A high-strength modified plastic product and its preparation process

Abstract

The present invention relates to the technical field of plastic materials, and specifically relates to a high-strength modified plastic product and its preparation process. In the present invention, modified carbon fiber, flame retardant, photoinitiator and N,N-dimethylformamide are mixed evenly, and after being irradiated with ultraviolet light, washed and dried, a composite is obtained; polyphthalamide, the composite, polyethylene wax, antioxidant and nucleating agent are mixed evenly to obtain a blend; the blend is melt extruded and granulated in a twin-screw extruder and injection molded to obtain a modified plastic product. The modified plastic product prepared by the present invention not only has excellent mechanical properties, but also has excellent flame retardant properties, effectively improving its use safety and durability.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic materials, and particularly to a high-strength modified plastic product and its preparation process. Background Art

[0002] Polyphthalamide (PPA) is a semi-aromatic polyamide, commonly known as high-temperature resistant nylon. Due to its excellent heat resistance, chemical resistance, mechanical strength and dimensional stability, it has broad application prospects in the fields of electronics, electrical appliances, automobiles, aerospace, etc. However, pure PPA materials still have some limitations in certain application scenarios, such as insufficient toughness, and the processing performance and flame retardancy need to be improved.

[0003] The enhancement of PPA and the improvement of flame retardancy are mainly achieved by filling flame retardants and carbon fibers. However, due to the lack of chemically active functional groups on the surface of carbon fibers, they usually exhibit chemical inertness, resulting in weak interfacial bonding force between carbon fibers and the PPA matrix, and it is difficult to effectively exert the reinforcing effect of carbon fibers; in terms of flame retardancy, the flame retardancy of PPA itself is relatively limited, and it is prone to combustion and thermal degradation in high-temperature environments.

[0004] Therefore, we propose a high-strength modified plastic product and its preparation process. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-strength modified plastic product and its preparation process to solve the problems raised in the prior art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A preparation process of a high-strength modified plastic product includes the following steps:

[0008] Step S1: Mix modified carbon fiber, flame retardant, photoinitiator and N,N-dimethylformamide evenly, and after ultraviolet light irradiation, washing and drying, a composite is obtained;

[0009] Step S2: Mix polyphthalamide, the composite, polyethylene wax, antioxidant and nucleating agent evenly to obtain a blend; extrude the blend in a twin-screw extruder, granulate, and injection mold to obtain a modified plastic product.

[0010] Furthermore, the modified plastic product includes the following weight components: 35 - 65 parts of polyphthalamide, 30 - 60 parts of the composite, 0.2 - 0.4 parts of polyethylene wax, 0.2 - 0.6 parts of antioxidant, and 0.3 - 0.5 parts of nucleating agent.

[0011] Further, the composite includes the following components by weight: 20-45 parts of modified carbon fiber, 10-15 parts of flame retardant, 2-4 parts of photoinitiator, and 50-100 parts of N,N-dimethylformamide.

[0012] Further, the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0013] Further, the preparation method of the modified carbon fiber is as follows:

[0014] Step (1): Adjust the pH of the Tris-HCl buffer solution to 8.5, add dopamine hydrochloride and mix evenly to obtain a dopamine hydrochloride solution; immerse the pretreated carbon fiber in the dopamine hydrochloride solution for 20-24 h, take it out and dry it to obtain poly-dopamine-coated carbon fiber;

[0015] Step (2): Mix maleic anhydride and 1,4-dioxane evenly, dropwise add a mixed solution of diethylenetriamine and 1,4-dioxane, finish dropping in 1-2 h, react at room temperature for 2-3 h, and after vacuum distillation and drying, obtain a prepolymer monomer; mix the prepolymer monomer and deionized water evenly, add ethylenediamine, react at 85-95 °C for 4-5 h, cool to room temperature, and after vacuum distillation and drying, obtain an amino-terminated hyperbranched polyamide;

[0016] Step (3): Place the poly-dopamine-coated carbon fiber in an aqueous solution of amino-terminated hyperbranched polyamide, perform ultrasonic treatment for 1-2 h, react for 3-5 h, filter and dry to obtain the modified carbon fiber.

[0017] Further, in the step (1), the concentration of the Tris-HCl buffer solution is 0.01 mol / L, the concentration of the dopamine hydrochloride solution is 2-4 mg / mL, and the mass of the pretreated carbon fiber is 2-5% of the mass of the dopamine hydrochloride solution.

[0018] Further, the preparation method of the pretreated carbon fiber is as follows:

[0019] Soak the carbon fiber in acetone for 22-24 h to remove the sizing agent on the surface, wash it with deionized water, clean it and dry it to obtain the pretreated carbon fiber.

[0020] Further, in the step (2), the mass ratio of maleic anhydride to 1,4-dioxane is 1:(4-5).

[0021] Further, in the step (2), the mass of diethylenetriamine is 1.1-1.3 times that of maleic anhydride, and the mass ratio of diethylenetriamine to 1,4-dioxane is 1:(4-5).

[0022] Further, in the step (2), the mass ratio of the prepolymer monomer to deionized water is 1:(5 - 8), and the mass of ethylenediamine is 10 - 15% of the mass of the prepolymer monomer.

[0023] Further, in the step (3), the mass ratio of the polydopamine-coated carbon fiber to the amino-terminated hyperbranched polyamide aqueous solution is 1:(20 - 30), and the concentration of the amino-terminated hyperbranched polyamide aqueous solution is 2 - 4 mg / mL.

[0024] Further, the preparation method of the flame retardant is as follows:

[0025] Step A: Under nitrogen protection, mix DOPO, 4-maleimidobenzoic acid, and N,N-dimethylformamide evenly, react at 90 - 100 °C for 1 - 2 h, continue to heat up to 125 - 135 °C and react for 6 - 8 h, cool to room temperature, recrystallize in an ice-water bath for 12 h, and after vacuum filtration, washing, and drying, obtain modified DOPO;

[0026] Step B: Mix the modified DOPO, N,N-dimethylformamide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide evenly, stir at 20 - 30 °C for 30 - 60 min, add L-cysteine, continue to stir for 12 - 24 h, and after filtration, washing, and drying, obtain the flame retardant.

[0027] Further, in the step A, the mass ratio of DOPO, 4-maleimidobenzoic acid, and N,N-dimethylformamide is 1:(1.0 - 1.2):(6 - 8).

[0028] Further, in the step B, the mass ratio of the modified DOPO, N,N-dimethylformamide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide is 1:(3 - 5):(0.08 - 0.10):(0.06 - 0.08).

[0029] Further, in the step B, the mass of L-cysteine is 1 - 2 times the mass of the modified DOPO.

[0030] Further, the model of the antioxidant is Bruggemann H161 from Germany.

[0031] Further, the model of the nucleating agent is Bruggemann P22 from Germany.

[0032] Further, in the step S1, the process conditions of ultraviolet irradiation are: irradiate with ultraviolet rays of 360 - 400 nm for 30 - 60 min, and the irradiation intensity is 20 - 35 mW / cm 2 2.

[0033] Further, in the step S2, the barrel temperatures of each section of the twin-screw extruder are successively 230 - 250 °C, 270 - 290 °C, 280 - 300 °C, 290 - 310 °C, 280 - 300 °C, 270 - 290 °C, 265 - 285 °C, 265 - 285 °C, 265 - 285 °C, 285 - 305 °C from the 1st to the 10th section, the head temperature is 290 - 310 °C, and the screw speed is 250 - 350 rpm.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. For a high-strength modified plastic product and its preparation process of the present invention, dopamine is used to modify the surface of carbon fiber to obtain poly-dopamine-coated carbon fiber. The introduction of the poly-dopamine layer not only increases the surface roughness of the carbon fiber but also enhances its surface chemical activity, providing a platform for subsequent modification. Maleic anhydride (MA) and diethylenetriamine (DETA) are used for amidation reaction to synthesize AB2 prepolymer monomer, and then ethylenediamine as the central core is introduced. A hyperbranched polyamide compound containing carbon-carbon double bonds and terminal amino groups, namely terminal amino hyperbranched polyamide, is prepared by the "one-step method". The introduction of the terminal amino hyperbranched polyamide provides a large number of amino groups and amide bonds. At the same time, through the Schiff base reaction between poly-dopamine and amino groups, the terminal amino hyperbranched polyamide is grafted onto the surface of the carbon fiber to obtain modified carbon fiber containing polyamide structural units, which has good compatibility with the polyamide structure of polyphthalamide (PPA), significantly improving the dispersion of the carbon fiber in the PPA matrix, enabling it to have a better reinforcing effect, being beneficial to improving the mechanical properties of PPA products, and thus realizing high-strength and high-performance modified plastic products.

[0036] 2. For a high-strength modified plastic product and its preparation process of the present invention, an addition reaction is carried out between the active P-H bond in the DOP0 group and the unsaturated double bond in 4-maleimidobenzoic acid to obtain DOPO containing maleimide structure and carboxyl group, that is, modified DOPO. Then, an amidation reaction occurs between the carboxyl group on the surface of the modified DOPO and the amino group of L-cysteine to introduce a mercapto group, obtaining a flame retardant containing N, P, and S elements;

[0037] On this basis, a thiol-ene click reaction occurs between the carbon-carbon double bond on the surface of the modified carbon fiber and the mercapto group in the flame retardant to prepare a composite, greatly improving the flame retardant performance of the plastic product, while enhancing the structural strength of the material, and effectively enhancing its use safety and durability. Specific embodiments

[0038] 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 embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] In this embodiment, the carbon fiber is short-cut carbon fiber, with the model of Toray T300 from Japan and the length of 5 - 8 mm; the polyphthalamide is of the model HTN502 from DuPont in the United States; the polyethylene wax is of the model AC-6A from Honeywell; the antioxidant is of the model H161 from Bruggemann in Germany; the nucleating agent is of the model P22 from Bruggemann in Germany.

[0040] In the following examples and comparative examples, 1 part is equal to 10 g.

[0041] Example 1: A preparation process of a high-strength modified plastic product, including the following processes:

[0042] Step S1: Mix 20 parts of modified carbon fiber, 10 parts of flame retardant, 2 parts of photoinitiator and 50 parts of N,N-dimethylformamide evenly, irradiate with 360 nm ultraviolet light for 30 min, and the irradiation intensity is 20 mW / cm 2 , and after washing and drying, a composite is obtained;

[0043] Step S2: Mix 35 parts of polyphthalamide, 30 parts of the composite, 0.2 part of polyethylene wax, 0.2 part of antioxidant and 0.3 part of nucleating agent evenly to obtain a blend; perform melt extrusion and granulation of the blend in a twin-screw extruder, and injection molding to obtain a modified plastic product; the barrel temperatures of each section of the twin-screw extruder are 230 °C, 270 °C, 280 °C, 290 °C, 280 °C, 270 °C, 265 °C, 265 °C, 265 °C, 285 °C in sequence from section 1 to section 10, the head temperature is 290 °C, and the screw speed is 250 rpm;

[0044] The preparation method of the modified carbon fiber is as follows:

[0045] Step (1): Adjust the pH of 0.01 mol / L Tris-HCl buffer solution to 8.5, add dopamine hydrochloride and mix evenly to obtain a 2 mg / mL dopamine hydrochloride solution; soak 25 parts of carbon fiber in acetone for 22 h to remove the sizing agent on the surface, wash it with deionized water and dry it to obtain pretreated carbon fiber; place 25 parts of pretreated carbon fiber in 1250 parts of dopamine hydrochloride solution and impregnate for 20 h, take it out and dry it to obtain poly-dopamine-coated carbon fiber;

[0046] Step (2): Mix 1 part of maleic anhydride and 4 parts of 1,4-dioxane evenly, and dropwise add a mixed solution of 1.1 parts of diethylenetriamine and 4.4 parts of 1,4-dioxane. Finish dropping in 1 h, react at room temperature for 2 h, and obtain a prepolymer monomer after vacuum distillation and drying; Mix 1 part of the prepolymer monomer and 5 parts of deionized water evenly, add 0.1 part of ethylenediamine, react at 85 °C for 4 h, cool to room temperature, and obtain an amino-terminated hyperbranched polyamide after vacuum distillation and drying;

[0047] Step (3): Place 25 parts of poly(dopamine)-coated carbon fiber in 500 parts of an aqueous solution of amino-terminated hyperbranched polyamide at 2 mg / mL, perform ultrasonic treatment for 1 h, react for 3 h, and obtain modified carbon fiber after filtration and drying;

[0048] The preparation method of the flame retardant is as follows:

[0049] Step A: Under nitrogen protection, mix 10 parts of DOPO, 10 parts of 4-maleimidobenzoic acid and 60 parts of N,N-dimethylformamide evenly, react at 90 °C for 1 h, continue to heat up to 125 °C and react for 6 h, cool to room temperature, perform recrystallization in an ice-water bath for 12 h, and obtain modified DOPO after vacuum filtration, washing and drying;

[0050] Step B: Mix 10 parts of modified DOPO, 30 parts of N,N-dimethylformamide, 0.8 part of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 0.6 part of N-hydroxysuccinimide evenly, stir at 20 °C for 30 min, add 10 parts of L-cysteine, continue to stir for 12 h, and obtain the flame retardant after filtration, washing and drying.

[0051] Example 2: A preparation process of a high-strength modified plastic product, including the following processes:

[0052] Step S1: Mix 35 parts of modified carbon fiber, 12 parts of flame retardant, 3 parts of photoinitiator and 80 parts of N,N-dimethylformamide, irradiate with 380 nm ultraviolet light for 50 min, and the irradiation intensity is 30 mW / cm 2 , and obtain a composite after washing and drying;

[0053] Step S2: Mix 50 parts of polyphthalamide, 47 parts of the composite, 0.3 part of polyethylene wax, 0.4 part of antioxidant and 0.4 part of nucleating agent evenly to obtain a blend; Perform melt extrusion and granulation of the blend in a twin-screw extruder, and injection mold to obtain a modified plastic product; The barrel temperatures of each section of the twin-screw extruder are 240 °C, 280 °C, 290 °C, 300 °C, 290 °C, 280 °C, 275 °C, 275 °C, 275 °C, 295 °C in sequence from the 1st to the 10th section, the head temperature is 300 °C, and the screw speed is 300 rpm;

[0054] The preparation method of the modified carbon fiber is as follows:

[0055] Step (1): Adjust the pH of 0.01 mol / L Tris-HCl buffer to 8.5, add dopamine hydrochloride and mix evenly to obtain a 4 mg / mL dopamine hydrochloride solution; soak 35 parts of carbon fiber in acetone for 23 h to remove the sizing agent on the surface, wash it with deionized water, dry it, and obtain pretreated carbon fiber; place 35 parts of pretreated carbon fiber in 875 parts of dopamine hydrochloride solution and impregnate it for 22 h, take it out and dry it to obtain polydopamine-coated carbon fiber;

[0056] Step (2): Mix 2 parts of maleic anhydride and 9 parts of 1,4-dioxane evenly, dropwise add a mixed solution of 2.4 parts of diethylenetriamine and 10.8 parts of 1,4-dioxane, finish dropping in 1.5 h, react at room temperature for 2.5 h, after reduced pressure distillation and drying, obtain a prepolymer monomer; mix 2 parts of prepolymer monomer and 14 parts of deionized water evenly, add 0.24 parts of ethylenediamine, react at 90 °C for 4.5 h, cool to room temperature, after reduced pressure distillation and drying, obtain amino-terminated hyperbranched polyamide;

[0057] Step (3): Place 35 parts of polydopamine-coated carbon fiber in 875 parts of an aqueous solution of 2 mg / mL amino-terminated hyperbranched polyamide, ultrasonically treat it for 1.5 h, react for 4 h, filter and dry it to obtain modified carbon fiber;

[0058] The preparation method of the flame retardant is as follows:

[0059] Step A: Under nitrogen protection, mix 12 parts of DOPO, 13.2 parts of 4-maleimidobenzoic acid and 84 parts of N,N-dimethylformamide evenly, react at 95 °C for 1.5 h, continue to heat up to 130 °C and react for 7 h, cool to room temperature, recrystallize in an ice-water bath for 12 h, after reduced pressure filtration, washing and drying, obtain modified DOPO;

[0060] Step B: Mix 12 parts of modified DOPO, 48 parts of N,N-dimethylformamide, 1.08 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 0.84 parts of N-hydroxysuccinimide evenly, stir at 25 °C for 50 min, add 18 parts of L-cysteine, continue to stir for 20 h, after filtration, washing and drying, obtain the flame retardant.

[0061] Example 3: The preparation process of a high-strength modified plastic product includes the following processes:

[0062] Step S1: Mix 45 parts of modified carbon fiber, 15 parts of flame retardant, 4 parts of photoinitiator and 100 parts of N,N-dimethylformamide, irradiate with 400 nm ultraviolet light for 60 min, and the irradiation intensity is 35 mW / cm2 , after washing and drying, a composite is obtained;

[0063] Step S2: Mix 65 parts of polyphthalamide, 60 parts of the composite, 0.4 part of polyethylene wax, 0.6 part of antioxidant, and 0.5 part of nucleating agent evenly to obtain a blend; extrude the blend through a twin-screw extruder, granulate, and injection mold to obtain a modified plastic product; the barrel temperatures of each section of the twin-screw extruder are 250 °C, 290 °C, 300 °C, 310 °C, 300 °C, 290 °C, 285 °C, 285 °C, 285 °C, and 305 °C in sequence from section 1 to section 10, the head temperature is 310 °C, and the screw speed is 350 rpm;

[0064] The preparation method of the modified carbon fiber is as follows:

[0065] Step (1): Adjust the pH of 0.01 mol / L Tris-HCl buffer to 8.5, add dopamine hydrochloride and mix evenly to obtain a 4 mg / mL dopamine hydrochloride solution; soak 45 parts of carbon fiber in acetone for 24 h to remove the sizing agent on the surface, wash it with deionized water, and dry it to obtain pretreated carbon fiber; place 45 parts of pretreated carbon fiber in 900 parts of dopamine hydrochloride solution and impregnate for 24 h, take it out and dry it to obtain poly(dopamine)-coated carbon fiber;

[0066] Step (2): Mix 3 parts of maleic anhydride and 15 parts of 1,4-dioxane evenly, dropwise add a mixed solution of 3.9 parts of diethylenetriamine and 19.5 parts of 1,4-dioxane, finish dropping in 2 h, react at room temperature for 3 h, and after vacuum distillation and drying, obtain a prepolymer monomer; mix 3 parts of prepolymer monomer and 24 parts of deionized water evenly, add 0.45 part of ethylenediamine, react at 95 °C for 5 h, cool to room temperature, and after vacuum distillation and drying, obtain an amino-terminated hyperbranched polyamide;

[0067] Step (3): Place 45 parts of poly(dopamine)-coated carbon fiber in 1350 parts of a 2 mg / mL aqueous solution of amino-terminated hyperbranched polyamide, ultrasonically treat for 2 h, react for 5 h, filter and dry to obtain modified carbon fiber;

[0068] The preparation method of the flame retardant is as follows:

[0069] Step A: Under nitrogen protection, mix 15 parts of DOPO, 18 parts of 4-maleimidobenzoic acid, and 120 parts of N,N-dimethylformamide evenly, react at 100 °C for 2 h, continue to heat up to 135 °C and react for 8 h, cool to room temperature, recrystallize in an ice-water bath for 12 h, and after vacuum filtration, washing, and drying, obtain modified DOPO;

[0070] Step B: Mix 15 parts of modified DOPO, 75 parts of N,N-dimethylformamide, 1.5 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and 1.2 parts of N-hydroxysuccinimide evenly, stir for 60 min at 30 °C, add 30 parts of L-cysteine, continue stirring for 24 h, and obtain the flame retardant after filtration, washing, and drying.

[0071] Comparative Example 1: A preparation process of a high-strength modified plastic product, including the following processes:

[0072] Step S1: Mix 35 parts of carbon fiber, 12 parts of flame retardant, 3 parts of photoinitiator, and 80 parts of N,N-dimethylformamide, irradiate with 380 nm ultraviolet light for 50 min, and the irradiation intensity is 30 mW / cm 2 , and obtain the composite after washing and drying;

[0073] Step S2: Mix 50 parts of polyphthalamide, 47 parts of the composite, 0.3 parts of polyethylene wax, 0.4 parts of antioxidant, and 0.4 parts of nucleating agent evenly to obtain a blend; melt-extrude and pelletize the blend in a twin-screw extruder, and injection mold to obtain the modified plastic product; the barrel temperatures of each section of the twin-screw extruder are 240 °C, 280 °C, 290 °C, 300 °C, 290 °C, 280 °C, 275 °C, 275 °C, 275 °C, 295 °C in sequence from section 1 to section 10, the head temperature is 300 °C, and the screw speed is 300 rpm;

[0074] The preparation method of the flame retardant is as follows:

[0075] Step A: Under nitrogen protection, mix 12 parts of DOPO, 13.2 parts of 4-maleimidobenzoic acid, and 84 parts of N,N-dimethylformamide evenly, react at 95 °C for 1.5 h, continue to heat up to 130 °C and react for 7 h, cool to room temperature, recrystallize in an ice-water bath for 12 h, and obtain the modified DOPO after vacuum filtration, washing, and drying;

[0076] Step B: Mix 12 parts of modified DOPO, 48 parts of N,N-dimethylformamide, 1.08 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and 0.84 parts of N-hydroxysuccinimide evenly, stir for 50 min at 25 °C, add 18 parts of L-cysteine, continue stirring for 20 h, and obtain the flame retardant after filtration, washing, and drying;

[0077] Compared with Example 2, in Comparative Example 1, the modified carbon fiber is replaced with the same mass of carbon fiber, and the other steps are the same as those in Example 2.

[0078] Comparative Example 2: A preparation process of a high-strength modified plastic product, including the following processes:

[0079] Compared with Example 2, in Comparative Example 2, the flame retardant was replaced with the same mass of DOPO, and the other steps were the same as those in Example 2.

[0080] Comparative Example 3: A preparation process of a high-strength modified plastic product, including the following processes:

[0081] Step S1: 12 parts of modified carbon fiber, 35 parts of flame retardant, 3 parts of photoinitiator, and 80 parts of N,N-dimethylformamide were irradiated with 380 nm ultraviolet light for 50 min at an irradiation intensity of 30 mW / cm2, washed and dried to obtain a composite;

[0082] Step S2: 50 parts of polyphthalamide, 47 parts of the composite, 0.3 parts of polyethylene wax, 0.4 parts of antioxidant, and 0.4 parts of nucleating agent were mixed evenly to obtain a blend; the blend was melt-extruded and granulated in a twin-screw extruder, and injection-molded to obtain a modified plastic product; the barrel temperatures of each section of the twin-screw extruder were 240 °C, 280 °C, 290 °C, 300 °C, 290 °C, 280 °C, 275 °C, 275 °C, 275 °C, and 295 °C in sequence from section 1 to section 10, the head temperature was 300 °C, and the screw speed was 300 rpm;

[0083] Compared with Example 2, the composite in Comparative Example 3 included the following weight components: 12 parts of modified carbon fiber, 35 parts of flame retardant, 3 parts of photoinitiator, and 80 parts of N,N-dimethylformamide, and the other steps were the same as those in Example 2.

[0084] Experiment: The modified plastic products obtained in Examples 1-3 and Comparative Examples 1-3 were taken to prepare specimens, and their properties were detected and the test results were recorded:

[0085] Tensile property test: The test was carried out in accordance with GB / T 1040.2-2006, dumbbell-shaped specimens with a size of 150 m×10 mm×4 mm, and a tensile rate of 10 mm / min; Flexural property test: The test was carried out in accordance with GB / T 9341-2008, specimens with a size of 80 mm×10 mm×4 mm, and a load loading speed of 2 mm / min; UL-94 flame retardancy test: The test was carried out in accordance with GB / T 2408-2008, specimens with a size of 127.0 mm×12.7 mm×3.2 mm.

[0086] The test results are as follows:

[0087]

[0088] According to the data in the above table, the following conclusions can be clearly obtained:

[0089] Compared with Examples 1-3, both the tensile strength and flexural strength of the product obtained in Comparative Example 1 decreased, indicating that the modified carbon fiber prepared by the present invention has better compatibility than carbon fiber, thus effectively improving the mechanical properties of the material.

[0090] Compared with Examples 1-3, the flame retardancy of the product obtained in Comparative Example 2 decreased, which indicates that the flame retardant prepared by the present invention has excellent flame retardancy compared with DOPO and can effectively improve the safety and fire resistance of the material.

[0091] Compared with Examples 1-3, both the tensile strength and flexural strength of the product obtained in Comparative Example 3 decreased, indicating that when the addition amount of the modified carbon fiber is reduced, the mechanical properties of the material will decrease accordingly.

[0092] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to include all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A process for preparing a high-strength modified plastic product, characterized in that: The steps include: Step S1: uniformly mixing the modified carbon fiber, the flame retardant, the photoinitiator and N,N-dimethylformamide, irradiating with ultraviolet light, washing and drying to obtain a composite; Step S2: uniformly mixing polyphthalamide, the composite, polyethylene wax, an antioxidant, and a nucleating agent to obtain a blend; melt-extruding, granulating, and injection-molding the blend in a twin-screw extruder to obtain a modified plastic product; The preparation method of the modified carbon fiber is as follows: Step (1): adjusting the pH of the Tris-HCl buffer to 8.5, adding dopamine hydrochloride and mixing evenly to obtain a dopamine hydrochloride solution; The pretreated carbon fiber is immersed in a dopamine hydrochloride solution for 20-24 hours, taken out, and dried to obtain a polydopamine-coated carbon fiber; Step (2): uniformly mix maleic anhydride and 1,4-dioxane, dropwise add a mixed solution of diethylenetriamine and 1,4-dioxane, and complete the dropwise addition for 1-2 hours, react at room temperature for 2-3 hours, and obtain a prepolymer monomer after vacuum distillation and drying; uniformly mix the prepolymer monomer and deionized water, add ethylenediamine, react at 85-95° C. for 4-5 hours, cool to room temperature, and obtain an amino-terminated hyperbranched polyamide after vacuum distillation and drying; Step (3): placing the polydopamine-coated carbon fiber in an aqueous solution of an amino-terminated hyperbranched polyamide, ultrasonically treating for 1-2 hours, reacting for 3-5 hours, filtering and drying to obtain a modified carbon fiber; The preparation method of the flame retardant is as follows: Step A: Under nitrogen protection, DOPO, 4-maleimidobenzoic acid and N,N-dimethylformamide are mixed evenly, reacted at 90-100°C for 1-2h, and then heated to 125-135°C for 6-8h, cooled to room temperature, and recrystallized in an ice water bath for 12h. After vacuum filtration, washing and drying, modified DOPO is obtained; Step B: The modified DOPO, N,N-dimethylformamide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide are mixed evenly, stirred at 20-30° C. for 30-60 min, L-cysteine ​​is added, and stirring is continued for 12-24 h. After filtering, washing and drying, a flame retardant is obtained.

2. The process for preparing a high-strength modified plastic product according to claim 1, characterized in that: The modified plastic product comprises the following components by weight: 35-65 parts of polyphthalamide, 30-60 parts of a composite, 0.2-0.4 parts of polyethylene wax, 0.2-0.6 parts of an antioxidant, and 0.3-0.5 parts of a nucleating agent.

3. The process for preparing a high-strength modified plastic product according to claim 2, characterized in that: The composite comprises the following components by weight: 20-45 parts of modified carbon fiber, 10-15 parts of flame retardant, 2-4 parts of photoinitiator and 50-100 parts of N,N-dimethylformamide.

4. The process for preparing a high-strength modified plastic product according to claim 1, characterized in that: The preparation method of the pretreated carbon fiber is as follows: The carbon fiber is soaked in acetone for 22-24 hours to remove the sizing agent on the surface, and then cleaned with deionized water and dried to obtain the pretreated carbon fiber.

5. The process for preparing a high-strength modified plastic product according to claim 1, characterized in that: In the step A, the mass ratio of DOPO, 4-maleimidobenzoic acid and N,N-dimethylformamide is 1:(1.0-1.2):(6-8).

6. The process for preparing a high-strength modified plastic product according to claim 1, characterized in that: In the step S2, the barrel temperatures of each section of the twin-screw extruder from section 1 to section 10 are 230-250°C, 270-290°C, 280-300°C, 290-310°C, 280-300°C, 270-290°C, 265-285°C, 265-285°C, 265-285°C, 285-305°C, the head temperature is 290-310°C, and the screw speed is 250-350rpm.

7. A high-strength modified plastic product obtained according to the preparation process according to any one of claims 1 to 6.

Images