agent and has a good toughening effect on the epoxy resin. Compared with comparative example 1, the elongation at break and impact toughness of the composite material are significantly improved. The fluorinated polyimide resin contains a hydrophobic alkyl long chain and a fluorinated group, which is evenly dispersed in the epoxy resin composite material, which is beneficial to reduce the water absorption rate of the material and improve the water resistance.

[0063] Comparative Example 2 uses pyromellitic anhydride and conventional p-phenylenediamine as raw materials. The prepared polyimide has poor solubility in solvents such as tetrahydrofuran, and the obtained fluorine-containing resin-based composite material has a large amount of precipitation, which makes it impossible for the polyimide to be evenly dispersed in the solution of the epoxy resin composite material. In addition, the polyimide does not contain flexible alkyl long chains, and the toughening effect is poor. The tensile strength, elongation at break and impact toughness of the epoxy resin composite material are low. In addition, the polyimide does not contain hydrophobic alkyl long chains and fluorine-containing groups, and the water absorption rate of the epoxy resin material is large, and the water resistance is poor.

[0064] Comparative Example 3 uses pyromellitic anhydride and conventional 2,2-bis(trifluoromethyl)diaminobiphenyl as raw materials to prepare a fluorinated polyimide resin that does not contain flexible and hydrophobic alkyl long chains, has a poor toughening effect, and has lower elongation at break and impact toughness than those of the various embodiments. It also has a high water absorption rate and poor water resistance.

[0065] Although the present invention has been described above with reference to the embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed by the present invention may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A composite material based on fluorine-containing resin, characterized in that: The fluorine-containing resin-based composite material comprises 100 parts by weight of epoxy resin, 10-25 parts by weight of fluorine-containing polyimide resin, 7-8 parts by weight of curing agent, and 0.5-0.8 parts by weight of defoaming agent; The preparation method of the fluorinated polyimide resin is as follows: Nitrogen is introduced into the container, N,N-dimethylformamide, dianhydride monomer, and fluorine-containing diamine monomer are added, and the mixture is stirred and reacted at room temperature for 10-15 hours, and then the solution is coated on the surface of a clean glass plate, and placed in an oven for thermal imidization treatment to obtain a fluorine-containing polyimide resin; The fluorinated diamine monomer has the following structural formula: ; In the structural formula, a is any integer between 8 and 16; The dianhydride monomer includes pyromellitic anhydride, 4,4'-biphenyl ether dianhydride or 3,3',4,4'-biphenyltetracarboxylic anhydride.

2. The fluorine-containing resin-based composite material according to claim 1, characterized in that: The curing agent includes 2-ethyl-4-methylimidazole; the defoaming agent includes an organic silicon defoaming agent.

3. The fluorine-containing resin-based composite material according to claim 1, characterized in that: The usage ratio of the dianhydride monomer and the fluorine-containing diamine monomer is 1 mol:1-1.05 mol.

4. The fluorine-containing resin-based composite material according to claim 1, characterized in that: The thermal imidization treatment is carried out in sequence at 100° C. for 1 hour, at 150° C. for 1 hour, at 200° C. for 2 hours, at 240° C. for 2 hours, and at 280° C. for 1 hour.

5. The fluorine-containing resin-based composite material according to claim 3, characterized in that: The preparation method of the fluorine-containing diamine monomer is: S1. Add solvent, 3-nitro-4-trifluoromethylbenzoic acid, alkyl glycol, p-toluenesulfonic acid to a container equipped with a condenser reflux tube, heat to 100-120° C., react for 12-18 hours, concentrate under reduced pressure, wash, and recrystallize to obtain a fluorine-containing dinitro monomer; S2. Add ethanol, fluorine-containing dinitro monomer and palladium carbon catalyst to a container equipped with a condenser reflux tube, heat to 70-80°C, drop hydrazine hydrate solution, stir to react for 6-12h, filter, concentrate the filtrate under reduced pressure, and recrystallize to obtain a fluorine-containing diamine monomer.

6. The fluorine-containing resin-based composite material according to claim 5, characterized in that: The solvent in S1 is toluene or xylene.

7. The fluorine-containing resin-based composite material according to claim 5, characterized in that: In S1, the usage ratio of 3-nitro-4-trifluoromethylbenzoic acid, alkyl glycol and p-toluenesulfonic acid is 2.4-3 mol:1 mol:0.13-0.16 mol; the structural formula of alkyl glycol is , a is any integer between 8 and 16.

8. The fluorine-containing resin-based composite material according to claim 5, characterized in that: In the S2, the mass ratio of the fluorine-containing dinitro monomer, the palladium-carbon catalyst, and the hydrazine hydrate solution is 1:0.12-0.15:6-8.

9. A method for preparing a composite material based on a fluorine-containing resin according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: adding tetrahydrofuran and fluorine-containing polyimide resin into a container, stirring and dissolving, adding epoxy resin, curing agent and defoaming agent, and mixing well to obtain a composite material based on fluorine-containing resin.

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