A preparation method of a carbon fiber composite material

Abstract

The present invention relates to the technical field of carbon fiber composite materials, and discloses a preparation method of a carbon fiber composite material. The carbon fiber composite material of the present invention comprises 5-20 parts by weight of oxidized carbon fiber, 3-15 parts by weight of a phosphonate phthalazinone flame retardant, 100 parts by weight of epoxy resin, 2.8-3.5 parts by weight of a curing agent, etc. The phosphonate phthalazinone flame retardant contains carboxyl groups, which can form hydrogen bond interaction forces with hydroxyl groups, carboxyl groups, etc. on the surface of the oxidized carbon fiber, thereby adhering to and modifying the surface of the oxidized carbon fiber. The dispersibility of the carbon fiber is improved, and the compatibility with the epoxy resin is improved, enhancing the tensile strength and high-temperature resistance of the material. The phosphonate phthalazinone flame retardant contains phosphonate flame retardant groups and nitrogen-containing heterocycles, forming a nitrogen-phosphorus flame retardant system, which improves the flame retardancy of the epoxy resin material.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon fiber composite materials, and specifically to a preparation method of carbon fiber composite materials. Background Art

[0002] Carbon fiber is an inorganic fiber material with excellent comprehensive performance, light weight, high mechanical strength, high modulus, and strong high-temperature resistance, and is widely used in polymer materials such as epoxy resin, acrylic resin, polyethylene, and polypropylene. Chinese Patent CN110734537B discloses a latent halogen-free flame-retardant epoxy resin curing agent, an epoxy resin prepreg, and a carbon fiber composite material. By reacting phenolic hydroxyl aromatic aldehyde, aminoimidazole, and DOPO, a curing agent with latent and halogen-free flame retardancy is obtained, making the composite material of epoxy resin and carbon fiber have excellent mechanical properties and flame retardancy. In order to improve the compatibility between carbon fiber and polymer resin, the carbon fiber usually needs to be surface-modified. After the carbon fiber is oxidized by sulfuric acid, nitric acid, hydrogen peroxide, etc., oxygen-containing functional groups such as hydroxyl and carboxyl can be introduced on the surface, and then further coated and reacted with polyaniline, silane coupling agent, titanate coupling agent, etc. to obtain functional carbon fiber, which can more effectively improve the mechanical properties, high-temperature resistance, etc. of the resin material. Summary of the Invention

[0003] The present invention solves the problem of poor flame retardancy and other properties of carbon fiber epoxy resin composites.

[0004] The technical solution of the present invention: A preparation method of a carbon fiber composite material:

[0005] (1) Add 5-20 parts by weight of oxidized carbon fiber to ethanol, disperse it by ultrasonic treatment, then add 3-15 parts by weight of phosphonate phthalazinone flame retardant, stir and then rotary evaporate to remove ethanol. Add the mixture to 100 parts by weight of epoxy resin, then add 0.4-0.8 parts by weight of polyether-modified silicone defoamer and 2.8-3.5 parts by weight of curing agent 2-ethyl-4-methylimidazole, stir and then pour it into a mold, perform vacuum degassing, heat curing, and demolding to obtain a carbon fiber composite material.

[0006] Preferably, the conditions for heat curing are to cure at 80-90°C for 2-3h first, and then cure at 120-130°C for 1.5-2h.

[0007] Preferably, the preparation method of oxidized carbon fiber is: Add carbon fiber to concentrated sulfuric acid and concentrated nitric acid, disperse it by ultrasonic treatment, heat to 90-100°C, perform condensation reflux reaction for 18-24h, pour the solution into water for dilution, filter and then wash with sodium carbonate solution and water in sequence, and dry to obtain oxidized carbon fiber.

[0008] Preferably, the preparation method of the phosphonate phthalazinone flame retardant is as follows: 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one, 3-bromo-2-(bromomethyl)propionic acid, and sodium carbonate are added to acetonitrile, and the mixture is heated to 55-70 °C and reacted for 18-24 h. The acetonitrile is removed by rotary evaporation, and the product is washed successively with hydrochloric acid solution and water. The product is separated by silica gel column chromatography, and the eluent is ethyl acetate and petroleum ether solution to obtain the phthalazinone precursor.

[0009] (2) The phthalazinone precursor, 5,5-dimethyl-2-chloro-1,3,2-dioxaphosphorinane 2-oxide, and triethylamine are added to dichloromethane, and the reaction is carried out at 20-25 °C for 12-18 h. The dichloromethane is removed by rotary evaporation, and the product is separated by silica gel column chromatography. The eluent is ethyl acetate and petroleum ether solution to obtain the phosphonate phthalazinone flame retardant. The reaction formula is as follows:

[0010] 。

[0011] Preferably, the molar ratio of 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one, 3-bromo-2-(bromomethyl)propionic acid, and potassium carbonate in (1) is (2-2.4):1:(2.6-3.4).

[0012] Preferably, the molar ratio of the phthalazinone precursor, 5,5-dimethyl-2-chloro-1,3,2-dioxaphosphorinane 2-oxide, and triethylamine in (2) is 1:(2-2.2):(2-2.2).

[0013] The beneficial technical effects of the present invention are as follows: The phosphonate phthalazinone flame retardant prepared by the present invention contains carboxyl groups, and during the stirring and mixing process, it can form hydrogen bond interactions with the hydroxyl groups and carboxyl groups on the surface of the oxidized carbon fiber, thereby attaching and modifying the phosphonate phthalazinone flame retardant on the surface of the oxidized carbon fiber. After the organic modification of the flame retardant, the dispersibility of the carbon fiber becomes better. When added to epoxy resin, the compatibility with epoxy resin becomes better, enabling the carbon fiber to have a better strengthening effect and improving the tensile strength of the material. At the same time, the oxidized carbon fiber is uniformly dispersed in the epoxy resin, and the thermal decomposition temperature and high-temperature resistance of the composite material also become better.

[0014] The phosphonate phthalazinone flame retardant of the present invention contains a phosphonate flame retardant group and a nitrogen-containing heterocycle, forming a nitrogen-phosphorus flame retardant system, which improves the charring property of the epoxy resin material during combustion, increases the limiting oxygen index of the composite material, and reaches the V1 to V0 grade in the UL94 test, and the flame retardancy becomes better.

[0015] During the high-temperature thermal curing process of the present invention, the carboxyl group contained in the phosphonate phthalazinone flame retardant can undergo a curing reaction with the epoxy resin, thereby introducing the heat-resistant phthalazinone structure into the molecular chain of the epoxy resin, which can further improve the high-temperature resistance and thermal decomposition temperature of the material. Moreover, as a reactive flame retardant, the phosphonate phthalazinone flame retardant will not have an adverse effect on the mechanical properties of the epoxy resin. Detailed Embodiments

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0017] The following epoxy resin model is bisphenol A type epoxy resin E44. Carbon fiber, with an average fineness of 7 μm. The polyether-modified silicone defoamer model is DT-698.

[0018] The CAS registration number of 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one is 152594-70-2. The CAS registration number of 3-bromo-2-(bromomethyl)propanoic acid is 41459-42-1. The CAS registration number of 5,5-dimethyl-2-chloro-1,3,2-dioxaphosphorinane 2-oxide is 4090-55-5.

[0019] Example 1:

[0020] (1) Add 20 g of carbon fiber to 450 mL of concentrated sulfuric acid (mass fraction 98%) and 150 mL of concentrated nitric acid (mass fraction 70%), ultrasonically disperse for 2 h, heat to 90 °C, and carry out a condensation reflux reaction for 24 h. Pour the solution into water for dilution, filter, and wash successively with sodium carbonate solution and water, and then dry to obtain oxidized carbon fiber.

[0021] (2) Add 0.2 mol of 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one, 0.1 mol of 3-bromo-2-(bromomethyl)propanoic acid, and 0.68 mol of sodium carbonate to 700 mL of acetonitrile, heat to 70 °C, react for 18 h, rotary evaporate to remove acetonitrile, wash successively with hydrochloric acid solution and water, and separate the product by silica gel column chromatography. The eluent is an ethyl acetate and petroleum ether solution to obtain the phthalazinone precursor.

[0022] (3) Add 0.2 mol of phthalazinone precursor, 0.4 mol of 5,5-dimethyl-2-chloro-1,3,2-dioxaphosphorinane 2-oxide, and 0.4 mol of triethylamine to 1 L of dichloromethane. React at 20 °C for 18 h. Rotate and evaporate to remove dichloromethane. The product is separated by silica gel column chromatography, and the eluent is an ethyl acetate and petroleum ether solution to obtain the phosphonate phthalazinone flame retardant.

[0023] (4) Add 50 g of oxidized carbon fiber to ethanol, disperse it by ultrasonic treatment for 2 h, then add 30 g of the phosphonate phthalazinone flame retardant. Stir and then rotate and evaporate to remove ethanol. Add the mixture to 1 kg of epoxy resin, then add 5 g of polyether-modified silicone defoamer and 30 g of curing agent 2-ethyl-4-methylimidazole. Stir and pour into a mold, and perform vacuum degassing. First, cure thermally at 90 °C for 2 h, then cure thermally at 130 °C for 1.5 h, and demold to obtain the carbon fiber composite material.

[0024] Example 2:

[0025] (1) Add 20 g of carbon fiber to 450 mL of concentrated sulfuric acid (mass fraction 98%) and 150 mL of concentrated nitric acid (mass fraction 70%). Disperse it by ultrasonic treatment for 2 h, heat to 100 °C, and react under reflux for 18 h. Pour the solution into water for dilution, filter, and wash successively with sodium carbonate solution and water, and dry to obtain oxidized carbon fiber.

[0026] (2) Add 0.24 mol of 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one, 0.1 mol of 3-bromo-2-(bromomethyl)propanoic acid, and 0.52 mol of sodium carbonate to 800 mL of acetonitrile. Heat to 55 °C and react for 24 h. Rotate and evaporate to remove acetonitrile, wash successively with hydrochloric acid solution and water, and separate the product by silica gel column chromatography. The eluent is an ethyl acetate and petroleum ether solution to obtain the phthalazinone precursor.

[0027] (3) Add 0.2 mol of phthalazinone precursor, 0.44 mol of 5,5-dimethyl-2-chloro-1,3,2-dioxaphosphorinane 2-oxide, and 0.44 mol of triethylamine to 1 L of dichloromethane. React at 25 °C for 12 h. Rotate and evaporate to remove dichloromethane. The product is separated by silica gel column chromatography, and the eluent is an ethyl acetate and petroleum ether solution to obtain the phosphonate phthalazinone flame retardant.

[0028] (4) Add 100 g of oxidized carbon fiber to ethanol, disperse it by ultrasonic wave for 2 h, then add 70 g of phosphonate phthalazinone flame retardant. After stirring, remove ethanol by rotary evaporation. Add the mixture to 1 kg of epoxy resin, then add 4 g of polyether-modified silicone defoamer and 35 g of curing agent 2-ethyl-4-methylimidazole. Stir and pour the mixture into a mold, degas it under vacuum. First, cure it thermally at 80 °C for 3 h, then cure it thermally at 120 °C for 2 h, and demold to obtain a carbon fiber composite material.

[0029] Example 3:

[0030] (1) Add 150 g of oxidized carbon fiber to ethanol, disperse it by ultrasonic wave for 2 h, then add 110 g of phosphonate phthalazinone flame retardant. After stirring, remove ethanol by rotary evaporation. Add the mixture to 1 kg of epoxy resin, then add 8 g of polyether-modified silicone defoamer and 32 g of curing agent 2-ethyl-4-methylimidazole. Stir and pour the mixture into a mold, degas it under vacuum. First, cure it thermally at 90 °C for 2 h, then cure it thermally at 120 °C for 2 h, and demold to obtain a carbon fiber composite material.

[0031] Example 4:

[0032] (1) Add 200 g of oxidized carbon fiber to ethanol, disperse it by ultrasonic wave for 2 h, then add 150 g of phosphonate phthalazinone flame retardant (prepared according to the method of Example 1). After stirring, remove ethanol by rotary evaporation. Add the mixture to 1 kg of epoxy resin, then add 5 g of polyether-modified silicone defoamer and 28 g of curing agent 2-ethyl-4-methylimidazole. Stir and pour the mixture into a mold, degas it under vacuum. First, cure it thermally at 85 °C for 3 h, then cure it thermally at 120 °C for 2 h, and demold to obtain a carbon fiber composite material.

[0033] Comparative Example 1:

[0034] (1) Add 5 g of polyether-modified silicone defoamer and 30 g of curing agent 2-ethyl-4-methylimidazole to 1 kg of epoxy resin. Stir and pour the mixture into a mold, degas it under vacuum. First, cure it thermally at 90 °C for 2 h, then cure it thermally at 130 °C for 1.5 h, and demold to obtain an epoxy resin material.

[0035] Comparative Example 2:

[0036] (1) Add 50 g of oxidized carbon fiber, 5 g of polyether-modified silicone defoamer and 30 g of curing agent 2-ethyl-4-methylimidazole to 1 kg of epoxy resin. Stir and pour the mixture into a mold, degas it under vacuum. First, cure it thermally at 90 °C for 2 h, then cure it thermally at 130 °C for 1.5 h, and demold to obtain a carbon fiber composite material.

[0037] Comparative Example 3:

[0038] (1) Add 30 g of phthalazinone phosphate flame retardant (prepared according to the method of Example 1), 5 g of polyether-modified silicone defoamer, and 30 g of curing agent 2-ethyl-4-methylimidazole to 1 kg of epoxy resin. After stirring, pour it into a mold, degas under vacuum, first cure thermally at 90 °C for 2 h, then cure thermally at 130 °C for 1.5 h, and demold to obtain an epoxy resin material.

[0039] Comparative Example 4:

[0040] (1) Add 50 g of carbon fiber to ethanol, disperse it by ultrasonic treatment for 2 h, then add 30 g of phthalazinone phosphate flame retardant (prepared according to the method of Example 1). After stirring, rotary evaporate to remove ethanol. Add the mixture to 1 kg of epoxy resin, then add 5 g of polyether-modified silicone defoamer and 30 g of curing agent 2-ethyl-4-methylimidazole. After stirring, pour it into a mold, degas under vacuum, first cure thermally at 90 °C for 2 h, then cure thermally at 130 °C for 1.5 h, and demold to obtain a carbon fiber composite material.

[0041] Comparative Example 5

[0042] (1) Add 50 g of oxidized carbon fiber (prepared according to the method of Example 1) to ethanol, disperse it by ultrasonic treatment for 2 h, then add 30 g of phthalazinone precursor (prepared according to the method of Example 1). After stirring, rotary evaporate to remove ethanol. Add the mixture to 1 kg of epoxy resin, then add 5 g of polyether-modified silicone defoamer and 30 g of curing agent 2-ethyl-4-methylimidazole. After stirring, pour it into a mold, degas under vacuum, first cure thermally at 90 °C for 2 h, then cure thermally at 130 °C for 1.5 h, and demold to obtain a carbon fiber composite material.

[0043] Test the tensile properties of the epoxy resin cast material according to GB / T 2567-2021. Test the oxygen index according to GB / T 2406.1-2008. Test the vertical burning performance according to the UL-94 method.

[0044] Weigh 5 mg of the cast material, and perform thermal performance testing in a thermogravimetric analyzer under a nitrogen atmosphere at a heating rate of 10 °C / min from 25 °C to 800 °C.

[0045] Table 1 Performance Testing of Cast Materials

[0046]

[0047] After testing, the epoxy resin material of Comparative Example 1 has a low tensile strength, an oxygen index of only 25.8%, no rating in the UL94 test, poor flame retardancy, and a low initial thermal decomposition temperature (temperature at 5% mass loss) and carbon residue content, and poor high-temperature resistance.

[0048] In the composite materials of Examples 1-4, carbon fiber oxide and phosphonate phthalazinone flame retardant are added. The flame retardant contains carboxyl groups, which can form hydrogen bond interactions with hydroxyl and carboxyl groups on the surface of carbon fiber oxide during the stirring and mixing process, thereby attaching and modifying the phosphonate phthalazinone flame retardant on the surface of carbon fiber oxide. After the organic modification of the flame retardant, the dispersibility of the carbon fiber becomes better, and at the same time, the compatibility with epoxy resin is improved, making the strengthening effect of the carbon fiber better, the tensile strength of the material significantly increased, and the thermal decomposition temperature and high-temperature resistance performance also improved. The phosphonate phthalazinone flame retardant contains phosphonate flame retardant groups and nitrogen-containing heterocycles, forming a nitrogen-phosphorus flame retardant system, which significantly improves the char-forming property and flame retardancy of the epoxy resin material, increases the limiting oxygen index, and the UL94 test reaches the V1 to V0 level. During the high-temperature thermal curing process, the carboxyl groups contained in the phosphonate phthalazinone flame retardant can react with the epoxy resin, thereby introducing the heat-resistant phthalazinone blocking structure into the molecular chain of the epoxy resin, which can further improve the high-temperature resistance performance of the material and exhibit a higher thermal decomposition temperature.

[0049] Compared with Example 1, in Comparative Example 2, only carbon fiber oxide is added, its dispersibility is poor, and its compatibility with epoxy resin is also poor. The improvement in the tensile strength of the material is not high, and the limiting oxygen index is only 26.3%. There is no grade in the UL94 test, and the flame retardancy is poor.

[0050] In Comparative Example 3, only the phosphonate phthalazinone flame retardant is added. The flame retardancy of the material is significantly improved, and during the high-temperature thermal curing process, the carboxyl groups of the flame retardant can react with the epoxy resin, thereby introducing the heat-resistant phthalazinone blocking structure into the molecular chain of the epoxy resin, which can improve the thermal decomposition temperature and high-temperature resistance performance of the material. The initial thermal decomposition temperature and the residual carbon content are higher than those of Comparative Example 1, and as a reactive flame retardant, it has almost no impact on the mechanical properties of the epoxy resin. The tensile strength still remains good. However, no carbon fiber is added, and the mechanical strength is low.

[0051] In Comparative Example 4, the added carbon fiber is not oxidized by mixed acid and does not contain functional groups such as hydroxyl and carboxyl groups on the surface, so it cannot form hydrogen bond interactions with the carboxyl groups of the phosphonate phthalazinone flame retardant, and cannot attach and modify the flame retardant on the surface of the carbon fiber oxide. The organic modification of the carbon fiber is not achieved, the dispersibility of the carbon fiber cannot be improved, and the compatibility with epoxy resin is not increased either, resulting in a poor strengthening effect of the carbon fiber and a lower tensile strength of the material than that of Example 1.

[0052] The phthalazinone precursor added in Comparative Example 5 contains carboxyl groups, which can form hydrogen bond interaction forces with hydroxyl groups, carboxyl groups, etc. on the surface of carbon fibers, thereby attaching and modifying the phosphonate phthalazinone flame retardant on the surface of carbon fibers. After the organic modification of the flame retardant, the dispersibility of carbon fibers is improved, and at the same time, the compatibility with epoxy resin is enhanced, making the strengthening effect of carbon fibers better and the tensile strength of the material significantly increased. However, the phthalazinone precursor does not contain phosphonate flame retardant groups, so the flame retardancy of the material is poor.

[0053] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of the present technology can make various modifications, supplements, or use similar methods to replace the specific embodiments described, as long as they do not deviate from the concept of the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a carbon fiber composite material, characterized in that: The preparation method is as follows: (1) Add 5-20 parts by weight of oxidized carbon fiber to ethanol, disperse it by ultrasonication, then add 3-15 parts by weight of phosphate diazonium flame retardant, stir and remove ethanol by rotary evaporation, add the mixture to 100 parts by weight of epoxy resin, then add 0.4-0.8 parts by weight of defoamer and 2.8-3.5 parts by weight of curing agent, stir and cast it into a mold, vacuum degas, heat cure, and demold to obtain a carbon fiber composite material; The structural formula of the phosphate phthalazinone flame retardant is: 。 2. The method for preparing a carbon fiber composite material according to claim 1, characterized in that: The curing agent is 2-ethyl-4-methylimidazole, and the defoaming agent is a polyether-modified organic silicon defoaming agent.

3. The method for preparing a carbon fiber composite material according to claim 1, characterized in that: The heat curing conditions are: first curing at 80-90° C. for 2-3 hours, and then curing at 120-130° C. for 1.5-2 hours.

4. The method for preparing a carbon fiber composite material according to claim 1, characterized in that: The preparation method of the oxidized carbon fiber is as follows: adding the carbon fiber to concentrated sulfuric acid and concentrated nitric acid, ultrasonically dispersing, heating to 90-100° C., condensing and refluxing for 18-24 hours, pouring the solution into water for dilution, filtering, washing, and drying to obtain the oxidized carbon fiber.

5. The method for preparing a carbon fiber composite material according to claim 1, characterized in that: The preparation method of the phosphate phthalazinone flame retardant is: (1) Add 4-(4-hydroxyphenyl)-2,3-naphthyridin-1-one, 3-bromo-2-(bromomethyl)propionic acid and sodium carbonate to acetonitrile, heat to 55-70°C, react for 18-24 hours, rotary evaporate, wash, and separate by silica gel column chromatography to obtain a naphthyridinone precursor; (2) Add a phthalazinone precursor, 5,5-dimethyl-2-chloro-1,3,2-dioxaphosphahexanoyl phosphate and triethylamine to dichloromethane, react at 20-25° C. for 12-18 hours, rotary evaporate, and separate by silica gel column chromatography to obtain a phosphate phthalazinone flame retardant.

6. The method for preparing a carbon fiber composite material according to claim 5, characterized in that: The molar ratio of the 4-(4-hydroxyphenyl)-2,3-naphthylidene-1-one, 3-bromo-2-(bromomethyl)propionic acid and sodium carbonate is (2-2.4):1 (2.6-3.4).

7. The method for preparing a carbon fiber composite material according to claim 5, characterized in that: The molar ratio of the diazonium phthalide precursor, 5,5-dimethyl-2-chloro-1,3,2-dioxaphosphahexanoyl phosphate and triethylamine in (2) is 1:(2-2.2):(2-2.2).

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